src/lib/teaching/physicsLessonSeeds.ts

/**
 * Deterministic Physics lesson-seed system (Phase 6D).
 *
 * Seeds are short, derived, teacher-style content for the 11-step DocDoe class
 * flow. They are authored from the Kerala SSLC Class 10 Physics chapter and
 * always carry a sourceRef back to that chapter. No long textbook paragraphs,
 * no PYQ claims, no "guaranteed question" language. Static — easy to validate
 * and test.
 *
 * Current curated chapters:
 * - Sound Waves (chapterId phy-p1-c1)
 * - Lenses (chapterId phy-p1-c2)
 * - The World of Colours and Vision (chapterId phy-p1-c3)
 * - Electric Energy: Consumption and Conservation (chapterId phy-p2-c5)
 * - Electromagnetic Induction in Daily Life (chapterId phy-p2-c6)
 * - Mechanical Advantage in Action (chapterId phy-p2-c7)
 * - Magnetic Effect of Electric Current (chapterId phy-p1-c4)
 */

import { LENSES_SEEDS } from "./lensesLessonSeeds";
import { COLOURS_VISION_SEEDS } from "./coloursVisionLessonSeeds";
import { ELECTRIC_ENERGY_SEEDS } from "./electricEnergyLessonSeeds";
import { ELECTROMAGNETIC_INDUCTION_SEEDS } from "./electromagneticInductionLessonSeeds";
import { MECHANICAL_ADVANTAGE_SEEDS } from "./mechanicalAdvantageLessonSeeds";
import { MAGNETIC_EFFECT_SEEDS } from "./magneticEffectLessonSeeds";
import { CHEMISTRY_NOMENCLATURE_SEEDS } from "./chemistryNomenclatureSeeds";
// Chemistry seeds are registered only when their chapter title matches the
// canonical SCERT chapter manifest. The former C2-C5 files contain useful
// drafts, but their titles do not match the current textbook mapping and must
// not be presented as lessons under the wrong chapter.
import { CHEMISTRY_P1_C1_SEEDS } from "./chemistryP1C1Seeds";
import { BIOLOGY_P1_C1_SEEDS } from "./biologyP1C1Seeds";
import { BIOLOGY_P1_C2_SEEDS } from "./biologyP1C2Seeds";
import { BIOLOGY_P1_C3_SEEDS } from "./biologyP1C3Seeds";
import { BIOLOGY_P1_C4_SEEDS } from "./biologyP1C4Seeds";
import { BIOLOGY_P1_C5_SEEDS } from "./biologyP1C5Seeds";
import { BIOLOGY_P1_C6_SEEDS } from "./biologyP1C6Seeds";

export type LessonSeedSourceRef = {
  label: string;
  sourceBook: string;
  chapterTitle: string;
  pageRange?: string;
  url?: string | null;
  confidence: "source_backed" | "needs_review";
};

export type ExamAnswerSeed = {
  marks: 1 | 2 | 3 | 4 | 5;
  question: string;
  answerPoints: string[];
  keywords: string[];
  commonMistakes: string[];
  boardStyleRewrite: string;
};

export type CorrectionRubricSeed = {
  maxMarks: number;
  scoringPoints: Array<{
    point: string;
    marks: number;
    requiredKeywords: string[];
    minimumMatches?: number;
  }>;
  commonMissingParts: string[];
  feedbackTemplate: string;
};

export type QuizSeed = {
  id: string;
  type: "mcq" | "short" | "numerical" | "diagram";
  question: string;
  options?: string[];
  answer: string;
  explanation: string;
  difficulty: "easy" | "medium" | "exam";
  tags: string[];
  /**
   * Chapter tests may assess a concept taught in an earlier mission. These
   * fields keep each answer attached to that exact mastery node instead of a
   * vague chapter-level score.
   */
  conceptMissionId?: string;
  conceptLabel?: string;
};

export type VisualBoardSeed = {
  boardTitle: string;
  frames: Array<{
    id: string;
    title: string;
    teacherAction: string;
    boardText: string[];
    diagramDescription?: string;
    imageUrl?: string;
    studentFocus: string;
  }>;
};

export type PhysicsFormulaSeed = {
  formula: string;
  meaning: string;
  symbols: Array<{
    symbol: string;
    meaning: string;
    unit?: string;
  }>;
  commonUseCase: string;
  /** Source-backed warning rendered beside this formula when available. */
  commonMistake?: string;
  numericalPattern?: string;
};

export type LessonSeedContentType =
  | "concept"
  | "diagram"
  | "numerical"
  | "formula"
  | "exam_answer"
  | "revision"
  | "pyq_placeholder";

export type TuitionLessonSeed = {
  missionId: string;
  chapterId: string;
  subject: "Physics" | "Chemistry" | "Biology" | "Maths" | "Mathematics" | "Social Science";
  chapterTitle: string;
  missionTitle: string;
  goal: string;
  /**
   * Day 20 — one-line spoken hook that OPENS the mission (a real question a
   * teacher would ask before any definition). Optional: missions without one
   * fall back to their recall prompt when it is question-shaped.
   */
  hookLine?: string;
  estimatedMinutes: number;
  contentType: LessonSeedContentType;
  tags: string[];
  sourceRefs: LessonSeedSourceRef[];
  sourceStatus: "source_backed" | "needs_review";
  canTeach: boolean;
  pyqEvidenceStatus: "not_curated" | "curated";

  recall: {
    prompt: string;
    expectedPoints: string[];
    misconceptionCheck: string;
  };

  teach: {
    teacherIntro: string;
    explanationBlocks: Array<{
      heading: string;
      explanation: string;
      keyTerms: string[];
    }>;
    analogy?: string;
    malayalamSupport?: string;
    manglishSupport?: string;
  };

  visualBoard: VisualBoardSeed;

  docDoeTrick: {
    title: string;
    trick: string;
    whyItWorks: string;
  };

  keyNotes: string[];

  formulas: PhysicsFormulaSeed[];

  examAnswers: ExamAnswerSeed[];

  yourTurn: {
    prompt: string;
    expectedAnswerPoints: string[];
    hint: string;
  };

  correctionRubric: CorrectionRubricSeed;

  quiz: QuizSeed[];

  recap: {
    summary: string[];
    mustRemember: string[];
  };

  splitScreen?: {
    left: { title: string; imageUrl?: string; caption: string; captionHighlight?: string; };
    right: { title: string; imageUrl?: string; caption: string; captionHighlight?: string; };
  };

  quizTimer?: {
    question: string;
    answer?: string;
    options?: string[];
    countdownSeconds?: number;
  };

  hotspot?: {
    title: string;
    type: "hotspot" | "trap";
    formula?: string;
    values?: string[];
    calculation?: string;
    importantNote: string;
  };

  revisionSave: {
    flashcards: Array<{
      front: string;
      back: string;
      requiredKeywords?: string[];
    }>;
    revisionNotes: string[];
    weakAreaTags: string[];
  };

  qualityFlags: {
    needsHumanReview: boolean;
    reason?: string;
  };
};

// ---------------------------------------------------------------------------
// Source reference (Kerala SSLC Class 10 Physics — Sound Waves, pages 7-26).
// The chapter exists in outputs/sslc-physics-2025/1-sound-waves with extracted
// terms (period, frequency, compressions/rarefactions, wave motion, persistence
// of hearing). All seeds reference this chapter.
// ---------------------------------------------------------------------------
const SOUND_WAVES_SOURCE: LessonSeedSourceRef = {
  label: "Kerala SSLC Physics — Sound Waves (pp. 7-26)",
  sourceBook: "Kerala SCERT Physics, Standard X (2025)",
  chapterTitle: "Sound Waves",
  pageRange: "7-26",
  url: null,
  confidence: "source_backed",
};

const CHAPTER_ID = "phy-p1-c1";
const CHAPTER_TITLE = "Sound Waves";

function physicsSeed(seed: Omit<TuitionLessonSeed, "chapterId" | "subject" | "chapterTitle">): TuitionLessonSeed {
  return { ...seed, chapterId: CHAPTER_ID, subject: "Physics", chapterTitle: CHAPTER_TITLE };
}

// M1 — Nature of Sound Waves

// M1 — Oscillation, Amplitude, Period and Frequency
const M1: TuitionLessonSeed = physicsSeed({
  missionId: "M1",
  missionTitle: "Oscillation, Amplitude, Period and Frequency",
  goal: "Understand the basic terms of oscillatory motion using a pendulum and swing.",
  hookLine: "Why does a playground swing keep coming back to the same point, again and again?",
  estimatedMinutes: 20,
  contentType: "concept",
  tags: ["oscillation", "amplitude", "period", "frequency", "pendulum"],
  sourceRefs: [SOUND_WAVES_SOURCE],
  sourceStatus: "source_backed",
  canTeach: true,
  pyqEvidenceStatus: "not_curated",
  recall: {
    prompt: "Have you noticed how a swing moves back and forth from its resting position?",
    expectedPoints: ["Moves to and fro", "Returns to starting point"],
    misconceptionCheck: "Some think one oscillation is just going forward, but it must return.",
  },
  teach: {
    teacherIntro: "Before we study sound, we need to understand how things vibrate. Imagine a playground swing.",
    explanationBlocks: [
      {
        heading: "Oscillation",
        explanation: "When a swing sits perfectly still, that's its equilibrium position. If you pull it back and let it go—one full trip forward and all the way back is exactly one oscillation.",
        keyTerms: ["oscillation", "equilibrium position", "to and fro"],
      },
      {
        heading: "Amplitude",
        explanation: "How far you pull that swing back before letting it go? That maximum distance from the center is called the amplitude. We measure it in metres (m).",
        keyTerms: ["amplitude", "maximum displacement", "metre"],
      },
      {
        heading: "Period and Frequency",
        explanation: "The total time it takes for that one full swing (forward and back) is the Time Period (T). On the flip side, how many full swings you can squeeze into just one second is the Frequency (f). Because they are exact opposites, T = 1/f.",
        keyTerms: ["time period", "frequency", "hertz"],
      },
    ],
    analogy: "Think of Period as 'Time per swing' and Frequency as 'Swings per time'. They are exact opposites!",
    malayalamSupport: "ഒരു വസ്തു അതിന്റെ സന്തുലിതാവസ്ഥയിൽ നിന്ന് അങ്ങോട്ടും ഇങ്ങോട്ടും ചലിക്കുന്നതാണ് ഓസിലേഷൻ.",
    manglishSupport: "Equilibrium position-il ninnu to and fro move cheyyunnathaanu oscillation.",
  },
  visualBoard: {
    boardTitle: "Oscillatory Motion",
    frames: [
      {
        id: "m1-f1",
        title: "Simple Pendulum",
        teacherAction: "Look at this pendulum moving from O to A, then B, and back to O.",
        boardText: ["O = Equilibrium position", "One oscillation = O → A → B → O"],
        diagramDescription: "Pendulum swinging with O at center, A and B at extremes.",
        imageUrl: "assets/tuition/phy-p1-c1/img_13.png",
        studentFocus: "An oscillation must complete the full path.",
      },
      {
        id: "m1-f2",
        title: "Frequency vs Period",
        teacherAction: "Remember the relation: T and f are reciprocals.",
        boardText: ["Period (T) = time for 1 oscillation", "Frequency (f) = oscillations in 1 sec", "Unit of f = Hertz (Hz)"],
        studentFocus: "Frequency is per second. Period is time in seconds.",
      },
    ],
  },
  docDoeTrick: {
    title: "1-sec vs 1-osc",
    trick: "Time for 1 osc = Period (T). Osc in 1 sec = Frequency (f).",
    whyItWorks: "Contrasting '1 osc' and '1 sec' prevents you from confusing their definitions.",
  },
  keyNotes: [
    "Oscillation is the to-and-fro periodic motion of a body.",
    "Amplitude is maximum displacement from equilibrium (unit: m).",
    "Period (T) is time for one oscillation (unit: s).",
    "Frequency (f) is number of oscillations per second (unit: Hz).",
  ],
  formulas: [
    {
      formula: "f = 1 / T",
      meaning: "Frequency is the reciprocal of the period.",
      symbols: [
        { symbol: "f", meaning: "frequency", unit: "Hz" },
        { symbol: "T", meaning: "period", unit: "s" },
      ],
      commonUseCase: "Convert between frequency and period.",
    },
  ],
  examAnswers: [
    {
      marks: 2,
      question: "If a pendulum takes 1 minute to complete 30 oscillations, find its frequency.",
      answerPoints: ["Time = 60s", "f = 30/60 = 0.5 Hz"],
      keywords: ["60s", "0.5 Hz"],
      commonMistakes: ["Using 1 minute directly instead of seconds"],
      boardStyleRewrite: "Time = 1 min = 60 s. Frequency = Number of oscillations / Time = 30 / 60 = 0.5 Hz.",
    },
  ],
  yourTurn: {
    prompt: "Define amplitude. What is its SI unit? (2 marks)",
    expectedAnswerPoints: ["Maximum displacement from equilibrium position", "Unit is metre"],
    hint: "Think of the maximum distance it moves to one side.",
  },
  correctionRubric: {
    maxMarks: 2,
    scoringPoints: [
      { point: "Mentions maximum displacement", marks: 1, requiredKeywords: ["maximum", "displacement"] },
      { point: "Correct SI unit", marks: 1, requiredKeywords: ["metre", "m"], minimumMatches: 1 },
    ],
    commonMissingParts: ["'Maximum' keyword", "SI unit"],
    feedbackTemplate: "You got {covered}. Remember to include {missing}.",
  },
  quiz: [
    {
      id: "m1-q1",
      type: "mcq",
      question: "The SI unit of frequency is:",
      options: ["metre", "second", "hertz", "m/s"],
      answer: "hertz",
      explanation: "Hertz (Hz) is the unit of frequency.",
      difficulty: "easy",
      tags: ["frequency", "unit"],
    },
  ],
  recap: {
    summary: ["Oscillation is to-and-fro motion", "Amplitude is max displacement", "f = 1/T"],
    mustRemember: ["f is measured in Hz, T in seconds"],
  },
  revisionSave: {
    flashcards: [
      { front: "What is frequency?", back: "Number of oscillations per second (Hz).", requiredKeywords: ["number", "oscillations", "second"] },
      { front: "What is amplitude?", back: "Maximum displacement from equilibrium position." },
    ],
    revisionNotes: ["f = 1/T", "Amplitude determines how far it swings"],
    weakAreaTags: ["oscillation basics"],
  },
  qualityFlags: { needsHumanReview: false },
});

// M2 — Natural Frequency, Forced Vibration & Resonance
const M2: TuitionLessonSeed = physicsSeed({
  missionId: "M2",
  missionTitle: "Natural Frequency, Forced Vibration & Resonance",
  goal: "Understand natural frequency and how forced vibrations lead to resonance.",
  hookLine: "Why are soldiers told to break their marching steps while crossing a bridge?",
  estimatedMinutes: 25,
  contentType: "concept",
  tags: ["natural frequency", "forced vibration", "resonance"],
  sourceRefs: [SOUND_WAVES_SOURCE],
  sourceStatus: "source_backed",
  canTeach: true,
  pyqEvidenceStatus: "not_curated",
  recall: {
    prompt: "Have you ever felt a table vibrate when a mixie is running on it?",
    expectedPoints: ["Table shakes", "Sound becomes louder"],
    misconceptionCheck: "Students might not know the table is forced to vibrate by the mixie.",
  },
  teach: {
    teacherIntro: "Every object in the universe has its own favorite shaking speed. Let's see what happens when we force it to vibrate at a different speed.",
    explanationBlocks: [
      {
        heading: "Natural Frequency",
        explanation: "If you tap a glass, it rings at a specific pitch. That innate, favorite vibration speed is its natural frequency. It depends entirely on the object's length, size, and material.",
        keyTerms: ["natural frequency", "freely vibrates"],
      },
      {
        heading: "Forced Vibration",
        explanation: "If you turn on a heavy mixie on a table, the whole table starts shaking! The table didn't want to shake, but it was forced to by the mixie. This is a forced vibration.",
        keyTerms: ["forced vibration", "induced"],
      },
      {
        heading: "Resonance",
        explanation: "Now, what if the mixie's shaking speed perfectly matches the table's natural favorite speed? The table will shake violently with maximum amplitude! This magical match is called Resonance.",
        keyTerms: ["resonance", "equal frequency", "maximum amplitude"],
      },
    ],
    analogy: "If you push someone on a swing at random times, they barely move (forced vibration). But if you push at exactly their natural swinging rhythm, they go much higher (resonance)!",
    malayalamSupport: "രണ്ട് വസ്തുക്കളുടെ സ്വാഭാവിക ഫ്രീക്വൻസി തുല്യമാകുമ്പോൾ അവ ഉയർന്ന ആംപ്ലിറ്റ്യൂഡിൽ കമ്പനം ചെയ്യുന്നതാണ് റെസൊണൻസ്.",
    manglishSupport: "Randu objects-inte natural frequency equal aakumpol ulla maximum amplitude vibration aanu resonance.",
  },
  visualBoard: {
    boardTitle: "Resonance in Action",
    frames: [
      {
        id: "m2-f1",
        title: "Forced Vibration",
        teacherAction: "When we press a vibrating tuning fork on a table, the table vibrates too.",
        boardText: ["Vibrating object touches table", "Table is forced to vibrate → louder sound"],
        diagramDescription: "Tuning fork pressed against a table.",
        imageUrl: "assets/tuition/phy-p1-c1/img_22.png",
        studentFocus: "The table vibrates because of the external force.",
      },
      {
        id: "m2-f2",
        title: "Resonance Condition",
        teacherAction: "Notice that resonance only happens when the frequencies match perfectly.",
        boardText: ["Forcing Frequency = Natural Frequency", "Result: Maximum Amplitude"],
        studentFocus: "Equal frequency causes resonance.",
      },
    ],
  },
  docDoeTrick: {
    title: "The Matching Rule",
    trick: "Resonance = Matching Frequencies = Max Amplitude.",
    whyItWorks: "In exams, if they ask why something vibrates heavily, the answer is always that their frequencies matched.",
  },
  keyNotes: [
    "Natural frequency depends on length, size, elasticity, and material.",
    "Forced vibration is caused by an external vibrating object.",
    "Resonance occurs when forcing frequency equals natural frequency.",
    "During resonance, the object vibrates with maximum amplitude.",
    "Applications: MRI scanning, radio tuning, musical instruments.",
  ],
  formulas: [],
  examAnswers: [
    {
      marks: 2,
      question: "What is resonance?",
      answerPoints: ["When natural frequency of forcing object equals forced object.", "Vibrates with maximum amplitude."],
      keywords: ["equal", "natural frequency", "maximum amplitude"],
      commonMistakes: ["Forgetting to mention maximum amplitude"],
      boardStyleRewrite: "If the natural frequency of the forcing object and that of the forced object are equal, they are said to be in resonance. They will vibrate with maximum amplitude.",
    },
  ],
  yourTurn: {
    prompt: "Name two factors that influence the natural frequency of an object. (1 mark)",
    expectedAnswerPoints: ["Length", "Size", "Elasticity", "Nature of material"],
    hint: "Think about what changes if you use a smaller or longer tuning fork.",
  },
  correctionRubric: {
    maxMarks: 1,
    scoringPoints: [
      { point: "Mentions any two factors", marks: 1, requiredKeywords: ["length", "size", "elasticity", "material"] },
    ],
    commonMissingParts: ["Listing only one factor"],
    feedbackTemplate: "Good. You listed {covered}.",
  },
  quiz: [
    {
      id: "m2-q1",
      type: "mcq",
      question: "During resonance, the amplitude of vibration is:",
      options: ["minimum", "maximum", "zero", "constant"],
      answer: "maximum",
      explanation: "Resonance causes the objects to vibrate with maximum amplitude.",
      difficulty: "easy",
      tags: ["resonance"],
    },
  ],
  recap: {
    summary: ["Natural frequency is innate to an object", "Forced vibration is induced", "Resonance = matching frequencies & max amplitude"],
    mustRemember: ["Resonance happens when frequencies are equal"],
  },
  revisionSave: {
    flashcards: [
      { front: "What happens during resonance?", back: "Objects vibrate with maximum amplitude because frequencies match." },
    ],
    revisionNotes: ["Pitch depends on frequency", "Loudness depends on amplitude"],
    weakAreaTags: ["pitch", "loudness"],
  },
  splitScreen: {
    left: { title: "Amplitude", imageUrl: "assets/tuition/phy-p1-c1/img_30.png", caption: "Determines the loudness of sound.", captionHighlight: "Higher Amplitude = Louder Sound" },
    right: { title: "Frequency", imageUrl: "assets/tuition/phy-p1-c1/img_34.png", caption: "Determines the pitch (shrillness).", captionHighlight: "Higher Frequency = Shriller Sound" }
  },
  qualityFlags: { needsHumanReview: false },
});

// M3 — Wave Motion & Types of Waves
const M3: TuitionLessonSeed = physicsSeed({
  missionId: "M3",
  missionTitle: "Wave Motion & Types of Waves",
  goal: "Learn how waves transfer energy without transferring particles, and differentiate longitudinal and transverse waves.",
  hookLine: "When you drop a stone in a pond, does the water itself travel to the shore?",
  estimatedMinutes: 30,
  contentType: "concept",
  tags: ["wave motion", "mechanical waves", "electromagnetic", "longitudinal", "transverse"],
  sourceRefs: [SOUND_WAVES_SOURCE],
  sourceStatus: "source_backed",
  canTeach: true,
  pyqEvidenceStatus: "not_curated",
  recall: {
    prompt: "If you stretch a slinky and shake one end, what moves to the other end?",
    expectedPoints: ["The disturbance moves", "The coils stay in place"],
    misconceptionCheck: "People think the material moves forward, but only energy moves.",
  },
  teach: {
    teacherIntro: "Sound travels as a wave. Let's understand what a wave actually is and the different types of waves.",
    explanationBlocks: [
      {
        heading: "Wave Motion",
        explanation: "Think of a 'Mexican wave' in a cricket stadium. The people (particles) just stand up and sit down—they don't run across the stadium! But the wave itself (the energy) travels all the way around. That is wave motion: energy moves, particles just vibrate in place.",
        keyTerms: ["energy", "propagation", "no particle displacement"],
      },
      {
        heading: "Mechanical vs Electromagnetic",
        explanation: "Some waves need a physical material to travel through, like sound needing air or water. These are Mechanical waves. Others, like light or radio waves, can travel through totally empty space! These are Electromagnetic waves.",
        keyTerms: ["mechanical", "electromagnetic", "medium"],
      },
      {
        heading: "No sound in vacuum",
        explanation: "Because sound is a mechanical wave, it cannot travel through a vacuum. In the bell jar experiment, as the air is slowly pumped out, the ringing bell fades to silence even though the hammer is still striking it.",
        keyTerms: ["vacuum", "bell jar", "medium needed"],
      },
      {
        heading: "Longitudinal vs Transverse",
        explanation: "If you push and pull a slinky straight forward and back, that's a Longitudinal wave (like sound). If you shake the slinky up and down like a snake, that's a Transverse wave (like water ripples).",
        keyTerms: ["longitudinal", "transverse", "parallel", "perpendicular"],
      },
    ],
    analogy: "Wave motion is like doing 'the wave' in a stadium. People just stand up and sit down (vibrate), but the 'wave' travels across the stadium (energy transfer).",
    malayalamSupport: "മാധ്യമത്തിലെ കണികകൾ സഞ്ചരിക്കാതെ ഊർജ്ജം മാത്രം പകരുന്നതാണ് തരംഗ ചലനം.",
    manglishSupport: "Particles move cheyyathe energy maathram pass aakunnathaane wave motion.",
  },
  visualBoard: {
    boardTitle: "Types of Waves",
    frames: [
      {
        id: "m3-f1",
        title: "Longitudinal Wave",
        teacherAction: "Look at the slinky. The push is parallel to the wave direction.",
        boardText: ["Vibration is PARALLEL to direction", "Forms Compressions (C) & Rarefactions (R)", "Example: Sound"],
        diagramDescription: "Slinky with dense compressions and sparse rarefactions.",
        imageUrl: "assets/tuition/phy-p1-c1/img_30.png",
        studentFocus: "Parallel = Longitudinal.",
      },
      {
        id: "m3-f2",
        title: "Transverse Wave",
        teacherAction: "Now shake the slinky up and down. The vibration is perpendicular.",
        boardText: ["Vibration is PERPENDICULAR", "Forms Crests & Troughs", "Example: Light, Water ripples"],
        diagramDescription: "Slinky moving up and down in sine-wave shape.",
        imageUrl: "assets/tuition/phy-p1-c1/img_34.png",
        studentFocus: "Perpendicular = Transverse.",
      },
    ],
  },
  docDoeTrick: {
    title: "Para-Long, Perp-Trans",
    trick: "Parallel -> Longitudinal. Perpendicular -> Transverse.",
    whyItWorks: "Just linking the 'P' words with their wave types saves time in MCQs.",
  },
  keyNotes: [
    "Wave motion transfers energy, not particles.",
    "Mechanical waves (Sound) require a medium.",
    "Sound cannot travel through a vacuum (bell jar experiment).",
    "Electromagnetic waves (Light, Radio) do not require a medium.",
    "Longitudinal waves vibrate parallel to the direction of propagation (Compressions & Rarefactions).",
    "Transverse waves vibrate perpendicular to the direction of propagation (Crests & Troughs).",
    "Sound is a longitudinal mechanical wave.",
  ],
  formulas: [],
  examAnswers: [
    {
      marks: 2,
      question: "Distinguish between longitudinal and transverse waves.",
      answerPoints: ["Longitudinal: Particles vibrate parallel to propagation direction. Forms compressions and rarefactions.", "Transverse: Particles vibrate perpendicular to propagation direction. Forms crests and troughs."],
      keywords: ["parallel", "compressions", "perpendicular", "crests"],
      commonMistakes: ["Mixing up parallel and perpendicular"],
      boardStyleRewrite: "In longitudinal waves, particles vibrate parallel to the direction of propagation, forming compressions and rarefactions. In transverse waves, particles vibrate perpendicular to the direction of propagation, forming crests and troughs.",
    },
  ],
  yourTurn: {
    prompt: "Give one example each for a mechanical wave and an electromagnetic wave. (2 marks)",
    expectedAnswerPoints: ["Mechanical: Sound", "Electromagnetic: Light / Radio waves"],
    hint: "Which one needs a medium? Which one doesn't?",
  },
  correctionRubric: {
    maxMarks: 2,
    scoringPoints: [
      { point: "Correct mechanical example", marks: 1, requiredKeywords: ["sound", "seismic", "water"] },
      { point: "Correct electromagnetic example", marks: 1, requiredKeywords: ["light", "radio", "x-ray", "gamma"] },
    ],
    commonMissingParts: ["Matching the wrong wave to the wrong type"],
    feedbackTemplate: "Good job identifying {covered}.",
  },
  quiz: [
    {
      id: "m3-q1",
      type: "mcq",
      question: "Which of these does not require a medium for transmission?",
      options: ["Sound waves", "Seismic waves", "Radio waves", "Ripples on water"],
      answer: "Radio waves",
      explanation: "Radio waves are electromagnetic waves, which do not need a medium.",
      difficulty: "easy",
      tags: ["electromagnetic"],
    },
  ],
  recap: {
    summary: ["Waves transfer energy, not particles", "Longitudinal = parallel (C & R)", "Transverse = perpendicular (Crests & Troughs)"],
    mustRemember: ["Sound is a mechanical longitudinal wave."],
  },
  revisionSave: {
    flashcards: [
      { front: "What is a longitudinal wave?", back: "Particles vibrate parallel to wave direction (Compressions & Rarefactions)." },
      { front: "What is a transverse wave?", back: "Particles vibrate perpendicular to wave direction (Crests & Troughs)." },
    ],
    revisionNotes: ["Longitudinal = parallel (sound)", "Transverse = perpendicular (light)"],
    weakAreaTags: ["longitudinal", "transverse"],
  },
  splitScreen: {
    left: { title: "Longitudinal Wave", imageUrl: "assets/tuition/phy-p1-c1/img_41.png", caption: "Slinky moving back and forth.", captionHighlight: "Compressions and Rarefactions" },
    right: { title: "Transverse Wave", imageUrl: "assets/tuition/phy-p1-c1/img_45.png", caption: "Rope moving up and down.", captionHighlight: "Crests and Troughs" }
  },
  qualityFlags: { needsHumanReview: false },
});

// M4 — Frequency, Wavelength and Wave Speed (v = fλ)
const M4: TuitionLessonSeed = physicsSeed({
  missionId: "M4",
  // Day 20 — title names the actual quantities (a weak student searches
  // "frequency wavelength", not the textbook section heading), which also
  // lets the tuition brain route that weak topic to this mission.
  missionTitle: "Frequency, Wavelength and Wave Speed (v = fλ)",
  goal: "Define wavelength, speed of a wave, and understand the relationship v = fλ.",
  hookLine: "If a sound becomes shriller, what happens to the size of its wave?",
  estimatedMinutes: 30,
  contentType: "formula",
  tags: ["wavelength", "speed", "v=fλ"],
  sourceRefs: [SOUND_WAVES_SOURCE],
  sourceStatus: "source_backed",
  canTeach: true,
  pyqEvidenceStatus: "not_curated",
  recall: {
    prompt: "We already know frequency (f) is oscillations per second. What is wavelength?",
    expectedPoints: ["The length of one wave"],
    misconceptionCheck: "Students might confuse wavelength with amplitude.",
  },
  teach: {
    teacherIntro: "Now let's measure the physical size and speed of a wave, and see how they are connected mathematically.",
    explanationBlocks: [
      {
        heading: "Wavelength (λ)",
        explanation: "Wavelength is just the physical length of one complete wave. It's the distance between one wave peak and the exact same spot on the very next wave. We measure it in metres (m).",
        keyTerms: ["wavelength", "consecutive", "metre"],
      },
      {
        heading: "Speed of wave (v)",
        explanation: "Speed is simply how much distance the wave covers in one single second. Just like a car's speed, we measure it in metres per second (m/s).",
        keyTerms: ["speed", "distance in one second", "m/s"],
      },
      {
        heading: "The relation v = fλ",
        explanation: "If Frequency (f) is how many waves hit you per second, and Wavelength (λ) is the physical size of each wave... then Speed (v) is just (number of waves) × (size of wave)! So, v = fλ.",
        keyTerms: ["v = fλ", "inversely proportional"],
      },
    ],
    analogy: "If frequency is how many steps you take per second, and wavelength is the size of each step, then speed is how much distance you cover per second.",
    malayalamSupport: "v = fλ എന്നതാണ് പ്രധാന ഫോർമുല. വേഗത സ്ഥിരമാണെങ്കിൽ, ഫ്രീക്വൻസി കൂടുമ്പോൾ തരംഗദൈർഘ്യം (wavelength) കുറയും.",
    manglishSupport: "Speed (v) = Frequency (f) × Wavelength (λ). Speed constant aayirunnal, f koodumpol λ kurayum.",
  },
  visualBoard: {
    boardTitle: "Wavelength and Speed",
    frames: [
      {
        id: "m4-f1",
        title: "Wavelength in Longitudinal Waves",
        teacherAction: "Look at the compressions and rarefactions.",
        boardText: ["Wavelength (λ) = Distance between two consecutive compressions (C-C) or rarefactions (R-R)"],
        diagramDescription: "Longitudinal wave showing λ between two compressions.",
        imageUrl: "assets/tuition/phy-p1-c1/img_41.png",
        studentFocus: "λ is the gap between identical points.",
      },
      {
        id: "m4-f2",
        title: "The Formula v = fλ",
        teacherAction: "This is the most important formula in this chapter.",
        boardText: ["Speed (v) = Frequency (f) × Wavelength (λ)", "If v is constant, f ∝ 1/λ"],
        diagramDescription: "v = fλ triangle.",
        imageUrl: "assets/tuition/phy-p1-c1/img_45.png",
        studentFocus: "Speed relates frequency and wavelength.",
      },
    ],
  },
  docDoeTrick: {
    title: "Inverse Rule",
    trick: "High Frequency = Short Wavelength. Low Frequency = Long Wavelength.",
    whyItWorks: "Because speed is constant in a given medium, if f goes up, λ must go down to keep the product the same.",
  },
  keyNotes: [
    "Wavelength (λ) is the distance between consecutive particles in the same phase.",
    "Unit of λ is metre (m).",
    "Speed (v) is distance travelled in one second. Unit is m/s.",
    "Speed = frequency × wavelength (v = fλ).",
    "When speed is constant, frequency is inversely proportional to wavelength.",
  ],
  formulas: [
    {
      formula: "v = f × λ",
      meaning: "Speed equals frequency times wavelength.",
      symbols: [
        { symbol: "v", meaning: "speed", unit: "m/s" },
        { symbol: "f", meaning: "frequency", unit: "Hz" },
        { symbol: "λ", meaning: "wavelength", unit: "m" },
      ],
      commonUseCase: "Calculating wave speed.",
    },
  ],
  examAnswers: [
    {
      marks: 2,
      question: "Define wavelength of a longitudinal wave.",
      answerPoints: ["It is the distance between two consecutive compressions or two consecutive rarefactions."],
      keywords: ["consecutive", "compressions", "rarefactions"],
      commonMistakes: ["Just saying 'length of a wave'"],
      boardStyleRewrite: "The distance between two consecutive compressions or two consecutive rarefactions is considered as the wavelength of a longitudinal wave.",
    },
  ],
  yourTurn: {
    prompt: "If speed is constant, what happens to wavelength when frequency increases? (1 mark)",
    expectedAnswerPoints: ["Wavelength decreases"],
    hint: "They are inversely proportional.",
  },
  correctionRubric: {
    maxMarks: 1,
    scoringPoints: [
      { point: "Mentions it decreases", marks: 1, requiredKeywords: ["decreases", "reduces", "inversely"] },
    ],
    commonMissingParts: ["Not understanding inverse proportionality"],
    feedbackTemplate: "Correct. {covered}.",
  },
  quiz: [
    {
      id: "m4-q1",
      type: "mcq",
      question: "If a wave travels 700 m in 2 s, its speed is:",
      options: ["1400 m/s", "350 m/s", "700 m/s", "2 m/s"],
      answer: "350 m/s",
      explanation: "Speed = Distance / Time = 700 / 2 = 350 m/s.",
      difficulty: "medium",
      tags: ["speed"],
    },
  ],
  recap: {
    summary: ["Wavelength (λ) = distance between consecutive C-C or R-R", "v = fλ", "f is inversely proportional to λ"],
    mustRemember: ["v = fλ is the core formula."],
  },
  revisionSave: {
    flashcards: [
      { front: "What is the relation between speed, frequency, and wavelength?", back: "v = fλ" },
      { front: "Unit of wavelength?", back: "metre (m)" },
    ],
    revisionNotes: ["v = fλ", "f ∝ 1/λ when v is constant"],
    weakAreaTags: ["v=fλ"],
  },
  qualityFlags: { needsHumanReview: false },
});

// M5 — Numericals using v = fλ
const M5: TuitionLessonSeed = physicsSeed({
  missionId: "M5",
  missionTitle: "Numericals using v = fλ",
  goal: "Solve exam-style numericals step-by-step using v = fλ.",
  hookLine: "Can you find the speed of a wave from just two numbers in the question?",
  estimatedMinutes: 25,
  contentType: "numerical",
  tags: ["numerical", "v=fλ", "substitution", "cm to m"],
  sourceRefs: [SOUND_WAVES_SOURCE],
  sourceStatus: "source_backed",
  canTeach: true,
  pyqEvidenceStatus: "not_curated",
  recall: {
    prompt: "What is the formula connecting speed, frequency, and wavelength?",
    expectedPoints: ["v = fλ"],
    misconceptionCheck: "Students substitute wavelength in cm without converting to metres.",
  },
  teach: {
    teacherIntro: "Let's apply our new magic formula v = fλ to solve exam problems! The secret trick? Watch your units.",
    explanationBlocks: [
      {
        heading: "Step 1 — Choose formula",
        explanation: "Always write down the values you are given. If you have speed and frequency, and you want wavelength, just rearrange the triangle: λ = v/f.",
        keyTerms: ["formula"],
      },
      {
        heading: "Step 2 — Unit Conversion",
        explanation: "This is a trap many students fall into! If the wavelength is given in centimeters (cm), you MUST divide by 100 to change it to metres (m) before putting it into the formula.",
        keyTerms: ["cm to m"],
      },
    ],
    analogy: "Think of solving physics problems like baking a cake. Converting cm to m is like pre-heating the oven—you HAVE to do it first, or the whole recipe fails!",
    malayalamSupport: "കണക്ക് ചെയ്യുമ്പോൾ cm നെ m ആക്കാൻ മറക്കരുത് (÷100).",
    manglishSupport: "cm unit-il aanengil adyam m aakuka, divide by 100.",
  },
  visualBoard: {
    boardTitle: "Solving Numericals",
    frames: [
      {
        id: "m5-f1",
        title: "Worked Example",
        teacherAction: "Let's find frequency when v = 350 m/s and λ = 2 m.",
        boardText: ["Given: v = 350 m/s, λ = 2 m", "Formula: f = v / λ", "f = 350 / 2 = 175 Hz"],
        studentFocus: "Write the unit Hz at the end.",
      },
      {
        id: "m5-f2",
        title: "Unit Trap",
        teacherAction: "Watch out for cm!",
        boardText: ["Given: λ = 35 cm", "Convert: λ = 35 / 100 = 0.35 m", "Then substitute into v = fλ"],
        studentFocus: "Never substitute cm directly.",
      },
    ],
  },
  docDoeTrick: {
    title: "F-S-U-A",
    trick: "Formula → Substitute → Unit-check → Answer.",
    whyItWorks: "Four fixed steps prevent silly mistakes and secure method marks.",
  },
  keyNotes: [
    "Use v = fλ.",
    "Convert cm to m before substituting (÷100).",
    "Speed in m/s, frequency in Hz, wavelength in m.",
  ],
  formulas: [
    {
      formula: "v = f × λ",
      meaning: "Speed equals frequency times wavelength.",
      symbols: [
        { symbol: "v", meaning: "speed", unit: "m/s" },
        { symbol: "f", meaning: "frequency", unit: "Hz" },
        { symbol: "λ", meaning: "wavelength", unit: "m" },
      ],
      commonUseCase: "Speed from frequency and wavelength.",
    },
  ],
  examAnswers: [
    {
      marks: 3,
      question: "A wave has a frequency of 2 kHz and a wavelength of 35 cm. How far does this wave travel in 0.5 s?",
      answerPoints: ["f = 2000 Hz, λ = 0.35 m", "v = fλ = 2000 × 0.35 = 700 m/s", "Distance = v × t = 700 × 0.5 = 350 m"],
      keywords: ["2000 Hz", "0.35 m", "700 m/s", "350 m"],
      commonMistakes: ["Not converting kHz to Hz", "Not converting cm to m"],
      boardStyleRewrite: "Given f = 2 kHz = 2000 Hz. Wavelength λ = 35 cm = 0.35 m. Speed v = fλ = 2000 × 0.35 = 700 m/s. Distance travelled in 0.5 s = v × t = 700 × 0.5 = 350 m.",
    },
    {
      marks: 2,
      // Day 20 fix — this chapter uses v = 350 m/s for speed of sound in air
      // everywhere else (M2 quiz, M6 echo problems, M8); this problem had
      // drifted to 340 m/s, a real inconsistency a topper-level review
      // caught (a student could enter the exam with the wrong constant).
      question: "The speed of sound in air is 350 m/s. Find the wavelength of a sound wave whose frequency is 175 Hz.",
      answerPoints: ["Given: v = 350 m/s, f = 175 Hz", "λ = v / f = 350 / 175", "λ = 2 m"],
      keywords: ["λ = v/f", "2 m"],
      commonMistakes: ["Multiplying v × f instead of rearranging to λ = v/f"],
      boardStyleRewrite: "Given v = 350 m/s and f = 175 Hz. Wavelength λ = v/f = 350/175 = 2 m.",
    },
    {
      marks: 3,
      question: "A wave completes 250 oscillations in 5 seconds. If its wavelength is 1.2 m, find its frequency and speed.",
      answerPoints: [
        "Given: 250 oscillations in 5 s, λ = 1.2 m",
        "Frequency f = number of oscillations / time = 250 / 5 = 50 Hz",
        "v = fλ = 50 × 1.2 = 60 m/s",
      ],
      keywords: ["50 Hz", "v = fλ", "60 m/s"],
      commonMistakes: ["Taking 250 itself as the frequency without dividing by the 5 seconds"],
      boardStyleRewrite: "Given 250 oscillations in 5 s and λ = 1.2 m. Frequency f = 250/5 = 50 Hz. Speed v = fλ = 50 × 1.2 = 60 m/s.",
    },
  ],
  yourTurn: {
    prompt: "Speed of sound = 350 m/s. Frequency = 35 Hz. Find the distance between two consecutive compressions. (2 marks)",
    expectedAnswerPoints: ["λ = v/f", "λ = 350 / 35", "λ = 10 m"],
    hint: "Distance between consecutive compressions is just the wavelength.",
  },
  correctionRubric: {
    maxMarks: 2,
    scoringPoints: [
      { point: "Recognizes it's asking for wavelength", marks: 1, requiredKeywords: ["wavelength", "v/f"] },
      { point: "Calculates correct answer with unit", marks: 1, requiredKeywords: ["10", "m"] },
    ],
    commonMissingParts: ["Unit on the answer"],
    feedbackTemplate: "Good. You got {covered}.",
  },
  quiz: [
    {
      id: "m5-q1",
      type: "numerical",
      question: "If v = 20 m/s and distance between two adjacent troughs is 2 m, find frequency.",
      answer: "f = v/λ = 20 / 2 = 10 Hz",
      explanation: "Distance between troughs is wavelength (λ=2m). f=v/λ.",
      difficulty: "medium",
      tags: ["numerical"],
    },
  ],
  recap: {
    summary: ["Convert kHz to Hz", "Convert cm to m", "Use v = fλ"],
    mustRemember: ["Always check units before substituting."],
  },
  revisionSave: {
    flashcards: [
      { front: "Convert 2 kHz to Hz", back: "2000 Hz" },
      { front: "Convert 35 cm to m", back: "0.35 m" },
    ],
    revisionNotes: ["Distance between adjacent compressions or crests = Wavelength"],
    weakAreaTags: ["numericals"],
  },
  qualityFlags: { needsHumanReview: false },
});

// M6 — Reflection, Echo & Reverberation
const M6: TuitionLessonSeed = physicsSeed({
  missionId: "M6",
  missionTitle: "Reflection, Echo & Reverberation",
  goal: "Understand how sound reflects, the conditions for an echo, and reverberation.",
  hookLine: "Why do you hear your own voice come back to you in an empty hall?",
  estimatedMinutes: 30,
  contentType: "concept",
  tags: ["reflection", "echo", "persistence of hearing", "reverberation"],
  sourceRefs: [SOUND_WAVES_SOURCE],
  sourceStatus: "source_backed",
  canTeach: true,
  pyqEvidenceStatus: "not_curated",
  recall: {
    prompt: "Why don’t we hear an echo inside a small room?",
    expectedPoints: ["Walls are too close", "Sound comes back too fast"],
    misconceptionCheck: "Students think reflection doesn't happen in a small room. It does, but we can't distinguish it.",
  },
  teach: {
    teacherIntro: "Just like a rubber ball bounces off a wall, sound waves bounce off surfaces. Let's see what happens when sound bounces back to us.",
    explanationBlocks: [
      {
        heading: "Reflection of Sound",
        explanation: "When sound hits a hard, smooth surface (like a concrete wall), it bounces back perfectly. This is reflection. Rough surfaces (like carpets) tend to absorb sound instead.",
        keyTerms: ["reflection", "smooth surfaces"],
      },
      {
        heading: "Echo and Persistence of Hearing",
        explanation: "If you shout, your brain remembers that sound for exactly 0.1 seconds. If the bounced sound comes back AFTER that 0.1s gap, you hear it clearly as a second, separate sound. This is an Echo!",
        keyTerms: ["echo", "persistence of hearing", "0.1 second"],
      },
      {
        heading: "Reverberation",
        explanation: "But what if you are in a small empty room? The sound bounces back too fast and from many different walls at once! They all blend together into a long, messy 'boom' that lingers. That is Reverberation.",
        keyTerms: ["reverberation", "multiple reflections", "lingering"],
      },
    ],
    analogy: "An Echo is like catching a single tennis ball thrown against a wall. Reverberation is like having 100 ping pong balls bouncing around a small room all at once!",
    malayalamSupport: "പ്രതിധ്വനി (echo) കേൾക്കാൻ ശബ്ദം പ്രതിഫലിച്ച് കുറഞ്ഞത് 0.1 സെക്കൻഡ് കഴിഞ്ഞ് തിരിച്ചെത്തണം. ഒന്നിലധികം തവണ പ്രതിഫലിച്ച് ശബ്ദം നീണ്ടുനിൽക്കുന്നതാണ് reverberation.",
    manglishSupport: "Reflect cheytha sound 0.1s kazhinju ethumbol echo kelkkum. Multiple reflection kaaranam sound linger cheyyunnathaanu reverberation.",
  },
  visualBoard: {
    boardTitle: "Echo vs Reverberation",
    frames: [
      {
        id: "m6-f1",
        title: "Echo Condition",
        teacherAction: "Here is the calculation for the minimum distance for an echo.",
        boardText: ["Time required = 0.1 s", "Speed of sound ≈ 350 m/s", "Distance = speed × time = 35 m", "Reflecting surface must be at least 17.5 m away"],
        imageUrl: "assets/tuition/phy-p1-c1/img_54.png",
        studentFocus: "The 17.5 m minimum distance rule.",
      },
      {
        id: "m6-f2",
        title: "Reverberation",
        teacherAction: "Look at the multiple reflection paths inside an empty hall.",
        boardText: ["Multiple reflections", "Lingering of sound = Reverberation", "Walls made rough to reduce it"],
        imageUrl: "assets/tuition/phy-p1-c1/img_51.png",
        studentFocus: "Rough walls reduce reverberation.",
      },
    ],
  },
  docDoeTrick: {
    title: "17.5 m Rule",
    trick: "Distance traveled = 35m (in 0.1s). So wall distance = 35 / 2 = 17.5m.",
    whyItWorks: "Always halve the total distance to find the distance to the wall.",
  },
  keyNotes: [
    "Smooth, hard surfaces reflect sound waves very well.",
    "Persistence of hearing is 0.1 s.",
    "Echo is heard when reflected sound arrives after 0.1 s.",
    "Minimum distance for echo in air (v=350m/s) is 17.5 m.",
    "Reverberation is the lingering of sound due to multiple reflections.",
    "Walls of cinema theatres are made rough to absorb sound and reduce reverberation.",
  ],
  formulas: [
    {
      formula: "2d = v × t",
      meaning: "Total distance traveled by sound to reflecting surface and back.",
      symbols: [
        { symbol: "d", meaning: "distance to surface", unit: "m" },
        { symbol: "v", meaning: "speed", unit: "m/s" },
        { symbol: "t", meaning: "time", unit: "s" },
      ],
      commonUseCase: "Calculating distance to reflecting surface.",
    },
  ],
  examAnswers: [
    {
      marks: 3,
      question: "Why are the walls of large halls like cinema theatres made rough?",
      answerPoints: ["To prevent reverberation.", "Rough surfaces absorb sound better and reflect less.", "This prevents the lingering of sound."],
      keywords: ["reverberation", "absorb", "lingering"],
      commonMistakes: ["Confusing echo and reverberation"],
      boardStyleRewrite: "Walls of cinema theatres are made rough to reduce multiple reflections of sound. Rough surfaces absorb sound waves, thereby reducing reverberation (lingering of sound).",
    },
  ],
  yourTurn: {
    prompt: "The echo of a firecracker is heard after 1 s. Speed of sound is 350 m/s. Find the distance to the reflecting surface. (2 marks)",
    expectedAnswerPoints: ["Total distance = v × t = 350 × 1 = 350 m", "Distance to surface = 350 / 2 = 175 m"],
    hint: "The sound travels there and back. So divide the total distance by 2.",
  },
  correctionRubric: {
    maxMarks: 2,
    scoringPoints: [
      { point: "Calculates total distance 350m", marks: 1, requiredKeywords: ["350"] },
      { point: "Divides by 2 to get 175m", marks: 1, requiredKeywords: ["175", "m"] },
    ],
    commonMissingParts: ["Forgetting to divide by 2"],
    feedbackTemplate: "Good. {covered}.",
  },
  quiz: [
    {
      id: "m6-q1",
      type: "mcq",
      question: "The lingering of sound due to multiple reflection is called:",
      options: ["Echo", "Reverberation", "Refraction", "Resonance"],
      answer: "Reverberation",
      explanation: "Multiple reflection causes the sound to linger, which is reverberation.",
      difficulty: "easy",
      tags: ["reverberation"],
    },
  ],
  recap: {
    summary: ["Persistence of hearing = 0.1s", "Echo needs minimum 17.5m distance", "Reverberation is lingering sound"],
    mustRemember: ["Divide distance by 2 for echo problems."],
  },
  revisionSave: {
    flashcards: [
      { front: "What is persistence of hearing?", back: "The auditory experience persists for 1/10 of a second." },
      { front: "What is reverberation?", back: "Lingering of sound due to multiple reflections." },
    ],
    revisionNotes: ["Echo requires 0.1s gap", "Rough surfaces reduce reverberation"],
    weakAreaTags: ["echo", "reverberation"],
  },
  hotspot: {
    title: "Echo Calculation",
    type: "hotspot",
    formula: "v = 2d / t",
    values: ["v = velocity of sound", "d = distance to obstacle", "t = total time taken"],
    calculation: "d = (v × t) / 2",
    importantNote: "Total distance is 2d because sound travels to the obstacle AND back!"
  },
  qualityFlags: { needsHumanReview: false },
});

// M7 — Limits of Audibility & Ultrasonic Uses
const M7: TuitionLessonSeed = physicsSeed({
  missionId: "M7",
  missionTitle: "Limits of Audibility & Ultrasonic Uses",
  goal: "Understand audible range, infrasonic and ultrasonic sounds, and their applications.",
  hookLine: "Why can a dog hear a whistle that you cannot hear at all?",
  estimatedMinutes: 20,
  contentType: "concept",
  tags: ["audibility", "infrasonic", "ultrasonic", "SONAR"],
  sourceRefs: [SOUND_WAVES_SOURCE],
  sourceStatus: "source_backed",
  canTeach: true,
  pyqEvidenceStatus: "not_curated",
  recall: {
    prompt: "Can a person with normal hearing hear all sounds?",
    expectedPoints: ["No", "Only a certain range"],
    misconceptionCheck: "Some think we can hear everything, but dogs and bats can hear higher frequencies than us.",
  },
  teach: {
    teacherIntro: "Did you know there are thousands of sounds in the room right now that you literally cannot hear? Human ears are only built to tune into a specific range of sounds.",
    explanationBlocks: [
      {
        heading: "Limits of Audibility",
        explanation: "For a person with normal hearing, we can only hear sounds between 20 Hz and 20,000 Hz. That is our 'Audible Range'.",
        keyTerms: ["20 Hz", "20000 Hz", "audible"],
      },
      {
        heading: "Infrasonic and Ultrasonic",
        explanation: "Anything vibrating slower than 20 Hz is Infrasonic (like massive earthquake waves, or elephants whispering). Anything faster than 20,000 Hz is Ultrasonic (like dogs or bats communicating). We can't hear either of them!",
        keyTerms: ["infrasonic", "ultrasonic"],
      },
      {
        heading: "Uses of Ultrasonic Waves",
        explanation: "Because Ultrasonic waves vibrate so incredibly fast, they pack a lot of energy. We use them in medicine to safely take images of babies (ultrasound), crush kidney stones, and in submarines (SONAR) to map the ocean floor.",
        keyTerms: ["ultrasonography", "SONAR", "cleaning"],
      },
    ],
    analogy: "Think of your ears like a radio that only tunes into certain stations. The Infrasonic and Ultrasonic stations are still playing, but your ears just can't tune into them!",
    malayalamSupport: "20 Hz നും 20000 Hz നും ഇടയിലുള്ള ശബ്ദം മാത്രമേ മനുഷ്യന് കേൾക്കാനാകൂ. അതിനു മുകളിലുള്ളത് ultrasonic ഉം താഴെയുള്ളത് infrasonic ഉം ആണ്.",
    manglishSupport: "20 Hz to 20 kHz aanu audible range. 20000 Hz mukalil ultrasonic, 20 Hz thaazhe infrasonic.",
  },
  visualBoard: {
    boardTitle: "Sound Frequencies",
    frames: [
      {
        id: "m7-f1",
        title: "Audible Range",
        teacherAction: "Look at the spectrum. Humans are limited to the middle band.",
        boardText: ["< 20 Hz : Infrasonic (Elephants, seismic)", "20 Hz - 20000 Hz : Audible to humans", "> 20000 Hz : Ultrasonic (Bats, Dogs)"],
        imageUrl: "assets/tuition/phy-p1-c1/img_57.png",
        studentFocus: "Memorize the 20 to 20,000 Hz limit.",
      },
      {
        id: "m7-f2",
        title: "SONAR",
        teacherAction: "SONAR uses ultrasonic waves to find distance to the sea bottom.",
        boardText: ["SONAR", "Emits ultrasonic waves", "Calculates depth using reflection"],
        diagramDescription: "Ship sending waves to sea bottom and receiving reflection.",
        imageUrl: "assets/tuition/phy-p1-c1/img_60.png",
        studentFocus: "SONAR uses reflection of ultrasonic waves.",
      },
    ],
  },
  docDoeTrick: {
    title: "Ultra means Above",
    trick: "Ultra = Above 20k. Infra = Below 20.",
    whyItWorks: "Simple prefix association helps remember which is which.",
  },
  keyNotes: [
    "Audible range for humans: 20 Hz to 20000 Hz.",
    "Infrasonic: Below 20 Hz.",
    "Ultrasonic: Above 20000 Hz.",
    "Ultrasonic uses: Ultrasonography, crushing kidney stones, SONAR, cleaning irregular parts.",
  ],
  formulas: [],
  examAnswers: [
    {
      marks: 2,
      question: "Write two uses of ultrasonic waves in the medical field.",
      answerPoints: ["To crush small stones in the kidneys.", "In ultrasonography to take images of internal organs."],
      keywords: ["kidney stones", "ultrasonography"],
      commonMistakes: ["Writing SONAR (which is not medical)"],
      boardStyleRewrite: "Ultrasonic waves are used in the medical field to crush small stones in the kidneys and for ultrasonography (to take images of internal organs).",
    },
  ],
  yourTurn: {
    prompt: "What is the frequency of sound that a bat produces to catch prey? Is it infrasonic or ultrasonic? (2 marks)",
    expectedAnswerPoints: ["Above 20000 Hz", "Ultrasonic"],
    hint: "Bats use very high frequency sound.",
  },
  correctionRubric: {
    maxMarks: 2,
    scoringPoints: [
      { point: "Mentions above 20000 Hz", marks: 1, requiredKeywords: ["20000", "above"] },
      { point: "Identifies as ultrasonic", marks: 1, requiredKeywords: ["ultrasonic"] },
    ],
    commonMissingParts: ["Mentioning the exact frequency range"],
    feedbackTemplate: "Correct. {covered}.",
  },
  quiz: [
    {
      id: "m7-q1",
      type: "mcq",
      question: "Which of the following frequency can be heard by humans?",
      options: ["5 Hz", "2000 Hz", "200 kHz", "50 kHz"],
      answer: "2000 Hz",
      explanation: "2000 Hz falls within the 20 Hz to 20,000 Hz audible range.",
      difficulty: "easy",
      tags: ["audibility"],
    },
  ],
  recap: {
    summary: ["Audible range: 20 Hz to 20 kHz", "Infra < 20 Hz, Ultra > 20 kHz", "Ultrasonic used in SONAR and medicine"],
    mustRemember: ["SONAR uses ultrasonic waves."],
  },
  revisionSave: {
    flashcards: [
      { front: "What is the audible range for humans?", back: "20 Hz to 20,000 Hz." },
      { front: "What type of wave is used in SONAR?", back: "Ultrasonic waves." },
    ],
    revisionNotes: ["Infra = below 20 Hz", "Ultra = above 20 kHz"],
    weakAreaTags: ["ultrasonic"],
  },
  hotspot: {
    title: "Unit Trap Warning!",
    type: "trap",
    importantNote: "Always convert kHz to Hz before calculating! Example: 2 kHz = 2000 Hz."
  },
  quizTimer: {
    question: "What is the audible range of frequency for humans?",
    options: ["20 Hz to 20,000 Hz", "2 Hz to 2000 Hz", "200 Hz to 20 kHz", "20 kHz to 200 kHz"],
    answer: "20 Hz to 20,000 Hz",
    countdownSeconds: 1.5
  },
  qualityFlags: { needsHumanReview: false },
});

// M8 — Seismic Waves and Tsunami
const M8: TuitionLessonSeed = physicsSeed({
  missionId: "M8",
  missionTitle: "Seismic Waves and Tsunami",
  goal: "Understand the destructive power of seismic waves and tsunamis.",
  hookLine: "How can a wave under the ground shake an entire city?",
  estimatedMinutes: 10,
  contentType: "concept",
  tags: ["seismic waves", "earthquake", "tsunami"],
  sourceRefs: [SOUND_WAVES_SOURCE],
  sourceStatus: "source_backed",
  canTeach: true,
  pyqEvidenceStatus: "not_curated",
  recall: {
    prompt: "Can waves travelling under the ground cause real harm?",
    expectedPoints: ["Yes, high intensity waves can cause disaster", "Like earthquakes or tsunamis"],
    misconceptionCheck: "Waves are not just sound or light, they can carry massive destructive energy.",
  },
  teach: {
    teacherIntro: "We end the chapter by looking at the most powerful, terrifying, and destructive mechanical waves on Planet Earth.",
    explanationBlocks: [
      {
        heading: "Seismic Waves",
        explanation: "When massive tectonic plates under the ground snap or volcanic explosions happen, they release unimaginable energy. This energy travels through the solid Earth crust as Seismic Waves—what we call an Earthquake.",
        keyTerms: ["seismic waves", "earthquake", "seismology"],
      },
      {
        heading: "Tsunami",
        explanation: "If one of these massive earthquakes happens at the bottom of the ocean, it acts like a giant paddle. It displaces millions of tons of water upward, creating a devastatingly fast ocean wave called a Tsunami.",
        keyTerms: ["tsunami", "ocean waves", "displacement of water"],
      },
    ],
    analogy: "A tsunami is NOT just a tall wave on the surface. It is the entire depth of the ocean—from the sea floor to the surface—being violently shoved forward by the earthquake.",
    malayalamSupport: "ഭൂകമ്പം ഉണ്ടാകുമ്പോൾ ഉണ്ടാകുന്ന തരംഗങ്ങളാണ് seismic waves. സമുദ്രത്തിനടിയിൽ ഭൂകമ്പം ഉണ്ടാകുമ്പോഴാണ് സുനാമി ഉണ്ടാകുന്നത്.",
    manglishSupport: "Earthquake kaaranam undaakunna waves aanu seismic waves. Ocean bottom-il earthquake undaakumpol Tsunami varum.",
  },
  visualBoard: {
    boardTitle: "Destructive Waves",
    frames: [
      {
        id: "m8-f1",
        title: "Seismic Waves & Tsunami",
        teacherAction: "The intensity of an earthquake is measured by the Richter scale.",
        boardText: ["Seismic waves = Earthquake waves", "Measured on Richter scale", "Tsunami = Gigantic ocean waves due to underwater earthquake"],
        studentFocus: "Earthquakes at ocean bottom trigger tsunamis.",
      },
    ],
  },
  docDoeTrick: {
    title: "Seismo = Earth",
    trick: "Seismic relates to the Earth's crust vibrating.",
    whyItWorks: "Helps connect seismology directly to earthquakes.",
  },
  keyNotes: [
    "Seismic waves are caused by earthquakes or massive explosions in the Earth's crust.",
    "Intensity of earthquakes is determined by the Richter scale.",
    "Tsunami is a series of gigantic ocean waves triggered by underwater earthquakes.",
  ],
  formulas: [],
  examAnswers: [
    {
      marks: 1,
      question: "Which scale is used to determine the intensity of earthquakes?",
      answerPoints: ["Richter scale"],
      keywords: ["Richter"],
      commonMistakes: ["Writing seismograph (which is the instrument, not the scale)"],
      boardStyleRewrite: "The intensity of earthquakes is determined by the Richter scale.",
    },
  ],
  yourTurn: {
    prompt: "What causes a tsunami? (1 mark)",
    expectedAnswerPoints: ["Earthquakes at the bottom of oceans", "Displacement of large volumes of water"],
    hint: "Think about what happens under the ocean.",
  },
  correctionRubric: {
    maxMarks: 1,
    scoringPoints: [
      { point: "Mentions underwater earthquakes", marks: 1, requiredKeywords: ["earthquake", "ocean", "bottom"] },
    ],
    commonMissingParts: ["Not specifying it happens underwater"],
    feedbackTemplate: "Correct. {covered}.",
  },
  quiz: [
    {
      id: "m8-q1",
      type: "mcq",
      question: "The study of seismic waves is called:",
      options: ["Astrology", "Seismology", "Cosmology", "Oceanography"],
      answer: "Seismology",
      explanation: "Seismology is the study of earthquakes and seismic waves.",
      difficulty: "easy",
      tags: ["seismic"],
    },
  ],
  recap: {
    summary: ["Seismic waves = earthquake waves", "Tsunami = gigantic ocean waves from underwater earthquakes"],
    mustRemember: ["Richter scale measures earthquake intensity."],
  },
  revisionSave: {
    flashcards: [
      { front: "What is a tsunami?", back: "Gigantic ocean waves caused by underwater earthquakes." },
    ],
    revisionNotes: ["Richter scale = intensity of earthquakes"],
    weakAreaTags: ["seismic"],
  },
  qualityFlags: { needsHumanReview: false },
});

// M9 — full-chapter revision and final assessment. Each quiz item points back
// to the mission it actually assesses, so one wrong answer repairs that exact
// concept instead of creating a vague chapter-level weakness.
const M9: TuitionLessonSeed = physicsSeed({
  missionId: "M9",
  missionTitle: "Sound Waves Chapter Test & Revision",
  goal: "Revise the full chapter, complete a concept-linked final test, and turn every mistake into the next revision task.",
  hookLine: "Can you connect every Sound Waves idea without opening the textbook?",
  estimatedMinutes: 40,
  contentType: "revision",
  tags: ["chapter test", "revision", "oscillation", "resonance", "wave speed", "echo", "audibility", "seismic waves"],
  sourceRefs: [SOUND_WAVES_SOURCE],
  sourceStatus: "source_backed",
  canTeach: true,
  pyqEvidenceStatus: "not_curated",
  recall: {
    prompt: "From memory, write the wave equation and name two chapter ideas that do not use it.",
    expectedPoints: ["v = fλ", "Examples include resonance, echo, audibility, seismic waves or tsunami"],
    misconceptionCheck: "The chapter is more than one formula: the test also checks definitions, applications and common traps.",
  },
  teach: {
    teacherIntro: "This is your chapter finish line. First rebuild the full map; then every test answer updates the exact concept it checks.",
    explanationBlocks: [
      {
        heading: "Motion and vibration",
        explanation: "Oscillation gives amplitude, period and frequency. Natural frequency and forced vibration explain resonance.",
        keyTerms: ["oscillation", "period", "frequency", "resonance"],
      },
      {
        heading: "Wave motion and calculations",
        explanation: "Mechanical waves transfer energy without carrying particles forward. For calculations use v = fλ and SI units.",
        keyTerms: ["energy transfer", "longitudinal", "transverse", "v = fλ"],
      },
      {
        heading: "Reflection, hearing and destructive waves",
        explanation: "Reflection explains echo and reverberation. Hearing has limits, ultrasonic sound has applications, and seismic waves can produce tsunamis.",
        keyTerms: ["echo", "reverberation", "20 Hz to 20 kHz", "ultrasonic", "seismic"],
      },
    ],
    analogy: "Treat the chapter like one route map: vibration starts the journey, waves carry energy, formulas measure them, and applications show what they do.",
    malayalamSupport: "അധ്യായ മാപ്പ്: ദോലനം → തരംഗചലനം → v = fλ → പ്രതിധ്വനി → ശ്രവണപരിധി → ഭൂകമ്പ തരംഗങ്ങൾ. ഓരോ തെറ്റും അതത് ആശയത്തിന്റെ റിവിഷൻ ടാസ്ക് ആവും.",
    manglishSupport: "Full map: oscillation → wave motion → v = fλ → echo → hearing range → seismic waves. Oro mistake-um exact revision task aavum.",
  },
  visualBoard: {
    boardTitle: "Sound Waves — one-board chapter map",
    frames: [
      {
        id: "m9-f1",
        title: "The complete chapter path",
        teacherAction: "Connect oscillation to wave applications, with v = fλ and the echo relation in the centre.",
        boardText: [
          "Oscillation → natural frequency → resonance",
          "Wave motion → longitudinal/transverse → v = fλ",
          "Reflection → echo | Hearing → infra/ultra | Earth → seismic/tsunami",
        ],
        studentFocus: "Definition, formula, condition and application must stay connected.",
      },
    ],
  },
  docDoeTrick: {
    title: "D-F-C-A check",
    trick: "For every answer check Definition, Formula, Condition and Application.",
    whyItWorks: "It catches the most common chapter-test omissions before you submit.",
  },
  keyNotes: [
    "Frequency f = 1/T and wave speed v = fλ; use seconds, hertz and metres.",
    "A mechanical wave transfers energy, not matter; particles vibrate parallel or perpendicular to wave travel.",
    "Resonance occurs when forcing frequency matches natural frequency and amplitude becomes maximum.",
    "For an echo, sound travels to the reflector and back, so distance to the reflector is vt/2.",
    "Human audible range is about 20 Hz to 20 kHz; ultrasonic sound is above 20 kHz.",
    "An underwater earthquake can displace a large volume of water and produce a tsunami.",
  ],
  formulas: [
    {
      formula: "f = 1 / T",
      meaning: "Frequency is the reciprocal of time period.",
      symbols: [
        { symbol: "f", meaning: "frequency", unit: "Hz" },
        { symbol: "T", meaning: "time period", unit: "s" },
      ],
      commonUseCase: "Converting between time period and frequency.",
    },
    {
      formula: "v = fλ",
      meaning: "Wave speed equals frequency multiplied by wavelength.",
      symbols: [
        { symbol: "v", meaning: "wave speed", unit: "m/s" },
        { symbol: "f", meaning: "frequency", unit: "Hz" },
        { symbol: "λ", meaning: "wavelength", unit: "m" },
      ],
      commonUseCase: "Finding wave speed, frequency or wavelength.",
    },
    {
      formula: "d = vt / 2",
      meaning: "Echo distance is half the total distance travelled by sound.",
      symbols: [
        { symbol: "d", meaning: "distance to reflector", unit: "m" },
        { symbol: "v", meaning: "speed of sound", unit: "m/s" },
        { symbol: "t", meaning: "echo time", unit: "s" },
      ],
      commonUseCase: "Finding reflector distance from echo time.",
    },
  ],
  examAnswers: [
    {
      marks: 4,
      question: "Write the key relations and conditions you would revise before a Sound Waves chapter test.",
      answerPoints: [
        "f = 1/T and v = fλ with SI units",
        "Resonance needs forcing frequency equal to natural frequency",
        "Echo distance uses d = vt/2 because sound travels to the reflector and back",
        "Human audible range is 20 Hz to 20 kHz",
      ],
      keywords: ["f = 1/T", "v = fλ", "natural frequency", "vt/2", "20 Hz", "20 kHz"],
      commonMistakes: ["Forgetting the factor 2 in echo distance", "Using centimetres without converting to metres", "Swapping infrasonic and ultrasonic ranges"],
      boardStyleRewrite: "Use f = 1/T and v = fλ in SI units. Resonance occurs at matching frequencies. Echo distance is vt/2. Humans hear about 20 Hz to 20 kHz.",
    },
  ],
  yourTurn: {
    prompt: "Build a four-line last-minute card using one definition, one formula, one condition and one application.",
    expectedAnswerPoints: ["A correct wave definition", "v = fλ or f = 1/T", "A resonance or echo condition", "An ultrasonic or seismic application"],
    hint: "Use the D-F-C-A check shown above.",
  },
  correctionRubric: {
    maxMarks: 4,
    scoringPoints: [
      { point: "Correct definition", marks: 1, requiredKeywords: ["wave", "energy"] },
      { point: "Correct formula", marks: 1, requiredKeywords: ["v", "f", "λ"] },
      { point: "Correct condition", marks: 1, requiredKeywords: ["frequency", "echo"] },
      { point: "Correct application", marks: 1, requiredKeywords: ["ultrasonic", "tsunami"] },
    ],
    commonMissingParts: ["A formula with units", "A clear condition", "A real application"],
    feedbackTemplate: "Your revision card covers {covered}. Add {missing} before the test.",
  },
  quiz: [
    {
      id: "m9-q1", type: "numerical",
      question: "An oscillator makes 5 oscillations each second. What is its time period?",
      answer: "0.2 s", explanation: "T = 1/f = 1/5 = 0.2 s.", difficulty: "medium", tags: ["period", "frequency"],
      conceptMissionId: "M1", conceptLabel: "Oscillation, Amplitude, Period and Frequency",
    },
    {
      id: "m9-q2", type: "short", question: "State the condition for resonance.",
      answer: "Resonance occurs when the forcing frequency equals the natural frequency.",
      explanation: "Matching frequencies produce maximum-amplitude vibration.", difficulty: "medium", tags: ["resonance"],
      conceptMissionId: "M2", conceptLabel: "Natural Frequency, Forced Vibration & Resonance",
    },
    {
      id: "m9-q3", type: "mcq", question: "In a longitudinal wave, particles vibrate",
      options: ["parallel to wave travel", "perpendicular to wave travel", "only upward", "with the wave from source to receiver"],
      answer: "parallel to wave travel", explanation: "Particles vibrate parallel to the direction of wave travel.",
      difficulty: "easy", tags: ["longitudinal wave"], conceptMissionId: "M3", conceptLabel: "Wave Motion & Types of Waves",
    },
    {
      id: "m9-q4", type: "numerical", question: "Sound travels at 340 m/s with frequency 400 Hz. Find its wavelength.",
      answer: "0.85 m", explanation: "λ = v/f = 340/400 = 0.85 m.", difficulty: "exam", tags: ["v = fλ", "wavelength"],
      conceptMissionId: "M4", conceptLabel: "Frequency, Wavelength and Wave Speed (v = fλ)",
    },
    {
      id: "m9-q5", type: "numerical", question: "A wave has frequency 500 Hz and wavelength 0.68 m. Find its speed.",
      answer: "340 m/s", explanation: "v = fλ = 500 × 0.68 = 340 m/s.", difficulty: "exam", tags: ["numerical", "wave speed"],
      conceptMissionId: "M5", conceptLabel: "Numericals using v = fλ",
    },
    {
      id: "m9-q6", type: "numerical", question: "An echo returns after 0.1 s. At 340 m/s, how far away is the reflector?",
      answer: "17 m", explanation: "d = vt/2 = 340 × 0.1 / 2 = 17 m.", difficulty: "exam", tags: ["echo", "reflection"],
      conceptMissionId: "M6", conceptLabel: "Reflection, Echo & Reverberation",
    },
    {
      id: "m9-q7", type: "mcq", question: "Which frequency is ultrasonic for humans?",
      options: ["10 Hz", "200 Hz", "2 kHz", "25 kHz"], answer: "25 kHz",
      explanation: "Ultrasonic sound is above about 20 kHz.", difficulty: "easy", tags: ["ultrasonic", "audibility"],
      conceptMissionId: "M7", conceptLabel: "Limits of Audibility & Ultrasonic Uses",
    },
    {
      id: "m9-q8", type: "short", question: "How can an underwater earthquake produce a tsunami?",
      answer: "It displaces a large volume of ocean water and generates gigantic waves.",
      explanation: "Sea-floor movement displaces the water column and starts tsunami waves.", difficulty: "medium", tags: ["tsunami", "seismic waves"],
      conceptMissionId: "M8", conceptLabel: "Seismic Waves and Tsunami",
    },
  ],
  recap: {
    summary: [
      "The full chapter map is connected from oscillation to seismic waves.",
      "Every final-test answer updates its exact concept; only mistakes become revision work.",
      "The saved result now decides the next lesson and spaced-revision task.",
    ],
    mustRemember: ["D-F-C-A; use v = fλ in SI units and vt/2 for echo distance"],
  },
  revisionSave: {
    flashcards: [
      { front: "Wave speed relation?", back: "v = fλ." },
      { front: "Resonance condition?", back: "Forcing frequency equals natural frequency." },
      { front: "Echo distance relation?", back: "d = vt/2." },
      { front: "Human audible range?", back: "About 20 Hz to 20 kHz." },
    ],
    revisionNotes: ["D-F-C-A, formula units and the echo factor 2"],
    weakAreaTags: ["chapter test corrections", "formula units", "exam conditions"],
  },
  qualityFlags: { needsHumanReview: false },
});

const SOUND_WAVES_SEEDS: TuitionLessonSeed[] = [M1, M2, M3, M4, M5, M6, M7, M8, M9];

const ALL_PHYSICS_SEEDS: TuitionLessonSeed[] = [
  ...SOUND_WAVES_SEEDS,
  ...LENSES_SEEDS,
  ...COLOURS_VISION_SEEDS,
  ...ELECTRIC_ENERGY_SEEDS,
  ...ELECTROMAGNETIC_INDUCTION_SEEDS,
  ...MECHANICAL_ADVANTAGE_SEEDS,
  ...MAGNETIC_EFFECT_SEEDS,
  ...CHEMISTRY_NOMENCLATURE_SEEDS,
  ...CHEMISTRY_P1_C1_SEEDS,
  ...BIOLOGY_P1_C1_SEEDS,
  ...BIOLOGY_P1_C2_SEEDS,
  ...BIOLOGY_P1_C3_SEEDS,
  ...BIOLOGY_P1_C4_SEEDS,
  ...BIOLOGY_P1_C5_SEEDS,
  ...BIOLOGY_P1_C6_SEEDS,
];

const SEED_INDEX = new Map<string, TuitionLessonSeed>(
  ALL_PHYSICS_SEEDS.map((seed) => [`${seed.chapterId}|${seed.missionId}`, seed]),
);

/** All curated lesson seeds. */
export function getAllLessonSeeds(): TuitionLessonSeed[] {
  return [...ALL_PHYSICS_SEEDS];
}

export function getSoundWavesSeeds(): TuitionLessonSeed[] {
  return [...SOUND_WAVES_SEEDS];
}

export function getLensesSeeds(): TuitionLessonSeed[] {
  return [...LENSES_SEEDS];
}

export function getColoursVisionSeeds(): TuitionLessonSeed[] {
  return [...COLOURS_VISION_SEEDS];
}

export function getElectricEnergySeeds(): TuitionLessonSeed[] {
  return [...ELECTRIC_ENERGY_SEEDS];
}

export function getElectromagneticInductionSeeds(): TuitionLessonSeed[] {
  return [...ELECTROMAGNETIC_INDUCTION_SEEDS];
}

export function getMechanicalAdvantageSeeds(): TuitionLessonSeed[] {
  return [...MECHANICAL_ADVANTAGE_SEEDS];
}

export function getMagneticEffectSeeds(): TuitionLessonSeed[] {
  return [...MAGNETIC_EFFECT_SEEDS];
}

/** Lookup a lesson seed by chapter + mission. Returns null when not curated. */
export function getPhysicsLessonSeed(
  chapterId: string | null | undefined,
  missionId: string | null | undefined,
): TuitionLessonSeed | null {
  if (!chapterId || !missionId) return null;
  return SEED_INDEX.get(`${chapterId}|${missionId}`) ?? null;
}

export function hasPhysicsLessonSeed(chapterId: string | null | undefined, missionId: string | null | undefined): boolean {
  return getPhysicsLessonSeed(chapterId, missionId) !== null;
}

export type PhysicsSeedCatalogMission = {
  mission_id: string;
  mission_title: string;
  contentType: LessonSeedContentType;
  canTeach: boolean;
  tags: string[];
};

/**
 * Catalog missions (selectable units) defined by the seeds for a chapter.
 * PYQ-placeholder content is excluded so it is never picked as a daily class.
 */
export function getPhysicsSeedCatalogMissions(chapterId: string): PhysicsSeedCatalogMission[] {
  return ALL_PHYSICS_SEEDS.filter((seed) => seed.chapterId === chapterId && seed.contentType !== "pyq_placeholder").map(
    (seed) => ({
      mission_id: seed.missionId,
      mission_title: seed.missionTitle,
      contentType: seed.contentType,
      canTeach: seed.canTeach,
      tags: seed.tags,
    }),
  );
}

/** Chapter ids that have at least one curated, teachable seed. */
export function chaptersWithPhysicsSeeds(): string[] {
  return Array.from(new Set(ALL_PHYSICS_SEEDS.filter((seed) => seed.canTeach).map((seed) => seed.chapterId)));
}

export type CuratedChapter = {
  chapterId: string;
  subject: TuitionLessonSeed["subject"];
  chapterTitle: string;
  /** Teachable (non-PYQ) missions available in this chapter. */
  missionCount: number;
};

/**
 * Every chapter with at least one teachable seed, in authored order. This is
 * the registry the daily-tuition picker walks so a student's real subject and
 * progress choose today's chapter — instead of one hardcoded chapter. Physics,
 * Chemistry and Biology all live in one seed index, so all are returned here.
 */
export function getCuratedChapters(): CuratedChapter[] {
  const order: string[] = [];
  const byId = new Map<string, CuratedChapter>();
  for (const seed of ALL_PHYSICS_SEEDS) {
    if (!seed.canTeach || seed.contentType === "pyq_placeholder") continue;
    const existing = byId.get(seed.chapterId);
    if (existing) {
      existing.missionCount += 1;
    } else {
      order.push(seed.chapterId);
      byId.set(seed.chapterId, {
        chapterId: seed.chapterId,
        subject: seed.subject,
        chapterTitle: seed.chapterTitle,
        missionCount: 1,
      });
    }
  }
  return order.map((id) => byId.get(id) as CuratedChapter);
}

export const NOT_CURATED_MESSAGE =
  "This lesson is source-backed but its guided content is not curated yet for this mission.";