/**
 * Pure helpers for the continuous class step flow.
 * Step ids stay stable for localStorage resume; labels match product language.
 */

import type { TuitionLessonStepId } from "./classSessionData";
import { tuitionLessonSteps } from "./classSessionData";

export type ClassStepGateState = {
  practiceAnswer: string;
  practiceSubmitted: boolean;
  quizAnswers: Record<string, string>;
  quizSubmitted: boolean;
};

/** Marks lost must never exceed maxMarks. */
export function clampMarksLost(score: number, maxMarks: number): number {
  if (!Number.isFinite(maxMarks) || maxMarks <= 0) return 0;
  if (!Number.isFinite(score)) return maxMarks;
  const safeScore = Math.max(0, Math.min(maxMarks, score));
  return Math.max(0, Math.min(maxMarks, maxMarks - safeScore));
}

/** Score displayed to the student is always within [0, maxMarks]. */
export function clampScoreEstimate(score: number, maxMarks: number): number {
  if (!Number.isFinite(maxMarks) || maxMarks <= 0) return 0;
  if (!Number.isFinite(score)) return 0;
  return Math.max(0, Math.min(maxMarks, Math.round(score)));
}

/**
 * Required-answer gate: Your Turn cannot be treated complete without a real answer.
 * Empty or whitespace-only answers never count as submitted.
 */
export function isPracticeAnswerComplete(answer: string, submitted: boolean): boolean {
  return submitted && answer.trim().length > 0;
}

/**
 * Whether the student may leave the current step for the next one.
 * Session Plan / Teach / Video / Visual / Methods / Notes / Exam are free to continue.
 * Your Turn requires a submitted non-empty practice answer.
 * Quiz requires submitted, non-empty answers before it can be completed.
 */
export function canAdvanceFromStep(stepId: TuitionLessonStepId, state: ClassStepGateState): boolean {
  if (stepId === "your-turn") {
    return isPracticeAnswerComplete(state.practiceAnswer, state.practiceSubmitted);
  }
  if (stepId === "quiz") {
    const answers = Object.values(state.quizAnswers);
    return state.quizSubmitted && answers.length > 0 && answers.every((answer) => answer.trim().length > 0);
  }
  return true;
}

export function advanceBlockedReason(stepId: TuitionLessonStepId, state: ClassStepGateState): string | null {
  if (stepId === "your-turn" && !isPracticeAnswerComplete(state.practiceAnswer, state.practiceSubmitted)) {
    return "Write and submit your answer before continuing. Required answers cannot be skipped.";
  }
  if (stepId === "quiz" && !canAdvanceFromStep(stepId, state)) {
    return "Answer and submit every quiz question before continuing.";
  }
  return null;
}

/** Weak-area tags must come only from real mistakes (missing keywords / failed points). */
export function weakAreasFromMistakes(missingKeywords: string[], isCorrect: boolean): string[] {
  if (isCorrect) return [];
  return missingKeywords.map((tag) => tag.trim()).filter(Boolean);
}

export function stepIndex(stepId: TuitionLessonStepId): number {
  return tuitionLessonSteps.findIndex((step) => step.id === stepId);
}

export function productStepLabels(): string[] {
  return tuitionLessonSteps.map((step) => step.label);
}

/** True when every selected plan day subject is in the student's selected subjects. */
export function weekPlanSubjectsAreBound(
  daySubjects: string[],
  selectedSubjects: string[],
): boolean {
  if (selectedSubjects.length === 0) return daySubjects.length === 0;
  const allowed = new Set(selectedSubjects.map((s) => s.trim().toLowerCase()));
  return daySubjects.every((subject) => allowed.has(subject.trim().toLowerCase()));
}

/** Chapter context lock: practice/mission selection must not silently switch chapter. */
export function isSameChapterContext(
  expected: { chapterId?: string; chapter?: string },
  actual: { chapterId?: string; chapter?: string },
): boolean {
  if (expected.chapterId && actual.chapterId) {
    return expected.chapterId === actual.chapterId;
  }
  if (expected.chapter && actual.chapter) {
    return expected.chapter.trim().toLowerCase() === actual.chapter.trim().toLowerCase();
  }
  return true;
}

/** Normalize video pipeline status for student UI — never invent progress. */
export type HonestVideoUiStatus =
  | "queued"
  | "rendering"
  | "ready"
  | "failed"
  | "unavailable"
  | "plan_only";

export function mapVideoJobStatus(status: string | null | undefined): HonestVideoUiStatus {
  const value = (status ?? "").toLowerCase().trim();
  if (!value || value === "unavailable" || value === "not_available" || value === "not_generated") return "unavailable";
  if (value === "plan_only" || value === "renderer_coming_later") return "plan_only";
  if (value === "ready" || value === "complete" || value === "completed") return "ready";
  if (value === "failed" || value === "error" || value === "qa_failed") return "failed";
  if (value === "package_ready") return "queued";
  if (
    value === "rendering" ||
    value === "running" ||
    value === "audio_generating" ||
    value === "visuals_generating" ||
    value === "uploading" ||
    value === "planning" ||
    value === "script_ready"
  ) {
    return "rendering";
  }
  if (value === "queued") return "queued";
  return "unavailable";
}

export function videoStatusLabel(status: HonestVideoUiStatus): string {
  switch (status) {
    case "queued":
      return "Queued";
    case "rendering":
      return "Rendering";
    case "ready":
      return "Ready";
    case "failed":
      return "Failed";
    case "plan_only":
      return "Plan only";
    case "unavailable":
    default:
      return "Unavailable";
  }
}