"use client";

import Link from "next/link";
import { useRouter } from "next/navigation";
import { Sheet, SheetContent, SheetHeader, SheetTitle, SheetDescription, SheetFooter } from "@/components/animate-ui/primitives/radix/sheet";
import { LiquidButton } from "@/components/animate-ui/primitives/buttons/liquid-button";
import {
  ArrowLeft,
  BookOpen,
  FileImage,
  FileText,
  LoaderCircle,
  Search,
  Upload,
} from "lucide-react";
import { AnimatePresence, motion, useReducedMotion } from "framer-motion";
import { useEffect, useMemo, useRef, useState, type DragEvent, type ReactNode, type RefObject } from "react";
import { DocDoeLogoMark } from "@/components/landing/DocDoeLogoMark";
import { uploadDocument } from "@/lib/api/documents";
import { saveStudyProfile } from "@/lib/api/brain";
import { normalizeApiError } from "@/lib/api/client";
import { hasLiveSession } from "@/lib/api/mode";
import {
  completeOnboarding,
  emptyStudyProfile,
  getOnboardingProfile,
  isOnboardingCompleted,
  labelForOnboardingGoal,
  saveOnboardingProfile,
  saveStudyProfileId,
  skipOnboarding,
  type BoardChoice,
  type ClassLevelChoice,
  type FirstUploadStatus,
  type OnboardingGoalChoice,
  type PrimaryNeedChoice,
  type StreamChoice,
  type StudentStudyProfile,
} from "@/lib/onboarding";
import { cn } from "@/lib/utils";
import {
  MATERIAL_UPLOAD_ACCEPT,
  validateStudentUpload,
} from "@/lib/uploads/document-upload-contract";

type SetupScreen = "welcome" | "context" | "subjects" | "exam-mode" | "material" | "ready";
type MaterialKind = "notes" | "chapter" | "question-paper";

const progression: Array<{ key: Exclude<SetupScreen, "welcome">; label: string }> = [
  { key: "context", label: "Context" },
  { key: "subjects", label: "Subjects" },
  { key: "exam-mode", label: "Exam mode" },
  { key: "material", label: "Material" },
  { key: "ready", label: "Ready" },
];

const boardOptions: BoardChoice[] = ["Kerala HSE", "Kerala SSLC", "CBSE", "ICSE", "Other State Board", "Other"];
const classOptions: ClassLevelChoice[] = ["SSLC / Class 10", "+1 / Class 11", "+2 / Class 12", "College", "Other"];
const streamOptions: StreamChoice[] = ["General", "Science", "Commerce", "Humanities", "Computer Science", "Other"];
const subjectOptions = [
  "Physics",
  "Chemistry",
  "Biology",
  "Mathematics",
  "Computer Science",
  "English",
  "Malayalam",
  "Accountancy",
  "Business Studies",
  "Economics",
] as const;

const subjectCombinations: Array<{ label: string; subjects: readonly string[] }> = [
  { label: "Science Stream", subjects: ["Physics", "Chemistry", "Mathematics", "Computer Science"] },
  { label: "Commerce Stream", subjects: ["Accountancy", "Business Studies", "Economics", "Mathematics"] },
  { label: "Humanities Stream", subjects: ["English", "Malayalam", "Economics", "Computer Science"] },
];

const examGoals: Array<{ id: OnboardingGoalChoice; title: string; text: string }> = [
  { id: "last_night_prep", title: "Last-night prep", text: "Fastest path when the exam is close." },
  {
    id: "pyq_intelligence",
    title: "PYQ intelligence",
    text: "Repeated topics, high-mark chapters, and scoring patterns.",
  },
  { id: "understand_chapters", title: "Understand chapters", text: "Hard concepts explained without extra noise." },
  { id: "practice_mode", title: "Practice mode", text: "Quizzes, flashcards, and revision checks." },
  { id: "full_study_path", title: "Full study path", text: "A clear order for what to study next." },
];

const materialKinds: Array<{ id: MaterialKind; title: string; description: string; icon: typeof FileText }> = [
  { id: "notes", title: "Notes", description: "PDF or plain-text export", icon: FileImage },
  { id: "chapter", title: "Chapter PDF", description: "A chapter or portion", icon: BookOpen },
  { id: "question-paper", title: "Question paper", description: "Past paper or PYQ", icon: FileText },
];

const primaryNeedForGoal: Record<OnboardingGoalChoice, PrimaryNeedChoice> = {
  last_night_prep: "last_night_plan",
  pyq_intelligence: "pyq_intelligence",
  understand_chapters: "scoring_notes",
  practice_mode: "quiz_me",
  full_study_path: "what_to_study",
};

const screenIndex: Record<SetupScreen, number> = {
  welcome: 0,
  context: 0,
  subjects: 1,
  "exam-mode": 2,
  material: 3,
  ready: 4,
};

const ease = [0.22, 1, 0.36, 1] as const;

function createProfile(): StudentStudyProfile {
  const now = new Date().toISOString();
  return { ...emptyStudyProfile, createdAt: now, updatedAt: now };
}

function profilePayload(profile: StudentStudyProfile) {
  return {
    exam: profile.board || null,
    board: profile.board || null,
    grade: profile.classLevel || profile.grade || null,
    subject: profile.subjects?.[0] || profile.subject || null,
    chapter: null,
    topic: null,
    goal: labelForOnboardingGoal(profile.primaryGoal),
    time_left: null,
    level: "intermediate" as const,
    language_preference: "English",
    primary_need: profile.primaryNeed,
    weak_areas: [],
    onboarding_completed: Boolean(profile.onboardingCompleted),
    extra: {
      onboardingSkipped: Boolean(profile.onboardingSkipped),
      stream: profile.stream || null,
      subjects: profile.subjects ?? [],
      primaryGoal: profile.primaryGoal || null,
    },
  };
}

function documentStatus(status: string): FirstUploadStatus {
  if (status === "ready") return "ready";
  return status === "processing" || status === "uploaded" ? "processing" : "received";
}

export function StudySetupFlow({ className }: { className?: string }) {
  const router = useRouter();
  const reduceMotion = Boolean(useReducedMotion());
  const [mounted, setMounted] = useState(false);
  const [screen, setScreen] = useState<SetupScreen>("welcome");
  const [profile, setProfile] = useState<StudentStudyProfile>(() => createProfile());
  const [customSubject, setCustomSubject] = useState("");
  const [selectedMaterialKind, setSelectedMaterialKind] = useState<MaterialKind>("notes");
  const [selectedFile, setSelectedFile] = useState<File | null>(null);
  const [isDragging, setIsDragging] = useState(false);
  const [isUploading, setIsUploading] = useState(false);
  const [uploadNotice, setUploadNotice] = useState<string | null>(null);
  const [showSkipSheet, setShowSkipSheet] = useState(false);
  const fileInputRef = useRef<HTMLInputElement>(null);

  // Calculate completed steps for progress bar
  const completedSteps = useMemo(() => {
    let count = 0;
    if (profile.board) count++;
    if (profile.subjects?.length) count++;
    if (profile.primaryGoal) count++;
    if (profile.firstUploadDocumentId) count++;
    return count;
  }, [profile]);

  useEffect(() => {
    const id = window.setTimeout(() => {
      const stored = getOnboardingProfile();
      const editing = new URLSearchParams(window.location.search).get("edit") === "1";
      if (isOnboardingCompleted() && !editing) {
        router.replace("/home");
        return;
      }
      if (stored) setProfile({ ...emptyStudyProfile, ...stored });
      if (editing) setScreen("context");
      setMounted(true);
    }, 0);
    return () => window.clearTimeout(id);
  }, [router]);

  // Keyboard navigation
  useEffect(() => {
    const handleKeyDown = (event: KeyboardEvent) => {
      if (event.key === "Escape") {
        setShowSkipSheet(true);
        return;
      }
      if (event.key === "Enter" && event.ctrlKey) {
        event.preventDefault();
        // Navigate to next screen based on current screen
        const nextMap: Partial<Record<SetupScreen, SetupScreen>> = {
          welcome: "context",
          context: "subjects",
          subjects: "exam-mode",
          "exam-mode": "material",
          material: "ready",
        };
        const next = nextMap[screen];
        if (next) goNext(next);
      }
      if (event.key === "Backspace" && !event.ctrlKey && !event.metaKey) {
        const target = event.target as HTMLElement;
        if (target.tagName !== "INPUT" && target.tagName !== "TEXTAREA") {
          event.preventDefault();
          const backMap: Partial<Record<SetupScreen, SetupScreen>> = {
            context: "welcome",
            subjects: "context",
            "exam-mode": "subjects",
            material: "exam-mode",
            ready: "material",
          };
          const back = backMap[screen];
          if (back) goNext(back);
        }
      }
    };

    window.addEventListener("keydown", handleKeyDown);
    return () => window.removeEventListener("keydown", handleKeyDown);
  }, [screen]);

  function updateProfile(patch: Partial<StudentStudyProfile>) {
    setProfile((current) => {
      const updated = saveOnboardingProfile({ ...current, ...patch });
      return updated;
    });
  }

  function goNext(next: SetupScreen) {
    setScreen(next);
  }

  function persistCompletedProfile(nextProfile: StudentStudyProfile) {
    const completed = completeOnboarding(nextProfile) ?? nextProfile;
    setProfile(completed);
    if (!hasLiveSession()) return;
    void saveStudyProfile(profilePayload(completed))
      .then((saved) => saveStudyProfileId(saved.id))
      .catch(() => {
        // Local profile remains usable when the API is unavailable during beta.
      });
  }

  async function handleSkipSetup() {
    const skippedItems = [];
    if (!profile.board) skippedItems.push("Personalized exam signals");
    if (!profile.subjects?.length) skippedItems.push("Subject-specific recommendations");
    if (!profile.primaryGoal) skippedItems.push("Tailored study modes");
    if (!profile.firstUploadDocumentId) skippedItems.push("First study material analysis");
    
    if (skippedItems.length > 2) {
      setShowSkipSheet(true);
      return;
    }
    
    await completeSkip();
  }

  async function completeSkip() {
    const skipped = skipOnboarding(profile);
    if (hasLiveSession()) {
      try {
        const saved = await saveStudyProfile(profilePayload(skipped));
        saveStudyProfileId(saved.id);
      } catch {
        // Skipping must never trap a student behind network availability.
      }
    }
    router.push("/home");
  }

  function selectSubject(subject: string) {
    const current = profile.subjects ?? [];
    const subjects = current.includes(subject) ? current.filter((item) => item !== subject) : [...current, subject];
    updateProfile({ subjects, subject: subjects[0] ?? "" });
  }

  function addCustomSubject() {
    const subject = customSubject.trim();
    if (!subject) return;
    const current = profile.subjects ?? [];
    if (!current.includes(subject)) updateProfile({ subjects: [...current, subject], subject: current[0] ?? subject });
    setCustomSubject("");
  }

  function toggleGoal(goal: OnboardingGoalChoice) {
    const current = profile.selectedGoals ?? [];
    if (current.includes(goal)) {
      const selectedGoals = current.filter((item) => item !== goal);
      const primaryGoal = profile.primaryGoal === goal ? selectedGoals[0] ?? "" : profile.primaryGoal ?? "";
      updateProfile({
        selectedGoals,
        primaryGoal,
        primaryNeed: primaryGoal ? primaryNeedForGoal[primaryGoal] : "what_to_study",
      });
      return;
    }
    const selectedGoals = [...current, goal];
    const primaryGoal = profile.primaryGoal || goal;
    updateProfile({ selectedGoals, primaryGoal, primaryNeed: primaryNeedForGoal[primaryGoal] });
  }

  function makePrimaryGoal(goal: OnboardingGoalChoice) {
    updateProfile({ primaryGoal: goal, primaryNeed: primaryNeedForGoal[goal] });
  }

  function handleFile(file: File | undefined) {
    if (!file) return;
    const validation = validateStudentUpload(file, "material");
    if (!validation.ok) {
      setUploadNotice(validation.message);
      return;
    }
    setSelectedFile(file);
    setUploadNotice(null);
  }

  function handleDrop(event: DragEvent<HTMLDivElement>) {
    event.preventDefault();
    setIsDragging(false);
    handleFile(event.dataTransfer.files[0]);
  }

  function finishWithoutUpload() {
    const nextProfile = saveOnboardingProfile({
      ...profile,
      sourceMode: "skip",
      firstUploadStatus: "skipped",
    });
    persistCompletedProfile(nextProfile);
    setScreen("ready");
  }

  async function uploadFirstMaterial() {
    if (!selectedFile) return;
    setIsUploading(true);
    setUploadNotice(null);
    try {
      // Simulate progress for better UX
      setUploadNotice("Reading your material...");
      await new Promise(resolve => setTimeout(resolve, 500));
      
      setUploadNotice("Finding study text...");
      const document = await uploadDocument({
        file: selectedFile,
        title: selectedFile.name.replace(/\.[^/.]+$/, ""),
        subject: profile.subjects?.[0] || undefined,
        syllabus: profile.board || undefined,
      });
      
      setUploadNotice("Preparing study signals...");
      await new Promise(resolve => setTimeout(resolve, 300));
      
      const nextProfile = saveOnboardingProfile({
        ...profile,
        sourceMode: "upload",
        sourceId: document.id,
        sourceTitle: document.title,
        firstUploadDocumentId: document.id,
        firstUploadStatus: documentStatus(document.status),
      });
      setUploadNotice("Material received. DocDoe will use it inside your study space.");
      persistCompletedProfile(nextProfile);
      setScreen("ready");
    } catch (error) {
      const errorMessage = normalizeApiError(error) || "Could not upload this material right now.";
      setUploadNotice(`${errorMessage} You can retry, skip, or try a different file.`);
    } finally {
      setIsUploading(false);
    }
  }

  const stage = screenIndex[screen];
  const subjects = profile.subjects ?? [];
  const selectedGoals = profile.selectedGoals ?? [];

  if (!mounted) {
    return (
      <main className={cn(className, "docdoe-setup grid min-h-svh place-items-center bg-[#030303] text-white")}>
        <LoaderCircle className="size-5 animate-spin text-white/45 motion-reduce:animate-none" aria-label="Loading study setup" />
      </main>
    );
  }

  return (
    <main className={cn(className, "docdoe-setup relative min-h-svh overflow-x-hidden bg-[#030303] text-[#f8fafc]")}>
      <div className="pointer-events-none absolute inset-x-0 top-0 h-px bg-gradient-to-r from-transparent via-white/28 to-transparent" />
      <div className="pointer-events-none absolute left-1/2 top-0 h-[24rem] w-[min(46rem,100vw)] -translate-x-1/2 bg-[radial-gradient(ellipse_at_top,rgba(255,255,255,0.065),transparent_62%)]" />

      <header className="relative z-10 mx-auto flex w-full max-w-[1160px] items-center justify-between px-5 pb-5 pt-5 sm:px-8 sm:pt-7">
        <Link href="/" className="inline-flex items-center gap-2.5 shrink-0" aria-label="DocDoe AI home">
          <span className="grid size-10 place-items-center rounded-xl border border-white/10 bg-[#080808]">
            <DocDoeLogoMark className="size-7 text-white" aria-hidden="true" />
          </span>
          <span className="text-[15px] font-semibold tracking-[-0.03em]">DocDoe AI</span>
        </Link>
        <button
          type="button"
          onClick={() => void handleSkipSetup()}
          className="min-h-12 shrink-0 rounded-full border border-white/10 px-4 text-[12px] font-medium text-white/58 transition hover:border-white/20 hover:text-white focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-white/35"
        >
          Skip for now
        </button>
      </header>

      <nav 
        className="relative z-10 mx-auto w-full max-w-[1160px] overflow-x-auto px-5 sm:px-8" 
        aria-label="Study profile progress"
        role="progressbar"
        aria-valuenow={completedSteps}
        aria-valuemin={0}
        aria-valuemax={4}
        aria-valuetext={`${completedSteps} of 4 steps completed`}
      >
        <ol className="grid grid-cols-5 min-w-[300px]">
          {progression.map((item, index) => {
            const active = index === stage && screen !== "welcome";
            const done = index < stage || screen === "ready";
            return (
              <li key={item.key} className="relative pb-5 shrink-0">
                <div className="absolute left-[0.58rem] right-0 top-[0.43rem] h-px bg-white/[0.09]" aria-hidden="true">
                  {done ? <span className="block h-full bg-white/48" /> : null}
                </div>
                <div className="relative flex flex-col gap-2">
                  <span
                    className={cn(
                      "relative z-10 block size-[0.9rem] rounded-full border bg-[#030303] transition-colors",
                      active
                        ? "docdoe-setup-signal-dot border-white/70 after:absolute after:inset-[3px] after:rounded-full after:bg-white/80"
                        : done
                          ? "border-white/52 bg-white/80"
                          : "border-white/20",
                    )}
                  />
                  <span className={cn("text-[10px] font-medium tracking-[0.08em] sm:text-[11px]", active ? "text-white/92" : done ? "text-white/52" : "text-white/38")}>
                    <span className="mr-1 text-white/30">0{index + 1}</span>
                    <span className="hidden min-[370px]:inline">{item.label}</span>
                  </span>
                </div>
              </li>
            );
          })}
        </ol>
      </nav>

      <div className="relative z-10 mx-auto grid w-full max-w-[1160px] gap-8 px-5 pb-8 pt-6 sm:px-8 sm:pt-10 lg:grid-cols-[minmax(0,1fr)_350px] lg:gap-12">
        <div className="min-w-0">
          <AnimatePresence mode="wait" initial={false}>
            <motion.section
              key={screen}
              initial={reduceMotion ? false : { opacity: 0, y: 12 }}
              animate={{ opacity: 1, y: 0 }}
              exit={reduceMotion ? undefined : { opacity: 0, y: -8 }}
              transition={{ duration: reduceMotion ? 0 : 0.2, ease }}
            >
              {screen === "welcome" ? (
                <WelcomeScreen onStart={() => goNext("context")} onSkip={() => void handleSkipSetup()} />
              ) : null}
              {screen === "context" ? (
                <ContextScreen
                  profile={profile}
                  onChange={updateProfile}
                  onContinue={() => goNext("subjects")}
                  onBack={() => goNext("welcome")}
                />
              ) : null}
              {screen === "subjects" ? (
                <SubjectsScreen
                  subjects={subjects}
                  customSubject={customSubject}
                  onSubjectChange={selectSubject}
                  onCustomChange={setCustomSubject}
                  onCustomAdd={addCustomSubject}
                  onCombinationAdd={(combinationSubjects) => {
                    const current = profile.subjects ?? [];
                    const newSubjects = [...new Set([...current, ...combinationSubjects])];
                    updateProfile({ subjects: newSubjects, subject: newSubjects[0] ?? "" });
                  }}
                  onContinue={() => goNext("exam-mode")}
                  onBack={() => goNext("context")}
                />
              ) : null}
              {screen === "exam-mode" ? (
                <ExamModeScreen
                  selected={selectedGoals}
                  primary={profile.primaryGoal ?? ""}
                  onToggle={toggleGoal}
                  onPrimary={makePrimaryGoal}
                  onContinue={() => goNext("material")}
                  onBack={() => goNext("subjects")}
                />
              ) : null}
              {screen === "material" ? (
                <MaterialScreen
                  materialKind={selectedMaterialKind}
                  file={selectedFile}
                  inputRef={fileInputRef}
                  dragging={isDragging}
                  uploading={isUploading}
                  notice={uploadNotice}
                  onKindSelect={setSelectedMaterialKind}
                  onFile={handleFile}
                  onFileRemove={() => setSelectedFile(null)}
                  onDragEnter={() => setIsDragging(true)}
                  onDragLeave={() => setIsDragging(false)}
                  onDrop={handleDrop}
                  onUpload={() => void uploadFirstMaterial()}
                  onSkip={finishWithoutUpload}
                  onBack={() => goNext("exam-mode")}
                />
              ) : null}
              {screen === "ready" ? (
                <ReadyScreen
                  profile={profile}
                  onDashboard={() => router.push("/home")}
                  onUploadAnother={() => router.push("/upload")}
                />
              ) : null}
            </motion.section>
          </AnimatePresence>
        </div>

        <SignalPreview profile={profile} screen={screen} />
      </div>

      <Sheet open={showSkipSheet} onOpenChange={setShowSkipSheet}>
        <SheetContent side="bottom" className="rounded-t-2xl">
          <SheetHeader>
            <SheetTitle>Skip setup?</SheetTitle>
            <SheetDescription>
              You can always set this up later, but DocDoe works best with your exam context.
            </SheetDescription>
          </SheetHeader>
          <SheetFooter className="mt-6">
            <LiquidButton variant="secondary" onClick={() => setShowSkipSheet(false)}>
              Continue setup
            </LiquidButton>
            <LiquidButton onClick={() => { setShowSkipSheet(false); completeSkip(); }}>
              Skip anyway
            </LiquidButton>
          </SheetFooter>
        </SheetContent>
      </Sheet>
    </main>
  );
}

function StepHeading({ title, body, eyebrow }: { title: string; body: string; eyebrow?: string }) {
  return (
    <div className="max-w-[590px]">
      {eyebrow ? (
        <p className="text-[11px] font-semibold uppercase tracking-[0.22em] text-white/38">{eyebrow}</p>
      ) : (
        <p className="text-[11px] font-semibold uppercase tracking-[0.22em] text-white/38">Build your exam path</p>
      )}
      <h1 className="mt-4 text-[clamp(2.1rem,7.5vw,3.35rem)] font-semibold leading-[1.02] tracking-[-0.065em] text-[#f8fafc]">
        {title}
      </h1>
      <p className="mt-4 max-w-[520px] text-[15px] leading-7 text-white/57 sm:text-[16px]">{body}</p>
    </div>
  );
}

function WelcomeScreen({ onStart, onSkip }: { onStart: () => void; onSkip: () => void }) {
  return (
    <div className="pt-5 sm:pt-10">
      <StepHeading
        eyebrow="SETUP TAKES LESS THAN A MINUTE"
        title="Let's build your exam path."
        body="Tell DocDoe what you're preparing for. Then upload material and get a study path built around what matters."
      />
      <div className="mt-10 grid max-w-[560px] grid-cols-3 items-center gap-2 rounded-[22px] border border-white/[0.08] bg-white/[0.02] p-4 sm:p-5">
        {["Material", "Signals", "Study path"].map((label, index) => (
          <div key={label} className="flex min-w-0 items-center gap-2">
            <span className={cn("size-2 shrink-0 rounded-full", index === 1 ? "bg-white/70" : "bg-white/28")} />
            <span className="truncate text-[12px] font-medium text-white/58">{label}</span>
            {index < 2 ? <span className="ml-auto h-px flex-1 bg-white/12" aria-hidden="true" /> : null}
          </div>
        ))}
      </div>
      <div className="mt-10 flex flex-col gap-3 sm:flex-row">
        <LiquidButton onClick={onStart} className="!min-h-12">Start setup</LiquidButton>
        <SecondaryAction onClick={onSkip}>Skip for now</SecondaryAction>
      </div>
    </div>
  );
}

function ContextScreen({
  profile,
  onChange,
  onContinue,
  onBack,
}: {
  profile: StudentStudyProfile;
  onChange: (patch: Partial<StudentStudyProfile>) => void;
  onContinue: () => void;
  onBack: () => void;
}) {
  const valid = Boolean(profile.board && profile.classLevel && profile.stream);
  return (
    <div>
      <StepHeading
        title="What exam are you preparing for?"
        body="DocDoe uses this to understand your board, class, and stream. Kerala HSE is supported first for closed beta."
      />
      <div className="mt-9 grid gap-7">
        <OptionGroup
          title="Board / exam system"
          values={boardOptions}
          selected={profile.board}
          onSelect={(board) => onChange({ board, exam: board })}
          recommendedValue="Kerala HSE"
          helper="Your exam board determines the syllabus and question patterns."
        />
        <OptionGroup
          title="Class"
          values={classOptions}
          selected={profile.classLevel ?? ""}
          onSelect={(classLevel) => onChange({ classLevel, grade: classLevel })}
          helper="Your current academic level helps tailor difficulty appropriately."
        />
        <OptionGroup
          title="Stream"
          values={streamOptions}
          selected={profile.stream ?? ""}
          onSelect={(stream) => onChange({ stream })}
          helper="Your subject stream determines available electives and focus areas."
        />
      </div>
      {!valid && (
        <p role="alert" className="mt-5 flex items-center gap-2 text-[12px] text-white/48">
          <span className="size-1.5 rounded-full bg-white/68" />
          Choose your board, class, and stream to continue.
        </p>
      )}
      <StepActions onBack={onBack} onNext={onContinue} disabled={!valid} />
    </div>
  );
}

function SubjectsScreen({
  subjects,
  customSubject,
  onSubjectChange,
  onCustomChange,
  onCustomAdd,
  onCombinationAdd,
  onContinue,
  onBack,
}: {
  subjects: string[];
  customSubject: string;
  onSubjectChange: (subject: string) => void;
  onCustomChange: (value: string) => void;
  onCustomAdd: () => void;
  onCombinationAdd: (combinationSubjects: readonly string[]) => void;
  onContinue: () => void;
  onBack: () => void;
}) {
  const hasSubjects = subjects.length > 0;
  const [search, setSearch] = useState("");
  const filteredSubjects = subjectOptions.filter((subject) =>
    subject.toLowerCase().includes(search.trim().toLowerCase()),
  );
  
  function addCombination(combinationSubjects: readonly string[]) {
    onCombinationAdd(combinationSubjects);
  }

  return (
    <div>
      <StepHeading
        title="What subjects should DocDoe focus on?"
        body="Pick the subjects you want help with first. You can change this later."
      />
      <div className="mt-6 flex flex-wrap gap-2">
        {subjectCombinations.map((combo) => (
          <button
            key={combo.label}
            type="button"
            onClick={() => addCombination(combo.subjects)}
            className="min-h-11 rounded-lg border border-white/12 bg-white/[0.02] px-3 text-[11px] font-medium text-white/50 transition hover:border-white/24 hover:text-white/70"
          >
            + {combo.label}
          </button>
        ))}
      </div>
      <label className="mt-6 flex h-12 max-w-[440px] items-center gap-3 rounded-xl border border-white/[0.1] bg-[#080808] px-4 focus-within:border-white/26">
        <Search className="size-4 shrink-0 text-white/35" strokeWidth={1.7} />
        <span className="sr-only">Search subjects</span>
        <input
          value={search}
          onChange={(event) => setSearch(event.target.value)}
          placeholder="Search subjects"
          className="min-w-0 flex-1 bg-transparent text-[13px] text-white outline-none placeholder:text-white/30"
        />
      </label>
      <div className="mt-6 flex max-w-[640px] flex-wrap gap-2.5">
        {filteredSubjects.map((subject) => (
          <button
            key={subject}
            type="button"
            aria-pressed={subjects.includes(subject)}
            onClick={() => onSubjectChange(subject)}
            className={cn(
              "relative min-h-12 rounded-full border px-5 text-[13px] font-medium transition-all duration-200 ease-out focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-white/50 focus-visible:ring-offset-2 focus-visible:ring-offset-[#030303] hover:-translate-y-px active:scale-95",
              subjects.includes(subject)
                ? "border-white/28 bg-white/[0.09] text-white after:absolute after:inset-0 after:rounded-full after:border after:border-white/28"
                : "border-white/[0.09] bg-[#080808] text-white/58 hover:border-white/17 hover:text-white",
            )}
          >
            {subject}
            {subjects.includes(subject) && (
              <span className="absolute right-2 top-1/2 -translate-y-1/2 size-1.5 rounded-full bg-white/70" aria-hidden="true" />
            )}
          </button>
        ))}
        {filteredSubjects.length === 0 ? (
          <p className="py-3 text-[12px] text-white/40">
            No match. Add your subject below.
          </p>
        ) : null}
      </div>
      {!hasSubjects && (
        <p role="alert" className="mt-4 flex items-center gap-2 text-[12px] text-white/48">
          <span className="size-1.5 rounded-full bg-white/68" />
          Choose at least one subject to continue.
        </p>
      )}
      <div className="mt-7 flex max-w-[440px] gap-2">
        <label className="sr-only" htmlFor="custom-subject">
          Add another subject
        </label>
        <input
          id="custom-subject"
          value={customSubject}
          onChange={(event) => onCustomChange(event.target.value)}
          onKeyDown={(event) => {
            if (event.key === "Enter") {
              event.preventDefault();
              onCustomAdd();
            }
          }}
          placeholder="Add another subject"
          className="h-12 min-w-0 flex-1 rounded-xl border border-white/[0.1] bg-[#080808] px-4 text-[13px] text-white outline-none placeholder:text-white/30 transition-all duration-200 ease-out focus:border-white/40 focus:shadow-[0_0_0_3px_rgba(255,255,255,0.12)] focus:bg-white/[0.02]"
        />
        <button
          type="button"
          onClick={onCustomAdd}
          aria-label={`Add ${customSubject || "custom subject"}`}
          className="h-12 rounded-xl border border-white/[0.11] px-4 text-[13px] font-medium text-white/70 transition hover:border-white/22 hover:text-white"
        >
          Add
        </button>
      </div>
      <StepActions onBack={onBack} onNext={onContinue} disabled={!hasSubjects} />
    </div>
  );
}

function ExamModeScreen({
  selected,
  primary,
  onToggle,
  onPrimary,
  onContinue,
  onBack,
}: {
  selected: OnboardingGoalChoice[];
  primary: OnboardingGoalChoice | "";
  onToggle: (goal: OnboardingGoalChoice) => void;
  onPrimary: (goal: OnboardingGoalChoice) => void;
  onContinue: () => void;
  onBack: () => void;
}) {
  return (
    <div>
      <StepHeading
        title="What do you need most right now?"
        body="Choose your main focus. You can use other modes later."
      />
      <div className="mt-8 grid max-w-[670px] gap-2.5 sm:grid-cols-2">
        {examGoals.map((goal) => {
          const checked = selected.includes(goal.id);
          const isPrimary = primary === goal.id;
          return (
            <div
              key={goal.id}
              className={cn(
                "relative flex min-h-[126px] flex-col rounded-[18px] border px-4 py-4 transition-all duration-250 ease-out",
                checked
                  ? "border-white/28 bg-white/[0.052] shadow-[0_0_0_1px_rgba(59,130,246,0.25)] hover:shadow-[0_0_0_1px_rgba(59,130,246,0.35)]"
                  : "border-white/[0.08] bg-[#080808] hover:border-white/14 hover:-translate-y-px hover:shadow-[0_4px_16px_rgba(0,0,0,0.4)]",
              )}
            >
              <button
                type="button"
                onClick={() => onToggle(goal.id)}
                aria-pressed={checked}
                className="absolute inset-0 rounded-[18px] focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-white/38 focus-visible:ring-offset-2 focus-visible:ring-offset-[#030303] active:scale-[0.99]"
                aria-label={`${checked ? "Remove" : "Select"} ${goal.title}`}
              />
              <div className="relative pointer-events-none flex items-start justify-between gap-3">
                <div>
                  <p className="text-[15px] font-medium tracking-[-0.02em] text-white/90">{goal.title}</p>
                  <p className="mt-2 text-[12.5px] leading-5 text-white/48">{goal.text}</p>
                </div>
                <span
                  className={cn(
                    "mt-1 size-2.5 shrink-0 rounded-full border",
                    checked ? "border-white/70 bg-white/80" : "border-white/22",
                  )}
                />
              </div>
              {checked ? (
                <button
                  type="button"
                  onClick={() => onPrimary(goal.id)}
                  aria-label={`${isPrimary ? "Primary focus" : `Set ${goal.title} as primary focus`}`}
                  className={cn(
                    "relative mt-auto self-start pt-3 text-[10px] font-semibold uppercase tracking-[0.17em] transition",
                    isPrimary ? "text-white/86" : "text-white/36 hover:text-white/62",
                  )}
                >
                  {isPrimary ? "Primary focus" : "Set as primary"}
                </button>
              ) : null}
            </div>
          );
        })}
      </div>
      <StepActions onBack={onBack} onNext={onContinue} disabled={!primary} />
    </div>
  );
}

function MaterialScreen({
  materialKind,
  file,
  inputRef,
  dragging,
  uploading,
  notice,
  onKindSelect,
  onFile,
  onFileRemove,
  onDragEnter,
  onDragLeave,
  onDrop,
  onUpload,
  onSkip,
  onBack,
}: {
  materialKind: MaterialKind;
  file: File | null;
  inputRef: RefObject<HTMLInputElement | null>;
  dragging: boolean;
  uploading: boolean;
  notice: string | null;
  onKindSelect: (kind: MaterialKind) => void;
  onFile: (file: File | undefined) => void;
  onFileRemove: () => void;
  onDragEnter: () => void;
  onDragLeave: () => void;
  onDrop: (event: DragEvent<HTMLDivElement>) => void;
  onUpload: () => void;
  onSkip: () => void;
  onBack: () => void;
}) {
  return (
    <div>
      <StepHeading
        title="Give DocDoe something to read."
        body="Upload notes, a chapter, or a question paper. DocDoe will use it to create your first study signal."
      />
      <div className="mt-8 grid gap-2 sm:grid-cols-3">
        {materialKinds.map((option) => {
          const Icon = option.icon;
          const active = option.id === materialKind;
          return (
            <button
              type="button"
              key={option.id}
              onClick={() => onKindSelect(option.id)}
              className={cn(
                "relative min-h-[100px] rounded-[16px] border p-3 text-left transition focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-white/30",
                active
                  ? "border-white/28 bg-white/[0.052] shadow-[0_0_0_1px_rgba(59,130,246,0.25)]"
                  : "border-white/[0.08] bg-[#080808] hover:border-white/16",
              )}
            >
              <Icon className="size-4 text-white/54" strokeWidth={1.65} aria-hidden="true" />
              <span className="mt-3 block text-[13px] font-medium text-white/84">{option.title}</span>
              <span className="mt-1 block text-[11px] text-white/42">{option.description}</span>
              {active && (
                <span className="absolute right-3 top-3 size-1.5 rounded-full bg-white/70" aria-hidden="true" />
              )}
            </button>
          );
        })}
      </div>
      <input
        ref={inputRef}
        type="file"
        accept={MATERIAL_UPLOAD_ACCEPT}
        className="sr-only"
        onChange={(event) => {
          onFile(event.target.files?.[0]);
          event.target.value = "";
        }}
      />
      <div
        onDragOver={(event) => event.preventDefault()}
        onDragEnter={onDragEnter}
        onDragLeave={onDragLeave}
        onDrop={onDrop}
        className={cn(
          "mt-4 rounded-[20px] border border-dashed px-5 py-7 transition",
          dragging ? "border-white/28 bg-white/[0.045]" : "border-white/[0.12] bg-white/[0.018]",
        )}
      >
        {file ? (
          <div className="flex items-center gap-3">
            <span className="grid size-11 shrink-0 place-items-center rounded-xl border border-white/10 bg-white/[0.035]">
              <FileText className="size-5 text-white/64" strokeWidth={1.65} />
            </span>
            <div className="min-w-0 flex-1">
              <p className="truncate text-[13px] font-medium text-white/86">{file.name}</p>
              <p className="mt-1 text-[11px] text-white/38">{(file.size / 1024 / 1024).toFixed(2)} MB · Selectable-text PDF or TXT</p>
            </div>
            <button 
              type="button" 
              onClick={onFileRemove} 
              aria-label={`Remove ${file.name}`}
              className="text-[12px] text-white/42 transition hover:text-white"
            >
              Remove
            </button>
          </div>
        ) : (
          <div className="text-center">
            <Upload className="mx-auto size-5 text-white/43" strokeWidth={1.6} aria-hidden="true" />
            <p className="mt-3 text-[13px] text-white/64">Drop a selectable-text PDF or TXT file here</p>
            <button
              type="button"
              onClick={() => inputRef.current?.click()}
              className="mt-4 min-h-11 rounded-full border border-white/14 px-5 text-[12px] font-medium text-white/72 transition hover:border-white/25 hover:text-white"
            >
              Choose file
            </button>
            <p className="mt-3 text-[11px] text-white/35">Up to 20 MB · scanned PDFs need selectable text</p>
          </div>
        )}
      </div>
      {notice ? <p role="alert" className="mt-3 text-[12px] leading-5 text-white/54">{notice}</p> : null}
      <div className="mt-9 flex flex-wrap items-center gap-3">
        <SecondaryAction onClick={onBack} icon="back">
          Back
        </SecondaryAction>
        {file ? (
          <LiquidButton onClick={onUpload} disabled={uploading} className="!min-h-12">
            {uploading ? "Receiving material..." : "Upload and continue"}
          </LiquidButton>
        ) : null}
        <button type="button" onClick={onSkip} className="min-h-12 px-3 text-[13px] text-white/45 transition hover:text-white/78">
          Skip and open DocDoe
        </button>
      </div>
    </div>
  );
}

function ReadyScreen({
  profile,
  onDashboard,
  onUploadAnother,
}: {
  profile: StudentStudyProfile;
  onDashboard: () => void;
  onUploadAnother: () => void;
}) {
  const summaries = [
    ["Board", profile.board || "Not selected"],
    ["Class", profile.classLevel || "Not selected"],
    ["Stream", profile.stream || "Not selected"],
    ["Subjects", profile.subjects?.join(", ") || "Add later"],
    ["Main focus", labelForOnboardingGoal(profile.primaryGoal)],
    [
      "First material",
      profile.firstUploadStatus === "ready" || profile.firstUploadStatus === "received"
        ? "Material received"
        : profile.firstUploadStatus === "processing"
          ? "Scanning pending"
          : "Upload from Sources",
    ],
  ];
  const hasMaterial = profile.firstUploadStatus === "ready" || profile.firstUploadStatus === "received";
  return (
    <div>
      <StepHeading
        title="Your exam path is ready."
        body="Start with an upload, generate notes, or open exam mode."
      />
      <div className="mt-9 max-w-[620px] overflow-hidden rounded-[22px] border border-white/[0.09] bg-[#080808]">
        {summaries.map(([label, value]) => (
          <div key={label} className="flex items-start justify-between gap-5 border-b border-white/[0.06] px-5 py-4 last:border-b-0">
            <span className="text-[12px] text-white/38">{label}</span>
            <span className="max-w-[64%] text-right text-[13px] font-medium text-white/78">{value}</span>
          </div>
        ))}
      </div>
      <div className="mt-9 flex flex-col gap-3 sm:flex-row">
        <LiquidButton onClick={onDashboard} className="!min-h-12">Open DocDoe</LiquidButton>
        <SecondaryAction onClick={onUploadAnother}>{hasMaterial ? "Upload another material" : "Upload material"}</SecondaryAction>
      </div>
    </div>
  );
}

function SignalPreview({ profile, screen }: { profile: StudentStudyProfile; screen: SetupScreen }) {
  const contextValue = profile.board ? `${profile.board} • ${profile.classLevel || "Class pending"}` : "Not set";
  const subjectLabel = profile.subjects?.slice(0, 2).join(", ") || "Awaiting subjects";
  const examModeValue = labelForOnboardingGoal(profile.primaryGoal);
  const materialValue = profile.firstUploadDocumentId ? "Material received" : screen === "material" ? "Ready for upload" : "Pending";

  const steps = [
    { label: "Context set", done: Boolean(profile.board) },
    { label: "Subjects chosen", done: Boolean(profile.subjects?.length) },
    { label: "Focus chosen", done: Boolean(profile.primaryGoal) },
    { label: "Material ready", done: Boolean(profile.firstUploadDocumentId) },
  ];

  const completedSteps = steps.filter((s) => s.done).length;
  const progressLabel = completedSteps === 4 ? "Signal found" : "Ready for signal";

  return (
    <aside aria-label="Study setup progress" className="hidden lg:block">
      <div className="sticky top-8 rounded-[24px] border border-white/[0.09] bg-[#070707] p-5 shadow-[0_28px_70px_rgba(0,0,0,0.22)]">
        <p className="text-[10px] font-semibold uppercase tracking-[0.22em] text-white/38">Study signal</p>
        <h2 className="mt-3 text-[20px] font-medium tracking-[-0.045em] text-white/92">Exam path setup</h2>
        <div className="mt-6 grid gap-0">
          <div className="relative grid grid-cols-[18px_1fr] gap-3 pb-6">
            <span className="mt-[5px] size-[9px] rounded-full border border-white/20 bg-[#070707]" />
            <div>
              <p className="text-[11px] font-medium text-white/40">Study context</p>
              <p className="mt-1 text-[12px] leading-5 text-white/68">{contextValue}</p>
            </div>
          </div>
          <div className="relative grid grid-cols-[18px_1fr] gap-3 pb-6">
            <span className="absolute bottom-0 left-[4px] top-3 w-px bg-white/[0.09]" />
            <span className={cn("mt-[5px] size-[9px] rounded-full border", profile.subjects?.length ? "border-white/70 bg-white/80" : "border-white/20 bg-[#070707]")} />
            <div>
              <p className="text-[11px] font-medium text-white/40">Subjects</p>
              <p className="mt-1 text-[12px] leading-5 text-white/68">{subjectLabel}</p>
            </div>
          </div>
          <div className="relative grid grid-cols-[18px_1fr] gap-3 pb-6">
            <span className="absolute bottom-0 left-[4px] top-3 w-px bg-white/[0.09]" />
            <span className={cn("mt-[5px] size-[9px] rounded-full border", profile.primaryGoal ? "border-white/70 bg-white/80" : "border-white/20 bg-[#070707]")} />
            <div>
              <p className="text-[11px] font-medium text-white/40">Exam mode</p>
              <p className="mt-1 text-[12px] leading-5 text-white/68">{examModeValue}</p>
            </div>
          </div>
          <div className="relative grid grid-cols-[18px_1fr] gap-3 pb-0">
            <span className={cn("mt-[5px] size-[9px] rounded-full border", profile.firstUploadDocumentId ? "border-white/70 bg-white/80" : "border-white/20 bg-[#070707]")} />
            <div>
              <p className="text-[11px] font-medium text-white/40">First material</p>
              <p className="mt-1 text-[12px] leading-5 text-white/68">{materialValue}</p>
            </div>
          </div>
        </div>
        <div className="mt-7 border-t border-white/[0.07] pt-4">
          <div className="flex items-center justify-between text-[10px] font-semibold uppercase tracking-[0.16em] text-white/32">
            <span>{completedSteps}/4 steps</span>
            <span>{progressLabel}</span>
          </div>
          <div className="mt-3 h-px bg-white/[0.08]">
            <span className="block h-px bg-gradient-to-r from-white/22 to-white/55" style={{ width: `${(completedSteps / 4) * 100}%` }} />
          </div>
        </div>
      </div>
    </aside>
  );
}

function OptionGroup<T extends string>({
  title,
  values,
  selected,
  onSelect,
  recommendedValue,
  helper,
}: {
  title: string;
  values: readonly T[];
  selected: string;
  onSelect: (value: T) => void;
  recommendedValue?: T;
  helper?: string;
}) {
  return (
    <fieldset>
      <legend className="mb-3 text-[12px] font-medium text-white/52">{title}</legend>
      <div className="flex flex-wrap gap-2">
        {values.map((value) => {
          const isRecommended = value === recommendedValue;
          return (
            <button
              key={value}
              type="button"
              aria-pressed={selected === value}
              onClick={() => onSelect(value)}
              className={cn(
                "relative min-h-12 rounded-xl border px-4 text-[13px] font-medium transition-all duration-200 ease-out focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-white/50 focus-visible:ring-offset-2 focus-visible:ring-offset-[#030303] hover:-translate-y-px hover:shadow-[0_2px_8px_rgba(0,0,0,0.3)] active:scale-95",
                selected === value
                  ? "border-white/28 bg-white/[0.09] text-white shadow-[0_0_0_1px_rgba(59,130,246,0.25)]"
                  : "border-white/[0.09] bg-[#080808] text-white/58 hover:border-white/18 hover:text-white",
              )}
            >
              {value}
              {isRecommended && (
                <span className="absolute -right-1.5 -top-1.5 flex size-3.5 items-center justify-center rounded-full bg-white text-[8px] font-bold text-[#080808]">
                  ✓
                </span>
              )}
            </button>
          );
        })}
      </div>
      {helper && (
        <p className="mt-2 text-[11px] text-white/38">{helper}</p>
      )}
    </fieldset>
  );
}

function StepActions({ onBack, onNext, disabled = false }: { onBack: () => void; onNext: () => void; disabled?: boolean }) {
  return (
    <div className="mt-8 flex flex-col-reverse gap-3 sm:flex-row">
      <SecondaryAction onClick={onBack} icon="back">
        Back
      </SecondaryAction>
      <LiquidButton onClick={onNext} disabled={disabled} className="!min-h-12">
        Continue
      </LiquidButton>
    </div>
  );
}

function SecondaryAction({
  children,
  onClick,
  icon,
}: {
  children: ReactNode;
  onClick: () => void;
  icon?: "back";
}) {
  return (
    <button
      type="button"
      onClick={onClick}
      className="inline-flex min-h-12 items-center justify-center gap-2 rounded-full border border-white/[0.12] bg-transparent px-6 text-[13px] font-medium text-white/65 transition hover:border-white/22 hover:text-white focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-white/30"
    >
      {icon ? <ArrowLeft className="size-4" strokeWidth={1.7} aria-hidden="true" /> : null}
      {children}
    </button>
  );
}