import { useState } from 'react';
import { motion } from 'motion/react';
import { Brain, Check, ChevronDown, Crown, Lock, PartyPopper, Play, Sparkles } from 'lucide-react';
import { api, type HomeNode, type HomeUnit } from '@/api';
import { useAppData } from '@/state/AppData';
import { findContinue, unitColor, unitProgress } from '@/state/curriculum';
import { onWhite } from '@/lib/color';
import { useNav } from '@/nav/Navigator';
import { useAsync } from '@/lib/useAsync';
import { EmptyState, ErrorState, LoadingState, ProgressBar, Screen, ScreenHeader, Sep } from '@/components/ui';
import { iconFor } from '@/components/NodeIcon';
import { toFa } from '@/lib/format';
import { MathText } from '@/lib/MathText';
import { useFirstVisit } from '@/lib/firstVisit';
import { SubjectBar } from '@/components/SubjectBar';

/**
 * تبِ «درس‌ها»: فصل ← جزیره ← درس. فصل‌ها اول بسته‌اند و بالای صفحه یک کارتِ «ادامه بده» هست.
 * بازبودنِ فصل/جزیره در متغیرِ ماژول نگه داشته می‌شود، چون با رفتن به درس و برگشتن صفحه از نو ساخته
 * می‌شود (کلیدِ مسیر در MainApp) و کاربر جایش را گم می‌کرد. با بستنِ اپ پاک می‌شود، عمداً.
 */
const remembered: { unit: string | null; node: string | null } = { unit: null, node: null };

export function LessonsScreen() {
  const { home, homeError, refreshHome, gradeTitle } = useAppData();
  const nav = useNav();
  const units = home?.units ?? [];
  const current = findContinue(home);
  const [openUnit, setOpenUnitState] = useState<string | null>(remembered.unit);
  const [openNode, setOpenNodeState] = useState<string | null>(remembered.node);
  const setOpenUnit = (id: string | null) => { remembered.unit = id; setOpenUnitState(id); };
  const setOpenNode = (id: string | null) => { remembered.node = id; setOpenNodeState(id); };

  const totalNodes = units.reduce((n, u) => n + u.nodes.length, 0);
  const doneNodes = units.reduce((n, u) => n + unitProgress(u).done, 0);

  return (
    <Screen className="bg-page">
      <ScreenHeader
        title="درس‌ها"
        subtitle={<>{gradeTitle && <>{gradeTitle}<Sep /></>}اول بخون، بعد آزمون جزیره رو بده</>}
        color="#2FB36B"
        exact
        mascot={{ mood: 'happy' }}
      >
        {home && totalNodes > 0 && (
          <div className="mt-4">
            <div className="mb-1.5 flex justify-between text-[11px] text-white/85">
              <span>جزیره‌هایی که تموم کردی</span>
              <span>{toFa(doneNodes)} از {toFa(totalNodes)}</span>
            </div>
            <ProgressBar percent={Math.round((doneNodes / totalNodes) * 100)} color="#fff" track="rgba(255,255,255,.25)" height={10} />
          </div>
        )}
      </ScreenHeader>

      <SubjectBar />

      <div className="flex-1 overflow-y-auto px-4 pb-6 pt-4">
        {!home ? (
          homeError ? <ErrorState error={homeError} onRetry={() => void refreshHome()} /> : <LoadingState text="دارم درس‌ها رو میارم…" />
        ) : units.length === 0 ? (
          <EmptyState text="هنوز درسی برای این پایه ثبت نشده" />
        ) : (
          <div className="flex flex-col gap-3">
            {current && current.node.nextLessonId != null && (
              <button
                type="button"
                onClick={() => nav.push({ name: 'lesson', lessonId: current.node.nextLessonId as number, nodeId: current.node.id })}
                className="flex items-center gap-3 rounded-2xl px-4 py-3.5 text-right text-white"
                style={{ backgroundColor: onWhite(unitColor(current.unitIndex)), boxShadow: `0 4px 0 ${onWhite(unitColor(current.unitIndex))}99` }}
              >
                <span className="flex h-11 w-11 flex-shrink-0 items-center justify-center rounded-full bg-white/25">
                  <Play size={20} fill="white" />
                </span>
                <span className="flex-1">
                  <span className="block text-[11px] font-bold text-white/85">ادامه بده از همین‌جا</span>
                  <span className="block text-sm font-black leading-6"><MathText text={current.node.title} /></span>
                </span>
              </button>
            )}

            {units.map((unit, i) => (
              <UnitCard
                key={unit.id}
                index={i}
                unit={unit}
                color={unitColor(i)}
                currentNodeId={current?.node.id ?? null}
                open={openUnit === unit.id}
                onToggle={() => setOpenUnit(openUnit === unit.id ? null : unit.id)}
                openNode={openNode}
                onToggleNode={(id) => setOpenNode(openNode === id ? null : id)}
              />
            ))}

            <button
              type="button"
              onClick={() => nav.switchTab('ask')}
              className="mt-1 flex items-center gap-3 rounded-2xl border border-line bg-white px-4 py-3 text-right"
            >
              <Brain size={22} className="flex-shrink-0 text-violet" />
              <span className="text-sm leading-6 text-body">یه جایی از درس رو نفهمیدی؟ <b className="text-ink">از دستیار بپرس</b></span>
            </button>
          </div>
        )}
      </div>
    </Screen>
  );
}

function UnitCard({
  index, unit, color, currentNodeId, open, onToggle, openNode, onToggleNode,
}: {
  index: number; unit: HomeUnit; color: string; currentNodeId: string | null; open: boolean; onToggle: () => void;
  openNode: string | null; onToggleNode: (id: string) => void;
}) {
  const p = unitProgress(unit);
  const complete = p.total > 0 && p.done === p.total;
  const untouched = unit.nodes.every((n) => n.status === 'locked');
  const Icon = iconFor(unit.nodes[0]?.icon, index);
  const nav = useNav();
  const premium = unit.requiresSubscription;
  const intro = useFirstVisit(`unit-card:${unit.id}`);
  return (
    <motion.div
      initial={intro ? { opacity: 0, y: 12 } : { opacity: 1, y: 0 }}
      animate={{ opacity: 1, y: 0 }}
      transition={{ delay: Math.min(index, 8) * 0.04 }}
      className="overflow-hidden rounded-2xl bg-white"
      style={{ border: `2px solid ${open ? color : '#e9e6f7'}`, boxShadow: open ? `0 4px 0 ${color}40` : '0 2px 0 #e9e6f7' }}
    >
      <button type="button" onClick={premium ? () => nav.push({ name: 'subscription' }) : onToggle} aria-expanded={open} className="flex w-full items-center gap-3 px-3.5 py-3.5 text-right">
        <span
          className="flex h-[52px] w-[52px] flex-shrink-0 items-center justify-center rounded-2xl"
          style={{ backgroundColor: complete ? color : `${color}22`, color: complete ? '#fff' : color, opacity: untouched ? 0.55 : 1 }}
        >
          {complete ? <Check size={26} strokeWidth={3.5} /> : untouched ? <Lock size={22} /> : <Icon size={26} strokeWidth={2.2} />}
        </span>
        <span className="min-w-0 flex-1">
          <span className="block text-[11px] font-bold" style={{ color }}>
            {complete ? <><PartyPopper size={12} className="mb-0.5 ml-1 inline" />تموم شد</> : `${toFa(p.total)} جزیره`}
            {premium && <span className="mr-1.5 inline-flex items-center gap-0.5 rounded-full bg-[#FFF4D6] px-1.5 text-[10px] text-[#A86A00]"><Crown size={10} /> با اشتراک</span>}
          </span>
          <span className="block text-sm font-black leading-6 text-ink"><MathText text={unit.title} /></span>
          <span className="mt-1 flex items-center gap-2">
            <span className="flex-1"><ProgressBar percent={p.percent} color={color} height={6} /></span>
            <span className="text-[11px] text-muted">{toFa(p.done)}/{toFa(p.total)}</span>
          </span>
        </span>
        {premium ? <Crown size={18} className="flex-shrink-0 text-[#E0A200]" /> : <ChevronDown size={18} className={`flex-shrink-0 text-muted transition-transform ${open ? 'rotate-180' : ''}`} />}
      </button>
      {open && !premium && (
        <ul className="flex flex-col gap-1.5 border-t border-line bg-[#fbfaff] px-3 py-3">
          {unit.nodes.map((node, ni) => (
            <NodeRow
              key={node.id}
              num={ni + 1}
              node={node}
              color={color}
              isCurrent={node.id === currentNodeId}
              open={openNode === node.id}
              onToggle={() => onToggleNode(node.id)}
            />
          ))}
        </ul>
      )}
    </motion.div>
  );
}

function NodeRow({
  num, node, color, isCurrent, open, onToggle,
}: { num: number; node: HomeNode; color: string; isCurrent: boolean; open: boolean; onToggle: () => void }) {
  const nav = useNav();
  const locked = node.status === 'locked';
  const done = node.status === 'completed';
  const lessons = useAsync(() => (open && !locked ? api.nodeLessons(node.id) : Promise.resolve(null)), [node.id, open, locked]);
  const playable = new Set(node.lessonIds);
  const list = lessons.data?.lessons.filter((l) => playable.has(Number(l.id))) ?? [];
  const loaded = !lessons.loading && !lessons.error && lessons.data !== null && lessons.data !== undefined;

  return (
    <li className="rounded-xl border bg-white" style={{ borderColor: isCurrent ? color : '#e9e6f7' }}>
      <button
        type="button"
        disabled={locked}
        onClick={onToggle}
        aria-expanded={open}
        className="flex w-full items-center gap-2.5 px-3 py-2.5 text-right disabled:opacity-60"
      >
        <span
          className="flex h-7 w-7 flex-shrink-0 items-center justify-center rounded-full text-xs font-black"
          style={done ? { backgroundColor: '#3E9E73', color: '#fff' } : { backgroundColor: locked ? '#f0eeff' : `${color}22`, color: locked ? '#727299' : color }}
        >
          {done ? <Check size={15} strokeWidth={3.5} /> : locked ? <Lock size={13} /> : toFa(num)}
        </span>
        <span className="min-w-0 flex-1">
          <span className="block text-sm font-bold leading-6 text-ink"><MathText text={node.title} /></span>
          <span className="block text-[11px] text-muted">
            {locked ? 'جزیره قبلی رو تموم کن تا باز بشه' : `${toFa(node.lessonIds.length)} درس`}
          </span>
        </span>
        {isCurrent && !open && (
          <span className="flex-shrink-0 rounded-full px-2 py-0.5 text-[10px] font-black text-white" style={{ backgroundColor: color }}>
            بعدی
          </span>
        )}
        {!locked && <ChevronDown size={16} className={`flex-shrink-0 text-muted transition-transform ${open ? 'rotate-180' : ''}`} />}
      </button>

      {open && !locked && (
        <div className="px-3 pb-3">
          {lessons.error ? (
            <ErrorState error={lessons.error} onRetry={lessons.reload} />
          ) : !loaded ? (
            <div className="flex flex-col gap-1.5" aria-busy="true" aria-label="دارم درس‌ها رو میارم">
              {[0, 1, 2].map((k) => <div key={k} className="h-10 animate-pulse rounded-xl bg-soft" />)}
            </div>
          ) : (
            <>
              <ul className="flex flex-col gap-1.5">
                {list.map((l, li) => (
                  <li key={l.id}>
                    <button
                      type="button"
                      onClick={() => nav.push({ name: 'lesson', lessonId: Number(l.id), nodeId: node.id })}
                      className="flex w-full items-center gap-2.5 rounded-xl bg-[#f7f8ff] px-3 py-2 text-right text-sm active:scale-[.99]"
                    >
                      <span
                        className="flex h-6 w-6 flex-shrink-0 items-center justify-center rounded-full text-[11px] font-black"
                        style={l.done ? { backgroundColor: '#3E9E73', color: '#fff' } : { backgroundColor: '#fff', color: '#727299', border: '1px solid #e9e6f7' }}
                      >
                        {l.done ? <Check size={13} strokeWidth={3.5} /> : toFa(li + 1)}
                      </span>
                      <span className={`flex-1 ${l.done ? 'text-muted' : 'text-ink'}`}><MathText text={l.title} /></span>
                    </button>
                  </li>
                ))}
              </ul>
              <button
                type="button"
                onClick={() => nav.push({ name: 'quiz', nodeId: node.id })}
                className="mt-2.5 flex w-full items-center justify-center gap-2 rounded-xl py-3 text-sm font-black text-white active:translate-y-[2px]"
                style={{ backgroundColor: onWhite(color), boxShadow: `0 3px 0 ${onWhite(color)}99` }}
              >
                {done ? <Sparkles size={15} /> : <Play size={15} fill="white" />}
                {done ? 'دوباره تمرین کن' : 'درس‌ها رو خوندی؟ برو آزمون'}
              </button>
            </>
          )}
        </div>
      )}
    </li>
  );
}