'use client';

import { AnimatePresence, motion } from 'motion/react';
import { useRouter } from 'next/navigation';
import { useEffect, useMemo, useRef, useState } from 'react';
import { apiRequest, ensureLogin } from '../lib/api';
import { chooseMatch, createBracket, firstOpenMatch } from '../lib/bracket';
import type { BracketState, ChoiceSide, TestDetail, TestResult } from '../lib/types';

type Mode = 'single' | 'multi' | 'swipe';

const MODES: readonly { id: Mode; label: string }[] = [
  { id: 'single', label: '一对' },
  { id: 'multi', label: '多对' },
  { id: 'swipe', label: '滑动' }
];

export default function TestArena({ slug }: { slug: string }) {
  const router = useRouter();
  const [test, setTest] = useState<TestDetail | null>(null);
  const [bracket, setBracket] = useState<BracketState | null>(null);
  const [mode, setMode] = useState<Mode>('single');
  const [error, setError] = useState('');
  const [saving, setSaving] = useState(false);
  const pointerStart = useRef<number | null>(null);

  useEffect(() => {
    apiRequest<TestDetail>(`/api/v1/tests/${slug}`).then(data => {
      setTest(data);
      setBracket(createBracket(data.candidates));
    }).catch((error: Error) => setError(error.message));
  }, [slug]);

  const total = test ? test.candidates.length - 1 : 1;
  const progress = bracket ? Math.round(bracket.decisions.length / total * 100) : 0;
  const currentIndex = bracket ? firstOpenMatch(bracket) : -1;
  const current = bracket && currentIndex >= 0 ? bracket.matches[currentIndex] : null;
  const visibleMatches = useMemo(() => bracket?.matches.slice(bracket.offset, bracket.offset + 4) || [], [bracket]);

  async function complete(finalState: BracketState) {
    setSaving(true);
    const champion = finalState.pool[0];
    const finalDecision = finalState.decisions.at(-1);
    try {
      await ensureLogin();
      if (!champion || !finalDecision) throw new Error('晋级结果不完整');
      const runnerUp = finalDecision.left_id === champion.id ? finalDecision.right_id : finalDecision.left_id;
      const result = await apiRequest<TestResult>(`/api/v1/tests/${slug}/runs`, {
        method: 'POST',
        body: {
          app_key: 'hub',
          champion_id: champion.id,
          runner_up_id: runnerUp,
          ranking_ids: [champion, ...finalState.eliminated].map(item => item.id),
          decisions: finalState.decisions
        }
      });
      sessionStorage.setItem('pk_last_result', JSON.stringify(result));
      router.replace(`/results/${result.id}`);
    } catch (error) {
      setError(error instanceof Error ? error.message : '保存失败');
      setSaving(false);
    }
  }

  function select(matchIndex: number, side: ChoiceSide) {
    if (saving || !bracket) return;
    const outcome = chooseMatch(bracket, matchIndex, side);
    let next = outcome.state;
    if (!outcome.finished && mode === 'multi') {
      const block = next.matches.slice(next.offset, next.offset + 4);
      if (block.length && block.every(match => match.winner)) next = { ...next, offset: next.offset + 4 };
    }
    setBracket(next);
    if (outcome.finished) complete(next);
  }

  function pointerUp(event: React.PointerEvent<HTMLElement>) {
    if (mode !== 'swipe' || pointerStart.current === null) return;
    const delta = event.clientX - pointerStart.current;
    pointerStart.current = null;
    if (Math.abs(delta) >= 55) select(currentIndex, delta < 0 ? 'left' : 'right');
  }

  if (error) return <main className="arenaState"><h1>暂时无法继续</h1><p>{error}</p><button onClick={() => router.push('/')}>返回首页</button></main>;
  if (!test || !bracket) return <main className="arenaState">正在抽签…</main>;
  if (!current && mode !== 'multi') return <main className="arenaState">正在生成晋级图…</main>;

  return (
    <main className="arenaPage">
      <header className="arenaHeader">
        <button onClick={() => router.push('/')} aria-label="返回">←</button>
        <span>第 {bracket.round} 轮</span>
        <small>{bracket.decisions.length} / {total}</small>
      </header>
      <div className="progressTrack"><i style={{ width: `${progress}%` }} /></div>
      <div className="modeTabs">
        {MODES.map(item => <button key={item.id} className={mode === item.id ? 'active' : ''} onClick={() => setMode(item.id)}>{item.label}</button>)}
      </div>
      {mode === 'multi' ? (
        <section className="multiArena">
          <AnimatePresence mode="popLayout">
            {visibleMatches.map((match, index) => {
              const matchIndex = bracket.offset + index;
              return (
                <motion.article layout key={`${bracket.round}-${matchIndex}`} className={`miniMatch ${match.winner ? 'resolved' : ''}`} initial={{ opacity: 0, scale: .94 }} animate={{ opacity: 1, scale: 1 }} exit={{ opacity: 0, scale: .9 }}>
                  {match.winner ? <motion.strong initial={{ scale: .6 }} animate={{ scale: 1 }}>晋级<br />{match.winner.name}</motion.strong> : <><button onClick={() => select(matchIndex, 'left')}>{match.left.name}</button><span>VS</span><button onClick={() => select(matchIndex, 'right')}>{match.right!.name}</button></>}
                </motion.article>
              );
            })}
          </AnimatePresence>
        </section>
      ) : (
        <section className={`singleArena ${mode === 'swipe' ? 'swipe' : ''}`} onPointerDown={event => { pointerStart.current = event.clientX; }} onPointerUp={pointerUp}>
          <motion.button whileTap={{ scale: .94, rotate: -1 }} onClick={() => mode !== 'swipe' && select(currentIndex, 'left')} className="choiceCard warm"><small>A</small><strong>{current!.left.name}</strong><span>{mode === 'swipe' ? '向左滑选它' : '点按晋级'}</span></motion.button>
          <b className="versus">VS</b>
          <motion.button whileTap={{ scale: .94, rotate: 1 }} onClick={() => mode !== 'swipe' && select(currentIndex, 'right')} className="choiceCard cool"><small>B</small><strong>{current!.right!.name}</strong><span>{mode === 'swipe' ? '向右滑选它' : '点按晋级'}</span></motion.button>
        </section>
      )}
      {saving ? <div className="savingToast">正在保存你的冠军…</div> : null}
    </main>
  );
}