"use client";

import { useEffect, useState } from "react";
import {
  fetchPersonalityDrift,
  listCanonWorks,
  listCharacters,
  proposeEpilogueMilestone,
  setTimeFlow,
  type CanonWork,
  type CharacterSummary,
  type DriftedPersonality,
  type MilestoneProposalResult,
  type TimeFlowMode,
} from "../../lib/api";

const TIME_FLOW_LABELS: Record<TimeFlowMode, string> = {
  FAST: "快轉",
  REALTIME: "現實同步（1:1）",
  SLOW: "放慢",
  FROZEN: "凍結",
};

// N-6 後日談畫面：時間流速切換、人格漂移檢視、里程碑提案——三者都依「推演深淺」（storyOrder）運作，
// 預設值抓作品目前的 anchorStoryOrder，使用者可自行調整。
export function EpilogueView() {
  const [works, setWorks] = useState<CanonWork[]>([]);
  const [workId, setWorkId] = useState("");
  const [work, setWork] = useState<CanonWork | null>(null);
  const [characters, setCharacters] = useState<CharacterSummary[]>([]);
  const [characterId, setCharacterId] = useState("");
  const [storyOrder, setStoryOrder] = useState(0);

  const [timeFlowError, setTimeFlowError] = useState<string | null>(null);
  const [drift, setDrift] = useState<DriftedPersonality | null>(null);
  const [milestoneResult, setMilestoneResult] = useState<MilestoneProposalResult | null>(null);
  const [pending, setPending] = useState(false);

  useEffect(() => {
    void listCanonWorks().then(setWorks);
  }, []);

  useEffect(() => {
    const selected = works.find((w) => w.id === workId) ?? null;
    setWork(selected);
    setStoryOrder(selected?.anchorStoryOrder ?? 0);
    setDrift(null);
    setMilestoneResult(null);
    setTimeFlowError(null);
    if (workId) {
      void listCharacters().then((all) => setCharacters(all.filter((c) => c.workId === workId)));
    } else {
      setCharacters([]);
    }
  }, [workId, works]);

  async function handleSetTimeFlow(mode: TimeFlowMode) {
    if (!workId || pending) return;
    setPending(true);
    setTimeFlowError(null);
    try {
      const updated = await setTimeFlow(workId, mode);
      setWork(updated);
      setWorks((prev) => prev.map((w) => (w.id === updated.id ? updated : w)));
    } catch (err) {
      // N-6 驗收：受限情境要顯示被拒原因，這裡把 setTimeFlow() 丟出的後端 message 原樣呈現。
      setTimeFlowError(err instanceof Error ? err.message : "時間流速設定失敗");
    } finally {
      setPending(false);
    }
  }

  async function handleViewDrift() {
    if (!characterId || pending) return;
    setPending(true);
    try {
      setDrift(await fetchPersonalityDrift(characterId, storyOrder));
    } catch {
      setDrift(null);
    } finally {
      setPending(false);
    }
  }

  async function handleProposeMilestone() {
    if (!characterId || pending) return;
    setPending(true);
    try {
      setMilestoneResult(await proposeEpilogueMilestone(characterId, storyOrder));
    } catch {
      setMilestoneResult(null);
    } finally {
      setPending(false);
    }
  }

  return (
    <div className="flex flex-col gap-4">
      <select
        value={workId}
        onChange={(event) => setWorkId(event.target.value)}
        className="rounded-full border bg-transparent px-3 py-2 text-sm"
        style={{ borderColor: "var(--line)", color: "var(--ink)" }}
      >
        <option value="">選擇作品……</option>
        {works.map((w) => (
          <option key={w.id} value={w.id}>
            {w.title}
          </option>
        ))}
      </select>

      {work && (
        <>
          <section className="flex flex-col gap-2 rounded-2xl border p-4 text-xs" style={{ borderColor: "var(--line)" }}>
            <h2 className="text-sm font-bold" style={{ color: "var(--ink)" }}>
              時間流速
            </h2>
            <p style={{ color: "var(--ink-soft)" }}>
              目前：{TIME_FLOW_LABELS[work.timeFlowMode]}
              {work.inEpilogue ? "．已進入後日談" : "．尚未進入後日談"}
            </p>
            <div className="flex flex-wrap gap-2">
              {(Object.keys(TIME_FLOW_LABELS) as TimeFlowMode[]).map((mode) => (
                <button
                  key={mode}
                  type="button"
                  onClick={() => void handleSetTimeFlow(mode)}
                  disabled={pending}
                  className="rounded-full border px-3 py-1 disabled:opacity-50"
                  style={{
                    borderColor: "var(--line)",
                    background: work.timeFlowMode === mode ? "var(--chip-bg)" : "transparent",
                    color: "var(--ink)",
                  }}
                >
                  {TIME_FLOW_LABELS[mode]}
                </button>
              ))}
            </div>
            {timeFlowError && <p style={{ color: "var(--accent)" }}>{timeFlowError}</p>}
          </section>

          <select
            value={characterId}
            onChange={(event) => {
              setCharacterId(event.target.value);
              setDrift(null);
              setMilestoneResult(null);
            }}
            className="rounded-full border bg-transparent px-3 py-2 text-sm"
            style={{ borderColor: "var(--line)", color: "var(--ink)" }}
          >
            <option value="">選擇角色……</option>
            {characters.map((character) => (
              <option key={character.id} value={character.id}>
                {character.aliases[0]?.formalName ?? character.id}
              </option>
            ))}
          </select>

          {characterId && (
            <>
              <div className="flex items-center gap-2 text-xs">
                <label style={{ color: "var(--ink-soft)" }}>推演深淺（storyOrder，預設抓作品目前的錨定點）</label>
                <input
                  type="number"
                  value={storyOrder}
                  onChange={(event) => setStoryOrder(Number(event.target.value))}
                  className="w-24 rounded-full border bg-transparent px-3 py-1"
                  style={{ borderColor: "var(--line)", color: "var(--ink)" }}
                />
              </div>

              <section className="flex flex-col gap-2 rounded-2xl border p-4 text-xs" style={{ borderColor: "var(--line)" }}>
                <div className="flex items-center justify-between">
                  <h2 className="text-sm font-bold" style={{ color: "var(--ink)" }}>
                    人格漂移
                  </h2>
                  <button
                    type="button"
                    onClick={() => void handleViewDrift()}
                    disabled={pending}
                    className="rounded-full px-3 py-1 font-bold text-white disabled:opacity-50"
                    style={{ background: "var(--accent-bright)" }}
                  >
                    查看
                  </button>
                </div>
                {drift && (
                  <p style={{ color: "var(--ink-soft)" }}>
                    性格核心：{drift.archetype}（不變）．外顯度：{drift.expressiveness.toFixed(2)}（位移
                    {drift.driftAmount >= 0 ? "+" : ""}
                    {drift.driftAmount.toFixed(2)}）．情緒衰減倍率：{drift.emotionHalfLifeMultiplier.toFixed(2)}
                  </p>
                )}
              </section>

              <section className="flex flex-col gap-2 rounded-2xl border p-4 text-xs" style={{ borderColor: "var(--line)" }}>
                <div className="flex items-center justify-between">
                  <h2 className="text-sm font-bold" style={{ color: "var(--ink)" }}>
                    人生里程碑
                  </h2>
                  <button
                    type="button"
                    onClick={() => void handleProposeMilestone()}
                    disabled={pending}
                    className="rounded-full px-3 py-1 font-bold text-white disabled:opacity-50"
                    style={{ background: "var(--accent-bright)" }}
                  >
                    提案
                  </button>
                </div>
                {milestoneResult && (
                  <p style={{ color: milestoneResult.label ? "var(--accent)" : "var(--ink-soft)" }}>
                    {milestoneResult.label
                      ? `提案成功：${milestoneResult.label}`
                      : "此時沒有里程碑可提案（可能離上次太近，或角色目標裡沒有對應的正史伏筆）"}
                  </p>
                )}
              </section>
            </>
          )}
        </>
      )}
    </div>
  );
}