"use client";

import { useEffect, useMemo, useState } from "react";
import { Plus, RotateCcw, Trash2 } from "lucide-react";
import { AdminStepper, AdminSwitch } from "@/components/admin";
import ConfirmDialog from "@/components/ConfirmDialog";
import useUnsavedGuard from "@/hooks/useUnsavedGuard";
import { apiGetSettings, apiUpdateSiteSettings } from "@/lib/api";
import {
  DEFAULT_LEVEL_DEFS,
  LEVEL_BADGE_CLASS,
  LEVEL_COLOR_KEYS,
  LEVEL_COLOR_TOKENS,
  MAX_LEVEL_COUNT,
  splitBackground,
  type LevelDef,
} from "@/lib/levels";
import { toast } from "@/lib/toast";

const cloneDefs = (defs: LevelDef[]): LevelDef[] =>
  defs.map((d) => ({ threshold: d.threshold, color: d.color }));

const sameDefs = (a: LevelDef[] | null, b: LevelDef[] | null) => {
  if (a === b) return true;
  if (!a || !b || a.length !== b.length) return false;
  return a.every((d, i) => d.threshold === b[i].threshold && d.color === b[i].color);
};

/** 等级管理：配置等级数量（2–12）、每级所需累计积分与前景/背景配色、特效开关 */
export default function LevelsAdmin() {
  const [form, setForm] = useState<LevelDef[] | null>(null); // null = 加载中
  const [saved, setSaved] = useState<LevelDef[] | null>(null);
  const [fx, setFx] = useState(true);
  const [savedFx, setSavedFx] = useState(true);
  const [resetOpen, setResetOpen] = useState(false);
  const [saving, setSaving] = useState(false);
  const dirty = useMemo(
    () => !sameDefs(form, saved) || fx !== savedFx,
    [form, saved, fx, savedFx],
  );
  const leave = useUnsavedGuard(dirty);

  useEffect(() => {
    let alive = true;
    apiGetSettings()
      .then((s) => {
        if (!alive) return;
        const defs = cloneDefs(s.levels);
        setForm(defs);
        setSaved(defs);
        setFx(s.levels_fx);
        setSavedFx(s.levels_fx);
      })
      .catch((e) => {
        toast(e instanceof Error ? e.message : "获取等级配置失败");
        if (alive) setForm([]);
      });
    return () => {
      alive = false;
    };
  }, []);

  const setThreshold = (i: number, v: number) =>
    setForm((f) => (f ? f.map((d, j) => (j === i ? { ...d, threshold: v } : d)) : f));
  const setColor = (i: number, color: string) =>
    setForm((f) => (f ? f.map((d, j) => (j === i ? { ...d, color } : d)) : f));
  const addLevel = () =>
    setForm((f) => {
      if (!f || f.length >= MAX_LEVEL_COUNT) return f;
      const last = f[f.length - 1];
      return [...f, { threshold: (last?.threshold ?? 0) + 100, color: "neutral" }];
    });
  const removeLast = () =>
    setForm((f) => (f && f.length > 2 ? f.slice(0, -1) : f));

  const save = async () => {
    if (saving || !dirty || !form) return;
    if (form.length < 2) {
      toast("至少保留 2 个等级");
      return;
    }
    if (form[0].threshold !== 0) {
      toast("Lv.1 所需积分须为 0");
      return;
    }
    for (let i = 1; i < form.length; i++) {
      if (!(form[i].threshold > form[i - 1].threshold)) {
        toast(`Lv.${i + 1} 所需积分须大于上一级`);
        return;
      }
    }
    setSaving(true);
    try {
      const res = await apiUpdateSiteSettings({ levels: form, levels_fx: fx });
      const defs = cloneDefs(res.levels);
      setForm(defs);
      setSaved(defs);
      setSavedFx(fx);
      toast("等级配置已保存", "ok");
    } catch (e) {
      toast(e instanceof Error ? e.message : "保存失败");
    } finally {
      setSaving(false);
    }
  };

  // 重置：仅回填默认等级表（2–12 约束内），需再点保存才生效
  const resetToDefault = () => {
    if (!form) return;
    setForm(cloneDefs(DEFAULT_LEVEL_DEFS));
    setResetOpen(false);
    toast("已恢复默认等级表，点击保存生效", "ok");
  };

  return (
    <div className="admin-settings-stack">
      <div>
        <h2 className="text-lg font-bold" style={{ color: "var(--ink)" }}>
          等级管理
        </h2>
        <p className="meta text-sm mt-1">
          用户等级由累计获得积分决定，达到某级阈值即晋升。可配置等级数量（2–{MAX_LEVEL_COUNT}{" "}
          级）、每级所需积分与配色；等级徽章仅显示 Lv.n，不弹悬浮提示。
        </p>
      </div>

      {!form ? (
        <p className="meta px-1 py-6">加载等级配置…</p>
      ) : form.length === 0 ? (
        <div className="panel text-center py-12">
          <p className="meta">等级配置加载失败，请刷新页面重试。</p>
        </div>
      ) : (
        <div className="panel p-0 overflow-hidden">
          {form.map((d, i) => {
            const n = i + 1;
            const tokens = LEVEL_COLOR_TOKENS[d.color] ?? LEVEL_COLOR_TOKENS.neutral;
            const textBg = splitBackground(tokens.text ?? "none");
            const isLast = i === form.length - 1;
            return (
              <div
                key={n}
                className="flex items-center gap-4 px-4 py-3 flex-wrap"
                style={{ borderTop: i === 0 ? "none" : "1px solid var(--line)" }}
              >
                {/* 预览：与 LevelBadge 同构（外层底色 + .lv-text 文字层），实时反映未保存的修改 */}
                <span className="w-14 shrink-0 flex">
                  <span
                    className={LEVEL_BADGE_CLASS}
                    style={{
                      background: tokens.bg,
                      boxShadow: `inset 0 0 0 1px ${tokens.ring ?? "transparent"}`,
                    }}
                  >
                    <span
                      className="lv-text"
                      style={{
                        backgroundImage: textBg.image,
                        backgroundPosition: textBg.position,
                        backgroundSize: textBg.size,
                        backgroundClip: "text",
                        WebkitBackgroundClip: "text",
                        color: tokens.fg,
                      }}
                    >
                      Lv.{n}
                    </span>
                  </span>
                </span>
                <div className="shrink-0">
                  <p className="text-xs mb-1" style={{ color: "var(--ink-2)" }}>
                    所需累计积分
                  </p>
                  <AdminStepper
                    value={d.threshold}
                    onChange={(v) => setThreshold(i, v)}
                    min={0}
                    max={1000000}
                    unit="分"
                    ariaLabel={`Lv.${n} 所需积分`}
                    disabled={saving || n === 1}
                  />
                </div>
                <div className="min-w-0">
                  <p className="text-xs mb-1.5" style={{ color: "var(--ink-2)" }}>
                    配色（前景/背景）
                  </p>
                  <div className="flex gap-1.5 flex-wrap">
                    {LEVEL_COLOR_KEYS.map((c) => {
                      const t = LEVEL_COLOR_TOKENS[c];
                      const active = d.color === c;
                      return (
                        <button
                          key={c}
                          type="button"
                          aria-label={c}
                          title={c}
                          disabled={saving}
                          onClick={() => setColor(i, c)}
                          className="w-6 h-6 rounded-full transition-transform"
                          style={{
                            background: t.bg,
                            outline: active
                              ? "2px solid var(--ink)"
                              : "1px solid var(--line)",
                            outlineOffset: 1,
                          }}
                        />
                      );
                    })}
                  </div>
                </div>
                <span className="flex-1" />
                {isLast && (
                  <button
                    type="button"
                    className="btn btn-line btn-sm shrink-0"
                    style={{ color: "var(--danger)" }}
                    disabled={saving || form.length <= 2}
                    onClick={removeLast}
                  >
                    <Trash2 size={13} /> 删除此级
                  </button>
                )}
              </div>
            );
          })}
          {/* 添加新等级：整宽虚线条目，与上方项同宽 */}
          {form.length < MAX_LEVEL_COUNT ? (
            <button
              type="button"
              className="w-full flex items-center justify-center gap-1.5 py-3.5 text-sm transition-colors hover:opacity-80"
              style={{
                borderTop: "1.5px dashed var(--line)",
                color: "var(--ink-2)",
              }}
              disabled={saving}
              onClick={addLevel}
            >
              <Plus size={15} /> 添加新等级
            </button>
          ) : (
            <div
              className="w-full flex items-center justify-center py-3.5 text-xs"
              style={{
                borderTop: "1.5px dashed var(--line)",
                color: "var(--ink-3)",
              }}
            >
              已达 {MAX_LEVEL_COUNT} 级上限
            </div>
          )}
        </div>
      )}

      <div className="flex items-center gap-4 flex-wrap">
        <button
          type="button"
          className="btn btn-primary btn-sm"
          disabled={saving || !dirty}
          onClick={() => void save()}
        >
          {saving ? "保存中…" : "保存等级配置"}
        </button>
        <button
          type="button"
          className="btn btn-line btn-sm"
          disabled={saving || !form}
          onClick={() => setResetOpen(true)}
        >
          <RotateCcw size={13} /> 重置
        </button>
        <div className="flex items-center gap-2">
          <AdminSwitch
            checked={fx}
            disabled={saving}
            onChange={() => setFx((v) => !v)}
            label="特效动画"
          />
        </div>
        <span className="admin-settings-instant">
          {dirty
            ? "有未保存的修改"
            : "已保存的配色在页面刷新后生效，等级数值即时按新阈值重算"}
        </span>
      </div>

      <ConfirmDialog
        open={resetOpen}
        title="重置等级配置"
        message={`将恢复为默认 ${DEFAULT_LEVEL_DEFS.length} 级配置（当前修改不会立即生效，需再点击保存）。确定重置？`}
        confirmLabel="重置"
        danger
        onCancel={() => setResetOpen(false)}
        onConfirm={resetToDefault}
      />

      <ConfirmDialog
        open={leave.leaveOpen}
        title="有未保存的修改"
        message="离开后，当前尚未保存的等级配置修改会丢失。确定离开？"
        confirmLabel="离开"
        danger
        onCancel={leave.cancelLeave}
        onConfirm={leave.confirmLeave}
      />
    </div>
  );
}