import { useCallback, useEffect, useMemo, useRef, useState } from "react";
import { useParams, useSearchParams } from "react-router-dom";
import { AppShell } from "../components/AppShell";
import { TaskDetail } from "../components/TaskDetail";
import { Check, Inbox, Plus, Search } from "../components/icons";
import {
  Button,
  EmptyState,
  InlineAlert,
  PageHeader,
  PriorityDot,
  SkeletonRows,
  StatusPill,
} from "../components/ui";
import { ApiError, api } from "../lib/client";
import { PRIORITY_LABEL, STATUS_LABEL, parseQuickAdd } from "../lib/parse";
import type { Item, ItemStatus, Page } from "../lib/types";

const VIEWS: { key: string; label: string; hint: string; createAs: ItemStatus }[] = [
  { key: "today", label: "今天", hint: "今天之前到期、还没做完的", createAs: "todo" },
  { key: "active", label: "进行中", hint: "待办 + 进行中 + 被阻塞", createAs: "todo" },
  { key: "inbox", label: "收件箱", hint: "想到还没归类的事", createAs: "inbox" },
  { key: "done", label: "已完成", hint: "最近完成的", createAs: "todo" },
  { key: "all", label: "全部", hint: "含已取消", createAs: "todo" },
];

function dueLabel(iso: string | null): { text: string; overdue: boolean } | null {
  if (!iso) return null;
  const due = new Date(iso);
  const text = due.toLocaleDateString("zh-CN", { month: "numeric", day: "numeric" });
  return { text, overdue: due.getTime() < Date.now() };
}

export function TasksPage() {
  const { wsId = "" } = useParams<{ wsId: string }>();
  const [view, setView] = useState("today");
  const [items, setItems] = useState<Item[]>([]);
  const [cursor, setCursor] = useState<string | null>(null);
  const [hasMore, setHasMore] = useState(false);
  const [query, setQuery] = useState("");
  const [draft, setDraft] = useState("");
  const [loading, setLoading] = useState(false);
  const [error, setError] = useState<string | null>(null);
  // 从通知点进来时带 ?open=<id>，落地即展开那一条
  const [searchParams, setSearchParams] = useSearchParams();
  const [openId, setOpenId] = useState<string | null>(searchParams.get("open"));
  const [activeIdx, setActiveIdx] = useState(0);
  const reqId = useRef(0);

  const current = VIEWS.find((v) => v.key === view);

  const load = useCallback(
    async (nextCursor?: string | null) => {
      if (!wsId) return;
      // 换视图/改搜索词会连发多个请求，慢的那个后到会把新结果覆盖掉。
      // 每次请求记一个号，回来时不是最新号就整包丢弃。
      const mine = ++reqId.current;
      setLoading(true);
      try {
        const params = new URLSearchParams({ view, limit: "30" });
        if (query.trim()) params.set("q", query.trim());
        if (nextCursor) params.set("cursor", nextCursor);
        const page = await api.get<Page<Item>>(`/workspaces/${wsId}/items?${params}`);
        if (mine !== reqId.current) return;
        setItems((prev) => (nextCursor ? [...prev, ...page.items] : page.items));
        setCursor(page.next_cursor);
        setHasMore(page.has_more);
        setError(null);
      } catch (err) {
        if (mine !== reqId.current) return;
        setError(err instanceof ApiError ? err.message : "加载失败");
      } finally {
        if (mine === reqId.current) setLoading(false);
      }
    },
    [wsId, view, query],
  );

  useEffect(() => {
    void load(null);
  }, [load]);

  const activeItem = useMemo(() => items[activeIdx] ?? null, [items, activeIdx]);

  useEffect(() => {
    const onKey = (e: KeyboardEvent) => {
      const target = e.target as HTMLElement;
      const typing =
        ["INPUT", "TEXTAREA", "SELECT"].includes(target.tagName) || target.isContentEditable;
      if (e.key === "Escape") {
        setOpenId(null);
        (target as HTMLInputElement).blur?.();
        return;
      }
      if (typing || items.length === 0) return;

      if (e.key === "j" || e.key === "ArrowDown") {
        e.preventDefault();
        setActiveIdx((i) => Math.min(i + 1, items.length - 1));
      } else if (e.key === "k" || e.key === "ArrowUp") {
        e.preventDefault();
        setActiveIdx((i) => Math.max(i - 1, 0));
      } else if (e.key === "e") {
        if (activeItem) setOpenId(activeItem.id);
      } else if (e.key === "Enter") {
        if (activeItem) void changeStatus(activeItem, activeItem.status === "done" ? "todo" : "done");
      }
    };
    window.addEventListener("keydown", onKey);
    return () => window.removeEventListener("keydown", onKey);
  });

  async function addTask() {
    const raw = draft.trim();
    if (!raw || !wsId || !current) return;
    const parsed = parseQuickAdd(raw, current.createAs);
    try {
      const created = await api.post<Item>(`/workspaces/${wsId}/items`, {
        title: parsed.title,
        status: parsed.status,
        priority: parsed.priority,
        tag_names: parsed.tagNames,
      });
      setDraft("");
      if (view !== "done") setItems((prev) => [created, ...prev]);
    } catch (err) {
      setError(err instanceof ApiError ? err.message : "创建失败");
    }
  }

  async function changeStatus(item: Item, status: ItemStatus) {
    if (!wsId) return;
    try {
      const updated = await api.post<Item>(`/workspaces/${wsId}/items/${item.id}/status`, {
        status,
        version: item.version,
      });
      setItems((prev) => prev.map((it) => (it.id === updated.id ? updated : it)));
    } catch (err) {
      if (err instanceof ApiError && err.code === 4009) {
        setError("这条任务刚被别人改过，已为你刷新");
        void load(null);
        return;
      }
      setError(err instanceof ApiError ? err.message : "状态更新失败");
    }
  }

  return (
    <AppShell wsId={wsId} active="tasks">
      <PageHeader
        title="任务"
        desc={current?.hint}
        eyebrow={<>按 j / k 移动，Enter 完成，e 打开详情</>}
        actions={
          <div className="relative">
            <span className="pointer-events-none absolute left-2.5 top-1/2 -translate-y-1/2 text-ink-400">
              <Search size={14} />
            </span>
            <input
              className="input h-9 w-56 pl-8 text-sm"
              placeholder="搜索标题或正文…"
              value={query}
              onChange={(e) => setQuery(e.target.value)}
            />
          </div>
        }
      />

      <div className="mb-4 flex flex-wrap items-center gap-1.5">
        {VIEWS.map((v) => {
          const active = view === v.key;
          return (
            <button
              key={v.key}
              onClick={() => setView(v.key)}
              className={`rounded-lg px-2.5 py-1.5 text-sm font-medium transition-colors ${
                active
                  ? "bg-white text-ink-900 shadow-sm ring-1 ring-line-200"
                  : "text-ink-500 hover:bg-white/60 hover:text-ink-800"
              }`}
            >
              {v.label}
            </button>
          );
        })}
      </div>

      <div className="card mb-4 overflow-hidden">
        <div className="flex items-center gap-2 px-3 py-2.5">
          <span className="grid h-7 w-7 shrink-0 place-items-center rounded-full border border-dashed border-line-300 text-ink-400">
            <Plus size={14} />
          </span>
          <input
            className="input-flush flex-1"
            placeholder="加一件要做的事，回车创建。支持 #标签 !高"
            value={draft}
            onChange={(e) => setDraft(e.target.value)}
            onKeyDown={(e) => {
              if (e.key === "Enter") void addTask();
            }}
          />
          <Button variant="primary" size="sm" disabled={!draft.trim()} onClick={() => void addTask()}>
            添加
          </Button>
        </div>
      </div>

      {error && (
        <div className="mb-4">
          <InlineAlert>{error}</InlineAlert>
        </div>
      )}

      <div className="card overflow-hidden p-0">
        {loading && items.length === 0 ? (
          <SkeletonRows rows={5} />
        ) : items.length === 0 ? (
          <EmptyState
            icon={<Inbox size={18} />}
            title={view === "today" ? "今天没有到期的事，挺好" : "这里还空着"}
            hint={
              view === "today"
                ? "想提前安排？切到「进行中」，或直接在上面加一件。"
                : "在上面输入一件要做的事，回车就进列表。"
            }
          />
        ) : (
          items.map((item, index) => {
            const due = dueLabel(item.due_at);
            const done = item.status === "done";
            // 收件箱里的东西还没"收下"，不给完成勾选框——先归类，再完成。
            const canComplete = item.status !== "inbox" && item.status !== "canceled";
            return (
              <div
                key={item.id}
                className={`group flex items-start gap-3 border-b border-line-100 px-4 py-3 transition-colors last:border-0 ${
                  index === activeIdx ? "bg-primary-50/45" : "hover:bg-paper-50"
                }`}
                onMouseEnter={() => setActiveIdx(index)}
              >
                {canComplete ? (
                  <button
                    onClick={() => void changeStatus(item, done ? "todo" : "done")}
                    aria-label={done ? "标记未完成" : "标记完成"}
                    className={`mt-0.5 grid h-[18px] w-[18px] shrink-0 place-items-center rounded-full border transition ${
                      done
                        ? "border-sage-500 bg-sage-500 text-white"
                        : "border-line-300 text-transparent hover:border-primary-500 hover:text-primary-500"
                    }`}
                  >
                    <Check size={11} strokeWidth={2.4} />
                  </button>
                ) : (
                  <span
                    className="mt-0.5 h-[18px] w-[18px] shrink-0 rounded-full border border-dashed border-line-300"
                    aria-hidden
                  />
                )}

                {/* 宽屏把元信息推到右侧，一行读完；窄屏仍折到标题下面 */}
                <div className="min-w-0 flex-1 md:flex md:items-center md:gap-3">
                  <button
                    className={`block w-full truncate text-left text-sm transition-colors md:flex-1 ${
                      done ? "text-ink-400 line-through" : "text-ink-900 hover:text-primary-700"
                    }`}
                    onClick={() => setOpenId(item.id)}
                  >
                    {item.title}
                  </button>
                  <div className="mt-1.5 flex flex-wrap items-center gap-1.5 text-2xs md:mt-0 md:shrink-0 md:justify-end">
                    <StatusPill status={item.status} label={STATUS_LABEL[item.status]} />
                    {item.priority > 0 && (
                      <span className="chip">
                        <PriorityDot level={item.priority} />
                        优先级 {PRIORITY_LABEL[item.priority]}
                      </span>
                    )}
                    {due && (
                      <span
                        className={`inline-flex items-center gap-1 rounded-md px-1.5 py-0.5 ${
                          due.overdue && !done
                            ? "bg-rust-50 font-medium text-rust-500"
                            : "text-ink-400"
                        }`}
                      >
                        截止 {due.text}
                        {due.overdue && !done ? "（逾期）" : ""}
                      </span>
                    )}
                    {item.tags.map((tag) => (
                      <span key={tag.id} className="chip text-ink-500">
                        #{tag.name}
                      </span>
                    ))}
                  </div>
                </div>

                <div className="flex shrink-0 gap-1 opacity-0 transition-opacity group-hover:opacity-100 focus-within:opacity-100">
                  {item.status === "inbox" && (
                    <Button variant="ghost" size="sm" onClick={() => void changeStatus(item, "todo")}>
                      收下
                    </Button>
                  )}
                  {(item.status === "todo" || item.status === "blocked") && (
                    <Button variant="ghost" size="sm" onClick={() => void changeStatus(item, "doing")}>
                      开工
                    </Button>
                  )}
                  {item.status === "doing" && (
                    <Button
                      variant="ghost"
                      size="sm"
                      onClick={() => void changeStatus(item, "blocked")}
                    >
                      阻塞
                    </Button>
                  )}
                </div>
              </div>
            );
          })
        )}
      </div>

      {hasMore && (
        <div className="mt-4 text-center">
          <Button variant="ghost" disabled={loading} onClick={() => void load(cursor)}>
            {loading ? "加载中…" : "加载更多"}
          </Button>
        </div>
      )}

      {openId && wsId && (
        <TaskDetail
          wsId={wsId}
          itemId={openId}
          onClose={() => {
            setOpenId(null);
            if (searchParams.get("open")) setSearchParams({}, { replace: true });
          }}
          onChanged={(updated) =>
            setItems((prev) => prev.map((it) => (it.id === updated.id ? updated : it)))
          }
          onDeleted={(id) => setItems((prev) => prev.filter((it) => it.id !== id))}
        />
      )}
    </AppShell>
  );
}