import { lazy, Suspense, useCallback, useEffect, useRef, useState } from "react";
import { del, get, post, put } from "../api";
import { confirmDialog, toast } from "../dialogs";
import { useT } from "../i18n";
import { Icon } from "./Icon";
import type { TermInfo } from "./Terminal";

// xterm and the editor are large: load them only when such a tab is shown.
const TermView = lazy(() => import("./Terminal").then((m) => ({ default: m.TermView })));
const Files = lazy(() => import("./Files").then((m) => ({ default: m.Files })));

const POLL_MS = 15_000;
const tabKey = (sessionId: string) => `codecraft.chatTab.${sessionId}`;

/** A file manager tab (stored per user and chat on the server). */
interface FileTab {
  id: string;
  dir: string;
}

/**
 * Tabs of a chat: the chat itself, its terminals and file managers. Both are kept on the
 * server, so they show up again after a reload or on another device (the list is
 * refreshed periodically); which tab is active is per browser tab.
 */
export function useChatTabs(sessionId: string, cwd: string) {
  const t = useT();
  const [terms, setTerms] = useState<TermInfo[]>([]);
  const [files, setFilesState] = useState<FileTab[]>([]);
  // Local file tab changes not yet saved: polling must not undo them.
  const pending = useRef<ReturnType<typeof setTimeout> | undefined>(undefined);
  const [tab, setTabState] = useState<string>(() => sessionStorage.getItem(tabKey(sessionId)) ?? "chat");

  const setTab = useCallback(
    (v: string) => {
      setTabState(v);
      sessionStorage.setItem(tabKey(sessionId), v);
    },
    [sessionId],
  );
  const setFiles = useCallback(
    (update: (f: FileTab[]) => FileTab[], delay = 0) =>
      setFilesState((cur) => {
        const next = update(cur);
        clearTimeout(pending.current);
        pending.current = setTimeout(() => {
          pending.current = undefined;
          void put(`/sessions/${sessionId}/tabs`, next).catch((e) => toast(e));
        }, delay);
        return next;
      }),
    [sessionId],
  );

  const reload = useCallback(
    () =>
      get<{ terminals: TermInfo[]; files: FileTab[] }>(`/sessions/${sessionId}/tabs`)
        .then((r) => {
          setTerms(r.terminals);
          if (!pending.current) setFilesState(r.files);
        })
        .catch(() => undefined),
    [sessionId],
  );

  useEffect(() => {
    setTabState(sessionStorage.getItem(tabKey(sessionId)) ?? "chat");
    setFilesState([]);
    setTerms([]);
    void reload();
    const id = setInterval(reload, POLL_MS);
    const onFocus = () => void reload();
    window.addEventListener("focus", onFocus);
    return () => {
      clearInterval(id);
      window.removeEventListener("focus", onFocus);
    };
  }, [sessionId, reload]);

  // A tab closed elsewhere (or a stale stored tab) falls back to the chat.
  const activeTerm = terms.find((x) => x.id === tab);
  const activeFiles = files.find((f) => f.id === tab);
  const current = activeTerm || activeFiles ? tab : "chat";

  const openTerminal = async () => {
    try {
      const info = await post<TermInfo>("/terminals", { session_id: sessionId, cols: 100, rows: 30 });
      await reload();
      setTab(info.id);
    } catch (e) {
      toast(e);
    }
  };

  const closeTerminal = async (x: TermInfo, n: number) => {
    if (x.alive && !(await confirmDialog({ message: t("terminal.closeConfirm", { name: t("terminal.tab", { n }) }), danger: true, confirmLabel: t("terminal.close") }))) return;
    await del(`/terminals/${x.id}`).catch(() => undefined);
    if (tab === x.id) setTab("chat");
    await reload();
  };

  const openFiles = () => {
    const id = `files:${Date.now().toString(36)}`;
    setFiles((f) => [...f, { id, dir: cwd }]);
    setTab(id);
  };

  const closeFiles = (id: string) => {
    setFiles((f) => f.filter((x) => x.id !== id));
    if (tab === id) setTab("chat");
  };

  // Browsing saves the folder after a short pause, not on every click.
  const fileDirChanged = useCallback((id: string, dir: string) => setFiles((f) => f.map((x) => (x.id === id ? { ...x, dir } : x)), 1000), [setFiles]);

  return { terms, files, tab: current, activeTerm, setTab, openTerminal, closeTerminal, openFiles, closeFiles, fileDirChanged };
}

type Tabs = ReturnType<typeof useChatTabs>;

const basename = (p: string) => p.split("/").filter(Boolean).pop() ?? "/";

/** Tab strip above the chat: the chat, one tab per terminal and file manager, and "+". */
export function ChatTabBar({ state }: { state: Tabs }) {
  const t = useT();
  const { terms, files, tab, setTab, openTerminal, closeTerminal, openFiles, closeFiles } = state;
  if (terms.length === 0 && files.length === 0) return null;
  return (
    <div className="chat-tabs" role="tablist">
      <button role="tab" aria-selected={tab === "chat"} className={`chat-tab ${tab === "chat" ? "active" : ""}`} onClick={() => setTab("chat")}>
        <Icon name="sparkle" /> {t("terminal.chatTab")}
      </button>
      {terms.map((x, i) => (
        <span key={x.id} className={`chat-tab ${tab === x.id ? "active" : ""} ${x.alive ? "" : "dead"}`}>
          <button role="tab" aria-selected={tab === x.id} className="ghost" onClick={() => setTab(x.id)} title={x.cwd}>
            <Icon name="terminal" /> {t("terminal.tab", { n: i + 1 })}
          </button>
          <button className="ghost close" onClick={() => void closeTerminal(x, i + 1)} aria-label={t("terminal.close")} title={t("terminal.close")}>
            <Icon name="close" size={12} />
          </button>
        </span>
      ))}
      {files.map((f) => (
        <span key={f.id} className={`chat-tab ${tab === f.id ? "active" : ""}`}>
          <button role="tab" aria-selected={tab === f.id} className="ghost" onClick={() => setTab(f.id)} title={f.dir}>
            <Icon name="folder" /> {basename(f.dir)}
          </button>
          <button className="ghost close" onClick={() => closeFiles(f.id)} aria-label={t("files.closeTab")} title={t("files.closeTab")}>
            <Icon name="close" size={12} />
          </button>
        </span>
      ))}
      <button className="ghost chat-tab-add" onClick={() => void openTerminal()} title={t("terminal.new")} aria-label={t("terminal.new")}>
        <Icon name="plus" /> <Icon name="terminal" />
      </button>
      <button className="ghost chat-tab-add" onClick={openFiles} title={t("files.newTab")} aria-label={t("files.newTab")}>
        <Icon name="plus" /> <Icon name="folder" />
      </button>
    </div>
  );
}

/**
 * Tab contents besides the chat. The active terminal is mounted (it re-attaches and
 * replays its output); file managers stay mounted while hidden, so unsaved edits survive.
 */
export function ChatTabPanes({ state }: { state: Tabs }) {
  const t = useT();
  const { tab, activeTerm, files, fileDirChanged } = state;
  return (
    <Suspense fallback={<div className="empty">{t("common.loading")}</div>}>
      {activeTerm && <TermView key={activeTerm.id} info={activeTerm} />}
      {files.map((f) => (
        <div key={f.id} className="chat-pane chat-files" hidden={tab !== f.id}>
          <Files embed={{ startDir: f.dir, onDirChange: (d) => fileDirChanged(f.id, d) }} />
        </div>
      ))}
    </Suspense>
  );
}