import { useEffect, useState } from "react";
import { Link, useNavigate } from "react-router-dom";
import { FontAwesomeIcon } from "@fortawesome/react-fontawesome";
import {
  faArrowLeft,
  faCheckCircle,
  faExclamationTriangle,
  faCircleNotch,
  faPlug,
  faTrashAlt,
  faServer,
} from "@fortawesome/free-solid-svg-icons";
import { useToast } from "../lib/toast";
import { getServerStatus, type ServerStatus } from "../lib/llm";
import { clearHistory } from "../lib/history";
import { useI18n } from "../lib/i18n";

const DRAFT_KEY = "melodymuse-draft";

interface LocalDataSummary {
  hasDraft: boolean;
}

function readLocalDataSummary(): LocalDataSummary {
  if (typeof window === "undefined") {
    return { hasDraft: false };
  }
  const hasDraft = window.localStorage.getItem(DRAFT_KEY) !== null;
  return { hasDraft };
}

export function SettingsPage() {
  const toast = useToast();
  const navigate = useNavigate();
  const { t } = useI18n();

  const [status, setStatus] = useState<ServerStatus | null>(null);
  const [statusError, setStatusError] = useState<string | null>(null);
  const [checking, setChecking] = useState(true);
  const [summary, setSummary] = useState<LocalDataSummary>({
    hasDraft: false,
  });

  const check = async (signal?: AbortSignal) => {
    setChecking(true);
    setStatusError(null);
    try {
      const s = await getServerStatus(signal);
      setStatus(s);
    } catch (err) {
      setStatusError(err instanceof Error ? err.message : t.unreachable);
      setStatus(null);
    } finally {
      setChecking(false);
    }
  };

  useEffect(() => {
    const ctrl = new AbortController();
    check(ctrl.signal);
    setSummary(readLocalDataSummary());
    return () => ctrl.abort();
  }, []);

  const onClearHistory = async () => {
    if (!window.confirm(t.clearHistoryConfirm)) return;
    await clearHistory();
    toast.info(t.clearHistory);
  };

  const onClearDraft = () => {
    if (!summary.hasDraft) return;
    if (!window.confirm(t.clearDraftConfirm)) return;
    window.localStorage.removeItem(DRAFT_KEY);
    setSummary((s) => ({ ...s, hasDraft: false }));
    toast.info(t.clearDraft);
  };

  return (
    <div className="min-h-screen">
      <header className="sticky top-0 z-20 bg-bg/70 backdrop-blur border-b border-border">
        <div className="max-w-md mx-auto px-4 h-14 flex items-center gap-2">
          <button
            type="button"
            onClick={() => navigate("/")}
            className="p-2 -ml-2 rounded-md text-fg-muted hover:text-fg hover:bg-bg-hover transition-colors"
            aria-label="Back"
          >
            <FontAwesomeIcon icon={faArrowLeft} className="w-4 h-4" />
          </button>
          <h1 className="text-sm font-semibold text-fg">{t.settings}</h1>
        </div>
      </header>

      <main className="max-w-md mx-auto px-4 mt-16">
        <div className="card p-6 space-y-6">
          <section>
            <h2 className="text-sm font-semibold text-fg mb-3 flex items-center gap-2">
              <FontAwesomeIcon icon={faServer} className="w-4 h-4 text-accent-primary" />
              {t.serverStatus}
            </h2>

            <div className="space-y-3">
              <div className="flex items-center justify-between gap-3 p-3 rounded-lg border border-border bg-bg-card/40">
                <div className="flex items-center gap-3 min-w-0">
                  <StatusDot checking={checking} ok={Boolean(status)} />
                  <div className="min-w-0">
                    <p className="text-sm font-medium text-fg">
                      {checking
                        ? t.checking
                        : status
                          ? t.connected
                          : statusError
                            ? t.unreachable
                            : "Unknown"}
                    </p>
                    {status && (
                      <p className="text-xs text-fg-muted truncate mt-1">
                        {t.model}: <span className="font-mono">{status.model}</span>
                        <br />
                        {t.endpoint}:{" "}
                        <span className="font-mono">{status.endpoint}</span>
                      </p>
                    )}
                    {statusError && !checking && (
                      <p className="text-xs text-rose-400 break-words mt-1">
                        {statusError}
                      </p>
                    )}
                  </div>
                </div>
                <button
                  type="button"
                  onClick={() => check()}
                  disabled={checking}
                  className="btn-ghost"
                >
                  {checking ? (
                     <FontAwesomeIcon icon={faCircleNotch} spin className="w-4 h-4" />
                  ) : (
                    <FontAwesomeIcon icon={faPlug} className="w-4 h-4" />
                  )}
                  <span>{t.recheck}</span>
                </button>
              </div>
            </div>
          </section>

          <hr className="border-border" />

          <section>
            <h2 className="text-sm font-semibold text-fg mb-3">{t.localData}</h2>
            <ul className="text-xs text-fg-muted space-y-1 mb-4">
              <li>
                <code className="font-mono text-accent-primary">melodymuse-draft</code> —{" "}
                {summary.hasDraft ? t.draftSaved : t.draftEmpty}
              </li>
            </ul>
            <div className="flex flex-col gap-2">
              <button
                type="button"
                onClick={onClearDraft}
                disabled={!summary.hasDraft}
                className="btn-secondary"
              >
                <FontAwesomeIcon icon={faTrashAlt} className="w-4 h-4" />
                {t.clearDraft}
              </button>
              <button
                type="button"
                onClick={onClearHistory}
                className="btn-secondary text-rose-400 hover:text-rose-300 border-rose-400/20"
              >
                <FontAwesomeIcon icon={faTrashAlt} className="w-4 h-4" />
                {t.clearHistory}
              </button>
            </div>
          </section>

          <div className="text-center pt-2">
            <Link
              to="/"
              className="text-xs font-semibold text-fg-muted hover:text-accent-primary transition-colors flex items-center justify-center gap-2"
            >
              <FontAwesomeIcon icon={faArrowLeft} /> {t.backToGenerator}
            </Link>
          </div>
        </div>
      </main>
    </div>
  );
}

function StatusDot({ checking, ok }: { checking: boolean; ok: boolean }) {
  if (checking)
    return <FontAwesomeIcon icon={faCircleNotch} spin className="w-5 h-5 text-fg-muted shrink-0" />;
  if (ok) return <FontAwesomeIcon icon={faCheckCircle} className="w-5 h-5 text-emerald-400 shrink-0" />;
  return <FontAwesomeIcon icon={faExclamationTriangle} className="w-5 h-5 text-rose-400 shrink-0" />;
}