import { useEffect, useEffectEvent, useLayoutEffect, useRef, useState } from "react";
import { useQueryClient } from "@tanstack/react-query";
import { useTranslation } from "react-i18next";
import clsx from "clsx";
import {
  AlertTriangle,
  CheckCircle2,
  ChevronDown,
  FolderOpen,
  Link,
  Loader2,
  RotateCw,
  X,
} from "lucide-react";
import type { QueueJob } from "../lib/api";
import { quickShareLink } from "../lib/downloads";
import { failCopyKeys, failTitleKey } from "../lib/downloadFailure";
import {
  IN_FLIGHT,
  clearFinished,
  fetchQueue,
  takeUnannounced,
  useFinished,
  useUnannounced,
} from "../lib/downloadQueue";
import { navItemAttrs } from "../lib/listNav";
import { notify } from "../lib/notifications";
import { qk } from "../lib/queryKeys";
import { LS } from "../lib/storage";
import { useLiveQuery } from "../lib/useLiveQuery";
import { usePref } from "../lib/usePref";
import { ErrorModal } from "./downloadModals";
import { jobTitle } from "./downloadTitle";
import { sourceLabel } from "./fileFolders";
import { useFilesActions } from "./filesContext";
import { useDownloadActions } from "./useDownloadActions";
import { type ActionMenuItem } from "./ui/ActionMenu";
import { setCornerLift } from "./ui/backToTopState";
import { Button } from "./ui/Button";
import { ContextMenu } from "./ui/ContextMenu";
import { IconButton } from "./ui/IconButton";
import { menuGroups } from "./ui/menuGroups";
import { MoreButton } from "./ui/MoreButton";
import NavGrid from "./ui/NavGrid";
import { Pressable } from "./ui/Pressable";
import { CONTENT_ID } from "./ui/landmarks";
import { SURFACE } from "./ui/surfaces";
import { useContextMenu } from "./ui/useContextMenu";

// The running downloads, app-wide (DESIGN.md "Running downloads"): a tray in the bottom-right corner,
// up only while something waits, runs or failed — and what finished in this tab, "Done · Open",
// until it is closed. Folds to a pill (remembered per account). A row's right click and "…" are the
// queue's one menu; a finish is announced once with "Copy link" and "Open" (DESIGN.md "Download
// done"). It sits under every dialog and player (z-chrome), so it never covers a player's controls.

type Fold = "open" | "folded";
const parseFold = (v: unknown): Fold => (v === "folded" ? "folded" : "open");
const parseClosed = (v: unknown): string | null => (typeof v === "string" ? v : null);

// Byte progress (a bar with a %) vs ffmpeg's post-steps (a pulse): the queue row's split.
const BYTE_PHASES = ["video", "audio", "editing", "converting"];

const keyOf = (job: QueueJob) => job.id;

function Progress({ job }: { job: QueueJob }) {
  if (job.phase && !BYTE_PHASES.includes(job.phase))
    return (
      <span className="block h-1 overflow-hidden rounded-full bg-fg/10">
        <span className="block h-full w-full animate-pulse bg-accent/60" />
      </span>
    );
  return (
    <span className="flex items-center gap-2 text-xs text-muted">
      <span className="h-1 flex-1 overflow-hidden rounded-full bg-fg/10">
        <span
          className="block h-full rounded-full bg-accent transition-all"
          style={{ width: `${job.progress}%` }}
        />
      </span>
      <span className="w-8 text-right tabular-nums">{job.progress}%</span>
    </span>
  );
}

export default function DownloadTray() {
  const { t } = useTranslation();
  const qc = useQueryClient();
  const { openFile } = useFilesActions();
  const actions = useDownloadActions();

  // Every page polls it now, so the idle cadence is slow: a job started here refetches at once
  // (invalidateDownloads), and one started on another device shows within a minute.
  const queueQ = useLiveQuery(qk.downloads(), fetchQueue, {
    intervalMs: (data) => (data?.some((j) => IN_FLIGHT.has(j.status)) ? 2000 : 60000),
  });
  const finished = useFinished();
  const active = (queueQ.data ?? []).filter((j) => IN_FLIGHT.has(j.status) || j.status === "error");
  const activeIds = new Set(active.map((j) => j.id));
  const rows = [...active, ...finished.filter((j) => !activeIds.has(j.id))];

  // Closed with work still on it, it stays away until that work changes: a new job, or one failing.
  // Remembered (per account) past a reload: an old failure the reader has seen must not reopen it
  // on every page they load.
  const signature = active.map((j) => `${j.id}${j.status === "error" ? "!" : ""}`).join(",");
  const [closedAt, setClosedAt] = usePref<string | null>("downloadTrayClosed", null, {
    localKey: LS.downloadTrayClosed,
    parse: parseClosed,
  });
  // A finish since it was closed is news of its own, whatever else is still on it.
  const shown = rows.length > 0 && (signature !== closedAt || finished.length > 0);
  const [fold, setFold] = usePref<Fold>("downloadTray", "open", {
    localKey: LS.downloadTray,
    parse: parseFold,
  });

  const [errorJob, setErrorJob] = useState<QueueJob | null>(null);
  const menu = useContextMenu<QueueJob>({ keyOf });

  // Folding swaps the control under the keyboard for its counterpart: the focus follows it there
  // (the pill, or the fold button), never left on <body> where the pressed one was.
  const pill = useRef<HTMLButtonElement>(null);
  const foldButton = useRef<HTMLButtonElement>(null);
  const focusNext = useRef<Fold | null>(null);
  const toggleFold = (next: Fold) => {
    focusNext.current = next;
    setFold(next);
  };
  useEffect(() => {
    const target = focusNext.current;
    focusNext.current = null;
    if (target === "folded") pill.current?.focus();
    else if (target === "open") foldButton.current?.focus();
  }, [fold]);

  // --- the done notice ------------------------------------------------------------------------
  const announce = useEffectEvent((job: QueueJob) => {
    const title = jobTitle(job);
    notify({
      level: "success",
      title: t("tray.done.title", { title }),
      message: t(job.asset?.media_kind === "file" ? "tray.done.file" : "tray.done.phone"),
      action: { label: t("tray.done.copyLink"), onClick: () => void quickShareLink(qc, job, t) },
      secondaryAction: {
        label: t("tray.done.open"),
        onClick: () => openFile(job.id, job.folder_id),
      },
    });
  });
  const fresh = useUnannounced();
  useEffect(() => {
    // The take clears them, so a second pass (StrictMode, a re-render) announces nothing again.
    if (fresh.length) takeUnannounced().forEach(announce);
  }, [fresh]);

  // --- Back to top steps up over the tray while it shows -----------------------------------------
  const box = useRef<HTMLDivElement>(null);
  useLayoutEffect(() => {
    const el = box.current;
    if (!el) {
      setCornerLift(0);
      return;
    }
    const measure = () => setCornerLift(el.getBoundingClientRect().height);
    measure();
    const ro = new ResizeObserver(measure);
    ro.observe(el);
    return () => {
      ro.disconnect();
      setCornerLift(0);
    };
  }, [shown, fold]);

  if (!shown)
    return errorJob ? (
      <ErrorModal
        job={errorJob}
        onRetry={() => actions.run(errorJob, "resume")}
        onClose={() => setErrorJob(null)}
      />
    ) : null;

  const counts = {
    running: rows.filter((j) => j.status === "queued" || j.status === "running").length,
    paused: rows.filter((j) => j.status === "paused").length,
    error: rows.filter((j) => j.status === "error").length,
    done: rows.filter((j) => j.status === "done").length,
  };
  const summary = (["running", "paused", "error", "done"] as const)
    .filter((k) => counts[k] > 0)
    .map((k) => t(`tray.count.${k}`, { count: counts[k] }))
    .join(", ");
  const running = rows.filter((j) => j.status === "running");
  const meanProgress = running.length
    ? Math.round(running.reduce((sum, j) => sum + j.progress, 0) / running.length)
    : null;
  const StateIcon = counts.running ? Loader2 : counts.error ? AlertTriangle : CheckCircle2;
  const stateIcon = (
    <StateIcon
      aria-hidden
      className={clsx(
        "size-4 shrink-0",
        counts.running ? "animate-spin text-accent" : counts.error ? "text-danger" : "text-success",
      )}
    />
  );

  const close = () => {
    clearFinished();
    setClosedAt(signature);
    // The tray goes with the button pressed: the keyboard rests on the page (its <main>).
    document.getElementById(CONTENT_ID)?.focus({ preventScroll: true });
  };

  const doneItems = (job: QueueJob): ActionMenuItem[] =>
    menuGroups([
      {
        id: "open",
        label: t("tray.done.open"),
        icon: <FolderOpen className="w-4 h-4" />,
        onSelect: () => openFile(job.id, job.folder_id),
      },
      {
        id: "copyLink",
        label: t("tray.done.copyLink"),
        icon: <Link className="w-4 h-4" />,
        onSelect: () => void quickShareLink(qc, job, t),
      },
    ]);
  const menuItems = menu.target
    ? menu.target.status === "done"
      ? doneItems(menu.target)
      : actions.items(menu.target)
    : [];

  return (
    <div
      ref={box}
      role="region"
      aria-label={t("tray.label")}
      className="absolute right-4 bottom-4 z-chrome flex max-w-[calc(100%-2rem)] flex-col items-end"
    >
      {fold === "folded" ? (
        <Pressable
          ref={pill}
          onClick={() => toggleFold("open")}
          aria-expanded={false}
          title={t("tray.unfold")}
          className={clsx(
            SURFACE.floating,
            "inline-flex items-center gap-2 px-3 py-1.5 text-sm glass-hover",
          )}
        >
          {stateIcon}
          <span className="truncate">{summary}</span>
          {meanProgress !== null && (
            <span className="h-1 w-16 shrink-0 overflow-hidden rounded-full bg-fg/10">
              <span
                className="block h-full rounded-full bg-accent"
                style={{ width: `${meanProgress}%` }}
              />
            </span>
          )}
        </Pressable>
      ) : (
        <div
          className={clsx(
            SURFACE.popover,
            "@container/tray w-80 max-w-full overflow-hidden shadow-float",
          )}
        >
          <div className="flex items-center gap-2 border-b border-border/60 py-1 pr-1 pl-3">
            {stateIcon}
            <span className="min-w-0 flex-1 truncate text-sm font-semibold">
              {/* A phone's narrow tray keeps the news and drops the name (the region names it). */}
              <span className="@max-[18rem]/tray:hidden">{t("tray.title")} · </span>
              {summary}
            </span>
            <IconButton
              ref={foldButton}
              label={t("tray.fold")}
              size="sm"
              variant="ghost"
              aria-expanded
              onClick={() => toggleFold("folded")}
            >
              <ChevronDown />
            </IconButton>
            <IconButton label={t("tray.close")} size="sm" variant="ghost" onClick={close}>
              <X />
            </IconButton>
          </div>
          <NavGrid className="max-h-[50dvh] overflow-y-auto py-1">
            {rows.map((job, i) => {
              const title = jobTitle(job);
              const mine = menu.open && menu.target?.id === job.id;
              return (
                <div
                  key={job.id}
                  {...navItemAttrs(i, title)}
                  {...menu.triggerProps(job)}
                  data-job-id={job.id}
                  className="group flex items-start gap-1 px-3 py-2 focus-visible:bg-fg/5"
                >
                  <div className="flex min-w-0 flex-1 flex-col gap-1">
                    <span className="flex min-w-0 items-center gap-2">
                      <span className="min-w-0 flex-1 truncate text-sm" title={title}>
                        {title}
                      </span>
                      <span className="shrink-0 text-xs text-muted">
                        {sourceLabel(job.source_key, t)}
                      </span>
                    </span>
                    <RowState
                      job={job}
                      onShowError={() => setErrorJob(job)}
                      onRetry={() => actions.run(job, "resume")}
                      onOpen={() => openFile(job.id, job.folder_id)}
                    />
                  </div>
                  <MoreButton
                    label={t("tray.rowMenu")}
                    size="sm"
                    expanded={mine}
                    menuProps={menu.buttonProps(job)}
                    className={mine ? undefined : "reveal"}
                  />
                </div>
              );
            })}
          </NavGrid>
        </div>
      )}
      <ContextMenu menu={menu} ariaLabel={t("tray.rowMenu")} items={menuItems} />
      {errorJob && (
        <ErrorModal
          job={errorJob}
          onRetry={() => actions.run(errorJob, "resume")}
          onClose={() => setErrorJob(null)}
        />
      )}
    </div>
  );
}

/** What a tray row says under its title: how far it is, that it waits, why it failed, or that it is
 *  done — with the one thing to do about it in reach. */
function RowState({
  job,
  onShowError,
  onRetry,
  onOpen,
}: {
  job: QueueJob;
  onShowError: () => void;
  onRetry: () => void;
  onOpen: () => void;
}) {
  const { t } = useTranslation();
  if (job.status === "running") return <Progress job={job} />;
  if (job.status === "error")
    return (
      <span className="flex items-center gap-2 text-xs">
        <AlertTriangle aria-hidden className="size-3.5 shrink-0 text-danger" />
        <Pressable
          onClick={onShowError}
          title={t(failTitleKey(job))}
          className="min-w-0 flex-1 truncate text-left text-danger hover:underline"
        >
          {t(failCopyKeys(job, "short"))}
        </Pressable>
        <Button
          variant="link"
          size="none"
          icon={<RotateCw className="size-3" />}
          onClick={onRetry}
          className="text-xs"
        >
          {t("downloads.actions.retry")}
        </Button>
      </span>
    );
  if (job.status === "done")
    return (
      <span className="flex items-center gap-2 text-xs">
        <CheckCircle2 aria-hidden className="size-3.5 shrink-0 text-success" />
        <span className="flex-1 text-success">{t("tray.done.label")}</span>
        <Button variant="link" size="none" onClick={onOpen} data-nav-open="" className="text-xs">
          {t("tray.done.open")}
        </Button>
      </span>
    );
  return <span className="text-xs text-muted">{t(`downloads.status.${job.status}`)}</span>;
}