import { useEffect, useRef, useState } from "react";
import { toast } from "sonner";
import { postSpotifyDownload, type InputType } from "../endpoints/spotify-download_POST.schema";
import {
  getSpotifyDownloadStatus,
  spotifyDownloadFileUrl,
} from "../endpoints/spotify-download-status_GET.schema";
import { getSpotifySession } from "../endpoints/spotify-session_GET.schema";
import { getDesktopBridge } from "./desktopBridge";

const POLL_INTERVAL_MS = 1500;

let canDownloadPromise: Promise<boolean> | undefined;
function loadCanDownload() {
  canDownloadPromise ??= getSpotifySession()
    .then((session) => {
      const allowed = Boolean(session.connected && session.canDownload);
      if (!allowed) canDownloadPromise = undefined;
      return allowed;
    })
    .catch(() => {
      canDownloadPromise = undefined;
      return false;
    });
  return canDownloadPromise;
}

function saveFromServer(jobId: string) {
  const anchor = document.createElement("a");
  anchor.href = spotifyDownloadFileUrl(jobId);
  anchor.rel = "noopener";
  document.body.appendChild(anchor);
  anchor.click();
  anchor.remove();
}

export function useSpotifyDownload() {
  const [busyKeys, setBusyKeys] = useState<Set<string>>(new Set());
  const [canDownload, setCanDownload] = useState(false);
  const mounted = useRef(true);

  useEffect(() => {
    mounted.current = true;
    loadCanDownload().then((allowed) => {
      if (mounted.current) setCanDownload(allowed);
    });
    return () => {
      mounted.current = false;
    };
  }, []);

  function setBusy(key: string, busy: boolean) {
    setBusyKeys((current) => {
      const next = new Set(current);
      if (busy) next.add(key);
      else next.delete(key);
      return next;
    });
  }

  async function startDownload(key: string, label: string, request: InputType) {
    if (busyKeys.has(key)) return;
    setBusy(key, true);
    const toastId = toast.loading(`Preparing ${label}…`);
    try {
      const { jobId } = await postSpotifyDownload(request);
      while (mounted.current) {
        await new Promise((resolve) => window.setTimeout(resolve, POLL_INTERVAL_MS));
        const status = await getSpotifyDownloadStatus(jobId);
        if (status.status === "failed") throw new Error(status.error || "Download failed.");
        if (status.status === "ready") {
          const skipped = status.failed ? ` (${status.failed} track${status.failed === 1 ? "" : "s"} could not be found)` : "";
          const desktop = getDesktopBridge();
          if (desktop && status.savedPath) {
            const savedPath = status.savedPath;
            toast.success(`Saved ${label}${skipped}`, {
              id: toastId,
              description: savedPath,
              action: { label: "Show in folder", onClick: () => desktop.showInFolder(savedPath) },
            });
          } else {
            saveFromServer(jobId);
            toast.success(`Downloading ${status.fileName}${skipped}`, { id: toastId, description: undefined });
          }
          return;
        }
        if (status.total > 1) {
          toast.loading(`Downloading ${label}: ${status.done} of ${status.total}`, {
            id: toastId,
            description: status.currentTitle,
          });
        }
      }
      toast.dismiss(toastId);
    } catch (reason) {
      toast.error(reason instanceof Error ? reason.message : "Download failed.", { id: toastId });
    } finally {
      if (mounted.current) setBusy(key, false);
    }
  }

  return { busyKeys, canDownload, startDownload };
}