<!--
  Downloads surface (UR-055): two views under /downloads.

  - Downloaded (default): the library filtered to what's on the device, using the
    same browse grids/cards/detail pages as online. Backed by the offline-only
    repository path (never merges server results).
  - Transfers: the in-flight transfer rows (downloading / queued / paused /
    failed / waiting-for-WiFi) with per-row controls. Completed transfers fall
    off this view — they appear in Downloaded.

  Initiating downloads stays on item/album/series detail pages (§7.1); this page
  manages and browses only.

  TRACES: UR-055, UR-056 | DR-081, DR-082, DR-083, DR-084, DR-085
-->
<script lang="ts">
  import { onMount } from "svelte";
  import { goto } from "$app/navigation";
  import { downloads, activeDownloads, pendingDownloads, failedDownloads, waitingForNetwork } from "$lib/stores/downloads";
  import { areDownloadsAllowed } from "$lib/services/networkType";
  import { auth } from "$lib/stores/auth";
  import DownloadItem from "$lib/components/downloads/DownloadItem.svelte";
  import DownloadedBrowse from "$lib/components/downloads/DownloadedBrowse.svelte";

  type ViewType = "downloaded" | "transfers";
  let view = $state<ViewType>("downloaded");
  let loading = $state(true);

  onMount(async () => {
    await loadDownloads();
    // Seed the WiFi-gate state on entry: the 'waitingForNetwork' event only
    // fires when the pump runs, so a queue parked before this page opened would
    // otherwise show no explanation.
    waitingForNetwork.set(!(await areDownloadsAllowed()));
  });

  async function loadDownloads() {
    try {
      loading = true;
      const userId = $auth.user?.id;
      if (userId) {
        await downloads.refresh(userId);
      }
    } catch (error) {
      console.error("Failed to load downloads:", error);
    } finally {
      loading = false;
    }
  }

  // Transfers = everything still in flight or waiting. Completed rows are
  // deliberately excluded — they live in Downloaded, not here.
  const transfers = $derived(
    $activeDownloads.concat($pendingDownloads).concat($failedDownloads)
  );

  async function pauseAll() {
    for (const download of $activeDownloads) {
      if (download.status === "downloading") {
        try {
          await downloads.pause(download.id);
        } catch (error) {
          console.error(`Failed to pause download ${download.id}:`, error);
        }
      }
    }
    const userId = $auth.user?.id;
    if (userId) await downloads.refresh(userId);
  }

  async function resumeAll() {
    for (const download of transfers) {
      if (download.status === "paused" || download.status === "failed") {
        try {
          await downloads.resume(download.id);
        } catch (error) {
          console.error(`Failed to resume download ${download.id}:`, error);
        }
      }
    }
    const userId = $auth.user?.id;
    if (userId) await downloads.refresh(userId);
  }
</script>

<div class="max-w-5xl mx-auto space-y-6 p-6">
  <div class="flex items-center justify-between">
    <div class="flex items-center gap-4">
      <button
        onclick={() => goto("/library")}
        class="p-2 rounded-full hover:bg-white/10 text-gray-400 hover:text-white transition-colors"
        title="Back to library"
      >
        <svg class="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24" stroke-width="2">
          <path stroke-linecap="round" stroke-linejoin="round" d="M15 19l-7-7 7-7" />
        </svg>
      </button>
      <div>
        <h1 class="text-3xl font-bold text-white">Downloads</h1>
        <p class="text-gray-400">Your offline library and active transfers</p>
      </div>
    </div>
  </div>

  <!-- View switch: Downloaded (default) / Transfers -->
  <div class="flex gap-4 border-b border-gray-700">
    <button
      onclick={() => (view = "downloaded")}
      class="pb-3 px-1 font-medium transition-colors relative {view === 'downloaded'
        ? 'text-[var(--color-jellyfin)]'
        : 'text-gray-400 hover:text-white'}"
    >
      Downloaded
      {#if view === "downloaded"}
        <div class="absolute bottom-0 left-0 right-0 h-0.5 bg-[var(--color-jellyfin)]"></div>
      {/if}
    </button>
    <button
      onclick={() => (view = "transfers")}
      class="pb-3 px-1 font-medium transition-colors relative {view === 'transfers'
        ? 'text-[var(--color-jellyfin)]'
        : 'text-gray-400 hover:text-white'}"
    >
      Transfers
      <!-- Draw attention only while transfers are active. -->
      {#if transfers.length > 0}
        <span class="ml-2 px-2 py-0.5 text-xs rounded-full bg-blue-500/20 text-blue-400">
          {transfers.length}
        </span>
      {/if}
      {#if view === "transfers"}
        <div class="absolute bottom-0 left-0 right-0 h-0.5 bg-[var(--color-jellyfin)]"></div>
      {/if}
    </button>
  </div>

  {#if view === "downloaded"}
    <DownloadedBrowse />
  {:else}
    <!-- WiFi-only gate notice (UR-053): explains an otherwise stuck-looking queue -->
    {#if $waitingForNetwork && transfers.length > 0}
      <div class="flex items-start gap-3 rounded-lg border border-amber-700 bg-amber-900/20 p-4" role="status">
        <svg class="mt-0.5 h-5 w-5 shrink-0 text-amber-400" fill="none" stroke="currentColor" viewBox="0 0 24 24" stroke-width="2">
          <path stroke-linecap="round" stroke-linejoin="round" d="M12 18h.01M8.111 15.111a5.5 5.5 0 017.778 0M4.929 11.929a10 10 0 0114.142 0M12 21h.01" />
        </svg>
        <div>
          <p class="font-medium text-amber-200">Waiting for WiFi</p>
          <p class="mt-1 text-sm text-amber-200/80">
            Downloads are paused because “WiFi Only” is enabled and this device is
            on a metered or cellular connection. They'll resume automatically on
            an unmetered network.
          </p>
        </div>
      </div>
    {/if}

    {#if loading}
      <div class="text-center py-12 text-gray-400"><p>Loading transfers…</p></div>
    {:else if transfers.length === 0}
      <div class="rounded-lg border border-gray-700 bg-[var(--color-surface)] p-10 text-center">
        <svg class="mx-auto mb-4 h-14 w-14 text-gray-600" fill="none" stroke="currentColor" viewBox="0 0 24 24" stroke-width="1.4">
          <path stroke-linecap="round" stroke-linejoin="round" d="M5 13l4 4L19 7" />
        </svg>
        <p class="text-lg font-medium text-gray-300">Nothing downloading</p>
        <p class="mt-2 text-sm text-gray-500">
          Browse your library and tap download to save media for offline.
        </p>
        <button
          onclick={() => goto("/library")}
          class="mt-5 rounded-lg bg-[var(--color-jellyfin)] px-4 py-2 text-sm font-medium text-white hover:opacity-90 transition"
        >
          Go to library
        </button>
      </div>
    {:else}
      <div class="flex gap-3">
        <button
          onclick={pauseAll}
          class="px-4 py-2 bg-[var(--color-surface)] text-white rounded-lg font-medium hover:bg-[var(--color-surface-hover)] transition-colors text-sm"
        >
          Pause All
        </button>
        <button
          onclick={resumeAll}
          class="px-4 py-2 bg-[var(--color-surface)] text-white rounded-lg font-medium hover:bg-[var(--color-surface-hover)] transition-colors text-sm"
        >
          Resume All
        </button>
      </div>

      <div class="space-y-3">
        {#each transfers as download (download.id)}
          <DownloadItem {download} />
        {/each}
      </div>
    {/if}
  {/if}
</div>
