<script lang="ts">
  import { onMount } from 'svelte';
  import type { ActivitySummary, BASIndex, Sport } from '../lib/types';
  import { formatDistance, formatDuration, formatElevation, formatDate, sportIcon, sportColor, sportLabel } from '../lib/format';
  import { loadIndex } from '../lib/dataloader';

  /** Render preview_coords as an SVG polyline path string. */
  function trackPath(coords: [number, number][] | null, w: number, h: number): string {
    if (!coords || coords.length < 2) return '';
    const lats = coords.map(c => c[0]);
    const lons = coords.map(c => c[1]);
    const minLat = Math.min(...lats), maxLat = Math.max(...lats);
    const minLon = Math.min(...lons), maxLon = Math.max(...lons);
    const latR = maxLat - minLat || 0.001;
    const lonR = maxLon - minLon || 0.001;
    const pad = 4;
    const scaleX = (w - pad * 2) / lonR;
    const scaleY = (h - pad * 2) / latR;
    const scale = Math.min(scaleX, scaleY);
    const offX = pad + (w - pad * 2 - lonR * scale) / 2;
    const offY = pad + (h - pad * 2 - latR * scale) / 2;
    return coords
      .map(([lat, lon], i) => {
        const x = (lon - minLon) * scale + offX;
        const y = h - ((lat - minLat) * scale + offY); // flip: SVG y↓, lat↑
        return `${i === 0 ? 'M' : 'L'}${x.toFixed(1)},${y.toFixed(1)}`;
      })
      .join(' ');
  }

  const PAGE_SIZE = 60;

  let all: ActivitySummary[] = [];
  let sport: Sport | 'all' = 'all';
  let shown = PAGE_SIZE;
  let loading = true;
  let error = '';
  let mounted = false;

  $: filtered = sport === 'all' ? all : all.filter(a => a.sport === sport);
  $: visible = filtered.slice(0, shown);
  $: hasMore = shown < filtered.length;

  $: if (sport) shown = PAGE_SIZE; // reset pagination on filter change

  $: if (mounted) {
    const params = new URLSearchParams(window.location.search);
    if (sport === 'all') params.delete('sport'); else params.set('sport', sport);
    const qs = params.toString();
    history.replaceState(null, '', qs ? `?${qs}` : window.location.pathname);
  }

  onMount(async () => {
    sport = (new URLSearchParams(window.location.search).get('sport') as Sport | 'all') ?? 'all';
    mounted = true;
    try {
      const index = await loadIndex(import.meta.env.BASE_URL);
      all = index.activities.filter(a => a.privacy !== 'private');
    } catch (e: any) {
      error = e.message;
    } finally {
      loading = false;
    }
  });

  const sports: Array<{ value: Sport | 'all'; label: string }> = [
    { value: 'all',      label: 'All' },
    { value: 'cycling',  label: '🚴 Cycling' },
    { value: 'running',  label: '🏃 Running' },
    { value: 'hiking',   label: '🥾 Hiking' },
    { value: 'walking',  label: '🚶 Walking' },
    { value: 'swimming', label: '🏊 Swimming' },
    { value: 'skiing',   label: '⛷️ Skiing' },
    { value: 'other',    label: '⚡ Other' },
  ];
</script>

<!-- Filter bar -->
<div class="flex gap-2 mb-6 flex-wrap">
  {#each sports as s}
    <button
      class="px-3 py-1 rounded-full text-sm font-medium border transition-colors"
      class:border-zinc-700={sport !== s.value}
      class:text-zinc-400={sport !== s.value}
      class:border-[--accent]={sport === s.value}
      class:text-white={sport === s.value}
      style={sport === s.value ? 'background:var(--accent-dim)' : ''}
      on:click={() => sport = s.value}
    >
      {s.label}
    </button>
  {/each}
  {#if all.length > 0}
    <span class="ml-auto text-sm text-zinc-500 self-center">
      {filtered.length} {filtered.length === 1 ? 'activity' : 'activities'}
    </span>
  {/if}
</div>

{#if loading}
  <div class="grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-3 gap-4">
    {#each Array(12) as _}
      <div class="h-36 rounded-xl bg-zinc-800 animate-pulse"></div>
    {/each}
  </div>
{:else if error}
  <p class="text-red-400 text-center py-12">Could not load activities: {error}</p>
{:else if filtered.length === 0}
  <p class="text-zinc-500 text-center py-12">No activities found.</p>
{:else}
  <div class="grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-3 gap-4">
    {#each visible as a (a.id)}
      <a
        href={`${import.meta.env.BASE_URL}activity/${a.id}/`}
        class="block rounded-xl bg-zinc-900 border border-zinc-800 p-4 hover:border-zinc-600 hover:bg-zinc-800/80 transition-all group"
      >
        <!-- header -->
        <div class="flex items-start justify-between gap-2 mb-3">
          <div class="flex-1 min-w-0">
            <p class="text-xs text-zinc-500 mb-0.5">{formatDate(a.started_at)}</p>
            <h3 class="font-semibold text-white truncate group-hover:text-[--accent] transition-colors">
              {a.title}
            </h3>
          </div>
          <span
            class="text-xs font-medium px-2 py-0.5 rounded-full flex-shrink-0"
            style="background:{sportColor(a.sport)}22; color:{sportColor(a.sport)}"
          >
            {sportIcon(a.sport)} {sportLabel(a.sport, a.sub_sport)}
          </span>
        </div>

        <!-- track thumbnail -->
        {#if a.preview_coords}
          <svg viewBox="0 0 120 70" class="w-full mt-2 mb-3 rounded overflow-hidden bg-zinc-800/60" style="height:70px">
            <path
              d={trackPath(a.preview_coords, 120, 70)}
              fill="none"
              stroke={sportColor(a.sport)}
              stroke-width="1.5"
              stroke-linecap="round"
              stroke-linejoin="round"
              opacity="0.9"
            />
          </svg>
        {/if}

        <!-- stats row -->
        <div class="grid grid-cols-3 gap-2 text-center">
          <div>
            <p class="text-lg font-bold text-white">{formatDistance(a.distance_m)}</p>
            <p class="text-xs text-zinc-500">Distance</p>
          </div>
          <div>
            <p class="text-lg font-bold text-white">{formatDuration(a.moving_time_s ?? a.duration_s)}</p>
            <p class="text-xs text-zinc-500">Moving time</p>
          </div>
          <div>
            <p class="text-lg font-bold text-white">{formatElevation(a.elevation_gain_m)}</p>
            <p class="text-xs text-zinc-500">Elevation</p>
          </div>
        </div>

        <!-- secondary stats -->
        {#if a.avg_speed_kmh || a.avg_hr_bpm}
          <div class="flex gap-4 mt-3 pt-3 border-t border-zinc-800 text-xs text-zinc-400">
            {#if a.avg_speed_kmh}
              <span>⚡ {a.avg_speed_kmh.toFixed(1)} km/h</span>
            {/if}
            {#if a.avg_hr_bpm}
              <span>♥ {a.avg_hr_bpm} bpm</span>
            {/if}
            {#if a.avg_cadence_rpm}
              <span>↻ {a.avg_cadence_rpm} rpm</span>
            {/if}
          </div>
        {/if}
      </a>
    {/each}
  </div>

  {#if hasMore}
    <div class="text-center mt-8">
      <button
        class="px-6 py-2 rounded-full border border-zinc-700 text-zinc-300 hover:border-zinc-500 hover:text-white transition-colors text-sm"
        on:click={() => shown += PAGE_SIZE}
      >
        Load more ({filtered.length - shown} remaining)
      </button>
    </div>
  {/if}
{/if}
