samplez/rippr-flutter-src/test/tile_downloader_test.dart

import 'dart:io';
import 'dart:typed_data';

import 'package:flutter_test/flutter_test.dart';
import 'package:rippr/src/tiles/tile_cache.dart';
import 'package:rippr/src/tiles/tile_downloader.dart';
import 'package:rippr/src/tiles/tile_math.dart';

void main() {
  late Directory tempDir;
  late FileTileCache cache;

  setUp(() async {
    tempDir = await Directory.systemTemp.createTemp('rippr_tile_downloader_test_');
    cache = FileTileCache(directory: tempDir, maxBytes: 1024 * 1024);
  });

  tearDown(() async {
    if (tempDir.existsSync()) tempDir.deleteSync(recursive: true);
  });

  List<TileKey> tiles(int n) => [for (var i = 0; i < n; i++) TileKey(1, i, 0)];

  test('every tile is fetched exactly once and lands in the cache', () async {
    final fetched = <TileKey>[];
    final progress = await downloadTiles(
      tiles: tiles(5),
      cache: cache,
      fetchTile: (key) async {
        fetched.add(key);
        return Uint8List.fromList([1, 2, 3]);
      },
      delay: Duration.zero,
    ).toList();

    expect(fetched, tiles(5), reason: 'sequential, in order, no duplicates');
    expect(progress.last, isA<DownloadProgress>());
    expect(progress.last.completed, 5);
    expect(progress.last.isDone, isTrue);
    for (final t in tiles(5)) {
      expect(await cache.get(t), isNotNull);
    }
  });

  test('one failing tile does not abort the rest', () async {
    final progress = await downloadTiles(
      tiles: tiles(4),
      cache: cache,
      fetchTile: (key) async {
        if (key.x == 1) throw Exception('transient');
        return Uint8List.fromList([1]);
      },
      delay: Duration.zero,
    ).toList();

    expect(progress.last.completed, 3);
    expect(progress.last.failed, 1);
    expect(progress.last.isDone, isTrue);
    expect(await cache.get(const TileKey(1, 1, 0)), isNull);
    expect(await cache.get(const TileKey(1, 0, 0)), isNotNull);
    expect(await cache.get(const TileKey(1, 2, 0)), isNotNull);
  });

  test('cancelling mid-download keeps everything already fetched', () async {
    final token = CancelToken();
    final events = <DownloadProgress>[];

    await for (final p in downloadTiles(
      tiles: tiles(10),
      cache: cache,
      fetchTile: (key) async => Uint8List.fromList([1]),
      cancelToken: token,
      delay: Duration.zero,
    )) {
      events.add(p);
      if (p.completed == 3) token.cancel();
    }

    final last = events.last;
    expect(last.isDone, isFalse,
        reason: 'stopped early -- fewer tiles than the total were fetched');
    expect(last.completed, lessThan(10));

    // Everything fetched before cancellation must still be in the cache -- a
    // consistent partial cache, not rolled back to nothing.
    for (var i = 0; i < last.completed; i++) {
      expect(await cache.get(TileKey(1, i, 0)), isNotNull);
    }
  });

  test('an empty tile list completes immediately with no fetch calls', () async {
    var calls = 0;
    final progress = await downloadTiles(
      tiles: const [],
      cache: cache,
      fetchTile: (key) async {
        calls++;
        return Uint8List(0);
      },
    ).toList();

    expect(calls, 0);
    expect(progress.last.isDone, isTrue);
    expect(progress.last.total, 0);
  });
}