import 'dart:convert';
import 'dart:typed_data';

import 'package:flutter_test/flutter_test.dart';
import 'package:image/image.dart' as img;
import 'package:tane/services/offer_thumbnail.dart';

void main() {
  /// A real, decodable photo far bigger than a thumbnail, with varied pixels so
  /// JPEG can't compress it to nothing.
  Uint8List bigPhoto() {
    final image = img.Image(width: 1280, height: 960);
    for (var y = 0; y < image.height; y++) {
      for (var x = 0; x < image.width; x++) {
        image.setPixelRgb(x, y, (x * 7) % 256, (y * 5) % 256, (x + y) % 256);
      }
    }
    return img.encodeJpg(image, quality: 90);
  }

  test('produces a small jpeg data-URI that fits the byte budget', () {
    final uri = offerThumbnailDataUri(bigPhoto(), maxBytes: 40000);

    expect(uri, isNotNull);
    expect(uri!, startsWith('data:image/jpeg;base64,'));
    final b64 = uri.substring('data:image/jpeg;base64,'.length);
    expect(b64.length, lessThanOrEqualTo(40000));

    // The payload really is a smaller image than the source.
    final decoded = img.decodeJpg(base64.decode(b64))!;
    expect(decoded.width, lessThanOrEqualTo(320));
    expect(decoded.height, lessThanOrEqualTo(320));
  });

  test('never upscales an already-tiny image', () {
    final small = img.encodeJpg(img.Image(width: 64, height: 48), quality: 80);
    final uri = offerThumbnailDataUri(small);

    expect(uri, isNotNull);
    final b64 = uri!.substring('data:image/jpeg;base64,'.length);
    final decoded = img.decodeJpg(base64.decode(b64))!;
    expect(decoded.width, 64);
    expect(decoded.height, 48);
  });

  test('returns null for bytes that are not an image', () {
    expect(offerThumbnailDataUri(Uint8List.fromList([1, 2, 3, 4])), isNull);
  });

  group('decodeDataUri', () {
    test('round-trips a base64 data URI to its bytes', () {
      final bytes = Uint8List.fromList([9, 8, 7, 6]);
      final uri = 'data:image/jpeg;base64,${base64.encode(bytes)}';
      expect(decodeDataUri(uri), bytes);
    });

    test('returns null for a plain http url', () {
      expect(decodeDataUri('https://example.org/a.jpg'), isNull);
    });
  });
}
