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

import 'package:flutter_test/flutter_test.dart';
import 'package:halkyon_learn_flutter/src/feature/pdf_source/data/pdf_engine.dart';
import 'package:halkyon_learn_flutter/src/feature/pdf_source/data/pdfrx_engine.dart';
import 'package:integration_test/integration_test.dart';
import 'package:material_ui/material_ui.dart';

// The app's PDF engine for real, PDFium included, which `flutter test`
// can't load: on a device or the desktop,
//
//   flutter test integration_test/pdf_engine_test.dart -d linux
//
// on a PDF of three pages, "Hello page N" on each, with an outline of two
// chapters.
void main() {
  IntegrationTestWidgetsFlutterBinding.ensureInitialized();

  setUpAll(PdfrxEngine.initialize);

  testWidgets('opens a PDF, reads its chapters and draws a region', (
    tester,
  ) async {
    final document = await tester.runAsync(
      () => PdfrxEngine().open(_threePages()),
    );
    addTearDown(() => tester.runAsync(document!.dispose));

    expect(document!.pageCount, 3);
    expect(await tester.runAsync(document.chapters), [
      (title: 'One', page: 1),
      (title: 'Two', page: 3),
    ]);
    final png = await tester.runAsync(
      () => document.renderRegion(1, const Rect.fromLTWH(0, 0, 0.5, 0.5)),
    );
    expect(png!.sublist(0, 4), [0x89, 0x50, 0x4e, 0x47]);
  });

  testWidgets('refuses a file that is no PDF', (tester) async {
    // runAsync reports what is thrown inside instead of passing it on.
    final refused = await tester.runAsync(() async {
      try {
        await PdfrxEngine().open(Uint8List.fromList(utf8.encode('text')));
        return false;
      } on FormatException {
        return true;
      }
    });
    expect(refused, isTrue);
  });

  testWidgets('its viewer turns pages and finds text', (tester) async {
    final document = await tester.runAsync(
      () => PdfrxEngine().open(_threePages()),
    );
    final controller = PdfReaderController();
    addTearDown(controller.dispose);
    await tester.pumpWidget(
      MaterialApp(
        home: Scaffold(
          body: SizedBox(
            width: 600,
            height: 800,
            child: document!.viewer(controller),
          ),
        ),
      ),
    );
    Future<void> until(bool Function() test) async {
      final waited = Stopwatch()..start();
      while (!test() && waited.elapsed < const Duration(seconds: 20)) {
        await tester.pump(const Duration(milliseconds: 100));
      }
    }

    await until(() => controller.isReady);
    expect(controller.isReady, isTrue);

    // The page turns over an animation, whose frames the test drives: it
    // is started, then pumped until it arrives.
    unawaited(controller.goToPage(3));
    await until(() => controller.page == 3);
    expect(controller.page, 3);

    controller.search('hello');
    await until(() => controller.matchCount == 3);
    expect(controller.matchCount, 3);
    expect(controller.pageRect(3), isNotNull);
  });
}

/// A PDF of three pages, each saying "Hello page N", with an outline of
/// chapter "One" at page 1 and "Two" at page 3.
Uint8List _threePages() {
  String text(int page) {
    final stream = 'BT /F1 24 Tf 40 700 Td (Hello page $page) Tj ET';
    return '<< /Length ${stream.length} >>\nstream\n$stream\nendstream';
  }

  String pageOf(int page) =>
      '<< /Type /Page /Parent 2 0 R /MediaBox [0 0 612 792] '
      '/Contents ${5 + page} 0 R /Resources << /Font << /F1 9 0 R >> >> >>';

  final objects = [
    '<< /Type /Catalog /Pages 2 0 R /Outlines 10 0 R >>',
    '<< /Type /Pages /Kids [3 0 R 4 0 R 5 0 R] /Count 3 >>',
    for (final page in [1, 2, 3]) pageOf(page),
    for (final page in [1, 2, 3]) text(page),
    '<< /Type /Font /Subtype /Type1 /BaseFont /Helvetica >>',
    '<< /Type /Outlines /First 11 0 R /Last 12 0 R /Count 2 >>',
    '<< /Title (One) /Parent 10 0 R /Next 12 0 R /Dest [3 0 R /Fit] >>',
    '<< /Title (Two) /Parent 10 0 R /Prev 11 0 R /Dest [5 0 R /Fit] >>',
  ];
  final out = StringBuffer('%PDF-1.7\n');
  final offsets = <int>[];
  for (final (index, object) in objects.indexed) {
    offsets.add(out.length);
    out.write('${index + 1} 0 obj\n$object\nendobj\n');
  }
  final xref = out.length;
  out
    ..write('xref\n0 ${objects.length + 1}\n0000000000 65535 f \n')
    ..writeAll([
      for (final offset in offsets)
        '${offset.toString().padLeft(10, '0')} 00000 n \n',
    ])
    ..write(
      'trailer\n<< /Size ${objects.length + 1} /Root 1 0 R >>\n'
      'startxref\n$xref\n%%EOF\n',
    );
  return Uint8List.fromList(latin1.encode(out.toString()));
}