// Coverage Reporter
//
// This script generates markdown-formatted test coverage reports for GitHub PRs.
//
// ## Usage
//
// The script reads an `lcov.info` file generated by the Dart coverage tool and
// outputs a markdown report showing:
// - Overall coverage percentage
// - Lines covered vs total lines
// - Per-file coverage breakdown sorted by coverage percentage
//
// ### Local Usage
//
// ```bash
// # Run tests with coverage
// dart test --coverage=coverage
//
// # Format coverage to lcov
// dart pub global activate coverage
// dart pub global run coverage:format_coverage --lcov --in=coverage --out=coverage/lcov.info --report-on=lib --check-ignore --ignore-files="**/*.g.dart"
//
// # Generate markdown report
// dart scripts/coverage_report.dart
//
// # For CI mode (no decorations)
// dart scripts/coverage_report.dart --ci
// ```
//
// ### CI Usage
//
// This script is automatically run as part of the CI pipeline in the `tests`
// job. The generated report is posted as a comment on pull requests.

import 'dart:io';

Future<void> main(List<String> args) async {
  final runningInCI = args.contains('--ci');
  final lcovFile = File('coverage/lcov.info');

  if (!lcovFile.existsSync()) {
    stderr.writeln('Error: coverage/lcov.info not found');
    exit(1);
  }

  final String lcovContent;
  try {
    lcovContent = lcovFile.readAsStringSync();
  } on Exception catch (e) {
    stderr.writeln('Error reading coverage/lcov.info: $e');
    exit(1);
  }

  final coverage = _parseLcov(lcovContent);
  final totalLines = coverage['total_lines'] as int;
  final coveredLines = coverage['covered_lines'] as int;
  final percentage = totalLines > 0
      ? (coveredLines / totalLines * 100).toStringAsFixed(2)
      : '0.00';

  if (!runningInCI) print('\n${'=' * 60}');
  print('## Test Coverage Report\n');
  print(
    [
      'This report shows the test coverage for the project.',
    ].join(runningInCI ? '' : '\n'),
  );
  if (!runningInCI) print('-' * 60);
  print('');
  print('**Total Coverage: $percentage%**');
  print('');
  print('- Lines covered: $coveredLines / $totalLines');
  print('');

  // Print per-file coverage in a collapsible section
  final files = coverage['files'] as Map<String, Map<String, int>>;
  if (files.isNotEmpty) {
    print('<details>');
    print('<summary>File Coverage</summary>');
    print('');
    final sortedFiles = files.entries.toList()
      ..sort((a, b) {
        final aTotal = a.value['total']!;
        final bTotal = b.value['total']!;
        if (aTotal == 0 && bTotal == 0) return 0;
        if (aTotal == 0) return 1;
        if (bTotal == 0) return -1;
        final aPercent = a.value['covered']! / aTotal;
        final bPercent = b.value['covered']! / bTotal;
        return bPercent.compareTo(aPercent);
      });

    for (final entry in sortedFiles) {
      final fileName = entry.key.split('/').last;
      final covered = entry.value['covered']!;
      final total = entry.value['total']!;
      final filePercentage = total > 0
          ? (covered / total * 100).toStringAsFixed(1)
          : '0.0';
      print('- `$fileName`: $filePercentage% ($covered/$total lines)');
    }
    print('');
    print('</details>');
  }

  if (!runningInCI) print('\n${'=' * 60}\n');
}

Map<String, dynamic> _parseLcov(String lcovContent) {
  final lines = lcovContent.split('\n');
  var totalLines = 0;
  var coveredLines = 0;
  final files = <String, Map<String, int>>{};

  String? currentFile;
  var currentFileLines = 0;
  var currentFileCovered = 0;

  for (final line in lines) {
    if (line.startsWith('SF:')) {
      // Save previous file data if it exists (handles malformed lcov)
      if (currentFile != null && currentFileLines > 0) {
        totalLines += currentFileLines;
        coveredLines += currentFileCovered;
        files[currentFile] = {
          'total': currentFileLines,
          'covered': currentFileCovered,
        };
      }
      currentFile = line.substring(3);
      currentFileLines = 0;
      currentFileCovered = 0;
    } else if (line.startsWith('DA:')) {
      final parts = line.substring(3).split(',');
      if (parts.length >= 2) {
        final hits = int.tryParse(parts[1]) ?? 0;
        currentFileLines++;
        if (hits > 0) {
          currentFileCovered++;
        }
      }
    } else if (line == 'end_of_record' && currentFile != null) {
      if (currentFileLines > 0) {
        totalLines += currentFileLines;
        coveredLines += currentFileCovered;
        files[currentFile] = {
          'total': currentFileLines,
          'covered': currentFileCovered,
        };
      }
      currentFile = null;
    }
  }

  // Handle case where file ends without 'end_of_record'
  if (currentFile != null && currentFileLines > 0) {
    totalLines += currentFileLines;
    coveredLines += currentFileCovered;
    files[currentFile] = {
      'total': currentFileLines,
      'covered': currentFileCovered,
    };
  }

  return {
    'total_lines': totalLines,
    'covered_lines': coveredLines,
    'files': files,
  };
}