import 'dart:convert';
import 'dart:io';

import 'package:flutter_test/flutter_test.dart';

/// The messages of the `.arb` file [name] in `lib/l10n/`, without metadata.
Map<String, String> _messages(String name) => {
  for (final MapEntry(:key, :value) in (jsonDecode(
    File('lib/l10n/$name').readAsStringSync(),
  ) as Map<String, Object?>).entries)
    if (!key.startsWith('@')) key: value! as String,
};

/// The names of the placeholders in [message], with plural and select
/// arguments; the words of their branches don't count. (gen-l10n reads
/// quotes as text here: `use-escaping` is off.)
Set<String> _placeholders(String message) {
  final names = <String>{};
  // Even depths hold text and placeholders, odd ones a plural's branches.
  var depth = 0;
  for (var i = 0; i < message.length; i++) {
    switch (message[i]) {
      case '{':
        final name = RegExp(r'\{\s*(\w+)\s*[,}]').matchAsPrefix(message, i);
        if (name != null && depth.isEven) {
          names.add(name.group(1)!);
        }
        depth++;
      case '}':
        depth--;
    }
  }
  return names;
}

void main() {
  final template = _messages('app_en.arb');

  test('German has every message, with the same placeholders', () {
    final german = _messages('app_de.arb');

    expect(
      template.keys.where((key) => !german.containsKey(key)),
      isEmpty,
      reason: 'untranslated',
    );
    expect(
      german.keys.where((key) => !template.containsKey(key)),
      isEmpty,
      reason: 'not in the template',
    );
    for (final MapEntry(:key, :value) in german.entries) {
      expect(_placeholders(value), _placeholders(template[key]!), reason: key);
    }
  });

  test("the English variants override the template's messages only, with "
      'the same placeholders', () {
    for (final variant in ['app_en_GB.arb', 'app_en_US.arb']) {
      for (final MapEntry(:key, :value) in _messages(variant).entries) {
        expect(template, contains(key), reason: '$variant: $key');
        expect(
          _placeholders(value),
          _placeholders(template[key]!),
          reason: '$variant: $key',
        );
      }
    }
  });

  test('a placeholder is found also inside a plural', () {
    expect(
      _placeholders('{count, plural, =1{1 card} other{{count} cards in {t}}}'),
      {'count', 't'},
    );
    expect(_placeholders("Couldn't open {name}"), {'name'});
  });
}