32 lines
1.1 KiB
Dart
32 lines
1.1 KiB
Dart
/// Converts an ISO 3166-1 alpha-2 country code to a flag emoji.
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///
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/// Uses Unicode Regional Indicator Symbols to create flag emojis.
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/// Each letter A-Z maps to a regional indicator symbol (U+1F1E6 to U+1F1FF).
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/// Combining two regional indicators creates a flag emoji.
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///
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/// Example: 'US' -> 🇺🇸, 'GB' -> 🇬🇧, 'CA' -> 🇨🇦
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///
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/// Returns null if the country code is invalid or null.
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String? getCountryFlag(String? countryCode) {
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if (countryCode == null || countryCode.length != 2) {
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return null;
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}
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final code = countryCode.toUpperCase();
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// Validate that both characters are A-Z
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if (!RegExp(r'^[A-Z]{2}$').hasMatch(code)) {
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return null;
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}
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// Convert each letter to its regional indicator symbol
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// 'A' = 65 in ASCII, Regional Indicator A = 0x1F1E6
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// Offset = 0x1F1E6 - 65 = 127397
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const int regionalIndicatorOffset = 0x1F1E6 - 65;
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final firstChar = code.codeUnitAt(0) + regionalIndicatorOffset;
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final secondChar = code.codeUnitAt(1) + regionalIndicatorOffset;
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return String.fromCharCodes([firstChar, secondChar]);
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}
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