feat: implement xsd:double codec

CHANGELOG.md

@@ -28,4 +28,5 @@
 - Implement `xsd:duration` codec and data type
 - Implement `xsd:datetime` codec and data type
 - Implement `xsd:anyUri` codec
-- Implement `xsd:decimal` codec
+- Implement `xsd:decimal` codec
+- Implement `xsd:double` codec

README.md

@@ -32,7 +32,7 @@ This library aims to support the following XSD 1.1 built-in datatypes that are c
 |         `xsd:language` |      ✅      |        ✅        |    `Locale`    |     `package:intl`    |
 |           `xsd:NCName` |      ✅      |        ✅        |    `String`    |     `dart:core`    |
 |          `xsd:decimal` |      ✅      |        ✅        |    `Decimal`    |     `package:decimal`    |
-|           `xsd:double` |      ✅      |        ❌        |    `double`    |     `dart:core`    |
+|           `xsd:double` |      ✅      |        ✅        |    `double`    |     `dart:core`    |
 |            `xsd:float` |      ✅      |        ❌        |    `double`    |     `dart:core`    |
 |          `xsd:integer` |      ✅      |        ❌        |    `BigInt`    |     `dart:core`    |
 | `xsd:nonPositiveInteger` |      ✅      |        ✅        |    `BigInt`    |     `dart:core`    |

lib/src/codecs/codecs.dart

@@ -26,3 +26,4 @@ export 'duration/xsd_duration_codec.dart';
 export 'datetime/xsd_datetime_codec.dart';
 export 'any_uri/any_uri_codec.dart';
 export 'decimal/decimal_codec.dart';
+export 'double/double_codec.dart';

lib/src/codecs/double/double_codec.dart

@@ -0,0 +1,42 @@
+import 'dart:convert';
+
+import 'package:xsd/src/helpers/whitespace.dart';
+
+/// A [Codec] that converts between XSD `double` strings and [double] values.
+class XsdDoubleCodec extends Codec<double, String> {
+  const XsdDoubleCodec();
+
+  @override
+  Converter<double, String> get encoder => const XsdDoubleEncoder();
+
+  @override
+  Converter<String, double> get decoder => const XsdDoubleDecoder();
+}
+
+class XsdDoubleEncoder extends Converter<double, String> {
+  const XsdDoubleEncoder();
+
+  @override
+  String convert(double input) {
+    if (input.isNaN) return 'NaN';
+    if (input == double.infinity) return 'INF';
+    if (input == double.negativeInfinity) return '-INF';
+    // Dart's toString() might produce scientific notation 1.2e+3, XSD accepts 1.2E3 or 1.2e3.
+    // XSD canonical form uses 'E'.
+    return input.toString().toUpperCase();
+  }
+}
+
+class XsdDoubleDecoder extends Converter<String, double> {
+  const XsdDoubleDecoder();
+
+  @override
+  double convert(String input) {
+    final trimmed = processWhiteSpace(input, Whitespace.collapse);
+    if (trimmed == 'INF') return double.infinity;
+    if (trimmed == '-INF') return double.negativeInfinity;
+    if (trimmed == 'NaN') return double.nan;
+
+    return double.parse(trimmed);
+  }
+}

test/codecs/double_codec_test.dart

@@ -0,0 +1,37 @@
+import 'package:test/test.dart';
+import 'package:xsd/xsd.dart';
+
+void main() {
+  group('XsdDoubleCodec', () {
+    const codec = XsdDoubleCodec();
+
+    test('should encode valid double', () {
+      expect(codec.encode(123.45), '123.45');
+      expect(codec.encode(-123.45), '-123.45');
+      expect(codec.encode(double.infinity), 'INF');
+      expect(codec.encode(double.negativeInfinity), '-INF');
+      expect(codec.encode(double.nan), 'NaN');
+      expect(codec.encode(double.nan), 'NaN');
+    });
+
+    test('should decode valid double', () {
+      expect(codec.decode('123.45'), 123.45);
+      expect(codec.decode('-123.45'), -123.45);
+      expect(codec.decode('INF'), double.infinity);
+      expect(codec.decode('-INF'), double.negativeInfinity);
+      expect(codec.decode('NaN').isNaN, isTrue);
+      expect(codec.decode('1.2E3'), 1200.0);
+      expect(codec.decode('1.2e3'), 1200.0);
+    });
+
+    test('should handle whitespace collapsing', () {
+      expect(codec.decode('  123.45  '), 123.45);
+      expect(codec.decode('\n-123.45\t'), -123.45);
+    });
+
+    test('should throw FormatException for invalid input', () {
+      expect(() => codec.decode('invalid'), throwsFormatException);
+      expect(() => codec.decode('1.2.3'), throwsFormatException);
+    });
+  });
+}