Add ICU4X number formatting to package:intl4x (#791)

* Add ICU4X number formatting to package:intl4x

* Add checks to readme

* Working on matching options

* Fix testing

* Add newlines

.gitignore

@@ -16,3 +16,5 @@
 # Specific files
 pkgs/intl/test/number_format_compact_google3_icu_test.dart
 pkgs/intl/update_from_cldr_data.sh
+
+.vscode

pkgs/intl4x/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.8.2-wip
+
+- Add ICU4X support for number formatting.
+
 ## 0.8.1
 
 - Add ICU4X support for collation.

pkgs/intl4x/README.md

@@ -18,7 +18,7 @@ via our [issue tracker](https://github.com/dart-lang/i18n/issues)).
 |   | Number format  | List format  | Date format  | Collation  | Display names | Plural Rules |
 |---|:---:|:---:|:---:|:---:|:---:|:---:|
 | **ECMA402 (web)** | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: |
-| **ICU4X (web/native)**  |   |   |   |   |   |   |
+| **ICU4X (web/native)**  | :heavy_check_mark: |   |   | :heavy_check_mark: |   |   |
 
 ## Implementation and Goals
 

pkgs/intl4x/analysis_options.yaml

@@ -12,3 +12,6 @@ analyzer:
   exclude:
     - "submodules/*"
     - "lib/src/bindings/*"
+
+  enable-experiment:
+    - native-assets

pkgs/intl4x/lib/src/collation/collation_stub_4x.dart

@@ -10,4 +10,4 @@ import 'collation_impl.dart';
 /// Stub for the conditional import
 CollationImpl getCollator4X(
         Locale locale, Data data, CollationOptions options) =>
-    throw UnimplementedError('Cannot use ECMA outside of web environments.');
+    throw UnimplementedError('Cannot use ICU4X in web environments.');

pkgs/intl4x/lib/src/number_format/number_format_4x.dart

@@ -2,8 +2,13 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'dart:math';
+
+import '../bindings/lib.g.dart' as icu;
 import '../data.dart';
+import '../data_4x.dart';
 import '../locale/locale.dart';
+import '../locale/locale_4x.dart';
 import 'number_format_impl.dart';
 import 'number_format_options.dart';
 
@@ -12,10 +17,114 @@ NumberFormatImpl getNumberFormatter4X(
     NumberFormat4X(locale, data, options);
 
 class NumberFormat4X extends NumberFormatImpl {
-  NumberFormat4X(super.locale, Data data, super.options);
+  final icu.FixedDecimalFormatter _formatter;
+  NumberFormat4X(super.locale, Data data, super.options)
+      : _formatter = icu.FixedDecimalFormatter.withGroupingStrategy(
+          data.to4X(),
+          locale.to4X(),
+          options.groupingStrategy4X(),
+        );
 
   @override
   String formatImpl(Object number) {
-    throw UnimplementedError('Insert diplomat bindings here');
+    final fixedDecimal = _toFixedDecimal(number);
+    final format = _formatter.format(fixedDecimal);
+    return format;
+  }
+
+  icu.FixedDecimal _toFixedDecimal(Object number) {
+    final icu.FixedDecimal fixedDecimal;
+    fixedDecimal = switch (number) {
+      final int i => icu.FixedDecimal.fromInt(i),
+      final double d => icu.FixedDecimal.fromDoubleWithDoublePrecision(d),
+      final String s => icu.FixedDecimal.fromString(s),
+      Object() => icu.FixedDecimal.fromString(number.toString()),
+    };
+    return _constructDouble(fixedDecimal);
+  }
+
+  icu.FixedDecimal _constructDouble(icu.FixedDecimal fixedDecimal) {
+    fixedDecimal.padStart(options.minimumIntegerDigits);
+    final minFractionDigits = options.digits?.fractionDigits.$1;
+    final maxFractionDigits = options.digits?.fractionDigits.$2;
+    final minSignificantDigits = options.digits?.significantDigits.$1;
+    final maxSignificantDigits = options.digits?.significantDigits.$2;
+
+    final overhead = fixedDecimal.length - (maxSignificantDigits ?? 0);
+    final maxSignificantPosition = fixedDecimal.magnitudeStart + overhead;
+    final maxFractionPosition =
+        max(fixedDecimal.magnitudeStart, -(maxFractionDigits ?? 0));
+
+    final roundingPriority = options.digits?.roundingPriority;
+    final bool? useSignificant;
+    if (maxFractionDigits != null &&
+        maxSignificantDigits != null &&
+        roundingPriority != null) {
+      useSignificant = switch (roundingPriority) {
+        RoundingPriority.auto => true,
+        RoundingPriority.morePrecision =>
+          maxSignificantPosition < maxFractionPosition,
+        RoundingPriority.lessPrecision =>
+          maxSignificantPosition > maxFractionPosition,
+      };
+    } else {
+      useSignificant = null;
+    }
+
+    if (minFractionDigits != null) {
+      fixedDecimal.padEnd(-minFractionDigits);
+    }
+    if (maxFractionDigits != null && !(useSignificant ?? false)) {
+      final int position;
+      if (minFractionDigits != null) {
+        position = min(maxFractionPosition, -minFractionDigits);
+      } else {
+        position = maxFractionPosition;
+      }
+      _roundDecimal(fixedDecimal, position);
+    }
+    if (minSignificantDigits != null &&
+        fixedDecimal.length < minSignificantDigits) {
+      final missingZeroes = minSignificantDigits - fixedDecimal.length;
+      fixedDecimal.padEnd(fixedDecimal.magnitudeStart - missingZeroes);
+    }
+    if (maxSignificantDigits != null &&
+        fixedDecimal.length > maxSignificantDigits &&
+        (useSignificant ?? true)) {
+      _roundDecimal(fixedDecimal, maxSignificantPosition);
+    }
+    return fixedDecimal;
+  }
+
+  void _roundDecimal(
+      icu.FixedDecimal fixedDecimal, int maxSignificantPosition) {
+    final roundingFunction = switch (options.roundingMode) {
+      RoundingMode.ceil => fixedDecimal.ceil,
+      RoundingMode.floor => fixedDecimal.floor,
+      RoundingMode.expand => fixedDecimal.expand,
+      RoundingMode.trunc => fixedDecimal.trunc,
+      RoundingMode.halfCeil => fixedDecimal.halfCeil,
+      RoundingMode.halfFloor => fixedDecimal.halfFloor,
+      RoundingMode.halfExpand => fixedDecimal.halfExpand,
+      RoundingMode.halfTrunc => fixedDecimal.halfTrunc,
+      RoundingMode.halfEven => fixedDecimal.halfEven,
+    };
+    roundingFunction(maxSignificantPosition);
   }
 }
+
+extension on NumberFormatOptions {
+  icu.FixedDecimalGroupingStrategy groupingStrategy4X() =>
+      switch (useGrouping) {
+        Grouping.always => icu.FixedDecimalGroupingStrategy.always,
+        Grouping.auto => icu.FixedDecimalGroupingStrategy.auto,
+        Grouping.never => icu.FixedDecimalGroupingStrategy.never,
+        Grouping.min2 => icu.FixedDecimalGroupingStrategy.min2,
+      };
+}
+
+extension on icu.FixedDecimal {
+  int get length => fractionLength + integerLength;
+  int get fractionLength => max(0, -magnitudeStart);
+  int get integerLength => max(0, magnitudeEnd + 1);
+}

pkgs/intl4x/lib/src/number_format/number_format_impl.dart

@@ -7,9 +7,10 @@ import '../ecma/ecma_policy.dart';
 import '../locale/locale.dart';
 import '../options.dart';
 import '../utils.dart';
-import 'number_format_4x.dart';
 import 'number_format_options.dart';
 import 'number_format_stub.dart' if (dart.library.js) 'number_format_ecma.dart';
+import 'number_format_stub_4x.dart'
+    if (dart.library.io) 'number_format_4x.dart';
 
 /// This is an intermediate to defer to the actual implementations of
 /// Number formatting.

pkgs/intl4x/lib/src/number_format/number_format_options.dart

@@ -274,7 +274,8 @@ final class Digits {
         significantDigits = (null, null),
         roundingPriority = null,
         assert(roundingIncrement == null ||
-            ((minimum != null || maximum != null) || minimum == maximum));
+            ((minimum != null || maximum != null) || minimum == maximum)),
+        assert((minimum == null || maximum == null) || minimum < maximum);
 
   const Digits.withSignificantDigits({
     int? minimum = 1,

pkgs/intl4x/lib/src/number_format/number_format_stub_4x.dart

@@ -0,0 +1,12 @@
+// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import '../data.dart';
+import '../locale/locale.dart';
+import 'number_format_impl.dart';
+import 'number_format_options.dart';
+
+NumberFormatImpl getNumberFormatter4X(
+        Locale locale, Data data, NumberFormatOptions options) =>
+    throw UnimplementedError('Cannot use ICU4X in web environments.');

pkgs/intl4x/lib/src/plural_rules/plural_rules_impl.dart

@@ -9,9 +9,9 @@ import '../locale/locale.dart';
 import '../options.dart';
 import '../utils.dart';
 import 'plural_rules.dart';
-import 'plural_rules_4x.dart';
 import 'plural_rules_options.dart';
 import 'plural_rules_stub.dart' if (dart.library.js) 'plural_rules_ecma.dart';
+import 'plural_rules_stub_4x.dart' if (dart.library.io) 'plural_rules_4x.dart';
 
 abstract class PluralRulesImpl {
   final Locale locale;

pkgs/intl4x/lib/src/plural_rules/plural_rules_stub_4x.dart

@@ -0,0 +1,15 @@
+// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import '../../plural_rules.dart';
+import '../data.dart';
+import '../locale/locale.dart';
+import 'plural_rules_impl.dart';
+
+PluralRulesImpl getPluralSelect4X(
+  Locale locale,
+  Data data,
+  PluralRulesOptions options,
+) =>
+    throw UnimplementedError('Cannot use ICU4X in web environments.');

pkgs/intl4x/pubspec.yaml

@@ -1,7 +1,7 @@
 name: intl4x
 description: >-
   A lightweight modular library for internationalization (i18n) functionality.
-version: 0.8.1
+version: 0.8.2-wip
 repository: https://github.com/dart-lang/i18n/tree/main/pkgs/intl4x
 platforms: ## TODO: Add native platforms once ICU4X is integrated.
   web:
@@ -18,6 +18,7 @@ dev_dependencies:
   args: ^2.4.2
   build_runner: ^2.1.4
   build_web_compilers: ^3.2.1
+  collection: ^1.18.0
   dart_flutter_team_lints: ^1.0.0
   lints: ^2.0.0
   native_assets_cli: ^0.3.2