pkg/matcher: split out order matchers from numeric matchers lib

lib/src/order_matchers.dart

+// Copyright (c) 2016, 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 'interfaces.dart';
+
+/// Returns a matcher which matches if the match argument is greater
+/// than the given [value].
+Matcher greaterThan(value) =>
+    new _OrderingMatcher(value, false, false, true, 'a value greater than');
+
+/// Returns a matcher which matches if the match argument is greater
+/// than or equal to the given [value].
+Matcher greaterThanOrEqualTo(value) => new _OrderingMatcher(
+    value, true, false, true, 'a value greater than or equal to');
+
+/// Returns a matcher which matches if the match argument is less
+/// than the given [value].
+Matcher lessThan(value) =>
+    new _OrderingMatcher(value, false, true, false, 'a value less than');
+
+/// Returns a matcher which matches if the match argument is less
+/// than or equal to the given [value].
+Matcher lessThanOrEqualTo(value) => new _OrderingMatcher(
+    value, true, true, false, 'a value less than or equal to');
+
+/// A matcher which matches if the match argument is zero.
+const Matcher isZero =
+    const _OrderingMatcher(0, true, false, false, 'a value equal to');
+
+/// A matcher which matches if the match argument is non-zero.
+const Matcher isNonZero =
+    const _OrderingMatcher(0, false, true, true, 'a value not equal to');
+
+/// A matcher which matches if the match argument is positive.
+const Matcher isPositive =
+    const _OrderingMatcher(0, false, false, true, 'a positive value', false);
+
+/// A matcher which matches if the match argument is zero or negative.
+const Matcher isNonPositive =
+    const _OrderingMatcher(0, true, true, false, 'a non-positive value', false);
+
+/// A matcher which matches if the match argument is negative.
+const Matcher isNegative =
+    const _OrderingMatcher(0, false, true, false, 'a negative value', false);
+
+/// A matcher which matches if the match argument is zero or positive.
+const Matcher isNonNegative =
+    const _OrderingMatcher(0, true, false, true, 'a non-negative value', false);
+
+// TODO(kevmoo) Note that matchers that use _OrderingComparison only use
+// `==` and `<` operators to evaluate the match. Or change the matcher.
+class _OrderingMatcher extends Matcher {
+  /// Expected value.
+  final _value;
+
+  /// What to return if actual == expected
+  final bool _equalValue;
+
+  /// What to return if actual < expected
+  final bool _lessThanValue;
+
+  /// What to return if actual > expected
+  final bool _greaterThanValue;
+
+  /// Textual name of the inequality
+  final String _comparisonDescription;
+
+  /// Whether to include the expected value in the description
+  final bool _valueInDescription;
+
+  const _OrderingMatcher(this._value, this._equalValue, this._lessThanValue,
+      this._greaterThanValue, this._comparisonDescription,
+      [bool valueInDescription = true])
+      : this._valueInDescription = valueInDescription;
+
+  bool matches(item, Map matchState) {
+    if (item == _value) {
+      return _equalValue;
+    } else if (item < _value) {
+      return _lessThanValue;
+    } else {
+      return _greaterThanValue;
+    }
+  }
+
+  Description describe(Description description) {
+    if (_valueInDescription) {
+      return description
+          .add(_comparisonDescription)
+          .add(' ')
+          .addDescriptionOf(_value);
+    } else {
+      return description.add(_comparisonDescription);
+    }
+  }
+
+  Description describeMismatch(
+      item, Description mismatchDescription, Map matchState, bool verbose) {
+    mismatchDescription.add('is not ');
+    return describe(mismatchDescription);
+  }
+}