Convert most interfaces in dart:core to abstract classes.

lib/core/duration.dart

Index: lib/core/duration.dart
diff --git a/lib/core/duration.dart b/lib/core/duration.dart
index c3bf66b37cffda10e391e1e54276fdcc12b273c8..f6a32fab8c27cba4a985e22659bd2d0a2636a201 100644
--- a/lib/core/duration.dart
+++ b/lib/core/duration.dart
@@ -7,7 +7,29 @@
 /**
  * A [Duration] represents a time span. A duration can be negative.
  */
-interface Duration extends Comparable default DurationImplementation {
+class Duration implements Comparable, Hashable {
+  static const int MILLISECONDS_PER_SECOND = 1000;
+  static const int SECONDS_PER_MINUTE = 60;
+  static const int MINUTES_PER_HOUR = 60;
+  static const int HOURS_PER_DAY = 24;
+
+  static const int MILLISECONDS_PER_MINUTE =
+      MILLISECONDS_PER_SECOND * SECONDS_PER_MINUTE;
+  static const int MILLISECONDS_PER_HOUR =
+      MILLISECONDS_PER_MINUTE * MINUTES_PER_HOUR;
+  static const int MILLISECONDS_PER_DAY =
+      MILLISECONDS_PER_HOUR * HOURS_PER_DAY;
+
+  static const int SECONDS_PER_HOUR = SECONDS_PER_MINUTE * MINUTES_PER_HOUR;
+  static const int SECONDS_PER_DAY = SECONDS_PER_HOUR * HOURS_PER_DAY;
+
+  static const int MINUTES_PER_DAY = MINUTES_PER_HOUR * HOURS_PER_DAY;
+
+  /**
+   * This [Duration] in milliseconds.
+   */
+  final int inMilliseconds;
+
   /**
    * The duration is the sum of all individual parts. This means that individual
    * parts don't need to be less than the next-bigger unit. For example [hours]
@@ -16,51 +38,83 @@ interface Duration extends Comparable default DurationImplementation {
    * All individual parts are allowed to be negative.
    * All arguments are by default 0.
    */
-  const Duration({int days, int hours, int minutes, int seconds,
-                  int milliseconds});
+  const Duration({int days: 0,
+                  int hours: 0,
+                  int minutes: 0,
+                  int seconds: 0,
+                  int milliseconds: 0})
+      : inMilliseconds = days * Duration.MILLISECONDS_PER_DAY +
+                         hours * Duration.MILLISECONDS_PER_HOUR +
+                         minutes * Duration.MILLISECONDS_PER_MINUTE +
+                         seconds * Duration.MILLISECONDS_PER_SECOND +
+                         milliseconds;
 
   /**
-   * Returns this [Duration] in days. Incomplete days are discarded.
+   * This [Duration] in days. Incomplete days are discarded
    */
-  int get inDays;
+  int get inDays {
+    return inMilliseconds ~/ Duration.MILLISECONDS_PER_DAY;
+  }
 
   /**
-   * Returns this [Duration] in hours. Incomplete hours are discarded.
+   * This [Duration] in hours. Incomplete hours are discarded.
    * The returned value can be greater than 23.
    */
-  int get inHours;
+  int get inHours {
+    return inMilliseconds ~/ Duration.MILLISECONDS_PER_HOUR;
+  }
 
   /**
-   * Returns this [Duration] in minutes. Incomplete minutes are discarded.
+   * This [Duration] in minutes. Incomplete minutes are discarded.
    * The returned value can be greater than 59.
    */
-  int get inMinutes;
+  int get inMinutes {
+    return inMilliseconds ~/ Duration.MILLISECONDS_PER_MINUTE;
+  }
 
   /**
-   * Returns this [Duration] in seconds. Incomplete seconds are discarded.
+   * This [Duration] in seconds. Incomplete seconds are discarded.
    * The returned value can be greater than 59.
    */
-  int get inSeconds;
+  int get inSeconds {
+    return inMilliseconds ~/ Duration.MILLISECONDS_PER_SECOND;
+  }
 
-  /**
-   * Returns this [Duration] in milliseconds.
-   */
-  int get inMilliseconds;
+  bool operator ==(other) {
+    if (other is !Duration) return false;
+    return inMilliseconds == other.inMilliseconds;
+  }
 
-  static const int MILLISECONDS_PER_SECOND = 1000;
-  static const int SECONDS_PER_MINUTE = 60;
-  static const int MINUTES_PER_HOUR = 60;
-  static const int HOURS_PER_DAY = 24;
+  int hashCode() {
+    return inMilliseconds.hashCode();
+  }
 
-  static const int MILLISECONDS_PER_MINUTE =
-      MILLISECONDS_PER_SECOND * SECONDS_PER_MINUTE;
-  static const int MILLISECONDS_PER_HOUR =
-      MILLISECONDS_PER_MINUTE * MINUTES_PER_HOUR;
-  static const int MILLISECONDS_PER_DAY =
-      MILLISECONDS_PER_HOUR * HOURS_PER_DAY;
+  int compareTo(Duration other) {
+    return inMilliseconds.compareTo(other.inMilliseconds);
+  }
 
-  static const int SECONDS_PER_HOUR = SECONDS_PER_MINUTE * MINUTES_PER_HOUR;
-  static const int SECONDS_PER_DAY = SECONDS_PER_HOUR * HOURS_PER_DAY;
+  String toString() {
+    String threeDigits(int n) {
+      if (n >= 100) return "$n";
+      if (n > 10) return "0$n";
+      return "00$n";
+    }
+    String twoDigits(int n) {
+      if (n >= 10) return "$n";
+      return "0$n";
+    }
 
-  static const int MINUTES_PER_DAY = MINUTES_PER_HOUR * HOURS_PER_DAY;
+    if (inMilliseconds < 0) {
+      Duration duration =
+          new Duration(milliseconds: -inMilliseconds);
+      return "-$duration";
+    }
+    String twoDigitMinutes =
+        twoDigits(inMinutes.remainder(Duration.MINUTES_PER_HOUR));
+    String twoDigitSeconds =
+        twoDigits(inSeconds.remainder(Duration.SECONDS_PER_MINUTE));
+    String threeDigitMs =
+        threeDigits(inMilliseconds.remainder(Duration.MILLISECONDS_PER_SECOND));
+    return "$inHours:$twoDigitMinutes:$twoDigitSeconds.$threeDigitMs";
+  }
 }