1 files changed, 183 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/events/Event.java b/src/main/java/com/google/devtools/build/lib/events/Event.java
new file mode 100644
index 0000000000..db5bc5f8ee
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/events/Event.java
@@ -0,0 +1,183 @@
+// Copyright 2014 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package com.google.devtools.build.lib.events;
+
+import static java.nio.charset.StandardCharsets.ISO_8859_1;
+
+import com.google.common.base.Preconditions;
+
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * An event is a situation encountered by the build system that's worth
+ * reporting: A 3-tuple of ({@link EventKind}, {@link Location}, message).
+ */
+@Immutable
+public final class Event {
+
+  private final EventKind kind;
+  private final Location location;
+  private final String message;
+  /**
+   * An alternative representation for message.
+   * Exactly one of message or messageBytes will be non-null.
+   * If messageBytes is non-null, then it contains the bytes
+   * of the message, encoded using the platform's default charset.
+   * We do this to avoid converting back and forth between Strings
+   * and bytes.
+   */
+  private final byte[] messageBytes;
+
+  @Nullable
+  private final String tag;
+
+  public Event withTag(String tag) {
+    if (this.message != null) {
+      return new Event(this.kind, this.location, this.message, tag);
+    } else {
+      return new Event(this.kind, this.location, this.messageBytes, tag);
+    }
+  }
+
+  public Event(EventKind kind, @Nullable Location location, String message) {
+    this(kind, location, message, null);
+  }
+
+  public Event(EventKind kind, @Nullable Location location, String message, @Nullable String tag) {
+    this.kind = kind;
+    this.location = location;
+    this.message = Preconditions.checkNotNull(message);
+    this.messageBytes = null;
+    this.tag = tag;
+  }
+
+  public Event(EventKind kind, @Nullable Location location, byte[] messageBytes) {
+    this(kind, location, messageBytes, null);
+  }
+
+  public Event(
+      EventKind kind, @Nullable Location location, byte[] messageBytes, @Nullable String tag) {
+    this.kind = kind;
+    this.location = location;
+    this.message = null;
+    this.messageBytes = Preconditions.checkNotNull(messageBytes);
+    this.tag = tag;
+  }
+
+  public String getMessage() {
+    return message != null ? message : new String(messageBytes);
+  }
+
+  public byte[] getMessageBytes() {
+    return messageBytes != null ? messageBytes : message.getBytes(ISO_8859_1);
+  }
+
+  public EventKind getKind() {
+    return kind;
+  }
+
+  /**
+   * the tag is typically the action that generated the event.
+   */
+  @Nullable
+  public String getTag() {
+    return tag;
+  }
+
+  /**
+   * Returns the location of this event, if any.  Returns null iff the event
+   * wasn't associated with any particular location, for example, a progress
+   * message.
+   */
+  @Nullable public Location getLocation() {
+    return location;
+  }
+
+  /**
+   * Returns <i>some</i> moderately sane representation of the event. Should never be used in
+   * user-visible places, only for debugging and testing.
+   */
+  @Override
+  public String toString() {
+    return kind + " " + (location != null ? location.print() : "<no location>") + ": "
+        + getMessage();
+  }
+
+  /**
+   * Replay a sequence of events on an {@link EventHandler}.
+   */
+  public static void replayEventsOn(EventHandler eventHandler, Iterable<Event> events) {
+    for (Event event : events) {
+      eventHandler.handle(event);
+    }
+  }
+
+  /**
+   * Reports a warning.
+   */
+  public static Event warn(Location location, String message) {
+    return new Event(EventKind.WARNING, location, message);
+  }
+
+  /**
+   * Reports an error.
+   */
+  public static Event error(Location location, String message){
+    return new Event(EventKind.ERROR, location, message);
+  }
+
+  /**
+   * Reports atemporal statements about the build, i.e. they're true for the duration of execution.
+   */
+  public static Event info(Location location, String message) {
+    return new Event(EventKind.INFO, location, message);
+  }
+
+  /**
+   * Reports a temporal statement about the build.
+   */
+  public static Event progress(Location location, String message) {
+    return new Event(EventKind.PROGRESS, location, message);
+  }
+
+  /**
+   * Reports a warning.
+   */
+  public static Event warn(String message) {
+    return warn(null, message);
+  }
+
+  /**
+   * Reports an error.
+   */
+  public static Event error(String message){
+    return error(null, message);
+  }
+
+  /**
+   * Reports atemporal statements about the build, i.e. they're true for the duration of execution.
+   */
+  public static Event info(String message) {
+    return info(null, message);
+  }
+
+  /**
+   * Reports a temporal statement about the build.
+   */
+  public static Event progress(String message) {
+    return progress(null, message);
+  }
+
+}