1 files changed, 177 insertions, 0 deletions
diff --git a/api/src/main/java/io/opencensus/stats/Measure.java b/api/src/main/java/io/opencensus/stats/Measure.java
new file mode 100644
index 00000000..2de7fd70
--- /dev/null
+++ b/api/src/main/java/io/opencensus/stats/Measure.java
@@ -0,0 +1,177 @@
+/*
+ * Copyright 2017, OpenCensus Authors
+ *
+ * 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 io.opencensus.stats;
+
+import com.google.auto.value.AutoValue;
+import io.opencensus.common.Function;
+import io.opencensus.internal.DefaultVisibilityForTesting;
+import io.opencensus.internal.StringUtils;
+import io.opencensus.internal.Utils;
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * The definition of the {@link Measurement} that is taken by OpenCensus library.
+ *
+ * @since 0.8
+ */
+@Immutable
+public abstract class Measure {
+  @DefaultVisibilityForTesting static final int NAME_MAX_LENGTH = 255;
+  private static final String ERROR_MESSAGE_INVALID_NAME =
+      "Name should be a ASCII string with a length no greater than "
+          + NAME_MAX_LENGTH
+          + " characters.";
+
+  /**
+   * Applies the given match function to the underlying data type.
+   *
+   * @since 0.8
+   */
+  public abstract <T> T match(
+      Function<? super MeasureDouble, T> p0,
+      Function<? super MeasureLong, T> p1,
+      Function<? super Measure, T> defaultFunction);
+
+  /**
+   * Name of measure, as a {@code String}. Should be a ASCII string with a length no greater than
+   * 255 characters.
+   *
+   * <p>Suggested format for name: {@code <web_host>/<path>}.
+   *
+   * @since 0.8
+   */
+  public abstract String getName();
+
+  /**
+   * Detailed description of the measure, used in documentation.
+   *
+   * @since 0.8
+   */
+  public abstract String getDescription();
+
+  /**
+   * The units in which {@link Measure} values are measured.
+   *
+   * <p>The suggested grammar for a unit is as follows:
+   *
+   * <ul>
+   *   <li>Expression = Component { "." Component } {"/" Component };
+   *   <li>Component = [ PREFIX ] UNIT [ Annotation ] | Annotation | "1";
+   *   <li>Annotation = "{" NAME "}" ;
+   * </ul>
+   *
+   * <p>For example, string “MBy{transmitted}/ms” stands for megabytes per milliseconds, and the
+   * annotation transmitted inside {} is just a comment of the unit.
+   *
+   * @since 0.8
+   */
+  // TODO(songya): determine whether we want to check the grammar on string unit.
+  public abstract String getUnit();
+
+  // Prevents this class from being subclassed anywhere else.
+  private Measure() {}
+
+  /**
+   * {@link Measure} with {@code Double} typed values.
+   *
+   * @since 0.8
+   */
+  @Immutable
+  @AutoValue
+  public abstract static class MeasureDouble extends Measure {
+
+    MeasureDouble() {}
+
+    /**
+     * Constructs a new {@link MeasureDouble}.
+     *
+     * @param name name of {@code Measure}. Suggested format: {@code <web_host>/<path>}.
+     * @param description description of {@code Measure}.
+     * @param unit unit of {@code Measure}.
+     * @return a {@code MeasureDouble}.
+     * @since 0.8
+     */
+    public static MeasureDouble create(String name, String description, String unit) {
+      Utils.checkArgument(
+          StringUtils.isPrintableString(name) && name.length() <= NAME_MAX_LENGTH,
+          ERROR_MESSAGE_INVALID_NAME);
+      return new AutoValue_Measure_MeasureDouble(name, description, unit);
+    }
+
+    @Override
+    public <T> T match(
+        Function<? super MeasureDouble, T> p0,
+        Function<? super MeasureLong, T> p1,
+        Function<? super Measure, T> defaultFunction) {
+      return p0.apply(this);
+    }
+
+    @Override
+    public abstract String getName();
+
+    @Override
+    public abstract String getDescription();
+
+    @Override
+    public abstract String getUnit();
+  }
+
+  /**
+   * {@link Measure} with {@code Long} typed values.
+   *
+   * @since 0.8
+   */
+  @Immutable
+  @AutoValue
+  public abstract static class MeasureLong extends Measure {
+
+    MeasureLong() {}
+
+    /**
+     * Constructs a new {@link MeasureLong}.
+     *
+     * @param name name of {@code Measure}. Suggested format: {@code <web_host>/<path>}.
+     * @param description description of {@code Measure}.
+     * @param unit unit of {@code Measure}.
+     * @return a {@code MeasureLong}.
+     * @since 0.8
+     */
+    public static MeasureLong create(String name, String description, String unit) {
+      Utils.checkArgument(
+          StringUtils.isPrintableString(name) && name.length() <= NAME_MAX_LENGTH,
+          ERROR_MESSAGE_INVALID_NAME);
+      return new AutoValue_Measure_MeasureLong(name, description, unit);
+    }
+
+    @Override
+    public <T> T match(
+        Function<? super MeasureDouble, T> p0,
+        Function<? super MeasureLong, T> p1,
+        Function<? super Measure, T> defaultFunction) {
+      return p1.apply(this);
+    }
+
+    @Override
+    public abstract String getName();
+
+    @Override
+    public abstract String getDescription();
+
+    @Override
+    public abstract String getUnit();
+  }
+}