[PresentationAPI,Android] Implement the ChromeMediaRouterDialogController.

chrome/android/java/src/org/chromium/chrome/browser/media/router/cast/MediaSource.java

Index: chrome/android/java/src/org/chromium/chrome/browser/media/router/cast/MediaSource.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/media/router/cast/MediaSource.java b/chrome/android/java/src/org/chromium/chrome/browser/media/router/cast/MediaSource.java
new file mode 100644
index 0000000000000000000000000000000000000000..0e1576fb3e5c7d92bffd2d1442aa958de2260e80
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/media/router/cast/MediaSource.java
@@ -0,0 +1,76 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.media.router.cast;
+
+import android.support.v7.media.MediaRouteSelector;
+
+import com.google.android.gms.cast.CastMediaControlIntent;
+
+import java.util.Locale;
+
+import javax.annotation.Nullable;
+
+/**
+ * Abstracts parsing the Cast application id and other parameters from the source URN.
+ */
+public class MediaSource {
+    private static final String CAST_SOURCE_URN_PREFIX = "https://google.com/cast#";
+    private static final String CAST_SOURCE_URN_PARAMETER_SEPARATOR = "/";
+    private static final String CAST_SOURCE_URN_APPLICATION_ID_PREFIX = "__castappid__=";
+
+    private String mApplicationId;
+
+    /**
+     * Initializes the media source from its source URN.
+     * @param sourceUrn the source urn for the Cast media source
+     * @return an initialized media source if the URN is valid or null.
+     */
+    @Nullable
+    public static MediaSource from(String sourceUrn) {
+        String applicationId = getCastApplicationId(sourceUrn);
+        if (applicationId == null) return null;
+        return new MediaSource(applicationId);
+    }
+
+    /**
+     * Returns a new {@link MediaRouteSelector} to use for Cast device filtering for this
+     * particular media source.
+     * @return an initialized route selector.
+     */
+    public MediaRouteSelector buildRouteSelector() {
+        return new MediaRouteSelector.Builder()
+                .addControlCategory(CastMediaControlIntent.categoryForCast(mApplicationId))
+                .build();
+    }
+
+    private MediaSource(String applicationId) {
+        mApplicationId = applicationId;
+    }
+
+    /**
+     * @param sourceUrn the URN identifying the media source.
+     * @return the corresponding Cast application id or null.
+     */
+    @Nullable
+    private static String getCastApplicationId(String sourceUrn) {
+        String canonicalSourceUrn = null;
+        if (sourceUrn != null) canonicalSourceUrn = sourceUrn.trim().toLowerCase(Locale.US);
+        if (canonicalSourceUrn == null
+                || !canonicalSourceUrn.startsWith(CAST_SOURCE_URN_PREFIX)) {
+            return null;
+        }
+        String[] parameters = canonicalSourceUrn
+                .substring(CAST_SOURCE_URN_PREFIX.length())
+                .split(CAST_SOURCE_URN_PARAMETER_SEPARATOR);
+        for (String parameter : parameters) {
+            if (parameter.startsWith(CAST_SOURCE_URN_APPLICATION_ID_PREFIX)) {
+                String applicationId = parameter.substring(
+                        CAST_SOURCE_URN_APPLICATION_ID_PREFIX.length()).toUpperCase(Locale.US);
+                if (!applicationId.isEmpty()) return applicationId;
+            }
+        }
+        return null;
+    }
+}