Add Android implementation of navigator.getInstalledRelatedApps.

content/public/android/java/src/org/chromium/content/browser/installedapp/InstalledAppProviderImpl.java

+// Copyright 2017 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.content.browser.installedapp;
+
+import android.content.Context;
+import android.content.pm.ApplicationInfo;
+import android.content.pm.PackageManager;
+import android.content.pm.PackageManager.NameNotFoundException;
+import android.content.res.Resources;
+
+import org.json.JSONArray;
+import org.json.JSONException;
+import org.json.JSONObject;
+
+import org.chromium.base.Log;
+import org.chromium.installedapp.mojom.InstalledAppProvider;
+import org.chromium.installedapp.mojom.RelatedApplication;
+import org.chromium.mojo.system.MojoException;
+
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.util.ArrayList;
+
+/**
+ * Android implementation of the InstalledAppProvider service defined in
+ * content/common/installedapp/installed_app_provider.mojom.

[boliu, 2017/03/17 18:02:55]

cs says this is in third_party/WebKit?

[Matt Giuca, 2017/03/20 06:31:56]

Done. (Removed the full path, because otherwise there is no guarantee it won't
go out of date as WebKit paths are moved around.)

+ */
+public class InstalledAppProviderImpl implements InstalledAppProvider {
+    private static final String ASSET_STATEMENTS_KEY = "asset_statements";
+    private static final String ASSET_STATEMENT_FIELD_TARGET = "target";
+    private static final String ASSET_STATEMENT_FIELD_NAMESPACE = "namespace";
+    private static final String ASSET_STATEMENT_FIELD_SITE = "site";
+    private static final String ASSET_STATEMENT_NAMESPACE_WEB = "web";
+    private static final String RELATED_APP_PLATFORM_ANDROID = "play";
+
+    private static final String TAG = "InstalledAppProvider";
+
+    private final Context mContext;
+    private final URI mPageUrl;
+
+    public InstalledAppProviderImpl(String pageUrl, Context context) {
+        mContext = context;
+
+        try {
+            mPageUrl = new URI(pageUrl);
+        } catch (URISyntaxException e) {
+            throw new AssertionError(e);
+        }
+    }
+
+    @Override
+    public void filterInstalledApps(
+            RelatedApplication[] relatedApps, FilterInstalledAppsResponse callback) {
+        ArrayList<RelatedApplication> installedApps = new ArrayList<RelatedApplication>();
+        PackageManager pm = mContext.getPackageManager();
+        for (RelatedApplication app : relatedApps) {
+            // If the package is of type "play", it is installed, and the origin is associated with
+            // package, add the package to the list of valid packages.
+            // NOTE: For security, it must not be possible to distinguish (from the response)
+            // between the app not being installed and the origin not being associated with the app
+            // (otherwise, arbitrary websites would be able to test whether un-associated apps are
+            // installed on the user's device).
+            if (app.platform.equals(RELATED_APP_PLATFORM_ANDROID) && app.id != null

[boliu, 2017/03/17 18:02:55]

A nit that reversing the equals call is safer since it also works when
app.platform is null as well. I think mojo guarantees platform is never null
though?

Same nit on the ASSET_STATEMENT_FIELD_NAMESPACE comparison below

[Matt Giuca, 2017/03/20 06:31:56]

Yes, Mojo guarantees platform is not null as it is not optional in the
declaration. That's also why there is no test for platform being null (while
there are tests for the other two fields).

I think I would rather leave it like this because it should not be null and
Chrome is supposed to crash when things that shouldn't happen happen.

Same goes for the namespace comparison below.

+                    && isAppInstalledAndAssociatedWithOrigin(app.id, mPageUrl, pm)) {
+                installedApps.add(app);
+            }
+        }
+        RelatedApplication[] installedAppsArray = new RelatedApplication[installedApps.size()];
+        installedApps.toArray(installedAppsArray);
+        callback.call(installedAppsArray);
+    }
+
+    @Override
+    public void close() {}
+
+    @Override
+    public void onConnectionError(MojoException e) {}
+
+    /**
+     * Determines whether a particular app is installed and matches the origin.
+     *
+     * @param packageName Name of the Android package to check if installed. Returns false if the
+     *                    app is not installed.
+     * @param pageUrl Returns false if the Android package does not declare association with the
+     *                origin of this URL.
+     */
+    private static boolean isAppInstalledAndAssociatedWithOrigin(
+            String packageName, URI pageUrl, PackageManager pm) {
+        // Early-exit if the Android app is not installed.
+        JSONArray statements;
+        try {
+            statements = getAssetStatements(packageName, pm);
+        } catch (NameNotFoundException e) {
+            return false;
+        }
+
+        // The installed Android app has provided us with a list of asset statements. If any one of
+        // those statements is a web asset that matches the given origin, return true.
+        for (int i = 0; i < statements.length(); i++) {
+            JSONObject statement;
+            try {
+                statement = statements.getJSONObject(i);
+            } catch (JSONException e) {
+                // If an element is not an object, just ignore it.
+                continue;
+            }
+
+            URI site = getSiteForWebAsset(statement);
+
+            // The URI is considered equivalent if the scheme, host, and port match, according
+            // to the DigitalAssetLinks v1 spec.
+            if (site != null && statementTargetMatches(pageUrl, site)) {
+                return true;
+            }
+        }
+
+        // No asset matched the origin.
+        return false;
+    }
+
+    /**
+     * Gets the asset statements from an Android app's manifest.
+     *
+     * This retrieves the list of statements from the Android app's "asset_statements" manifest
+     * resource, as specified in Digital Asset Links v1.
+     *
+     * @param packageName Name of the Android package to get statements from.
+     * @return The list of asset statements, parsed from JSON.
+     * @throws NameNotFoundException if the application is not installed.
+     */
+    private static JSONArray getAssetStatements(String packageName, PackageManager pm)
+            throws NameNotFoundException {
+        // Get the <meta-data> from this app's manifest.
+        // Throws NameNotFoundException if the application is not installed.
+        ApplicationInfo appInfo = pm.getApplicationInfo(packageName, PackageManager.GET_META_DATA);
+        int identifier = appInfo.metaData.getInt(ASSET_STATEMENTS_KEY);
+        if (identifier == 0) {
+            return new JSONArray();
+        }
+
+        // Throws NameNotFoundException in the rare case that the application was uninstalled since
+        // getting |appInfo| (or resources could not be loaded for some other reason).
+        Resources resources = pm.getResourcesForApplication(appInfo);
+
+        String statements;
+        try {
+            statements = resources.getString(identifier);
+        } catch (Resources.NotFoundException e) {
+            // This should never happen, but it could if there was a broken APK, so handle it
+            // gracefully without crashing.
+            Log.w(TAG,
+                    "Android package " + packageName + " missing asset statements resource (0x"
+                            + Integer.toHexString(identifier) + ").");
+            return new JSONArray();
+        }
+
+        try {
+            return new JSONArray(statements);
+        } catch (JSONException e) {
+            // If the JSON is invalid or not an array, assume it is empty.
+            Log.w(TAG,
+                    "Android package " + packageName
+                            + " has JSON syntax error in asset statements resource (0x"
+                            + Integer.toHexString(identifier) + ").");
+            return new JSONArray();
+        }
+    }
+
+    /**
+     * Gets the "site" URI from an Android asset statement.
+     *
+     * @return The site, or null if the asset string was invalid or not related to a web site. This
+     *         could be because: the JSON string was invalid, there was no "target" field, this was
+     *         not a web asset, there was no "site" field, or the "site" field was invalid.
+     */
+    private static URI getSiteForWebAsset(JSONObject statement) {
+        JSONObject target;
+        try {
+            // Ignore the "relation" field and allow an asset with any relation to this origin.
+            // TODO(mgiuca): [Spec issue] Should we require a specific relation string, rather
+            // than any or no relation?
+            target = statement.getJSONObject(ASSET_STATEMENT_FIELD_TARGET);
+        } catch (JSONException e) {
+            return null;
+        }
+
+        // If it is not a web asset, skip it.
+        if (!isAssetWeb(target)) {
+            return null;
+        }
+
+        try {
+            return new URI(target.getString(ASSET_STATEMENT_FIELD_SITE));
+        } catch (JSONException e) {

[boliu, 2017/03/17 18:02:56]

nit: you can do "JSONException | URISyntaxException e" I think

[Matt Giuca, 2017/03/20 06:31:56]

Done.

Nice, I didn't know that.

+            return null;
+        } catch (URISyntaxException e) {
+            return null;
+        }
+    }
+
+    /**
+     * Determines whether an Android asset statement is for a website.
+     *
+     * @param target The "target" field of the asset statement.
+     */
+    private static boolean isAssetWeb(JSONObject target) {
+        String namespace;
+        try {
+            namespace = target.getString(ASSET_STATEMENT_FIELD_NAMESPACE);
+        } catch (JSONException e) {
+            return false;
+        }
+
+        return namespace.equals(ASSET_STATEMENT_NAMESPACE_WEB);
+    }
+
+    private static boolean statementTargetMatches(URI pageUrl, URI assetUrl) {
+        if (assetUrl.getScheme() == null || assetUrl.getAuthority() == null) {
+            return false;
+        }
+
+        return assetUrl.getScheme().equals(pageUrl.getScheme())
+                && assetUrl.getAuthority().equals(pageUrl.getAuthority());
+    }
+}