Set User-Agent and Accept-Language request headers for PWS requests

chrome/android/java/src/org/chromium/chrome/browser/physicalweb/PwsClientImpl.java

Index: chrome/android/java/src/org/chromium/chrome/browser/physicalweb/PwsClientImpl.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/physicalweb/PwsClientImpl.java b/chrome/android/java/src/org/chromium/chrome/browser/physicalweb/PwsClientImpl.java
index 20f0a611a287ed7e51c1a3c3d7a6c8507f0b204c..51a76f543bc3e808aa13d5031c501fdb2f6c2618 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/physicalweb/PwsClientImpl.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/physicalweb/PwsClientImpl.java
@@ -4,12 +4,16 @@
 
 package org.chromium.chrome.browser.physicalweb;
 
+import android.content.Context;
 import android.graphics.Bitmap;
 import android.os.AsyncTask;
+import android.os.Build;
 
 import org.chromium.base.Log;
 import org.chromium.base.ThreadUtils;
+import org.chromium.base.VisibleForTesting;
 import org.chromium.chrome.GoogleAPIKeys;
+import org.chromium.chrome.R;
 import org.chromium.chrome.browser.ChromeVersionInfo;
 import org.chromium.chrome.browser.physicalweb.PwsClient.FetchIconCallback;
 import org.chromium.chrome.browser.physicalweb.PwsClient.ResolveScanCallback;
@@ -21,6 +25,8 @@ import org.json.JSONObject;
 import java.net.MalformedURLException;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Formatter;
+import java.util.Locale;
 
 /**
  * This class sends requests to the Physical Web Service.
@@ -30,6 +36,30 @@ class PwsClientImpl implements PwsClient {
     private static final String ENDPOINT_URL =
             "https://physicalweb.googleapis.com/v1alpha1/urls:resolve";
 
+    // Format strings for creating the User-Agent string. It should somewhat resemble the Chrome for
+    // Android User-Agent but doesn't need to match perfectly as this value will only be seen by the
+    // Physical Web metadata service and favicon fetcher.
+    // The WebKit version is not accessible from here so it is reported as 0.0.
+    private static final String USER_AGENT_FORMAT =
+            "Mozilla/5.0 (%s) AppleWebKit/0.0 (KHTML, like Gecko) %s Safari/0.0";
+    private static final String OS_INFO_FORMAT = "Linux; Android %s; %s Build/%s";
+    private static final String PRODUCT_FORMAT = "Chrome/%s Mobile";
+
+    // HTTP request header strings, lazily initialized.
+    private static String sUserAgent;
+    private static String sAcceptLanguage;
+
+    // Cached locale string. When the default locale changes, recreate the Accept-Language header.
+    private static String sDefaultLocale;
+
+    // The context must be valid for as long as this client is in use, since it is used to recreate
+    // the Accept-Language header when the locale changes.
+    private final Context mContext;
+
+    public PwsClientImpl(Context context) {
+        mContext = context;
+    }
+
     private String getApiKey() {
         if (ChromeVersionInfo.isStableBuild()) {
             return GoogleAPIKeys.GOOGLE_API_KEY;
@@ -117,7 +147,8 @@ class PwsClientImpl implements PwsClient {
         try {
             JSONObject payload = createResolveScanPayload(broadcastUrls);
             String url = ENDPOINT_URL + "?key=" + getApiKey();
-            request = new JsonObjectHttpRequest(url, payload, requestCallback);
+            request = new JsonObjectHttpRequest(url, getUserAgent(), getAcceptLanguage(), payload,
+                    requestCallback);
         } catch (MalformedURLException e) {
             Log.e(TAG, "Error creating PWS HTTP request", e);
             return;
@@ -159,7 +190,8 @@ class PwsClientImpl implements PwsClient {
         // Create the request.
         BitmapHttpRequest request = null;
         try {
-            request = new BitmapHttpRequest(iconUrl, requestCallback);
+            request = new BitmapHttpRequest(iconUrl, getUserAgent(), getAcceptLanguage(),
+                    requestCallback);
         } catch (MalformedURLException e) {
             Log.e(TAG, "Error creating icon request", e);
             return;
@@ -167,4 +199,135 @@ class PwsClientImpl implements PwsClient {
         // The callback will be called on the main thread.
         AsyncTask.THREAD_POOL_EXECUTOR.execute(request);
     }
+
+    /**
+     * Recreate the Chrome for Android User-Agent string as closely as possible without calling any
+     * native code.
+     * @return A User-Agent string
+     */
+    @VisibleForTesting
+    String getUserAgent() {
+        if (sUserAgent == null) {
+            // Build the OS info string.
+            // eg: Linux; Android 5.1.1; Nexus 4 Build/LMY48T
+            String osInfo = String.format(OS_INFO_FORMAT, Build.VERSION.RELEASE, Build.MODEL,
+                    Build.ID);
+
+            // Build the product string.
+            // eg: Chrome/50.0.2661.89 Mobile
+            String product = String.format(PRODUCT_FORMAT, ChromeVersionInfo.getProductVersion());
+
+            // Build the User-Agent string.
+            // eg: Mozilla/5.0 (Linux; Android 5.1.1; Nexus 4 Build/LMY48T) AppleWebKit/0.0 (KHTML,
+            //     like Gecko) Chrome/50.0.2661.89 Mobile Safari/0.0
+            sUserAgent = String.format(USER_AGENT_FORMAT, osInfo, product);
+        }
+        return sUserAgent;
+    }
+
+    /**
+     * Construct the Accept-Language string based on the current locale.
+     * @return An Accept-Language string.
+     */
+    @VisibleForTesting
+    String getAcceptLanguage() {
+        String defaultLocale = Locale.getDefault().toString();
+        if (sDefaultLocale == null || !sDefaultLocale.equals(defaultLocale)) {
+            String acceptLanguages = mContext.getResources().getString(R.string.accept_languages);
+            acceptLanguages = prependToAcceptLanguagesIfNecessary(defaultLocale, acceptLanguages);
+            sAcceptLanguage = generateAcceptLanguageHeader(acceptLanguages);
+            sDefaultLocale = defaultLocale;
+        }
+        return sAcceptLanguage;
+    }
+
+    /**
+     * Handle the special cases in converting a language code/region code pair into an ISO-639-1
+     * language tag.
+     * @param language The 2-character language code
+     * @param region The 2-character country code
+     * @return A language tag.
+     */
+    @VisibleForTesting
+    static String makeLanguageTag(String language, String region) {
+        // Java mostly follows ISO-639-1 and ICU, except for the following three.
+        // See documentation on java.util.Locale constructor for more.
+        String isoLanguage;
+        if ("iw".equals(language)) {
+            isoLanguage = "he";
+        } else if ("ji".equals(language)) {
+            isoLanguage = "yi";
+        } else if ("in".equals(language)) {
+            isoLanguage = "id";
+        } else {
+            isoLanguage = language;
+        }
+
+        return isoLanguage + "-" + region;
+    }
+
+    /**
+     * Get the language code for the default locale and prepend it to the Accept-Language string if
+     * it isn't already present. The logic should match PrependToAcceptLanguagesIfNecessary in
+     * chrome/browser/android/preferences/pref_service_bridge.cc
+     * @param locale A string representing the default locale.
+     * @param acceptLanguages The default language list for the language of the user's locale.
+     * @return An updated language list.
+     */
+    @VisibleForTesting
+    static String prependToAcceptLanguagesIfNecessary(String locale, String acceptLanguages)
+    {
+        if (locale.length() != 5 || locale.charAt(2) != '_') {
+            return acceptLanguages;
+        }
+
+        String language = locale.substring(0, 2);
+        String region = locale.substring(3);
+        String languageTag = makeLanguageTag(language, region);
+
+        if (acceptLanguages.contains(languageTag)) {
+            return acceptLanguages;
+        }
+
+        Formatter parts = new Formatter();
+        parts.format("%s,", languageTag);
+        // If language is not in the accept languages list, also add language code.
+        // This will work with the IDS_ACCEPT_LANGUAGES localized strings bundled with Chrome but
+        // may fail on arbitrary lists of language tags due to differences in case and whitespace.
+        if (!acceptLanguages.contains(language + ",") && !acceptLanguages.endsWith(language)) {
+            parts.format("%s,", language);
+        }
+        parts.format("%s", acceptLanguages);
+        return parts.toString();
+    }
+
+    /**
+     * Given a list of comma-delimited language codes in decreasing order of preference, insert
+     * q-values to represent the relative quality/precedence of each language. The logic should
+     * match GenerateAcceptLanguageHeader in net/http/http_util.cc.
+     * @param languageList A comma-delimited list of language codes containing no whitespace.
+     * @return An Accept-Language header with q-values.
+     */
+    @VisibleForTesting
+    static String generateAcceptLanguageHeader(String languageList) {
+        // We use integers for qvalue and qvalue decrement that are 10 times larger than actual
+        // values to avoid a problem with comparing two floating point numbers.
+        int kQvalueDecrement10 = 2;
+        int qvalue10 = 10;
+        String[] parts = languageList.split(",");
+        Formatter langListWithQ = new Formatter();
+        for (String language : parts) {
+            if (qvalue10 == 10) {
+                // q=1.0 is implicit
+                langListWithQ.format("%s", language);
+            } else {
+                langListWithQ.format(",%s;q=0.%d", language, qvalue10);
+            }
+            // It does not make sense to have 'q=0'.
+            if (qvalue10 > kQvalueDecrement10) {
+                qvalue10 -= kQvalueDecrement10;
+            }
+        }
+        return langListWithQ.toString();
+    }
 }