Move Java Blimp shell code to app subpackage

blimp/client/app/android/java/src/org/chromium/blimp/auth/RetryingTokenSource.java

-// 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.blimp.auth;
-
-import android.content.Intent;
-import android.os.Handler;
-import android.os.Message;
-
-import org.chromium.base.ThreadUtils;
-import org.chromium.base.VisibleForTesting;
-
-import java.util.Random;
-
-/**
- * Wraps an existing {@link TokenSource} and adds exponential fallback retry support to it.  The
- * underlying {@link TokenSource} will be queried and all calls will be proxied except transient
- * failures, which will cause a retry after a random exponentially increasing delay.
- *
- * Because callbacks to {@link TokenSource#Callback#onTokenUnavailable(boolean)} with
- * {@code isTransient} set to {@code true} will be captured here, this {@link TokenSource} currently
- * won't expose any transient errors to the caller.
- */
-public class RetryingTokenSource extends Handler implements TokenSource, TokenSource.Callback {
-    private static final int MSG_QUERY_TOKEN = 1;
-    private static final int BASE_BACKOFF_DELAY_MS = 500;
-    private static final int MAX_EXPONENT = 10;
-
-    private static final Random sRandom = new Random();
-
-    /** The maximum number of times to attempt connection before failing. */
-    @VisibleForTesting
-    public static final int MAX_NUMBER_OF_RETRIES = 8;
-
-    private final TokenSource mTokenSource;
-
-    private TokenSource.Callback mCallback;
-    private int mAttemptNumber;
-
-    /**
-     * Creates a {@link RetryingTokenSource} that proxies most {@link TokenSource} communication to
-     * {@code tokenSource}.
-     * @param tokenSource A {@link TokenSource} that does the actual underlying token management.
-     */
-    public RetryingTokenSource(TokenSource tokenSource) {
-        mTokenSource = tokenSource;
-        mTokenSource.setCallback(this);
-    }
-
-    // TokenSource implementation.
-    @Override
-    public void destroy() {
-        ThreadUtils.assertOnUiThread();
-
-        mTokenSource.destroy();
-        removeMessages(MSG_QUERY_TOKEN);
-    }
-
-    @Override
-    public void setCallback(TokenSource.Callback callback) {
-        ThreadUtils.assertOnUiThread();
-
-        mCallback = callback;
-    }
-
-    @Override
-    public void getToken() {
-        ThreadUtils.assertOnUiThread();
-
-        // Reset all exponential backoff states.
-        removeMessages(MSG_QUERY_TOKEN);
-        mAttemptNumber = 0;
-
-        // Start the TokenSource#getToken() exponential backoff calls.
-        getTokenWithBackoff();
-    }
-
-    @Override
-    public boolean isRetrievingToken() {
-        ThreadUtils.assertOnUiThread();
-
-        return mTokenSource.isRetrievingToken() || hasMessages(MSG_QUERY_TOKEN);
-    }
-
-    @Override
-    public int tokenIsInvalid(String token) {
-        ThreadUtils.assertOnUiThread();
-
-        return mTokenSource.tokenIsInvalid(token);
-    }
-
-    @Override
-    public void onAccountSelected(Intent data) {
-        ThreadUtils.assertOnUiThread();
-
-        mTokenSource.onAccountSelected(data);
-    }
-
-    // TokenSource.Callback implementation.
-    @Override
-    public void onTokenReceived(String token) {
-        mCallback.onTokenReceived(token);
-    }
-
-    @Override
-    public void onTokenUnavailable(boolean isTransient) {
-        if (isTransient && mAttemptNumber < MAX_NUMBER_OF_RETRIES) {
-            getTokenWithBackoff();
-        } else {
-            mCallback.onTokenUnavailable(false);
-        }
-    }
-
-    @Override
-    public void onNeedsAccountToBeSelected(Intent intent) {
-        mCallback.onNeedsAccountToBeSelected(intent);
-    }
-
-    // Handler overrides.
-    @Override
-    public void handleMessage(Message msg) {
-        if (msg.what != MSG_QUERY_TOKEN) return;
-        mTokenSource.getToken();
-    }
-
-    /**
-     * @param delay The suggested time (in ms) to wait before attempting to query for the token
-     *              again.
-     * @return      The actual time (in ms) to wait before attempting to query for a token again.
-     */
-    @VisibleForTesting
-    protected int finalizeRetryDelay(int delay) {
-        return delay;
-    }
-
-    private void getTokenWithBackoff() {
-        int delayMs = 0;
-
-        // For the first attempt, don't delay.
-        if (mAttemptNumber > 0) {
-            // Find a random value between the previous and current max delay values.
-            int prevMaxDelay = getMaxDelay(mAttemptNumber - 1);
-            int currMaxDelay = getMaxDelay(mAttemptNumber);
-
-            assert currMaxDelay > prevMaxDelay;
-            int delayWindow = currMaxDelay - prevMaxDelay;
-
-            delayMs = sRandom.nextInt(delayWindow) + prevMaxDelay;
-        }
-
-        sendEmptyMessageDelayed(MSG_QUERY_TOKEN, finalizeRetryDelay(delayMs));
-        mAttemptNumber++;
-    }
-
-    /**
-     * Helper method for calculating the max delay for any given attempt.
-     * @param attempt The current attempt at calling {@link TokenSource#getToken()} on the internal
-     *                {@link TokenSource}
-     * @return        The maximum possible delay (in ms) to use for this attempt.
-     */
-    private static int getMaxDelay(int attempt) {
-        // For the first attempt, use no delay.
-        if (attempt == 0) return 0;
-
-        // Figure out the delay multiplier 2^(retry attempt number).
-        int multiplier = 1 << Math.min(MAX_EXPONENT, attempt - 1);
-        return multiplier * BASE_BACKOFF_DELAY_MS;
-    }
-}