// Copyright 2015 The Vanadium 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 io.v.android.v23.services.blessing;

import android.app.Activity;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;

import java.security.interfaces.ECPublicKey;

import io.v.android.v23.V;
import io.v.android.impl.google.services.blessing.BlessingActivity;
import io.v.v23.context.VContext;

/**
 * Provides client methods for talking to the android
 * {@link io.v.android.impl.google.services.blessing.BlessingActivity BlessingService}.
 */
public class BlessingService {
    public static final String EXTRA_ERROR = "ERROR";
    public static final String EXTRA_REPLY = "REPLY";
    public static final String EXTRA_PUBLIC_KEY = "PUBLIC_KEY";
    public static final String EXTRA_GOOGLE_ACCOUNT = "GOOGLE_ACCOUNT";

    private static final String ACCOUNT_MANAGER_PACKAGE_NAME = "io.v.android.apps.account_manager";

    /**
     * Returns the intent used for obtaining a fresh set of credentials from the
     * vanadium blessing service.
     *
     * @param ctx            android context
     * @param googleAccount  google account name to use as the basis of the newly minted credentials
     *                       (e.g., {@code myname@mymail.com}).  If empty or {@code null}, user
     *                       will be prompted to select one from the list of installed Google
     *                       accounts
     */
    public static Intent newBlessingIntent(Context ctx, String googleAccount) {
        VContext vCtx = V.init(ctx);
        ECPublicKey key = V.getPrincipal(vCtx).publicKey();
        Intent intent = null;
        if (isAccountManagerInstalled(ctx)) {
            // Get blessings from the account manager installed on the device.
            intent = new Intent();
            intent.setComponent(new ComponentName(ACCOUNT_MANAGER_PACKAGE_NAME,
                    ACCOUNT_MANAGER_PACKAGE_NAME + ".LocalBlessingActivity"));
        } else {
            // Get blessings from the blessing service.
            intent = new Intent(ctx, BlessingActivity.class);
            intent.setAction("io.v.android.x.ref.services.blessing.BLESSING");
        }
        intent.putExtra(EXTRA_PUBLIC_KEY, key);
        intent.putExtra(EXTRA_GOOGLE_ACCOUNT, googleAccount);
        return intent;
    }

    /**
     * Same as {@link #newBlessingIntent(Context, String)}, but without the explicit Google
     * account name: the user will be prompted to select one from the list of installed Google
     * accounts.
     *
     * @param ctx          android context
     */
    public static Intent newBlessingIntent(Context ctx) {
        return newBlessingIntent(ctx, "");
    }

    /**
     * Processes the reply from the vanadium blessing serves generated by the
     * {@link #newBlessingIntent} intent, returning the credentials stored within.
     *
     * @param  resultCode                result code of the reply
     * @param  data                      reply data
     * @return                           the credentials stored in the reply
     * @throws BlessingCreationException if there was an error generating the credentials
     */
    public static byte[] extractBlessingReply(int resultCode, Intent data)
            throws BlessingCreationException {
        if (data == null) {
            throw new BlessingCreationException("NULL blessing response");
        }
        if (resultCode != Activity.RESULT_OK) {
            throw new BlessingCreationException("Error getting blessing: " + data.getStringExtra(EXTRA_ERROR));
        }
        byte[] blessingsVom = data.getByteArrayExtra(EXTRA_REPLY);
        if (blessingsVom == null || blessingsVom.length <= 0) {
            throw new BlessingCreationException("Got null blessings.");
        }
        return blessingsVom;
    }

    private static boolean isAccountManagerInstalled(Context ctx) {
        PackageManager pm = ctx.getPackageManager();
        try {
            pm.getPackageInfo(ACCOUNT_MANAGER_PACKAGE_NAME, PackageManager.GET_ACTIVITIES);
            return true;
        } catch (PackageManager.NameNotFoundException e) {
            return false;
        }
    }

    private BlessingService() {}
}