/*  Copyright (C) 2016-2024 Andreas Shimokawa, Carsten Pfeiffer, Daniele
    Gobbetti, José Rebelo, Taavi Eomäe

    This file is part of Gadgetbridge.

    Gadgetbridge is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as published
    by the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    Gadgetbridge is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>. */
package nodomain.freeyourgadget.gadgetbridge.util;

import android.app.Activity;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.MutableContextWrapper;
import android.content.ServiceConnection;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
import android.os.IBinder;
import android.os.Looper;
import android.os.Message;
import android.os.Messenger;
import android.os.RemoteException;
import android.webkit.WebResourceResponse;
import android.webkit.WebSettings;
import android.webkit.WebView;

import androidx.annotation.NonNull;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.ByteArrayInputStream;
import java.nio.charset.Charset;
import java.util.HashMap;
import java.util.Map;
import java.util.UUID;
import java.util.concurrent.CountDownLatch;

import nodomain.freeyourgadget.gadgetbridge.impl.GBDevice;
import nodomain.freeyourgadget.gadgetbridge.service.devices.pebble.webview.GBChromeClient;
import nodomain.freeyourgadget.gadgetbridge.service.devices.pebble.webview.GBWebClient;
import nodomain.freeyourgadget.gadgetbridge.service.devices.pebble.webview.JSInterface;

public class WebViewSingleton {

    private static final Logger LOG = LoggerFactory.getLogger(WebViewSingleton.class);
    private static final WebViewSingleton instance = new WebViewSingleton();

    private WebView webView = null;
    private MutableContextWrapper contextWrapper;
    private Looper mainLooper;
    private UUID currentRunningUUID;
    private Messenger internetHelper = null;
    public boolean internetHelperBound;
    private boolean internetHelperInstalled;
    private CountDownLatch latch;
    private WebResourceResponse internetResponse;
    private Messenger internetHelperListener;

    private WebViewSingleton() {
    }

    //Internet helper outgoing connection
    private final ServiceConnection internetHelperConnection = new ServiceConnection() {
        public void onServiceConnected(ComponentName className, IBinder service) {
            LOG.info("internet helper service bound");
            internetHelperBound = true;
            internetHelper = new Messenger(service);
        }

        public void onServiceDisconnected(ComponentName className) {
            LOG.info("internet helper service unbound");
            internetHelper = null;
            internetHelperBound = false;
        }
    };

    public static synchronized void ensureCreated(Activity context) {
        if (instance.webView == null) {
            instance.contextWrapper = new MutableContextWrapper(context);
            instance.mainLooper = context.getMainLooper();
            instance.webView = new WebView(instance.contextWrapper);
            WebView.setWebContentsDebuggingEnabled(true);
            instance.webView.setWillNotDraw(true);
            instance.webView.clearCache(true);
            instance.webView.setWebViewClient(new GBWebClient());
            instance.webView.setWebChromeClient(new GBChromeClient());
            WebSettings webSettings = instance.webView.getSettings();
            //noinspection SetJavaScriptEnabled
            webSettings.setJavaScriptEnabled(true);
            //needed to access the DOM
            webSettings.setDomStorageEnabled(true);
            //needed for localstorage
            webSettings.setDatabaseEnabled(true);
            // #3373 #3424 - Fix configuration for pebble apps
            // TODO: this should use a WebViewAssetLoader
            webSettings.setAllowFileAccess(true);
        }
    }

    public static WebViewSingleton getInstance() {
        return instance;
    }

    public WebResourceResponse send(Message webRequest) throws RemoteException, InterruptedException {
        webRequest.replyTo = internetHelperListener;
        latch = new CountDownLatch(1); //the messenger should run on a single thread, hence we don't need to be worried about concurrency. This approach however is certainly not ideal.
        internetHelper.send(webRequest);
        latch.await();
        return internetResponse;
    }

    //Internet helper inbound (responses) handler
    private class IncomingHandler extends Handler {

        private String getCharsetFromHeaders(String contentType) {
            if (contentType != null && contentType.toLowerCase().trim().contains("charset=")) {
                String[] parts = contentType.toLowerCase().trim().split("=");
                if (parts.length > 0)
                    return parts[1];
            }
            return null;
        }

        @Override
        public void handleMessage(Message msg) {
            Bundle data = msg.getData();
            LOG.debug("WEBVIEW: internet helper returned: " + data.getString("response"));
            Map<String, String> headers = new HashMap<>();
            headers.put("Access-Control-Allow-Origin", "*");

            internetResponse = new WebResourceResponse(data.getString("content-type"), data.getString("content-encoding"), 200, "OK",
                    headers,
                    new ByteArrayInputStream(data.getString("response").getBytes(Charset.forName(getCharsetFromHeaders(data.getString("content-type")))))
            );

            latch.countDown();
        }
    }

    @NonNull
    public WebView getWebView(Context context) {
        contextWrapper.setBaseContext(context);
        return webView;
    }

    /**
     * Checks that the webview is up and the given app is running.
     * @param uuid the uuid of the application expected to be running
     * @throws IllegalStateException when the webview is not active or the app is not running
     */
    public void checkAppRunning(@NonNull UUID uuid) {
        if (webView == null) {
            throw new IllegalStateException("instance.webView is null!");
        }
        if (!uuid.equals(currentRunningUUID)) {
            throw new IllegalStateException("Expected app " + uuid + " is not running, but " + currentRunningUUID + " is.");
        }
    }

    public void runJavascriptInterface(@NonNull Activity context, @NonNull GBDevice device, @NonNull UUID uuid) {
        ensureCreated(context);
        runJavascriptInterface(device, uuid);
    }

    public void runJavascriptInterface(@NonNull GBDevice device, @NonNull UUID uuid) {
        if (uuid.equals(currentRunningUUID)) {
            LOG.debug("WEBVIEW uuid not changed keeping the old context");
        } else {
            final JSInterface jsInterface = new JSInterface(device, uuid);
            LOG.debug("WEBVIEW uuid changed, restarting");
            currentRunningUUID = uuid;
            invokeWebview(new WebViewRunnable() {
                @Override
                public void invoke(WebView webView) {
                    webView.onResume();
                    webView.removeJavascriptInterface("GBjs");
                    webView.addJavascriptInterface(jsInterface, "GBjs");
                    webView.loadUrl("file:///android_asset/app_config/configure.html?rand=" + Math.random() * 500);
                }
            });
            if (contextWrapper != null && !internetHelperBound && !internetHelperInstalled) {
                String internetHelperPkg = "nodomain.freeyourgadget.internethelper";
                String internetHelperCls = internetHelperPkg + ".MyService";
                try {
                    contextWrapper.getPackageManager().getApplicationInfo(internetHelperPkg, 0);
                    Intent intent = new Intent();
                    intent.setComponent(new ComponentName(internetHelperPkg, internetHelperCls));
                    contextWrapper.getApplicationContext().bindService(intent, internetHelperConnection, Context.BIND_AUTO_CREATE);
                    internetHelperListener = new Messenger(new IncomingHandler());
                    internetHelperInstalled = true;
                }
                catch (PackageManager.NameNotFoundException e) {
                    internetHelperInstalled = false;
                    LOG.info("WEBVIEW: Internet helper not installed, only mimicked HTTP requests will work.");
                }
            }
        }
    }

    public void stopJavascriptInterface() {
        invokeWebview(new WebViewRunnable() {
            @Override
            public void invoke(WebView webView) {
                webView.removeJavascriptInterface("GBjs");
                webView.loadUrl("about:blank");
            }
        });
    }

    public void disposeWebView() {
        if (internetHelperBound) {
            LOG.debug("WEBVIEW: will unbind the internet helper");
            contextWrapper.getApplicationContext().unbindService(internetHelperConnection);
            internetHelperBound = false;
        }
        currentRunningUUID = null;
        invokeWebview(new WebViewRunnable() {
            @Override
            public void invoke(WebView webView) {
                webView.removeJavascriptInterface("GBjs");
//                    webView.setWebChromeClient(null);
//                    webView.setWebViewClient(null);
                webView.clearHistory();
                webView.clearCache(true);
                webView.loadUrl("about:blank");
//                    webView.freeMemory();
                webView.pauseTimers();
//                    webView.destroy();
//                    webView = null;
//                    contextWrapper = null;
//                    jsInterface = null;
            }
        });
    }

    public void invokeWebview(final WebViewRunnable runnable) {
        if (webView == null || mainLooper == null) {
            LOG.warn("Webview already disposed, ignoring runnable");
            return;
        }
        new Handler(mainLooper).post(new Runnable() {
            @Override
            public void run() {
                if (webView == null) {
                    LOG.warn("Webview already disposed, cannot invoke runnable");
                    return;
                }
                runnable.invoke(webView);
            }
        });
    }

    public interface WebViewRunnable {
        /**
         * Called in the main thread with a non-null webView webView
         * @param webView the webview, never null
         */
        void invoke(WebView webView);
    }
}