package net.ME1312.SubServers.Client.Sponge.Library;

import com.google.gson.JsonArray;
import com.google.gson.JsonObject;
import com.google.inject.Inject;
import net.ME1312.SubServers.Client.Sponge.SubPlugin;
import ninja.leaping.configurate.commented.CommentedConfigurationNode;
import ninja.leaping.configurate.hocon.HoconConfigurationLoader;
import org.apache.commons.lang3.Validate;
import org.slf4j.Logger;
import org.spongepowered.api.Sponge;
import org.spongepowered.api.scheduler.Scheduler;
import org.spongepowered.api.scheduler.Task;

import javax.net.ssl.HttpsURLConnection;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.net.URL;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.List;
import java.util.Timer;
import java.util.TimerTask;
import java.util.UUID;
import java.util.zip.GZIPOutputStream;

/**
 * bStats collects some data for plugin authors.
 *
 * Check out https://bStats.org/ to learn more about bStats!
 */
public class Metrics {

    static {
        // You can use the property to disable the check in your test environment
        if (System.getProperty("bstats.relocatecheck") == null || !System.getProperty("bstats.relocatecheck").equals("false")) {
            // Maven's Relocate is clever and changes strings, too. So we have to use this little "trick" ... :D
            final String defaultPackage = new String(
                    new byte[]{'o', 'r', 'g', '.', 'b', 's', 't', 'a', 't', 's', '.', 's', 'p', 'o', 'n', 'g', 'e'});
            final String examplePackage = new String(new byte[]{'y', 'o', 'u', 'r', '.', 'p', 'a', 'c', 'k', 'a', 'g', 'e'});
            // We want to make sure nobody just copy & pastes the example and use the wrong package names
            if (Metrics.class.getPackage().getName().equals(defaultPackage) || Metrics.class.getPackage().getName().equals(examplePackage)) {
                throw new IllegalStateException("bStats Metrics class has not been relocated correctly!");
            }
        }
    }

    // The version of this bStats class
    public static final int B_STATS_VERSION = 1;

    // The url to which the data is sent
    private static final String URL = "https://bStats.org/submitData/sponge";

    // We use this flag to ensure only one instance of this class exist
    private static boolean created = false;

    // The logger
    private Logger logger;

    // The plugin
    private final SubPlugin plugin;

    // Is bStats enabled on this server?
    private boolean enabled;

    // The uuid of the server
    private String serverUUID;

    // Should failed requests be logged?
    private boolean logFailedRequests = false;

    // A list with all known metrics class objects including this one
    private static final List<Object> knownMetricsInstances = new ArrayList<>();

    // The config path
    private Path configDir;

    @Inject
    public Metrics(SubPlugin plugin) {
        if (created) {
            // We don't want more than one instance of this class
            throw new IllegalStateException("There's already an instance of this Metrics class!");
        } else {
            created = true;
        }

        this.plugin = plugin;
        this.logger = plugin.log;
        this.configDir = plugin.dir.getParentFile().toPath();

        try {
            loadConfig();
        } catch (IOException e) {
            // Failed to load configuration
            logger.warn("Failed to load bStats config!", e);
            return;
        }

        // We are not allowed to send data about this server :(
        if (!enabled) {
            return;
        }

        Class<?> usedMetricsClass = getFirstBStatsClass();
        if (usedMetricsClass == null) {
            // Failed to get first metrics class
            return;
        }
        if (usedMetricsClass == getClass()) {
            // We are the first! :)
            linkMetrics(this);
            startSubmitting();
        } else {
            // We aren't the first so we link to the first metrics class
            try {
                usedMetricsClass.getMethod("linkMetrics", Object.class).invoke(null,this);
            } catch (NoSuchMethodException | IllegalAccessException | InvocationTargetException e) {
                if (logFailedRequests) {
                    logger.warn("Failed to link to first metrics class {}!", usedMetricsClass.getName(), e);
                }
            }
        }
    }

    /**
     * Links an other metrics class with this class.
     * This method is called using Reflection.
     *
     * @param metrics An object of the metrics class to link.
     */
    public static void linkMetrics(Object metrics) {
        knownMetricsInstances.add(metrics);
    }

    /**
     * Gets the plugin specific data.
     * This method is called using Reflection.
     *
     * @return The plugin specific data.
     */
    public JsonObject getPluginData() {
        JsonObject data = new JsonObject();

        String pluginName = "SubServers Client";
        String pluginVersion = plugin.version.toString();

        data.addProperty("pluginName", pluginName);
        data.addProperty("pluginVersion", pluginVersion);

        JsonArray customCharts = new JsonArray();
        data.add("customCharts", customCharts);

        return data;
    }

    private void startSubmitting() {
        // We use a timer cause want to be independent from the server tps
        final Timer timer = new Timer(true);
        timer.scheduleAtFixedRate(new TimerTask() {
            @Override
            public void run() {
                // Plugin was disabled, e.g. because of a reload (is this even possible in Sponge?)
                if (!Sponge.getPluginManager().isLoaded(plugin.plugin.getId())) {
                    timer.cancel();
                    return;
                }
                // The data collection (e.g. for custom graphs) is done sync
                // Don't be afraid! The connection to the bStats server is still async, only the stats collection is sync ;)
                Scheduler scheduler = Sponge.getScheduler();
                Task.Builder taskBuilder = scheduler.createTaskBuilder();
                taskBuilder.execute(() -> submitData()).submit(plugin);
            }
        }, 1000*60*5, 1000*60*30);
        // Submit the data every 30 minutes, first time after 5 minutes to give other plugins enough time to start
        // WARNING: Changing the frequency has no effect but your plugin WILL be blocked/deleted!
        // WARNING: Just don't do it!
    }

    /**
     * Gets the server specific data.
     *
     * @return The server specific data.
     */
    private JsonObject getServerData() {
        // Minecraft specific data
        int playerAmount = Sponge.getServer().getOnlinePlayers().size();
        playerAmount = playerAmount > 200 ? 200 : playerAmount;
        int onlineMode = Sponge.getServer().getOnlineMode() ? 1 : 0;
        String minecraftVersion = Sponge.getGame().getPlatform().getMinecraftVersion().getName();
        String spongeImplementation = plugin.api.getServerVersion() + "";

        // OS/Java specific data
        String javaVersion = System.getProperty("java.version");
        String osName = System.getProperty("os.name");
        String osArch = System.getProperty("os.arch");
        String osVersion = System.getProperty("os.version");
        int coreCount = Runtime.getRuntime().availableProcessors();

        JsonObject data = new JsonObject();

        data.addProperty("serverUUID", serverUUID);

        data.addProperty("playerAmount", playerAmount);
        data.addProperty("onlineMode", onlineMode);
        data.addProperty("minecraftVersion", minecraftVersion);
        data.addProperty("spongeImplementation", spongeImplementation);

        data.addProperty("javaVersion", javaVersion);
        data.addProperty("osName", osName);
        data.addProperty("osArch", osArch);
        data.addProperty("osVersion", osVersion);
        data.addProperty("coreCount", coreCount);

        return data;
    }

    /**
     * Collects the data and sends it afterwards.
     */
    private void submitData() {
        final JsonObject data = getServerData();

        JsonArray pluginData = new JsonArray();
        // Search for all other bStats Metrics classes to get their plugin data
        for (Object metrics : knownMetricsInstances) {
            try {
                Object plugin = metrics.getClass().getMethod("getPluginData").invoke(metrics);
                if (plugin instanceof JsonObject) {
                    pluginData.add((JsonObject) plugin);
                }
            } catch (NoSuchMethodException | IllegalAccessException | InvocationTargetException ignored) { }
        }

        data.add("plugins", pluginData);

        // Create a new thread for the connection to the bStats server
        new Thread(() ->  {
            try {
                // Send the data
                sendData(data);
            } catch (Exception e) {
                // Something went wrong! :(
                if (logFailedRequests) {
                    logger.warn("Could not submit plugin stats!", e);
                }
            }
        }).start();
    }

    /**
     * Loads the bStats configuration.
     *
     * @throws IOException If something did not work :(
     */
    private void loadConfig() throws IOException {
        Path configPath = configDir.resolve("bStats");
        configPath.toFile().mkdirs();
        File configFile = new File(configPath.toFile(), "config.conf");
        HoconConfigurationLoader configurationLoader = HoconConfigurationLoader.builder().setFile(configFile).build();
        CommentedConfigurationNode node;
        if (!configFile.exists()) {
            configFile.createNewFile();
            node = configurationLoader.load();

            // Add default values
            node.getNode("enabled").setValue(true);
            // Every server gets it's unique random id.
            node.getNode("serverUuid").setValue(UUID.randomUUID().toString());
            // Should failed request be logged?
            node.getNode("logFailedRequests").setValue(false);

            // Add information about bStats
            node.getNode("enabled").setComment(
                    "bStats collects some data for plugin authors like how many servers are using their plugins.\n" +
                            "To honor their work, you should not disable it.\n" +
                            "This has nearly no effect on the server performance!\n" +
                            "Check out https://bStats.org/ to learn more :)"
            );

            configurationLoader.save(node);
        } else {
            node = configurationLoader.load();
        }

        // Load configuration
        enabled = node.getNode("enabled").getBoolean(true);
        serverUUID = node.getNode("serverUuid").getString();
        logFailedRequests = node.getNode("logFailedRequests").getBoolean(false);
    }

    /**
     * Gets the first bStat Metrics class.
     *
     * @return The first bStats metrics class.
     */
    private Class<?> getFirstBStatsClass() {
        Path configPath = configDir.resolve("bStats");
        configPath.toFile().mkdirs();
        File tempFile = new File(configPath.toFile(), "temp.txt");

        try {
            String className = readFile(tempFile);
            if (className != null) {
                try {
                    // Let's check if a class with the given name exists.
                    return Class.forName(className);
                } catch (ClassNotFoundException ignored) { }
            }
            writeFile(tempFile, getClass().getName());
            return getClass();
        } catch (IOException e) {
            if (logFailedRequests) {
                logger.warn("Failed to get first bStats class!", e);
            }
            return null;
        }
    }

    /**
     * Reads the first line of the file.
     *
     * @param file The file to read. Cannot be null.
     * @return The first line of the file or <code>null</code> if the file does not exist or is empty.
     * @throws IOException If something did not work :(
     */
    private String readFile(File file) throws IOException {
        if (!file.exists()) {
            return null;
        }
        try (
                FileReader fileReader = new FileReader(file);
                BufferedReader bufferedReader =  new BufferedReader(fileReader);
        ) {
            return bufferedReader.readLine();
        }
    }

    /**
     * Writes a String to a file. It also adds a note for the user,
     *
     * @param file The file to write to. Cannot be null.
     * @param text The text to write.
     * @throws IOException If something did not work :(
     */
    private void writeFile(File file, String text) throws IOException {
        if (!file.exists()) {
            file.createNewFile();
        }
        try (
                FileWriter fileWriter = new FileWriter(file);
                BufferedWriter bufferedWriter = new BufferedWriter(fileWriter)
        ) {
            bufferedWriter.write(text);
            bufferedWriter.newLine();
            bufferedWriter.write("Note: This class only exists for internal purpose. You can ignore it :)");
        }
    }

    /**
     * Sends the data to the bStats server.
     *
     * @param data The data to send.
     * @throws Exception If the request failed.
     */
    private static void sendData(JsonObject data) throws Exception {
        Validate.notNull(data, "Data cannot be null");
        HttpsURLConnection connection = (HttpsURLConnection) new URL(URL).openConnection();

        // Compress the data to save bandwidth
        byte[] compressedData = compress(data.toString());

        // Add headers
        connection.setRequestMethod("POST");
        connection.addRequestProperty("Accept", "application/json");
        connection.addRequestProperty("Connection", "close");
        connection.addRequestProperty("Content-Encoding", "gzip"); // We gzip our request
        connection.addRequestProperty("Content-Length", String.valueOf(compressedData.length));
        connection.setRequestProperty("Content-Type", "application/json"); // We send our data in JSON format
        connection.setRequestProperty("User-Agent", "MC-Server/" + B_STATS_VERSION);

        // Send data
        connection.setDoOutput(true);
        DataOutputStream outputStream = new DataOutputStream(connection.getOutputStream());
        outputStream.write(compressedData);
        outputStream.flush();
        outputStream.close();

        connection.getInputStream().close(); // We don't care about the response - Just send our data :)
    }

    /**
     * Gzips the given String.
     *
     * @param str The string to gzip.
     * @return The gzipped String.
     * @throws IOException If the compression failed.
     */
    private static byte[] compress(final String str) throws IOException {
        if (str == null) {
            return null;
        }
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        GZIPOutputStream gzip = new GZIPOutputStream(outputStream);
        gzip.write(str.getBytes("UTF-8"));
        gzip.close();
        return outputStream.toByteArray();
    }

}