package com.Acrobot.ChestShop;

import org.bukkit.Bukkit;
import org.bukkit.configuration.InvalidConfigurationException;
import org.bukkit.configuration.file.YamlConfiguration;
import org.bukkit.plugin.Plugin;
import org.bukkit.plugin.PluginDescriptionFile;

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import java.net.Proxy;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLEncoder;
import java.util.UUID;
import java.util.logging.Level;

public class Metrics {

    /**
     * The current revision number
     */
    private final static int REVISION = 5;

    /**
     * The base url of the metrics domain
     */
    private static final String BASE_URL = "http://mcstats.org";

    /**
     * The url used to report a server's status
     */
    private static final String REPORT_URL = "/report/%s";

    /**
     * The file where guid and opt out is stored in
     */
    private static final String CONFIG_FILE = "plugins/PluginMetrics/config.yml";

    /**
     * Interval of time to ping (in minutes)
     */
    private final static int PING_INTERVAL = 10;

    /**
     * The plugin this metrics submits for
     */
    private final Plugin plugin;

    /**
     * The plugin configuration file
     */
    private final YamlConfiguration configuration;

    /**
     * The plugin configuration file
     */
    private final File configurationFile;

    /**
     * Unique server id
     */
    private final String guid;

    /**
     * Lock for synchronization
     */
    private final Object optOutLock = new Object();

    /**
     * Id of the scheduled task
     */
    private volatile int taskId = -1;

    public Metrics(Plugin plugin) throws IOException {
        if (plugin == null) {
            throw new IllegalArgumentException("Plugin cannot be null");
        }

        this.plugin = plugin;

        // load the config
        configurationFile = new File(CONFIG_FILE);
        configuration = YamlConfiguration.loadConfiguration(configurationFile);

        // add some defaults
        configuration.addDefault("opt-out", false);
        configuration.addDefault("guid", UUID.randomUUID().toString());

        // Do we need to create the file?
        if (configuration.get("guid", null) == null) {
            configuration.options().header("http://mcstats.org").copyDefaults(true);
            configuration.save(configurationFile);
        }

        // Load the guid then
        guid = configuration.getString("guid");
    }


    /**
     * Start measuring statistics. This will immediately create an async repeating task as the plugin and send
     * the initial data to the metrics backend, and then after that it will post in increments of
     * PING_INTERVAL * 1200 ticks.
     *
     * @return True if statistics measuring is running, otherwise false.
     */
    public boolean start() {
        synchronized (optOutLock) {
            // Did we opt out?
            if (isOptOut()) {
                return false;
            }

            // Is metrics already running?
            if (taskId >= 0) {
                return true;
            }

            // Begin hitting the server with glorious data
            taskId = plugin.getServer().getScheduler().scheduleAsyncRepeatingTask(plugin, new Runnable() {

                private boolean firstPost = true;

                public void run() {
                    try {
                        // This has to be synchronized or it can collide with the disable method.
                        synchronized (optOutLock) {
                            // Disable Task, if it is running and the server owner decided to opt-out
                            if (isOptOut() && taskId > 0) {
                                plugin.getServer().getScheduler().cancelTask(taskId);
                                taskId = -1;
                            }
                        }

                        // We use the inverse of firstPost because if it is the first time we are posting,
                        // it is not a interval ping, so it evaluates to FALSE
                        // Each time thereafter it will evaluate to TRUE, i.e PING!
                        postPlugin(!firstPost);

                        // After the first post we set firstPost to false
                        // Each post thereafter will be a ping
                        firstPost = false;
                    } catch (IOException e) {
                        Bukkit.getLogger().log(Level.INFO, "[Metrics] {0}", e.getMessage());
                    }
                }
            }, 0, PING_INTERVAL * 1200);

            return true;
        }
    }

    /**
     * Has the server owner denied plugin metrics?
     *
     * @return
     */
    public boolean isOptOut() {
        synchronized(optOutLock) {
            try {
                // Reload the metrics file
                configuration.load(CONFIG_FILE);
            } catch (IOException ex) {
                Bukkit.getLogger().log(Level.INFO, "[Metrics] {0}", ex.getMessage());
                return true;
            } catch (InvalidConfigurationException ex) {
                Bukkit.getLogger().log(Level.INFO, "[Metrics] {0}", ex.getMessage());
                return true;
            }
            return configuration.getBoolean("opt-out", false);
        }
    }

    /**
     * Enables metrics for the server by setting "opt-out" to false in the config file and starting the metrics task.
     *
     * @throws IOException
     */
    public void enable() throws IOException {
        // This has to be synchronized or it can collide with the check in the task.
        synchronized (optOutLock) {
            // Check if the server owner has already set opt-out, if not, set it.
            if (isOptOut()) {
                configuration.set("opt-out", false);
                configuration.save(configurationFile);
            }

            // Enable Task, if it is not running
            if (taskId < 0) {
                start();
            }
        }
    }

    /**
     * Disables metrics for the server by setting "opt-out" to true in the config file and canceling the metrics task.
     *
     * @throws IOException
     */
    public void disable() throws IOException {
        // This has to be synchronized or it can collide with the check in the task.
        synchronized (optOutLock) {
            // Check if the server owner has already set opt-out, if not, set it.
            if (!isOptOut()) {
                configuration.set("opt-out", true);
                configuration.save(configurationFile);
            }

            // Disable Task, if it is running
            if (taskId > 0) {
                this.plugin.getServer().getScheduler().cancelTask(taskId);
                taskId = -1;
            }
        }
    }

    /**
     * Generic method that posts a plugin to the metrics website
     */
    private void postPlugin(boolean isPing) throws IOException {
        // The plugin's description file containg all of the plugin data such as name, version, author, etc
        final PluginDescriptionFile description = plugin.getDescription();

        // Construct the post data
        final StringBuilder data = new StringBuilder(100);
        data.append(encode("guid")).append('=').append(encode(guid));
        encodeDataPair(data, "version", description.getVersion());
        encodeDataPair(data, "server", Bukkit.getVersion());
        encodeDataPair(data, "players", Integer.toString(Bukkit.getServer().getOnlinePlayers().length));
        encodeDataPair(data, "revision", String.valueOf(REVISION));

        // If we're pinging, append it
        if (isPing) {
            encodeDataPair(data, "ping", "true");
        }

        // Create the url
        URL url = new URL(BASE_URL + String.format(REPORT_URL, encode(plugin.getDescription().getName())));

        // Connect to the website
        URLConnection connection;

        // Mineshafter creates a socks proxy, so we can safely bypass it
        // It does not reroute POST requests so we need to go around it
        if (isMineshafterPresent()) {
            connection = url.openConnection(Proxy.NO_PROXY);
        } else {
            connection = url.openConnection();
        }

        connection.setDoOutput(true);

        // Write the data
        final OutputStreamWriter writer = new OutputStreamWriter(connection.getOutputStream());
        writer.write(data.toString());
        writer.flush();

        // Now read the response
        final BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
        final String response = reader.readLine();

        // close resources
        writer.close();
        reader.close();

        if (response == null || response.startsWith("ERR")) {
            throw new IOException(response); //Throw the exception
        }
        //if (response.startsWith("OK")) - We should get "OK" followed by an optional description if everything goes right
    }

    /**
     * Check if mineshafter is present. If it is, we need to bypass it to send POST requests
     *
     * @return
     */
    private static boolean isMineshafterPresent() {
        try {
            Class.forName("mineshafter.MineServer");
            return true;
        } catch (Exception e) {
            return false;
        }
    }

    /**
     * <p>Encode a key/value data pair to be used in a HTTP post request. This INCLUDES a & so the first
     * key/value pair MUST be included manually, e.g:</p>
     * <code>
     * StringBuffer data = new StringBuffer();
     * data.append(encode("guid")).append('=').append(encode(guid));
     * encodeDataPair(data, "version", description.getVersion());
     * </code>
     *
     * @param buffer
     * @param key
     * @param value
     * @return
     */
    private static void encodeDataPair(final StringBuilder buffer, final String key, final String value) throws UnsupportedEncodingException {
        buffer.append('&').append(encode(key)).append('=').append(encode(value));
    }

    /**
     * Encode text as UTF-8
     *
     * @param text
     * @return
     */
    private static String encode(String text) throws UnsupportedEncodingException {
        return URLEncoder.encode(text, "UTF-8");
    }

}