/*
 * Copyright 2011-2013 Tyler Blair. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are
 * permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this list of
 * conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice, this list
 * of conditions and the following disclaimer in the documentation and/or other materials
 * provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ''AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * The views and conclusions contained in the software and documentation are those of the
 * authors and contributors and should not be interpreted as representing official policies,
 * either expressed or implied, of anybody else.
 */
package me.libraryaddict.disguise.utilities;

import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.net.Proxy;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLEncoder;
import java.util.Collections;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.Set;
import java.util.UUID;
import java.util.logging.Level;
import java.util.zip.GZIPOutputStream;

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 org.bukkit.scheduler.BukkitTask;

public class Metrics
{

    /**
     * The current revision number
     */
    private final static int REVISION = 7;
    /**
     * The base url of the metrics domain
     */
    private static final String BASE_URL = "http://report.mcstats.org";
    /**
     * The url used to report a server's status
     */
    private static final String REPORT_URL = "/plugin/%s";
    /**
     * Interval of time to ping (in minutes)
     */
    private static final int PING_INTERVAL = 15;
    /**
     * The plugin this metrics submits for
     */
    private final Plugin plugin;
    /**
     * All of the custom graphs to submit to metrics
     */
    private final Set<Graph> graphs = Collections.synchronizedSet(new HashSet<Graph>());
    /**
     * The plugin configuration file
     */
    private final YamlConfiguration configuration;
    /**
     * The plugin configuration file
     */
    private final File configurationFile;
    /**
     * Unique server id
     */
    private final String guid;
    /**
     * Debug mode
     */
    private final boolean debug;
    /**
     * Lock for synchronization
     */
    private final Object optOutLock = new Object();
    /**
     * The scheduled task
     */
    private volatile BukkitTask task = null;

    public Metrics(final Plugin plugin) throws IOException
    {
        if (plugin == null)
        {
            throw new IllegalArgumentException("Plugin cannot be null");
        }
        this.plugin = plugin;
        // load the config
        configurationFile = getConfigFile();
        configuration = YamlConfiguration.loadConfiguration(configurationFile);
        // add some defaults
        configuration.addDefault("opt-out", false);
        configuration.addDefault("guid", UUID.randomUUID().toString());
        configuration.addDefault("debug", false);
        // 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");
        debug = configuration.getBoolean("debug", false);
    }

    /**
     * Construct and create a Graph that can be used to separate specific plotters to their own graphs on the metrics website.
     * Plotters can be added to the graph object returned.
     *
     * @param name
     *            The name of the graph
     * @return Graph object created. Will never return NULL under normal circumstances unless bad parameters are given
     */
    public Graph createGraph(final String name)
    {
        if (name == null)
        {
            throw new IllegalArgumentException("Graph name cannot be null");
        }
        // Construct the graph object
        final Graph graph = new Graph(name);
        // Now we can add our graph
        graphs.add(graph);
        // and return back
        return graph;
    }

    /**
     * Add a Graph object to BukkitMetrics that represents data for the plugin that should be sent to the backend
     *
     * @param graph
     *            The name of the graph
     */
    public void addGraph(final Graph graph)
    {
        if (graph == null)
        {
            throw new IllegalArgumentException("Graph cannot be null");
        }
        graphs.add(graph);
    }

    /**
     * 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 (task != null)
            {
                return true;
            }
            // Begin hitting the server with glorious data
            task = plugin.getServer().getScheduler().runTaskTimerAsynchronously(plugin, new Runnable()
            {
                private boolean firstPost = true;

                @Override
                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() && task != null)
                            {
                                task.cancel();
                                task = null;
                                // Tell all plotters to stop gathering information.
                                for (Graph graph : graphs)
                                {
                                    graph.onOptOut();
                                }
                            }
                        }
                        // 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)
                    {
                        if (debug)
                        {
                            Bukkit.getLogger().log(Level.INFO, "[Metrics] " + e.getMessage());
                        }
                    }
                }
            }, 0, PING_INTERVAL * 1200);
            return true;
        }
    }

    /**
     * Has the server owner denied plugin metrics?
     *
     * @return true if metrics should be opted out of it
     */
    public boolean isOptOut()
    {
        synchronized (optOutLock)
        {
            try
            {
                // Reload the metrics file
                configuration.load(getConfigFile());
            }
            catch (IOException | InvalidConfigurationException ex)
            {
                if (debug)
                {
                    Bukkit.getLogger().log(Level.INFO, "[Metrics] " + 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 java.io.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 (task == null)
            {
                start();
            }
        }
    }

    /**
     * Disables metrics for the server by setting "opt-out" to true in the config file and canceling the metrics task.
     *
     * @throws java.io.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 (task != null)
            {
                task.cancel();
                task = null;
            }
        }
    }

    /**
     * Gets the File object of the config file that should be used to store data such as the GUID and opt-out status
     *
     * @return the File object for the config file
     */
    public File getConfigFile()
    {
        // I believe the easiest way to get the base folder (e.g Spigot set via -P) for plugins to use
        // is to abuse the plugin object we already have
        // plugin.getDataFolder() => base/plugins/PluginA/
        // pluginsFolder => base/plugins/
        // The base is not necessarily relative to the startup directory.
        File pluginsFolder = plugin.getDataFolder().getParentFile();
        // return => base/plugins/PluginMetrics/config.yml
        return new File(new File(pluginsFolder, "PluginMetrics"), "config.yml");
    }

    /**
     * Generic method that posts a plugin to the metrics website
     */
    private void postPlugin(final boolean isPing) throws IOException
    {
        // Server software specific section
        PluginDescriptionFile description = plugin.getDescription();
        String pluginName = description.getName();
        boolean onlineMode = Bukkit.getServer().getOnlineMode(); // TRUE if online mode is enabled
        String pluginVersion = description.getVersion();
        String serverVersion = Bukkit.getVersion();
        int playersOnline = Bukkit.getServer().getOnlinePlayers().size();
        // END server software specific section -- all code below does not use any code outside of this class / Java
        // Construct the post data
        StringBuilder json = new StringBuilder(1024);
        json.append('{');
        // The plugin's description file containg all of the plugin data such as name, version, author, etc
        appendJSONPair(json, "guid", guid);
        appendJSONPair(json, "plugin_version", pluginVersion);
        appendJSONPair(json, "server_version", serverVersion);
        appendJSONPair(json, "players_online", Integer.toString(playersOnline));
        // New data as of R6
        String osname = System.getProperty("os.name");
        String osarch = System.getProperty("os.arch");
        String osversion = System.getProperty("os.version");
        String java_version = System.getProperty("java.version");
        int coreCount = Runtime.getRuntime().availableProcessors();
        // normalize os arch .. amd64 -> x86_64
        if (osarch.equals("amd64"))
        {
            osarch = "x86_64";
        }
        appendJSONPair(json, "osname", osname);
        appendJSONPair(json, "osarch", osarch);
        appendJSONPair(json, "osversion", osversion);
        appendJSONPair(json, "cores", Integer.toString(coreCount));
        appendJSONPair(json, "auth_mode", onlineMode ? "1" : "0");
        appendJSONPair(json, "java_version", java_version);
        // If we're pinging, append it
        if (isPing)
        {
            appendJSONPair(json, "ping", "1");
        }
        if (graphs.size() > 0)
        {
            synchronized (graphs)
            {
                json.append(',');
                json.append('"');
                json.append("graphs");
                json.append('"');
                json.append(':');
                json.append('{');
                boolean firstGraph = true;
                for (Graph graph : graphs)
                {
                    StringBuilder graphJson = new StringBuilder();
                    graphJson.append('{');
                    for (Plotter plotter : graph.getPlotters())
                    {
                        appendJSONPair(graphJson, plotter.getColumnName(), Integer.toString(plotter.getValue()));
                    }
                    graphJson.append('}');
                    if (!firstGraph)
                    {
                        json.append(',');
                    }
                    json.append(escapeJSON(graph.getName()));
                    json.append(':');
                    json.append(graphJson);
                    firstGraph = false;
                }
                json.append('}');
            }
        }
        // close json
        json.append('}');
        // Create the url
        URL url = new URL(BASE_URL + String.format(REPORT_URL, urlEncode(pluginName)));
        // 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();
        }
        byte[] uncompressed = json.toString().getBytes();
        byte[] compressed = gzip(json.toString());
        // Headers
        connection.addRequestProperty("User-Agent", "MCStats/" + REVISION);
        connection.addRequestProperty("Content-Type", "application/json");
        connection.addRequestProperty("Content-Encoding", "gzip");
        connection.addRequestProperty("Content-Length", Integer.toString(compressed.length));
        connection.addRequestProperty("Accept", "application/json");
        connection.addRequestProperty("Connection", "close");
        connection.setDoOutput(true);
        if (debug)
        {
            System.out.println("[Metrics] Prepared request for " + pluginName + " uncompressed=" + uncompressed.length
                    + " compressed=" + compressed.length);
        }
        // Write the data
        OutputStream os = connection.getOutputStream();
        os.write(compressed);
        os.flush();
        String response;
        try ( // Now read the response
                BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream())))
        {
            response = reader.readLine();
            // close resources
            os.close();
        }
        if (response == null || response.startsWith("ERR") || response.startsWith("7"))
        {
            if (response == null)
            {
                response = "null";
            }
            else if (response.startsWith("7"))
            {
                response = response.substring(response.startsWith("7,") ? 2 : 1);
            }
            throw new IOException(response);
        }
        else
        {
            // Is this the first update this hour?
            if (response.equals("1") || response.contains("This is your first update this hour"))
            {
                synchronized (graphs)
                {
                    for (Graph graph : graphs)
                    {
                        for (Plotter plotter : graph.getPlotters())
                        {
                            plotter.reset();
                        }
                    }
                }
            }
        }
    }

    /**
     * GZip compress a string of bytes
     *
     * @param input
     * @return byte[]
     */
    public static byte[] gzip(String input)
    {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        GZIPOutputStream gzos = null;
        try
        {
            gzos = new GZIPOutputStream(baos);
            gzos.write(input.getBytes("UTF-8"));
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
        finally
        {
            if (gzos != null)
            {
                try
                {
                    gzos.close();
                }
                catch (IOException ignore)
                {
                }
            }
        }
        return baos.toByteArray();
    }

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

    /**
     * Appends a json encoded key/value pair to the given string builder.
     *
     * @param json
     * @param key
     * @param value
     * @throws UnsupportedEncodingException
     */
    private static void appendJSONPair(StringBuilder json, String key, String value) throws UnsupportedEncodingException
    {
        boolean isValueNumeric = false;
        try
        {
            if (value.equals("0") || !value.endsWith("0"))
            {
                Double.parseDouble(value);
                isValueNumeric = true;
            }
        }
        catch (NumberFormatException e)
        {
            isValueNumeric = false;
        }
        if (json.charAt(json.length() - 1) != '{')
        {
            json.append(',');
        }
        json.append(escapeJSON(key));
        json.append(':');
        if (isValueNumeric)
        {
            json.append(value);
        }
        else
        {
            json.append(escapeJSON(value));
        }
    }

    /**
     * Escape a string to create a valid JSON string
     *
     * @param text
     * @return String
     */
    private static String escapeJSON(String text)
    {
        StringBuilder builder = new StringBuilder();
        builder.append('"');
        for (int index = 0; index < text.length(); index++)
        {
            char chr = text.charAt(index);
            switch (chr)
            {
            case '"':
            case '\\':
                builder.append('\\');
                builder.append(chr);
                break;
            case '\b':
                builder.append("\\b");
                break;
            case '\t':
                builder.append("\\t");
                break;
            case '\n':
                builder.append("\\n");
                break;
            case '\r':
                builder.append("\\r");
                break;
            default:
                if (chr < ' ')
                {
                    String t = "000" + Integer.toHexString(chr);
                    builder.append("\\u").append(t.substring(t.length() - 4));
                }
                else
                {
                    builder.append(chr);
                }
                break;
            }
        }
        builder.append('"');
        return builder.toString();
    }

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

    /**
     * Represents a custom graph on the website
     */
    public static class Graph
    {

        /**
         * The graph's name, alphanumeric and spaces only :) If it does not comply to the above when submitted, it is rejected
         */
        private final String name;
        /**
         * The set of plotters that are contained within this graph
         */
        private final Set<Plotter> plotters = new LinkedHashSet<>();

        private Graph(final String name)
        {
            this.name = name;
        }

        /**
         * Gets the graph's name
         *
         * @return the Graph's name
         */
        public String getName()
        {
            return name;
        }

        /**
         * Add a plotter to the graph, which will be used to plot entries
         *
         * @param plotter
         *            the plotter to add to the graph
         */
        public void addPlotter(final Plotter plotter)
        {
            plotters.add(plotter);
        }

        /**
         * Remove a plotter from the graph
         *
         * @param plotter
         *            the plotter to remove from the graph
         */
        public void removePlotter(final Plotter plotter)
        {
            plotters.remove(plotter);
        }

        /**
         * Gets an <b>unmodifiable</b> set of the plotter objects in the graph
         *
         * @return an unmodifiable {@link java.util.Set} of the plotter objects
         */
        public Set<Plotter> getPlotters()
        {
            return Collections.unmodifiableSet(plotters);
        }

        @Override
        public int hashCode()
        {
            return name.hashCode();
        }

        @Override
        public boolean equals(final Object object)
        {
            if (!(object instanceof Graph))
            {
                return false;
            }
            final Graph graph = (Graph) object;
            return graph.name.equals(name);
        }

        /**
         * Called when the server owner decides to opt-out of BukkitMetrics while the server is running.
         */
        protected void onOptOut()
        {
        }
    }

    /**
     * Interface used to collect custom data for a plugin
     */
    public static abstract class Plotter
    {

        /**
         * The plot's name
         */
        private final String name;

        /**
         * Construct a plotter with the default plot name
         */
        public Plotter()
        {
            this("Default");
        }

        /**
         * Construct a plotter with a specific plot name
         *
         * @param name
         *            the name of the plotter to use, which will show up on the website
         */
        public Plotter(final String name)
        {
            this.name = name;
        }

        /**
         * Get the current value for the plotted point. Since this function defers to an external function it may or may not
         * return immediately thus cannot be guaranteed to be thread friendly or safe. This function can be called from any thread
         * so care should be taken when accessing resources that need to be synchronized.
         *
         * @return the current value for the point to be plotted.
         */
        public abstract int getValue();

        /**
         * Get the column name for the plotted point
         *
         * @return the plotted point's column name
         */
        public String getColumnName()
        {
            return name;
        }

        /**
         * Called after the website graphs have been updated
         */
        public void reset()
        {
        }

        @Override
        public int hashCode()
        {
            return getColumnName().hashCode();
        }

        @Override
        public boolean equals(final Object object)
        {
            if (!(object instanceof Plotter))
            {
                return false;
            }
            final Plotter plotter = (Plotter) object;
            return plotter.name.equals(name) && plotter.getValue() == getValue();
        }
    }
}