/*
 * 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 ch.njol.skript;

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.Iterator;
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.eclipse.jdt.annotation.NonNull;
import org.eclipse.jdt.annotation.NonNullByDefault;
import org.eclipse.jdt.annotation.Nullable;

import ch.njol.skript.bukkitutil.PlayerUtils;
import ch.njol.skript.util.Task;

// Copied to have this source available as mcstats' Maven repo does neither provide the source nor any Javadocs
// I also made a few changes to support older versions of Bukkit
@NonNullByDefault(false)
public class Metrics {
	
	/**
	 * The current revision number
	 */
	private final static int REVISION = 7;
	
	/**
	 * The base url of the metrics domain
	 */
	private final static String BASE_URL = "http://report.mcstats.org";
	
	/**
	 * The url used to report a server's state
	 */
	private final static String REPORT_URL = "/plugin/%s";
	
	/**
	 * Interval of time to ping (in minutes)
	 */
	private final static int PING_INTERVAL = 15;
	
	/**
	 * The plugin this metrics submits for
	 */
	@NonNull
	private final Plugin plugin;
	
	/**
	 * All of the custom graphs to submit to metrics
	 */
	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
	 */
	final boolean debug;
	
	/**
	 * Lock for synchronization
	 */
	final Object optOutLock = new Object();
	
	/**
	 * The scheduled task
	 */
	@Nullable
	Task task = null;
	
	public Metrics(final Plugin plugin) {
		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);
			try {
				configuration.save(configurationFile);
			} catch (final IOException e) {}
		}
		
		// 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 = new Task(plugin, 0, PING_INTERVAL * 1200, true) {
				
				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 (final 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 (final IOException e) {
						if (debug) {
							Bukkit.getLogger().log(Level.INFO, "[Metrics] " + e.getMessage());
						}
					}
				}
			};
			
			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 (final IOException ex) {
				if (debug) {
					Bukkit.getLogger().log(Level.INFO, "[Metrics] " + ex.getMessage());
				}
				return true;
			} catch (final 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 state
	 * 
	 * @return the File object for the config file
	 */
	public File getConfigFile() {
		// I believe the easiest way to get the base folder (e.g craftbukkit 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.
		final 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
	 */
	void postPlugin(final boolean isPing) throws IOException {
		// Server software specific section
		final PluginDescriptionFile description = plugin.getDescription();
		final String pluginName = description.getName();
		final boolean onlineMode = Bukkit.getServer().getOnlineMode(); // TRUE if online mode is enabled
		final String pluginVersion = description.getVersion();
		final String serverVersion = Bukkit.getVersion();
		final int playersOnline = PlayerUtils.getOnlinePlayers().size();
		
		// END server software specific section -- all code below does not use any code outside of this class / Java
		
		// Construct the post data
		final 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
		final String osname = System.getProperty("os.name");
		String osarch = System.getProperty("os.arch");
		final String osversion = System.getProperty("os.version");
		final String java_version = System.getProperty("java.version");
		final 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;
				
				final Iterator<Graph> iter = graphs.iterator();
				
				while (iter.hasNext()) {
					final Graph graph = iter.next();
					
					final StringBuilder graphJson = new StringBuilder();
					graphJson.append('{');
					
					for (final 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
		final 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();
		}
		
		final byte[] uncompressed = json.toString().getBytes();
		final 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
		final OutputStream os = connection.getOutputStream();
		os.write(compressed);
		os.flush();
		
		// Now read the response
		final BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
		String response = reader.readLine();
		
		// close resources
		os.close();
		reader.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) {
					final Iterator<Graph> iter = graphs.iterator();
					
					while (iter.hasNext()) {
						final Graph graph = iter.next();
						
						for (final Plotter plotter : graph.getPlotters()) {
							plotter.reset();
						}
					}
				}
			}
		}
	}
	
	/**
	 * GZip compress a string of bytes
	 * 
	 * @param input
	 * @return Compressed data
	 */
	public static byte[] gzip(final String input) {
		final ByteArrayOutputStream baos = new ByteArrayOutputStream();
		GZIPOutputStream gzos = null;
		
		try {
			gzos = new GZIPOutputStream(baos);
			gzos.write(input.getBytes("UTF-8"));
		} catch (final IOException e) {
			e.printStackTrace();
		} finally {
			if (gzos != null)
				try {
					gzos.close();
				} catch (final 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 static boolean isMineshafterPresent() {
		try {
			Class.forName("mineshafter.MineServer");
			return true;
		} catch (final Exception e) {
			return false;
		}
	}
	
	/**
	 * Appends a json encoded key/value pair to the given string builder.
	 * 
	 * @param json
	 * @param key
	 * @param value
	 */
	private static void appendJSONPair(final StringBuilder json, final String key, final String value) {
		boolean isValueNumeric = false;
		
		try {
			if (value.equals("0") || !value.endsWith("0")) {
				Double.parseDouble(value);
				isValueNumeric = true;
			}
		} catch (final 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 Escaped String
	 */
	private static String escapeJSON(final String text) {
		final StringBuilder builder = new StringBuilder();
		
		builder.append('"');
		for (int index = 0; index < text.length(); index++) {
			final 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 < ' ') {
						final String t = "000" + Integer.toHexString(chr);
						builder.append("\\u" + 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<>();
		
		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();
		}
	}
}
