package io;

import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Reader;
import static java.lang.Thread.sleep;
import java.util.Scanner;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.logging.Level;
import java.util.logging.Logger;
import mining.Search;
import mining.TwitterApi;
import mining.TwitterApi.Builder;
import provider.ExceptionListener;
import provider.ResultListener;

/**
 * Implementation of the search with rate limit handling and multiple threads
 *
 * @author Maurice Laveaux
 */
public class SearchImpl implements Search {

    private static final String USER_TIMELINE_RESOURCE = "statuses/user_timeline";

    /**
     * The result listener to report results to
     */
    private ResultListener resultListener = null;

    /**
     * Dummy object to synchronize the resultListener;
     */
    private final Object resultListenerSync = new Object();

    /**
     * The list of user searches are done on search.
     */
    private final BlockingQueue<Request> requestQueue;

    /**
     * The thread container that handles both io and request thread.
     */
    private ThreadContainer thread_cached;

    /**
     * The twitter api to execute requests.
     */
    private final TwitterApi oauth;

    public SearchImpl(TwitterApi oauth) {
        this.oauth = oauth;
        requestQueue = new LinkedBlockingQueue();
        load("search_cache");
        
        if (thread_cached == null) {
            thread_cached = new ThreadContainer();
            thread_cached.start();
        }
        
        if (requestQueue.size() > 0) {
            System.out.println("Resumed " + requestQueue.size() + " amount of requests");
        }
    }

    @Override
    public void search(String screenName, int numberOfTweets) {
        if (numberOfTweets > 3200) {
            numberOfTweets = 3200;
            System.out.println("Changed number of tweets to max 3200.");
        }

        requestQueue.offer(new Request(screenName, numberOfTweets));
    }

    @Override
    public void setResultListener(ResultListener listener) {
        synchronized (resultListenerSync) {
            resultListener = listener;
        }
    }

    @Override
    public final void save(String filename) {
        try (FileWriter writer = new FileWriter(filename)) {
            for (Request req : requestQueue) {
                writer.append(req.toString() + "\n");
            }
        } catch (IOException ex) {
            Logger.getLogger(SearchImpl.class.getName()).log(Level.SEVERE,
                    "save error", ex);
        }
    }

    @Override
    public final void load(String filename) {
        try (Reader fileReader = new FileReader(filename)) {
            BufferedReader reader = new BufferedReader(fileReader);

            String line;
            while ((line = reader.readLine()) != null) {
                requestQueue.offer(new Request(line));
            }
        } catch (IOException ex) {
            Logger.getLogger(getClass().getName())
                    .log(Level.WARNING, "File named {0} did not exist will be created.", filename);
        }
    }

    @Override
    public void setExceptionListener(ExceptionListener listener) {

    }

    @Override
    public void close() {
        if (thread_cached != null) {
            thread_cached.stop();
            save("search_cache");
        }
    }
    
    private class Request {

        public Request(String screenName, int numberOfTweets) {
            this.screenName = screenName;
            this.numberOfTweets = numberOfTweets;

            sinceId = 0;
            maxId = Long.MAX_VALUE;
        }

        public Request(String parse) {
            String[] args = parse.split(":", 4);

            this.screenName = args[0];
            this.sinceId = Long.parseLong(args[1]);
            this.maxId = Long.parseLong(args[2]);
            this.numberOfTweets = Integer.parseInt(args[3]);
        }

        @Override
        public String toString() {
            return screenName + ":" + Long.toString(sinceId) + ":" + Long.toString(maxId) + ":" + Integer.toString(numberOfTweets);
        }

        public String screenName;
        public long sinceId;
        public long maxId;
        public int numberOfTweets;
    }

    /**
     * The container that creates both threads.
     */
    private class ThreadContainer {

        private final Thread ioThread;
        private final Poller poller;

        private final Thread workerThread;
        private final Worker worker;

        /**
         * The poller methods.
         */
        public ThreadContainer() {
            worker = new Worker();
            poller = new Poller(worker);

            ioThread = new Thread(poller);
            workerThread = new Thread(worker);
        }

        public void start() {
            ioThread.start();
            workerThread.start();
        }

        public void stop() {
            worker.stop();
            while (workerThread.isAlive()) {
                try {
                    workerThread.interrupt();
                    workerThread.join();
                    ioThread.join();
                } catch (InterruptedException ex) {
                    Logger.getLogger(getClass().getName())
                            .warning("Interrupted while waiting for search saving.");
                }
            }
        }
    }

    /**
     * The thread that handles all the queries and the items in the queue.
     */
    private class Worker implements Runnable {

        /**
         * The json arrays received from the requests.
         */
        private final BlockingQueue<JsonObject> receivedObjects;

        private volatile boolean running = true;

        public Worker() {
            receivedObjects = new LinkedBlockingQueue();
        }

        public boolean isRunning() {
            return running;
        }

        public boolean hasObjects() {
            return !receivedObjects.isEmpty();
        }

        public void stop() {
            running = false;
        }

        /**
         * @return The head of the received object queue.
         */
        public JsonObject getObject() throws InterruptedException {
            return receivedObjects.take();
        }

        @Override
        public void run() {
            while (running) {
                try {
                    Request request = requestQueue.take();
                    executeRequest(request);
                } catch (InterruptedException ex) {
                    if (running) {
                        getLogger().log(Level.SEVERE,
                                "Interrupted while active", ex);
                    }
                    return;
                }
            }
        }

        private void executeRequest(Request request) throws InterruptedException {
            try {
                long waittime = 0;
                
                Builder url = oauth.build(USER_TIMELINE_RESOURCE)
                        .param("screen_name", request.screenName);

                int count = Math.min(200, request.numberOfTweets);

                url.param("count", Integer.toString(count));
                if (request.maxId > 0) {
                    url.param("max_id", Long.toString(request.maxId - 1));
                }

                try {
                    Response result = url.request();

                    // Obtain the lowest id.
                    JsonArray array = result.getJson().getAsJsonArray();
                    for (JsonElement element : array) {
                        JsonObject object = element.getAsJsonObject();

                        JsonElement id = object.get("id");
                        if (id == null || !id.isJsonPrimitive()) {
                            getLogger().log(Level.WARNING, "Search {0}, id was not valid.", object);
                            continue;
                        }
                        if (id.getAsLong() <= request.maxId) {
                            request.maxId = id.getAsLong();
                        }

                        receivedObjects.offer(object);
                    }

                    request.numberOfTweets -= count;
                    // request completed, do we need more requests?
                    if (request.numberOfTweets > 0) {
                        requestQueue.offer(request);
                    }

                    if (result.getRateLimitRemaining() == 0) {
                        waittime = result.getRateLimitRemainingTime();
                    }
                } catch (RateLimitException ex) {
                    requestQueue.offer(request);
                    waittime = ex.getRateLimitRemainingTime();
                }
                
                if (waittime > 0) {
                    System.out.println("Rate limited, waiting for " + waittime + " ms");
                    sleep(waittime);
                }
            } catch (IOException ex) {
                requestQueue.offer(request);
                getLogger().log(Level.SEVERE, null, ex);
            }
        }

        private Logger getLogger() {
            return Logger.getLogger(SearchImpl.class.getName());
        }
    }

    /**
     * Polls the worker thread for leftover JSONobjects to push as results.
     */
    private class Poller implements Runnable {

        private final Worker worker;

        private Poller(Worker worker) {
            this.worker = worker;
        }

        @Override
        public void run() {
            // keep waiting for objects if the worker is alive, or fetch objects
            // if the worker has any old ones left.
            while (worker.isRunning() || worker.hasObjects()) {
                try {
                    processObject(worker.getObject());
                } catch (InterruptedException ex) {
                    // requested to stop.
                    getLogger().log(Level.SEVERE, null, ex);
                    return;
                }
            }
        }

        /**
         * Distributes a new JSONObject to the result listeners.
         *
         * @param obj
         */
        private void processObject(JsonObject obj) {
            synchronized (resultListenerSync) {
                if (resultListener != null) {
                    resultListener.tweetGenerated(obj);
                }
            }
        }

        private Logger getLogger() {
            return Logger.getLogger(SearchImpl.class.getName());
        }
    }
}