package ch.epfl.maze.graphics;

import ch.epfl.maze.physical.World;
import ch.epfl.maze.simulation.Simulation;

import javax.imageio.ImageIO;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferStrategy;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

/**
 * Handles the display of a {@code Simulation} on a window.
 *
 * @author EPFL
 */
public final class Display implements Runnable {

    /* constants */
    public static final Color BACKGROUND_COLOR = Color.GRAY;
    public static final int SQUARE_SIZE = 42;
    public static final int BUFFERS_NUMBER = 2;
    public static final int MAX_SPEED = 32;
    public static final int DEFAULT_SPEED = 2;
    public static final int MIN_SPEED = 1;
    public static final int ANIMATION_SLEEP = 10;

    /* lock for mutual exclusion between human interactions and display */
    private final Object mLock = new Object();

    /* simulation and animation handlers */
    private final Simulation mSimulation;
    private final Animation mAnimation;
    private volatile float mSpeed;

    /* actual window frame and canvas */
    private JFrame mFrame;
    private JMenuBar mMenuBar;
    private Canvas mCanvas;

    /* drawing buffers */
    private BufferStrategy mStrategy;
    private Map<Integer, BufferedImage> mTiles;

    /* control variables */
    private boolean mRunning;
    private boolean mPaused;
    private boolean mShowGrid;
    private boolean mDebug;
    private boolean mFinished;

    /**
     * Constructs a {@code Display} that will display a simulation.
     *
     * @param simulation A {@code Simulation} to display
     */
    public Display(Simulation simulation) {
        // sanity check
        if (simulation == null) {
            throw new IllegalArgumentException("Simulation must be defined.");
        }
        if (simulation.getWorld() == null) {
            throw new IllegalArgumentException("World in Simulation must be defined.");
        }

        // initiates instances
        mSimulation = simulation;
        mAnimation = new Animation(simulation.getWorld().getAnimals());
        mSpeed = DEFAULT_SPEED;

        // default control variables
        mRunning = true;
        mPaused = false;
        mShowGrid = false;
        mDebug = false;
        mFinished = false;

        // creates menu
        createMenu();

        // creates canvas
        createCanvas();

        // creates window
        createWindow();

        // sets canvas and menu on frame
        mFrame.setJMenuBar(mMenuBar);
        mFrame.add(mCanvas);
        mFrame.pack();
        mFrame.setLocationRelativeTo(null);

        // creates buffer strategy
        mCanvas.createBufferStrategy(BUFFERS_NUMBER);
        mStrategy = mCanvas.getBufferStrategy();

        // loads images of tiles
        mTiles = new HashMap<Integer, BufferedImage>();
        try {
            mTiles.put(World.FREE, ImageIO.read(new File("img/tiles/free.png")));
            mTiles.put(World.WALL, ImageIO.read(new File("img/tiles/wall.png")));
            mTiles.put(World.START, ImageIO.read(new File("img/tiles/start.png")));
            mTiles.put(World.EXIT, ImageIO.read(new File("img/tiles/exit.png")));
            mTiles.put(World.NOTHING, ImageIO.read(new File("img/tiles/nothing.png")));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void run() {
        mFrame.setVisible(true);
        mainLoop();
        mFrame.dispose();
    }

    /**
     * Sets the debug control.
     *
     * @param debug The new debug value
     */
    public void setDebug(boolean debug) {
        mDebug = debug;
        mShowGrid = debug;
        createMenu();
        mFrame.setJMenuBar(mMenuBar);
    }

    /**
     * Creates frame window.
     */
    private void createWindow() {
        // actual window
        mFrame = new JFrame("Maze solver simulation");

        // redefines closing operation
        mFrame.setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);
        mFrame.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                synchronized (mLock) {
                    mRunning = false;
                }
            }
        });

        // sets up various options to make it look good
        mFrame.setIgnoreRepaint(false);
        mFrame.setBackground(BACKGROUND_COLOR);
        mFrame.setFocusable(false);
        mFrame.setFocusTraversalKeysEnabled(false);
        mFrame.setResizable(false);
        System.setProperty("sun.awt.noerasebackground", "true");
    }

    /**
     * Creates canvas.
     */
    private void createCanvas() {
        // actual canvas
        mCanvas = new Canvas();

        // sets canvas size
        int height = SQUARE_SIZE * mSimulation.getWorld().getHeight();
        int width = SQUARE_SIZE * mSimulation.getWorld().getWidth();
        mCanvas.setSize(width, height);

        // sets up options to make it look good
        mCanvas.setIgnoreRepaint(true);
        mCanvas.setBackground(Color.BLACK);
        mCanvas.setFocusable(true);
        mCanvas.setFocusTraversalKeysEnabled(false);
    }

    /**
     * Creates menu.
     */
    private void createMenu() {
        // creates menu bar
        mMenuBar = new JMenuBar();

        // creates "Maze" menu
        JMenu menu = new JMenu("Simulation");
        menu.setMnemonic(KeyEvent.VK_M);
        menu.setToolTipText("Contains main manipulation options.");
        mMenuBar.add(menu);

        // creates menu items
        // "Stop"
        JMenuItem stopItem = new JMenuItem("Stop", KeyEvent.VK_S);
        stopItem.setToolTipText("Stops simulation in its current state.");
        stopItem.setAccelerator(KeyStroke.getKeyStroke("control W"));
        stopItem.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                synchronized (mLock) {
                    mSimulation.stop();
                    mAnimation.reset(null);
                    mPaused = false;
                }
            }
        });
        menu.add(stopItem);

        // "Restart"
        JMenuItem restart = new JMenuItem("Restart", KeyEvent.VK_R);
        restart.setToolTipText("Restarts the simulation from the beginning.");
        restart.setAccelerator(KeyStroke.getKeyStroke("control R"));
        restart.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                synchronized (mLock) {
                    mSimulation.restart();
                    mAnimation.reset(mSimulation.getWorld().getAnimals());
                    mPaused = false;
                    mFinished = false;
                }
            }
        });
        menu.add(restart);

        // ==========================================================
        menu.addSeparator();

        // "Pause"
        final JMenuItem pauseItem = new JMenuItem(mDebug ? "Next step" :
                (mPaused ? "Resume" : "Pause"), KeyEvent.VK_P);
        pauseItem.setAccelerator(KeyStroke.getKeyStroke("SPACE"));
        pauseItem.setToolTipText("Pauses simulation.");
        pauseItem.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                synchronized (mLock) {
                    if (mPaused) {
                        mPaused = false;
                        if (!mDebug) {
                            pauseItem.setText("Pause");
                        }
                    } else {
                        mPaused = true;
                        if (!mDebug) {
                            pauseItem.setText("Resume");
                        }
                    }
                }
                ;
            }
        });
        menu.add(pauseItem);

        // "Debug mode"
        JCheckBoxMenuItem debugItem = new JCheckBoxMenuItem("Debug mode");
        debugItem.setState(mDebug);
        debugItem.setMnemonic(KeyEvent.VK_M);
        debugItem.setAccelerator(KeyStroke.getKeyStroke("alt G"));
        debugItem.setToolTipText("Enters in debug mode, allowing to move animals step by step.");
        menu.add(debugItem);

        // ==========================================================
        menu.addSeparator();

        // "Accelerate"
        final JMenuItem accelerateItem = new JMenuItem("Accelerate",
                KeyEvent.VK_A);
        // "Decelerate"
        final JMenuItem decelerateItem = new JMenuItem("Decelerate",
                KeyEvent.VK_D);

        accelerateItem.setToolTipText("Increases simulation speed up to a maximum.");
        decelerateItem.setToolTipText("Decreases simulation speed down to a minimum.");

        accelerateItem.setAccelerator(KeyStroke.getKeyStroke('+'));
        decelerateItem.setAccelerator(KeyStroke.getKeyStroke('-'));

        accelerateItem.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                synchronized (mLock) {
                    decelerateItem.setEnabled(true);
                    if (mSpeed < MAX_SPEED) {
                        mSpeed *= 2;
                    }
                    if (mSpeed == MAX_SPEED) {
                        accelerateItem.setEnabled(false);
                    }
                }
            }
        });
        decelerateItem.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                synchronized (mLock) {
                    accelerateItem.setEnabled(true);
                    if (mSpeed > MIN_SPEED) {
                        mSpeed /= 2;
                    }
                    if (mSpeed == MIN_SPEED) {
                        decelerateItem.setEnabled(false);
                    }
                }
            }
        });

        menu.add(accelerateItem);
        menu.add(decelerateItem);

        // ==========================================================
        menu.addSeparator();

        // "Show grid"
        final JCheckBoxMenuItem gridItem = new JCheckBoxMenuItem("Show grid");
        gridItem.setState(mShowGrid);
        gridItem.setMnemonic(KeyEvent.VK_G);
        gridItem.setToolTipText("Criss-crosses the maze tiles.");
        gridItem.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                synchronized (mLock) {
                    mShowGrid = !mShowGrid;
                    gridItem.setState(mShowGrid);
                }
            }
        });
        debugItem.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                synchronized (mLock) {
                    if (!mDebug) {
                        mDebug = true;
                        mShowGrid = true;
                        pauseItem.setText("Next Step");

                    } else {
                        mShowGrid = false;
                        mPaused = false;
                        mDebug = false;
                        pauseItem.setText("Pause");
                    }
                    gridItem.setState(mShowGrid);
                }
            }
        });
        menu.add(gridItem);

        // "Exit"
        JMenuItem exitItem = new JMenuItem("Exit", KeyEvent.VK_E);
        exitItem.setToolTipText("Exits program.");
        exitItem.setAccelerator(KeyStroke.getKeyStroke("ESCAPE"));
        exitItem.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                synchronized (mLock) {
                    mRunning = false;
                }
            }
        });
        menu.add(exitItem);
    }

    /**
     * Draws the labyrinth being simulated.
     *
     * @param g The graphics on which the labyrinth will be drawn
     */
    private void drawLabyrinth(Graphics2D g) {
        World world = mSimulation.getWorld();

        BufferedImage tile;
        for (int y = 0; y < world.getHeight(); y++) {
            for (int x = 0; x < world.getWidth(); x++) {
                // retrieves corresponding image
                tile = mTiles.get(world.getTile(x, y));
                if (tile == null) {
                    tile = mTiles.get(World.WALL);
                }

                int width = x * SQUARE_SIZE;
                int height = y * SQUARE_SIZE;

                g.drawImage(tile, width, height, mFrame);

                if (mShowGrid) {
                    g.setColor(BACKGROUND_COLOR);
                    g.drawRect(width, height, SQUARE_SIZE, SQUARE_SIZE);
                }
            }
        }
    }

    /**
     * Draws the actual animation of the display.
     *
     * @param dt     The elapsed time between two frames
     * @param g      The graphics on which the animation will be drawn
     * @param width  Width of graphics
     * @param height Height of graphics
     */
    private void drawAnimation(float dt, Graphics2D g, int width, int height) {
        // clears background
        g.setColor(BACKGROUND_COLOR);
        g.fillRect(0, 0, width, height);

        // paints maze
        drawLabyrinth(g);

        synchronized (mLock) {
            // paints next animation frame
            mAnimation.paint(dt, g, mFrame);

            if (mAnimation.isDone()) {
                // determines if maze is solved
                if (!mFinished && mSimulation.isOver()) {
                    mFinished = true;
                    final String recordTable = mSimulation.getRecordTable();

                    // message dialog to invoke later, to prevent Display from
                    // crashing when a key is being held
                    EventQueue.invokeLater(new Runnable() {
                        @Override
                        public void run() {
                            JOptionPane.showMessageDialog(null, "Simulation is complete.\n\n" + recordTable);
                        }
                    });
                    mPaused = true;
                } else {
                    if (mDebug) {
                        mPaused = true;
                    }
                    nextMove();
                }
            }
        }
    }

    /**
     * Controls the graphics environment for the animation of the display.
     *
     * @param dt The elapsed time between two frames
     */
    private void animate(float dt) {
        Graphics2D g = null;
        try {
            // retrieves Graphics2D from strategy
            g = (Graphics2D) mStrategy.getDrawGraphics();

            // sets options
            g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                    RenderingHints.VALUE_ANTIALIAS_ON);
            g.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING,
                    RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
            drawAnimation(dt, g, mCanvas.getWidth(), mCanvas.getHeight());
        } finally {
            if (g != null) {
                // to call at the end
                g.dispose();
            }
        }

        // displays the buffer
        mStrategy.show();
    }

    /**
     * Runs the animation main loop.
     */
    private void mainLoop() {
        long before = System.nanoTime();
        while (mRunning) {
            if (mPaused || mFinished) {
                animate(0);
                before = System.nanoTime();
            } else {
                long now = System.nanoTime();
                float dt = (now - before) * 0.000000001f * mSpeed;
                if (dt < 0.001f) {
                    dt = 0.001f;
                }

                animate(dt);

                before = now;
            }

            try {
                Thread.sleep(ANIMATION_SLEEP);
            } catch (InterruptedException e) {
                // do nothing
            }
        }

        // paints a last frame
        animate(0);
    }

    /**
     * Computes the {@code Simulation}'s next move.
     */
    private void nextMove() {
        synchronized (mLock) {
            if (mRunning) {
                mSimulation.move(mAnimation);
            }
        }
    }

}