package atmos;

import java.text.DecimalFormat;
import java.text.MessageFormat;
import java.util.Random;

import com.badlogic.gdx.ApplicationListener;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.Input.Keys;
import com.badlogic.gdx.InputAdapter;
import com.badlogic.gdx.backends.lwjgl.LwjglApplication;
import com.badlogic.gdx.backends.lwjgl.LwjglApplicationConfiguration;
import com.badlogic.gdx.graphics.Color;
import com.badlogic.gdx.graphics.GL10;
import com.badlogic.gdx.graphics.OrthographicCamera;
import com.badlogic.gdx.graphics.Pixmap;
import com.badlogic.gdx.graphics.Pixmap.Format;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.BitmapFont;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;
import com.badlogic.gdx.graphics.glutils.ShaderProgram;
import com.badlogic.gdx.math.Matrix4;
import com.badlogic.gdx.math.Vector2;
import com.badlogic.gdx.math.Vector3;

/**
 * Simple illumination model with shaders in LibGDX.
 * @author davedes
 */
public class Illumination2D implements ApplicationListener {

    Texture texture, texture_n;

    boolean flipY;
    Texture normalBase;
    OrthographicCamera cam;
    SpriteBatch fxBatch, batch;

    Matrix4 transform = new Matrix4();

    Random rnd = new Random();

    // position of our light
    final Vector3 DEFAULT_LIGHT_POS = new Vector3(0f, 0f, 0.07f);
    // the color of our light
    final Vector3 DEFAULT_LIGHT_COLOR = new Vector3(1f, 0.7f, 0.6f);
    // the ambient color (color to use when unlit)
    final Vector3 DEFAULT_AMBIENT_COLOR = new Vector3(0.3f, 0.3f, 1f);
    // the attenuation factor: x=constant, y=linear, z=quadratic
    final Vector3 DEFAULT_ATTENUATION = new Vector3(0.4f, 3f, 20f);
    // the ambient intensity (brightness to use when unlit)
    final float DEFAULT_AMBIENT_INTENSITY = 0.2f;
    final float DEFAULT_STRENGTH = 1f;

    final Color NORMAL_VCOLOR = new Color(1f,1f,1f,DEFAULT_STRENGTH);

    // the position of our light in 3D space
    Vector3 lightPos = new Vector3(DEFAULT_LIGHT_POS);
    // the resolution of our game/graphics
    Vector2 resolution = new Vector2();
    // the current attenuation
    Vector3 attenuation = new Vector3(DEFAULT_ATTENUATION);
    // the current ambient intensity
    float ambientIntensity = DEFAULT_AMBIENT_INTENSITY;
    float strength = DEFAULT_STRENGTH;

    // whether to use attenuation/shadows
    boolean useShadow = true;

    // whether to use lambert shading (with our normal map)
    boolean useNormals = true;

    DecimalFormat DEC_FMT = new DecimalFormat("0.00000");

    ShaderProgram program;

    BitmapFont font;

    private int texWidth, texHeight;

    final String TEXT = "Use number keys to adjust parameters:\n" +
            "1: Randomize Ambient Color\n" +
            "2: Randomize Ambient Intensity {0}\n" +
            "3: Randomize Light Color\n" +
            "4/5: Increase/decrease constant attenuation: {1}\n" +
            "6/7: Increase/decrease linear attenuation: {2}\n" +
            "8/9: Increase/decrease quadratic attenuation: {3}\n" +
            "0: Reset parameters\n" +
            "RIGHT/LEFT: Increase/decrease normal map intensity: {4}\n" +
            "UP/DOWN: Increase/decrease lightDir.z: {5}\n\n" +
            "S toggles attenuation, N toggles normal shading\n" +
            "T to toggle textures";

    private Texture rock, rock_n, teapot, teapot_n;

    public void create() {
        // load our textures
        rock = new Texture(Gdx.files.internal("data/teapot.png"));
        rock_n = new Texture(Gdx.files.internal("data/teapot_n.png"));
        teapot = new Texture(Gdx.files.internal("data/rock.png"));
        teapot_n = new Texture(Gdx.files.internal("data/rock_n.png"));

        texture = teapot;
        texture_n = teapot_n;
        flipY = texture==rock;

        //we only use this to show what the strength-adjusted normal map looks like on screen
        Pixmap pix = new Pixmap(1, 1, Format.RGB565);
        pix.setColor(0.5f, 0.5f, 1.0f, 1.0f);
        pix.fill();
        normalBase = new Texture(pix);

        texWidth = texture.getWidth();
        texHeight = texture.getHeight();

        // a simple 2D orthographic camera
        cam = new OrthographicCamera(Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
        cam.setToOrtho(false);

        // create our shader program...
        program = createShader();

        // now we create our sprite batch for our shader
        fxBatch = new SpriteBatch(100, program);
        // setShader is needed; perhaps this is a LibGDX bug?
        fxBatch.setShader(program);
        fxBatch.setProjectionMatrix(cam.combined);
        fxBatch.setTransformMatrix(transform);

        // usually we would just use a single batch for our application,
        // but for demonstration let's also show the un-affected image
        batch = new SpriteBatch(100);
        batch.setProjectionMatrix(cam.combined);
        batch.setTransformMatrix(transform);

        // quick little input for debugging -- press S to toggle shadows, N to
        // toggle normals
        Gdx.input.setInputProcessor(new InputAdapter() {
            public boolean keyDown(int key) {
                if (key == Keys.S) {
                    useShadow = !useShadow;
                    return true;
                } else if (key == Keys.N) {
                    useNormals = !useNormals;
                    return true;
                } else if (key == Keys.NUM_1) {
                    program.begin();
                    program.setUniformf("ambientColor", rndColor());
                    program.end();
                    return true;
                } else if (key == Keys.NUM_2) {
                    ambientIntensity = rnd.nextFloat();
                    return true;
                } else if (key == Keys.NUM_3) {
                    program.begin();
                    program.setUniformf("lightColor", rndColor());
                    program.end();
                    return true;
                } else if (key == Keys.NUM_0) {
                    attenuation.set(DEFAULT_ATTENUATION);
                    ambientIntensity = DEFAULT_AMBIENT_INTENSITY;
                    lightPos.set(DEFAULT_LIGHT_POS);
                    strength = DEFAULT_STRENGTH;
                    program.begin();
                    program.setUniformf("lightColor", DEFAULT_LIGHT_COLOR);
                    program.setUniformf("ambientColor", DEFAULT_AMBIENT_COLOR);
                    program.setUniformf("ambientIntensity", ambientIntensity);
                    program.setUniformf("attenuation", attenuation);
                    program.setUniformf("lightPos", lightPos);
                    program.setUniformf("strength", strength);
                    program.end();
                } else if (key == Keys.T) {
                    texture = texture==teapot ? rock : teapot;
                    texture_n = texture_n==teapot_n ? rock_n : teapot_n;
                    flipY = texture==rock;
                    texWidth = texture.getWidth();
                    texHeight = texture.getHeight();
                    program.begin();
                    program.setUniformi("yInvert", flipY ? 1 : 0);
                    program.end();
                }
                return false;
            }
        });

        font = new BitmapFont();
    }

    private Vector3 rndColor() {
        return new Vector3(rnd.nextFloat(), rnd.nextFloat(), rnd.nextFloat());
    }

    private ShaderProgram createShader() {
        // see the code here: http://pastebin.com/7fkh1ax8
        // simple illumination model using ambient, diffuse (lambert) and attenuation
        // see here: http://nccastaff.bournemouth.ac.uk/jmacey/CGF/slides/IlluminationModels4up.pdf
        String vert = "attribute vec4 " + ShaderProgram.POSITION_ATTRIBUTE + ";\n" //
                + "attribute vec4 " + ShaderProgram.COLOR_ATTRIBUTE + ";\n" //
                + "attribute vec2 " + ShaderProgram.TEXCOORD_ATTRIBUTE + "0;\n" //
                + "uniform mat4 u_proj;\n" //
                + "uniform mat4 u_trans;\n" //
                + "uniform mat4 u_projTrans;\n" //
                + "varying vec4 v_color;\n" //
                + "varying vec2 v_texCoords;\n" //
                + "\n" //
                + "void main()\n" //
                + "{\n" //
                + "   v_color = " + ShaderProgram.COLOR_ATTRIBUTE + ";\n" //
                + "   v_texCoords = " + ShaderProgram.TEXCOORD_ATTRIBUTE + "0;\n" //
                + "   gl_Position =  u_projTrans * " + ShaderProgram.POSITION_ATTRIBUTE + ";\n" //
                + "}\n";

        String frag = "#ifdef GL_ES\n" +
                "precision mediump float;\n" +
                "#endif\n" +
                "varying vec4 v_color;\n" +
                "varying vec2 v_texCoords;\n" +

                "uniform sampler2D u_texture;\n" +
                "uniform sampler2D u_normals;\n" +
                "uniform vec3 light;\n" +
                "uniform vec3 ambientColor;\n" +
                "uniform float ambientIntensity; \n" +
                "uniform vec2 resolution;\n" +
                "uniform vec3 lightColor;\n" +
                "uniform bool useNormals;\n" +
                "uniform bool useShadow;\n" +
                "uniform vec3 attenuation;\n" +
                "uniform float strength;\n" +
                "uniform bool yInvert;\n"+
                "\n" +
                "void main() {\n" +
                "   //sample color & normals from our textures\n" +
                "   vec4 color = texture2D(u_texture, v_texCoords.st);\n" +
                "   vec3 nColor = texture2D(u_normals, v_texCoords.st).rgb;\n\n" +
                "   //some bump map programs will need the Y value flipped..\n" +
                "   nColor.g = yInvert ? 1.0 - nColor.g : nColor.g;\n\n" +
                "   //this is for debugging purposes, allowing us to lower the intensity of our bump map\n" +
                "   vec3 nBase = vec3(0.5, 0.5, 1.0);\n" +
                "   nColor = mix(nBase, nColor, strength);\n\n" +
                "   //normals need to be converted to [-1.0, 1.0] range and normalized\n" +
                "   vec3 normal = normalize(nColor * 2.0 - 1.0);\n\n" +
                "   //here we do a simple distance calculation\n" +
                "   vec3 deltaPos = vec3( (light.xy - gl_FragCoord.xy) / resolution.xy, light.z );\n\n" +
                "   vec3 lightDir = normalize(deltaPos);\n" +
                "   float lambert = useNormals ? clamp(dot(normal, lightDir), 0.0, 1.0) : 1.0;\n" +
                "   \n" +
                "   //now let's get a nice little falloff\n" +
                "   float d = sqrt(dot(deltaPos, deltaPos));"+
                "   \n" +
                "   float att = useShadow ? 1.0 / ( attenuation.x + (attenuation.y*d) + (attenuation.z*d*d) ) : 1.0;\n" +
                "   \n" +
                "   vec3 result = (ambientColor * ambientIntensity) + (lightColor.rgb * lambert) * att;\n" +
                "   result *= color.rgb;\n" +
                "   \n" +
                "   gl_FragColor = v_color * vec4(result, color.a);\n" +
                "}";
        System.out.println("VERTEX PROGRAM:\n------------\n\n"+vert);
        System.out.println("FRAGMENT PROGRAM:\n------------\n\n"+frag);
        ShaderProgram program = new ShaderProgram(vert, frag);
        // u_proj and u_trans will not be active but SpriteBatch will still try to set them...
        program.pedantic = false;
        if (program.isCompiled() == false)
            throw new IllegalArgumentException("couldn't compile shader: "
                    + program.getLog());

        // set resolution vector
        resolution.set(Gdx.graphics.getWidth(), Gdx.graphics.getHeight());

        // we are only using this many uniforms for testing purposes...!!
        program.begin();
        program.setUniformi("u_texture", 0);
        program.setUniformi("u_normals", 1);
        program.setUniformf("light", lightPos);
        program.setUniformf("strength", strength);
        program.setUniformf("ambientIntensity", ambientIntensity);
        program.setUniformf("ambientColor", DEFAULT_AMBIENT_COLOR);
        program.setUniformf("resolution", resolution);
        program.setUniformf("lightColor", DEFAULT_LIGHT_COLOR);
        program.setUniformf("attenuation", attenuation);
        program.setUniformi("useShadow", useShadow ? 1 : 0);
        program.setUniformi("useNormals", useNormals ? 1 : 0);
        program.setUniformi("yInvert", flipY ? 1 : 0);
        program.end();

        return program;
    }

    public void dispose() {
        fxBatch.dispose();
        batch.dispose();
        texture.dispose();
        texture_n.dispose();
    }

    public void render() {
        Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);

        // draw our sprites without any effects
        batch.begin();

        final int IMG_Y = texHeight/2;

        //let's first simulate our resulting normal map by blending a blue square atop it
        //we also could have achieved this with glTexEnv in the fixed function pipeline
        NORMAL_VCOLOR.a = 1.0f - strength;
        batch.draw(texture_n, texWidth + 10, IMG_Y);
        batch.setColor(NORMAL_VCOLOR);
        batch.draw(normalBase, texWidth + 10, IMG_Y, texWidth, texHeight);
        batch.setColor(Color.WHITE);
        batch.draw(texture, 0, IMG_Y);
        //now let's simulate how our normal map will be sampled using strength
        //we can do this simply by blending a blue fill overtop

        String str = MessageFormat.format(TEXT, ambientIntensity,
                attenuation.x, attenuation.y, DEC_FMT.format(attenuation.z),
                strength, lightPos.z);
        font.drawMultiLine(batch, str, 10, Gdx.graphics.getHeight()-10);

        font.draw(batch, "Diffuse Color", 10, IMG_Y+texHeight + 30);
        font.draw(batch, "Normal Map", texWidth+20, IMG_Y+texHeight + 30);
        font.draw(batch, "Final Color", texWidth*2+30, IMG_Y+texHeight + 30);
        batch.end();

        // start our FX batch, which will bind our shader program
        fxBatch.begin();

        // get y-down light position based on mouse/touch
        lightPos.x = Gdx.input.getX();
        lightPos.y = Gdx.graphics.getHeight() - Gdx.input.getY();

        // handle attenuation input
        if (Gdx.input.isKeyPressed(Keys.NUM_4)) {
            attenuation.x += 0.025f;
        } else if (Gdx.input.isKeyPressed(Keys.NUM_5)) {
            attenuation.x -= 0.025f;
            if (attenuation.x < 0)
                attenuation.x = 0;
        } else if (Gdx.input.isKeyPressed(Keys.NUM_6)) {
            attenuation.y += 0.25f;
        } else if (Gdx.input.isKeyPressed(Keys.NUM_7)) {
            attenuation.y -= 0.25f;
            if (attenuation.y < 0)
                attenuation.y = 0;
        } else if (Gdx.input.isKeyPressed(Keys.NUM_8)) {
            attenuation.z += 0.25f;
        } else if (Gdx.input.isKeyPressed(Keys.NUM_9)) {
            attenuation.z -= 0.25f;
            if (attenuation.z < 0)
                attenuation.z = 0;
        } else if (Gdx.input.isKeyPressed(Keys.RIGHT)) {
            strength += 0.025f;
            if (strength > 1f)
                strength = 1f;
        } else if (Gdx.input.isKeyPressed(Keys.LEFT)) {
            strength -= 0.025f;
            if (strength < 0)
                strength = 0;
        } else if (Gdx.input.isKeyPressed(Keys.UP)) {
            lightPos.z += 0.0025f;
        } else if (Gdx.input.isKeyPressed(Keys.DOWN)) {
            lightPos.z -= 0.0025f;
        }

        // update our uniforms
        program.setUniformf("ambientIntensity", ambientIntensity);
        program.setUniformf("attenuation", attenuation);
        program.setUniformf("light", lightPos);
        program.setUniformi("useNormals", useNormals ? 1 : 0);
        program.setUniformi("useShadow", useShadow ? 1 : 0);
        program.setUniformf("strength", strength);

        // bind the normal first at texture1
        texture_n.bind(1);

        // bind the actual texture at texture0
        texture.bind(0);

        // we bind texture0 second since draw(texture) will end up binding it at
        // texture0...
        fxBatch.draw(texture, texWidth*2 + 20, IMG_Y);
        fxBatch.end();
    }

    public void resize(int width, int height) {
        cam.setToOrtho(false, width, height);
        resolution.set(width, height);
        program.setUniformf("resolution", resolution);
    }

    public void pause() {
    }

    public void resume() {
    }

    public static void main(String[] args) {
        LwjglApplicationConfiguration cfg = new LwjglApplicationConfiguration();
        cfg.title = "Lighting Test";
        cfg.useGL20 = true;
        cfg.width = 1024;
        cfg.height = 768;
        cfg.resizable = false;

        new LwjglApplication(new Illumination2D(), cfg);
    }
}