package space.engine;

import static org.lwjgl.opengl.GL11.*;
import org.lwjgl.opengl.GLContext;
import org.newdawn.slick.SlickException;
import org.newdawn.slick.opengl.Texture;
import org.newdawn.slick.opengl.renderer.Renderer;

import static org.lwjgl.opengl.EXTFramebufferObject.GL_COLOR_ATTACHMENT0_EXT;
import static org.lwjgl.opengl.EXTFramebufferObject.GL_DEPTH_ATTACHMENT_EXT;
import static org.lwjgl.opengl.EXTFramebufferObject.GL_FRAMEBUFFER_COMPLETE_EXT;
import static org.lwjgl.opengl.EXTFramebufferObject.GL_FRAMEBUFFER_EXT;
import static org.lwjgl.opengl.EXTFramebufferObject.GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT_EXT;
import static org.lwjgl.opengl.EXTFramebufferObject.GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS_EXT;
import static org.lwjgl.opengl.EXTFramebufferObject.GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER_EXT;
import static org.lwjgl.opengl.EXTFramebufferObject.GL_FRAMEBUFFER_INCOMPLETE_FORMATS_EXT;
import static org.lwjgl.opengl.EXTFramebufferObject.GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT_EXT;
import static org.lwjgl.opengl.EXTFramebufferObject.GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER_EXT;
import static org.lwjgl.opengl.EXTFramebufferObject.GL_RENDERBUFFER_EXT;
import static org.lwjgl.opengl.EXTFramebufferObject.glBindFramebufferEXT;
import static org.lwjgl.opengl.EXTFramebufferObject.glBindRenderbufferEXT;
import static org.lwjgl.opengl.EXTFramebufferObject.glCheckFramebufferStatusEXT;
import static org.lwjgl.opengl.EXTFramebufferObject.glDeleteFramebuffersEXT;
import static org.lwjgl.opengl.EXTFramebufferObject.glDeleteRenderbuffersEXT;
import static org.lwjgl.opengl.EXTFramebufferObject.glFramebufferRenderbufferEXT;
import static org.lwjgl.opengl.EXTFramebufferObject.glFramebufferTexture2DEXT;
import static org.lwjgl.opengl.EXTFramebufferObject.glGenFramebuffersEXT;
import static org.lwjgl.opengl.EXTFramebufferObject.glGenRenderbuffersEXT;
import static org.lwjgl.opengl.EXTFramebufferObject.glRenderbufferStorageEXT;

public class FBO {

    public static boolean isSupported() {
        return GLContext.getCapabilities().GL_EXT_framebuffer_object;
    }

    /** Our render texture. */
    private Texture texture;
    /** The ID of the FBO in use */
    private int id;
    private int width, height;
    private int pushAttrib = GL_VIEWPORT_BIT | GL_TRANSFORM_BIT | GL_COLOR_BUFFER_BIT;

    public static final int NO_BITS = 0;

    public FBO(Texture texture) throws SlickException {
        if (!isSupported()) {
            throw new SlickException("Your OpenGL card does not support FBO and hence can't handle " +
                    "the dynamic images required for this application.");
        }
        this.texture = texture;
        this.width = texture.getImageWidth();
        this.height = texture.getImageHeight();
        try {
            texture.bind();
            id = glGenFramebuffersEXT();
            glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, id);
            glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT,
                                      GL_TEXTURE_2D, texture.getTextureID(), 0);
            completeCheck();
            glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
        } catch (SlickException ex) {
            throw ex;
        } catch (Exception e) {
            throw new SlickException("Failed to create new texture for FBO");
        }
    }

    public FBO(int width, int height) throws SlickException {
        this(TextureUtils.createEmptyTexture(width, height));
    }

    public void setPushAttrib(int attrib) {
        this.pushAttrib = attrib;
    }

    public int getPushAttrib() {
        return pushAttrib;
    }

    public int getWidth() {
        return width;
    }

    public int getHeight() {
        return height;
    }

    public int getID() {
        return id;
    }

    public Texture getTexture() {
        return texture;
    }

    /**
     * Check the FBO for completeness as shown in the LWJGL tutorial
     *
     * @throws SlickException Indicates an incomplete FBO
     */
    private void completeCheck() throws SlickException {
        int framebuffer = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT);
        switch ( framebuffer ) {
            case GL_FRAMEBUFFER_COMPLETE_EXT:
                break;
            case GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT_EXT:
                throw new SlickException( "FrameBuffer: " + id
                        + ", has caused a GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT_EXT exception" );
            case GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT_EXT:
                throw new SlickException( "FrameBuffer: " + id
                        + ", has caused a GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT_EXT exception" );
            case GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS_EXT:
                throw new SlickException( "FrameBuffer: " + id
                        + ", has caused a GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS_EXT exception" );
            case GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER_EXT:
                throw new SlickException( "FrameBuffer: " + id
                        + ", has caused a GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER_EXT exception" );
            case GL_FRAMEBUFFER_INCOMPLETE_FORMATS_EXT:
                throw new SlickException( "FrameBuffer: " + id
                        + ", has caused a GL_FRAMEBUFFER_INCOMPLETE_FORMATS_EXT exception" );
            case GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER_EXT:
                throw new SlickException( "FrameBuffer: " + id
                        + ", has caused a GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER_EXT exception" );
            default:
                throw new SlickException( "Unexpected reply from glCheckFramebufferStatusEXT: " + framebuffer);
        }
    }

    /**
     * Bind to the FBO created
     */
    public void bind() {
        if (id == 0)
            throw new IllegalStateException("can't use FBO as it has been destroyed..");
        if (pushAttrib != NO_BITS)
            glPushAttrib(pushAttrib);

        glViewport(0, 0, width, height);
        glMatrixMode(GL_PROJECTION);
        glPushMatrix();
        glLoadIdentity();
        glOrtho(0, width, 0, height, 1, -1);
        glMatrixMode(GL_MODELVIEW);
        glPushMatrix();
        glLoadIdentity();

        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, id);
    }

    /**
     * Unbind from the FBO created
     */
    public void unbind() {
        if (id==0)
            return;
        Renderer.get().flush();
        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);

        glMatrixMode(GL_PROJECTION);
        glPopMatrix();
        glMatrixMode(GL_MODELVIEW);
        glPopMatrix();
        if (pushAttrib != NO_BITS)
            glPopAttrib();
    }


    /**
     * @see org.newdawn.slick.Graphics#destroy()
     */
    public void release() {
        glDeleteFramebuffersEXT(id);
        id = 0;
    }
}