module ws.gl.gbuffer;

import
    std.string,
    ws.gl.gl;


class GBuffer {

    private {
        GLuint fbo;
        GLuint textures[NUM];
        GLuint depth;
    }

    this(int w, int h){
        // Create the FBO
        glGenFramebuffersEXT(1, &fbo);
        glBindFramebufferEXT(GL_FRAMEBUFFER, fbo);

        // Create the gbuffer textures
        glGenTextures(textures.length, textures.ptr);
        for(uint i = 0; i < textures.length; i++){
            glBindTexture(GL_TEXTURE_2D, textures[i]);
            glTexStorage2D(GL_TEXTURE_2D, 1, GL_RGB32F, w, h);
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
            glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0 + i, textures[i], 0);
        }
        // depth
        glGenTextures(1, &depth);
        glBindTexture(GL_TEXTURE_2D, depth);
        glTexStorage2D(GL_TEXTURE_2D, 1, GL_DEPTH_COMPONENT32F, w, h);
        glFramebufferTexture(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, depth, 0);

        GLenum[] drawBuffers;
        for(int i=0; i<NUM; i++)
            drawBuffers ~= GL_COLOR_ATTACHMENT0+i;
        glDrawBuffers(cast(uint)drawBuffers.length, drawBuffers.ptr);
        GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
        if(status != GL_FRAMEBUFFER_COMPLETE)
            throw new Exception("FB error %s".format(status));
        // restore default FBO
        glBindFramebuffer(GL_FRAMEBUFFER, 0);
    }

    void destroy(){
        if(fbo)
            glDeleteFramebuffers(1, &fbo);
        if(textures[0])
            glDeleteTextures(textures.length, textures.ptr);
        if(depth)
            glDeleteRenderbuffers(1, &depth);
    }

    void setRead(int type){
        glReadBuffer(GL_COLOR_ATTACHMENT0 + type);
    }

    void bindWrite(){
        glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo);
    }

    void bindRead(){
        glBindFramebuffer(GL_READ_FRAMEBUFFER, fbo);
    }

    enum: int {
        DIFFUSE, NUM
    };

}