/*

 File: ES2Renderer.m

 Abstract: The ES2Renderer class creates an OpenGL ES 2.0 context and draws 

 using OpenGL ES 2.0 shaders.

 Version: 1.0

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*/

#import "ES2Renderer.h"

#import "Shaders.h"

#include "matrix.h"

// uniform index

enum {

    UNIFORM_MODELVIEW_PROJECTION_MATRIX,

    NUM_UNIFORMS

};

GLint uniforms[NUM_UNIFORMS];

// attribute index

enum {

    ATTRIB_VERTEX,

    ATTRIB_COLOR,

    NUM_ATTRIBUTES

};

@interface ES2Renderer (PrivateMethods)

- (BOOL) loadShaders;

@end

@implementation ES2Renderer

// Create an ES 2.0 context

- (id <ESRenderer>) init

{

    if (self = [super init])

    {

        context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];

        if (!context || ![EAGLContext setCurrentContext:context] || ![self loadShaders])

        {

            [self release];

            return nil;

        }

        // Create default framebuffer object. The backing will be allocated for the current layer in -resizeFromLayer

        glGenFramebuffers(1, &defaultFramebuffer);

        glGenRenderbuffers(1, &colorRenderbuffer);

        glBindFramebuffer(GL_FRAMEBUFFER, defaultFramebuffer);

        glBindRenderbuffer(GL_RENDERBUFFER, colorRenderbuffer);

        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, colorRenderbuffer);

    }

    return self;

}

- (void)render {

    // Replace the implementation of this method to do your own custom drawing

    const GLfloat squareVertices[] = {

        -0.5f, -0.5f,

        0.5f,  -0.5f,

        -0.5f,  0.5f,

        0.5f,   0.5f,

    };

    const GLubyte squareColors[] = {

        255, 255,   0, 255,

        0,   255, 255, 255,

        0,     0,   0,   0,

        255,   0, 255, 255,

    };

    [EAGLContext setCurrentContext:context];

    glBindFramebuffer(GL_FRAMEBUFFER, defaultFramebuffer);

    glViewport(0, 0, backingWidth, backingHeight);

    glClearColor(0.5f, 0.4f, 0.5f, 1.0f);

    glClear(GL_COLOR_BUFFER_BIT);

    // use shader program

    glUseProgram(program);

    // handle viewing matrices

    GLfloat proj[16], modelview[16], modelviewProj[16];

    // setup projection matrix (orthographic)

    mat4f_LoadOrtho(-1.0f, 1.0f, -1.5f, 1.5f, -1.0f, 1.0f, proj);

    // setup modelview matrix (rotate around z)

    mat4f_LoadZRotation(rotz, modelview);

    // projection matrix * modelview matrix

    mat4f_MultiplyMat4f(proj, modelview, modelviewProj);

    rotz += 3.0f * M_PI / 180.0f;

    // update uniform values

    glUniformMatrix4fv(uniforms[UNIFORM_MODELVIEW_PROJECTION_MATRIX], 1, GL_FALSE, modelviewProj);

    // update attribute values

    glVertexAttribPointer(ATTRIB_VERTEX, 2, GL_FLOAT, 0, 0, squareVertices);

    glEnableVertexAttribArray(ATTRIB_VERTEX);

    glVertexAttribPointer(ATTRIB_COLOR, 4, GL_UNSIGNED_BYTE, 1, 0, squareColors); //enable the normalized flag

    glEnableVertexAttribArray(ATTRIB_COLOR);

    // Validate program before drawing. This is a good check, but only really necessary in a debug build.

    // DEBUG macro must be defined in your debug configurations if that's not already the case.

#if defined(DEBUG)

    if (![self validateProgram:program])

    {

        NSLog(@"Failed to validate program: %d", program);

        return;

    }

#endif

    // draw

    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

    glBindRenderbuffer(GL_RENDERBUFFER, colorRenderbuffer);

    [context presentRenderbuffer:GL_RENDERBUFFER];

}

- (BOOL)loadShaders {

    GLuint vertShader, fragShader;

    NSString *vertShaderPathname, *fragShaderPathname;

    // create shader program

    program = glCreateProgram();

    // create and compile vertex shader

    vertShaderPathname = [[NSBundle mainBundle] pathForResource:@"template" ofType:@"vsh"];

    if (!compileShader(&vertShader, GL_VERTEX_SHADER, 1, vertShaderPathname)) {

        destroyShaders(vertShader, fragShader, program);

        return NO;

    }

    // create and compile fragment shader

    fragShaderPathname = [[NSBundle mainBundle] pathForResource:@"template" ofType:@"fsh"];

    if (!compileShader(&fragShader, GL_FRAGMENT_SHADER, 1, fragShaderPathname)) {

        destroyShaders(vertShader, fragShader, program);

        return NO;

    }

    // attach vertex shader to program

    glAttachShader(program, vertShader);

    // attach fragment shader to program

    glAttachShader(program, fragShader);

    // bind attribute locations

    // this needs to be done prior to linking

    glBindAttribLocation(program, ATTRIB_VERTEX, "position");

    glBindAttribLocation(program, ATTRIB_COLOR, "color");

    // link program

    if (!linkProgram(program)) {

        destroyShaders(vertShader, fragShader, program);

        return NO;

    }

    // get uniform locations

    uniforms[UNIFORM_MODELVIEW_PROJECTION_MATRIX] = glGetUniformLocation(program, "modelViewProjectionMatrix");

    // release vertex and fragment shaders

    if (vertShader) {

        glDeleteShader(vertShader);

        vertShader = 0;

    }

    if (fragShader) {

        glDeleteShader(fragShader);

        fragShader = 0;

    }

    return YES;

}

- (BOOL) resizeFromLayer:(CAEAGLLayer *)layer

{

    // Allocate color buffer backing based on the current layer size

    glBindRenderbuffer(GL_RENDERBUFFER, colorRenderbuffer);

    [context renderbufferStorage:GL_RENDERBUFFER fromDrawable:layer];

    glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH, &backingWidth);

    glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_HEIGHT, &backingHeight);

    if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)

    {

        NSLog(@"Failed to make complete framebuffer object %x", glCheckFramebufferStatus(GL_FRAMEBUFFER));

        return NO;

    }

    return YES;

}

- (void) dealloc

{

    // tear down GL

    if (defaultFramebuffer)

    {

        glDeleteFramebuffers(1, &defaultFramebuffer);

        defaultFramebuffer = 0;

    }

    if (colorRenderbuffer)

    {

        glDeleteRenderbuffers(1, &colorRenderbuffer);

        colorRenderbuffer = 0;

    }

    // realease the shader program object

    if (program)

    {

        glDeleteProgram(program);

        program = 0;

    }

    // tear down context

    if ([EAGLContext currentContext] == context)

        [EAGLContext setCurrentContext:nil];

    [context release];

    context = nil;

    [super dealloc];

}

@end