/*

 Copyright (C) 2015 Apple Inc. All Rights Reserved.

 See LICENSE.txt for this sample’s licensing information

 Abstract:

 The main rendering code.

 */

#import "ES2Renderer.h"

#import <OpenGLES/ES2/gl.h>

#import <OpenGLES/ES2/glext.h>

@interface ES2Renderer ()

{

    EAGLContext* _context;

    // The OpenGL names for the framebuffer and renderbuffer used to render to this view

    GLuint _colorRenderbuffer;

    GLuint _depthRenderbuffer;

}

@end

@implementation ES2Renderer

// Create an ES 2.0 context

- (instancetype)initWithContext:(EAGLContext*)context AndDrawable:(id<EAGLDrawable>)drawable

{

    // Create default framebuffer object. The backing will be allocated for the

    // current layer in -resizeFromLayer

    GLuint defaultFBOName;

    glGenFramebuffers(1, &defaultFBOName);

    glGenRenderbuffers(1, &_colorRenderbuffer);

    glBindFramebuffer(GL_FRAMEBUFFER, defaultFBOName);

    glBindRenderbuffer(GL_RENDERBUFFER, _colorRenderbuffer);

    _context = context;

    // This call associates the storage for the current render buffer with the

    // EAGLDrawable (our CAEAGLLayer) allowing us to draw into a buffer that

    // will later be rendered to the screen wherever the layer is (which

    // corresponds with our view).

    [_context renderbufferStorage:GL_RENDERBUFFER fromDrawable:drawable];

    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, _colorRenderbuffer);

    // Get the drawable buffer's width and height so we can create a depth buffer for the FBO

    GLint backingWidth;

    GLint backingHeight;

    glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH, &backingWidth);

    glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_HEIGHT, &backingHeight);

    // Create a depth buffer to use with our drawable FBO

    glGenRenderbuffers(1, &_depthRenderbuffer);

    glBindRenderbuffer(GL_RENDERBUFFER, _depthRenderbuffer);

    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, backingWidth, backingHeight);

    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, _depthRenderbuffer);

    if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)

    {

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

        return nil;

    }

    self = [super initWithDefaultFBO:defaultFBOName];

    if (nil == self)

    {

        glDeleteFramebuffers(1, &defaultFBOName);

        glDeleteRenderbuffers(1, &_colorRenderbuffer);

        glDeleteRenderbuffers(1, &_depthRenderbuffer);

    }

    return self;

}

- (void)render

{

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

    glBindFramebuffer(GL_FRAMEBUFFER, super.defaultFBOName);

    [super render];

    glBindRenderbuffer(GL_RENDERBUFFER, _colorRenderbuffer);

    [_context presentRenderbuffer:GL_RENDERBUFFER];

}

- (BOOL)resizeFromLayer:(CAEAGLLayer*)layer

{

    // The pixel dimensions of the CAEAGLLayer

    GLint backingWidth;

    GLint backingHeight;

    // 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);

    glGenRenderbuffers(1, &_depthRenderbuffer);

    glBindRenderbuffer(GL_RENDERBUFFER, _depthRenderbuffer);

    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, backingWidth, backingHeight);

    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, _depthRenderbuffer);

    [super resizeWithWidth:backingWidth AndHeight: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 (super.defaultFBOName)

    {

        GLuint defaultFBOName = super.defaultFBOName;

        glDeleteFramebuffers(1, &defaultFBOName);

        super.defaultFBOName = 0;

    }

    if (_colorRenderbuffer)

    {

        glDeleteRenderbuffers(1, &_colorRenderbuffer);

        _colorRenderbuffer = 0;

    }

}

@end