/*

 File: Shaders.m

 Abstract: Shader utilities for compiling, linking and validating shaders. 

 It is important to check the result status.

 Version: 1.0

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 please do not use, install, modify or redistribute this Apple software.

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 Neither the name, trademarks, service marks or logos of Apple Inc. may be used

 to endorse or promote products derived from the Apple Software without specific

 prior written permission from Apple.  Except as expressly stated in this notice,

 no other rights or licenses, express or implied, are granted by Apple herein,

 including but not limited to any patent rights that may be infringed by your

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 The Apple Software is provided by Apple on an "AS IS" basis.  APPLE MAKES NO

 WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION THE IMPLIED

 WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS FOR A PARTICULAR

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 COMBINATION WITH YOUR PRODUCTS.

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 Copyright (C) 2009 Apple Inc. All Rights Reserved.

*/

#import "Shaders.h"

/* Create and compile a shader from the provided source(s) */

GLint compileShader(GLuint *shader, GLenum type, GLsizei count, NSString *file)

{

    GLint status;

    const GLchar *sources;

    // get source code

    sources = (GLchar *)[[NSString stringWithContentsOfFile:file encoding:NSUTF8StringEncoding error:nil] UTF8String];

    if (!sources)

    {

        NSLog(@"Failed to load vertex shader");

        return 0;

    }

    *shader = glCreateShader(type);             // create shader

    glShaderSource(*shader, 1, &sources, NULL); // set source code in the shader

    glCompileShader(*shader);                   // compile shader

#if defined(DEBUG)

    GLint logLength;

    glGetShaderiv(*shader, GL_INFO_LOG_LENGTH, &logLength);

    if (logLength > 0)

    {

        GLchar *log = (GLchar *)malloc(logLength);

        glGetShaderInfoLog(*shader, logLength, &logLength, log);

        NSLog(@"Shader compile log:\n%s", log);

        free(log);

    }

#endif

    glGetShaderiv(*shader, GL_COMPILE_STATUS, &status);

    if (status == GL_FALSE)

    {

        NSLog(@"Failed to compile shader:\n");

        int i;

        for (i = 0; i < count; i++)

            NSLog(@"%s", sources[i]);

    }

    return status;

}

/* Link a program with all currently attached shaders */

GLint linkProgram(GLuint prog)

{

    GLint status;

    glLinkProgram(prog);

#if defined(DEBUG)

    GLint logLength;

    glGetProgramiv(prog, GL_INFO_LOG_LENGTH, &logLength);

    if (logLength > 0)

    {

        GLchar *log = (GLchar *)malloc(logLength);

        glGetProgramInfoLog(prog, logLength, &logLength, log);

        NSLog(@"Program link log:\n%s", log);

        free(log);

    }

#endif

    glGetProgramiv(prog, GL_LINK_STATUS, &status);

    if (status == GL_FALSE)

        NSLog(@"Failed to link program %d", prog);

    return status;

}

/* Validate a program (for i.e. inconsistent samplers) */

GLint validateProgram(GLuint prog)

{

    GLint logLength, status;

    glValidateProgram(prog);

    glGetProgramiv(prog, GL_INFO_LOG_LENGTH, &logLength);

    if (logLength > 0)

    {

        GLchar *log = (GLchar *)malloc(logLength);

        glGetProgramInfoLog(prog, logLength, &logLength, log);

        NSLog(@"Program validate log:\n%s", log);

        free(log);

    }

    glGetProgramiv(prog, GL_VALIDATE_STATUS, &status);

    if (status == GL_FALSE)

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

    return status;

}

/* delete shader resources */

void destroyShaders(GLuint vertShader, GLuint fragShader, GLuint prog)

{   

    if (vertShader) {

        glDeleteShader(vertShader);

        vertShader = 0;

    }

    if (fragShader) {

        glDeleteShader(fragShader);

        fragShader = 0;

    }

    if (prog) {

        glDeleteProgram(prog);

        prog = 0;

    }

}