#include "Angel.h"
#include <iostream>
#include <unistd.h>

namespace Angel {


// Create a NULL-terminated string by reading the provided file
static char*
readShaderSource(const char* shaderFile)
{
    FILE* fp = fopen(shaderFile, "r");

    if ( fp == NULL ) { return NULL; }

    fseek(fp, 0L, SEEK_END);
    long size = ftell(fp);

    fseek(fp, 0L, SEEK_SET);
    char* buf = new char[size + 1];
    fread(buf, 1, size, fp);

    buf[size] = '\0';
    fclose(fp);

    return buf;
}


// Create a GLSL program object from vertex and fragment shader files
GLuint
InitShader(const char* vShaderFile, const char* fShaderFile)
{
    struct Shader {
	const char*  filename;
	GLenum       type;
	GLchar*      source;
    }  shaders[2] = {
	{ vShaderFile, GL_VERTEX_SHADER, NULL },
	{ fShaderFile, GL_FRAGMENT_SHADER, NULL }
    };

    GLuint program = glCreateProgram();
    
    for ( int i = 0; i < 2; ++i ) {
        Shader& s = shaders[i];
        s.source = readShaderSource( s.filename );
        if ( shaders[i].source == NULL ) {
             std::cerr << "Failed to read " << s.filename << std::endl;
            exit( EXIT_FAILURE );
        }

        GLuint shader = glCreateShader( s.type );
        glShaderSource( shader, 1, (const GLchar**) &s.source, NULL );
        glCompileShader( shader );

        GLint  compiled;
        glGetShaderiv( shader, GL_COMPILE_STATUS, &compiled );
        if ( !compiled ) {
             std::cerr << s.filename << " failed to compile:" << std::endl;
            GLint  logSize;
            glGetShaderiv( shader, GL_INFO_LOG_LENGTH, &logSize );
            char* logMsg = new char[logSize];
            glGetShaderInfoLog( shader, logSize, NULL, logMsg );
             std::cerr << logMsg << std::endl;
            delete [] logMsg;

            exit( EXIT_FAILURE );
        }

        delete [] s.source;

        glAttachShader( program, shader );
    }

    /* link  and error check */
    glLinkProgram(program);

    GLint  linked;
    glGetProgramiv( program, GL_LINK_STATUS, &linked );
    if ( !linked ) {
	 std::cerr << "Shader program failed to link" << std::endl;
	GLint  logSize;
	glGetProgramiv( program, GL_INFO_LOG_LENGTH, &logSize);
	char* logMsg = new char[logSize];
	glGetProgramInfoLog( program, logSize, NULL, logMsg );
	 std::cerr << logMsg << std::endl;
	delete [] logMsg;

	exit( EXIT_FAILURE );
    }

    /* use program object */
    glUseProgram(program);

    return program;
}
    
// Create a GLSL program object from vertex and fragment shaders presented as literal source code
GLuint
InitLitShader(const GLchar* vShaderSource, const GLchar* fShaderSource)
{
    struct Shader {
        const char*  filename;
        GLenum       type;
        const GLchar*      source;
    }  shaders[2] = {
        { NULL, GL_VERTEX_SHADER, vShaderSource },
        { NULL, GL_FRAGMENT_SHADER, fShaderSource }
    };
    
    GLuint program = glCreateProgram();
    
    for ( int i = 0; i < 2; ++i ) {
        Shader& s = shaders[i];
        // s.source = readShaderSource( s.filename );
        /* if ( shaders[i].source == NULL ) {
            std::cerr << "Failed to read " << s.filename << std::endl;
            exit( EXIT_FAILURE );
        } */
        
        GLuint shader = glCreateShader( s.type );
        glShaderSource( shader, 1, (const GLchar**) &s.source, NULL );
        glCompileShader( shader );
        
        GLint  compiled;
        glGetShaderiv( shader, GL_COMPILE_STATUS, &compiled );
        if ( !compiled ) {
            std::cerr << s.filename << " failed to compile:" << std::endl;
            GLint  logSize;
            glGetShaderiv( shader, GL_INFO_LOG_LENGTH, &logSize );
            char* logMsg = new char[logSize];
            glGetShaderInfoLog( shader, logSize, NULL, logMsg );
            std::cerr << logMsg << std::endl;
            delete [] logMsg;
            
            exit( EXIT_FAILURE );
        }
        
        delete [] s.source;
        
        glAttachShader( program, shader );
    }
    
    /* link  and error check */
    glLinkProgram(program);
    
    GLint  linked;
    glGetProgramiv( program, GL_LINK_STATUS, &linked );
    if ( !linked ) {
        std::cerr << "Shader program failed to link" << std::endl;
        GLint  logSize;
        glGetProgramiv( program, GL_INFO_LOG_LENGTH, &logSize);
        char* logMsg = new char[logSize];
        glGetProgramInfoLog( program, logSize, NULL, logMsg );
        std::cerr << logMsg << std::endl;
        delete [] logMsg;
        
        exit( EXIT_FAILURE );
    }
    
    /* use program object */
    glUseProgram(program);
    
    return program;
}


}  // Close namespace Angel block