module Engine.Shader;

import std.stdio;
import derelict.opengl3.gl;
import Engine.Batch;
import gl3n.linalg;


class Shader
{
	immutable GLuint Program;
	package static GLuint currentProgram = -1;
	Attribute[string] attributes;

	@property const(Attribute[string]) Attributes() {
		return attributes;
	}

	this(immutable string vertexShaderSource,immutable string fregmentShaderSource)
	{
		auto vertexShader = glCreateShader(GL_VERTEX_SHADER); 

		auto vertexSourcePtr = cast(const char*)vertexShaderSource.ptr;
		glShaderSource(vertexShader, 1, &vertexSourcePtr , null);
		glCompileShader(vertexShader);

		int result = 0;
		glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &result);
		if (result != GL_TRUE) {
			int InfoLogLength = 0;
			glGetShaderiv(vertexShader, GL_INFO_LOG_LENGTH, &InfoLogLength);
			if ( InfoLogLength > 0 ){
				char[] message = new char[InfoLogLength];
				scope( exit )  destroy(message); 
				glGetShaderInfoLog(vertexShader, InfoLogLength, null, cast( char*)&message[0]);
				throw new Exception(cast(string)message);
			}
		}

		auto fregmentShader = glCreateShader(GL_FRAGMENT_SHADER); 

		auto fregmentShaderPtr = cast(const char*)fregmentShaderSource.ptr;
		glShaderSource(fregmentShader, 1, &fregmentShaderPtr , null);
		glCompileShader(fregmentShader);

		result = 0;
		glGetShaderiv(fregmentShader, GL_COMPILE_STATUS, &result);
		if (result != GL_TRUE) {
			int InfoLogLength = 0;
			glGetShaderiv(fregmentShader, GL_INFO_LOG_LENGTH, &InfoLogLength);
			if ( InfoLogLength > 0 ){
				char[] message = new char[InfoLogLength];
				scope( exit )  destroy(message) ;
				glGetShaderInfoLog(fregmentShader, InfoLogLength, null, cast( char*)&message[0]);
				throw new Exception(cast(string)message);
			}
		}

		auto program = glCreateProgram();
		glAttachShader(program, vertexShader);
		glAttachShader(program, fregmentShader);
		glLinkProgram(program);

		result = 0;
		glGetProgramiv(program, GL_LINK_STATUS, &result);
		if (result != GL_TRUE) {
			int InfoLogLength = 0;
			glGetProgramiv(program, GL_INFO_LOG_LENGTH, &InfoLogLength);
			if ( InfoLogLength > 0 ){
				char[] message = new char[InfoLogLength];
				scope( exit )  destroy(message) ; 
				glGetProgramInfoLog(program, InfoLogLength, null, cast( char*)&message[0]);
				throw new Exception(cast(string)message);
			}
		}

		int attribs = 0;
		glGetProgramiv(program, GL_ACTIVE_ATTRIBUTES, &attribs);
		int maxAttribLen = 0;
		glGetProgramiv(program, GL_ACTIVE_ATTRIBUTE_MAX_LENGTH, &maxAttribLen);


		for (int i =0;i<attribs;i++) {
			int len = 0;
			int attribSize = 0;
			GLenum type = 0;
			char[] message = new char[maxAttribLen];
			glGetActiveAttrib(program,i,maxAttribLen,&len,&attribSize,&type,cast( char*)&message[0]);
			message = message[0..len];
			auto location = glGetAttribLocation(program, cast( char*)&message[0]);
			this.attributes[cast(string)(message)] = new Attribute(i,location,cast(string)(message),type);
		}

		attribs = 0;
		glGetProgramiv(program, GL_ACTIVE_UNIFORMS, &attribs);
		maxAttribLen = 0;
		glGetProgramiv(program, GL_ACTIVE_UNIFORM_MAX_LENGTH, &maxAttribLen);

		for (int i =0;i<attribs;i++) {
			int len = 0;
			int attribSize = 0;
			GLenum type = 0;
			char[] message = new char[maxAttribLen];
			glGetActiveUniform(program,i,maxAttribLen,&len,&attribSize,&type,cast( char*)&message[0]);
			message = message[0..len];
			auto location = glGetUniformLocation(program, cast( char*)&message[0]);
			this.attributes[cast(string)(message)] = new Attribute(i,location,cast(string)(message),type);
		}




		Program = program;
	}

	public void Use() {
		if (Program != currentProgram) {
			currentProgram = Program;
			glUseProgram(Program);
		}
	}
}



class Attribute {
	package this(int index, uint location, string name, GLenum type) {
		this.index = index;
		this.location = location;
		this.name = name;
		this.type = type;
	}

	immutable int index;
	immutable uint location;
	immutable string name;
	immutable GLenum type;

	final void Set(vec4 v) const {
		glUniform4f(location, v.x,v.y,v.z,v.w);
	}

	final void Set(vec3 v) const {
		glUniform3f(location, v.x,v.y,v.z);
	}

	final void Set(vec2 v) const {
		glUniform2f(location, v.x,v.y);
	}

	final void Set(float v) const {
		glUniform1f(location, v);
	}

	final void Set(vec4d v) const {
		glUniform4d(location, v.x,v.y,v.z,v.w);
	}

	final void Set(vec3d v) const {
		glUniform3d(location, v.x,v.y,v.z);
	}

	final void Set(vec2d v) const {
		glUniform2d(location, v.x,v.y);
	}

	final void Set(double v) const {
		glUniform1d(location, v);
	}

	final void Set(vec4i v) const {
		glUniform4i(location, v.x,v.y,v.z,v.w);
	}

	final void Set(vec3i v) const {
		glUniform3i(location, v.x,v.y,v.z);
	}

	final void Set(vec2i v) const {
		glUniform2i(location, v.x,v.y);
	}

	final void Set(int v) const {
		glUniform1i(location, v);
	}

	final void Set(bool v) const {
		glUniform1i(location, cast(bool)v);
	}

	final void Set(ref mat4 m) const {
		glUniformMatrix4fv(location, 1, GL_TRUE, m.value_ptr);
	}

	final void Set(mat4 m) const {
		glUniformMatrix4fv(location, 1, GL_TRUE, m.value_ptr);
	}
}