import ctypes
import pyglet.gl as gl

class Shader_error(Exception):
	def __init__(self, message):
		self.message = message

def create_shader(target, source_path):
	# read shader source

	source_file = open(source_path, "rb")
	source = source_file.read()
	source_file.close()

	source_length = ctypes.c_int(len(source) + 1)
	source_buffer = ctypes.create_string_buffer(source)

	buffer_pointer = ctypes.cast(
		ctypes.pointer(ctypes.pointer(source_buffer)),
		ctypes.POINTER(ctypes.POINTER(ctypes.c_char)))
	
	# compile shader

	gl.glShaderSource(target, 1, buffer_pointer, ctypes.byref(source_length))
	gl.glCompileShader(target)

	# handle potential errors

	log_length = gl.GLint(0)
	gl.glGetShaderiv(target, gl.GL_INFO_LOG_LENGTH, ctypes.byref(log_length))

	log_buffer = ctypes.create_string_buffer(log_length.value)
	gl.glGetShaderInfoLog(target, log_length, None, log_buffer)

	if log_length.value > 1:
		raise Shader_error(str(log_buffer.value))

class Shader:
	def __init__(self, vert_path, frag_path):
		self.program = gl.glCreateProgram()

		# create vertex shader

		self.vert_shader = gl.glCreateShader(gl.GL_VERTEX_SHADER)
		create_shader(self.vert_shader, vert_path)
		gl.glAttachShader(self.program, self.vert_shader)

		# create fragment shader

		self.frag_shader = gl.glCreateShader(gl.GL_FRAGMENT_SHADER)
		create_shader(self.frag_shader, frag_path)
		gl.glAttachShader(self.program, self.frag_shader)

		# link program and clean up

		gl.glLinkProgram(self.program)

		gl.glDeleteShader(self.vert_shader)
		gl.glDeleteShader(self.frag_shader)
	
	def __del__(self):
		gl.glDeleteProgram(self.program)

	def find_uniform(self, name):
		return gl.glGetUniformLocation(self.program, ctypes.create_string_buffer(name))
	
	def uniform_matrix(self, location, matrix):
		gl.glUniformMatrix4fv(location, 1, gl.GL_FALSE, (gl.GLfloat * 16) (*sum(matrix.data, [])))

	def use(self):
		gl.glUseProgram(self.program)