/**
 * Copyright (c) 2021 Dominic Msters
 * 
 * This software is released under the MIT License.
 * https://opensource.org/licenses/MIT
 */

#pragma once
#include "../../libs.h"
#include "../matrix.h"
#include "../camera.h"
#include "../texture.h"
#include "../../util/array.h"

#define SHADER_UNIFORM_NAME_MAX 24
#define SHADER_UNIFORM_COUNT 16

/** Representation of a shader uniform */
typedef GLuint shaderuniform_t;

/**
 * Structure containing information about an OpenGL Shader. For simplicity sake
 * we demand certain uninforms to be present on the shader target.
 */
typedef struct {
  /** Pointer to an uploaded vertex shader program */
  shaderuniform_t shaderVertex;

  /** Pointer to an uploaded fragment shader program */
  GLuint shaderFrag;

  /** Pointer to an uploaded shader program linked */
  GLuint shaderProgram;

  /** Buffer of chars where we store the uniform names */
  char uniformBuffer[SHADER_UNIFORM_NAME_MAX * SHADER_UNIFORM_COUNT];

  /** Array of strings (pointers to the above buffer) of the uniform names */
  char *uniformNames[SHADER_UNIFORM_COUNT];
  int32_t uniformCount;

  /** Type of each uniform */
  GLenum types[SHADER_UNIFORM_COUNT];

  /** Texture Slots (which texture slot for GL to use for each uniform) */
  uint8_t textureSlots[SHADER_UNIFORM_COUNT];
} shader_t;

/**
 * Compiles a shader from vertex and fragment shader code.
 * @param shader Shader to compile into.
 * @param vertexShaderSource The raw vertex shader code.
 * @param fragmentShaderSource The raw fragment shader code.
 */
void shaderInit(shader_t *shader,
  char *vertexShaderSource, char* fragmentShaderSource
);

/**
 * Return the shaderuniform_t for a given shader uniform name.
 * 
 * @param shader Shader to get from
 * @param name Name to look for
 * @return The shader uniform, or -1 if not found.
 */
shaderuniform_t shaderGetUniform(shader_t *shader, char *name);

/**
 * Cleanup and unload a previously loaded shader.
 * @param shader The shader to unload
 */
void shaderDispose(shader_t *shader);

/**
 * Attaches the supplied shader as the current shader.
 * @param shader The shader to attach
 */
void shaderUse(shader_t *shader);



/**
 * Attaches a texture to the shader.
 * 
 * @param shader Shader to attach to.
 * @param uniform Uniform on the shader to set.
 * @param texture Texture to attach.
 */
void shaderUseTexture(
  shader_t *shader, shaderuniform_t uniform, texture_t *texture
);

/**
 * Set's a specific shader uniform to a matrix.
 * 
 * @param shader Shader to apply to.
 * @param uniform Uniform on the shader to set.
 * @param matrix Matrix to apply.
 */
void shaderUseMatrix(
  shader_t *shader, shaderuniform_t uniform, matrix_t *matrix
);

/**
 * Set's a specific shader uniform to a color.
 * 
 * @param shader Shader to apply to.
 * @param uniform Uniform on the shader to set.
 * @param color Color to set on to the uniform.
 */
void shaderUseColor(shader_t *shader, shaderuniform_t uniform, pixel_t color);

/**
 * Set's the current translation matrix onto the shader for the next
 * render to use. Rotation order is set to YZX.
 * 
 * @param shader Shader to attach to.
 * @param uniform Uniform on the shader to set.
 * @param x X coordinate (world space).
 * @param y Y coordinate (world space).
 * @param z Z coordinate (world space).
 * @param pitch Pitch of the object (local space).
 * @param yaw Yaw of the object (local space).
 * @param roll Roll of the object (local space).
 */
void shaderUsePosition(
  shader_t *shader, shaderuniform_t uniform,
  float x, float y, float z,
  float pitch, float yaw, float roll
);

/**
 * Set's the current translation matrix onto the shader for the next
 * render to use. Also provides scaling controls.
 * 
 * @param shader Shader to attach to.
 * @param uniform Uniform on the shader to set.
 * @param x X coordinate (world space).
 * @param y Y coordinate (world space).
 * @param z Z coordinate (world space).
 * @param pitch Pitch of the object (local space).
 * @param yaw Yaw of the object (local space).
 * @param roll Roll of the object (local space).
 * @param scaleX X scale of model (1 being 100% scaled).
 * @param scaleY Y scale of model (1 being 100% scaled).
 * @param scaleZ Z scale of model (1 being 100% scaled).
 */
void shaderUsePositionAndScale(
  shader_t *shader, shaderuniform_t uniform,
  float x, float y, float z,
  float pitch, float yaw, float roll,
  float scaleX, float scaleY, float scaleZ
);

/**
 * Attaches a camera to the shader.
 * 
 * @param shader Shader to attach to.
 * @param uniformView Shader Uniform for the view matrix.
 * @param uniformProjection Shader Uniform for the view matrix.
 * @param camera Camera to attach.
 */
void shaderUseCamera(
  shader_t *shader,
  shaderuniform_t uniformView, shaderuniform_t uniformProjection,
  camera_t *camera
);