/*
 * demoscene-eo, an ASCII art demoscene written as a gift for Emmanuel Otton retirement 
 * Copyright (C) 2019  XXXXXX XXXXXXX <xxxxxx@xxxxxx.fr>
 *  
 * This file is part of demoscene-eo.
 *
 *  demoscene-eo is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  demoscene-eo is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with demoscene-eo.  If not, see <http://www.gnu.org/licenses/>
 */
#include "scene01.h"

// Mostly inspired by CC0 https://gist.github.com/koute/7391344
typedef float t_mat4x4[16];

static inline void mat4x4_ortho( t_mat4x4 out, float left, float right, float bottom, float top, float znear, float zfar )
{
	#define T(a, b) (a * 4 + b)

	out[T(0,0)] = 2.0f / (right - left);
	out[T(0,1)] = 0.0f;
	out[T(0,2)] = 0.0f;
	out[T(0,3)] = 0.0f;

	out[T(1,1)] = 2.0f / (top - bottom);
	out[T(1,0)] = 0.0f;
	out[T(1,2)] = 0.0f;
	out[T(1,3)] = 0.0f;

	out[T(2,2)] = -2.0f / (zfar - znear);
	out[T(2,0)] = 0.0f;
	out[T(2,1)] = 0.0f;
	out[T(2,3)] = 0.0f;

	out[T(3,0)] = -(right + left) / (right - left);
	out[T(3,1)] = -(top + bottom) / (top - bottom);
	out[T(3,2)] = -(zfar + znear) / (zfar - znear);
	out[T(3,3)] = 1.0f;

	#undef T
}

static const char * vertex_shader =
	"#version 130\n"
	"in vec2 i_position;\n"
	"in vec4 i_color;\n"
	"out vec4 v_color;\n"
	"uniform mat4 u_projection_matrix;\n"
	"void main() {\n"
	"	v_color = i_color;\n"
	"	gl_Position = u_projection_matrix * vec4( i_position, 0.0, 1.0 );\n"
	"}\n";

static const char * fragment_shader =
	"#version 130\n"
	"in vec4 v_color;\n"
	"out vec4 o_color;\n"
	"void main() {\n"
	"	o_color = v_color;\n"
	"}\n";

typedef enum t_attrib_id
{
	attrib_position,
	attrib_color
} t_attrib_id;

int scene01_init_gl(graphical_env_t *ge, scene01_env_t *se) {
	GLuint vs, fs, program;

	vs = glCreateShader( GL_VERTEX_SHADER );
	fs = glCreateShader( GL_FRAGMENT_SHADER );

	int length = strlen( vertex_shader );
	glShaderSource( vs, 1, ( const GLchar ** )&vertex_shader, &length );
	glCompileShader( vs );

	GLint status;
	glGetShaderiv( vs, GL_COMPILE_STATUS, &status );
	if( status == GL_FALSE )
	{
		fprintf( stderr, "vertex shader compilation failed\n" );
		return 1;
	}

	length = strlen( fragment_shader );
	glShaderSource( fs, 1, ( const GLchar ** )&fragment_shader, &length );
	glCompileShader( fs );

	glGetShaderiv( fs, GL_COMPILE_STATUS, &status );
	if( status == GL_FALSE )
	{
		fprintf( stderr, "fragment shader compilation failed\n" );
		return 1;
	}

	program = glCreateProgram();
	glAttachShader( program, vs );
	glAttachShader( program, fs );

	glBindAttribLocation( program, attrib_position, "i_position" );
	glBindAttribLocation( program, attrib_color, "i_color" );
	glLinkProgram( program );

	glUseProgram( program );

	glDisable( GL_DEPTH_TEST );
	//glClearColor( 0.5, 0.0, 0.0, 0.0 );
	glClearColor( 0.5, 0.5, 0.0, 0.0 );
	glViewport( 0, 0, FBUF_W, FBUF_H );

	GLuint vbo;

	glGenVertexArrays( 1, &(se->vao) );
	glGenBuffers( 1, &vbo );
	glBindVertexArray( se->vao );
	glBindBuffer( GL_ARRAY_BUFFER, vbo );

	glEnableVertexAttribArray( attrib_position );
	glEnableVertexAttribArray( attrib_color );

	glVertexAttribPointer( attrib_color, 4, GL_FLOAT, GL_FALSE, sizeof( float ) * 6, 0 );
	glVertexAttribPointer( attrib_position, 2, GL_FLOAT, GL_FALSE, sizeof( float ) * 6, ( void * )(4 * sizeof(float)) );

	const GLfloat g_vertex_buffer_data[] = {
	/*  R, G, B, A, X, Y  */
		1, 0, 0, 1, 0, 0,
		0, 1, 0, 1, FBUF_W, 0,
		0, 0, 1, 1, FBUF_W, FBUF_H,

		1, 0, 0, 1, 0, 0,
		0, 0, 1, 1, FBUF_W, FBUF_H,
		1, 1, 1, 1, 0, FBUF_H
	};

	glBufferData( GL_ARRAY_BUFFER, sizeof( g_vertex_buffer_data ), g_vertex_buffer_data, GL_STATIC_DRAW );

	t_mat4x4 projection_matrix;
	mat4x4_ortho( projection_matrix, 0.0f, (float)FBUF_W, (float)FBUF_H, 0.0f, 0.0f, 100.0f );
	glUniformMatrix4fv( glGetUniformLocation( program, "u_projection_matrix" ), 1, GL_FALSE, projection_matrix );
	return 0;
}

int scene01_init_sdl(graphical_env_t *ge, scene01_env_t *se) {
	return 0;
}

int scene01_init_caca(graphical_env_t *ge, scene01_env_t *se) {
	return 0;
}

void scene01_free_gl(graphical_env_t *ge, scene01_env_t *se) {
	//TODO
}

void scene01_free_sdl(graphical_env_t *ge, scene01_env_t *se) {
}

void scene01_free_caca(graphical_env_t *ge, scene01_env_t *se) {
}

int scene01_next_gl(graphical_env_t *ge, scene01_env_t *se) {
	SDL_Renderer *r = ge->gl_rndr;

	// https://gist.github.com/Twinklebear/8265888
	// https://forums.libsdl.org/viewtopic.php?p=51634

	glClear(GL_COLOR_BUFFER_BIT);
	glBindVertexArray(se->vao);
	glDrawArrays(GL_TRIANGLES, 0, 6);
	// [...]

	SDL_GL_SwapWindow(ge->gl_win);
	
	// Download the rendered texture from videocard to main memory
	SDL_RenderReadPixels(r, NULL, 0, ge->raw_target, FBUF_W*4);

	return 0;
}

int scene01_next_sdl(graphical_env_t *ge, scene01_env_t *se) {
	return 0;
}

int scene01_next_caca(graphical_env_t *ge, scene01_env_t *se) {
	// Shorthands
	caca_canvas_t *cv = ge->cv;
	int w = ge->w, h = ge->h;
	Uint32 frame = ge->sc_framecount;

	// "convert" the raw pixel stream from SDL to ASCII art on caca canevas
	caca_set_dither_gamma(ge->d, 1.0);
	caca_dither_bitmap(cv, 0, 0, w, h, ge->d, ge->raw_target);

	// Add things on top of caca canvas
	caca_set_color_ansi(cv, CACA_WHITE, CACA_BLACK);
	caca_put_str(cv, (w-17)/2, h/2, "This is a message");

	if ( frame >= 300 ) {
		return 1;
	}
	return 0;
}