/* SPDX-License-Identifier: ISC */
/*
 * shader.c
 *
 * Copyright (C) 2022 David Oberhollenzer <goliath@infraroot.at>
 */
#include "shadermeh.h"

/* stub vertex shader */
static const char *vert_src =
"#version 140\n"
"\n"
"in vec4 V_POSITION;\n"
"in vec4 V_COLOR;\n"
"\n"
"void main()\n"
"{\n"
"	gl_Position = V_POSITION;\n"
"}\n";

/* stub fragment shader */
static const char *frag_src_pre =
"#version 330\n"
"\n"
"uniform vec3 iResolution;\n"
"uniform float iTime;\n"
"uniform float iTimeDelta;\n"
"uniform float iFrame;\n"
"uniform float iChannelTime[4];\n"
"uniform vec4 iMouse;\n"
"uniform vec4 iDate;\n"
"uniform float iSampleRate;\n"
"uniform vec3 iChannelResolution[4];\n"
"uniform sampler2D iChannel0;"
"\n";

static const char *frag_src_post =
"\n"
"void main()\n"
"{\n"
"	mainImage(gl_FragColor, gl_FragCoord.xy);\n"
"}\n"
"\n";

static char* load_file(const char *path)
{
	size_t size, pre_len, post_len;
	char *buffer;
	FILE *f;

	if (!path)
		return NULL;

	/* try to open the file */
	f = fopen(path, "r");
	if (!f) {
		perror(path);
		return NULL;
	}

	/* get file size */
	fseek(f, 0, SEEK_END);
	size = ftell(f);
	fseek(f, 0, SEEK_SET);

	pre_len = strlen(frag_src_pre);
	post_len = strlen(frag_src_post);

	/* try to allocate buffer for file contents */
	buffer = calloc(1, pre_len + size + post_len + 1);

	if (!buffer) {
		fclose(f);
		return NULL;
	}

	/* read file contents into buffer */
	memcpy(buffer, frag_src_pre, pre_len);
	fread(buffer + pre_len, 1, size, f);
	memcpy(buffer + pre_len + size, frag_src_post, post_len);

	/* cleanup */
	fclose(f);
	return buffer;
}

/****************************************************************************/

GLuint shader_program_load(const char *fsrc)
{
	GLuint vsh = 0, fsh = 0, prog = 0;
	char *fs = NULL;

	if (!fsrc)
		return 0;

	fs = load_file(fsrc);

	if (!fs)
		goto done;

	vsh = glCreateShader(GL_VERTEX_SHADER);
	fsh = glCreateShader(GL_FRAGMENT_SHADER);

	if (!vsh || !fsh)
		goto done;

	prog = glCreateProgram();
	if (!prog)
		goto done;

	glShaderSource(vsh, 1, (const GLchar **)&vert_src, NULL);
	glShaderSource(fsh, 1, (const GLchar **)&fs, NULL);

	glCompileShader(vsh);
	glCompileShader(fsh);

	glAttachShader(prog, vsh);
	glAttachShader(prog, fsh);

	glLinkProgram(prog);
done:
	if (vsh)
		glDeleteShader(vsh);
	if (fsh)
		glDeleteShader(fsh);
	free(fs);
	return prog;
}

int shader_program_get_build_status(GLuint prog)
{
	GLuint shaders[3];
	GLsizei i, count;
	GLint v;

	glGetProgramiv(prog, GL_LINK_STATUS, &v);
	if (!v)
		return 0;

	glGetAttachedShaders(prog, 3, &count, shaders);

	for (i = 0; i < count; ++i) {
		glGetShaderiv(shaders[i], GL_COMPILE_STATUS, &v);
		if (!v)
			return 0;
	}

	return 1;
}

void shader_program_print_info_log(GLuint prog)
{
	GLsizei i, count, len;
	char *buffer = NULL;
	int buffersize = 0;
	GLuint shaders[3];
	GLint v;

	glGetAttachedShaders(prog, 3, &count, shaders);

	for (i = 0; i < count; ++i) {
		glGetShaderiv(shaders[i], GL_INFO_LOG_LENGTH, &v);

		if ((v + 1) > buffersize) {
			buffer = realloc(buffer, v + 1);
			buffersize = v + 1;
		}

		glGetShaderInfoLog(shaders[i], buffersize,
				   &len, (GLchar *)buffer);
		buffer[len] = '\0';
		printf("-------------\n%s\n-------------\n", buffer);
	}

	glGetProgramiv(prog, GL_INFO_LOG_LENGTH, &v);

	if ((v + 1) > buffersize) {
		buffer = realloc(buffer, v + 1);
		buffersize = v + 1;
	}

	glGetProgramInfoLog(prog, buffersize, &len, (GLchar *)buffer);
	buffer[len] = '\0';
	printf("-------------\n%s\n-------------\n", buffer);

	free(buffer);
}