#include "shader.hpp"
#include "common.hpp"
#include "vendor/glad/glad.h"
#include <cstdio>
#include <cstring>
#include <cerrno>
#include <cstdlib>


unsigned int create_shader(unsigned int type, const char **source)
{
    unsigned int shader = glCreateShader(type);
    if (!shader) {
        printf("err: create_shader: glCreateShader returned 0\n");
        return 0;
    }
    glShaderSource(shader, 1, source, NULL);
    glCompileShader(shader);

    int success;
    glGetShaderiv(shader, GL_COMPILE_STATUS, &success);
    if (!success) {
        char log[512];
        glGetShaderInfoLog(shader, 512, NULL, log);
        printf("err: create_shader: compilation failed, log: %s\n", log);
        return 0;
    }

    return shader;
}

unsigned int create_program_source(const char *vertex_shader_source, const char *fragment_shader_source)
{
    unsigned int program = glCreateProgram();
    if (!program) {
        printf("err: create_program: glCreateProgram returned 0\n");
        return 0;
    }

    unsigned int vertex_shader = create_shader(GL_VERTEX_SHADER, &vertex_shader_source);
    if (!vertex_shader) {
        printf("err: create_program: create_shader failed returned 0 (vertex_shader)\n");
        return 0;
    }
    unsigned int fragment_shader = create_shader(GL_FRAGMENT_SHADER, &fragment_shader_source);
    if (!fragment_shader) {
        printf("err: create_program: create_shader failed returned 0 (fragment_shader)\n");
        return 0;
    }

    glAttachShader(program, vertex_shader);
    glAttachShader(program, fragment_shader);
    glLinkProgram(program);

    int success;
    glGetProgramiv(program, GL_LINK_STATUS, &success);
    if (!success) {
        char log[512];
        glGetProgramInfoLog(program, 512, NULL, log);
        printf("err: create_program: link failed, log: %s\n", log);
        return 0;
    }

    return program;
}

unsigned int create_program(const char *vertex_shader_path, const char *fragment_shader_path)
{
    FILE *vertex_shader_file, *fragment_shader_file = NULL;
    char *vertex_shader_source = NULL;
    char *fragment_shader_source = NULL;
    Errno err = 0;
    unsigned int ret = 0;

    vertex_shader_file = fopen(vertex_shader_path, "r");
    if (!vertex_shader_file) {
        fprintf(stderr, "create_program: failed to open vertex shader file (%s): %s\n", vertex_shader_path, strerror(errno));
        goto done;
    }
    err = read_entire_file(vertex_shader_file, &vertex_shader_source);
    if (err) {
        fprintf(stderr, "create_program: failed to read vertex shader file (%s): %s\n", vertex_shader_path, strerror(err));
        goto done;
    }

    fragment_shader_file = fopen(fragment_shader_path, "r");
    if (!fragment_shader_file) {
        fprintf(stderr, "create_program: failed to open fragment shader file (%s): %s\n", fragment_shader_path, strerror(errno));
        goto done;
    }
    err = read_entire_file(fragment_shader_file, &fragment_shader_source);
    if (err) {
        fprintf(stderr, "create_program: failed to read fragment shader file (%s): %s\n", fragment_shader_path, strerror(err));
        goto done;
    }

    ret = create_program_source(vertex_shader_source, fragment_shader_source);

done:
    if (vertex_shader_file) fclose(vertex_shader_file);
    if (fragment_shader_file) fclose(fragment_shader_file);
    if (vertex_shader_source) free(vertex_shader_source);
    if (fragment_shader_source) free(fragment_shader_source);
    return ret;
}