#include "mk.h"
#include <stdio.h>
#include <stdlib.h>

static GLFWwindow *Window;
static Shader_t Shader;
static GLuint Vao, Vbo;
static Vertex_t Vertices[3];

static const GLchar WORLD_SHADER_VS[] = {
    "#version 330\n"

    // per vertex:
    "in vec3 vPosition;"

    "void main() {"
    "  gl_Position = vec4(vPosition + vOffset, 1.0f);"
    "}"
};

static const GLchar WORLD_SHADER_FS[] = {
    "#version 330\n"

    "out vec3 oColor;"

    "void main() {"
    "  oColor = vec3(1.0f, 1.0f, 1.0f);"
    "}"
};

static GLuint CompileShader(const GLchar *source, GLenum type)
{
    GLuint shader = glCreateShader(type);
    if (!shader) return 0;

    glShaderSource(shader, 1, &source, NULL);
    glCompileShader(shader);

    GLint success;
    glGetShaderiv(shader, GL_COMPILE_STATUS, &success);
    if (!success) {
        GLchar log[1024];
        glGetShaderInfoLog(shader, sizeof(log), NULL, log);
        fprintf(stderr, "[ERROR] CompileShader:\n%s\n", log);

        glDeleteShader(shader);
        return 0;
    }
    return shader;
}

void InitializeWindow(GLFWwindow *w)
{
    Window = w;
}

bool InitializeShaders()
{
    Shader.VS = CompileShader(WORLD_SHADER_VS, GL_VERTEX_SHADER);
    if (!Shader.VS) return false;

    Shader.FS = CompileShader(WORLD_SHADER_FS, GL_FRAGMENT_SHADER);
    if (!Shader.FS) return false;

    Shader.Program = glCreateProgram();
    if (!Shader.Program) return false;

    glAttachShader(Shader.Program, Shader.VS);
    glAttachShader(Shader.Program, Shader.FS);
    glLinkProgram(Shader.Program);
    glDetachShader(Shader.Program, Shader.VS);
    glDetachShader(Shader.Program, Shader.FS);

    GLint success;
    glGetProgramiv(Shader.Program, GL_LINK_STATUS, &success);
    if (!success) {
        GLchar log[1024];
        glGetProgramInfoLog(Shader.Program, sizeof(log), NULL, log);
        fprintf(stderr, "[ERROR] InitializeShaders:\n%s\n", log);
        return false;
    }
    return true;
}

bool InitializeMeshes()
{
    Vertices[0].Position.x = -0.5f;
    Vertices[0].Position.y = -0.5f;
    Vertices[0].Position.z = 0.0f;

    Vertices[1].Position.x = 0.0f;
    Vertices[1].Position.y = 0.5f;
    Vertices[1].Position.z = 0.0f;

    Vertices[1].Position.x = 0.5f;
    Vertices[1].Position.y = -0.5f;
    Vertices[1].Position.z = 0.0f;

    glGenBuffers(1, &Vao);
    glBindVertexArray(Vao);

    glGenBuffers(1, &Vbo);
    glBindBuffer(GL_ARRAY_BUFFER, Vbo);

    glBufferData(Vbo, sizeof(Vertices), Vertices, GL_STATIC_DRAW);

    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);

    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindVertexArray(0);
    return true;
}

void RenderMeshes()
{
    glUseProgram(Shader.Program);

    glBindVertexArray(Vao);
    glBindBuffer(GL_ARRAY_BUFFER, Vbo);

    glDrawArrays(GL_TRIANGLES, 0, 3);

    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindVertexArray(0);
}