/*
    Copyright (C) 2021  hiimgoodpack

    This program 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.

    This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.
*/

#define FAST_OBJ_IMPLEMENTATION
#include "../fast_obj/fast_obj.h"
#include <mesh.h>
#include <GLFW/glfw3.h>
#include <shader.h>
#include <cstring>
#include <cassert>
#include <iostream>

typedef struct {
	linalg::aliases::float3 position;
} Vertex;
typedef unsigned int Element;

const Mesh::Attribute VERTEX_ATTRIBUTES[] = {
	{
		.index = 0,
		.size = 3,
		.type = GL_FLOAT,
		.stride = sizeof(Vertex),
		.pointer = (void*)offsetof(Vertex, position)
	}
};

Mesh::InstancedElements processMesh(const char* const path) {
	fastObjMesh* mesh = fast_obj_read(path);
	assert(mesh && "An error occured while reading a mesh. Make sure the path is correct and points to a wavefront object file");

	const unsigned int vertexCount = mesh->position_count-1;
	const unsigned int indexCount = mesh->face_count*3;
	Vertex* const vertices = new Vertex[vertexCount];
	Element* const elements = new Element[indexCount];

	// Index 0 is an invalid index to use in an object file, so we'll remove it
	for (unsigned int i = 1; i < mesh->position_count; i++) {
		vertices[i-1].position = {mesh->positions[i*3], mesh->positions[i*3+1], mesh->positions[i*3+2]};
	}
	for (unsigned int i = 0; i < mesh->face_count; i += 3) {
		elements[i] = mesh->indices[i].p-1;
		elements[i+1] = mesh->indices[i].t-1;
		elements[i+2] = mesh->indices[i].n-1;
	}

	fast_obj_destroy(mesh);

	// TODO: Make a way to clean up buffers
	Buffer::Specialized<Vertex, GL_ARRAY_BUFFER> vertexBuffer(vertices, vertexCount * sizeof(Vertex), GL_STATIC_DRAW);
	Buffer::Specialized<Element, GL_ELEMENT_ARRAY_BUFFER> elementBuffer(elements, indexCount * sizeof(Element), GL_STATIC_DRAW);

	delete[] vertices;
	delete[] elements;

	Mesh::Buffer buffers[2] = {
		{
			.buffer = vertexBuffer,
			.attributes = VERTEX_ATTRIBUTES,
			.attributeCount = sizeof(VERTEX_ATTRIBUTES)/sizeof(Mesh::Attribute)
		},
		{
			.buffer = elementBuffer
		}
	};

	return Mesh::InstancedElements(buffers, 2, indexCount, 1, GL_UNSIGNED_INT);
}

#include <fstream>
std::string readExternalFile(const char* name) {
	std::string contents;

	std::ifstream file;
	file.open(name, std::fstream::in);

	if (!file.is_open())
		std::cerr << "Failed to load file " << name << ": " << strerror(errno) << "\n";

	std::string line;
	while (getline(file, line)) {
		contents += line;
		contents += "\n";
	}

	file.close();

	return std::string(contents);
}

void onDebugOutput(GLenum source, GLenum type, GLuint id, GLenum severity, GLsizei length, const char* message, const void* /* userParam */) {
	std::cerr << "OpenGL ";
	switch (severity) {
		case GL_DEBUG_SEVERITY_HIGH: std::cerr << "high severity"; break;
		case GL_DEBUG_SEVERITY_MEDIUM: std::cerr << "moderately severity"; break;
		case GL_DEBUG_SEVERITY_LOW: std::cerr << "low severity"; break;
		case GL_DEBUG_SEVERITY_NOTIFICATION: std::cerr << "notification"; break;
		default: std::cerr << "[unknown severity " << severity << "]"; break;
	}
	std::cerr << " ";
	switch (type) {
		case GL_DEBUG_TYPE_ERROR: std::cerr << "error"; break;
		case GL_DEBUG_TYPE_DEPRECATED_BEHAVIOR: std::cerr << "deprecation warning"; break;
		case GL_DEBUG_TYPE_UNDEFINED_BEHAVIOR: std::cerr << "undefined behavior warning"; break;
		case GL_DEBUG_TYPE_PORTABILITY: std::cerr << "portability warning"; break;
		case GL_DEBUG_TYPE_PERFORMANCE: std::cerr << "performance warning"; break;
		case GL_DEBUG_TYPE_MARKER: std::cerr << "debug marker"; break;
		case GL_DEBUG_TYPE_PUSH_GROUP: std::cerr << "pushed group"; break;
		case GL_DEBUG_TYPE_POP_GROUP: std::cerr << "popped group"; break;
		case GL_DEBUG_TYPE_OTHER: std::cerr << "debug message"; break;
		default: std::cerr << "[unknown message type " << type << "]"; break;
	}
	std::cerr << " from ";
	switch (source) {
		case GL_DEBUG_SOURCE_API: std::cerr << "API"; break;
		case GL_DEBUG_SOURCE_WINDOW_SYSTEM: std::cerr << "window system"; break;
		case GL_DEBUG_SOURCE_SHADER_COMPILER: std::cerr << "shader compiler"; break;
		case GL_DEBUG_SOURCE_THIRD_PARTY: std::cerr << "third party"; break;
		case GL_DEBUG_SOURCE_APPLICATION: std::cerr << "application"; break;
		case GL_DEBUG_SOURCE_OTHER: std::cerr << "unknown source"; break;
		default: std::cerr << "[unknown source type " << source << "]"; break;
	}
	std::cerr << ": ";
	if (length < 0)
		std::cerr << message;
	else
		std::cerr << std::string(message, length);
		
	std::cerr << " (message id: " << id << ")\n";
}

void onGLFWError(int errorCode, const char* error) {
	std::cerr << "GLFW error: " << error << " (error code: " << errorCode << ")\n";
}

int main() {
	glfwSetErrorCallback(onGLFWError);
	glfwInit();
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, 1);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
	glfwWindowHint(GLFW_OPENGL_DEBUG_CONTEXT, true);
	glfwWindowHint(GLFW_SAMPLES, 4);
	glfwWindowHint(GLFW_VISIBLE, false);
	GLFWwindow* window = glfwCreateWindow(1, 1, "You aren't supposed to see this", NULL, NULL);
	glfwMakeContextCurrent(window);

	Mesh::InstancedElements sphere = processMesh("../meshes/sphere.obj");
	Shader::Program shader;

	shader.add(readExternalFile("../shaders/vertex.glsl").c_str(), -1, GL_VERTEX_SHADER);
	shader.add(readExternalFile("../shaders/fragment.glsl").c_str(), -1, GL_FRAGMENT_SHADER);
	shader.link();
	shader.use();
}