/*
 *  <Short Description>
 *  Copyright (C) 2024  Brett Terpstra
 *
 *  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/>.
 */

#ifndef BLT_WITH_GRAPHICS_OBJ_LOADER_H
#define BLT_WITH_GRAPHICS_OBJ_LOADER_H

#include "blt/math/vectors.h"
#include "blt/std/hashmap.h"
#include <utility>
#include <vector>
#include <string_view>

namespace blt::gfx
{
    
    typedef blt::vec3 vertex_t;
    typedef blt::vec2 uv_t;
    typedef blt::vec3 normal_t;
    
    struct face_t
    {
        std::int32_t vertex, uv, normal;
    };
    
    struct constructed_vertex_t
    {
        vertex_t vertex;
        uv_t uv;
        normal_t normal;
    };
    
    struct triangle_t
    {
        std::int32_t v1, v2, v3;
    };
    
    class obj_loader;
    
    class obj_object_t
    {
            friend obj_loader;
        private:
            // TODO: shared VBO?
            std::string object_name;
            std::vector<constructed_vertex_t> vertices_;
            std::vector<std::int32_t> indices_;
            
            obj_object_t(std::string_view name, std::vector<constructed_vertex_t> vertices, std::vector<std::int32_t> indices):
                    object_name(name), vertices_(std::move(vertices)), indices_(std::move(indices))
            {}
        
        public:
            inline const std::vector<constructed_vertex_t>& vertices()
            {
                return vertices_;
            };
            
            inline const std::vector<std::int32_t>& indices()
            {
                return indices_;
            };
    };
    
    class obj_loader
    {
        private:
            std::vector<vertex_t> vertices;
            std::vector<uv_t> uvs;
            std::vector<normal_t> normals;
            struct object_data
            {
                std::string object_name;
                // maps between vertex indices -> face (constructed vertex)
                HASHMAP<std::int32_t, constructed_vertex_t> vertex_data;
                std::vector<std::int32_t> indices;
            };
        
        private:
            void parse_face(std::string_view line);
        
        public:
            void parseFile(std::string_view file);
    };
    
    std::vector<obj_object_t> quick_load(std::string_view file);
    
}

#endif //BLT_WITH_GRAPHICS_OBJ_LOADER_H