#include "mesh.h"
#include <fstream>
#include <sstream>
#include <iostream>
#include <stdexcept>
#include <filesystem>

namespace fs = std::filesystem;

std::map<std::string, Material> load_mtl_materials(const std::string& mtl_path)
{
    std::map<std::string, Material> materials;
    std::ifstream file(mtl_path);
    if (!file.is_open()) {
        std::cerr << "Warning: could not open MTL file: " << mtl_path << std::endl;
        return materials;
    }

    std::string line, current_mtl;
    while (std::getline(file, line)) {
        std::istringstream ss(line);
        std::string keyword;
        ss >> keyword;

        if (keyword == "newmtl") {
            ss >> current_mtl;
            materials[current_mtl] = Material{Color(255, 255, 255), ""}; // Default white, no texture
        } else if (keyword == "Kd") {
            float r, g, b;
            ss >> r >> g >> b;
            if (materials.count(current_mtl)) {
                materials[current_mtl].color = Color(
                    static_cast<uint8_t>(r * 255),
                    static_cast<uint8_t>(g * 255),
                    static_cast<uint8_t>(b * 255)
                );
            }
        } else if (keyword == "map_Kd") {
            std::string texture_path;
            ss >> texture_path;
            if (materials.count(current_mtl)) {
                materials[current_mtl].texture_path = texture_path;
            }
        }
    }

    return materials;
}

std::vector<Triangle> load_obj(const std::string& obj_path, Renderer* renderer)
{
    std::ifstream file(obj_path);
    if (!file.is_open()) {
        throw std::runtime_error("Failed to open OBJ file: " + obj_path);
    }

    std::vector<Vec3> positions;
    std::vector<Vec2> texcoords;
    std::map<std::string, Material> materials;
    std::map<std::string, GLuint> texture_map;
    std::vector<Triangle> triangles;

    std::string current_material = "";
    fs::path base_path = fs::path(obj_path).parent_path();

    std::string line;
    while (std::getline(file, line)) {
        std::istringstream ss(line);
        std::string keyword;
        ss >> keyword;

        if (keyword == "v") {
            float x, y, z;
            ss >> x >> y >> z;
            positions.emplace_back((int)(x * 4096), (int)(y * 4096), (int)(z * 4096));
        } else if (keyword == "vt") {
            float u, v;
            ss >> u >> v;
            texcoords.emplace_back(u, 1.0f - v);  // flip v
        } else if (keyword == "f") {
            std::vector<std::string> tokens;
            std::string token;
            while (ss >> token) tokens.push_back(token);

            std::vector<int> v_idx, t_idx;
            for (const auto& t : tokens) {
                std::stringstream ts(t);
                std::string part;
                int vi = -1, ti = -1;

                std::getline(ts, part, '/');
                if (!part.empty()) vi = std::stoi(part) - 1;

                if (std::getline(ts, part, '/') && !part.empty())
                    ti = std::stoi(part) - 1;

                v_idx.push_back(vi);
                t_idx.push_back(ti);
            }

            // Triangulate face
            for (size_t i = 1; i + 1 < v_idx.size(); ++i) {
                Triangle tri;
                tri.v0 = positions[v_idx[0]];
                tri.v1 = positions[v_idx[i]];
                tri.v2 = positions[v_idx[i + 1]];

                tri.uv0 = (t_idx[0] >= 0 && t_idx[0] < (int)texcoords.size()) ? texcoords[t_idx[0]] : Vec2(0, 0);
                tri.uv1 = (t_idx[i] >= 0 && t_idx[i] < (int)texcoords.size()) ? texcoords[t_idx[i]] : Vec2(0, 0);
                tri.uv2 = (t_idx[i + 1] >= 0 && t_idx[i + 1] < (int)texcoords.size()) ? texcoords[t_idx[i + 1]] : Vec2(0, 0);

                if (materials.count(current_material)) {
                    tri.color = materials[current_material].color;
                    tri.texture = texture_map[current_material];
                } else {
                    tri.color = Color(255, 255, 255); // Fallback white
                    tri.texture = 0;                   // No texture
                }

                triangles.push_back(tri);
            }
        } else if (keyword == "mtllib") {
            std::string mtl_file;
            ss >> mtl_file;
            fs::path mtl_path = base_path / mtl_file;
            materials = load_mtl_materials(mtl_path.string());

            // Load textures for all materials
            for (const auto& mat_pair : materials) {
                const std::string& mat_name = mat_pair.first;
                const Material& mat = mat_pair.second;
                if (!mat.texture_path.empty()) {
                    fs::path texture_full_path = base_path / mat.texture_path;
                    texture_map[mat_name] = renderer->load_texture(texture_full_path.string());
                } else {
                    texture_map[mat_name] = 0; // No texture
                }
            }
        } else if (keyword == "usemtl") {
            ss >> current_material;
        }
    }

    return triangles;
}