#include "obj_parser.h"

#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <cstddef>
#include <array>
#include "math/vector.h"
#include "o3d/mesh.h"
#include "o3d/vertex_data.h"

namespace engine {

namespace {

std::vector<std::string> split(const std::string& s, char sep) {
    std::vector<std::string> res;
    std::string::size_type last_ind = 0;
    for (std::string::size_type ind = 0; ind < s.length(); ind++) {
        if (s[ind] == sep) {
            res.push_back(s.substr(last_ind, ind - last_ind));
            last_ind = ind + 1;
        }
    }
    res.push_back(s.substr(last_ind));
    return res;
}

float parse_float(const std::string& s) {
    std::string::size_type ind = 0;
    bool positive = true;
    while (ind < s.length() && (s[ind] == '+' || s[ind] == '-'))
        if (s[ind++] == '-')
            positive = !positive;

    // TODO: improve error checking
    if (ind == s.length())
        return 0.f;

    int n = 0;
    while (ind < s.length() && s[ind] >= '0' && s[ind] <= '9')
        n = n * 10 + static_cast<int>(s[ind++]) - static_cast<int>('0');

    if (ind == s.length())
        return (positive ? 1.f : -1.f) * static_cast<float>(n);

    // TODO: improve error checking
    if (s[ind] != '.')
        return 0.f;

    ind++;

    float decimal_part = 0.f;
    float decimal_fac = .1f;
    while (ind < s.length() && s[ind] >= '0' && s[ind] <= '9') {
        decimal_part += decimal_fac * static_cast<float>(static_cast<int>(s[ind++]) - static_cast<int>('0'));
        decimal_fac *= .1f;
    }

    // TODO: improve error checking
    if (ind != s.length())
        return 0.f;

    return (positive ? 1.f : -1.f) * (static_cast<float>(n) + decimal_part);
}

float parse_int(const std::string& s) {
    std::string::size_type ind = 0;
    bool positive = true;
    while (ind < s.length() && (s[ind] == '+' || s[ind] == '-'))
        if (s[ind++] == '-')
            positive = !positive;

    // TODO: improve error checking
    if (ind == s.length())
        return 0.f;

    int n = 0;
    while (ind < s.length() && s[ind] >= '0' && s[ind] <= '9')
        n = n * 10 + static_cast<int>(s[ind++]) - static_cast<int>('0');

    // TODO: improve error checking
    if (ind != s.length())
        return 0.f;

    return (positive ? 1.f : -1.f) * n;
}

}

o3d::Mesh parse_object(const std::string& obj_path) {
    o3d::Mesh mesh;
    std::ifstream obj_file(obj_path);
    std::string line;
    while (std::getline(obj_file, line)) {
        if (line.length() == 0 || line[0] == '#')
            continue;
        if (line.rfind("o ", 0) == 0) {
            // std::cout << "Object: " << line.substr(2) << std::endl;
        } else if (line.rfind("v ", 0) == 0) {
            auto s_coords = split(line.substr(2), ' ');
            math::Vector4 v{parse_float(s_coords[0]), parse_float(s_coords[1]), parse_float(s_coords[2]), 1.f};
            // std::cout << "Vertex x: " << v.x << " y: " << v.y << " z: " << v.z << std::endl;
            mesh.vertices.push_back(v);
        } else if (line.rfind("vn ", 0) == 0) {
            auto s_coords = split(line.substr(3), ' ');
            math::Vector3 vn{parse_float(s_coords[0]), parse_float(s_coords[1]), parse_float(s_coords[2])};
            // std::cout << "Vertex normal x: " << vn.x << " y: " << vn.y << " z: " << vn.z << std::endl;
            mesh.normals.push_back(vn);
        } else if (line.rfind("s ", 0) == 0) {
            // auto smooth = false;
            // auto s_smooth = line.substr(2);
            // if (s_smooth == "0" || s_smooth == "off") {
            //     smooth = false;
            // } else if (s_smooth == "1" || s_smooth == "on") {
            //     smooth = true;
            // }
            // std::cout << "Smooth: " << std::boolalpha << smooth << std::endl;
        } else if (line.rfind("f ", 0) == 0) {
            std::array<std::array<std::size_t, 2>, 3> indices;
            auto line_split = split(line.substr(2), ' ');
            for (int i = 0; i < 3; i++) {
                auto indices_s_group = split(line_split[i], '/');
                indices[i][0] = parse_int(indices_s_group[0]) - 1;
                indices[i][1] = parse_int(indices_s_group[2]) - 1;
            }
            // std::cout << "Face:"
            //     << " 1: vertex: " << indices[0][0] << " normal: " << indices[0][1]
            //     << " 2: vertex: " << indices[1][0] << " normal: " << indices[1][1]
            //     << " 3: vertex: " << indices[2][0] << " normal: " << indices[2][1]
            //     << std::endl;
            mesh.indices.push_back(indices);
        }
    }
    return mesh;
}

}