#include "../../include/model_loader/ObjModelLoader.hpp"
#include "../../include/File.hpp"
#include "../../include/DataView.hpp"
#include "../../include/Image.hpp"
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <assert.h>
#include <libgen.h>
#include <string>

namespace amalgine {
    static StringView get_line(char *str, size_t size) {
        for(size_t i = 0; i < size; ++i) {
            char c = str[i];
            if(c == '\n' || c == '\r')
                return { str, i };
        }
        return { str, size };
    }

    static bool is_whitespace(char c) {
        switch(c) {
            case ' ':
            case '\t':
            case '\n':
            case '\r':
            case '\v':
                return true;
            default:
                return false;
        }
    }

    static bool contains_non_whitespace(const char *str, size_t size) {
        for(size_t i = 0; i < size; ++i)  {
            if(!is_whitespace(str[i]))
                return true;
        }
        return false;
    }

    // Return the number of columns, limited by @output_size
    static int split_columns(const StringView &str, char split_char, StringView *output, int output_size) {
        char *data = str.data;
        ssize_t size = str.size;

        int column = 0;
        while(size > 0) {
            char *found_ptr = (char*)memchr(data, split_char, size);
            if(!found_ptr)
                found_ptr = data + size;

            size_t column_size = static_cast<size_t>(found_ptr - data);
            if(column_size > 0 && contains_non_whitespace(data, column_size)) {
                output[column++] = { data, column_size };
                if(column == output_size)
                    break;
            }

            data = found_ptr + 1;
            size -= (column_size + 1);
        }

        return column;
    }

    static size_t find_or_end(const StringView &str, char c) {
        char *found_ptr = (char*)memchr(str.data, c, str.size);
        if(!found_ptr)
            found_ptr = str.data + str.size;
        return static_cast<size_t>(found_ptr - str.data);
    }

    struct FaceData {
        int vertex_index;
        int texcoord_index;
        int normal_index;
    };

    // TODO: Optimize? dont use sscanf 3 times
    static bool split_faces(StringView *input, FaceData *face_data) {
        input->data[input->size] = '\0';

        face_data->vertex_index = 0;
        face_data->texcoord_index = 0;
        face_data->normal_index = 0;
        if(sscanf(input->data, "%d/%d/%d", &face_data->vertex_index, &face_data->texcoord_index, &face_data->normal_index) == 3)
            return true;

        face_data->texcoord_index = 0;
        if(sscanf(input->data, "%d//%d", &face_data->vertex_index, &face_data->normal_index) == 2)
            return true;

        return sscanf(input->data, "%d/%d", &face_data->vertex_index, &face_data->texcoord_index) == 2;
    }

    struct Material {
        Image *image;
    };

    static Result<Material> load_material_from_file(const char *filepath);

    bool ObjModelLoader::load_from_file(const char *filepath, std::vector<Triangle3D> &triangles, std::vector<vec2f> &texture_coords, Image **image) {
        triangles.clear();
        texture_coords.clear();
        *image = nullptr;

        size_t file_size;
        char *file_data = file_get_content(filepath, &file_size);
        if(!file_data)
            return false;

        std::string dir_path = filepath;
        dirname(&dir_path[0]);
        const int dir_path_size = strlen(dir_path.c_str());
        dir_path.resize(dir_path_size);

        const int max_columns = 8;
        StringView columns[max_columns];

        std::vector<Vertex3D> vertices;
        std::vector<vec2f> temp_texture_coords;

        char *data = file_data;
        ssize_t size = file_size;
        while(size > 0) {
            StringView line_data = get_line(data, size);

            if(line_data.size > 2 && memcmp(line_data.data, "v ", 2) == 0) {
                //printf("line: |%.*s|\n", line_data.size, line_data.data);
                StringView column_data = { line_data.data + 2, line_data.size - 2 };

                int num_columns = split_columns(column_data, ' ', columns, max_columns);
                if(num_columns >= 3) {
                    columns[0].data[columns[0].size] = '\0';
                    columns[1].data[columns[1].size] = '\0';
                    columns[2].data[columns[2].size] = '\0';
                    vertices.push_back({ atof(columns[0].data), atof(columns[1].data), atof(columns[2].data) });
                }
            } else if(line_data.size > 2 && memcmp(line_data.data, "f ", 2) == 0) {
                //printf("line: |%.*s|\n", line_data.size, line_data.data);
                StringView column_data = { line_data.data + 2, line_data.size - 2 };

                int num_columns = split_columns(column_data, ' ', columns, max_columns);
                if(num_columns == 3 || num_columns == 4) {
                    bool valid = true;
                    // TODO: Handle these when they are not set in the below loop
                    int vertex_indices[4];
                    int texture_coord_indices[4];
                    int normal_indices[4]; // TODO: Use this

                    for(int i = 0; i < num_columns; ++i) {
                        FaceData face_data;
                        if(!split_faces(&columns[i], &face_data)) {
                            valid = false;
                            abort();
                            break;
                        }

                        vertex_indices[i] = face_data.vertex_index;
                        texture_coord_indices[i] = face_data.texcoord_index;
                        normal_indices[i] = face_data.normal_index;

                        if(vertex_indices[i] < 1 || vertex_indices[i] > vertices.size()) {
                            valid = false;
                            abort();
                            break;
                        }

                        if(texture_coord_indices[i] != 0 && (texture_coord_indices[i] < 1 || texture_coord_indices[i] > temp_texture_coords.size())) {
                            valid = false;
                            abort();
                            break;
                        }

                        --vertex_indices[i];
                        --texture_coord_indices[i];
                        --normal_indices[i];
                    }

                    if(valid) {
                        if(num_columns == 3) { // Triangle
                            triangles.push_back({ vertices[vertex_indices[0]], vertices[vertex_indices[1]], vertices[vertex_indices[2]] });

                            if(texture_coord_indices[0] >= 0) {
                                texture_coords.push_back(temp_texture_coords[texture_coord_indices[0]]);
                                texture_coords.push_back(temp_texture_coords[texture_coord_indices[1]]);
                                texture_coords.push_back(temp_texture_coords[texture_coord_indices[2]]);
                            }
                        } else if(num_columns == 4) { // Quad, convert to triangle. TODO: Support rendering quads instead of converting to triangles
                            triangles.push_back({ vertices[vertex_indices[0]], vertices[vertex_indices[1]], vertices[vertex_indices[2]] });
                            triangles.push_back({ vertices[vertex_indices[2]], vertices[vertex_indices[3]], vertices[vertex_indices[0]] });

                            if(texture_coord_indices[0] >= 0) {
                                texture_coords.push_back(temp_texture_coords[texture_coord_indices[0]]);
                                texture_coords.push_back(temp_texture_coords[texture_coord_indices[1]]);
                                texture_coords.push_back(temp_texture_coords[texture_coord_indices[2]]);

                                texture_coords.push_back(temp_texture_coords[texture_coord_indices[2]]);
                                texture_coords.push_back(temp_texture_coords[texture_coord_indices[3]]);
                                texture_coords.push_back(temp_texture_coords[texture_coord_indices[0]]);
                            }
                        }
                    }
                }
            } else if(line_data.size > 3 && memcmp(line_data.data, "vt ", 3) == 0) {
                StringView column_data = { line_data.data + 3, line_data.size - 3 };
                int num_columns = split_columns(column_data, ' ', columns, max_columns);
                if(num_columns == 2) {
                    columns[0].data[columns[0].size] = '\0';
                    columns[1].data[columns[1].size] = '\0';
                    temp_texture_coords.push_back({ atof(columns[0].data), 1.0f - atof(columns[1].data) });
                }
            } else if(line_data.size > 7 && memcmp(line_data.data, "mtllib ", 7) == 0) {
                StringView column_data = { line_data.data + 7, line_data.size - 7 };
                int num_columns = split_columns(column_data, ' ', columns, max_columns);
                if(num_columns == 1) {
                    std::string material_path = dir_path + '/';
                    material_path.append(columns[0].data, columns[0].size);
                    printf("mtl file: %s\n", material_path.c_str());

                    assert(!*image);
                    Result<Material> material = load_material_from_file(material_path.c_str());
                    if(!material) {
                        fprintf(stderr, "Warning: %s\n", material.getErrorMsg().c_str());
                    } else {
                        *image = material->image;
                    }
                }
            }

            data += (line_data.size + 1);
            size -= (line_data.size + 1);
        }

        printf("num tex coords: %d\n", texture_coords.size());

        cleanup:
        free(file_data);
        return true;
    }

    Result<Material> load_material_from_file(const char *filepath) {
        size_t file_size;
        char *file_data = file_get_content(filepath, &file_size);
        if(!file_data)
            return Result<Material>::Err("Failed to load material: " + std::string(filepath));

        std::string dir_path = filepath;
        dirname(&dir_path[0]);
        const int dir_path_size = strlen(dir_path.c_str());
        dir_path.resize(dir_path_size);

        Image *image = nullptr;
        
        char *data = file_data;
        ssize_t size = file_size;
        while(size > 0) {
            StringView line_data = get_line(data, size);

            if(line_data.size > 7 && memcmp(line_data.data, "map_Kd ", 7) == 0) {
                StringView texture_file = { line_data.data + 7, line_data.size - 7 };
                line_data.data[line_data.size] = '\0';

                std::string texture_path;
                texture_path.resize(dir_path_size + 1 + texture_file.size);
                memcpy(&texture_path[0], dir_path.data(), dir_path_size);
                texture_path[dir_path_size] = '/';
                memcpy(&texture_path[dir_path_size + 1], texture_file.data, texture_file.size);
                printf("texture file: |%.*s|\n", texture_path.size(), texture_path.data());

                Result<Image*> image_result = Image::loadFromFile(texture_path.c_str());
                if(!image_result)
                    return Result<Material>::Err(image_result.getErrorMsg(), image_result.getErrorCode());

                image = image_result.unwrap();
                break;
            }

            data += (line_data.size + 1);
            size -= (line_data.size + 1);
        }

        free(file_data);
        return Result<Material>::Ok({ image });
    }
}