#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "compressor.h"

#define BUFFER_SIZE 4096
#define MAX_SYMBOLS 257
#define WINDOW_CAPACITY 4096
#define MAX_MATCH_LENGTH 15
#define BUFFER_CAPACITY 4096
// Макрос для обмена двух узлов
#define SWAP_NODES(a, b) { Node* temp = a; a = b; b = temp; }

// Определение структуры узла дерева
typedef struct Node {
    int symbol;                
    unsigned int frequency;     
    struct Node *left, *right;  
} Node;

typedef struct LZ77{
    int posun;
    int dlzka;
    char dalsi_znak;
} LZ77;

Node* create_node(int symbol, unsigned int frequency) {
    Node* node = (Node*)malloc(sizeof(Node));
    node->symbol = symbol;
    node->frequency = frequency;
    node->left = node->right = NULL;
    return node;
}

Node* build_huffman_tree(const unsigned int* frequencies) {
    Node* nodes[MAX_SYMBOLS];
    int node_count = 0;

    for (int i = 0; i < MAX_SYMBOLS; i++) {
        if (frequencies[i] > 0) {
            nodes[node_count++] = create_node(i, frequencies[i]);
        }
    }

    while (node_count > 1) {
        // Сортируем узлы по частоте
        for (int i = 0; i < node_count - 1; i++) {
            for (int j = i + 1; j < node_count; j++) {
                if (nodes[i]->frequency > nodes[j]->frequency) {
                    SWAP_NODES(nodes[i], nodes[j]);
                }
            }
        }

        Node* left = nodes[0];
        Node* right = nodes[1];
        Node* parent = create_node(-1, left->frequency + right->frequency);
        parent->left = left;
        parent->right = right;

        // Заменяем объединенные узлы новым родительским узлом
        nodes[0] = parent;
        nodes[1] = nodes[--node_count];
    }

    return nodes[0];
}

void generate_huffman_codes(Node* root, char* code, int depth, char codes[MAX_SYMBOLS][MAX_SYMBOLS]) {
    if (!root->left && !root->right) {
        code[depth] = '\0'; 
        strcpy(codes[root->symbol], code);
        return;
    }
    if (root->left) {
        code[depth] = '0'; 
        generate_huffman_codes(root->left, code, depth + 1, codes);
    }
    if (root->right) {
        code[depth] = '1'; 
        generate_huffman_codes(root->right, code, depth + 1, codes);
    }
}

void free_huffman_tree(Node* root) {
    if (!root) return;
    free_huffman_tree(root->left);
    free_huffman_tree(root->right);
    free(root);
}

int compress_1(const char* input_file, const char* output_file) {
    FILE* input = fopen(input_file, "rb");
    FILE* output = fopen(output_file, "wb");
    if (!input || !output) return -1;

    unsigned int frequencies[MAX_SYMBOLS] = {0};
    unsigned char buffer[BUFFER_SIZE];
    size_t bytes_read;

    // Подсчет частот символов
    while ((bytes_read = fread(buffer, 1, BUFFER_SIZE, input)) > 0) {
        for (size_t i = 0; i < bytes_read; i++) {
            frequencies[buffer[i]]++;
        }
    }
    frequencies[256] = 1; // Добавляем маркер EOF

    Node* root = build_huffman_tree(frequencies);
    if (!root) return -1;

    // Генерация кодов Хаффмана
    char codes[MAX_SYMBOLS][MAX_SYMBOLS] = {{0}};
    char code[MAX_SYMBOLS] = {0};
    generate_huffman_codes(root, code, 0, codes);


    fwrite(frequencies, sizeof(frequencies[0]), MAX_SYMBOLS, output);

    rewind(input);
    unsigned char current_byte = 0;
    int bit_count = 0;

    while ((bytes_read = fread(buffer, 1, BUFFER_SIZE, input)) > 0) {
        for (size_t i = 0; i < bytes_read; i++) {
            char* symbol_code = codes[buffer[i]];
            for (size_t j = 0; symbol_code[j] != '\0'; j++) {
                current_byte = (current_byte << 1) | (symbol_code[j] - '0');
                bit_count++;
                if (bit_count == 8) {
                    fwrite(&current_byte, 1, 1, output);
                    current_byte = 0;
                    bit_count = 0;
                }
            }
        }
    }

    char* eof_code = codes[256];
    for (size_t j = 0; eof_code[j] != '\0'; j++) {
        current_byte = (current_byte << 1) | (eof_code[j] - '0');
        bit_count++;
        if (bit_count == 8) {
            fwrite(&current_byte, 1, 1, output);
            current_byte = 0;
            bit_count = 0;
        }
    }
    if (bit_count > 0) {
        current_byte <<= (8 - bit_count);
        fwrite(&current_byte, 1, 1, output);
    }

    fclose(input);
    fclose(output);
    free_huffman_tree(root);
    return 0;
}

int decompress_1(const char* input_file, const char* output_file) {
    FILE* input = fopen(input_file, "rb");
    FILE* output = fopen(output_file, "wb");
    if (!input || !output) return -1;

    unsigned int frequencies[MAX_SYMBOLS] = {0};
    fread(frequencies, sizeof(frequencies[0]), MAX_SYMBOLS, input);
    Node* root = build_huffman_tree(frequencies);
    if (!root) return -1;

    Node* current = root;
    unsigned char byte;
    int bit;


    while (fread(&byte, 1, 1, input) == 1) {
        for (bit = 7; bit >= 0; bit--) {
            current = (byte & (1 << bit)) ? current->right : current->left;

            if (!current->left && !current->right) {
                if (current->symbol == 256) { // Маркер EOF
                    fclose(input);
                    fclose(output);
                    free_huffman_tree(root);
                    return 0;
                }
                fwrite(&current->symbol, 1, 1, output);
                current = root;
            }
        }
    }

    fclose(input);
    fclose(output);
    free_huffman_tree(root);
    return 0;
}


int compress_2(const char *input_file, const char *output_file) {
    FILE *source = fopen(input_file, "rb");
    if (source == NULL) {
        return -1;
    }

    FILE *destination = fopen(output_file, "wb");
    if (destination == NULL) {
        fclose(source);
        return -1;
    }

    fseek(source, 0, SEEK_END);
    long file_size = ftell(source);
    if (file_size > 10 * 1024 * 1024) {
        fclose(source);
        fclose(destination);
        return -1;
    }
    fseek(source, 0, SEEK_SET);  // Возврат в начало файла для чтения

    char *input_data = malloc(file_size);
    if (input_data == NULL) {
        fclose(source);
        fclose(destination);
        return -1;
    }
    fread(input_data, 1, file_size, source);

    int index = 0;
    while (index < file_size) {
        LZ77 element = {0, 0, input_data[index]};  // Инициализация элемента с текущим символом
        int best_length = 0, best_offset = 0;
        int start_idx;

        if ((index - WINDOW_CAPACITY) > 0) {
            start_idx = index - WINDOW_CAPACITY;
        } else {
            start_idx = 0;
        }  // Поиск начала окна

        // Поиск наилучшего совпадения в окне
        for (int i = start_idx; i < index; i++) {
            int match_length = 0;
            while (match_length < MAX_MATCH_LENGTH && index + match_length < file_size &&
                   input_data[i + match_length] == input_data[index + match_length]) {
                match_length++;
            }

            if (match_length > best_length) {
                best_length = match_length;
                best_offset = index - i;
            }

            if (match_length == MAX_MATCH_LENGTH) {
                break;
            }
        }

        // Если найдено совпадение записываем его в элемент иначе сохраняем символ
        if (best_length > 1) {
            element.posun = best_offset;
            element.dlzka = best_length;
            element.dalsi_znak = input_data[index + best_length];
            index += best_length + 1;
        } else {
            element.posun = 0;
            element.dlzka = 0;
            element.dalsi_znak = input_data[index];
            index++;
        }


        unsigned short combined = (element.posun << 4) | (element.dlzka & 0xF);  // Объединение posun и dlzka в одно значение
        fwrite(&combined, sizeof(unsigned short), 1, destination);
        fwrite(&element.dalsi_znak, sizeof(char), 1, destination);
    }

    fwrite(&file_size, sizeof(file_size), 1, destination);
    free(input_data);
    fclose(source);
    fclose(destination);
    return ftell(destination);
}


int decompress_2(const char *input_file, const char *output_file) {
    FILE *source = fopen(input_file, "rb");
    if (source == NULL) {
        return -1;
    }

    FILE *destination = fopen(output_file, "wb");
    if (destination == NULL) {
        fclose(source);
        return -1;
    }

    char *buffer = malloc(WINDOW_CAPACITY);
    if (buffer == NULL) {
        fclose(source);
        fclose(destination);
        return -1;
    }

    memset(buffer, 0, WINDOW_CAPACITY);
// Переход к концу файла для чтения размера исходного файла
    fseek(source, -sizeof(long), SEEK_END);
    long original_size;
    if (fread(&original_size, sizeof(long), 1, source) != 1) {
        free(buffer);
        fclose(source);
        fclose(destination);
        return -1;
    }
    // Возврат в начало файла для распаковки
    fseek(source, 0, SEEK_SET);

    int written_bytes = 0, buffer_position = 0;
    while (written_bytes < original_size) {
        unsigned short combined;
        char dalsi_znak;
        if (fread(&combined, sizeof(unsigned short), 1, source) != 1) {
            break;
        }
        if (fread(&dalsi_znak, sizeof(char), 1, source) != 1) {
            break;
        }

        int posun = combined >> 4;
        int dlzka = combined & 0xF;

        // Восстановление данных из совпадений в буфере
        if (dlzka > 0) {
            int start_idx = buffer_position - posun;
            for (int i = 0; i < dlzka; i++) {
                char current = buffer[(start_idx + i) % WINDOW_CAPACITY];
                fputc(current, destination);
                buffer[buffer_position % WINDOW_CAPACITY] = current;
                buffer_position++;
                written_bytes++;
            }
        }

        // Запись следующего символа в файл
        if (written_bytes < original_size) {
            fputc(dalsi_znak, destination);
            buffer[buffer_position % WINDOW_CAPACITY] = dalsi_znak;
            buffer_position++;
            written_bytes++;
        }
    }

    free(buffer);
    fclose(source);
    fclose(destination);
    return ftell(destination);
}