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

// Trie (prefix tree) structure for LZ78 compression
struct dict {
    int index;
    struct dict* characters[LZ78_DICT_SIZE];
};

// Free the dictionary trie
void delete_dict(struct dict* tree) {
    if (!tree) {
        return;
    }
    for (int i = 0; i < LZ78_DICT_SIZE; i++) {
        delete_dict(tree->characters[i]);
    }
    free(tree);
}

// LZ78 Compression
void lz78_compress(FILE* in, FILE* out) {
    struct dict* root = calloc(1, sizeof(struct dict));
    struct dict* current = root;
    int index = 1;
    int c;

    while ((c = fgetc(in)) != EOF) {
        if (current->characters[c]) {
            current = current->characters[c];
        } else {
            current->characters[c] = calloc(1, sizeof(struct dict));
            current->characters[c]->index = index++;
            fprintf(out, "%d-%c\n", current->index, c);
            current = root;
        }
    }

    delete_dict(root);
}

// LZ78 Decompression
void lz78_decompress(FILE* in, FILE* out) {
    char buffer[LZ78_DICT_SIZE][BUFFER_SIZE] = {""};
    int index, dict_index = 1;
    char c;

    while (fscanf(in, "%d-%c\n", &index, &c) == 2) {
        if (index > 0) {
            fprintf(out, "%s", buffer[index]);
        }
        fputc(c, out);
        snprintf(buffer[dict_index], BUFFER_SIZE, "%s%c", buffer[index], c);
        dict_index++;
    }
}

// Compress function
int compress(const char* input_file_name, const char* output_file_name) {
    FILE* input_file = fopen(input_file_name, "rb");
    if (!input_file) {
        perror("Error opening input file");
        return -1;
    }

    FILE* output_file = fopen(output_file_name, "wb");
    if (!output_file) {
        perror("Error opening output file");
        fclose(input_file);
        return -1;
    }

    lz78_compress(input_file, output_file);

    fclose(input_file);
    fclose(output_file);

    printf("File compressed successfully.\n");
    return 0;
}

// Decompress function
int decompress(const char* input_file_name, const char* output_file_name) {
    FILE* input_file = fopen(input_file_name, "rb");
    if (!input_file) {
        perror("Error opening input file");
        return -1;
    }

    FILE* output_file = fopen(output_file_name, "wb");
    if (!output_file) {
        perror("Error opening output file");
        fclose(input_file);
        return -1;
    }

    lz78_decompress(input_file, output_file);

    fclose(input_file);
    fclose(output_file);

    printf("File decompressed successfully.\n");
    return 0;
}