#include <stdlib.h>
#include <stdio.h>
#include <netdb.h>
#include <errno.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <string.h>
#include <math.h>
#include <pthread.h>

#ifdef __APPLE__
#include "./endian.h"
#else
#include <endian.h>
#endif

#include "./cascade.h"
#include "./sha256.h"

char tracker_ip[IP_LEN];
char tracker_port[PORT_LEN];
char my_ip[IP_LEN];
char my_port[PORT_LEN];

csc_file_t* cascade_files[64];
int cascade_amount;

/*
 * Frees global resources that are malloc'ed during peer downloads.
 */
void free_resources(csc_file_t* casc_file)
{
    free(casc_file->peers);
    csc_free_file(casc_file);
}

/*
 * Gets a sha256 hash of a specified file, sourcefile. The hash itself is
 * placed into the given variable 'hash'. Any size can be created, but a
 * a normal size for the hash would be given by the global variable
 * 'SHA256_HASH_SIZE', that has been defined in sha256.h
 */
void get_file_sha(const char* sourcefile, uint8_t hash[32], int size)
{
    int casc_file_size;

    FILE* fp = fopen(sourcefile, "rb");
    if (fp == 0)
    {
        printf("Failed to open source: %s\n", sourcefile);
        return;
    }

    fseek(fp, 0L, SEEK_END);
    casc_file_size = ftell(fp);
    fseek(fp, 0L, SEEK_SET);

    char buffer[casc_file_size];
    fread(buffer, casc_file_size, 1, fp);
    fclose(fp);

    get_data_sha(buffer, hash, casc_file_size, size);
}


csc_file_t* check_blocks(csc_file_t* casc_file_data) {
    casc_file_data->completed = 1;
    char* destination = casc_file_data->outputfile;

    FILE* fp = fopen(destination, "a+w");
    if (fp == NULL)
    {
        printf("Failed to open destination file %s\n", destination);
        csc_free_file(casc_file_data);
        return NULL;
    }

    void* buffer = malloc(casc_file_data->blocksize);
    if (buffer == NULL)
    {
        printf("No block buffer asigned: %ld\n", casc_file_data->blocksize);
        csc_free_file(casc_file_data);
        fclose(fp);
        return NULL;
    }

    SHA256_CTX shactx;
    for(unsigned long long i = 0; i < casc_file_data->blockcount; i++)
    {
        uint8_t* shabuffer = malloc(sizeof(uint8_t) * SHA256_HASH_SIZE);
        unsigned long long size = casc_file_data->blocks[i].length;
        if (fread(buffer, size, 1, fp) != 1)
        {
            break;
        }

        sha256_init(&shactx);
        sha256_update(&shactx, buffer, size);
        sha256_final(&shactx, shabuffer);

        if (memcmp((&(&casc_file_data->blocks[i])->hash)->x, shabuffer, 32) == 0) {
            (&casc_file_data->blocks[i])->completed = 1;
        } else {
            (&casc_file_data->blocks[i])->completed = 0;
            casc_file_data->completed = 0;
        }
    }
    free(buffer);


    if (casc_file_data->completed) {
        rewind(fp);
        buffer = malloc(casc_file_data->targetsize);
        uint8_t* shabuffer = malloc(sizeof(uint8_t) * SHA256_HASH_SIZE);
        fread(buffer, casc_file_data->targetsize, 1, fp);

        sha256_init(&shactx);
        sha256_update(&shactx, buffer, casc_file_data->targetsize);
        sha256_final(&shactx, shabuffer);

        if (!(memcmp((&casc_file_data->targethash)->x, shabuffer, 32) == 0)) {
            casc_file_data->completed = 0;
            for (unsigned long long i = 0;i < casc_file_data->blockcount;i++) {
                (&casc_file_data->blocks[i])->completed = 0;
            }
        }
        free(buffer);
    }

    fclose(fp);

    return casc_file_data;
}

/*
 * Gets a sha256 hash of specified data, sourcedata. The hash itself is
 * placed into the given variable 'hash'. Any size can be created, but a
 * a normal size for the hash would be given by the global variable
 * 'SHA256_HASH_SIZE', that has been defined in sha256.h
 */
void get_data_sha(const char* sourcedata, unsigned char* hash, uint32_t data_size, int hash_size)
{
    SHA256_CTX shactx;
    uint8_t* shabuffer = malloc(sizeof(uint8_t) * hash_size);
    sha256_init(&shactx);
    sha256_update(&shactx, sourcedata, data_size);
    sha256_final(&shactx, shabuffer);

    for (int i=0; i<hash_size; i++)
    {
        hash[i] = shabuffer[i];
    }
}

/*
 * Count how many times a character occurs in a string
 */
int count_occurences(char string[], char c)
{
    size_t i=0;
    int count=0;
    for(i=0; i<strlen(string); i++)
    {
        if(string[i] == c)
        {
            count++;
        }
    }
    return count;
}

// Adapted from: https://stackoverflow.com/a/35452093/
/*
 *  Convert a string of hexidecimal into a string of bytes
 */
uint8_t* hex_to_bytes(const char* string) {

    if(string == NULL)
       return NULL;

    size_t slength = strlen(string);
    if((slength % 2) != 0) // must be even
       return NULL;

    size_t dlength = slength / 2;

    uint8_t* data = malloc(dlength);
    memset(data, 0, dlength);

    size_t index = 0;
    while (index < slength) {
        char c = string[index];
        int value = 0;
        if(c >= '0' && c <= '9')
          value = (c - '0');
        else if (c >= 'A' && c <= 'F')
          value = (10 + (c - 'A'));
        else if (c >= 'a' && c <= 'f')
          value = (10 + (c - 'a'));
        else {
          free(data);
          return NULL;
        }

        data[(index/2)] += value << (((index + 1) % 2) * 4);
        index++;
    }

    return data;
}

/*
 * Parses a cascade file, given the sourcepath input and destination, which may or may not exist.
 * Returns a pointer to a datastructure describing the file, or NULL if the file could not be parsed
 */
csc_file_t* csc_parse_file(const char* sourcefile)
{
    FILE* fp = fopen(sourcefile, "rb");
    if (fp == 0)
    {
        printf("Failed to open source: %s\n", sourcefile);
        return NULL;
    }

    const int FILE_HEADER_SIZE = 8+8+8+8+32;

    char header[FILE_HEADER_SIZE];
    if (fread(header, 1, FILE_HEADER_SIZE, fp) != FILE_HEADER_SIZE)
    {
        printf("Failed to read magic 8 bytes header from file\n");
        fclose(fp);
        return NULL;
    }

    if (memcmp(header, "CASCADE1", 8) != 0)
    {
        printf("File does not contain magic 8 bytes in header\n");
        fclose(fp);
        return NULL;
    }

    csc_file_t* casc_file_data = (csc_file_t*)malloc(sizeof(csc_file_t));
    uint8_t hash_buf[32];
    get_file_sha(sourcefile, hash_buf, 32);
    memcpy(casc_file_data->cascadehash,hash_buf,32);

    char* outputfile = malloc(strlen(sourcefile)-7);
    memcpy(outputfile, sourcefile, strlen(sourcefile)-8);
    outputfile[strlen(sourcefile)-8] = '\0';
    casc_file_data->outputfile = outputfile;
    printf("Downloading to: %s\n", casc_file_data->outputfile);

    casc_file_data->targetsize = be64toh(*((unsigned long long*)&header[16]));
    casc_file_data->blocksize = be64toh(*((unsigned long long*)&header[24]));
    uint8_t x[32];
    for (int i = 0; i < 32; i++) {
        x[i] = (uint8_t)(*((unsigned long long*)&header[32+i]));
    }

    csc_hashdata_t* hash = malloc(sizeof(csc_hashdata_t));
    memcpy(hash->x,x,SHA256_HASH_SIZE);

    casc_file_data->targethash = *hash;
    casc_file_data->blockcount = 1 + floor(
        (casc_file_data->targetsize - 1.0)/casc_file_data->blocksize
    );
    casc_file_data->trailblocksize = casc_file_data->targetsize - (
        (casc_file_data->blockcount - 1) * casc_file_data->blocksize
    );
    casc_file_data->completed = 0;

    csc_block_t* block_list = malloc(
        sizeof(csc_block_t) * casc_file_data->blockcount
    );

    casc_file_data->blocks = block_list;

    for (unsigned long long b = 0;b < casc_file_data->blockcount; b++) {
        csc_block_t* block = &(block_list[b]);
        block->index = b;
        block->offset = b * casc_file_data->blocksize;
        if (b == casc_file_data->blockcount - 1 ) {
            block->length = casc_file_data->trailblocksize;
        } else {
            block->length = casc_file_data->blocksize;
        }

        block->completed = 0;

        uint8_t block_x[32];
        if (fread(block_x, 1, 32, fp) != 32) {
            printf("Cascade file not readable\n");
            fclose(fp);
            return NULL;
        }
        csc_hashdata_t* hash = malloc(sizeof(csc_hashdata_t));
        memcpy(hash->x,block_x,SHA256_HASH_SIZE);
        block->hash = *hash;
    }

    fclose(fp);

    return check_blocks(casc_file_data);
}

/*
 * Releases the memory allocated by a file datastructure
 */
void csc_free_file(csc_file_t* file)
{
    free(file->blocks);
    file->blocks = NULL;
    free(file);
}

size_t readbytes(int sock, uint8_t* buffer, size_t count)
{
    size_t remaining = count;
    while(remaining > 0)
    {
        size_t read = recv(sock, buffer, remaining, 0);
        if (read == 0)
            return 0;
        buffer += read;
        remaining -= read;
    }

    return count;
}

/*
 * Get a specified block from a peer on the network. The block is retrieved and then inserted directly into
 * the appropriate data file at the appropriate location.
 */
void get_block(csc_block_t* block, csc_peer_t peer, unsigned char* hash, char* output_file)
{
    printf("Attempting to get block %ld from %s:%s for %s\n", block->index, peer.ip, peer.port, output_file);

    int buffer_size;
    if (block->length + PEER_RESPONSE_HEADER_SIZE > MAX_LINE) {
        buffer_size = block->length + PEER_RESPONSE_HEADER_SIZE;
    } else {
        buffer_size = MAX_LINE;
    }
    char rio_buf[buffer_size];

    rio_t rio;
    int peer_socket;
    peer_socket = Open_clientfd(peer.ip, peer.port);
    Rio_readinitb(&rio, peer_socket);

    struct ClientRequest request;
    memcpy(request.protocol, "CASCADE1", 8);
    for (int i = 0;i<16;i++) {
        request.reserved[i] = 0;
    }
    request.block_num = be64toh(block->index);
    memcpy(request.hash, hash, 32);

    memcpy(rio_buf, &request, PEER_REQUEST_HEADER_SIZE);
    Rio_writen(peer_socket, rio_buf, PEER_REQUEST_HEADER_SIZE);

    Rio_readnb(&rio, rio_buf, buffer_size);

    char reply_header[PEER_RESPONSE_HEADER_SIZE];
    memcpy(reply_header, rio_buf, PEER_RESPONSE_HEADER_SIZE);

    uint64_t msglen = be64toh(*((unsigned long long*)&reply_header[1]));

    if (msglen == 0)
    {
        Close(peer_socket);
        return;
    }

    if (reply_header[0] != 0)
    {
        char* error_buf = malloc(msglen + 1);
        if (error_buf == NULL)
        {
            printf("Tracker error %d and out-of-memory reading error\n", reply_header[0]);
            Close(peer_socket);
            return;
        }
        memset(error_buf, 0, msglen + 1);
        memcpy(error_buf, &rio_buf[PEER_RESPONSE_HEADER_SIZE], msglen);
        printf("Peer gave error: %d - %s\n", reply_header[0], error_buf);
        free(error_buf);
        Close(peer_socket);
        return;
    }

    uint8_t* shabuffer = malloc(sizeof(uint8_t) * SHA256_HASH_SIZE);

    SHA256_CTX shactx;
    sha256_init(&shactx);
    sha256_update(&shactx, &rio_buf[PEER_RESPONSE_HEADER_SIZE], msglen);
    sha256_final(&shactx, shabuffer);

    if (memcmp(shabuffer, (&block->hash)->x, SHA256_HASH_SIZE) != 0) {
        printf("Not the same hash\n");
        Close(peer_socket);
        return;
    }

    FILE* fp = fopen(output_file, "rb+");
    if (fp == 0)
    {
        printf("Failed to open destination: %s\n", output_file);
        Close(peer_socket);
        return;
    }

    fseek(fp, block->offset, SEEK_SET);
    fwrite(&rio_buf[PEER_RESPONSE_HEADER_SIZE],msglen,1,fp);

    printf("Got block %ld. Wrote from %ld to %ld\n", block->index, block->offset, block->offset+msglen-1);
    Close(peer_socket);
    fclose(fp);
}

/*
 * Get a list of peers on the network from a tracker. Note that this query is doing double duty according to
 * the protocol, and by asking for a list of peers we are also enrolling on the network ourselves.
 */
int send_tracker_request(csc_peer_t** peers, uint8_t hash[32], int command)
{
    rio_t rio;
    uint8_t rio_buf[MAX_LINE];

    int tracker_socket;

    tracker_socket = Open_clientfd(tracker_ip, tracker_port);
    Rio_readinitb(&rio, tracker_socket);

    struct RequestHeader request_header;
    memcpy(request_header.protocol, "CASC", 4);
    request_header.version = htonl(1);
    request_header.command = htonl(command);
    request_header.length = htonl(BODY_SIZE);
    memcpy(rio_buf, &request_header, HEADER_SIZE);

    struct RequestBody request_body;
    memcpy(request_body.hash, hash, 32);

    inet_aton(my_ip, &request_body.ip);
    request_body.port = be16toh(atol(my_port));
    memcpy(&rio_buf[HEADER_SIZE], &request_body, BODY_SIZE);

    Rio_writen(tracker_socket, rio_buf, MESSAGE_SIZE);

    Rio_readnb(&rio, rio_buf, MAX_LINE);

    char reply_header[REPLY_HEADER_SIZE];
    memcpy(reply_header, rio_buf, REPLY_HEADER_SIZE);

    uint32_t msglen = ntohl(*(uint32_t*)&reply_header[1]);
    if (msglen == 0)
    {
        Close(tracker_socket);
        return 0;
    }

    if (reply_header[0] != 0)
    {
        char* error_buf = malloc(msglen + 1);
        if (error_buf == NULL)
        {
            printf("Tracker error %d and out-of-memory reading error\n", reply_header[0]);
            Close(tracker_socket);
            return 0;
        }
        memset(error_buf, 0, msglen + 1);
        memcpy(error_buf, &rio_buf[REPLY_HEADER_SIZE], msglen); // Fixed by Rune
        printf("Tracker gave error: %d - %s\n", reply_header[0], error_buf);
        free(error_buf);
        Close(tracker_socket);
        return 0;
    }

    if (msglen % 12 != 0)
    {
        printf("LIST response from tracker was length %u but should be evenly divisible by 12\n", msglen);
        Close(tracker_socket);
        return 0;
    }
    int peercount = msglen/12;
    *peers = malloc(peercount * sizeof(csc_peer_t));

    for (int i = 0;i<peercount;i++) {
        csc_peer_t peer;
        uint8_t* peer_data = &rio_buf[REPLY_HEADER_SIZE + 12*i];
        sprintf(peer.ip, "%u.%u.%u.%u", peer_data[0], peer_data[1], peer_data[2], peer_data[3]);
        sprintf(peer.port, "%u", be16toh(*((uint16_t*)&peer_data[4])));

        (*peers)[i] = peer;
    }
    Close(tracker_socket);
    return peercount;
}

void service_block_request(void* arg) {
    block_request_t* request = (block_request_t*)arg;
    printf("servicing block request.\n");

    char request_header[32];
    memcpy(request_header, request->request, 32);

    if (memcmp(request_header, "CASCADE1", 8) != 0) {
        char response[9];
        response[0] = 4;
        for (int j = 1 ; j < 9; j++) {
            response[j] = 0;
        }
        Rio_writen(request->socket,&response,9);
        close(request->socket);
        return;
    }

    for (int i = 8;i<16;i++) {
        if ((int)request_header[i] != 0) {
            char response[9];
            response[0] = 4;
            for (int j = 1 ; j < 9; j++) {
                response[j] = 0;
            }
            Rio_writen(request->socket,&response,9);
            close(request->socket);
            return;
        }
    }

    uint64_t block_number = be64toh(*((unsigned long long*)&request_header[24]));

    unsigned char hash[32];
    memcpy(hash, &(request->request[32]), 32);
    csc_file_t* casc_file = NULL;

    for (int i = 0; i < cascade_amount; i++){
        if (memcmp(cascade_files[i]->cascadehash,hash,32) == 0) {
            casc_file = cascade_files[i];
            break;
        }
    }

    if (casc_file == NULL) {
        char response[9];
        response[0] = 1;
        for (int j = 1 ; j < 9; j++) {
            response[j] = 0;
        }
        Rio_writen(request->socket,&response,9);
        close(request->socket);
        return;
    }

    if (block_number >= casc_file->blockcount) {
        char response[9];
        response[0] = 3;
        for (int j = 1 ; j < 9; j++) {
            response[j] = 0;
        }
        Rio_writen(request->socket,&response,9);
        close(request->socket);
        return;
    }

    csc_block_t* block = (&casc_file->blocks[block_number]);

    pthread_mutex_lock(&casc_file->mutex);

    if (!block->completed) {
        char response[9];
        response[0] = 2;
        for (int j = 1 ; j < 9; j++) {
            response[j] = 0;
        }
        Rio_writen(request->socket,&response,9);
        pthread_mutex_unlock(&casc_file->mutex);
        close(request->socket);
        return;
    }

    FILE* fp = fopen(casc_file->outputfile, "rb+");
    fseek(fp, block->offset, SEEK_SET);
    char buffer[block->length];
    fread(&buffer,1,block->length,fp);
    fclose(fp);
    pthread_mutex_unlock(&casc_file->mutex);
    char response[9 + block->length];
    response[0] = 0;
    char* block_length = be64toh(block->length);
    memcpy(&response[1],&block_length,8);
    memcpy(&response[9],buffer,block->length);

    Rio_writen(request->socket, &response, 9+block->length);

    close(request->socket);

}

void server_mt() {
    char rio_buf[64];

    int socket = open_listenfd(my_port);
    struct sockaddr* peer_address = malloc(sizeof(struct sockaddr));
    int address_length;

    while (1) {
        rio_t rio;
        int new_socket = Accept(socket, peer_address, &address_length);
        Rio_readinitb(&rio, new_socket);
        Rio_readnb(&rio, rio_buf, 64);

        pthread_t request_handler;
        block_request_t* request = malloc(sizeof(block_request_t));
        memcpy(request->request,rio_buf,64);
        request->peer_address = peer_address;
        request->rio = rio;
        request->socket = new_socket;
        
        pthread_create(&request_handler, NULL, service_block_request, (void*)request);
        //pthread_join(&request_handler, NULL);
    }
}

void client_mt(void* arg) {
    csc_file_t* casc_file = (csc_file_t*)arg;
    printf("Starting client for %s.\n", casc_file->outputfile);
    

    csc_block_t** queue = malloc(casc_file->blockcount * sizeof(csc_block_t*));

    while (!casc_file->completed){
        while (casc_file->peercount == 0) {
            casc_file->peercount = send_tracker_request(&(casc_file->peers), casc_file->cascadehash, 1);
            if (casc_file->peercount == 0)
            {
                printf("No peers were found. Will try again in %d seconds\n", PEER_REQUEST_DELAY);
                fflush(stdout);
                sleep(PEER_REQUEST_DELAY);
            }
        }
        printf("Found %d peer(s)\n", casc_file->peercount);

        int uncomp_count = 0;
        for (unsigned long long i = 0;i<casc_file->blockcount;i++) {
            if ((&casc_file->blocks[i])->completed == 0) {
                queue[uncomp_count] = &casc_file->blocks[i];
                uncomp_count++;
            }
        }

        csc_peer_t peer = (casc_file->peers[0]);
        // Get a good peer if one is available
        for (int i=0; i<casc_file->peercount; i++)
        {
            if (casc_file->peers[i].good)
            {
                peer = (casc_file->peers[i]);
            }
        }

        for (int i=0; i<uncomp_count; i++)
        {
            pthread_mutex_lock(&casc_file->mutex);
            get_block(queue[i], peer, casc_file->cascadehash, casc_file->outputfile);
            pthread_mutex_unlock(&casc_file->mutex);
        }

        printf("\n");
        pthread_mutex_lock(&casc_file->mutex);
        casc_file = check_blocks(casc_file);
        pthread_mutex_unlock(&casc_file->mutex);

        if (!casc_file->completed) {
            send_tracker_request(&(casc_file->peers), casc_file->cascadehash,1);
        }

    }

    free(casc_file->peers);
    free(queue);
    printf("Fully downloaded %s\n",casc_file->outputfile);
}

void start_peer(char* cascade_file){
    printf("Managing download only for: %s\n", cascade_file);
    if (access(cascade_file, F_OK ) != 0 )
    {
        fprintf(stderr, ">> File %s does not exist\n", cascade_file);
        exit(EXIT_FAILURE);
    }

    csc_file_t *casc_file;
    casc_file = csc_parse_file(cascade_file);

    cascade_files[cascade_amount] = casc_file;
    cascade_amount++;

    // start client and server on separate threads
    pthread_t client;


    // subscribe to peer
    casc_file->peercount = send_tracker_request(&(casc_file->peers), casc_file->cascadehash, 2);


    pthread_create(&client, NULL, client_mt, (void*)casc_file);
}

/*
 * The entry point for the code. Parses command line arguments and starts up the appropriate peer code.
 */
int main(int argc, char **argv)
{
    if (argc != MAIN_ARGNUM + 1)
    {
        fprintf(stderr, "Usage: %s <cascade file(s)> <tracker server ip> <tracker server port> <peer ip> <peer port>.\n", argv[0]);
        exit(EXIT_FAILURE);
    }
    else if (!is_valid_ip(argv[2]))
    {
        fprintf(stderr, ">> Invalid tracker IP: %s\n", argv[2]);
        exit(EXIT_FAILURE);
    }
    else if (!is_valid_port(argv[3]))
    {
        fprintf(stderr, ">> Invalid tracker port: %s\n", argv[3]);
        exit(EXIT_FAILURE);
    }
    else if (!is_valid_ip(argv[4]))
    {
        fprintf(stderr, ">> Invalid peer IP: %s\n", argv[4]);
        exit(EXIT_FAILURE);
    }
    else if (!is_valid_port(argv[5]))
    {
        fprintf(stderr, ">> Invalid peer port: %s\n", argv[5]);
        exit(EXIT_FAILURE);
    }

    snprintf(tracker_ip,   IP_LEN,   argv[2]);
    snprintf(tracker_port, PORT_LEN, argv[3]);
    snprintf(my_ip,   IP_LEN,   argv[4]);
    snprintf(my_port, PORT_LEN, argv[5]);

    char cas_str[strlen(argv[1])];
    snprintf(cas_str, strlen(argv[1])+1, argv[1]);
    char delim[] = ":";

    int casc_count = count_occurences(argv[1], ':') + 1;
    char *cascade_files[casc_count];

    char *ptr = strtok(cas_str, delim);
    int i = 0;

    while (ptr != NULL)
    {
        if (strstr(ptr, ".cascade") != NULL)
        {
            cascade_files[i++] = ptr;
            ptr = strtok(NULL, delim);
        }
        else
        {
            printf("Abort on %s\n", ptr);
            fprintf(stderr, ">> Invalid cascade file: %s\n", ptr);
            exit(EXIT_FAILURE);
        }
    }

    pthread_t server;
    pthread_create(&server, NULL, server_mt, NULL);

    for (int j=0; j<casc_count; j++)
    {
        start_peer(cascade_files[j]);
    }

    pthread_join(server, NULL);

    exit(EXIT_SUCCESS);
}