// This is the main file of the Dazibao project. It represents the node, and
// handles all of the main logic, including the network connexions.
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>
#include <time.h>

#include "tlv.h"
#include "node.h"

/* ----  Fonctions utilitaires  ---- */

// Get list length
int len_list(list *l) {
	int len = 0;
	list *tmp = l;

	while(tmp != NULL) {
		tmp = tmp->next;
		len++;
	}

	return len;
}

// Get a random neighbour
neighbour_peer *get_random_neighbour() {
	// Get a random number
    time_t t;
    srand((unsigned) time(&t));
    int n = rand() % len_list(neighbour_list);

    // Get nth neighbour
    list *tmp = neighbour_list;

    for(int i=0; i<n; i++) {
    	tmp = tmp->next;
    }

    return (neighbour_peer*) tmp->data;
}

/* ---- Fin fonctions utilitaires ---- */

int send_tlv(struct tlv tlv_to_send, int tlv_type, struct sockaddr_in6 * dest_list[], int dest_list_size, int sock_num){
	debug_print("Building packet to send a TLV.");

	// We first need to build the packet,
	char packet_buff[1024];
	struct packet pack;

	pack.magic = 95;
	pack.version = 1;
	if(sizeof(tlv_to_send) > 1020){
		debug_print("Unable to send TLV, the size is bigger than 1020 bits.");
		return -1;
	} else {
		pack.length = sizeof(tlv_to_send);
		strcpy(pack.body, (char) tlv_to_send);
	}

	// Casting the struct to a buffer.
	packet_buff = (char *) pack;

	debug_print("Packet has been built.");

    // Vectorized buffer
    struct iovec vec_buff = { .iov_len = sizeof(packet_buff), .iov_base = packet_buff };

	int error_while_sending = 0;

	// For every dest
	for (size_t i = 0; i < dest_list_size; i++) {
		// Creating the struct to send out with sendmsg
		struct msghdr packet_tlv_send_out = {
			.msg_name = &dest_list[i],
			.msg_namelen = sizeof(dest_list[i]),
			.msg_iov = &vec_buff,
			.msg_iovlen = 1 // We have only one iovec buffer. But if we had 2, we would write 2.
		};

		response_code = sendmsg((int) sock_num, &packet_tlv_send_out, 0);
		if (response_code < 0) {
			debug_print("Unable to send out the packet to peer %i", i);
			error_while_sending = 1;
			continue;
		} else if (response_code < sizeof(packet_tlv_send_out)) {
			debug_print("Sent out only part of the packet.");
			error_while_sending = 1;
			continue;
		} else {
			debug_print("Send out packet to peer %i", i);
		}
	}

	if (error_while_sending == 1) {
		debug_print("Error occured while sending out a packet.");
		return -1;
	} else {
		return 0;
	}
}

// We need to make sure the TLV announces a length that will no go onto
// another tlv, as we might end up reading bullshit.
int validate_tlv(char *data, int pos, short packet_len){
    char type = data[pos];

    // Nothing to do in this case
    if(type == 0)
        return 0;

    // Check that we can read a length
    if(pos + 1 >= packet_len)
        return -1;

    unsigned char tlv_len = data[pos+1];

    // Check that the tlv does not exceed the packet length
    if(pos + length >= packet_len)
        return -1;

    // Returns the type of the tlv or -1 if something went wrong
    switch(type) {
        case 1:
            return 1;
        case 2:
            if(tlv_len != LEN_NEIGHBOUR_REQ) return -1;
            return 2;
        case 3:
            if(tlv_len != LEN_NEIGHBOUR) return -1;
            return 3;
        case 4:
            if(tlv_len != LEN_NETWORK_HASH) return -1;
            return 4;
        case 5:
            if(tlv_len != LEN_NETWORK_STATE_REQ) return -1;
            return 5;
        case 6:
            if(tlv_len != LEN_NODE_HASH) return -1;
            return 6;
        case 7:
            if(tlv_len != LEN_NODE_STATE_REQ) return -1;
            return 7;
        case 8:
            if(tlv_len < MIN_LEN_NODE_STATE || tlv_len > MAX_LEN_NODE_STATE) return -1;
            return 8;
        case 9:
            return 9;
        default:
            return -1;
    }
}

// For every packet recivied,
// then we make sure it's conform
// We then extract the data from it to make it easy to work with
int check_header(char * req[], int buffer_size, struct packet * packet_to_return){

    packet * packet_to_return = (packet*) req;

    // We need to check a few things ;
    // The first byte must be worth 95,
    if (packet_to_return->magic != 95) {
        perror(">> The magic number of the packet is no good.");
        return -1;
    }

    // The second byte must be worth 1,
    if (packet_to_return->version != 1) {
        perror(">> The version number of the packet is no good.");
        return -1;
    }

    if (packet_to_return.length + 4 > buffer_size  ) {
        perror(">> The packet length is bigger than the UDP datagram, which is not possible with the current laws of physics.");
        return -1;
    }

    return 0;
}

// If the sender is not in the neighbourhood, and we have 15 neighbours, we
// ignore the packet. Otherwise, we add him to the neighbourhood, marked as
// temporary.
int update_neighbours(){
    return 0;
};

// We then look at the differents TLVs in the packet.
void work_with_tlvs(char *data, short packet_len, struct sockaddr_in6 sender){
    int pos = 0;
    unsigned char tlv_len;
    tlv tmp_tlv;

    while(pos < packet_len) {
        switch(validate_tlv(data, pos, packet_len)) {
            case 0:
                // We received a padding tlv so it is ignored
                pos += 1;
                break;
            case 1:
                // We received a padding tlv so it is ignored
                tlv_len = data[pos+1];
                pos += tlv_len + 2;
                break;
            case 2:
                // We received a neighbour request so a random neighbor tlv has to be sent
                tlv_len = data[pos+1];
                pos += tlv_len + 2;

                // Send a neighbour tlv
                neighbour_peer *random = get_random_neighbour();
                build_neighbour(&tmp_tlv, random->ip, random->port);

                // NOT FINISHED - What packet is it added to?
                add_tlv(packet, &tmp_tlv, 3);
                break;
            case 3:
                // We received a neighbour tlv so a tlv network hash is sent to that address
            	neighbour* cur_tlv = ((neighbour*) data) + pos;
            	struct in6_addr ip = cur_tlv->ip;
				short port = cur_tlv->port;

                tlv_len = data[pos+1];
                pos += tlv_len + 2;

                // Build network hash
                unsigned char hash[16];
                hash_network(neighbour_list, hash);
                build_network_hash(&tmp_tlv, hash);

                // NOT FINISHED - What packet is it added to?
                add_tlv(packet, &tmp_tlv, 4);
                break;
            case 4:
                // We reveived a network hash tlv so
                tlv_len = data[pos+1];
                pos += tlv_len +2;

                // NOT FINISHED - Where is network_hash?
                build_neighbour(&tmp_tlv, network_hash);
                // NOT FINISHED - What packet is it added to?
                add_tlv(packet, &tmp_tlv, 4);
                break;
            case 5:
                // We received a network state request tlv so a series of tlv node hash have to be sent for each data known
                pos += 2;

                // NOT FINISHED - for each known data
                list *tmp_list = data_list;
                pub_data *tmp_data;

                while(tmp_list != NULL) {
                	tmp_data = (pub_data*) tmp_list->data;
                	build_node_hash(&tmp_tlv, tmp_data->id, tmp_data->seqno);
                }

                break;
            case 6:
                // We received a node hash tlv
                break;
            case 7:
                // We received a node state request tlv
                break;
            case 8:
                // We received a node state tlv
                break;
            case 9:
                // We received a warning tlv so it's message is printed
                break;
            default:
                return ;
        }
    }
}

// We listen forever for new paquets;
void listen_for_packets(){

    // Create new socket for UDP
    int s = socket(AF_INET6, SOCK_DGRAM, 0);

    if(s < 0) {
        perror(">> Error, cannot create socket.");
        perror(">> Exiting...");
        exit(1);
    }

    struct sockaddr_in6 server;
    memset(&server, 0, sizeof(server));

    server.sin6_family = AF_INET6;
    server.sin6_port = htons(LISTEN_PORT);
    int rc = bind(s, (struct sockaddr*)&server, sizeof(server));
    if(rc < 0) {
        perror(">> Error, cannot bind socket to choosen port.");
        perror(">> Exiting...");
        exit(1);
    }

    // A paquet has at most a length of 1024 bytes
    char req[1024];
    struct sockaddr_in6 sender;
    struct iovec io = { .iov_len = 1024, .iov_base = req };
    struct msghdr msg_to_receive = {
        .msg_name = &sender,
        .msg_namelen = sizeof(sender),
        .msg_iov = &io,
        .msg_iovlen = 1
    };
    while(1){
        memset(req, '\0', 1024);

        rc = recvmsg(s, &msg_to_receive, 0);
        if(rc < 0) {
            perror(">> Error while receiving a new datagram.");
            perror(">> Ignoring, continuing...");
            continue;
        }

        printf(">> New paquet received :\n");
        printf("%s\n", req);

        // TODO : Here, we need to fork.

        // We verify the received packet is well formated,
        // and we return it in the struct designed to work with it.
        struct packet * formated_rec_datagram;
        if(check_header(&req, 1024, formated_rec_datagram) < 0){
            perror(">> Error while checking the header, aborting this packet, by choice, and conviction.");
            continue;
        }

        // TODO : Add the neighbour check here.

        // struct tlv_list received_tlvs;
        // if (validate_tlvs(formated_rec_datagram) < 0)
        int nbr_success_tlv = work_with_tlvs(formated_rec_datagram, &req, sender);
        if (nbr_success_tlv < 0){
            perror(">> Error while treating the TLVs of the packet.");
            printf(">> Managed to deal with %i TLVs\n", -nbr_success_tlv );
        } else {
            printf(">> Done working with the TLVs of the packet, listenin for new packets.\n");
        }
    }
}

int main(int argc, const char *argv[]) {
    int cont = 1;

    while(cont){

        // We create the neighbourhood table
        neighbour_peer neighbour_list[NEIGHBOUR_MAX];
        // We create the message table

        // We create our own message.

        // Listen for incoming packets
        listen_for_packets();

        // This is in it's own fork.
        time_t delay = time(NULL) + 20;
        while(! (delay < time(NULL))) {
            // Theses functions are there for general book-keeping,and run in there own
            // thread, being run every 20 seconds.
            // Every 20 sec, if we have less than 5 neighbours, we ask for more peers
            // by sending out a TLV neighbour Request at a random peer.
            t_ask_for_more_peers();
            // Every 20 sec, we also check for a peer that didn't emit a new message for
            // the past 70 sec, if he's temporary, we delete him from the neighbourhood.
            t_update_neighbours();
            // We send out a TLV Network hash to get an ideal of the network state.
            t_get_network_state();
        }
    }
    return 0;
}