#include <sys/socket.h>

#include <netinet/in.h>

#include <stdio.h>

#include <sys/types.h>

#include <unistd.h>

#include <arpa/inet.h>

#include <string.h>

#include <netdb.h>

#include <fcntl.h>

#include <signal.h>

#define BUFLEN 512

#define NPACK 10

#define PORT 9930

#define SRV_IP "127.0.0.1"

#define LENGTH 1000

// header : add ip addr + port + filelength + flag;

// agent: change destination

struct sockaddr_in si_other;

int slen = 0, nameLength = 0, fin = -1, ackType = -1, expectNum = 0, resend = 0;

void diep(char *a){

perror(a);

//exit(1);

return ;

}

void sighandler(int signo){

resend = 1;

}

unsigned char * encode_int(unsigned char *buffer, int value);

unsigned char * encode_char(unsigned char *buffer, char *value);

unsigned char * encode_struct(unsigned char *buffer, int a, char *b);

unsigned char * encode_data_struct(unsigned char *buffer, int length, int sequence, char* data);

void send_connection_packet(char *filename, int s);

void send_data_packet(char *fileName, int s);

void send_end_packet(int s);

int decode_ack(char *ack);

unsigned int decode_int(unsigned char *buffer);

int main(int argc, char** argv){

int s, i;

slen = sizeof(si_other);

char fileName[1000];

struct sigaction act;

act.sa_handler = sighandler;

act.sa_flags = 0;

strcpy(fileName, argv[1]);

nameLength = strlen(fileName);

if(argc != 2)

diep("please enter filename");

if(sigaction(SIGALRM, &act, 0) == -1)

perror("sigaction\n");

if((s=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1)

diep("socket");

memset((char *) &si_other, 0, sizeof(si_other));

si_other.sin_family = AF_INET;

si_other.sin_port = htons(PORT);

if(inet_aton(SRV_IP, &si_other.sin_addr) == 0){

fprintf(stderr, "inet_aton() failed\n");

exit(1);

}

while(fin < 0){

if(ackType == -1)

send_connection_packet(fileName, s);

else if(ackType == 1)

send_data_packet(fileName, s);

else

send_end_packet(s);

}

printf("end the connection\n");

close(s);

return 0;

}

unsigned char * encode_int(unsigned char *buffer, int value){

printf("encode int\n");

int i = 0;

for(i = 0;i < 4;i++){

buffer[i] = value >> (24 - 8 * i);

}

return buffer + 4;

}

unsigned char * encode_char(unsigned char *buffer, char *value){

printf("encode char:\n");

int i = 0;

for(i = 0;i < LENGTH; i++){

buffer[i] = value[i];

}

return buffer + LENGTH;

}

/*void send_packet(int s, int a, char b){

unsigned char buf[32];

unsigned char *ptr;

char ack[4];

ack[3] = '\0';

ptr = encode_strcut(buf, a, b);

if(sendto(s, buf, ptr - buf, 0, &si_other, slen) == -1)

diep("sendto()");

if(recvfrom(s, ack, 3, 0, &si_other, &slen) == -1)

diep("recvfrom");

printf("ack: %s\n", ack);

}*/

unsigned char * encode_struct(unsigned char *buffer, int a, char *b){

buffer = encode_int(buffer, a);

buffer = encode_char(buffer, b);

return buffer;

}

unsigned char * encode_data_struct(unsigned char *buffer, int length, int sequence, char *data){

buffer = encode_int(buffer, sequence);

buffer = encode_int(buffer, length);

buffer = encode_char(buffer, data);

return buffer;

}

void send_connection_packet(char *fileName, int s){

// packet style: file name + file size

// ack style: num

char readBuffer[1000],ack[2];

int f, fileLength = 0, i, j;

unsigned char buf[LENGTH + 8], *ptr;

ack[1] = '\0';

if((f = open(fileName, O_RDONLY)) == -1)

diep("open file failed");

while((i = read(f, readBuffer, 1000)) > 0){

fileLength += i;

}

for(j = 0;j < strlen(fileName); j++)

readBuffer[j] = fileName[j];

ptr = encode_struct(buf, fileLength, readBuffer);

if(sendto(s, buf, ptr - buf, 0, &si_other, slen) == -1)

diep("connection packet error\n");

while(recvfrom(s, ack, 1, 0, &si_other, &slen) < 0){

sendto(s, buf, ptr - buf, 0, &si_other, slen);

}

printf("the recv ack is : %s\n", ack);

ackType = 1;

expectNum = 1;

}

void send_end_packet(int s){

printf("send_end_packet\n");

char end[2], rec[2];

end[0] = '1';

end[1] = '\0';

rec[1] = '\0';

if(sendto(s, end, 1, 0, &si_other, slen) == -1)

diep("end packet error\n");

while(recvfrom(s, rec, 1, 0, &si_other, &slen) < 0){

if(sendto(s, end, 1, 0, &si_other, slen) == -1)

diep("end packet error\n");

}

if(rec[0] != '1')

diep("wrong fin\n");

fin = 1;

}

void send_data_packet(char *fileName, int s){

//packet style: sequence num + length + data

printf("send_data_packet\n");

int f, i, fileLength = 0;

char readBuffer[LENGTH + 1], ack[5];

unsigned char buf[LENGTH + 8], *ptr;

ack[4] = '\0';

if(expectNum < 1) diep("can not start sending data packet \n");

if((f = open(fileName, O_RDONLY)) == -1) diep("can not open the file when sending data packets\n");

while((i = read(f, readBuffer, LENGTH)) > 0){

readBuffer[i] = '\0';

printf("reading: %s\n", readBuffer);

ptr = encode_data_struct(buf, i, expectNum, readBuffer);

expectNum += i;

fileLength += i;

//printf("ready recv\n");

while(1){ // small loop to do congestion control

if(sendto(s, buf, ptr - buf, 0, &si_other, slen) < 0)

diep("send error\n");

alarm(5);

//recvfrom(s, ack, sizeof(char) * 4, 0, &si_other, &slen) < 0 || expectNum != decode_ack(ack)

if(recvfrom(s, ack, sizeof(char) * 4, 0, &si_other, &slen) >= 0){

if(expectNum == decode_ack(ack)){

alarm(0);

break;

}

}

printf("recv error\n");

}

}

if(expectNum - 1 != fileLength) diep("data sending error\n");

else ackType = 2;

}

int decode_ack(char *ack){

//printf("decode_ack:%d\n", strlen(ack));

if(ack != NULL){

printf("expect sequence: %d\n", decode_int(ack));

return decode_int(ack);

}

return -1;

}

unsigned int decode_int(unsigned char *buffer){

unsigned int ans = 0;

int i = 0;

printf("%s\n", "decode int");

for(i = 0; i < 4;i++){

ans += buffer[i];

if(i != 3) ans = ans << 8;

}

return ans;

}