#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>
#include <string.h>
#include <arpa/inet.h>
#include <errno.h>
#include <sys/stat.h>
#include <signal.h>
#include <assert.h>
#include <fcntl.h>
#include "socket_wrapper.h"

/*========
 *Operation
 *========*/

/**
 * send user error message
 * 80 character limit
 * thread safe
*/
int send_fail(int sock,const char * msg){
    struct TransferResult res;
    res.res = RES_USR_ERR;
    res.file_size = 0;
    res.err_number = 0;
    res.error_msg_size = strlen(msg);
    //os will be combining if tcp_autocorking emabled.
    if(send(sock,&res,sizeof(res),0) < 0){
        perror("error msg send");
        return -1;
    }
    if (send(sock,msg,res.error_msg_size,0) < 0){
        perror("error msg send");
        return -1;
    }
    return 0;
}
/**
 * send errno to client
 * thread safe
 */
int send_errno(int sock){
    struct TransferResult r;
    r.res = RES_ERR;
    r.err_number = errno;
    r.file_size = 0;
    r.error_msg_size = 0;
    if(send(sock,&r,sizeof(r),0)){
        perror("errno send");
        return -1;
    }
    return 0;
}
/**
 * return fd, if success. otherwise, return -1.
 * thread safe
*/
int read_request(int sock,uint8_t * buf,size_t bufsize){
    struct ReadOp p;
    int fd;
    ssize_t n = recv_until_byte(sock,&p,sizeof(p),TIMEOUT);
    if (n < 0){
        if (n == -2) fprintf(stderr,"timeout!");
        else perror("receive fail"); 
        return -1;
    }
    if(bufsize <= ((size_t)p.file_url_size) + sizeof(p) + 1){
        send_fail(sock,"buffer overflow");
        return -1;
    }
    else if(p.file_url_size + 1 > MAX_PATH_SIZE){
        send_fail(sock,"max path fail");
        return -1;
    }
    else if(p.file_url_size == 0){
        send_fail(sock,"filename zero fail");
        return -1;
    }
    n = recv_until_byte(sock,buf,p.file_url_size,TIMEOUT);
    buf[p.file_url_size] = '\0';    //truncate
    fprintf(stdout,"str size: %d, request %s\n",p.file_url_size,buf);
    if(strchr((char *)buf,'/') != NULL){
        send_fail(sock,"Illegal character /");
        return -1;
    }
    fd = open((char *)buf,O_RDONLY);
    if(fd < 0){
        send_errno(sock);
        close(fd);
        return -1;
    }
    return fd;
}
/**
 * send response to client
 * thread safe
*/
int send_response(int sock,int fd, uint8_t * buf, size_t bufsize){
    struct TransferResult r;
    struct stat st;
    off_t offset = 0;
    ssize_t readed = 0;
    r.res = RES_OK;
    r.err_number = 0;
    r.error_msg_size = 0;
    if(fstat(fd,&st) < 0){
        return send_errno(sock);
    }
    if(S_ISDIR(st.st_mode)){
        return send_fail(sock,"is a directory");
    }
    r.file_size = st.st_size;
    if(send(sock,&r,sizeof(r),0)<0){
        perror("send fail");
        return -1;
    }
#ifdef USE_SENDFILE
    while (r.file_size != offset)
    {
        size_t count = SEND_FILE_CHUNK_SIZE < (r.file_size - offset) ? SEND_FILE_CHUNK_SIZE : (r.file_size - offset);
        if((readed = sendfile(sock,fd,&offset,count)) < 0){
            perror("send file fail");
            return -1;
        }
    }
#else
    while (offset < r.file_size)
    {
        readed = bufsize < (r.file_size - offset) ? bufsize : r.file_size - offset;
        if(read(fd,buf,readed)<0){
            perror("send response read fail");
            return -1;
        }
        if(send(sock,buf,readed,0)<0){
            perror("send response send fail");
            return -1;
        }
        offset += readed;
    }
    
#endif
    return 0;
}
static int sock;
void safe_exit(){
    close(sock);
}
int main(int argc, const char *argv[]){
    uint8_t * buf;
    struct sockaddr_in addr;
    struct sockaddr_in client_addr;
    socklen_t client_addr_len = sizeof(client_addr);
    int csock;
    int bufsize;
    sock = socket(AF_INET,SOCK_STREAM,0);
    atexit(safe_exit);
    if(sock < 0){
        perror("sock create fail");
        return 1;
    }
    bufsize = getBufferSizeFrom(sock);
    buf = malloc(bufsize * sizeof(*buf));
    if (buf == NULL){
        fprintf(stderr,"lack of memory");
        return 1;
    }
    
    addr.sin_addr.s_addr = htonl(INADDR_ANY); /*0.0.0.0 모든 네트워크 인터페이스에 묶임.*/
    addr.sin_family = AF_INET;
    addr.sin_port = htons(SERVER_PORT);

    if(bind(sock, (struct sockaddr *)&addr,sizeof(addr)) < 0){
        perror("bind failed");
        return 1;
    }
    fprintf(stderr,"server bind on %s:%d\n",inet_ntoa(addr.sin_addr),SERVER_PORT);

    if(listen(sock,1) < 0){
        perror("listen failed");
        return 1;
    }

    while ((csock = accept(sock, (struct sockaddr *)&client_addr,&client_addr_len)) >= 0)
    {
        int fd;
        /*inet_ntoa is not reentrant function. do not use it in signal handler.*/
        printf("Connect : %s\n",(inet_ntoa(client_addr.sin_addr)));
        if((fd = read_request(csock,buf,bufsize)) > 0){
            send_response(csock,fd,buf,bufsize);
            close(fd);
        }

        if(close(csock) < 0)
            perror("csock close error");

    }
    free(buf);
    perror("accept error");
    return 1;
}