#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 <sys/wait.h>

#include "socket_wrapper.h"

#ifndef DEFAULT_MAX_LISTEN_SOCKET
static const int MAX_LISTEN_SOCKET = 16;
#else
static const int MAX_LISTEN_SOCKET = DEFAULT_MAX_LISTEN_SOCKET;
#endif

#ifdef USE_SENDFILE
#include <sys/sendfile.h>
#ifndef DEFAULT_SEND_FILE_CHUNK_SIZE
const size_t SEND_FILE_CHUNK_SIZE = 0x100000; /*1MB*/
#else
const size_t SEND_FILE_CHUNK_SIZE = DEFAULT_SEND_FILE_CHUNK_SIZE; /*1MB*/
#endif
#endif
#ifndef DEFAULT_SERVER_PORT
static const in_port_t SERVER_PORT = 9091;
#else
static const in_port_t SERVER_PORT = DEFAULT_SERVER_PORT;
#endif
#ifndef DEFAULT_MAX_PATH_SIZE
/*0 < x < MAX_PATH_SIZE*/
static const uint16_t MAX_PATH_SIZE = 256;
#else
static const uint16_t MAX_PATH_SIZE = DEFAULT_MAX_PATH_SIZE;
#endif
#ifndef DEFAULT_TIMEOUT
static const int TIMEOUT = 5;
#else
static const int TIMEOUT = DEFAULT_TIMEOUT;
#endif
#ifndef DEFAULT_RESPONSE_REQUEST
static const int RESPONSE_REQUEST = 3;
#else
static const int RESPONSE_REQUEST = DEFAULT_RESPONSE_REQUEST;
#endif

#ifdef USE_TRACE
#include <sys/time.h>
#include <time.h>
#include "timerhelper.h"

enum{
    #ifndef DEFAULT_TOP_TRACE_TIMER_ID
    Top_Trace_Timer_ID = CLOCK_REALTIME,
    #else
    Top_Trace_Timer_ID = DEFAULT_TOP_TRACE_TIMER_ID,
    #endif
    #ifndef DEFAULT_BOTTOM_TRACE_TIMER_ID
    Bottom_Trace_Timer_ID = CLOCK_THREAD_CPUTIME_ID
    #else
    Bottom_Trace_Timer_ID = DEFAULT_BOTTOM_TRACE_TIMER_ID
    #endif
};

static inline void report_resolution()
{
    struct timespec top_res,bottom_res;
    clock_getres(Top_Trace_Timer_ID,&top_res);
    clock_getres(Bottom_Trace_Timer_ID,&bottom_res);
    fprintf(stderr,"top res: %ld, bottom res: %ld\n",top_res.tv_nsec,bottom_res.tv_nsec);
}
#endif

/*========
 *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;
}
/** print help message
 * arg `n`: executable name
 */
const char * help(const char * n){
    const char * msg = "USASE : %s [Option] ...\n"
    "Options and arguments: \n"
    "-p port\t:set to port binding. couldn't set to 0\n"
    "-h\t:print help message.\n";
    printf(msg,n);
    return msg;
}
/** parse arguments. 
 * if return 0, success. otherwise arguments are invalid format.*/
int parse_args(int argc,const char * argv[] , in_port_t * port){
    int pos = 1;
    const char * opt;
    while (pos < argc)
    {
        opt = argv[pos++];
        if (strcmp(opt,"-h") == 0 || strcmp(opt,"--help") == 0)
        {
            help(argv[0]);
            return 2;
        }
        else if(strcmp(opt,"-p") == 0 || strcmp(opt,"--port") == 0){
            if (pos < argc){
                const char * value = argv[pos++];
                *port = atoi(value);
                if (port == 0){ // either not number or zero 
                    fprintf(stderr,"port argument is either not number or zero\n");
                    return 2;
                }
            }
            else{
                fprintf(stderr,"need argument\n"); 
                return 2; //failed to find argument.
            }
        }
    }
    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;
    int i;
    in_port_t binding_port_number = SERVER_PORT;
    if (argc > 1){
        int d = parse_args(argc,argv,&binding_port_number);
        if(d != 0 ) return d;
    }
    #ifdef USE_TRACE
    report_resolution();
    #endif
    sock = socket(AF_INET,SOCK_STREAM,0);
    atexit(safe_exit);
    if(sock < 0){
        perror("sock create fail");
        return 1;
    }
    else {
        int option = 1;
        if(setsockopt(sock,SOL_SOCKET,SO_REUSEADDR,&option,sizeof(option)) < 0){
            perror("setsockopt");
        }
    }
    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(binding_port_number);

    if(bind(sock, (struct sockaddr *)&addr,sizeof(addr)) < 0){
        perror("bind failed");
        return 1;
    } else {
        char ip_buf[INET_ADDRSTRLEN];
        const char * msg = inet_ntop(AF_INET,&addr.sin_addr,ip_buf,sizeof(ip_buf));
        assert(msg != NULL);
        fprintf(stderr,"server bind on %s:%d\n",msg ,binding_port_number);
    }
    if(listen(sock,MAX_LISTEN_SOCKET) < 0){
        perror("listen failed");
        return 1;
    }

    for (i = 0; i < RESPONSE_REQUEST; i++)
    {
        int fd, pid;
        char ip_buf[INET_ADDRSTRLEN];
        const char * msg;
        int retval = 0;
    #ifdef USE_TRACE
        struct timespec ts_top_begin,ts_top_end, ts_bottom_begin, ts_bottom_end;
    #endif
        if((csock = accept(sock, (struct sockaddr *)&client_addr,&client_addr_len)) < 0){
            free(buf);
            perror("accept error");
            return 1;
        }
        msg = inet_ntop(AF_INET,&client_addr.sin_addr,ip_buf,sizeof(ip_buf));
    #ifdef USE_TRACE
        clock_gettime(Top_Trace_Timer_ID,&ts_top_begin);
    #endif
        fprintf(stdout,"Connected on : %s:%d\n",msg == NULL ? "(null)" : msg , ntohs(client_addr.sin_port));
        pid = fork();
        if(pid == 0){
    #ifdef USE_TRACE
            clock_gettime(Top_Trace_Timer_ID,&ts_top_end);
            clock_gettime(Bottom_Trace_Timer_ID,&ts_bottom_begin);
    #endif
            if((fd = read_request(csock,buf,bufsize)) > 0){
                retval = send_response(csock,fd,buf,bufsize);
                close(fd);
            }
            else retval = fd;
            if(close(csock) < 0)
                perror("csock close error");
    #ifdef USE_TRACE
            clock_gettime(Bottom_Trace_Timer_ID,&ts_bottom_end);
            struct timespec tophalf = timespec_sub(ts_top_end,ts_top_begin);
            struct timespec bottomhalf = timespec_sub(ts_bottom_end,ts_bottom_begin);
            fprintf(stderr,"top: %ld ns, bottom: %ld ns\n",tophalf.tv_nsec,bottomhalf.tv_nsec);
    #endif
            free(buf);
            return retval;
        }
    }
    for (i = 0; i < RESPONSE_REQUEST; i++)
    {
        int retval;
        int pid = wait(&retval);
        printf("[%d] %d: %d\n",i,pid,retval);
    }
    
    free(buf);
    return 0;
}