#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 <pthread.h>

#include "socket_wrapper.h"
#include "simple_circular_buffer.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

enum{
#ifndef DEFAULT_WORK_QUEUE_SIZE
 WORK_QUEUE_SIZE = 10,
 #else
 WORK_QUEUE_SIZE = DEFAULT_WORK_QUEUE_SIZE,
#endif
#ifndef DEFAULT_MAX_THREAD_NUMBER
 MAX_THREAD_NUMBER = 10
 #else
 MAX_THREAD_NUMBER = DEFAULT_MAX_THREAD_NUMBER
#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;
}
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;
}
/** return 0 ok. otherwise 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 0;
        }
        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,"argument is either not number or zero\n");
                    return 2;
                }
            }
            else{
                fprintf(stderr,"need argument\n"); 
                return 2; //failed to find argument.
            }
        }
    }
    return 0;
}
//============
//Simple Thread Pool
//============
typedef struct SharedState{
    //empty if less than 0
    queue_struct(int,WORK_QUEUE_SIZE) socks;
    pthread_mutex_t sock_mutex;
    pthread_cond_t ready;
    //int progress[MAX_THREAD_NUMBER];
} shared_state_t;

void init_shared_state(shared_state_t * state) {
    queue_init(&state->socks);
    pthread_mutex_init(&state->sock_mutex,NULL);
    pthread_cond_init(&state->ready,NULL);
}
//
typedef struct WorkerArgument
{
    int id;
    int bufsize;
    uint8_t * buf;

    //pthread_mutex_t * cond_mutex;
    //pthread_cond_t cond;

} worker_argument_t;

__attribute_malloc__ worker_argument_t * create_worker_argument(int id, int bufsize){
    worker_argument_t * ret = (worker_argument_t *)malloc(sizeof(worker_argument_t));
    if (ret == NULL) return ret;
    ret->id = id;
    ret->bufsize = bufsize;
    ret->buf = (uint8_t *)malloc(sizeof(*ret->buf)*bufsize);
    if(ret->buf == NULL){
        free(ret);
        ret = NULL;
    }
    return ret;
}

static shared_state_t globalState;

void * worker_proc(void * data){
    worker_argument_t * args = (worker_argument_t *)data;
    int fd, csock;
    for(;;){
        pthread_mutex_lock(&globalState.sock_mutex);
        while (queue_isempty(&globalState.socks)){
            pthread_cond_wait(&globalState.ready,&globalState.sock_mutex);
        }
        csock = dequeue(&globalState.socks);
        pthread_mutex_unlock(&globalState.sock_mutex);
        if((fd = read_request(csock,args->buf,args->bufsize)) > 0){
            send_response(csock,fd,args->buf,args->bufsize);
            close(fd);
        }

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

static pthread_t worker_threads[MAX_THREAD_NUMBER];

static int sock;
void safe_exit(){
    close(sock);
}
int main(int argc, const char *argv[]){
    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;
    }
    
    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");
        }
    }
    init_shared_state(&globalState);
    bufsize = getBufferSizeFrom(sock);
    for (i = 0; i < MAX_THREAD_NUMBER; i++) {
        worker_argument_t * args = create_worker_argument(i,bufsize);
        if (args == NULL) {
            fprintf(stderr,"malloc: lack of memory");
            return 1;
        }
        pthread_create(&worker_threads[i],NULL,worker_proc,args);
    }
    
    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;
    }

    while ((csock = accept(sock, (struct sockaddr *)&client_addr,&client_addr_len)) >= 0)
    {
        char ip_buf[INET_ADDRSTRLEN];
        const char * msg = inet_ntop(AF_INET,&client_addr.sin_addr,ip_buf,sizeof(ip_buf));
        fprintf(stderr,"Connected on : %s:%d\n",msg == NULL ? "(null)" : msg , ntohs(addr.sin_port));
        for(;;){
            pthread_mutex_lock(&globalState.sock_mutex);
            if (queue_isfull(&globalState.socks)){
                pthread_mutex_unlock(&globalState.sock_mutex);
#ifdef _GNU_SOURCE
                pthread_yield();
#else
                usleep(400);
#endif    
                continue;
            }
            else enqueue(&globalState.socks,csock);
            break;
        }
        pthread_mutex_unlock(&globalState.sock_mutex);
        pthread_cond_signal(&globalState.ready);
    }
    
    return 1;
}