#include <arpa/inet.h>
#include <errno.h>
#include <libgen.h>
#include <netdb.h>
#include <resolv.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>
#include <sys/wait.h>
#include <netinet/in.h>
#include <sys/select.h>
#include <sys/poll.h>
#include <sys/epoll.h>

#include <string.h>

#define BUF_SIZE 8192

#define READ  0
#define WRITE 1

#define DEFAULT_LOCAL_PORT    8080
#define DEFAULT_REMOTE_PORT   8081
#define SERVER_SOCKET_ERROR -1
#define SERVER_SETSOCKOPT_ERROR -2
#define SERVER_BIND_ERROR -3
#define SERVER_LISTEN_ERROR -4
#define CLIENT_SOCKET_ERROR -5
#define CLIENT_RESOLVE_ERROR -6
#define CLIENT_CONNECT_ERROR -7
#define CREATE_PIPE_ERROR -8
#define BROKEN_PIPE_ERROR -9
#define HEADER_BUFFER_FULL -10
#define BAD_HTTP_PROTOCOL -11

#define MAX_HEADER_SIZE 8192


#if defined(OS_ANDROID)
#include <android/log.h>

#define LOG(fmt...) __android_log_print(ANDROID_LOG_DEBUG,__FILE__,##fmt)

#else
#define LOG(fmt...)  do { fprintf(stderr,"%s %s ",__DATE__,__TIME__); fprintf(stderr, ##fmt); } while(0)
#endif


char remote_host[128];
int remote_port;
int local_port;

int server_sock;
int client_sock;
int remote_sock;


char *header_buffer;


enum
{
    FLG_NONE = 0,       /* 正常数据流不进行编解码 */
    R_C_DEC = 1,        /* 读取客户端数据仅进行解码 */
    W_S_ENC = 2         /* 发送到服务端进行编码 */
};

static int io_flag; /* 网络io的一些标志位 */
static int m_pid; /* 保存主进程id */



void server_loop();

void stop_server();

void handle_client(int client_sock);

void forward_header(int destination_sock);

void forward_data(int source_sock, int destination_sock);

void rewrite_header();

int send_data(int socket, char *buffer, int len);

int receive_data(int socket, char *buffer, int len);

void hand_mproxy_info_req(int sock, char *header_buffer);

void get_info(char *output);

const char *get_work_mode();

int create_connection();

int _main(int argc, char *argv[]);


ssize_t readLine(int fd, void *buffer, size_t n)
{
    ssize_t numRead;
    size_t totRead;
    char *buf;
    char ch;

    if (n <= 0 || buffer == NULL) {
        errno = EINVAL;
        return -1;
    }

    buf = buffer;

    totRead = 0;
    for (;;) {
        numRead = receive_data(fd, &ch, 1);

        if (numRead == -1) {
            if (errno == EINTR)
                continue;
            else
                return -1;              /* 未知错误 */

        } else if (numRead == 0) {      /* EOF */
            if (totRead == 0)           /* No bytes read; return 0 */
                return 0;
            else                        /* Some bytes read; add '\0' */
                break;

        } else {

            if (totRead < n - 1) {      /* Discard > (n - 1) bytes */
                totRead++;
                *buf++ = ch;
            }

            if (ch == '\n')
                break;
        }
    }

    *buf = '\0';
    return totRead;
}

int read_header(int fd, void *buffer)
{
    // bzero(header_buffer,sizeof(MAX_HEADER_SIZE));
    memset(header_buffer, 0, MAX_HEADER_SIZE);
    char line_buffer[2048];
    char *base_ptr = header_buffer;

    for (;;) {
        memset(line_buffer, 0, 2048);

        int total_read = readLine(fd, line_buffer, 2048);
        if (total_read <= 0) {
            return CLIENT_SOCKET_ERROR;
        }
        //防止header缓冲区蛮越界
        if (base_ptr + total_read - header_buffer <= MAX_HEADER_SIZE) {
            strncpy(base_ptr, line_buffer, total_read);
            base_ptr += total_read;
        } else {
            return HEADER_BUFFER_FULL;
        }

        //读到了空行，http头结束
        if (strcmp(line_buffer, "\r\n") == 0 || strcmp(line_buffer, "\n") == 0) {
            break;
        }

    }
    return 0;

}

void extract_server_path(const char *header, char *output)
{
    char *p = strstr(header, "GET /");
    if (p) {
        char *p1 = strchr(p + 4, ' ');
        strncpy(output, p + 4, (int) (p1 - p - 4));
    }

}

int extract_host(const char *header)
{

    char *_p = strstr(header, "CONNECT");  /* 在 CONNECT 方法中解析 隧道主机名称及端口号 */
    if (_p) {
        char *_p1 = strchr(_p, ' ');

        char *_p2 = strchr(_p1 + 1, ':');
        char *_p3 = strchr(_p1 + 1, ' ');

        if (_p2) {
            char s_port[10];
            bzero(s_port, 10);

            strncpy(remote_host, _p1 + 1, (int) (_p2 - _p1) - 1);
            strncpy(s_port, _p2 + 1, (int) (_p3 - _p2) - 1);
            remote_port = atoi(s_port);

        } else {
            strncpy(remote_host, _p1 + 1, (int) (_p3 - _p1) - 1);
            remote_port = 80;
        }


        return 0;
    }


    char *p = strstr(header, "Host:");
    if (!p) {
        return BAD_HTTP_PROTOCOL;
    }
    char *p1 = strchr(p, '\n');
    if (!p1) {
        return BAD_HTTP_PROTOCOL;
    }

    char *p2 = strchr(p + 5, ':'); /* 5是指'Host:'的长度 */

    if (p2 && p2 < p1) {

        int p_len = (int) (p1 - p2 - 1);
        char s_port[p_len];
        strncpy(s_port, p2 + 1, p_len);
        s_port[p_len] = '\0';
        remote_port = atoi(s_port);

        int h_len = (int) (p2 - p - 5 - 1);
        strncpy(remote_host, p + 5 + 1, h_len); //Host:
        //assert h_len < 128;
        remote_host[h_len] = '\0';
    } else {
        int h_len = (int) (p1 - p - 5 - 1 - 1);
        strncpy(remote_host, p + 5 + 1, h_len);
        //assert h_len < 128;
        remote_host[h_len] = '\0';
        remote_port = 80;
    }
    return 0;
}

/* 响应隧道连接请求  */
int send_tunnel_ok(int client_sock)
{
    char *resp = "HTTP/1.1 200 Connection Established\r\n\r\n";
    int len = strlen(resp);
    char buffer[len + 1];
    strcpy(buffer, resp);
    if (send_data(client_sock, buffer, len) < 0) {
        perror("Send http tunnel response  failed\n");
        return -1;
    }
    return 0;
}


//返回mproxy的运行基本信息
void hand_mproxy_info_req(int sock, char *header)
{
    char server_path[255];
    char response[8192];
    extract_server_path(header, server_path);

    LOG("server path:%s\n", server_path);
    char info_buf[1024];
    get_info(info_buf);
    sprintf(response, "HTTP/1.0 200 OK\nServer: MProxy/0.1\n\
                    Content-type: text/html; charset=utf-8\n\n\
                     <html><body>\
                     <pre>%s</pre>\
                     </body></html>\n", info_buf);


    write(sock, response, strlen(response));

}

/* 获取运行的基本信息输出到指定的缓冲区 */
void get_info(char *output)
{
    int pos = 0;
    char line_buffer[512];
    sprintf(line_buffer, "======= mproxy (v0.1) ========\n");
    int len = strlen(line_buffer);
    memcpy(output, line_buffer, len);
    pos += len;

    sprintf(line_buffer, "%s\n", get_work_mode());
    len = strlen(line_buffer);
    memcpy(output + pos, line_buffer, len);
    pos += len;

    if (strlen(remote_host) > 0) {
        sprintf(line_buffer, "start server on %d and next hop is %s:%d\n", local_port, remote_host, remote_port);

    } else {
        sprintf(line_buffer, "start server on %d\n", local_port);
    }

    len = strlen(line_buffer);
    memcpy(output + pos, line_buffer, len);
    pos += len;

    output[pos] = '\0';

}


const char *get_work_mode()
{

    if (strlen(remote_host) == 0) {
        if (io_flag == FLG_NONE) {
            return "start as normal http proxy";
        } else if (io_flag == R_C_DEC) {
            return "start as remote forward proxy and do decode data when recevie data";
        }

    } else {
        if (io_flag == FLG_NONE) {
            return "start as remote forward proxy";
        } else if (io_flag == W_S_ENC) {
            return "start as forward proxy and do encode data when send data";
        }
    }

    return "unknow";

}

/* 处理客户端的连接 */
void handle_client(int client_sock)
{
    int is_http_tunnel = 0;
    if (strlen(remote_host) == 0) /* 未指定远端主机名称从http 请求 HOST 字段中获取 */
    {

#ifdef DEBUG
        LOG(" ============ handle new client ============\n");
        LOG(">>>Header:%s\n",header_buffer);
#endif

        if (read_header(client_sock, header_buffer) < 0) {
            LOG("Read Http header failed\n");
            return;
        } else {
            char *p = strstr(header_buffer, "CONNECT"); /* 判断是否是http 隧道请求 */
            if (p) {
                LOG("receive CONNECT request\n");
                is_http_tunnel = 1;
            }

            if (strstr(header_buffer, "GET /mproxy") > 0) {
                LOG("====== hand mproxy info request ====");
                //返回mproxy的运行基本信息
                hand_mproxy_info_req(client_sock, header_buffer);

                return;
            }

            if (extract_host(header_buffer) < 0) {
                LOG("Cannot extract host field,bad http protrotol");
                return;
            }
            LOG("Host:%s port: %d io_flag:%d\n", remote_host, remote_port, io_flag);

        }
    }

    if ((remote_sock = create_connection()) < 0) {
        LOG("Cannot connect to host [%s:%d]\n", remote_host, remote_port);
        return;
    }

    if (fork() == 0) { // 创建子进程用于从客户端转发数据到远端socket接口

        if (strlen(header_buffer) > 0 && !is_http_tunnel) {
            forward_header(remote_sock); //普通的http请求先转发header
        }

        forward_data(client_sock, remote_sock);
        exit(0);
    }

    if (fork() == 0) { // 创建子进程用于转发从远端socket接口过来的数据到客户端

        if (io_flag == W_S_ENC) {
            io_flag = R_C_DEC; //发送请求给服务端进行编码，读取服务端的响应则进行解码
        } else if (io_flag == R_C_DEC) {
            io_flag = W_S_ENC; //接收客户端请求进行解码，那么响应客户端请求需要编码
        }

        if (is_http_tunnel) {
            send_tunnel_ok(client_sock);
        }

        forward_data(remote_sock, client_sock);
        exit(0);
    }

    close(remote_sock);
    close(client_sock);
}

void forward_header(int destination_sock)
{
    rewrite_header();
#ifdef DEBUG
    LOG("================ The Forward HEAD =================");
        LOG("%s\n",header_buffer);
#endif

    int len = strlen(header_buffer);
    send_data(destination_sock, header_buffer, len);
}

int send_data(int socket, char *buffer, int len)
{

    if (io_flag == W_S_ENC) {
        int i;
        for (i = 0; i < len; i++) {
            buffer[i] ^= 1;

        }
    }

    return send(socket, buffer, len, 0);
}

int receive_data(int socket, char *buffer, int len)
{
    int n = recv(socket, buffer, len, 0);
    if (io_flag == R_C_DEC && n > 0) {
        int i;
        for (i = 0; i < n; i++) {
            buffer[i] ^= 1;
            // printf("%d => %d\n",c,buffer[i]);
        }
    }

    return n;
}


/* 代理中的完整URL转发前需改成 path 的形式 */
void rewrite_header()
{
    char *p = strstr(header_buffer, "http://");
    char *p0 = strchr(p, '\0');
    char *p5 = strstr(header_buffer, "HTTP/"); /* "HTTP/" 是协议标识 如 "HTTP/1.1" */
    int len = strlen(header_buffer);
    if (p) {
        char *p1 = strchr(p + 7, '/');
        if (p1 && (p5 > p1)) {
            //转换url到 path
            memcpy(p, p1, (int) (p0 - p1));
            int l = len - (p1 - p);
            header_buffer[l] = '\0';


        } else {
            char *p2 = strchr(p, ' ');  //GET http://3g.sina.com.cn HTTP/1.1

            // printf("%s\n",p2);
            memcpy(p + 1, p2, (int) (p0 - p2));
            *p = '/';  //url 没有路径使用根
            int l = len - (p2 - p) + 1;
            header_buffer[l] = '\0';

        }
    }
}


void forward_data(int source_sock, int destination_sock)
{
    char buffer[BUF_SIZE];
    int n;

    while ((n = receive_data(source_sock, buffer, BUF_SIZE)) > 0) {

        send_data(destination_sock, buffer, n);
    }

    shutdown(destination_sock, SHUT_RDWR);

    shutdown(source_sock, SHUT_RDWR);
}


int create_connection()
{
    struct sockaddr_in server_addr;
    struct hostent *server;
    int sock;

    if ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        return CLIENT_SOCKET_ERROR;
    }

    if ((server = gethostbyname(remote_host)) == NULL) {
        errno = EFAULT;
        return CLIENT_RESOLVE_ERROR;
    }
    LOG("======= forward request to remote host:%s port:%d ======= \n", remote_host, remote_port);
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    memcpy(&server_addr.sin_addr.s_addr, server->h_addr, server->h_length);
    server_addr.sin_port = htons(remote_port);

    if (connect(sock, (struct sockaddr *) &server_addr, sizeof(server_addr)) < 0) {
        return CLIENT_CONNECT_ERROR;
    }

    return sock;
}


int create_server_socket(int port)
{
    int server_sock, optval;
    struct sockaddr_in server_addr;

    if ((server_sock = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        return SERVER_SOCKET_ERROR;
    }

    if (setsockopt(server_sock, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval)) < 0) {
        return SERVER_SETSOCKOPT_ERROR;
    }

    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(port);
    server_addr.sin_addr.s_addr = INADDR_ANY;

    if (bind(server_sock, (struct sockaddr *) &server_addr, sizeof(server_addr)) != 0) {
        return SERVER_BIND_ERROR;
    }

    if (listen(server_sock, 20) < 0) {
        return SERVER_LISTEN_ERROR;
    }

    return server_sock;
}

/* 处理僵尸进程 */
void sigchld_handler(int signal)
{
    while (waitpid(-1, NULL, WNOHANG) > 0);
}


void server_loop()
{
    struct sockaddr_in client_addr;
    socklen_t addrlen = sizeof(client_addr);

    while (1) {
        client_sock = accept(server_sock, (struct sockaddr *) &client_addr, &addrlen);

        if (fork() == 0) { // 创建子进程处理客户端连接请求
            close(server_sock);
            handle_client(client_sock);
            exit(0);
        }
        close(client_sock);
    }

}

void server_select()
{
    int fdArray[sizeof(fd_set)<<3];
    fdArray[0] = server_sock;
    int num = sizeof(fdArray)/sizeof(fdArray[0]);
    for(int i=1;i<num;++i)
        fdArray[i] = -1;
    while(1)
    {
        fd_set rfds;
        FD_ZERO(&rfds);
        int max = fdArray[0];
        for(int i=0;i<num;++i)
        {
            if(fdArray[i]>=0)
            {
                FD_SET(fdArray[i], &rfds);
                max = max>fdArray[i]?max:fdArray[i];
            }
        }
        struct timeval timeout = {5, 0};
        switch(select(max+1, &rfds, NULL, NULL, &timeout))
        {
            case 0:
                printf("timeout\n");
                break;
            case -1:
                perror("select");
                break;
            default:
            {
                for(int i=0;i<num;++i)
                {
                    if(fdArray[i]==-1)
                        continue;
                    if(i==0 && fdArray[i]==server_sock && FD_ISSET(fdArray[i], &rfds))
                    {
                        struct sockaddr_in client_addr;
                        socklen_t addrlen = sizeof(client_addr);
                        int new_sock = accept(server_sock, (struct sockaddr *) &client_addr, &addrlen);
                        handle_client(new_sock);
                        close(new_sock);
                    }
                }
            }
        }
    }
}


void server_poll()
{
    struct pollfd peerfd[1024];
    peerfd[0].fd = server_sock;
    peerfd[0].events = POLLIN;
    int nfds = 1;
    int ret;
    int maxsize = sizeof(peerfd)/sizeof(peerfd[0]);
    int timeout =  -1;
    for(int i=1;i<maxsize;++i)
        peerfd[i].fd = -1;
    while(1)
    {
        switch (ret = poll(peerfd, nfds, timeout))
        {
            case 0:
                printf("timeout\n");
                break;
            case -1:
                perror("poll");
                break;
            default:
            {
                for(int i=0;i<maxsize;++i)
                {
                    struct sockaddr_in client_addr;
                    socklen_t addrlen = sizeof(client_addr);
                    if ((peerfd[i].fd == server_sock) && (peerfd[i].revents & POLLIN))
                    {
                        int new_sock = accept(server_sock, (struct sockaddr *) &client_addr, &addrlen);
                        int j = 1;
                        for ( ; j < maxsize; ++j) {
                            if (peerfd[j].fd < 0) {
                                peerfd[j].fd = new_sock;
                                peerfd[j].events = POLLIN;
                                peerfd[j].revents = 0;
                                break;
                            }
                        }
                        if (j == maxsize) {
                            printf("too many connections.\n");
                            close(new_sock);
                        }
                        if (j + 1 > nfds)
                            nfds = j + 1;
                    }
                    else if((peerfd[i].fd>0) &&(peerfd[i].revents & POLLIN))
                    {
                        handle_client(peerfd[i].fd);
                        close(peerfd[i].fd);
                        peerfd[i].fd = -1;
                    }
                }
            }
        }
    }

}


void server_epoll()
{
    int epollfd = epoll_create(1024);
    if(epollfd<0)
    {
        perror("epoll_create");
    }
    struct epoll_event ev;
    ev.events = EPOLLIN;
    ev.data.fd = server_sock;
    if(epoll_ctl(epollfd, EPOLL_CTL_ADD, server_sock, &ev)<0)
    {
        perror("epoll_ctl");
    }
    int evnums = 0;
    struct epoll_event evs[1024];
    int timeout = -1;
    while(1)
    {
        switch(evnums = epoll_wait(epollfd, evs, 1024, timeout))
        {
            case 0:
                printf("timeout\n");
                break;
            case -1:
                perror("epoll_wait");
                break;
            default:
            {
                for(int i=0;i<evnums;++i)
                {
                    struct sockaddr_in client;
                    socklen_t len = sizeof(client);
                    if(evs[i].data.fd == server_sock && evs[i].events & EPOLLIN)
                    {
                        int new_sock = accept(server_sock, (struct sockaddr *) &client, &len);
                        ev.data.fd = new_sock;
                        ev.events = EPOLLIN;
                        epoll_ctl(epollfd, EPOLL_CTL_ADD, new_sock, &ev);
                    }
                    else if(evs[i].data.fd>0 && evs[i].events & EPOLLIN)
                    {
                        handle_client(evs[i].data.fd);
                        close(evs[i].data.fd);
                        epoll_ctl(epollfd, EPOLL_CTL_DEL, evs[i].data.fd, NULL);
                    }
                }
            }
        }
    }
}


void stop_server()
{
    kill(m_pid, SIGKILL);
}

void usage(void)
{
    printf("Usage:\n");
    printf(" -l <port number>  specifyed local listen port \n");
    printf(" -h <remote server and port> specifyed next hop server name\n");
    printf(" -d <remote server and port> run as daemon\n");
    printf("-E encode data when forwarding data\n");
    printf("-D decode data when receiving data\n");
    exit(8);
}

void start_server(int daemon)
{
    //初始化全局变量
    header_buffer = (char *) malloc(MAX_HEADER_SIZE);

    signal(SIGCHLD, sigchld_handler); // 防止子进程变成僵尸进程

    if ((server_sock = create_server_socket(local_port)) < 0) { // start server
        LOG("Cannot run server on %d\n", local_port);
        exit(server_sock);
    }

    if (daemon) {
        pid_t pid;
        if ((pid = fork()) == 0) {
            server_loop();
        } else if (pid > 0) {
            m_pid = pid;
            LOG("mporxy pid is: [%d]\n", pid);
            close(server_sock);
        } else {
            LOG("Cannot daemonize\n");
            exit(pid);
        }

    } else {
        //这里修改服务模式
        server_loop();
//        server_select();
//        server_poll();
//        server_epoll();
    }

}

int main(int argc, char *argv[])
{
    return _main(argc, argv);
}

int _main(int argc, char *argv[])
{
    local_port = DEFAULT_LOCAL_PORT;
    io_flag = FLG_NONE;
    int daemon = 0;

    char info_buf[2048];

    int opt;
    char optstrs[] = ":l:h:dED";
    char *p = NULL;
    while (-1 != (opt = getopt(argc, argv, optstrs))) {
        switch (opt) {
            case 'l':
                local_port = atoi(optarg);
                break;
            case 'h':
                p = strchr(optarg, ':');
                if (p) {
                    strncpy(remote_host, optarg, p - optarg);
                    remote_port = atoi(p + 1);
                } else {
                    strncpy(remote_host, optarg, strlen(remote_host));
                }
                break;
            case 'd':
                daemon = 1;
                break;
            case 'E':
                io_flag = W_S_ENC;
                break;
            case 'D':
                io_flag = R_C_DEC;
                break;
            case ':':
                printf("\nMissing argument after: -%c\n", optopt);
                usage();
            case '?':
                printf("\nInvalid argument: %c\n", optopt);
            default:
                usage();
        }
    }

    get_info(info_buf);
    LOG("%s\n", info_buf);
    start_server(daemon);
    return 0;

}