#include <rtthread.h>
#include <lwip/api.h>
#include <lwip/sockets.h>
#include <rtdevice.h>

#include <finsh.h>
#include <shell.h>

#define TELNET_PORT         23
#define TELNET_BACKLOG      5
#define RX_BUFFER_SIZE      256
#define TX_BUFFER_SIZE      4096

#define ISO_nl              0x0a
#define ISO_cr              0x0d

#define STATE_NORMAL        0
#define STATE_IAC           1
#define STATE_WILL          2
#define STATE_WONT          3
#define STATE_DO            4
#define STATE_DONT          5
#define STATE_CLOSE         6

#define TELNET_IAC          255
#define TELNET_WILL         251
#define TELNET_WONT         252
#define TELNET_DO           253
#define TELNET_DONT         254

struct telnet_session
{
    struct rt_ringbuffer rx_ringbuffer;
    struct rt_ringbuffer tx_ringbuffer;

    rt_mutex_t rx_ringbuffer_lock;
    rt_mutex_t tx_ringbuffer_lock;

    struct rt_device device;
    rt_int32_t server_fd;
    rt_int32_t client_fd;

    /* telnet protocol */
    rt_uint8_t state;
    rt_uint8_t echo_mode;

};

static struct telnet_session* telnet;

/* process tx data */
static void send_to_client(struct telnet_session* telnet)
{
    rt_size_t length;
    rt_uint8_t tx_buffer[32];

    while (1)
    {
        rt_memset(tx_buffer, 0, sizeof(tx_buffer));
        rt_mutex_take(telnet->tx_ringbuffer_lock, RT_WAITING_FOREVER);
        /* get buffer from ringbuffer */
        length = rt_ringbuffer_get(&(telnet->tx_ringbuffer), tx_buffer, sizeof(tx_buffer));
        rt_mutex_release(telnet->tx_ringbuffer_lock);

        /* do a tx procedure */
        if (length > 0)
        {
            send(telnet->client_fd, tx_buffer, length, 0);
        }
        else break;
    }
}

/* send telnet option to remote */
static void send_option_to_client(struct telnet_session* telnet, rt_uint8_t option, rt_uint8_t value)
{
    rt_uint8_t optbuf[4];

    optbuf[0] = TELNET_IAC;
    optbuf[1] = option;
    optbuf[2] = value;
    optbuf[3] = 0;

    rt_mutex_take(telnet->tx_ringbuffer_lock, RT_WAITING_FOREVER);
    rt_ringbuffer_put(&telnet->tx_ringbuffer, optbuf, 3);
    rt_mutex_release(telnet->tx_ringbuffer_lock);

    send_to_client(telnet);
}

/* process rx data */
static void process_rx(struct telnet_session* telnet, rt_uint8_t *data, rt_size_t length)
{
    rt_size_t rx_length, index;

    for (index = 0; index < length; index ++)
    {
        switch(telnet->state)
        {
        case STATE_IAC:
            if (*data == TELNET_IAC)
            {
                rt_mutex_take(telnet->rx_ringbuffer_lock, RT_WAITING_FOREVER);
                /* put buffer to ringbuffer */
                rt_ringbuffer_putchar(&(telnet->rx_ringbuffer), *data);
                rt_mutex_release(telnet->rx_ringbuffer_lock);

                telnet->state = STATE_NORMAL;
            }
            else
            {
                /* set telnet state according to received package */
                switch (*data)
                {
                case TELNET_WILL: telnet->state = STATE_WILL; break;
                case TELNET_WONT: telnet->state = STATE_WONT; break;
                case TELNET_DO:   telnet->state = STATE_DO; break;
                case TELNET_DONT: telnet->state = STATE_DONT; break;
                default: telnet->state = STATE_NORMAL; break;
                }
            }
            break;

        /* don't option */
        case STATE_WILL:
        case STATE_WONT:
            send_option_to_client(telnet, TELNET_DONT, *data);
            telnet->state = STATE_NORMAL;
            break;

        /* won't option */
        case STATE_DO:
        case STATE_DONT:
            send_option_to_client(telnet, TELNET_WONT, *data);
            telnet->state = STATE_NORMAL;
            break;

        case STATE_NORMAL:
            if (*data == TELNET_IAC) telnet->state = STATE_IAC;
            else if (*data != '\r') /* ignore '\r' */
            {
                rt_mutex_take(telnet->rx_ringbuffer_lock, RT_WAITING_FOREVER);
                /* put buffer to ringbuffer */
                rt_ringbuffer_putchar(&(telnet->rx_ringbuffer), *data);
                rt_mutex_release(telnet->rx_ringbuffer_lock);
            }
            break;
        }

        data ++;
    }

    rt_mutex_take(telnet->rx_ringbuffer_lock, RT_WAITING_FOREVER);
    /* get total size */
    rx_length = rt_ringbuffer_data_len(&telnet->rx_ringbuffer);
    rt_mutex_release(telnet->rx_ringbuffer_lock);

    /* indicate there are reception data */
    if ((rx_length > 0) && (telnet->device.rx_indicate != RT_NULL))
        telnet->device.rx_indicate(&telnet->device, rx_length);

    return;
}

/* client close */
static void client_close(struct telnet_session* telnet)
{
    /* set console */
    rt_console_set_device(RT_CONSOLE_DEVICE_NAME);
    /* set finsh device */
    finsh_set_device(RT_CONSOLE_DEVICE_NAME);

    /* close connection */
    closesocket(telnet->client_fd);

    /* restore shell option */
    finsh_set_echo(telnet->echo_mode);

    rt_kprintf("resume console to %s\n", RT_CONSOLE_DEVICE_NAME);
}

/* RT-Thread Device Driver Interface */
static rt_err_t telnet_init(rt_device_t dev)
{
    return RT_EOK;
}

static rt_err_t telnet_open(rt_device_t dev, rt_uint16_t oflag)
{
    return RT_EOK;
}

static rt_err_t telnet_close(rt_device_t dev)
{
    return RT_EOK;
}

static rt_size_t telnet_read(rt_device_t dev, rt_off_t pos, void* buffer, rt_size_t size)
{
    rt_size_t result;

    /* read from rx ring buffer */
    rt_mutex_take(telnet->rx_ringbuffer_lock, RT_WAITING_FOREVER);
    result = rt_ringbuffer_get(&(telnet->rx_ringbuffer), buffer, size);
    rt_mutex_release(telnet->rx_ringbuffer_lock);

    return result;
}

static rt_size_t telnet_write (rt_device_t dev, rt_off_t pos, const void* buffer, rt_size_t size)
{
    const rt_uint8_t *ptr;

    ptr = (rt_uint8_t*) buffer;

    rt_mutex_take(telnet->tx_ringbuffer_lock, RT_WAITING_FOREVER);
    while (size)
    {
        if (*ptr == '\n')
            rt_ringbuffer_putchar(&telnet->tx_ringbuffer, '\r');

        if (rt_ringbuffer_putchar(&telnet->tx_ringbuffer, *ptr) == 0) /* overflow */
            break;
        ptr++;
        size--;
    }
    rt_mutex_release(telnet->tx_ringbuffer_lock);

    /* send data to telnet client */
    send_to_client(telnet);

    return (rt_uint32_t) ptr - (rt_uint32_t) buffer;
}

static rt_err_t telnet_control(rt_device_t dev, rt_uint8_t cmd, void *args)
{
    return RT_EOK;
}

/* telnet server thread entry */
static void telnet_thread(void* parameter)
{
#define RECV_BUF_LEN 64

    struct sockaddr_in addr;
    socklen_t addr_size;
    rt_uint8_t recv_buf[RECV_BUF_LEN];
    rt_int32_t recv_len = 0;

    if ((telnet->server_fd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
    {
        rt_kprintf("telnet: create socket failed\n");
        return;
    }

    addr.sin_family = AF_INET;
    addr.sin_port = htons(TELNET_PORT);
    addr.sin_addr.s_addr = INADDR_ANY;
    rt_memset(&(addr.sin_zero), 0, sizeof(addr.sin_zero));
    if (bind(telnet->server_fd, (struct sockaddr *)&addr, sizeof(struct sockaddr)) == -1)
    {
        rt_kprintf("telnet: bind socket failed\n");
        return;
    }

    if (listen(telnet->server_fd, TELNET_BACKLOG) == -1)
    {
        rt_kprintf("telnet: listen socket failed\n");
        return;
    }

    /* register telnet device */
    telnet->device.type     = RT_Device_Class_Char;
    telnet->device.init     = telnet_init;
    telnet->device.open     = telnet_open;
    telnet->device.close    = telnet_close;
    telnet->device.read     = telnet_read;
    telnet->device.write    = telnet_write;
    telnet->device.control  = telnet_control;

    /* no private */
    telnet->device.user_data = RT_NULL;

    /* register telnet device */
    rt_device_register(&telnet->device, "telnet",
                       RT_DEVICE_FLAG_RDWR | RT_DEVICE_FLAG_STREAM);

    while (1)
    {
        rt_kprintf("telnet server waiting for connection\n");

        /* grab new connection */
        if ((telnet->client_fd = accept(telnet->server_fd, (struct sockaddr * )&addr, &addr_size)) == -1)
        {
            continue;
        }

        rt_kprintf("new telnet client(%s:%d) connection, switch console to telnet...\n", inet_ntoa(addr.sin_addr), addr.sin_port);

        /* process the new connection */
        /* set console */
        rt_console_set_device("telnet");
        /* set finsh device */
        finsh_set_device("telnet");

        /* set init state */
        telnet->state = STATE_NORMAL;

        telnet->echo_mode = finsh_get_echo();
        /* disable echo mode */
        finsh_set_echo(0);

        while (1)
        {
            /* try to send all data in tx ringbuffer */
            send_to_client(telnet);

            /* do a rx procedure */
            if ((recv_len = recv(telnet->client_fd, recv_buf, RECV_BUF_LEN, 0)) > 0)
            {
                process_rx(telnet, recv_buf, recv_len);
            }
            else
            {
                /* close connection */
                client_close(telnet);
                break;
            }
        }
    }
}

/* telnet server */
void telnet_srv(void)
{
    rt_thread_t tid;

    if (telnet == RT_NULL)
    {
        rt_uint8_t *ptr;

        telnet = rt_malloc(sizeof(struct telnet_session));
        if (telnet == RT_NULL)
        {
            rt_kprintf("telnet: no memory\n");
            return;
        }
        /* init ringbuffer */
        ptr = rt_malloc(RX_BUFFER_SIZE);
        if (ptr)
        {
            rt_ringbuffer_init(&telnet->rx_ringbuffer, ptr, RX_BUFFER_SIZE);
        }
        else
        {
            rt_kprintf("telnet: no memory\n");
            return;
        }
        ptr = rt_malloc(TX_BUFFER_SIZE);
        if (ptr)
        {
            rt_ringbuffer_init(&telnet->tx_ringbuffer, ptr, TX_BUFFER_SIZE);
        }
        else
        {
            rt_kprintf("telnet: no memory\n");
            return;
        }
        /* create tx ringbuffer lock */
        telnet->tx_ringbuffer_lock = rt_mutex_create("telnet_tx", RT_IPC_FLAG_FIFO);
        /* create rx ringbuffer lock */
        telnet->rx_ringbuffer_lock = rt_mutex_create("telnet_rx", RT_IPC_FLAG_FIFO);

        tid = rt_thread_create("telnet", telnet_thread, RT_NULL, 2048, 25, 5);
        if (tid != RT_NULL)
            rt_thread_startup(tid);
    }
    else
    {
        rt_kprintf("telnet: already running\n");
    }

}

#ifdef RT_USING_FINSH
#include <finsh.h>
FINSH_FUNCTION_EXPORT(telnet_srv, startup telnet server);
#ifdef FINSH_USING_MSH
MSH_CMD_EXPORT(telnet_srv, startup telnet server)
#endif /* FINSH_USING_MSH */
#endif /* RT_USING_FINSH */