/**
 * @file tcp_server.c
 * @brief TCP Server module implementation for transparent transmission with UART2
 */

#include "tcp_server.h"
#include "config.h"
#include "lwip/opt.h"
#include "lwip/tcp.h"
#include "lwip/sys.h"
#include "lwip/sockets.h"

#include "FreeRTOS.h"
#include "task.h"
#include "stream_buffer.h"

#include <string.h>

/*---------------------------------------------------------------------------
 * Private Variables
 *---------------------------------------------------------------------------*/

/* Server configuration */
static tcp_server_config_t server_config = {
    .port = TCP_SERVER_DEFAULT_PORT,
    .auto_reconnect = true
};

/* Server status */
static tcp_server_status_t server_status = {
    .state = TCP_SERVER_STATE_IDLE,
    .rx_bytes = 0,
    .tx_bytes = 0,
    .connections = 0,
    .errors = 0
};

/* Socket descriptors */
static int listen_socket = -1;
static int client_socket = -1;

/* Stream buffers for UART integration */
static StreamBufferHandle_t rx_stream = NULL;  /* TCP RX -> UART TX */
static StreamBufferHandle_t tx_stream = NULL;  /* UART RX -> TCP TX */

/*---------------------------------------------------------------------------
 * Public Functions
 *---------------------------------------------------------------------------*/

static int tcp_server_send_all(int sock, const uint8_t *data, uint16_t len)
{
    uint16_t total = 0;

    while (total < len)
    {
        int sent = send(sock, data + total, len - total, 0);
        if (sent > 0)
        {
            total += (uint16_t)sent;
        }
        else
        {
            return -1;
        }
    }

    return (int)total;
}

/**
 * @brief Initialize TCP Server module
 */
int tcp_server_init(const tcp_server_config_t *config)
{
    if (config != NULL)
    {
        memcpy(&server_config, config, sizeof(tcp_server_config_t));
    }
    
    /* Create stream buffers */
    if (rx_stream == NULL)
    {
        rx_stream = xStreamBufferCreate(TCP_SERVER_RX_BUFFER_SIZE, 1);
        if (rx_stream == NULL)
        {
            return -1;
        }
    }
    
    if (tx_stream == NULL)
    {
        tx_stream = xStreamBufferCreate(TCP_SERVER_TX_BUFFER_SIZE, 1);
        if (tx_stream == NULL)
        {
            return -1;
        }
    }
    
    server_status.state = TCP_SERVER_STATE_IDLE;
    
    return 0;
}

/**
 * @brief Start TCP Server
 */
int tcp_server_start(void)
{
    struct sockaddr_in server_addr;
    int opt = 1;
    
    if (listen_socket >= 0)
    {
        /* Already started */
        return 0;
    }
    
    /* Create socket */
    listen_socket = socket(AF_INET, SOCK_STREAM, 0);
    if (listen_socket < 0)
    {
        server_status.state = TCP_SERVER_STATE_ERROR;
        server_status.errors++;
        return -1;
    }
    
    /* Set socket options */
    setsockopt(listen_socket, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
    
    /* Bind to port */
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = INADDR_ANY;
    server_addr.sin_port = htons(server_config.port);
    
    if (bind(listen_socket, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0)
    {
        close(listen_socket);
        listen_socket = -1;
        server_status.state = TCP_SERVER_STATE_ERROR;
        server_status.errors++;
        return -1;
    }
    
    /* Start listening */
    if (listen(listen_socket, TCP_SERVER_MAX_CONNECTIONS) < 0)
    {
        close(listen_socket);
        listen_socket = -1;
        server_status.state = TCP_SERVER_STATE_ERROR;
        server_status.errors++;
        return -1;
    }
    
    server_status.state = TCP_SERVER_STATE_LISTENING;
    
    return 0;
}

/**
 * @brief Stop TCP Server
 */
int tcp_server_stop(void)
{
    if (client_socket >= 0)
    {
        close(client_socket);
        client_socket = -1;
    }
    
    if (listen_socket >= 0)
    {
        close(listen_socket);
        listen_socket = -1;
    }
    
    server_status.state = TCP_SERVER_STATE_IDLE;
    
    return 0;
}

/**
 * @brief Send data to connected client
 */
int tcp_server_send(const uint8_t *data, uint16_t len)
{
    int sent;
    
    if (client_socket < 0)
    {
        return -1;
    }
    
    sent = tcp_server_send_all(client_socket, data, len);
    if (sent > 0)
    {
        server_status.tx_bytes += sent;
    }
    else if (sent < 0)
    {
        /* Connection error */
        close(client_socket);
        client_socket = -1;
        server_status.state = TCP_SERVER_STATE_LISTENING;
        server_status.errors++;
    }
    
    return sent;
}

/**
 * @brief Receive data from connected client
 */
int tcp_server_recv(uint8_t *data, uint16_t max_len, uint32_t timeout_ms)
{
    int received;
    struct timeval tv;
    
    if (client_socket < 0)
    {
        return -1;
    }
    
    /* Set receive timeout */
    tv.tv_sec = timeout_ms / 1000;
    tv.tv_usec = (timeout_ms % 1000) * 1000;
    setsockopt(client_socket, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv));
    
    received = recv(client_socket, data, max_len, 0);
    if (received > 0)
    {
        server_status.rx_bytes += received;
    }
    else if (received == 0)
    {
        /* Connection closed by client */
        close(client_socket);
        client_socket = -1;
        server_status.state = TCP_SERVER_STATE_LISTENING;
    }
    else if (received < 0)
    {
        /* Timeout or error - check errno */
        /* For timeout, just return 0 */
    }
    
    return received;
}

/**
 * @brief Check if client is connected
 */
bool tcp_server_is_connected(void)
{
    return (client_socket >= 0);
}

/**
 * @brief Get TCP Server status
 */
void tcp_server_get_status(tcp_server_status_t *status)
{
    if (status != NULL)
    {
        memcpy(status, &server_status, sizeof(tcp_server_status_t));
    }
}

/**
 * @brief Get RX StreamBuffer handle
 */
void *tcp_server_get_rx_stream(void)
{
    return rx_stream;
}

/**
 * @brief Get TX StreamBuffer handle
 */
void *tcp_server_get_tx_stream(void)
{
    return tx_stream;
}

/**
 * @brief TCP Server task
 */
void tcp_server_task(void *argument)
{
    const device_config_t *cfg;
    tcp_server_config_t task_cfg;
    struct sockaddr_in client_addr;
    socklen_t addr_len;
    uint8_t rx_buffer[256];
    uint8_t tx_buffer[256];
    int received;
    size_t tx_len;
    fd_set read_fds;
    struct timeval tv;
    int max_fd;
    
    (void)argument;
    
    /* Initialize server */
    task_cfg.port = TCP_SERVER_DEFAULT_PORT;
    task_cfg.auto_reconnect = true;
    cfg = config_get();
    if (cfg != NULL && cfg->server_port > 0)
    {
        task_cfg.port = cfg->server_port;
    }
    tcp_server_init(&task_cfg);
    
    /* Start server */
    while (tcp_server_start() != 0)
    {
        vTaskDelay(pdMS_TO_TICKS(1000));
    }
    
    while (1)
    {
        /* Check if we need to accept a new connection */
        if (client_socket < 0 && listen_socket >= 0)
        {
            /* Use select with timeout to check for incoming connections */
            FD_ZERO(&read_fds);
            FD_SET(listen_socket, &read_fds);
            tv.tv_sec = 0;
            tv.tv_usec = 100000;  /* 100ms timeout */
            
            if (select(listen_socket + 1, &read_fds, NULL, NULL, &tv) > 0)
            {
                addr_len = sizeof(client_addr);
                client_socket = accept(listen_socket, (struct sockaddr *)&client_addr, &addr_len);
                if (client_socket >= 0)
                {
                    server_status.state = TCP_SERVER_STATE_CONNECTED;
                    server_status.connections++;
                }
            }
        }
        
        /* Handle data transfer if connected */
        if (client_socket >= 0)
        {
            /* Check for data from TCP client */
            FD_ZERO(&read_fds);
            FD_SET(client_socket, &read_fds);
            max_fd = client_socket;
            tv.tv_sec = 0;
            tv.tv_usec = 10000;  /* 10ms timeout */
            
            if (select(max_fd + 1, &read_fds, NULL, NULL, &tv) > 0)
            {
                if (FD_ISSET(client_socket, &read_fds))
                {
                    received = recv(client_socket, rx_buffer, sizeof(rx_buffer), 0);
                    if (received > 0)
                    {
                        /* Forward to UART via stream buffer */
                        xStreamBufferSend(rx_stream, rx_buffer, received, pdMS_TO_TICKS(10));
                        server_status.rx_bytes += received;
                    }
                    else if (received == 0)
                    {
                        /* Connection closed */
                        close(client_socket);
                        client_socket = -1;
                        server_status.state = TCP_SERVER_STATE_LISTENING;
                    }
                    else
                    {
                        /* Error */
                        close(client_socket);
                        client_socket = -1;
                        server_status.state = TCP_SERVER_STATE_LISTENING;
                        server_status.errors++;
                    }
                }
            }
            
            /* Check for data from UART to send to TCP */
            tx_len = xStreamBufferReceive(tx_stream, tx_buffer, sizeof(tx_buffer), 0);
            if (tx_len > 0)
            {
                int sent = tcp_server_send_all(client_socket, tx_buffer, (uint16_t)tx_len);
                if (sent > 0)
                {
                    server_status.tx_bytes += sent;
                }
                else if (sent < 0)
                {
                    /* Send error */
                    close(client_socket);
                    client_socket = -1;
                    server_status.state = TCP_SERVER_STATE_LISTENING;
                    server_status.errors++;
                }
            }
        }
        
        /* Small delay to prevent tight loop */
        vTaskDelay(pdMS_TO_TICKS(1));
    }
}