/**
 * @file tcp_server.c
 * @brief lwIP RAW TCP server for the UART2 bridge.
 */

#include "tcp_server.h"

#include "lwip/pbuf.h"
#include "lwip/tcp.h"

#include <string.h>

typedef struct {
    struct tcp_pcb *listen_pcb;
    struct tcp_pcb *client_pcb;
    uint8_t rx_ring[TCP_SERVER_RX_BUFFER_SIZE];
    uint16_t rx_head;
    uint16_t rx_tail;
    tcp_server_config_t config;
    tcp_server_status_t status;
} tcp_server_ctx_t;

static tcp_server_ctx_t g_server;

static uint16_t ring_free(uint16_t head, uint16_t tail, uint16_t size)
{
    return (head >= tail) ? (uint16_t)(size - head + tail - 1u) : (uint16_t)(tail - head - 1u);
}

static err_t tcp_server_on_recv(void *arg, struct tcp_pcb *pcb, struct pbuf *p, err_t err)
{
    tcp_server_ctx_t *ctx = (tcp_server_ctx_t *)arg;
    struct pbuf *q;

    if (err != ERR_OK) {
        if (p != NULL) {
            pbuf_free(p);
        }
        return err;
    }

    if (p == NULL) {
        tcp_arg(pcb, NULL);
        tcp_recv(pcb, NULL);
        tcp_sent(pcb, NULL);
        tcp_err(pcb, NULL);
        if (tcp_close(pcb) != ERR_OK) {
            tcp_abort(pcb);
        }
        ctx->client_pcb = NULL;
        ctx->status.state = TCP_SERVER_STATE_LISTENING;
        return ERR_OK;
    }

    for (q = p; q != NULL; q = q->next) {
        const uint8_t *src = (const uint8_t *)q->payload;
        for (uint16_t i = 0; i < q->len; ++i) {
            if (ring_free(ctx->rx_head, ctx->rx_tail, TCP_SERVER_RX_BUFFER_SIZE) == 0u) {
                ctx->status.errors++;
                break;
            }
            ctx->rx_ring[ctx->rx_head] = src[i];
            ctx->rx_head = (uint16_t)((ctx->rx_head + 1u) % TCP_SERVER_RX_BUFFER_SIZE);
            ctx->status.rx_bytes++;
        }
    }

    tcp_recved(pcb, p->tot_len);
    pbuf_free(p);
    return ERR_OK;
}

static err_t tcp_server_on_sent(void *arg, struct tcp_pcb *pcb, u16_t len)
{
    tcp_server_ctx_t *ctx = (tcp_server_ctx_t *)arg;
    (void)pcb;
    ctx->status.tx_bytes += len;
    return ERR_OK;
}

static void tcp_server_on_err(void *arg, err_t err)
{
    tcp_server_ctx_t *ctx = (tcp_server_ctx_t *)arg;
    (void)err;
    ctx->client_pcb = NULL;
    ctx->status.state = TCP_SERVER_STATE_LISTENING;
    ctx->status.errors++;
}

static err_t tcp_server_on_accept(void *arg, struct tcp_pcb *newpcb, err_t err)
{
    tcp_server_ctx_t *ctx = (tcp_server_ctx_t *)arg;

    if (err != ERR_OK) {
        return err;
    }

    if (ctx->client_pcb != NULL) {
        tcp_abort(newpcb);
        return ERR_ABRT;
    }

    ctx->client_pcb = newpcb;
    ctx->status.state = TCP_SERVER_STATE_CONNECTED;
    ctx->status.connections++;

    tcp_nagle_disable(newpcb);

    tcp_arg(newpcb, ctx);
    tcp_recv(newpcb, tcp_server_on_recv);
    tcp_sent(newpcb, tcp_server_on_sent);
    tcp_err(newpcb, tcp_server_on_err);
    return ERR_OK;
}

int tcp_server_init(const tcp_server_config_t *config)
{
    memset(&g_server, 0, sizeof(g_server));
    g_server.config.port = TCP_SERVER_DEFAULT_PORT;
    g_server.config.auto_reconnect = true;
    g_server.status.state = TCP_SERVER_STATE_IDLE;

    if (config != NULL) {
        g_server.config = *config;
    }

    return 0;
}

int tcp_server_start(void)
{
    struct tcp_pcb *pcb;
    err_t err;

    if (g_server.listen_pcb != NULL) {
        return 0;
    }

    pcb = tcp_new_ip_type(IPADDR_TYPE_V4);
    if (pcb == NULL) {
        g_server.status.errors++;
        return -1;
    }

    err = tcp_bind(pcb, IP_ANY_TYPE, g_server.config.port);
    if (err != ERR_OK) {
        tcp_abort(pcb);
        g_server.status.errors++;
        return -1;
    }

    g_server.listen_pcb = tcp_listen_with_backlog(pcb, 1);
    if (g_server.listen_pcb == NULL) {
        g_server.status.errors++;
        return -1;
    }

    tcp_arg(g_server.listen_pcb, &g_server);
    tcp_accept(g_server.listen_pcb, tcp_server_on_accept);
    g_server.status.state = TCP_SERVER_STATE_LISTENING;
    return 0;
}

int tcp_server_stop(void)
{
    if (g_server.client_pcb != NULL) {
        tcp_arg(g_server.client_pcb, NULL);
        tcp_recv(g_server.client_pcb, NULL);
        tcp_sent(g_server.client_pcb, NULL);
        tcp_err(g_server.client_pcb, NULL);
        tcp_abort(g_server.client_pcb);
        g_server.client_pcb = NULL;
    }

    if (g_server.listen_pcb != NULL) {
        tcp_arg(g_server.listen_pcb, NULL);
        tcp_accept(g_server.listen_pcb, NULL);
        tcp_close(g_server.listen_pcb);
        g_server.listen_pcb = NULL;
    }

    g_server.status.state = TCP_SERVER_STATE_IDLE;
    return 0;
}

int tcp_server_send(const uint8_t *data, uint16_t len)
{
    err_t err;

    if (g_server.client_pcb == NULL || data == NULL || len == 0u) {
        return -1;
    }

    if ((g_server.client_pcb->flags & TF_RXCLOSED) != 0u) {
        g_server.status.errors++;
        return -1;
    }

    if (tcp_sndbuf(g_server.client_pcb) < len) {
        return 0;
    }

    err = tcp_write(g_server.client_pcb, data, len, TCP_WRITE_FLAG_COPY);
    if (err != ERR_OK) {
        g_server.status.errors++;
        return -1;
    }

    err = tcp_output(g_server.client_pcb);
    if (err != ERR_OK) {
        g_server.status.errors++;
        return -1;
    }

    return (int)len;
}

int tcp_server_recv(uint8_t *data, uint16_t max_len, uint32_t timeout_ms)
{
    uint16_t copied = 0u;
    (void)timeout_ms;

    if (data == NULL || max_len == 0u) {
        return -1;
    }

    while (copied < max_len && g_server.rx_tail != g_server.rx_head) {
        data[copied++] = g_server.rx_ring[g_server.rx_tail];
        g_server.rx_tail = (uint16_t)((g_server.rx_tail + 1u) % TCP_SERVER_RX_BUFFER_SIZE);
    }

    return (int)copied;
}

bool tcp_server_is_connected(void)
{
    return g_server.client_pcb != NULL;
}

void tcp_server_get_status(tcp_server_status_t *status)
{
    if (status != NULL) {
        *status = g_server.status;
    }
}

void *tcp_server_get_rx_stream(void)
{
    return NULL;
}

void *tcp_server_get_tx_stream(void)
{
    return NULL;
}

void tcp_server_task(void *argument)
{
    (void)argument;
}