/* BSD Socket API Example

   This example code is in the Public Domain (or CC0 licensed, at your option.)

   Unless required by applicable law or agreed to in writing, this
   software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
   CONDITIONS OF ANY KIND, either express or implied.
*/
#include <string.h>
#include <sys/param.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "esp_system.h"
#include "esp_wifi.h"
#include "esp_event.h"
#include "esp_log.h"
#include "nvs_flash.h"
#include "esp_netif.h"
#include "protocol_examples_common.h"

#include "lwip/err.h"
#include "lwip/sockets.h"
#include "lwip/sys.h"
#include <lwip/netdb.h>


#define PORT CONFIG_EXAMPLE_PORT

static const char *TAG = "example";

static void do_retransmit(const int sock)
{
    int len;
    char rx_buffer[128];

    do {
        len = recv(sock, rx_buffer, sizeof(rx_buffer) - 1, 0);
        if (len < 0) {
            ESP_LOGE(TAG, "Error occurred during receiving: errno %d", errno);
        } else if (len == 0) {
            ESP_LOGW(TAG, "Connection closed");
        } else {
            rx_buffer[len] = 0; // Null-terminate whatever is received and treat it like a string
            ESP_LOGI(TAG, "Received %d bytes: %s", len, rx_buffer);

            // send() can return less bytes than supplied length.
            // Walk-around for robust implementation. 
            int to_write = len;
            while (to_write > 0) {
                int written = send(sock, rx_buffer + (len - to_write), to_write, 0);
                if (written < 0) {
                    ESP_LOGE(TAG, "Error occurred during sending: errno %d", errno);
                }
                to_write -= written;
            }
        }
    } while (len > 0);
}

static void tcp_server_task(void *pvParameters)
{
    char addr_str[128];
    int addr_family;
    int ip_protocol;


#ifdef CONFIG_EXAMPLE_IPV4
    struct sockaddr_in dest_addr;
    dest_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    dest_addr.sin_family = AF_INET;
    dest_addr.sin_port = htons(PORT);
    addr_family = AF_INET;
    ip_protocol = IPPROTO_IP;
    inet_ntoa_r(dest_addr.sin_addr, addr_str, sizeof(addr_str) - 1);
#else // IPV6
    struct sockaddr_in6 dest_addr;
    bzero(&dest_addr.sin6_addr.un, sizeof(dest_addr.sin6_addr.un));
    dest_addr.sin6_family = AF_INET6;
    dest_addr.sin6_port = htons(PORT);
    addr_family = AF_INET6;
    ip_protocol = IPPROTO_IPV6;
    inet6_ntoa_r(dest_addr.sin6_addr, addr_str, sizeof(addr_str) - 1);
#endif

    int listen_sock = socket(addr_family, SOCK_STREAM, ip_protocol);
    if (listen_sock < 0) {
        ESP_LOGE(TAG, "Unable to create socket: errno %d", errno);
        vTaskDelete(NULL);
        return;
    }
    ESP_LOGI(TAG, "Socket created");

    int err = bind(listen_sock, (struct sockaddr *)&dest_addr, sizeof(dest_addr));
    if (err != 0) {
        ESP_LOGE(TAG, "Socket unable to bind: errno %d", errno);
        goto CLEAN_UP;
    }
    ESP_LOGI(TAG, "Socket bound, port %d", PORT);

    err = listen(listen_sock, 1);
    if (err != 0) {
        ESP_LOGE(TAG, "Error occurred during listen: errno %d", errno);
        goto CLEAN_UP;
    }

    while (1) {

        ESP_LOGI(TAG, "Socket listening");

        struct sockaddr_in6 source_addr; // Large enough for both IPv4 or IPv6
        uint addr_len = sizeof(source_addr);
        int sock = accept(listen_sock, (struct sockaddr *)&source_addr, &addr_len);
        if (sock < 0) {
            ESP_LOGE(TAG, "Unable to accept connection: errno %d", errno);
            break;
        }

        // Convert ip address to string
        if (source_addr.sin6_family == PF_INET) {
            inet_ntoa_r(((struct sockaddr_in *)&source_addr)->sin_addr.s_addr, addr_str, sizeof(addr_str) - 1);
        } else if (source_addr.sin6_family == PF_INET6) {
            inet6_ntoa_r(source_addr.sin6_addr, addr_str, sizeof(addr_str) - 1);
        }
        ESP_LOGI(TAG, "Socket accepted ip address: %s", addr_str);

        do_retransmit(sock);

        shutdown(sock, 0);
        close(sock);
    }

CLEAN_UP:
    close(listen_sock);
    vTaskDelete(NULL);
}

void app_main(void)
{
    ESP_ERROR_CHECK(nvs_flash_init());
    ESP_ERROR_CHECK(esp_netif_init());
    ESP_ERROR_CHECK(esp_event_loop_create_default());

    /* This helper function configures Wi-Fi or Ethernet, as selected in menuconfig.
     * Read "Establishing Wi-Fi or Ethernet Connection" section in
     * examples/protocols/README.md for more information about this function.
     */
    ESP_ERROR_CHECK(example_connect());

    xTaskCreate(tcp_server_task, "tcp_server", 4096, NULL, 5, NULL);
}