/* CoAP server 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.
*/

/*
 * WARNING
 * libcoap is not multi-thread safe, so only this thread must make any coap_*()
 * calls.  Any external (to this thread) data transmitted in/out via libcoap
 * therefore has to be passed in/out by xQueue*() via this thread.
 */

#include <string.h>
#include <sys/socket.h>

#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/event_groups.h"

#include "esp_log.h"
#include "esp_wifi.h"
#include "esp_event.h"

#include "nvs_flash.h"

#include "protocol_examples_common.h"

#if 1
/* Needed until coap_dtls.h becomes a part of libcoap proper */
#include "libcoap.h"
#include "coap_dtls.h"
#endif
#include "coap.h"

/* The examples use simple Pre-Shared-Key configuration that you can set via
   'make menuconfig'.

   If you'd rather not, just change the below entries to strings with
   the config you want - ie #define EXAMPLE_COAP_PSK_KEY "some-agreed-preshared-key"

   Note: PSK will only be used if the URI is prefixed with coaps://
   instead of coap:// and the PSK must be one that the server supports
   (potentially associated with the IDENTITY)
*/
#define EXAMPLE_COAP_PSK_KEY CONFIG_COAP_PSK_KEY

/* The examples use CoAP Logging Level that
   you can set via 'make menuconfig'.

   If you'd rather not, just change the below entry to a value
   that is between 0 and 7 with
   the config you want - ie #define EXAMPLE_COAP_LOG_DEFAULT_LEVEL 7
*/
#define EXAMPLE_COAP_LOG_DEFAULT_LEVEL CONFIG_COAP_LOG_DEFAULT_LEVEL

static char espressif_data[100];
static int espressif_data_len = 0;

#define INITIAL_DATA "Hello World!"

/*
 * The resource handler
 */
static void
hnd_espressif_get(coap_context_t *ctx, coap_resource_t *resource,
                  coap_session_t *session,
                  coap_pdu_t *request, coap_binary_t *token,
                  coap_string_t *query, coap_pdu_t *response)
{
    coap_add_data_blocked_response(resource, session, request, response, token,
                                   COAP_MEDIATYPE_TEXT_PLAIN, 0,
                                   (size_t)espressif_data_len,
                                   (const u_char *)espressif_data);
}

static void
hnd_espressif_put(coap_context_t *ctx,
                  coap_resource_t *resource,
                  coap_session_t *session,
                  coap_pdu_t *request,
                  coap_binary_t *token,
                  coap_string_t *query,
                  coap_pdu_t *response)
{
    size_t size;
    unsigned char *data;

    coap_resource_notify_observers(resource, NULL);

    if (strcmp (espressif_data, INITIAL_DATA) == 0) {
        response->code = COAP_RESPONSE_CODE(201);
    }
    else {
        response->code = COAP_RESPONSE_CODE(204);
    }

    /* coap_get_data() sets size to 0 on error */
    (void)coap_get_data(request, &size, &data);

    if (size == 0) {      /* re-init */
        snprintf(espressif_data, sizeof(espressif_data), INITIAL_DATA);
        espressif_data_len = strlen(espressif_data);
    } else {
        espressif_data_len = size > sizeof (espressif_data) ? sizeof (espressif_data) : size;
        memcpy (espressif_data, data, espressif_data_len);
    }
}

static void
hnd_espressif_delete(coap_context_t *ctx,
                     coap_resource_t *resource,
                     coap_session_t *session,
                     coap_pdu_t *request,
                     coap_binary_t *token,
                     coap_string_t *query,
                     coap_pdu_t *response)
{
    coap_resource_notify_observers(resource, NULL);
    snprintf(espressif_data, sizeof(espressif_data), INITIAL_DATA);
    espressif_data_len = strlen(espressif_data);
    response->code = COAP_RESPONSE_CODE(202);
}

#ifdef CONFIG_MBEDTLS_COAP_PKI

#ifdef __GNUC__
#define UNUSED_PARAM __attribute__ ((unused))
#else /* not a GCC */
#define UNUSED_PARAM
#endif /* GCC */

#ifndef min
#define min(a,b) ((a) < (b) ? (a) : (b))
#endif

static int
verify_cn_callback(const char *cn,
                   const uint8_t *asn1_public_cert UNUSED_PARAM,
                   size_t asn1_length UNUSED_PARAM,
                   coap_session_t *session UNUSED_PARAM,
                   unsigned depth,
                   int validated UNUSED_PARAM,
                   void *arg UNUSED_PARAM
) {
  coap_log(LOG_INFO, "CN '%s' presented by server (%s)\n",
           cn, depth ? "CA" : "Certificate");
  return 1;
}
#endif /* CONFIG_MBEDTLS_COAP_PKI */

static void coap_example_server(void *p)
{
    coap_context_t *ctx = NULL;
    coap_address_t serv_addr;
    coap_resource_t *resource = NULL;

    snprintf(espressif_data, sizeof(espressif_data), INITIAL_DATA);
    espressif_data_len = strlen(espressif_data);
    coap_set_log_level(EXAMPLE_COAP_LOG_DEFAULT_LEVEL);

    while (1) {
        coap_endpoint_t *ep = NULL;
        unsigned wait_ms;

        /* Prepare the CoAP server socket */
        coap_address_init(&serv_addr);
        serv_addr.addr.sin.sin_family      = AF_INET;
        serv_addr.addr.sin.sin_addr.s_addr = INADDR_ANY;
        serv_addr.addr.sin.sin_port        = htons(COAP_DEFAULT_PORT);

        ctx = coap_new_context(NULL);
        if (!ctx) {
           continue;
        }
#ifdef CONFIG_MBEDTLS_COAP_PSK
        /* Need PSK setup before we set up endpoints */
        coap_context_set_psk(ctx, "CoAP",
                             (const uint8_t*)EXAMPLE_COAP_PSK_KEY,
                             sizeof(EXAMPLE_COAP_PSK_KEY)-1);
#endif /* CONFIG_MBEDTLS_COAP_PSK */

#ifdef CONFIG_MBEDTLS_COAP_PKI
/* CA cert, taken from coap_ca.pem
   Server cert, taken from coap_server.crt
   Server key, taken from coap_server.key

   The PEM, CRT and KEY file are examples taken from the wpa2 enterprise
   example.

   To embed it in the app binary, the PEM, CRT and KEY file is named
   in the component.mk COMPONENT_EMBED_TXTFILES variable.
*/
extern uint8_t ca_pem_start[] asm("_binary_coap_ca_pem_start");
extern uint8_t ca_pem_end[]   asm("_binary_coap_ca_pem_end");
extern uint8_t server_crt_start[] asm("_binary_coap_server_crt_start");
extern uint8_t server_crt_end[]   asm("_binary_coap_server_crt_end");
extern uint8_t server_key_start[] asm("_binary_coap_server_key_start");
extern uint8_t server_key_end[]   asm("_binary_coap_server_key_end");
            unsigned int ca_pem_bytes = ca_pem_end - ca_pem_start;
            unsigned int server_crt_bytes = server_crt_end - server_crt_start;
            unsigned int server_key_bytes = server_key_end - server_key_start;
            coap_dtls_pki_t dtls_pki;

            memset (&dtls_pki, 0, sizeof(dtls_pki));
            dtls_pki.version = COAP_DTLS_PKI_SETUP_VERSION;
            if (ca_pem_bytes) {
                /*
                 * Add in additional certificate checking.
                 * This list of enabled can be tuned for the specific
                 * requirements - see 'man coap_encryption'.
                 *
                 * Note: A list of root ca file can be setup separately using
                 * coap_context_set_pki_root_cas(), but the below is used to
                 * define what checking actually takes place.
                 */
                dtls_pki.verify_peer_cert        = 1;
                dtls_pki.require_peer_cert       = 1;
                dtls_pki.allow_self_signed       = 1;
                dtls_pki.allow_expired_certs     = 1;
                dtls_pki.cert_chain_validation   = 1;
                dtls_pki.cert_chain_verify_depth = 2;
                dtls_pki.check_cert_revocation   = 1;
                dtls_pki.allow_no_crl            = 1;
                dtls_pki.allow_expired_crl       = 1;
                dtls_pki.allow_bad_md_hash       = 1;
                dtls_pki.allow_short_rsa_length  = 1;
                dtls_pki.validate_cn_call_back   = verify_cn_callback;
                dtls_pki.cn_call_back_arg        = NULL;
                dtls_pki.validate_sni_call_back  = NULL;
                dtls_pki.sni_call_back_arg       = NULL;
            }
            dtls_pki.pki_key.key_type = COAP_PKI_KEY_PEM_BUF;
            dtls_pki.pki_key.key.pem_buf.public_cert = server_crt_start;
            dtls_pki.pki_key.key.pem_buf.public_cert_len = server_crt_bytes;
            dtls_pki.pki_key.key.pem_buf.private_key = server_key_start;
            dtls_pki.pki_key.key.pem_buf.private_key_len = server_key_bytes;
            dtls_pki.pki_key.key.pem_buf.ca_cert = ca_pem_start;
            dtls_pki.pki_key.key.pem_buf.ca_cert_len = ca_pem_bytes;

            coap_context_set_pki(ctx, &dtls_pki);
#endif /* CONFIG_MBEDTLS_COAP_PKI */

        ep = coap_new_endpoint(ctx, &serv_addr, COAP_PROTO_UDP);
        if (!ep) {
           goto clean_up;
        }
        ep = coap_new_endpoint(ctx, &serv_addr, COAP_PROTO_TCP);
        if (!ep) {
           goto clean_up;
        }
#if defined(CONFIG_MBEDTLS_COAP_PSK) || defined(CONFIG_MBEDTLS_COAP_PKI)
	if (coap_dtls_is_supported()) {
            serv_addr.addr.sin.sin_port = htons(COAPS_DEFAULT_PORT);
            ep = coap_new_endpoint(ctx, &serv_addr, COAP_PROTO_DTLS);
            if (!ep) {
               goto clean_up;
            }
        }
#endif /* CONFIG_MBEDTLS_COAP_PSK CONFIG_MBEDTLS_COAP_PKI */
        resource = coap_resource_init(coap_make_str_const("Espressif"), 0);
        if (!resource) {
           goto clean_up;
        }
        coap_register_handler(resource, COAP_REQUEST_GET, hnd_espressif_get);
        coap_register_handler(resource, COAP_REQUEST_PUT, hnd_espressif_put);
        coap_register_handler(resource, COAP_REQUEST_DELETE, hnd_espressif_delete);
        /* We possibly want to Observe the GETs */
        coap_resource_set_get_observable(resource, 1);
        coap_add_resource(ctx, resource);

        wait_ms = COAP_RESOURCE_CHECK_TIME * 1000;

        while (1) {
            int result = coap_run_once(ctx, wait_ms);
            if (result < 0) {
                break;
            } else if (result && (unsigned)result < wait_ms) {
                /* decrement if there is a result wait time returned */
                wait_ms -= result;
            }
            if (result) {
                /* result must have been >= wait_ms, so reset wait_ms */
                wait_ms = COAP_RESOURCE_CHECK_TIME * 1000;
            }
        }
    }
clean_up:
    coap_free_context(ctx);
    coap_cleanup();

    vTaskDelete(NULL);
}

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

#if 0
/* See https://github.com/Ebiroll/qemu_esp32 for further information */
#include "emul_ip.h"
    if (is_running_qemu()) {
        xTaskCreate(task_lwip_init, "task_lwip_init", 2*4096, NULL, 20, NULL); 
    }
    else
#endif
    /* 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(coap_example_server, "coap", 8 * 1024, NULL, 5, NULL);
}