#include "coap3/coap_internal.h"

#include "coap_fuzz_helper.h"

#include <stdint.h>

#include <string.h>

#include <stdlib.h>

static int

fuzz_event_handler(coap_session_t *session, const coap_event_t event) {

  (void)session;

  (void)event;

  return 0;

}

/* Resource handler - exercises coap_add_data_large_response() */

static void

block_handler(coap_resource_t *resource, coap_session_t *session,

              const coap_pdu_t *request, const coap_string_t *query,

              coap_pdu_t *response) {

  (void)query;

  size_t len;

  const uint8_t *databuf;

  response->code = COAP_RESPONSE_CODE(205);

  if (coap_get_data(request, &len, &databuf) && len > 64) {

    /* Large payload - use block transfer API */

    coap_add_data_large_response(resource, session, request, response,

                                 query, COAP_MEDIATYPE_TEXT_PLAIN, -1, 0,

                                 len, databuf, NULL, NULL);

  } else if (len > 0) {

    coap_add_data(response, len, databuf);

  } else {

    /* Generate 256-byte response to trigger BLOCK2 */

    static const uint8_t large_data[256] = {

      '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F',

      '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F',

      '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F',

      '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F',

      '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F',

      '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F',

      '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F',

      '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F',

      '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F',

      '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F',

      '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F',

      '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F',

      '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F',

      '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F',

      '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F',

      '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'

    };

    coap_add_data_large_response(resource, session, request, response,

                                 query, COAP_MEDIATYPE_TEXT_PLAIN, -1, 0,

                                 sizeof(large_data), large_data, NULL,

                                 NULL);

  }

}

int

LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {

  coap_context_t *ctx = NULL;

  coap_session_t *session = NULL;

  coap_resource_t *resource = NULL;

  coap_address_t addr;

  if (size < 8)

    return 0;

  coap_startup();

  coap_set_log_level(COAP_LOG_EMERG);

  coap_debug_set_packet_loss("50%");

  coap_debug_set_packet_fail("100%");

  ctx = coap_new_context(NULL);

  if (!ctx)

    goto cleanup;

  coap_register_event_handler(ctx, fuzz_event_handler);

  /* Configure block mode and max block size */

  uint32_t block_mode = ((uint32_t)data[0] << 8) | data[1];

  coap_context_set_block_mode(ctx, block_mode & 0x0F);

  uint16_t max_block = ((uint16_t)data[2] << 8) | data[3];

  if (max_block >= 16 && max_block <= 1024) {

    coap_context_set_max_block_size(ctx, max_block);

  }

  /* Create resource with type and interface attributes */

  resource = coap_resource_init(coap_make_str_const("data"), 0);

  if (resource) {

    coap_register_request_handler(resource, COAP_REQUEST_GET, block_handler);

    coap_register_request_handler(resource, COAP_REQUEST_PUT, block_handler);

    coap_register_request_handler(resource, COAP_REQUEST_POST, block_handler);

    coap_add_attr(resource, coap_make_str_const("rt"),

                  coap_make_str_const("\"test\""), 0);

    coap_add_attr(resource, coap_make_str_const("if"),

                  coap_make_str_const("\"block\""), 0);

    coap_add_resource(ctx, resource);

  }

  /* Create session */

  coap_address_init(&addr);

  addr.addr.sa.sa_family = AF_INET;

  session = coap_new_client_session(ctx, NULL, &addr, COAP_PROTO_UDP);

  if (!session)

    goto cleanup;

  session->state = COAP_SESSION_STATE_ESTABLISHED;

  /* Dispatch with programmatic PDU and raw wire format */

  coap_fuzz_dispatch(ctx, session, data, size, (const uint8_t *)"data", 4);

  /* Probe .well-known/core with a fuzz-derived query filter */

  {

    coap_pdu_t *wk = coap_pdu_init(COAP_MESSAGE_CON, COAP_REQUEST_CODE_GET,

                                   coap_new_message_id(session),

                                   coap_session_max_pdu_size(session));

    if (wk) {

      coap_add_option(wk, COAP_OPTION_URI_PATH, 11,

                      (const uint8_t *)".well-known");

      coap_add_option(wk, COAP_OPTION_URI_PATH, 4,

                      (const uint8_t *)"core");

      uint8_t qlen = (data[4] % 16) + 1;

      if ((size_t)5 + qlen <= size)

        coap_add_option(wk, COAP_OPTION_URI_QUERY, qlen, data + 5);

      coap_lock_lock(goto cleanup);

      coap_dispatch(ctx, session, wk);

      coap_lock_unlock();

      coap_delete_pdu(wk);

    }

  }

cleanup:

  if (session)

    coap_session_release(session);

  if (ctx)

    coap_free_context(ctx);

  coap_cleanup();

  return 0;

}