text: // Copyright 2018 Espressif Systems (Shanghai) PTE LTD
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  //
  //     http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an "AS IS" BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  
  
  #include <errno.h>
  #include <esp_log.h>
  #include <esp_err.h>
  #include <http_parser.h>
  
  #include <esp_http_server.h>
  #include "esp_httpd_priv.h"
  
  static const char *TAG = "httpd_uri";
  
  static bool httpd_uri_match_simple(const char *uri1, const char *uri2, size_t len2)
  {
      return strlen(uri1) == len2 &&          // First match lengths
          (strncmp(uri1, uri2, len2) == 0);   // Then match actual URIs
  }
  
  bool httpd_uri_match_wildcard(const char *template, const char *uri, size_t len)
  {
      const size_t tpl_len = strlen(template);
      size_t exact_match_chars = tpl_len;
  
      /* Check for trailing question mark and asterisk */
      const char last = (const char) (tpl_len > 0 ? template[tpl_len - 1] : 0);
      const char prevlast = (const char) (tpl_len > 1 ? template[tpl_len - 2] : 0);
      const bool asterisk = last == '*' || (prevlast == '*' && last == '?');
      const bool quest = last == '?' || (prevlast == '?' && last == '*');
  
      /* Minimum template string length must be:
       *      0 : if neither of '*' and '?' are present
       *      1 : if only '*' is present
       *      2 : if only '?' is present
       *      3 : if both are present
       *
       * The expression (asterisk + quest*2) serves as a
       * case wise generator of these length values
       */
  
      /* abort in cases such as "?" with no preceding character (invalid template) */
      if (exact_match_chars < asterisk + quest*2) {
          return false;
      }
  
      /* account for special characters and the optional character if "?" is used */
      exact_match_chars -= asterisk + quest*2;
  
      if (len < exact_match_chars) {
          return false;
      }
  
      if (!quest) {
          if (!asterisk && len != exact_match_chars) {
              /* no special characters and different length - strncmp would return false */
              return false;
          }
          /* asterisk allows arbitrary trailing characters, we ignore these using
           * exact_match_chars as the length limit */
          return (strncmp(template, uri, exact_match_chars) == 0);
      } else {
          /* question mark present */
          if (len > exact_match_chars && template[exact_match_chars] != uri[exact_match_chars]) {
              /* the optional character is present, but different */
              return false;
          }
          if (strncmp(template, uri, exact_match_chars) != 0) {
              /* the mandatory part differs */
              return false;
          }
          /* Now we know the URI is longer than the required part of template,
           * the mandatory part matches, and if the optional character is present, it is correct.
           * Match is OK if we have asterisk, i.e. any trailing characters are OK, or if
           * there are no characters beyond the optional character. */
          return asterisk || len <= exact_match_chars + 1;
      }
  }
  
  /* Find handler with matching URI and method, and set
   * appropriate error code if URI or method not found */
  static httpd_uri_t* httpd_find_uri_handler(struct httpd_data *hd,
                                             const char *uri, size_t uri_len,
                                             httpd_method_t method,
                                             httpd_err_code_t *err)
  {
      if (err) {
          *err = HTTPD_404_NOT_FOUND;
      }
  
      for (int i = 0; i < hd->config.max_uri_handlers; i++) {
          if (!hd->hd_calls[i]) {
              break;
          }
          ESP_LOGD(TAG, LOG_FMT("[%d] = %s"), i, hd->hd_calls[i]->uri);
  
          /* Check if custom URI matching function is set,
           * else use simple string compare */
          if (hd->config.uri_match_fn ?
              hd->config.uri_match_fn(hd->hd_calls[i]->uri, uri, uri_len) :
              httpd_uri_match_simple(hd->hd_calls[i]->uri, uri, uri_len)) {
              /* URIs match. Now check if method is supported */
              if (hd->hd_calls[i]->method == method) {
                  /* Match found! */
                  if (err) {
                      /* Unset any error that may
                       * have been set earlier */
                      *err = 0;
                  }
                  return hd->hd_calls[i];
              }
              /* URI found but method not allowed.
               * If URI is found later then this
               * error must be set to 0 */
              if (err) {
                  *err = HTTPD_405_METHOD_NOT_ALLOWED;
              }
          }
      }
      return NULL;
  }
  
  esp_err_t httpd_register_uri_handler(httpd_handle_t handle,
                                       const httpd_uri_t *uri_handler)
  {
      if (handle == NULL || uri_handler == NULL) {
          return ESP_ERR_INVALID_ARG;
      }
  
      struct httpd_data *hd = (struct httpd_data *) handle;
  
      /* Make sure another handler with matching URI and method
       * is not already registered. This will also catch cases
       * when a registered URI wildcard pattern already accounts
       * for the new URI being registered */
      if (httpd_find_uri_handler(handle, uri_handler->uri,
                                 strlen(uri_handler->uri),
                                 uri_handler->method, NULL) != NULL) {
          ESP_LOGW(TAG, LOG_FMT("handler %s with method %d already registered"),
                   uri_handler->uri, uri_handler->method);
          return ESP_ERR_HTTPD_HANDLER_EXISTS;
      }
  
      for (int i = 0; i < hd->config.max_uri_handlers; i++) {
          if (hd->hd_calls[i] == NULL) {
              hd->hd_calls[i] = malloc(sizeof(httpd_uri_t));
              if (hd->hd_calls[i] == NULL) {
                  /* Failed to allocate memory */
                  return ESP_ERR_HTTPD_ALLOC_MEM;
              }
  
              /* Copy URI string */
              hd->hd_calls[i]->uri = strdup(uri_handler->uri);
              if (hd->hd_calls[i]->uri == NULL) {
                  /* Failed to allocate memory */
                  free(hd->hd_calls[i]);
                  return ESP_ERR_HTTPD_ALLOC_MEM;
              }
  
              /* Copy remaining members */
              hd->hd_calls[i]->method   = uri_handler->method;
              hd->hd_calls[i]->handler  = uri_handler->handler;
              hd->hd_calls[i]->user_ctx = uri_handler->user_ctx;
  #ifdef CONFIG_HTTPD_WS_SUPPORT
              hd->hd_calls[i]->is_websocket = uri_handler->is_websocket;
              hd->hd_calls[i]->handle_ws_control_frames = uri_handler->handle_ws_control_frames;
  #endif
              ESP_LOGD(TAG, LOG_FMT("[%d] installed %s"), i, uri_handler->uri);
              return ESP_OK;
          }
          ESP_LOGD(TAG, LOG_FMT("[%d] exists %s"), i, hd->hd_calls[i]->uri);
      }
      ESP_LOGW(TAG, LOG_FMT("no slots left for registering handler"));
      return ESP_ERR_HTTPD_HANDLERS_FULL;
  }
  
  esp_err_t httpd_unregister_uri_handler(httpd_handle_t handle,
                                         const char *uri, httpd_method_t method)
  {
      if (handle == NULL || uri == NULL) {
          return ESP_ERR_INVALID_ARG;
      }
  
      struct httpd_data *hd = (struct httpd_data *) handle;
      for (int i = 0; i < hd->config.max_uri_handlers; i++) {
          if (!hd->hd_calls[i]) {
              break;
          }
          if ((hd->hd_calls[i]->method == method) &&       // First match methods
              (strcmp(hd->hd_calls[i]->uri, uri) == 0)) {  // Then match URI string
              ESP_LOGD(TAG, LOG_FMT("[%d] removing %s"), i, hd->hd_calls[i]->uri);
  
              free((char*)hd->hd_calls[i]->uri);
              free(hd->hd_calls[i]);
              hd->hd_calls[i] = NULL;
  
              /* Shift the remaining non null handlers in the array
               * forward by 1 so that order of insertion is maintained */
              for (i += 1; i < hd->config.max_uri_handlers; i++) {
                  if (!hd->hd_calls[i]) {
                      break;
                  }
                  hd->hd_calls[i-1] = hd->hd_calls[i];
              }
              /* Nullify the following non null entry */
              hd->hd_calls[i-1] = NULL;
              return ESP_OK;
          }
      }
      ESP_LOGW(TAG, LOG_FMT("handler %s with method %d not found"), uri, method);
      return ESP_ERR_NOT_FOUND;
  }
  
  esp_err_t httpd_unregister_uri(httpd_handle_t handle, const char *uri)
  {
      if (handle == NULL || uri == NULL) {
          return ESP_ERR_INVALID_ARG;
      }
  
      struct httpd_data *hd = (struct httpd_data *) handle;
      bool found = false;
  
      int i = 0, j = 0; // For keeping count of removed entries
      for (; i < hd->config.max_uri_handlers; i++) {
          if (!hd->hd_calls[i]) {
              break;
          }
          if (strcmp(hd->hd_calls[i]->uri, uri) == 0) {   // Match URI strings
              ESP_LOGD(TAG, LOG_FMT("[%d] removing %s"), i, uri);
  
              free((char*)hd->hd_calls[i]->uri);
              free(hd->hd_calls[i]);
              hd->hd_calls[i] = NULL;
              found = true;
  
              j++; // Update count of removed entries
          } else {
              /* Shift the remaining non null handlers in the array
               * forward by j so that order of insertion is maintained */
              hd->hd_calls[i-j] = hd->hd_calls[i];
          }
      }
      /* Nullify the following non null entries */
      for (int k = (i - j); k < i; k++) {
          hd->hd_calls[k] = NULL;
      }
  
      if (!found) {
          ESP_LOGW(TAG, LOG_FMT("no handler found for URI %s"), uri);
      }
      return (found ? ESP_OK : ESP_ERR_NOT_FOUND);
  }
  
  void httpd_unregister_all_uri_handlers(struct httpd_data *hd)
  {
      for (unsigned i = 0; i < hd->config.max_uri_handlers; i++) {
          if (!hd->hd_calls[i]) {
              break;
          }
          ESP_LOGD(TAG, LOG_FMT("[%d] removing %s"), i, hd->hd_calls[i]->uri);
  
          free((char*)hd->hd_calls[i]->uri);
          free(hd->hd_calls[i]);
          hd->hd_calls[i] = NULL;
      }
  }
  
  esp_err_t httpd_uri(struct httpd_data *hd)
  {
      httpd_uri_t            *uri = NULL;
      httpd_req_t            *req = &hd->hd_req;
      struct http_parser_url *res = &hd->hd_req_aux.url_parse_res;
  
      /* For conveying URI not found/method not allowed */
      httpd_err_code_t err = 0;
  
      ESP_LOGD(TAG, LOG_FMT("request for %s with type %d"), req->uri, req->method);
  
      /* URL parser result contains offset and length of path string */
      if (res->field_set & (1 << UF_PATH)) {
          uri = httpd_find_uri_handler(hd, req->uri + res->field_data[UF_PATH].off,
                                       res->field_data[UF_PATH].len, req->method, &err);
      }
  
      /* If URI with method not found, respond with error code */
      if (uri == NULL) {
          switch (err) {
              case HTTPD_404_NOT_FOUND:
                  ESP_LOGW(TAG, LOG_FMT("URI '%s' not found"), req->uri);
                  return httpd_req_handle_err(req, HTTPD_404_NOT_FOUND);
              case HTTPD_405_METHOD_NOT_ALLOWED:
                  ESP_LOGW(TAG, LOG_FMT("Method '%d' not allowed for URI '%s'"),
                           req->method, req->uri);
                  return httpd_req_handle_err(req, HTTPD_405_METHOD_NOT_ALLOWED);
              default:
                  return ESP_FAIL;
          }
      }
  
      /* Attach user context data (passed during URI registration) into request */
      req->user_ctx = uri->user_ctx;
  
      /* Final step for a WebSocket handshake verification */
  #ifdef CONFIG_HTTPD_WS_SUPPORT
      struct httpd_req_aux   *aux = req->aux;
      if (uri->is_websocket && aux->ws_handshake_detect && uri->method == HTTP_GET) {
          ESP_LOGD(TAG, LOG_FMT("Responding WS handshake to sock %d"), aux->sd->fd);
          esp_err_t ret = httpd_ws_respond_server_handshake(&hd->hd_req);
          if (ret != ESP_OK) {
              return ret;
          }
  
          aux->sd->ws_handshake_done = true;
          aux->sd->ws_handler = uri->handler;
          aux->sd->ws_control_frames = uri->handle_ws_control_frames;
  
          /* Return immediately after handshake, no need to call handler here */
          return ESP_OK;
      }
  #endif
  
      /* Invoke handler */
      if (uri->handler(req) != ESP_OK) {
          /* Handler returns error, this socket should be closed */
          ESP_LOGW(TAG, LOG_FMT("uri handler execution failed"));
          return ESP_FAIL;
      }
      return ESP_OK;
  }
  