Adding path arguments to WebServer (#1994)

libraries/WebServer/examples/PathArgServer/PathArgServer.ino

+#include <WiFi.h>
+#include <WiFiClient.h>
+#include <WebServer.h>
+#include <ESPmDNS.h>
+
+const char *ssid = "........";
+const char *password = "........";
+
+WebServer server(80);
+
+void setup(void) {
+  Serial.begin(9600);
+  WiFi.mode(WIFI_STA);
+  WiFi.begin(ssid, password);
+  Serial.println("");
+
+  // Wait for connection
+  while (WiFi.status() != WL_CONNECTED) {
+    delay(500);
+    Serial.print(".");
+  }
+  Serial.println("");
+  Serial.print("Connected to ");
+  Serial.println(ssid);
+  Serial.print("IP address: ");
+  Serial.println(WiFi.localIP());
+
+  if (MDNS.begin("esp32")) {
+    Serial.println("MDNS responder started");
+  }
+
+  server.on("/", []() {
+    server.send(200, "text/plain", "hello from esp32!");
+  });
+
+  server.on("/users/{}", []() {
+    String user = server.pathArg(0);
+    server.send(200, "text/plain", "User: '" + user + "'");
+  });
+  
+  server.on("/users/{}/devices/{}", []() {
+    String user = server.pathArg(0);
+    String device = server.pathArg(1);
+    server.send(200, "text/plain", "User: '" + user + "' and Device: '" + device + "'");
+  });
+
+  server.begin();
+  Serial.println("HTTP server started");
+}
+
+void loop(void) {
+  server.handleClient();
+}

libraries/WebServer/src/WebServer.cpp

@@ -509,6 +509,11 @@ void WebServer::_streamFileCore(const size_t fileSize, const String & fileName,
   send(200, contentType, "");
 }
 
+String WebServer::pathArg(unsigned int i) { 
+  if (_currentHandler != nullptr)
+    return _currentHandler->pathArg(i);
+  return "";
+}
 
 String WebServer::arg(String name) {
   for (int j = 0; j < _postArgsLen; ++j) {

libraries/WebServer/src/WebServer.h

@@ -97,6 +97,7 @@ public:
   virtual WiFiClient client() { return _currentClient; }
   HTTPUpload& upload() { return *_currentUpload; }
 
+  String pathArg(unsigned int i); // get request path argument by number
   String arg(String name);        // get request argument value by name
   String arg(int i);              // get request argument value by number
   String argName(int i);          // get request argument name by number

libraries/WebServer/src/detail/RequestHandler.h

 #ifndef REQUESTHANDLER_H
 #define REQUESTHANDLER_H
 
+#include <vector>
+#include <assert.h>
+
 class RequestHandler {
 public:
     virtual ~RequestHandler() { }
@@ -14,6 +17,15 @@ public:
 
 private:
     RequestHandler* _next = nullptr;
+
+protected:
+    std::vector<String> pathArgs;
+
+public:
+    const String& pathArg(unsigned int i) { 
+        assert(i < pathArgs.size());
+        return pathArgs[i];
+    }
 };
 
 #endif //REQUESTHANDLER_H

libraries/WebServer/src/detail/RequestHandlersImpl.h

@@ -15,16 +15,55 @@ public:
     , _uri(uri)
     , _method(method)
     {
+        int numParams = 0, start = 0;
+        do {
+            start = _uri.indexOf("{}", start);
+            if (start > 0) {
+                numParams++;
+                start += 2;
+            }
+        } while (start > 0);
+        pathArgs.resize(numParams);
     }
 
     bool canHandle(HTTPMethod requestMethod, String requestUri) override  {
         if (_method != HTTP_ANY && _method != requestMethod)
             return false;
 
-        if (requestUri != _uri)
+        if (_uri == requestUri)
+            return true;
+
+        size_t uriLength = _uri.length();
+        unsigned int pathArgIndex = 0;
+        unsigned int requestUriIndex = 0;
+        for (unsigned int i = 0; i < uriLength; i++, requestUriIndex++) {
+            char uriChar = _uri[i];
+            char requestUriChar = requestUri[requestUriIndex];
+
+            if (uriChar == requestUriChar)
+                continue;
+            if (uriChar != '{')
                 return false;
 
-        return true;
+            i += 2; // index of char after '}'
+            if (i >= uriLength) {
+                // there is no char after '}'
+                pathArgs[pathArgIndex] = requestUri.substring(requestUriIndex);
+                return pathArgs[pathArgIndex].indexOf("/") == -1; // path argument may not contain a '/'
+            }
+            else
+            {
+                char charEnd = _uri[i];
+                int uriIndex = requestUri.indexOf(charEnd, requestUriIndex);
+                if (uriIndex < 0)
+                    return false;
+                pathArgs[pathArgIndex] = requestUri.substring(requestUriIndex, uriIndex);
+                requestUriIndex = (unsigned int) uriIndex;
+            }
+            pathArgIndex++;
+        }
+
+        return requestUriIndex >= requestUri.length();
     }
 
     bool canUpload(String requestUri) override  {