Let us start here, from square one. No, from Zero!

api/resources/arduino/spiceapi/connection.h

@@ -0,0 +1,169 @@
+#ifndef SPICEAPI_CONNECTION_H
+#define SPICEAPI_CONNECTION_H
+
+#include <stdint.h>
+#include "rc4.h"
+
+#ifndef SPICEAPI_INTERFACE
+#define SPICEAPI_INTERFACE Serial
+#endif
+
+namespace spiceapi {
+
+    class Connection {
+    private:
+        uint8_t* receive_buffer;
+        size_t receive_buffer_size;
+        const char* password;
+        RC4* cipher;
+
+    public:
+        Connection(size_t receive_buffer_size, const char* password = "");
+        ~Connection();
+
+        void reset();
+
+        bool check();
+        void cipher_alloc(const char *session_key = nullptr);
+        void change_pass(const char* password, bool session = false);
+        const char* request(const char* json, size_t timeout = 1000);
+        const char* request(char* json, size_t timeout = 1000);
+    };
+}
+
+spiceapi::Connection::Connection(size_t receive_buffer_size, const char* password) {
+    this->receive_buffer = new uint8_t[receive_buffer_size];
+    this->receive_buffer_size = receive_buffer_size;
+    this->password = password;
+    this->cipher = nullptr;
+    this->reset();
+}
+
+spiceapi::Connection::~Connection() {
+
+    // clean up
+    if (this->cipher != nullptr)
+        delete this->cipher;
+}
+
+void spiceapi::Connection::reset() {
+
+    // drop all input
+    while (SPICEAPI_INTERFACE.available()) {
+        SPICEAPI_INTERFACE.read();
+    }
+
+#ifdef SPICEAPI_INTERFACE_WIFICLIENT
+    // reconnect TCP client
+    SPICEAPI_INTERFACE.stop();
+    this->check();
+#else
+    // 8 zeroes reset the password/session on serial
+    for (size_t i = 0; i < 8; i++) {
+        SPICEAPI_INTERFACE.write((int) 0);
+    }
+#endif
+
+    // reset password
+    this->cipher_alloc();
+}
+
+void spiceapi::Connection::cipher_alloc(const char *session_key) {
+
+    // delete old cipher
+    if (this->cipher != nullptr) {
+        delete this->cipher;
+        this->cipher = nullptr;
+    }
+
+    // create new cipher if password is set
+    session_key = session_key ? session_key : this->password;
+    if (strlen(session_key) > 0) {
+        this->cipher = new RC4(
+                (uint8_t *) session_key,
+                strlen(session_key));
+    }
+}
+
+bool spiceapi::Connection::check() {
+#ifdef SPICEAPI_INTERFACE_WIFICLIENT
+    if (!SPICEAPI_INTERFACE.connected()) {
+        return SPICEAPI_INTERFACE.connect(
+            SPICEAPI_INTERFACE_WIFICLIENT_HOST,
+            SPICEAPI_INTERFACE_WIFICLIENT_PORT);
+    } else {
+        return true;
+    }
+#else
+    // serial is always valid
+    return true;
+#endif
+}
+
+void spiceapi::Connection::change_pass(const char* password, bool session) {
+    if (!session) {
+        this->password = password;
+    }
+    this->cipher_alloc(password);
+}
+
+const char* spiceapi::Connection::request(const char* json, size_t timeout) {
+    auto json_len = strlen(json);
+    strncpy((char*) receive_buffer, json, receive_buffer_size);
+    return request((char*) receive_buffer, timeout);
+}
+
+const char* spiceapi::Connection::request(char* json_data, size_t timeout) {
+
+    // check connection
+    if (!this->check())
+        return "";
+
+    // crypt
+    auto json_len = strlen(json_data) + 1;
+    if (this->cipher != nullptr)
+        this->cipher->crypt((uint8_t*) json_data, json_len);
+
+    // send
+    auto send_result = SPICEAPI_INTERFACE.write((const char*) json_data, (int) json_len);
+    SPICEAPI_INTERFACE.flush();
+    if (send_result < (int) json_len) {
+        return "";
+    }
+
+    // receive
+    size_t receive_data_len = 0;
+    auto t_start = millis();
+    while (SPICEAPI_INTERFACE) {
+
+        // check for timeout
+        if (millis() - t_start > timeout) {
+            this->reset();
+            return "";
+        }
+
+        // read single byte
+        auto b = SPICEAPI_INTERFACE.read();
+        if (b < 0) continue;
+        receive_buffer[receive_data_len++] = b;
+
+        // check for buffer overflow
+        if (receive_data_len >= receive_buffer_size) {
+            this->reset();
+            return "";
+        }
+
+        // crypt
+        if (this->cipher != nullptr)
+            this->cipher->crypt(&receive_buffer[receive_data_len - 1], 1);
+
+        // check for message end
+        if (receive_buffer[receive_data_len - 1] == 0)
+            break;
+    }
+
+    // return resulting json
+    return (const char*) &receive_buffer[0];
+}
+
+#endif //SPICEAPI_CONNECTION_H