/*!
 * @file Adafruit_UBX.h
 * 
 * Arduino library for parsing UBX protocol from u-blox GPS/RTK modules.
 * 
 * This library can use any Stream object as input (UART, DDC, or other).
 * 
 * Adafruit invests time and resources providing this open source code,
 * please support Adafruit and open-source hardware by purchasing
 * products from Adafruit!
 *
 * Written by Your Name for Project Name.
 * 
 * MIT license, all text here must be included in any redistribution.
 */

#ifndef ADAFRUIT_UBX_H
#define ADAFRUIT_UBX_H

#include <Arduino.h>
#include <Stream.h>
#include "Adafruit_uBlox_typedef.h"

// UBX protocol constants
#define UBX_SYNC_CHAR_1 0xB5 // First UBX protocol sync char (µ)
#define UBX_SYNC_CHAR_2 0x62 // Second UBX protocol sync char (b)
// UBX ACK Message IDs
#define UBX_ACK_NAK 0x00     // Message Not Acknowledged
#define UBX_ACK_ACK 0x01     // Message Acknowledged

// Callback function type for UBX messages - defined at global scope so other classes can use it
typedef void (*UBXMessageCallback)(uint8_t msgClass, uint8_t msgId, uint16_t payloadLen, uint8_t *payload);


/*!
 * @brief Class for parsing UBX protocol messages from u-blox GPS/RTK modules
 */
class Adafruit_UBX {
  public:
    // Constructor
    Adafruit_UBX(Stream &stream);
    uint8_t verbose_debug = 0; // 0=off, 1=basic, 2=verbose

    // Basic methods
    bool begin();
    
    bool checkMessages();    // Message parsing
    bool sendMessage(uint8_t msgClass, uint8_t msgId, uint8_t *payload, uint16_t length); // Send a UBX message
    UBXSendStatus sendMessageWithAck(uint8_t msgClass, uint8_t msgId, uint8_t *payload, uint16_t length, uint16_t timeout_ms = 500);

    // Configure port to use UBX protocol only (disable NMEA)
    UBXSendStatus setUBXOnly(UBXPortId portID, bool checkAck = true, uint16_t timeout_ms = 500);

    void setMessageCallback(UBXMessageCallback callback);     // Set callback function
    UBXMessageCallback onUBXMessage;     // Callback for message received

  private:
    Stream *_stream;                 // Stream interface for reading data
    
    // Buffer for reading messages
    static const uint16_t MAX_PAYLOAD_SIZE = 64; // Maximum UBX payload size
    uint8_t _buffer[MAX_PAYLOAD_SIZE + 8];       // Buffer for message (header, payload, checksum)
    
    // Parser state machine
    enum ParserState {
      WAIT_SYNC_1,     // Waiting for first sync char (0xB5)
      WAIT_SYNC_2,     // Waiting for second sync char (0x62)
      GET_CLASS,       // Reading message class
      GET_ID,          // Reading message ID
      GET_LENGTH_1,    // Reading length LSB
      GET_LENGTH_2,    // Reading length MSB
      GET_PAYLOAD,     // Reading payload
      GET_CHECKSUM_A,  // Reading checksum A
      GET_CHECKSUM_B   // Reading checksum B
    };
    
    ParserState _parserState = WAIT_SYNC_1; // Current state of the parser
    uint8_t _msgClass;                      // Message class of current message
    uint8_t _msgId;                         // Message ID of current message
    uint16_t _payloadLength;                // Length of current message payload
    uint16_t _payloadCounter;               // Counter for payload bytes received
    uint8_t _checksumA;                     // Running checksum A
    uint8_t _checksumB;                     // Running checksum B
    
    // Calculate checksum for a block of data
    void calculateChecksum(uint8_t *buffer, uint16_t len, uint8_t &checksumA, uint8_t &checksumB);
    
    // Reset parser state
    void resetParser();

    // Add to private section of Adafruit_UBX.h
    uint8_t _lastMsgClass;        // Class of last message
    uint8_t _lastMsgId;           // ID of last message
    uint16_t _lastPayloadLength;  // Length of last message payload
    uint8_t _lastPayload[8];      // Buffer for small payloads (like ACK messages)
};

#endif // ADAFRUIT_UBX_H