/**
 * @file DCCDecoder.h
 * @brief DCC Signal Decoder for locomotive control
 * 
 * Decodes DCC packets from the track signal, extracts speed and function commands,
 * and manages locomotive addressing (short/long address support).
 */

#ifndef DCC_DECODER_H
#define DCC_DECODER_H

#include <Arduino.h>

// DCC Timing constants (in microseconds)
#define DCC_ONE_BIT_MIN 52
#define DCC_ONE_BIT_MAX 64
#define DCC_ZERO_BIT_MIN 95
#define DCC_ZERO_BIT_MAX 9900

// Maximum packet size
#define MAX_DCC_PACKET_SIZE 6

class DCCDecoder {
public:
    DCCDecoder();
    
    /**
     * @brief Initialize the DCC decoder
     * @param dccPin GPIO pin for DCC signal input
     * @return true if initialization successful
     */
    bool begin(uint8_t dccPin);
    
    /**
     * @brief Process DCC signal (call frequently from loop or ISR)
     */
    void process();
    
    /**
     * @brief Get current speed value (0-126, 0=stop, 1=emergency stop)
     * @return Current speed
     */
    uint8_t getSpeed() const { return currentSpeed; }
    
    /**
     * @brief Get current direction
     * @return true = forward, false = reverse
     */
    bool getDirection() const { return direction; }
    
    /**
     * @brief Get function state (F0-F28)
     * @param functionNum Function number (0-28)
     * @return Function state (true = on)
     */
    bool getFunction(uint8_t functionNum) const;
    
    /**
     * @brief Check if decoder has received valid packets recently
     * @return true if signal is valid
     */
    bool hasValidSignal() const;
    
    /**
     * @brief Set locomotive address
     * @param address Locomotive address (1-10239)
     */
    void setAddress(uint16_t address);
    
    /**
     * @brief Get current locomotive address
     */
    uint16_t getAddress() const { return locoAddress; }

private:
    static void IRAM_ATTR dccISR();
    static DCCDecoder* instance;
    
    void decodeDCCPacket();
    void processSpeedPacket(uint8_t* data, uint8_t len);
    void processFunctionPacket(uint8_t* data, uint8_t len);
    
    uint8_t dccInputPin;
    uint16_t locoAddress;
    uint8_t currentSpeed;
    bool direction;
    uint32_t functions; // Bit field for F0-F28
    
    // Packet assembly
    uint8_t packetBuffer[MAX_DCC_PACKET_SIZE];
    uint8_t packetIndex;
    uint8_t bitCount;
    bool assemblingPacket;
    
    // Timing
    unsigned long lastBitTime;
    unsigned long lastValidPacket;
};

#endif // DCC_DECODER_H