/**
 * Modbus slave
 */

#ifndef MODBUS_H
#define MODBUS_H

#include <stdint.h>
#include <stdbool.h>
#include <sys/types.h>

// Config - TODO do this via cmake
#define MB_SUPPORT_FC01  // READ_COILS
#define MB_SUPPORT_FC02  // READ_DISCRETES
#define MB_SUPPORT_FC03  // READ_HOLDING_REGISTERS
#define MB_SUPPORT_FC04  // READ_INPUT_REGISTERS
#define MB_SUPPORT_FC05  // WRITE_SINGLE_COIL
#define MB_SUPPORT_FC06  // WRITE_SINGLE_REGISTER
#define MB_SUPPORT_FC15  // WRITE_MULTIPLE_COILS
#define MB_SUPPORT_FC16  // WRITE_MULTIPLE_REGISTERS
#define MB_SUPPORT_FC22  // MASK_WRITE_REGISTER
#define MB_SUPPORT_FC23  // READ_WRITE_MULTIPLE_REGISTERS

typedef enum ModbusException {
  MB_EXCEPTION_OK = 0,
  MB_EXCEPTION_ILLEGAL_FUNCTION = 1,
  MB_EXCEPTION_ILLEGAL_DATA_ADDRESS = 2,
  MB_EXCEPTION_ILLEGAL_DATA_VALUE = 3,
  MB_EXCEPTION_SLAVE_DEVICE_FAILURE = 4,
  // other codes exist but are not meaningful for simple slave devices
} ModbusException_t;

typedef enum ModbusFunction {
  FC01_READ_COILS = 1,
  FC02_READ_DISCRETES = 2,
  FC03_READ_HOLDING_REGISTERS = 3,
  FC04_READ_INPUT_REGISTERS = 4,
  FC05_WRITE_SINGLE_COIL = 5,
  FC06_WRITE_SINGLE_REGISTER = 6,
  FC15_WRITE_MULTIPLE_COILS = 15,
  FC16_WRITE_MULTIPLE_REGISTERS = 16,
  FC22_MASK_WRITE_REGISTER = 22,
  FC23_READ_WRITE_MULTIPLE_REGISTERS = 23,
} ModbusFunction_t;

typedef enum ModbusError {
  MB_OK = 0,
  MB_ERROR = 1,
  MB_ERR_NOTFORME = 2,
  MB_ERR_NEEDMORE = 3,
  MB_ERR_CHECKSUM = 4,
  MB_ERR_BADPROTO = 5,
} ModbusError_t;

typedef enum ModbusProtocol {
  MB_PROTO_RTU,
  MB_PROTO_TCP
} ModbusProtocol_t;

typedef struct ModbusSlave ModbusSlave_t;

struct ModbusSlave {
  uint8_t addr;
  ModbusProtocol_t proto;
  void *userData;
  ModbusException_t (*startOfAccess)(ModbusSlave_t *ms, ModbusFunction_t fcx, uint8_t slave_id);
  void (*endOfAccess)(ModbusSlave_t *ms);

#ifdef MB_SUPPORT_FC01
  ModbusException_t (*readCoil)(ModbusSlave_t *ms, uint16_t reference, bool *value);
#endif

#ifdef MB_SUPPORT_FC02
  ModbusException_t (*readDiscrete)(ModbusSlave_t *ms, uint16_t reference, bool *value);
#endif

#if defined(MB_SUPPORT_FC03) || defined(MB_SUPPORT_FC22) || defined(MB_SUPPORT_FC23)
  ModbusException_t (*readHolding)(ModbusSlave_t *ms, uint16_t reference, uint16_t *value);
#endif

#ifdef MB_SUPPORT_FC04
  ModbusException_t (*readInput)(ModbusSlave_t *ms, uint16_t reference, uint16_t *value);
#endif

#if defined(MB_SUPPORT_FC15) || defined(MB_SUPPORT_FC05)
  ModbusException_t (*writeCoil)(ModbusSlave_t *ms, uint16_t reference, bool value);
#endif

#if defined(MB_SUPPORT_FC06) || defined(MB_SUPPORT_FC16) || defined(MB_SUPPORT_FC22) || defined(MB_SUPPORT_FC23)
  ModbusException_t (*writeHolding)(ModbusSlave_t *ms, uint16_t reference, uint16_t value);
#endif
};

ModbusError_t mb_handleRequest(
        ModbusSlave_t *ms,
        const uint8_t *req,
        size_t req_size,
        uint8_t* resp,
        size_t resp_capacity,
        size_t *resp_size
);

#endif //MODBUS_H