#ifndef MPS_SENSOR_H
#define MPS_SENSOR_H

#pragma once

#include <stdint.h>
#include <stdbool.h>
#include "config.h"

// =====================================================
// MPS SENSOR COMMAND IDs
// =====================================================
#define MPS_CMD_ANSWER          0x01    // Returns a complete answer in one read
#define MPS_CMD_CONC            0x03    // Returns flammable gas concentration [%LEL]
#define MPS_CMD_ID              0x04    // Returns flammable gas ID
#define MPS_CMD_TEMP            0x21    // Returns ambient temperature (C)
#define MPS_CMD_PRES            0x22    // Returns ambient pressure (kPa)
#define MPS_CMD_REL_HUM         0x23    // Returns ambient relative humidity (%RH)
#define MPS_CMD_ABS_HUM         0x24    // Returns ambient absolute humidity (g/m3)
#define MPS_CMD_STATUS          0x41    // Returns MPS status code
#define MPS_CMD_VERSION         0x42    // Returns SW / HW / protocol versions
#define MPS_CMD_SENSOR_INFO     0x43    // Returns sensor serial number and info
#define MPS_CMD_MEAS            0x61    // Sets sensing mode and concentration unit
#define MPS_CMD_RESET           0x62    // Soft reset — clears all data and states

// =====================================================
// MPS MEASUREMENT MODE (payload for MPS_CMD_MEAS)
// =====================================================
// CONFIRMED from NevadaNano MPS 5.0 User Manual, Table 12.
// Only two modes are documented; there is no "idle" or "single" mode.
#define MPS_MEAS_MODE_CONT          0x2     // MPS_CONT — continuous autonomous mode
#define MPS_MEAS_MODE_STOP          0x3     // MPS_STOP — stop measurement

// CONFIRMED from User Manual, Table 11.
#define MPS_CONC_UNIT_LEL_ISO       0x0     // %LEL per ISO 10156
#define MPS_CONC_UNIT_LEL_IEC       0x2     // %LEL per IEC 60079-20-1

// =====================================================
// MPS STATUS CODES
// =====================================================
#define MPS_STATUS_OK                           0x00
#define MPS_STATUS_CRC_FAILED                   0x01
#define MPS_STATUS_BAD_PARAMETER                0x02
#define MPS_STATUS_EXECUTION_FAILED             0x03
#define MPS_STATUS_NO_MEMORY                    0x04
#define MPS_STATUS_UNKNOWN_COMMAND              0x05
#define MPS_STATUS_INCOMPLETE_COMMAND           0x07
#define MPS_STATUS_HW_ERR_AO                    0x20
#define MPS_STATUS_HW_ERR_VDD                   0x21
#define MPS_STATUS_HW_ERR_VREF                  0x22
#define MPS_STATUS_HW_ENV_XCD_RANGE             0x23
#define MPS_STATUS_HW_ENV_SNSR_MALFUNCTION      0x24
#define MPS_STATUS_HW_ERR_MCU                   0x25
#define MPS_STATUS_SENSOR_INITIALIZATION        0x26
#define MPS_STATUS_SENSOR_STARTUP               0x27
#define MPS_STATUS_SENSOR_NEGATIVE              0x30
#define MPS_STATUS_CONDENSATION_DETECTED        0x31
#define MPS_STATUS_HW_SENSOR_MALFUNCTION        0x32
#define MPS_STATUS_GAS_DETECTED_DURING_STARTUP  0x33
#define MPS_STATUS_SLOW_GAS_ACCUMULATION        0x34
#define MPS_STATUS_BREATH_OR_HUMIDITY_SURGE     0x35
#define MPS_STATUS_WATCHDOG_MCU_RESET           0x36
#define MPS_STATUS_HW_ERR_WATCHDOG              0x37
#define MPS_STATUS_HW_ERR_DAC_ADC_XCD_RANGE     0x38

// =====================================================
// ALARM LEVELS
// =====================================================
typedef enum {
    MPS_ALARM_NONE    = 0,
    MPS_ALARM_WARNING = 1,
    MPS_ALARM_ALARM   = 2,
    MPS_ALARM_HIGH    = 3
} MpsAlarmLevel_t;

// =====================================================
// PACKET STRUCTURES
// =====================================================
// CONFIRMED from NevadaNano MPS 5.0 User Manual, Tables 2 & 3.
// All multi-byte integers are Little-Endian on the wire.
//
// Request header (8 bytes): CmdID(2) + Length(2) + Reserved(2) + Checksum(2)
// Reply header   (6 bytes): CmdID(1) + Status(1) + Length(2)   + Checksum(2)
//
// NOTE: CmdID in the REQUEST is 2 bytes (high byte always 0x00) for alignment,
// even though only 1 byte is meaningful. This differs from the REPLY, where
// CmdID is 1 byte. Mixing these up breaks the CRC and the sensor will return
// CRC_FAILED (0x01) or simply not respond as expected.
typedef struct __attribute__((packed)) {
    uint16_t cmdID;        // Command ID, low byte significant, high byte = 0x00
    uint16_t length;       // Payload length in bytes (0 if no payload)
    uint16_t reserved;     // Reserved for future use, zero-filled
    uint16_t checksum;     // CRC-16/CCITT over entire packet (this field zeroed during calc)
    uint8_t  payload[MPS_PACKET_MAX_PAYLOAD];
} MpsRequest_t;

typedef struct __attribute__((packed)) {
    uint8_t  cmdID;        // Echo of command ID (1 byte in replies)
    uint8_t  status;       // MPS_STATUS_* code
    uint16_t length;       // Payload length in bytes (0 if no payload)
    uint16_t checksum;     // CRC-16/CCITT over entire packet (this field zeroed during calc)
    uint8_t  payload[MPS_PACKET_MAX_PAYLOAD];
} MpsReply_t;

// =====================================================
// SENSOR DATA
// =====================================================
typedef struct {
    uint32_t cycle_count;        // Measurement cycle number; compare to detect repeats
    float    concentration_lel;
    uint8_t  gas_id;
    float    temperature_c;
    float    pressure_kpa;
    float    rel_humidity_pct;
    float    abs_humidity_gm3;
    uint8_t  sensor_status;
    MpsAlarmLevel_t alarm_level;
    bool     data_valid;
} MpsSensorData_t;

// =====================================================
// FUNCTION DECLARATIONS
// =====================================================
bool        MPS_Init(void);
bool        MPS_Reset(void);
bool        MPS_SetMeasurementMode(uint8_t mode, uint8_t unit);
bool        MPS_ReadStatus(uint8_t *status);
bool        MPS_ReadAll(MpsSensorData_t *data);
bool        MPS_ReadConcentration(float *conc_lel);
bool        MPS_ReadEnvironmental(MpsSensorData_t *data);
void        MPS_EvaluateAlarm(MpsSensorData_t *data);
const char *MPS_StatusString(uint8_t status);
uint16_t    MPS_ComputeCRC(const uint8_t *data, uint16_t len);

#endif // MPS_SENSOR_H