#ifndef _GXHT30_CH32_HW_I2C_H
#define _GXHT30_CH32_HW_I2C_H

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

#include "ch32fun.h"
#include "ch32v20xhw.h"

// I2C Configuration
#define GXHT30_I2C_CLKRATE 400000
#define GXHT30_I2C_PRERATE 2000000
#define GXHT30_I2C_TIMEOUT_MAX 250000

// GXHT30 I2C Addresses
#define GXHT30_I2C_ADDR_DEFAULT 0x44
#define GXHT30_I2C_ADDR_ALT 0x45

// Commands
#define GXHT30_CMD_MEAS_MSB 0x2C
#define GXHT30_CMD_MEAS_LSB 0x06
#define GXHT30_CMD_SOFT_RESET_MSB 0x30
#define GXHT30_CMD_SOFT_RESET_LSB 0xA2
#define GXHT30_CMD_HEATER_ON_MSB 0x30
#define GXHT30_CMD_HEATER_ON_LSB 0x6D
#define GXHT30_CMD_HEATER_OFF_MSB 0x30
#define GXHT30_CMD_HEATER_OFF_LSB 0x66
#define GXHT30_CMD_STATUS_MSB 0xF3
#define GXHT30_CMD_STATUS_LSB 0x2D
#define GXHT30_CMD_CLEAR_STATUS_MSB 0x30
#define GXHT30_CMD_CLEAR_STATUS_LSB 0x41

// I2C Event Masks
#define GXHT30_I2C_EVT_MASTER_MODE_SELECT \
  ((uint32_t)0x00030001)  // BUSY, MSL, SB
#define GXHT30_I2C_EVT_MASTER_TRANSMITTER_MODE \
  ((uint32_t)0x00070082)  // BUSY, MSL, ADDR, TXE, TRA
#define GXHT30_I2C_EVT_MASTER_RECEIVER_MODE \
  ((uint32_t)0x00030002)  // BUSY, MSL, ADDR
#define GXHT30_I2C_EVT_MASTER_BYTE_TRANSMITTED \
  ((uint32_t)0x00070084)  // TRA, BUSY, MSL, TXE, BTF
#define GXHT30_I2C_EVT_MASTER_BYTE_RECEIVED \
  ((uint32_t)0x00030040)  // BUSY, MSL, RXNE

// Sensor Data Structure
typedef struct {
  float temperature;  // Temperature in Celsius
  float humidity;     // Relative humidity in %
  uint8_t error;      // Last error code
} GXHT30_Data;

// Status Register Structure
typedef struct {
  uint8_t alert_pending;      // Bit 15: Alert status
  uint8_t heater_on;          // Bit 13: Heater status
  uint8_t humidity_alert;     // Bit 11: Humidity tracking alert
  uint8_t temperature_alert;  // Bit 10: Temperature tracking alert
  uint8_t reset_detected;     // Bit 4: System reset detected
  uint8_t command_status;     // Bit 1: Last command execution status
  uint8_t crc_status;         // Bit 0: Write data CRC checksum status
  uint16_t raw_status;        // Raw 16-bit status value
} GXHT30_Status;

// Error Codes
enum GXHT30_Error {
  GXHT30_OK = 0,
  GXHT30_ERR_TIMEOUT,
  GXHT30_ERR_CRC,
  GXHT30_ERR_I2C,
  GXHT30_ERR_BUSY
};

static inline uint8_t _gxht30_i2c_check_event(uint32_t event_mask) {
  uint32_t status = I2C1->STAR1 | (I2C1->STAR2 << 16);
  return (status & event_mask) == event_mask;
}

static inline uint8_t _gxht30_wait_event(uint32_t event_mask) {
  int32_t timeout = GXHT30_I2C_TIMEOUT_MAX;
  while (!_gxht30_i2c_check_event(event_mask) && (timeout-- > 0));
  return timeout > 0 ? GXHT30_OK : GXHT30_ERR_TIMEOUT;
}

static inline uint8_t _gxht30_wait_flag(uint32_t flag) {
  int32_t timeout = GXHT30_I2C_TIMEOUT_MAX;
  while (!(I2C1->STAR1 & flag) && (timeout-- > 0));
  return timeout > 0 ? GXHT30_OK : GXHT30_ERR_TIMEOUT;
}

static inline uint8_t _gxht30_i2c_start(uint8_t addr, uint8_t direction) {
  // wait until bus is not busy
  int32_t timeout = GXHT30_I2C_TIMEOUT_MAX;
  while ((I2C1->STAR2 & I2C_STAR2_BUSY) && (timeout-- > 0));
  if (timeout <= 0) return GXHT30_ERR_TIMEOUT;

  // gen START
  I2C1->CTLR1 |= I2C_CTLR1_START;
  if (_gxht30_wait_event(GXHT30_I2C_EVT_MASTER_MODE_SELECT) != GXHT30_OK)
    return GXHT30_ERR_TIMEOUT;

  // send addr
  I2C1->DATAR = (addr << 1) | direction;

  uint32_t event = (direction == 0) ? GXHT30_I2C_EVT_MASTER_TRANSMITTER_MODE
                                    : GXHT30_I2C_EVT_MASTER_RECEIVER_MODE;

  return _gxht30_wait_event(event);
}

static inline uint8_t _gxht30_i2c_write_byte(uint8_t data) {
  I2C1->DATAR = data;
  return _gxht30_wait_flag(I2C_STAR1_TXE);
}

static inline uint8_t _gxht30_i2c_read(uint8_t* buffer, uint8_t length) {
  for (uint8_t i = 0; i < length; i++) {
    if (i == length - 1) {
      I2C1->CTLR1 &= ~I2C_CTLR1_ACK;  // NACK last byte
    }

    if (_gxht30_wait_flag(I2C_STAR1_RXNE) != GXHT30_OK) {
      I2C1->CTLR1 |= I2C_CTLR1_ACK;
      return GXHT30_ERR_TIMEOUT;
    }

    buffer[i] = I2C1->DATAR;
  }

  I2C1->CTLR1 |= I2C_CTLR1_ACK;  // re-enable ACK
  return GXHT30_OK;
}

static inline bool _gxht30_crc8_check(uint8_t msb, uint8_t lsb, uint8_t crc) {
  uint8_t calc_crc = 0xFF;
  uint8_t data[2] = {msb, lsb};

  for (uint8_t byte = 0; byte < 2; byte++) {
    calc_crc ^= data[byte];
    for (uint8_t i = 0; i < 8; i++) {
      calc_crc = (calc_crc & 0x80) ? (calc_crc << 1) ^ 0x31 : (calc_crc << 1);
    }
  }

  return calc_crc == crc;
}

// init I2C hw
static inline void gxht30_i2c_init(void) {
  uint16_t tempreg;

  RCC->APB2PCENR |= RCC_APB2Periph_GPIOB | RCC_APB2Periph_AFIO;
  RCC->APB1PCENR |= RCC_APB1Periph_I2C1;

  // PB6 (SCL) and PB7 (SDA)
  GPIOB->CFGLR &= ~(0xff << (4 * 6));
  GPIOB->CFGLR |= ((GPIO_Speed_10MHz | GPIO_CNF_OUT_OD_AF) << (4 * 6)) |
                  ((GPIO_Speed_10MHz | GPIO_CNF_OUT_OD_AF) << (4 * 7));

  // rst I2C1
  RCC->APB1PRSTR |= RCC_APB1Periph_I2C1;
  RCC->APB1PRSTR &= ~RCC_APB1Periph_I2C1;

  // i2c frequency
  tempreg = I2C1->CTLR2;
  tempreg &= ~I2C_CTLR2_FREQ;
  tempreg |= (FUNCONF_SYSTEM_CORE_CLOCK / GXHT30_I2C_PRERATE) & I2C_CTLR2_FREQ;
  I2C1->CTLR2 = tempreg;

  // Fast Mode 400kHz
  tempreg =
      (FUNCONF_SYSTEM_CORE_CLOCK / (3 * GXHT30_I2C_CLKRATE)) & I2C_CKCFGR_CCR;
  tempreg |= I2C_CKCFGR_FS;
  I2C1->CKCFGR = tempreg;

  // en I2C and ACK
  I2C1->CTLR1 |= I2C_CTLR1_PE | I2C_CTLR1_ACK;
}

static inline uint8_t gxht30_send_command(uint8_t addr, uint8_t cmd_msb,
                                          uint8_t cmd_lsb) {
  uint8_t err;

  if ((err = _gxht30_i2c_start(addr, 0)) != GXHT30_OK) return err;
  if ((err = _gxht30_i2c_write_byte(cmd_msb)) != GXHT30_OK) return err;
  if ((err = _gxht30_i2c_write_byte(cmd_lsb)) != GXHT30_OK) return err;
  if (_gxht30_wait_event(GXHT30_I2C_EVT_MASTER_BYTE_TRANSMITTED) != GXHT30_OK)
    return GXHT30_ERR_TIMEOUT;

  I2C1->CTLR1 |= I2C_CTLR1_STOP;
  return GXHT30_OK;
}

// read temp and humidity
static inline uint8_t gxht30_read_data(uint8_t addr, GXHT30_Data* data) {
  uint8_t rx_data[6];
  uint8_t err;

  if ((err = gxht30_send_command(addr, GXHT30_CMD_MEAS_MSB,
                                 GXHT30_CMD_MEAS_LSB)) != GXHT30_OK) {
    data->error = err;
    return err;
  }

  // read data
  if ((err = _gxht30_i2c_start(addr, 1)) != GXHT30_OK) {
    data->error = err;
    return err;
  }

  if ((err = _gxht30_i2c_read(rx_data, 6)) != GXHT30_OK) {
    data->error = err;
    return err;
  }

  I2C1->CTLR1 |= I2C_CTLR1_STOP;

  // verify crc
  if (!_gxht30_crc8_check(rx_data[0], rx_data[1], rx_data[2]) ||
      !_gxht30_crc8_check(rx_data[3], rx_data[4], rx_data[5])) {
    data->error = GXHT30_ERR_CRC;
    return GXHT30_ERR_CRC;
  }

  // calc values
  uint16_t temp_raw = (rx_data[0] << 8) | rx_data[1];
  uint16_t hum_raw = (rx_data[3] << 8) | rx_data[4];

  data->temperature = (float)temp_raw * 0.00267033f - 45.0f;
  data->humidity = (float)hum_raw * 0.0015259f;
  data->error = GXHT30_OK;

  return GXHT30_OK;
}

static inline uint8_t gxht30_read_status(uint8_t addr, GXHT30_Status* status) {
  uint8_t rx_data[3];
  uint8_t err;

  if ((err = _gxht30_i2c_start(addr, 0)) != GXHT30_OK) return err;
  if ((err = _gxht30_i2c_write_byte(GXHT30_CMD_STATUS_MSB)) != GXHT30_OK)
    return err;
  if ((err = _gxht30_i2c_write_byte(GXHT30_CMD_STATUS_LSB)) != GXHT30_OK)
    return err;
  if (_gxht30_wait_event(GXHT30_I2C_EVT_MASTER_BYTE_TRANSMITTED) != GXHT30_OK)
    return GXHT30_ERR_TIMEOUT;

  I2C1->CTLR1 |= I2C_CTLR1_START;
  if (_gxht30_wait_event(GXHT30_I2C_EVT_MASTER_MODE_SELECT) != GXHT30_OK)
    return GXHT30_ERR_TIMEOUT;

  I2C1->DATAR = (addr << 1) | 0x01;
  if (_gxht30_wait_event(GXHT30_I2C_EVT_MASTER_RECEIVER_MODE) != GXHT30_OK)
    return GXHT30_ERR_TIMEOUT;

  if ((err = _gxht30_i2c_read(rx_data, 3)) != GXHT30_OK) return err;

  I2C1->CTLR1 |= I2C_CTLR1_STOP;

  if (!_gxht30_crc8_check(rx_data[0], rx_data[1], rx_data[2]))
    return GXHT30_ERR_CRC;

  uint16_t raw = (rx_data[0] << 8) | rx_data[1];
  status->raw_status = raw;
  status->alert_pending = (raw >> 15) & 0x01;
  status->heater_on = (raw >> 13) & 0x01;
  status->humidity_alert = (raw >> 11) & 0x01;
  status->temperature_alert = (raw >> 10) & 0x01;
  status->reset_detected = (raw >> 4) & 0x01;
  status->command_status = (raw >> 1) & 0x01;
  status->crc_status = raw & 0x01;

  return GXHT30_OK;
}

static inline uint8_t gxht30_soft_reset(uint8_t addr) {
  return gxht30_send_command(addr, GXHT30_CMD_SOFT_RESET_MSB,
                             GXHT30_CMD_SOFT_RESET_LSB);
}

static inline uint8_t gxht30_heater_on(uint8_t addr) {
  return gxht30_send_command(addr, GXHT30_CMD_HEATER_ON_MSB,
                             GXHT30_CMD_HEATER_ON_LSB);
}

static inline uint8_t gxht30_heater_off(uint8_t addr) {
  return gxht30_send_command(addr, GXHT30_CMD_HEATER_OFF_MSB,
                             GXHT30_CMD_HEATER_OFF_LSB);
}

static inline uint8_t gxht30_clear_status(uint8_t addr) {
  return gxht30_send_command(addr, GXHT30_CMD_CLEAR_STATUS_MSB,
                             GXHT30_CMD_CLEAR_STATUS_LSB);
}

#endif  // _GXHT30_CH32_HW_I2C_H