// Package lis3dh provides a driver for the LIS3DH digital accelerometer.
//
// Datasheet: https://www.st.com/resource/en/datasheet/lis3dh.pdf
package lis3dh // import "tinygo.org/x/drivers/lis3dh"

import (
	"tinygo.org/x/drivers"
	"tinygo.org/x/drivers/internal/legacy"
)

// Device wraps an I2C connection to a LIS3DH device.
type Device struct {
	bus     drivers.I2C
	address uint16
	r       Range
}

// Driver configuration, used for the Configure call. All fields are optional.
type Config struct {
	Address uint16
}

// New creates a new LIS3DH connection. The I2C bus must already be configured.
//
// This function only creates the Device object, it does not touch the device.
func New(bus drivers.I2C) Device {
	return Device{bus: bus, address: Address0}
}

// Configure sets up the device for communication
func (d *Device) Configure(config Config) error {
	if config.Address != 0 {
		d.address = config.Address
	}

	// enable all axes, normal mode
	err := legacy.WriteRegister(d.bus, uint8(d.address), REG_CTRL1, []byte{0x07})
	if err != nil {
		return err
	}

	// 400Hz rate
	err = d.SetDataRate(DATARATE_400_HZ)
	if err != nil {
		return err
	}

	// High res & BDU enabled
	err = legacy.WriteRegister(d.bus, uint8(d.address), REG_CTRL4, []byte{0x88})
	if err != nil {
		return err
	}

	// get current range
	d.r, err = d.ReadRange()
	return err
}

// Connected returns whether a LIS3DH has been found.
// It does a "who am I" request and checks the response.
func (d *Device) Connected() bool {
	data := []byte{0}
	err := legacy.ReadRegister(d.bus, uint8(d.address), WHO_AM_I, data)
	if err != nil {
		return false
	}
	return data[0] == 0x33
}

// SetDataRate sets the speed of data collected by the LIS3DH.
func (d *Device) SetDataRate(rate DataRate) error {
	ctl1 := []byte{0}
	err := legacy.ReadRegister(d.bus, uint8(d.address), REG_CTRL1, ctl1)
	if err != nil {
		return err
	}
	// mask off bits
	ctl1[0] &^= 0xf0
	ctl1[0] |= (byte(rate) << 4)
	return legacy.WriteRegister(d.bus, uint8(d.address), REG_CTRL1, ctl1)
}

// SetRange sets the G range for LIS3DH.
func (d *Device) SetRange(r Range) error {
	ctl := []byte{0}
	err := legacy.ReadRegister(d.bus, uint8(d.address), REG_CTRL4, ctl)
	if err != nil {
		return err
	}
	// mask off bits
	ctl[0] &^= 0x30
	ctl[0] |= (byte(r) << 4)
	err = legacy.WriteRegister(d.bus, uint8(d.address), REG_CTRL4, ctl)
	if err != nil {
		return err
	}

	// store the new range
	d.r = r

	return nil
}

// ReadRange returns the current G range for LIS3DH.
func (d *Device) ReadRange() (r Range, err error) {
	ctl := []byte{0}
	err = legacy.ReadRegister(d.bus, uint8(d.address), REG_CTRL4, ctl)
	if err != nil {
		return 0, err
	}
	// mask off bits
	r = Range(ctl[0] >> 4)
	r &= 0x03

	return r, nil
}

// ReadAcceleration reads the current acceleration from the device and returns
// it in µg (micro-gravity). When one of the axes is pointing straight to Earth
// and the sensor is not moving the returned value will be around 1000000 or
// -1000000.
func (d *Device) ReadAcceleration() (int32, int32, int32, error) {
	x, y, z := d.ReadRawAcceleration()
	divider := float32(1)
	switch d.r {
	case RANGE_16_G:
		divider = 1365
	case RANGE_8_G:
		divider = 4096
	case RANGE_4_G:
		divider = 8190
	case RANGE_2_G:
		divider = 16380
	}

	return int32(float32(x) / divider * 1000000), int32(float32(y) / divider * 1000000), int32(float32(z) / divider * 1000000), nil
}

// ReadRawAcceleration returns the raw x, y and z axis from the LIS3DH
func (d *Device) ReadRawAcceleration() (x int16, y int16, z int16) {
	legacy.WriteRegister(d.bus, uint8(d.address), REG_OUT_X_L|0x80, nil)

	data := []byte{0, 0, 0, 0, 0, 0}
	d.bus.Tx(d.address, nil, data)

	x = int16((uint16(data[1]) << 8) | uint16(data[0]))
	y = int16((uint16(data[3]) << 8) | uint16(data[2]))
	z = int16((uint16(data[5]) << 8) | uint16(data[4]))

	return
}