// Package rfm69 RFM69 Implementation in Go
package rfm69

import (
	"errors"
	"log"
	"time"
	"github.com/davecheney/gpio"
	"github.com/fulr/spidev"
)

const (
	spiPath = "/dev/spidev0.0"
)

var frequencies = map[string][]byte{
	"433": {0x6C, 0x40, 0x00},
	"868": {0xD9, 0x00, 0x00},
	"915": {0xE4, 0xC0, 0x00},
}

// OnReceiveHandler is the receive callback
type OnReceiveHandler func(*RXStream)

// Device RFM69 Device
type Device struct {
	spiDevice  *spidev.SPIDevice
	gpio       gpio.Pin
	mode       byte
	isRFM69HW  bool
	powerLevel byte
	tx         chan *Data
	quit       chan bool
	_invert    bool
	OnReceive  OnReceiveHandler
}

// Global settings
const (
	CsmaLimit  = -80
	MaxDataLen = 66
)

// NewDevice creates a new device
func NewDevice(isRfm69HW bool) (*Device, error) {
	pin, err := getPin()
	if err != nil {
		return nil, err
	}

	spi, err := spidev.NewSPIDevice(spiPath)
	if err != nil {
		return nil, err
	}

	ret := &Device{
		spiDevice:  spi,
		gpio:       pin,
		isRFM69HW:  isRfm69HW,
		powerLevel: 31,
		_invert: false,
		tx:         make(chan *Data, 5),
		quit:       make(chan bool),
	}

	err = ret.setup()
	if err != nil {
		return nil, err
	}

	//go ret.loop()

	return ret, nil
}

// Close cleans up
func (r *Device) Close() error {
	r.quit <- true
	<-r.quit
	err := r.gpio.Close()
	if err != nil {
		return err
	}
	r.spiDevice.Close()
	return err
}

func (r *Device) writeReg(addr, data byte) error {
	tx := make([]byte, 2)
	tx[0] = addr | 0x80
	tx[1] = data
	//log.Printf("write %x: %x", addr, data)
	_, err := r.spiDevice.Xfer(tx)
	if err != nil {
		log.Println(err)
	}
	return err
}
func (r *Device) writeRegDouble(addr byte, data uint16) error {
	tx := make([]byte, 3)
	tx[0] = addr | 0x80
	tx[1] = byte((data >>  8) & 0xFF)
	tx[2] = byte(data & 0xFF)
	//log.Printf("write %x: %x", addr, data)
	_, err := r.spiDevice.Xfer(tx)
	if err != nil {
		log.Println(err)
	}
	return err
}
func (r *Device) WriteReg(addr, data byte) error {
	return r.writeReg(addr, data)
}

func (r *Device) readReg(addr byte) (byte, error) {
	tx := make([]uint8, 2)
	tx[0] = addr & 0x7f
	tx[1] = 0
	rx, err := r.spiDevice.Xfer(tx)
	if err != nil {
		log.Println(err)
	}
	return rx[1], err
}

func (r *Device) setup() error {
	config := [][]byte{
		/* 0x01 */ {REG_OPMODE, RF_OPMODE_SEQUENCER_ON | RF_OPMODE_LISTEN_OFF | RF_OPMODE_STANDBY},
		/* 0x02 */ {REG_DATAMODUL, RF_DATAMODUL_DATAMODE_PACKET | RF_DATAMODUL_MODULATIONTYPE_FSK | RF_DATAMODUL_MODULATIONSHAPING_00}, // no shaping
		/* 0x03 */ {REG_BITRATEMSB, 0x68},
		/* 0x04 */ {REG_BITRATELSB, 0x2B},
		/* 0x05 */ {REG_FDEVMSB, 0x00}, // default: 5KHz, (FDEV + BitRate / 2 <= 500KHz)
		/* 0x06 */ {REG_FDEVLSB, 0x4a},
		/* 0x07 */ {REG_FRFMSB, RF_FRFMSB_868},
		/* 0x08 */ {REG_FRFMID, RF_FRFMID_868},
		/* 0x09 */ {REG_FRFLSB, RF_FRFLSB_868},
		// looks like PA1 and PA2 are not implemented on RFM69W, hence the max output power is 13dBm
		// +17dBm and +20dBm are possible on RFM69HW
		// +13dBm formula: Pout = -18 + OutputPower (with PA0 or PA1**)
		// +17dBm formula: Pout = -14 + OutputPower (with PA1 and PA2)**
		// +20dBm formula: Pout = -11 + OutputPower (with PA1 and PA2)** and high power PA settings (section 3.3.7 in datasheet)
		///* 0x11 */ { REG_PALEVEL, RF_PALEVEL_PA0_ON | RF_PALEVEL_PA1_OFF | RF_PALEVEL_PA2_OFF | RF_PALEVEL_OUTPUTPOWER_11111},
		///* 0x13 */ { REG_OCP, RF_OCP_ON | RF_OCP_TRIM_95 }, // over current protection (default is 95mA)
		// RXBW defaults are { REG_RXBW, RF_RXBW_DCCFREQ_010 | RF_RXBW_MANT_24 | RF_RXBW_EXP_5} (RxBw: 10.4KHz)
		/* 0x19 */ {REG_RXBW, RF_RXBW_DCCFREQ_010 | RF_RXBW_MANT_16 | RF_RXBW_EXP_2}, // (BitRate < 2 * RxBw)
		//for BR-19200: /* 0x19 */ { REG_RXBW, RF_RXBW_DCCFREQ_010 | RF_RXBW_MANT_24 | RF_RXBW_EXP_3 },
		/* 0x25 */ {REG_DIOMAPPING1, RF_DIOMAPPING1_DIO0_01}, // DIO0 is the only IRQ we're using
		/* 0x26 */ {REG_DIOMAPPING2, RF_DIOMAPPING2_CLKOUT_OFF }, // DIO5 ClkOut disable for power saving
		/* 0x28 */ {REG_IRQFLAGS2, RF_IRQFLAGS2_FIFOOVERRUN}, // writing to this bit ensures that the FIFO & status flags are reset
		/* 0x29 */ {REG_RSSITHRESH, 220}, // must be set to dBm = (-Sensitivity / 2), default is 0xE4 = 228 so -114dBm
		///* 0x2D */ { REG_PREAMBLELSB, RF_PREAMBLESIZE_LSB_VALUE } // default 3 preamble bytes 0xAAAAAA
		/* 0x2E */ {REG_SYNCCONFIG, RF_SYNC_ON | RF_SYNC_FIFOFILL_AUTO | RF_SYNC_SIZE_6 | RF_SYNC_TOL_0},
		/* 0x2F */ {REG_SYNCVALUE1, 0xAA},
		/* 0x30 */ {REG_SYNCVALUE2, 0xAA},
		/* 0x30 */ {REG_SYNCVALUE3, 0xAA},
		/* 0x30 */ {REG_SYNCVALUE4, 0xAA},
		/* 0x30 */ {REG_SYNCVALUE5, 0xAA},
		/* 0x30 */ {REG_SYNCVALUE6, 0xAA},
		/* 0x37 */ {REG_PACKETCONFIG1, RF_PACKET1_FORMAT_FIXED | RF_PACKET1_DCFREE_OFF | RF_PACKET1_CRC_OFF | RF_PACKET1_CRCAUTOCLEAR_ON | RF_PACKET1_ADRSFILTERING_OFF},
		/* 0x38 */ {REG_PAYLOADLENGTH, 0x00}, // in variable length mode: the max frame size, not used in TX, 0: unlimited packet format
		///* 0x39 */ { REG_NODEADRS, nodeID }, // turned off because we're not using address filtering
		/* 0x3C */ {REG_FIFOTHRESH, RF_FIFOTHRESH_TXSTART_FIFONOTEMPTY | RF_FIFOTHRESH_VALUE}, // TX on FIFO not empty
		/* 0x3D */ {REG_PACKETCONFIG2, RF_PACKET2_RXRESTARTDELAY_2BITS | RF_PACKET2_AUTORXRESTART_ON | RF_PACKET2_AES_OFF}, // RXRESTARTDELAY must match transmitter PA ramp-down time (bitrate dependent)
		/* 0x2D */ {REG_PREAMBLELSB, 0x00},
		//for BR-19200: /* 0x3D */ { REG_PACKETCONFIG2, RF_PACKET2_RXRESTARTDELAY_NONE | RF_PACKET2_AUTORXRESTART_ON | RF_PACKET2_AES_OFF }, // RXRESTARTDELAY must match transmitter PA ramp-down time (bitrate dependent)
		/* 0x6F */ {REG_TESTDAGC, RF_DAGC_IMPROVED_LOWBETA0}, // run DAGC continuously in RX mode for Fading Margin Improvement, recommended default for AfcLowBetaOn=0
	}
	for data, err := r.readReg(REG_SYNCVALUE1); err == nil && data != 0xAA; data, err = r.readReg(REG_SYNCVALUE1) {
		err := r.writeReg(REG_SYNCVALUE1, 0xAA)
		if err != nil {
			return err
		}
	}
	for data, err := r.readReg(REG_SYNCVALUE1); err == nil && data != 0x55; data, err = r.readReg(REG_SYNCVALUE1) {
		r.writeReg(REG_SYNCVALUE1, 0x55)
		if err != nil {
			return err
		}
	}
	for _, c := range config {
		err := r.writeReg(c[0], c[1])
		if err != nil {
			return err
		}
	}
	err := r.Encrypt([]byte{})
	if err != nil {
		return err
	}
	err = r.SetInvert(false)
	if err != nil {
		return err
	}
	err = r.setHighPower(r.isRFM69HW)
	if err != nil {
		return err
	}
	err = r.SetMode(RF_OPMODE_STANDBY)
	if err != nil {
		return err
	}
	err = r.waitForMode()
	return err
}
func (r *Device) SetInvert(invert bool) error {
	r._invert = invert
	if (r._invert) {
		r.WriteReg(REG_SYNCVALUE1, 0x55)
		r.WriteReg(REG_SYNCVALUE2, 0x55)
		r.WriteReg(REG_SYNCVALUE3, 0x55)
	} else  {
		r.WriteReg(REG_SYNCVALUE1, 0xAA)
		r.WriteReg(REG_SYNCVALUE2, 0xAA)
		r.WriteReg(REG_SYNCVALUE3, 0xAA)
	}
	return nil
}
func (r *Device) waitForMode() error {
	errChan := make(chan error)
	go func() {
		for {
			reg, err := r.readReg(REG_IRQFLAGS1)
			if err != nil {
				errChan <- err
				break
			}
			if reg&RF_IRQFLAGS1_MODEREADY != 0 {
				errChan <- nil
				break
			}
		}
	}()
	time.AfterFunc(5*time.Second, func() {
		errChan <- errors.New("timeout")
	})
	return <-errChan
}
func (r *Device) WaitForMode() error {
	return r.waitForMode();
}

// Encrypt sets the encryption key and enables AES encryption
func (r *Device) Encrypt(key []byte) error {
	var turnOn byte
	if len(key) == 16 {
		turnOn = 1
		tx := make([]byte, 17)
		tx[0] = REG_AESKEY1 | 0x80
		copy(tx[1:], key)
		if _, err := r.spiDevice.Xfer(tx); err != nil {
			return err
		}
	}
	return r.readWriteReg(REG_PACKETCONFIG2, 0xFE, turnOn)
}

func (r *Device) SetBaudrate(rate int) error {
	var divider uint16 =  (uint16)(32e6 / rate) //0x4F4F
	
	/*switch(rate) {
		case 1200:
			divider = 0x682B
		case 2400:
			divider = 0x3415
	}*/
	return r.writeRegDouble(REG_BITRATEMSB, divider)
}
func (r *Device) SetFrequency(freqHz, offset int) error {
    //freqHz =   // divide down by FSTEP to get FRF
	frf := (int)((float32(freqHz) / float32(61.03515625))) + offset  // offset per chip (you may have to calibrate)
	if err := r.writeReg(REG_FRFMSB, byte((frf >> 16) & 0xFF)); err != nil {
		return err
	}
	if err := r.writeReg(REG_FRFMID, byte((frf >>  8) & 0xFF)); err != nil {
		return err
	}
	if err := r.writeReg(REG_FRFLSB, byte(frf & 0xFF)); err != nil {
		return err
	}
	return nil
}

// SetMode sets operation mode
func (r *Device) SetMode(newMode byte) error {
	if newMode == r.mode {
		return nil
	}
	err := r.readWriteReg(REG_OPMODE, 0xE3, newMode)
	if err != nil {
		return err
	}
	if r.isRFM69HW && (newMode == RF_OPMODE_RECEIVER || newMode == RF_OPMODE_TRANSMITTER) {
		err := r.setHighPowerRegs(newMode == RF_OPMODE_TRANSMITTER)
		if err != nil {
			return err
		}
	}
	if r.mode == RF_OPMODE_SLEEP {
		err = r.waitForMode()
		if err != nil {
			return err
		}
	}
	r.mode = newMode
	return nil
}

// SetModeAndWait sets the mode and waits for it
func (r *Device) SetModeAndWait(newMode byte) error {
	err := r.SetMode(RF_OPMODE_STANDBY)
	if err != nil {
		return err
	}
	err = r.waitForMode()
	if err != nil {
		return err
	}
	return nil
}

func (r *Device) setHighPower(turnOn bool) error {
	r.isRFM69HW = turnOn
	ocp := byte(RF_OCP_ON)
	if r.isRFM69HW {
		ocp = RF_OCP_OFF
	}
	err := r.writeReg(REG_OCP, ocp)
	if err != nil {
		return err
	}
	if r.isRFM69HW {
		err = r.readWriteReg(REG_PALEVEL, 0x1F, RF_PALEVEL_PA1_ON|RF_PALEVEL_PA2_ON)
	} else {
		err = r.readWriteReg(REG_PALEVEL, 0, RF_PALEVEL_PA0_ON|RF_PALEVEL_PA1_OFF|RF_PALEVEL_PA2_OFF|r.powerLevel)
	}
	return err
}

func (r *Device) setHighPowerRegs(turnOn bool) (err error) {
	var (
		testPa1 byte = 0x55
		testPa2 byte = 0x70
	)

	if turnOn {
		testPa1 = 0x5D
		testPa2 = 0x7C
	}
	err = r.writeReg(REG_TESTPA1, testPa1)
	if err != nil {
		return
	}
	err = r.writeReg(REG_TESTPA2, testPa2)
	return
}

// SetPowerLevel sets the TX power
func (r *Device) SetPowerLevel(powerLevel byte) error {
	r.powerLevel = powerLevel
	if r.powerLevel > 31 {
		r.powerLevel = 31
	}
	return r.readWriteReg(REG_PALEVEL, 0xE0, r.powerLevel)
}

func (r *Device) canSend() (bool, error) {
	// if signal stronger than -100dBm is detected assume channel activity
	if r.mode == RF_OPMODE_RECEIVER {
		rssi, err := r.readRSSI(false)
		if err != nil {
			return false, err
		}
		if rssi < CsmaLimit {
			err = r.SetMode(RF_OPMODE_STANDBY)
			return true, err
		}
	}
	return false, nil
}

func (r *Device) readRSSI(forceTrigger bool) (rssi int, err error) {
	if forceTrigger {
		// RSSI trigger not needed if DAGC is in continuous mode
		err = r.writeReg(REG_RSSICONFIG, RF_RSSI_START)
		if err != nil {
			return
		}
		for {
			data, err := r.readReg(REG_RSSICONFIG)
			if err != nil {
				return 0, err
			}
			if data&RF_RSSI_DONE != 0 {
				break
			}
		}
	}
	data, err := r.readReg(REG_RSSIVALUE)
	if err != nil {
		return
	}
	rssi = -int(data) / 2
	return
}

func (r *Device) readWriteReg(reg, andMask, orMask byte) error {
	regValue, err := r.readReg(reg)
	if err != nil {
		return err
	}
	regValue = (regValue & andMask) | orMask
	return r.writeReg(reg, regValue)
}

func (r *Device) writeFifo(data []byte) error {
	buffersize := len(data)
	if buffersize > MaxDataLen {
		buffersize = MaxDataLen
	}
	tx := make([]byte, buffersize+1)
	// write to FIFO
	tx[0] = REG_FIFO | 0x80
	copy(tx[1:], data[:buffersize])
	//log.Println("% X\n\n", tx)
	_, err := r.spiDevice.Xfer(tx)
	return err
}

func (r *Device) WriteFifoData(data []byte) error {
	if err := r.writeFifo(data); err != nil {
		return err
	}
	return nil
}
func (r *Device) WriteFifoDataWait() error {
	errChan := make(chan error)
	go func() {
		for {
			reg, err := r.readReg(REG_IRQFLAGS2)
			if err != nil {
				log.Fatal(err)
				panic(err)
				errChan <- err
				break
			}
			log.Println("% X", reg)
			if reg&RF_IRQFLAGS2_FIFONOTEMPTY != 0 {
				errChan <- nil
				break
			}
		}
	}()
	time.AfterFunc(2*time.Second, func() {
		errChan <- errors.New("timeout fifowait")
	})
	return <-errChan
}

func (r *Device) readFifo() (Data, error) {
	var err error
	data := Data{}
	/*data.Rssi, err = r.readRSSI(false)
	if err != nil {
		return data, err
	}*/
	tx := new([67]byte)
	tx[0] = REG_FIFO & 0x7f
	rx, err := r.spiDevice.Xfer(tx[:1])
	if err != nil {
		return data, err
	}  
	rx, err = r.spiDevice.Xfer(tx[1:])
	if err != nil {
		return data, err
	}
	data.Data = rx[1:]
	return data, nil
}
func (r *Device) readFifo1Byte() (byte, error) {
	var err error
	log.Println("readFifo1Byte()")
	tx := new([2]byte)
	tx[0] = REG_FIFO & 0x7f
	log.Println(tx)
	rx, err := r.spiDevice.Xfer(tx[:1])
	if err != nil {
		return rx[1], err
	} 
	log.Println(rx)
	rx, err = r.spiDevice.Xfer(tx[1:])
	if err != nil {
		return rx[1], err
	}
	log.Println(rx)
	return rx[0], nil
}