package beaglebone

import (
	"bufio"
	"errors"
	"fmt"
	"os"
	"strconv"
	"strings"

	multierror "github.com/hashicorp/go-multierror"
	"gobot.io/x/gobot"
	"gobot.io/x/gobot/drivers/i2c"
	"gobot.io/x/gobot/sysfs"
)

const pwmDefaultPeriod = 500000

// Adaptor is the gobot.Adaptor representation for the Beaglebone
type Adaptor struct {
	name        string
	digitalPins []*sysfs.DigitalPin
	pwmPins     map[string]*sysfs.PWMPin
	i2cBuses    map[int]sysfs.I2cDevice
	usrLed      string
	analogPath  string
	slots       string
}

// NewAdaptor returns a new Beaglebone Adaptor
func NewAdaptor() *Adaptor {
	b := &Adaptor{
		name:        gobot.DefaultName("Beaglebone"),
		digitalPins: make([]*sysfs.DigitalPin, 120),
		pwmPins:     make(map[string]*sysfs.PWMPin),
		i2cBuses:    make(map[int]sysfs.I2cDevice),
	}

	b.setSlots()
	return b
}

func (b *Adaptor) setSlots() {
	b.slots = "/sys/devices/platform/bone_capemgr/slots"
	b.usrLed = "/sys/class/leds/beaglebone:green:"
	b.analogPath = "/sys/bus/iio/devices/iio:device0"
}

// Name returns the Adaptor name
func (b *Adaptor) Name() string { return b.name }

// SetName sets the Adaptor name
func (b *Adaptor) SetName(n string) { b.name = n }

// Connect initializes the pwm and analog dts.
func (b *Adaptor) Connect() error {
	if err := ensureSlot(b.slots, "BB-ADC"); err != nil {
		return err
	}

	return nil
}

// Finalize releases all i2c devices and exported analog, digital, pwm pins.
func (b *Adaptor) Finalize() (err error) {
	for _, pin := range b.digitalPins {
		if pin != nil {
			if e := pin.Unexport(); e != nil {
				err = multierror.Append(err, e)
			}
		}
	}
	for _, pin := range b.pwmPins {
		if pin != nil {
			if e := pin.Unexport(); e != nil {
				err = multierror.Append(err, e)
			}
		}
	}
	for _, bus := range b.i2cBuses {
		if bus != nil {
			if e := bus.Close(); e != nil {
				err = multierror.Append(err, e)
			}
		}
	}
	return
}

// PwmWrite writes the 0-254 value to the specified pin
func (b *Adaptor) PwmWrite(pin string, val byte) (err error) {
	pwmPin, err := b.PWMPin(pin)
	if err != nil {
		return
	}
	period, err := pwmPin.Period()
	if err != nil {
		return err
	}
	duty := gobot.FromScale(float64(val), 0, 255.0)
	return pwmPin.SetDutyCycle(uint32(float64(period) * duty))
}

// ServoWrite writes a servo signal to the specified pin
func (b *Adaptor) ServoWrite(pin string, angle byte) (err error) {
	pwmPin, err := b.PWMPin(pin)
	if err != nil {
		return
	}

	// TODO: take into account the actual period setting, not just assume default
	const minDuty = 100 * 0.0005 * pwmDefaultPeriod
	const maxDuty = 100 * 0.0020 * pwmDefaultPeriod
	duty := uint32(gobot.ToScale(gobot.FromScale(float64(angle), 0, 180), minDuty, maxDuty))
	return pwmPin.SetDutyCycle(duty)
}

// DigitalRead returns a digital value from specified pin
func (b *Adaptor) DigitalRead(pin string) (val int, err error) {
	sysfsPin, err := b.DigitalPin(pin, sysfs.IN)
	if err != nil {
		return
	}
	return sysfsPin.Read()
}

// DigitalWrite writes a digital value to specified pin.
// valid usr pin values are usr0, usr1, usr2 and usr3
func (b *Adaptor) DigitalWrite(pin string, val byte) (err error) {
	if strings.Contains(pin, "usr") {
		fi, e := sysfs.OpenFile(b.usrLed+pin+"/brightness", os.O_WRONLY|os.O_APPEND, 0666)
		defer fi.Close()
		if e != nil {
			return e
		}
		_, err = fi.WriteString(strconv.Itoa(int(val)))
		return err
	}
	sysfsPin, err := b.DigitalPin(pin, sysfs.OUT)
	if err != nil {
		return err
	}
	return sysfsPin.Write(int(val))
}

// DigitalPin retrieves digital pin value by name
func (b *Adaptor) DigitalPin(pin string, dir string) (sysfsPin sysfs.DigitalPinner, err error) {
	i, err := b.translatePin(pin)
	if err != nil {
		return
	}
	if b.digitalPins[i] == nil {
		b.digitalPins[i] = sysfs.NewDigitalPin(i)
		err := b.digitalPins[i].Export()
		if err != nil {
			return nil, err
		}
	}
	if err = b.digitalPins[i].Direction(dir); err != nil {
		return
	}
	return b.digitalPins[i], nil
}

// PWMPin returns matched pwmPin for specified pin number
func (b *Adaptor) PWMPin(pin string) (sysfsPin sysfs.PWMPinner, err error) {
	pinInfo, err := b.translatePwmPin(pin)
	if err != nil {
		return nil, err
	}

	if b.pwmPins[pin] == nil {
		newPin := sysfs.NewPWMPin(pinInfo.channel)
		newPin.Path = pinInfo.path

		if err = muxPWMPin(pin); err != nil {
			return
		}
		if err = newPin.Export(); err != nil {
			return
		}
		if err = newPin.SetPeriod(pwmDefaultPeriod); err != nil {
			return
		}
		// if err = newPin.InvertPolarity(false); err != nil {
		// 	return
		// }
		if err = newPin.Enable(true); err != nil {
			return
		}
		b.pwmPins[pin] = newPin
	}

	sysfsPin = b.pwmPins[pin]

	return
}

// AnalogRead returns an analog value from specified pin
func (b *Adaptor) AnalogRead(pin string) (val int, err error) {
	analogPin, err := b.translateAnalogPin(pin)
	if err != nil {
		return
	}
	fi, err := sysfs.OpenFile(fmt.Sprintf("%v/%v", b.analogPath, analogPin), os.O_RDONLY, 0644)
	defer fi.Close()

	if err != nil {
		return
	}

	var buf = make([]byte, 1024)
	_, err = fi.Read(buf)
	if err != nil {
		return
	}

	val, _ = strconv.Atoi(strings.Split(string(buf), "\n")[0])
	return
}

// GetConnection returns a connection to a device on a specified bus.
// Valid bus number is either 0 or 2 which corresponds to /dev/i2c-0 or /dev/i2c-2.
func (b *Adaptor) GetConnection(address int, bus int) (connection i2c.Connection, err error) {
	if (bus != 0) && (bus != 2) {
		return nil, fmt.Errorf("Bus number %d out of range", bus)
	}
	if b.i2cBuses[bus] == nil {
		b.i2cBuses[bus], err = sysfs.NewI2cDevice(fmt.Sprintf("/dev/i2c-%d", bus))
	}
	return i2c.NewConnection(b.i2cBuses[bus], address), err
}

// GetDefaultBus returns the default i2c bus for this platform
func (b *Adaptor) GetDefaultBus() int {
	return 2
}

// translatePin converts digital pin name to pin position
func (b *Adaptor) translatePin(pin string) (value int, err error) {
	if val, ok := pins[pin]; ok {
		value = val
	} else {
		err = errors.New("Not a valid pin")
	}
	return
}

func (b *Adaptor) translatePwmPin(pin string) (p pwmPinData, err error) {
	if val, ok := pwmPins[pin]; ok {
		p = val
	} else {
		err = errors.New("Not a valid PWM pin")
	}
	return
}

// translateAnalogPin converts analog pin name to pin position
func (b *Adaptor) translateAnalogPin(pin string) (value string, err error) {
	if val, ok := analogPins[pin]; ok {
		value = val
	} else {
		err = errors.New("Not a valid analog pin")
	}
	return
}

func ensureSlot(slots, item string) (err error) {
	fi, err := sysfs.OpenFile(slots, os.O_RDWR|os.O_APPEND, 0666)
	defer fi.Close()
	if err != nil {
		return
	}

	// ensure the slot is not already written into the capemanager
	// (from: https://github.com/mrmorphic/hwio/blob/master/module_bb_pwm.go#L190)
	scanner := bufio.NewScanner(fi)
	for scanner.Scan() {
		line := scanner.Text()
		if strings.Index(line, item) > 0 {
			return
		}
	}

	_, err = fi.WriteString(item)
	if err != nil {
		return err
	}
	fi.Sync()

	scanner = bufio.NewScanner(fi)
	for scanner.Scan() {
		line := scanner.Text()
		if strings.Index(line, item) > 0 {
			return
		}
	}
	return
}

func muxPWMPin(pin string) error {
	path := fmt.Sprintf("/sys/devices/platform/ocp/ocp:%s_pinmux/state", pin)
	fi, e := sysfs.OpenFile(path, os.O_WRONLY, 0666)
	defer fi.Close()
	if e != nil {
		return e
	}
	_, e = fi.WriteString("pwm")
	return e
}