package uncanny

import (
	"errors"
	"fmt"
	"log"
	"github.com/brutella/can"
)

const queueSize = 10

type Can struct {
	bus       *can.Bus
	queue     chan func()

	swstate   FeedbackStatus
	dispstate int
}

func NewCan(intf string) (*Can, error) {
	bus, err := can.NewBusForInterfaceWithName(intf)
	if err != nil {
		return nil, errors.New(fmt.Sprintf("Can't open %s: %v", intf, err))
	}
	can := &Can{
		bus:       bus,
		queue:     make(chan func(), queueSize),
		dispstate: -1,
	}
	bus.Subscribe(can)
	return can, nil
}

func (c *Can) Start() error {
	go c.process()
	log.Printf("Starting bus listener")
	return c.bus.ConnectAndPublish()
}

func (c *Can) process() {
	running := true
	log.Printf("Starting processing queue")
	for running {
		select {
		case fn, ok := <-c.queue:
			if ok {
				fn()
			} else {
				running = false
			}
		}
	}
	for range c.queue {}
	log.Printf("Processing queue shut down")
}

func (c *Can) Stop() error {
	log.Printf("Shutting down processing queue and bus listener")
	close(c.queue)
	return c.bus.Disconnect()
}

func (c *Can) Handle(frame can.Frame) {
	c.queue <- func() {
		log.Printf("Got CAN frame to 0x%08x", frame.ID)
		typ, obj, err := DecodeMessage(frame)
		if err != nil {
			if err == UnsupportedMessageType {
				log.Printf("Unsupported message type: 0x%08x", frame.ID)
			} else {
				log.Printf("Cannot decode message: %v", err)
			}
		} else {
			switch typ {
			case MessageTypeFeedbackStatus:
				log.Printf("Got feedback status message: %+v", obj.(FeedbackStatus))
				log.Printf("Data: 0x%02x 0x%02x", frame.Data[0], frame.Data[1])
				c.swstate = obj.(FeedbackStatus)
				// when all end switches are open (i.e. true): send stop command
				if c.swstate.EndD && c.swstate.EndE && c.swstate.EndF && c.swstate.EndG && c.swstate.EndH {
					log.Printf("All end switches off, stopping dispenser")
					c.Cancel()
				}
			case MessageTypePowerStatus:
				log.Printf("Got power status message: %+v", obj.(PowerStatus))
				// ignore
			case MessageTypeDispenseCommand:
				log.Printf("Got dispense command message: %+v", obj.(DispenseCommand))
				c.dispstate = obj.(DispenseCommand).Slot
			case MessageTypeDisplayStatus:
				log.Printf("Got display status message: %+v", obj.(DisplayStatus))
			}
		}
	}
}

func (c *Can) IsEmpty(slot int) bool {
	ret := make(chan bool)
	c.queue <- func() {
		switch (slot) {
		case 0:
			ret <- c.swstate.EmptyD
		case 1:
			ret <- c.swstate.EmptyE
		case 2:
			ret <- c.swstate.EmptyF
		case 3:
			ret <- c.swstate.EmptyG
		case 4:
			ret <- c.swstate.EmptyH
		}
		ret <- false
	}
	return <-ret
}

func (c *Can) IsDispensing(slot int) bool {
	ret := make(chan bool)
	c.queue <- func() {
		switch (slot) {
		case 0:
			ret <- c.swstate.EndD
		case 1:
			ret <- c.swstate.EndE
		case 2:
			ret <- c.swstate.EndF
		case 3:
			ret <- c.swstate.EndG
		case 4:
			ret <- c.swstate.EndH
		}
		ret <- false
	}
	return <-ret
}

func (c *Can) ActiveDispenser() int {
	ret := make(chan int)
	c.queue <- func() {
		ret <- c.dispstate
	}
	return <- ret
}

func (c *Can) Dispense(slot int) {
	c.queue <- func() {
		log.Printf("Starting dispense on slot %d", slot)
		err := c.bus.Publish(DispenseCommand{slot}.Encode())
		if err != nil {
			log.Printf("Error sending dispense command: %v", err)
		}
	}
}

func (c *Can) Cancel() {
	c.queue <- func() {
		log.Printf("Stopping dispense")
		err := c.bus.Publish(DispenseCommand{DispenseSlotOff}.Encode())
		if err != nil {
			log.Printf("Error sending stop command: %v", err)
		}
	}
}

func (c *Can) Initialize() {
	c.queue <- func() {
		log.Printf("Initializing devices")
		// enable automatic status updates
		c.bus.Publish(AutoCommand{true}.Encode())
		c.bus.Publish(EncodeFeedbackRequest())
		c.bus.Publish(EncodePowerRequest())
		c.bus.Publish(EncodeDisplayRequest())
	}
}