package main

import (
	"encoding/binary"
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"path"

	"git.wow.st/gmp/ble"

	"gopkg.in/yaml.v2"

	"gioui.org/app"
	"gioui.org/io/system"
	"gioui.org/layout"
	"gioui.org/text"
	"gioui.org/unit"
	"gioui.org/widget"
	"gioui.org/widget/material"

	"gioui.org/font/gofont"

	_ "gioui.org/permission/bluetooth"
)

type conf struct {
	Autoconnect string
}

var Config conf
var conffile string

func main() {
	conffile = path.Join(getConfDir(), "config.yml")
	if _, err := os.Stat(conffile); os.IsNotExist(err) {
		fd, err := os.Create(conffile)
		if err != nil {
			log.Fatal("Cannot create configuration file: ", err)
		}
		fd.Close()
	}

	confbytes, err := ioutil.ReadFile(conffile)
	if err != nil {
		log.Fatal("Cannot read configuration file: ", err)
	}
	if err = yaml.UnmarshalStrict(confbytes, &Config); err != nil {
		log.Fatal("Cannot parse configuration file: ", err)
	}
	go eventloop()
	app.Main()
}

func saveConfig() {
	confbytes, err := yaml.Marshal(&Config)
	if err != nil {
		log.Fatal("Cannot encode configuration: ", err)
	}
	err = ioutil.WriteFile(conffile, confbytes, 0700)
}

func hrDecode(x []byte) int {
	flags := x[0]
	if flags&0x80 != 0 { // uint16 format
		return int(binary.BigEndian.Uint16(x[1:2]))
	} else {
		return int(x[1])
	}
}

func eventloop() {
	w := app.NewWindow(
		app.Size(unit.Dp(400), unit.Dp(400)),
		app.Title("HRM"),
	)
	ble.Init() // allow ble driver to set up the JVM on Android
	gofont.Register()
	th := material.NewTheme()
	gtx := &layout.Context{Queue: w.Queue()}

	sysinset := &layout.Inset{}
	resetSysinset := func(x system.Insets) {
		sysinset.Top = x.Top
		sysinset.Bottom = x.Bottom
		sysinset.Left = x.Left
		sysinset.Right = x.Right
	}
	margin := layout.UniformInset(unit.Dp(10))

	b := ble.NewBLE()

	state := "starting"
	var hr int
	var periph ble.Peripheral
	periphs := make([]ble.Peripheral, 0)
	btns := make([]*widget.Button, 0)
	backBtn := &widget.Button{}

	var page, offpage, scanpage, connpage, hrpage func()

	f := &layout.Flex{Axis: layout.Vertical}
	offpage = func() {
		c1 := f.Rigid(gtx, func() {
			th.Body1("Heart Rate Monitor").Layout(gtx)
		})
		c2 := f.Rigid(gtx, func() {
			th.Body1("Bluetooth is Powered Off").Layout(gtx)
		})
		f.Layout(gtx, c1, c2)
	}
	scanpage = func() {
		c1 := f.Rigid(gtx, func() {
			th.Body1("Heart Rate Monitor").Layout(gtx)
		})
		c2 := f.Rigid(gtx, func() {
			th.Body1(state).Layout(gtx)
		})
		c3 := f.Rigid(gtx, func() {
			lst := &layout.List{Axis: layout.Vertical}
			lst.Layout(gtx, len(periphs), func(i int) {
				gtx.Constraints.Width.Min = gtx.Constraints.Width.Max
				layout.UniformInset(unit.Dp(2)).Layout(gtx, func() {
					th.Button(periphs[i].Name).Layout(gtx, btns[i])
				})
				if btns[i].Clicked(gtx) {
					b.StopScan()
					periph = periphs[i]
					b.Connect(periph)
					state = "connecting"
					page = connpage
					w.Invalidate()
				}
			})
		})
		f.Layout(gtx, c1, c2, c3)
	}

	connpage = func() {
		c1 := f.Rigid(gtx, func() {
			th.Body1("Heart Rate Monitor").Layout(gtx)
		})
		c2 := f.Rigid(gtx, func() {
			th.Body1("Connecting").Layout(gtx)
		})
		c3 := f.Rigid(gtx, func() {
			th.Body1(periph.Name).Layout(gtx)
		})
		c4 := f.Rigid(gtx, func() {
			th.Button("Cancel").Layout(gtx, backBtn)
			if backBtn.Clicked(gtx) {
				ble.CancelConnection(periph)
				periphs = periphs[:0]
				Config.Autoconnect = ""
				saveConfig()
				b.Scan()
				state = "scanning"
				page = scanpage
			}
		})
		f.Layout(gtx, c1, c2, c3, c4)
	}

	hrpage = func() {
		c1 := f.Rigid(gtx, func() {
			th.Body1("Heart Rate Monitor").Layout(gtx)
		})
		c2 := f.Rigid(gtx, func() {
			th.Body1(periph.Name).Layout(gtx)
		})
		c3 := f.Rigid(gtx, func() {
			l := th.H1(fmt.Sprintf("%d", hr))
			l.Alignment = text.Middle
			l.Layout(gtx)
		})
		c4 := f.Rigid(gtx, func() {
			th.Button("Stop").Layout(gtx, backBtn)
			if backBtn.Clicked(gtx) {
				ble.Disconnect(periph)
				periphs = periphs[:0]
				Config.Autoconnect = ""
				saveConfig()
				b.Scan()
				state = "scanning"
				page = scanpage
			}
		})
		f.Layout(gtx, c1, c2, c3, c4)
	}

	page = offpage

	events := b.Events()

	for {
		select {
		case e := <-events:
			switch e := e.(type) {
			case ble.UpdateStateEvent:
				fmt.Printf("UpdateState: %s\n", e.State)
				state = e.State
				if state != "powered on" {
					periphs = periphs[:0]
					page = offpage
				} else {

					if Config.Autoconnect != "" && b.Connect(ble.Peripheral{Identifier: Config.Autoconnect}) {
						state = "connecting"
						page = connpage
					} else {
						periphs = periphs[:0]
						state = "scanning"
						page = scanpage
						b.Scan()
					}
				}
			case ble.DiscoverPeripheralEvent:
				fmt.Printf("found %s (%s)\n", e.Peripheral.Name, e.Peripheral.Identifier)
				periphs = append(periphs, e.Peripheral)
				btns = append(btns, &widget.Button{})
				if e.Peripheral.Identifier == Config.Autoconnect && b.Connect(e.Peripheral) {
					state = "connecting"
					page = connpage
				}
			case ble.ConnectEvent:
				fmt.Printf("Connect event\n")
				b.StopScan()
				state = "connected"
				periph = e.Peripheral
				Config.Autoconnect = periph.Identifier
				saveConfig()
				e.Peripheral.DiscoverServices()
				page = hrpage
			case ble.ConnectTimeoutEvent:
				fmt.Printf("Connect timeout\n")
				state = "timeout"
				periphs = periphs[:0]
				page = scanpage
				Config.Autoconnect = ""
				saveConfig()
				b.Scan()
			case ble.DiscoverServiceEvent:
				fmt.Printf("DiscoverService %s\n", e.Gatt.UUID)
				if e.Gatt.UUID == "180D" {
					fmt.Printf("Found HRM Service\n")
					e.Peripheral.DiscoverCharacteristics(e.Service)
				}
			case ble.DiscoverCharacteristicEvent:
				fmt.Printf("DiscoverCharacteristic %s\n", e.Gatt.UUID)
				if e.Gatt.UUID == "2A37" {
					fmt.Printf("Found heart rate value\n")
					e.Peripheral.SetNotifyValue(e.Characteristic)
				}
			case ble.UpdateValueEvent:
				hr = hrDecode(e.Data)
			}
			w.Invalidate() // refresh on any Bluetooth event
		case e := <-w.Events():
			switch e := e.(type) {
			case system.DestroyEvent:
				return
			case system.FrameEvent:
				gtx.Reset(e.Config, e.Size)
				resetSysinset(e.Insets)
				sysinset.Layout(gtx, func() {
					margin.Layout(gtx, page)
				})
				e.Frame(gtx.Ops)
			}
		}
	}
}