package main

import (
	"encoding/binary"
	"fmt"
	"image"
	"image/color"
	"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/f32"
	"gioui.org/op"
	"gioui.org/op/clip"
	"gioui.org/op/paint"
	"gioui.org/text"
	"gioui.org/unit"
	"gioui.org/widget"
	"gioui.org/widget/material"

	"gioui.org/font/gofont"
)

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 {
	if len(x) < 4 {
		return 0
	}
	flags := x[0]
	if flags&0x80 != 0 { // uint16 format
		return int(binary.BigEndian.Uint16(x[1:3]))
	} else {
		return int(x[1])
	}
}

func eventloop() {
	w := app.NewWindow(
		app.Size(unit.Dp(400), unit.Dp(400)),
		app.Title("HRM"),
	)
	gofont.Register()
	th := material.NewTheme()
	th.TextSize = unit.Sp(fontSize)
	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()
	b.Enable(w)

	state := "starting"
	var hr int
	var periph ble.Peripheral
	var wide bool
	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() {
		f.Layout(gtx,
			f.Rigid(gtx, func() {
				th.Body1("Heart Rate Monitor").Layout(gtx)
			}),
			f.Rigid(gtx, func() {
				th.Body1("Bluetooth is Powered Off").Layout(gtx)
			}),
		)
	}

	appname := func() { th.Body1("Heart Rate Monitor").Layout(gtx) }
	appstate := func() { th.Body1(state).Layout(gtx) }
	periphname := func() { th.Body1(periph.Name).Layout(gtx) }

	leftbar := func() {
		f := &layout.Flex{Axis: layout.Vertical}
		f.Layout(gtx,
			f.Rigid(gtx, appname),
			f.Rigid(gtx, func() { th.Body1("").Layout(gtx) }),
			f.Rigid(gtx, appstate),
		)
	}

	scanlist := 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()
			}
		})
	}

	scanpage = func() {
		if wide {
			f2 := &layout.Flex{Axis: layout.Horizontal}
			f2.Layout(gtx,
				f2.Flex(gtx, 0.2, leftbar),
				f2.Rigid(gtx, scanlist),
			)
		} else {
			f.Layout(gtx,
				f.Rigid(gtx, appname),
				f.Rigid(gtx, appstate),
				f.Rigid(gtx, scanlist),
			)
		}
	}

	connpage = func() {
		f.Layout(gtx,
			f.Rigid(gtx, appname),
			f.Rigid(gtx, func() {
				th.Body1("Connecting").Layout(gtx)
			}),
			f.Rigid(gtx, periphname),
			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
				}
			}),
		)
	}

	hrcircle := func() {
		blue := color.RGBA{0x3f, 0x51, 0xb5, 255}
		white := color.RGBA{255, 255, 255, 255}
		w, h1 := float32(gtx.Constraints.Width.Max), float32(gtx.Constraints.Height.Max)
		if w < h1 {
			h1 = w
		}
		s2 := h1 * 0.9
		r1 := f32.Rectangle{f32.Point{0, 0}, f32.Point{h1, h1}}
		p2a := f32.Point{(h1-s2)/2, (h1-s2)/2}
		p2b := f32.Point{s2 + (h1-s2)/2, s2 + (h1-s2)/2}
		r2 := f32.Rectangle{p2a, p2b}
		clip.Rect{ Rect: r1, NE: h1/2, NW: h1/2, SE: h1/2, SW: h1/2}.Op(gtx.Ops).Add(gtx.Ops)
		paint.ColorOp{Color: blue}.Add(gtx.Ops)
		paint.PaintOp{Rect: r1}.Add(gtx.Ops)
		clip.Rect{ Rect: r2, NE: s2/2, NW: s2/2, SE: s2/2, SW: s2/2}.Op(gtx.Ops).Add(gtx.Ops)
		paint.ColorOp{Color: white}.Add(gtx.Ops)
		paint.PaintOp{Rect: r2}.Add(gtx.Ops)
		op.TransformOp{}.Offset(p2a).Add(gtx.Ops)
		gtx.Constraints.Width.Max = int(s2)
		gtx.Constraints.Height.Max = int(s2)
		gtx.Constraints.Width.Min = int(s2)
		gtx.Constraints.Height.Min = int(s2)
		l := th.H1(fmt.Sprintf("%d", hr))
		l.Alignment = text.Middle
		layout.Align(layout.Center).Layout(gtx, func() {
			l.Layout(gtx)
		})
		gtx.Dimensions.Size = image.Point{int(h1), int(h1)}
	}

	hrpage = func() {
		f.Layout(gtx,
			f.Rigid(gtx, appname),
			f.Rigid(gtx, periphname),
			f.Rigid(gtx, func() {
				layout.UniformInset(unit.Dp(2)).Layout(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.Rigid(gtx, hrcircle),
		)
	}

	page = offpage

	for {
		select {
		case e := <-b.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" {
				if e.Gatt.IsHRM() {
					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" {
				if e.Gatt.IsHRV() {
					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)
				if e.Size.X > e.Size.Y {
					wide = true
				} else {
					wide = false
				}
				resetSysinset(e.Insets)
				sysinset.Layout(gtx, func() {
					margin.Layout(gtx, page)
				})
				e.Frame(gtx.Ops)
			}
		}
	}
}