package main

import (
	"encoding/binary"
	"fmt"
	"os/exec"
	"time"

	"github.com/google/gousb"
	"tinygo.org/x/bluetooth"
)

func oldMain() {

	var vendorId gousb.ID = 0x0fcf
	var productId gousb.ID = 0x1008
	var deviceNumber uint32 = 3001

	listenForAntDevice(vendorId, productId, deviceNumber)

	fmt.Println("channel closed")
}

var adapter = bluetooth.DefaultAdapter

func main() {
	exec.Command("hciconfig", "hci0", "down").Run()
	exec.Command("hciconfig", "hci0", "up").Run()

	must(adapter.Enable())

	var powerChar bluetooth.Characteristic

	must(adapter.AddService(&bluetooth.Service{
		UUID: bluetooth.New16BitUUID(0x1818),
		Characteristics: []bluetooth.CharacteristicConfig{
			{
				UUID:  bluetooth.New16BitUUID(0x2A65), // Cycling Power Feature
				Flags: bluetooth.CharacteristicReadPermission,
				Value: []byte{0, 0, 0, 0},
			},
			{
				UUID:   bluetooth.New16BitUUID(0x2A63), // Cycling Power Measurement
				Flags:  bluetooth.CharacteristicNotifyPermission,
				Handle: &powerChar,
			},
		},
	}))

	must(adapter.DefaultAdvertisement().Configure(bluetooth.AdvertisementOptions{
		LocalName:    "LinuxAntBtBridge",
		ServiceUUIDs: []bluetooth.UUID{bluetooth.New16BitUUID(0x1818)},
	}))
	must(adapter.DefaultAdvertisement().Start())
	fmt.Println("BLE advertising...")
	var crankRevs uint16
	var lastCrankEventTime uint16

	for {
		sec := time.Now().Second()
		watts := uint16(100 + sec)
		rpm := uint16(50 + sec)

		// advance crank event time based on rpm
		// time between crank events = 1024*60/rpm ticks
		crankEventInterval := uint16(1024 * 60 / rpm)
		lastCrankEventTime += crankEventInterval
		crankRevs++

		// flags: bit 5 = crank revolution data present
		payload := make([]byte, 8)
		binary.LittleEndian.PutUint16(payload[0:], 0x20)
		binary.LittleEndian.PutUint16(payload[2:], watts)
		binary.LittleEndian.PutUint16(payload[4:], crankRevs)
		binary.LittleEndian.PutUint16(payload[6:], lastCrankEventTime)

		powerChar.Write(payload)
		fmt.Printf("watts: %d  rpm: %d  crankRevs: %d  eventTime: %d\n", watts, rpm, crankRevs, lastCrankEventTime)

		time.Sleep(time.Second)
	}
}

func must(err error) {
	if err != nil {
		panic(err)
	}
}