// This is a sensor station that uses a RTL8720DN running on the device UART2.
// It creates an MQTT connection that publishes a message every second
// to an MQTT broker.
//
// In other words:
// Your computer <--> USB-CDC <--> MCU <--> UART2 <--> RTL8720DN <--> Internet <--> MQTT broker.
//
// You must install the Paho MQTT package to build this program:
//
// 		go get -u github.com/eclipse/paho.mqtt.golang
//
// You can check that mqttpub is running successfully with the following command.
//
// 		mosquitto_sub -h test.mosquitto.org -t tinygo
//
package main

import (
	"fmt"
	"math/rand"
	"time"

	"tinygo.org/x/drivers/net"
	"tinygo.org/x/drivers/net/mqtt"
	"tinygo.org/x/drivers/rtl8720dn"
)

// You can override the setting with the init() in another source code.
// func init() {
//    ssid = "your-ssid"
//    password = "your-password"
//    debug = true
//    server = "tinygo.org"
// }

var (
	ssid     string
	password string
	server   string = "tcp://test.mosquitto.org:1883"
	debug           = false
)

var buf [0x400]byte

var lastRequestTime time.Time
var conn net.Conn
var adaptor *rtl8720dn.RTL8720DN

func main() {
	err := run()
	for err != nil {
		fmt.Printf("error: %s\r\n", err.Error())
		time.Sleep(5 * time.Second)
	}
}

var (
	topic = "tinygo"
)

func run() error {
	rtl, err := setupRTL8720DN()
	if err != nil {
		return err
	}
	net.UseDriver(rtl)

	err = rtl.ConnectToAccessPoint(ssid, password, 10*time.Second)
	if err != nil {
		return err
	}

	ip, subnet, gateway, err := rtl.GetIP()
	if err != nil {
		return err
	}
	fmt.Printf("IP Address : %s\r\n", ip)
	fmt.Printf("Mask       : %s\r\n", subnet)
	fmt.Printf("Gateway    : %s\r\n", gateway)

	rand.Seed(time.Now().UnixNano())

	opts := mqtt.NewClientOptions()
	opts.AddBroker(server).SetClientID("tinygo-client-" + randomString(10))

	println("Connectng to MQTT...")
	cl := mqtt.NewClient(opts)
	if token := cl.Connect(); token.Wait() && token.Error() != nil {
		failMessage(token.Error().Error())
	}

	for i := 0; ; i++ {
		println("Publishing MQTT message...")
		data := []byte(fmt.Sprintf(`{"e":[{"n":"hello %d","v":101}]}`, i))
		token := cl.Publish(topic, 0, false, data)
		token.Wait()
		if err := token.Error(); err != nil {
			return err
		}
		time.Sleep(100 * time.Millisecond)
	}

	// Right now this code is never reached. Need a way to trigger it...
	println("Disconnecting MQTT...")
	cl.Disconnect(100)

	println("Done.")

	return nil
}

// Returns an int >= min, < max
func randomInt(min, max int) int {
	return min + rand.Intn(max-min)
}

// Generate a random string of A-Z chars with len = l
func randomString(len int) string {
	bytes := make([]byte, len)
	for i := 0; i < len; i++ {
		bytes[i] = byte(randomInt(65, 90))
	}
	return string(bytes)
}

func failMessage(msg string) {
	for {
		println(msg)
		time.Sleep(1 * time.Second)
	}
}