// https://medium.com/coinmonks/iot-tutorial-read-tags-from-a-usb-rfid-reader-with-raspberry-pi-and-node-red-from-scratch-4554836be127
// nolint: gochecknoglobals, lll, forbidigo
package main

import (
	"fmt"
	"log"
	"os"
)

const newLine = 40

var charMap = map[byte]string{
	4:  "a",
	5:  "b",
	6:  "c",
	7:  "d",
	8:  "e",
	9:  "f",
	10: "g",
	11: "h",
	12: "i",
	13: "j",
	14: "k",
	15: "l",
	16: "m",
	17: "n",
	18: "o",
	19: "p",
	20: "q",
	21: "r",
	22: "s",
	23: "t",
	24: "u",
	25: "v",
	26: "w",
	27: "x",
	28: "y",
	29: "z",
	30: "1",
	31: "2",
	32: "3",
	33: "4",
	34: "5",
	35: "6",
	36: "7",
	37: "8",
	38: "9",
	39: "0",
}

func main() {
	d, err := os.Open("/dev/hidraw7")
	if err != nil {
		log.Fatal(err)
	}

	id := make(chan string)

	go func() {
		buf := make([]byte, 3)

		rfid := ""

		for {
			// Reading the RFID reader.
			_, err := d.Read(buf)
			if err != nil {
				log.Print(err)

				continue
			}

			// 40 means "\n" and is an indicator that the input is complete.
			// Send the id string to the consumer channel.
			if buf[2] == newLine {
				id <- rfid
				rfid = ""

				continue
			}

			// Check if byte is in the charMap and if its true, append it to the rfid string.
			// It waits till next read and checks for the newline byte.
			c, ok := charMap[buf[2]]
			if ok {
				rfid += c
			}
		}
	}()

	// Wait for an RFID ID and do something with it.
	for {
		rfid := <-id
		fmt.Println(rfid)
	}
}