res_levis_backend/cmd/decoder-parser-testbench/main.go

package main

import (
	"bytes"
	"encoding/binary"
	"encoding/json"
	"fmt"
	"io"
	"os"
	"sync"

	"github.com/AFASystems/presence/internal/pkg/model"
)

type parserConfig struct {
	Length int    `json:"length"`
	Offset int    `json:"offset"`
	Order  string `json:"order"`
}

type beaconParser struct {
	name     string
	canParse func([]byte) bool
	configs  map[string]parserConfig
}

type parserRegistry struct {
	parserList []beaconParser
	rw         sync.RWMutex
}

type config struct {
	Name    string                  `json:"name"`
	Min     int                     `json:"min"`
	Max     int                     `json:"max"`
	Pattern []string                `json:"pattern"`
	Configs map[string]parserConfig `json:"configs"`
}

func (pc parserConfig) GetOrder() binary.ByteOrder {
	if pc.Order == "bigendian" {
		return binary.BigEndian
	}

	return binary.LittleEndian
}

func (p *parserRegistry) Register(name string, c config) {
	p.rw.Lock()
	defer p.rw.Unlock()

	b := beaconParser{
		name: name,
		canParse: func(ad []byte) bool {
			return len(ad) >= c.Min && len(ad) <= c.Max && bytes.HasPrefix(ad, c.GetPatternBytes())
		},
		configs: c.Configs,
	}

	p.parserList = append(p.parserList, b)
}

func (b *beaconParser) Parse(ad []byte) (model.BeaconEvent, bool) {
	flag := false
	event := model.BeaconEvent{Type: b.name}
	if cfg, ok := b.configs["battery"]; ok {
		event.Battery = uint32(b.extract(ad, cfg))
		flag = true
	}
	if cfg, ok := b.configs["accX"]; ok {
		event.AccX = int16(b.extract(ad, cfg))
		flag = true
	}
	if cfg, ok := b.configs["accY"]; ok {
		event.AccY = int16(b.extract(ad, cfg))
		flag = true
	}
	if cfg, ok := b.configs["accZ"]; ok {
		event.AccZ = int16(b.extract(ad, cfg))
		flag = true
	}
	return event, flag
}

func (b *beaconParser) extract(ad []byte, pc parserConfig) uint16 {
	if len(ad) < pc.Offset+pc.Length {
		return 0
	}
	data := ad[pc.Offset : pc.Offset+pc.Length]

	if pc.Length == 1 {
		return uint16(data[0])
	}

	return pc.GetOrder().Uint16(data)
}

func (c config) GetPatternBytes() []byte {
	res := make([]byte, len(c.Pattern))
	for i, s := range c.Pattern {
		fmt.Sscanf(s, "0x%02x", &res[i])
	}
	return res
}

func main() {
	parserRegistry := parserRegistry{
		parserList: make([]beaconParser, 0),
	}
	seq := []byte{0x02, 0x01, 0x06, 0x64, 0x01, 0xF4, 0x00, 0x0A, 0xFF, 0x05}

	jsonFile, err := os.Open("configs.json")
	if err != nil {
		fmt.Println(err)
	}

	fmt.Println("succesfully opened json file")

	b, _ := io.ReadAll(jsonFile)
	var configs []config
	json.Unmarshal(b, &configs)
	for _, config := range configs {
		parserRegistry.Register(config.Name, config)
	}

	for _, parser := range parserRegistry.parserList {
		if parser.canParse(seq) {
			event, ok := parser.Parse(seq)
			if ok {
				fmt.Printf("Device: %s | Battery: %d%% | AccX: %d | AccY: %d | AccZ: %d\n", event.Type, event.Battery, event.AccX, event.AccY, event.AccZ)
			}
		}
	}

	fmt.Printf("configs: %+v\n", configs)
	jsonFile.Close()
}