package decoder

import (
	"bytes"
	"context"
	"encoding/hex"
	"fmt"
	"strings"

	"github.com/AFASystems/presence/internal/pkg/common/appcontext"
	"github.com/AFASystems/presence/internal/pkg/common/utils"
	"github.com/AFASystems/presence/internal/pkg/model"
	"github.com/segmentio/kafka-go"
)

// processIncoming processes incoming beacon advertisements
func processIncoming(adv model.BeaconAdvertisement, appState *appcontext.AppState, writer kafkaWriter, parserRegistry *model.ParserRegistry) {
	err := decodeBeacon(adv, appState, writer, parserRegistry)
	if err != nil {
		eMsg := fmt.Sprintf("Error in decoding: %v", err)
		fmt.Println(eMsg)
		return
	}
}

// decodeBeacon decodes beacon data and publishes events
func decodeBeacon(adv model.BeaconAdvertisement, appState *appcontext.AppState, writer kafkaWriter, parserRegistry *model.ParserRegistry) error {
	beacon := strings.TrimSpace(adv.Data)
	id := adv.ID
	if beacon == "" {
		return nil
	}

	b, err := hex.DecodeString(beacon)
	if err != nil {
		return err
	}

	b = utils.RemoveFlagBytes(b)

	indeces := utils.ParseADFast(b)
	event := utils.LoopADStructures(b, indeces, id, parserRegistry)

	if event.ID == "" {
		return nil
	}

	prevEvent, ok := appState.GetBeaconEvent(id)
	appState.UpdateBeaconEvent(id, event)
	if ok && bytes.Equal(prevEvent.Hash(), event.Hash()) {
		return nil
	}

	eMsg, err := event.ToJSON()
	if err != nil {
		return err
	}

	if err := writer.WriteMessages(context.Background(), kafka.Message{Value: eMsg}); err != nil {
		return err
	}

	return nil
}

// kafkaWriter interface defines the methods we need from kafka.Writer
type kafkaWriter interface {
	WriteMessages(ctx context.Context, msgs ...kafka.Message) error
}