package logic

import (
	"crypto/sha256"
	"encoding/binary"
	"encoding/hex"
	"fmt"
	"strings"

	deviceentity "spark-server/internal/module/device/entity"
)

// FingerprintInput is the physical identity for one login/register.
type FingerprintInput struct {
	DeviceType deviceentity.DeviceType
	IDFV       string
	AndroidID  string
}

func fingerprintHash(in FingerprintInput) (string, error) {
	if !in.DeviceType.Valid() {
		return "", fmt.Errorf("device_type")
	}
	idfv := strings.TrimSpace(in.IDFV)
	androidID := strings.TrimSpace(in.AndroidID)
	var tail string
	switch in.DeviceType {
	case deviceentity.TypeIOS, deviceentity.TypeMacOS:
		if idfv == "" {
			return "", fmt.Errorf("idfv")
		}
		tail = idfv
	case deviceentity.TypeAndroid, deviceentity.TypeHarmony:
		if androidID == "" {
			return "", fmt.Errorf("android_id")
		}
		tail = androidID
	default:
		switch {
		case idfv != "":
			tail = idfv
		case androidID != "":
			tail = androidID
		default:
			return "", fmt.Errorf("device_id")
		}
	}
	payload := fmt.Sprintf("%d:%s", in.DeviceType, tail)
	sum := sha256.Sum256([]byte(payload))
	return hex.EncodeToString(sum[:]), nil
}

// DeviceIDFromFingerprint derives the stable business device id.
func DeviceIDFromFingerprint(in FingerprintInput) (uint64, string, error) {
	hash, err := fingerprintHash(in)
	if err != nil {
		return 0, "", err
	}
	sum := sha256.Sum256([]byte(hash))
	id := binary.BigEndian.Uint64(sum[:8])
	if id == 0 {
		id = binary.BigEndian.Uint64(sum[1:9])
	}
	if id == 0 {
		id = 1
	}
	return id, hash, nil
}