package signature

import (
	"crypto/hmac"
	"crypto/sha512"
	"encoding/hex"
	"errors"
	"strings"
	"time"

	"edge-infra.dev/pkg/edge/datasync/internal/config"
)

type MessageSignatureContext struct {
	MessageID   string
	MessageType string
	Payload     []byte
	Timestamp   time.Time
}

func Generate(sharedKey string, secretKey string, messageContext MessageSignatureContext, organizationName string) (string, error) {
	if sharedKey == "" || secretKey == "" {
		return "", errors.New("failed to sign message. missing keys")
	}

	signableContent := getSignableContent(messageContext, organizationName)
	// if err != nil {
	// 	return "", fmt.Errorf("failed to sign content. %v", err.Error())
	// }

	authenticationHash := GenerateHmac(secretKey, signableContent, messageContext.Timestamp)

	return sharedKey + ":" + authenticationHash, nil
}

func getSignableContent(messageContext MessageSignatureContext, organizationName string) string {
	appKey := config.GetAppKey()

	values := make([]string, 0)

	// h := md5.New()
	// _, err := io.WriteString(h, string(messageContext.Payload))
	// if err != nil {
	// 	return "", fmt.Errorf("failed to write payload with md5. %v", err.Error())
	// }

	// md5Checksum := h.Sum(nil)

	values = append(values, appKey)
	// values = append(values, string(md5Checksum))
	values = append(values, string(messageContext.Payload)) // TODO: maybe dont
	values = append(values, messageContext.MessageID)
	values = append(values, organizationName)

	valuesWithContent := make([]string, 0)
	for _, value := range values {
		if value != "" {
			valuesWithContent = append(valuesWithContent, value)
		}
	}

	signableContent := strings.Join(valuesWithContent, "\n")
	//fmt.Println(signableContent)
	return signableContent
}

func GenerateHmac(secretKey string, signableContent string, timestamp time.Time) string {
	iso8601Timestamp := timestamp.Format(time.RFC3339)

	uniqueKey := secretKey + iso8601Timestamp

	// Create a new HMAC by defining the hash type and the key (as byte array)
	h := hmac.New(sha512.New, []byte(uniqueKey))
	// Write Data to it
	_, err := h.Write([]byte(signableContent))
	if err != nil {
		return ""
	}
	// Get result and encode as hexadecimal string
	sha := hex.EncodeToString(h.Sum(nil))

	return sha
}