payment_request.go

package mppx

import (
	"encoding/base64"
	"encoding/json"
	"fmt"
)

// SerializePaymentRequest serializes a payment request map to a base64url-encoded canonical JSON string.
// Go's encoding/json sorts map keys, producing deterministic output suitable for HMAC computation.
func SerializePaymentRequest(req map[string]any) string {
	data, err := json.Marshal(req)
	if err != nil {
		return ""
	}
	return base64.RawURLEncoding.EncodeToString(data)
}

// DeserializePaymentRequest decodes a base64url-encoded payment request string into a map.
func DeserializePaymentRequest(encoded string) (map[string]any, error) {
	data, err := base64.RawURLEncoding.DecodeString(encoded)
	if err != nil {
		return nil, fmt.Errorf("mpp: invalid base64url in request: %w", err)
	}
	var result map[string]any
	if err := json.Unmarshal(data, &result); err != nil {
		return nil, fmt.Errorf("mpp: invalid JSON in request: %w", err)
	}
	return result, nil
}