Other: Safer user types

internal/user/types.go

@@ -1,10 +1,17 @@
 package user
 
 import (
+	"context"
+	"encoding/hex"
 	"fmt"
 	"reflect"
+
+	"gitlab.protontech.ch/go/liteapi"
 )
 
+// mapTo converts the slice to the given type.
+// This is not runtime safe, so make sure the slice is of the correct type!
+// (This is a workaround for the fact that slices cannot be converted to other types generically).
 func mapTo[From, To any](from []From) []To {
 	to := make([]To, 0, len(from))
 
@@ -19,3 +26,79 @@ func mapTo[From, To any](from []From) []To {
 
 	return to
 }
+
+// groupBy returns a map of the given slice grouped by the given key.
+// Duplicate keys are overwritten.
+func groupBy[Key comparable, Value any](items []Value, key func(Value) Key) map[Key]Value {
+	groups := make(map[Key]Value)
+
+	for _, item := range items {
+		groups[key(item)] = item
+	}
+
+	return groups
+}
+
+// sortAddr returns whether the first address should be sorted before the second.
+func sortAddr(addrIDA, addrIDB string, apiAddrs map[string]liteapi.Address) bool {
+	return apiAddrs[addrIDA].Order < apiAddrs[addrIDB].Order
+}
+
+// hexEncode returns the hexadecimal encoding of the given byte slice.
+func hexEncode(b []byte) []byte {
+	enc := make([]byte, hex.EncodedLen(len(b)))
+
+	hex.Encode(enc, b)
+
+	return enc
+}
+
+// hexDecode returns the bytes represented by the hexadecimal encoding of the given byte slice.
+func hexDecode(b []byte) ([]byte, error) {
+	dec := make([]byte, hex.DecodedLen(len(b)))
+
+	if _, err := hex.Decode(dec, b); err != nil {
+		return nil, err
+	}
+
+	return dec, nil
+}
+
+// getAddrID returns the address ID for the given email address.
+func getAddrID(apiAddrs []liteapi.Address, email string) (string, error) {
+	for _, addr := range apiAddrs {
+		if addr.Email == email {
+			return addr.ID, nil
+		}
+	}
+
+	return "", fmt.Errorf("address %s not found", email)
+}
+
+// getAddrEmail returns the email address of the given address ID.
+func getAddrEmail(apiAddrs []liteapi.Address, addrID string) (string, error) {
+	for _, addr := range apiAddrs {
+		if addr.ID == addrID {
+			return addr.Email, nil
+		}
+	}
+
+	return "", fmt.Errorf("address %s not found", addrID)
+}
+
+// contextWithStopCh returns a new context that is cancelled when the stop channel is closed or a value is sent to it.
+func contextWithStopCh(ctx context.Context, stopCh <-chan struct{}) (context.Context, context.CancelFunc) {
+	ctx, cancel := context.WithCancel(ctx)
+
+	go func() {
+		select {
+		case <-stopCh:
+			cancel()
+
+		case <-ctx.Done():
+			// ...
+		}
+	}()
+
+	return ctx, cancel
+}