Calculation errors for refunded amounts

app/Models/ParticipantRefund.php

@@ -4,6 +4,7 @@ namespace App\Models;
 
 use App\Casts\AmountCast;
 use App\Enumerations\RefundReason;
+use App\Enumerations\RetentionReason;
 use App\Scopes\InstancedModel;
 use App\ValueObjects\Amount;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
@@ -20,6 +21,9 @@ use Illuminate\Database\Eloquent\Relations\BelongsTo;
  * @property Amount|null $amount
  * @property string|null $reason
  * @property string|null $reason_note
+ * @property string|null $retention_reason
+ * @property string|null $retention_reason_note
+ * @property Amount|null $retained_amount
  * @property string|null $account_owner
  * @property string|null $account_iban
  * @property int|null $captured_by
@@ -51,6 +55,9 @@ class ParticipantRefund extends InstancedModel
         'amount',
         'reason',
         'reason_note',
+        'retention_reason',
+        'retention_reason_note',
+        'retained_amount',
         'account_owner',
         'account_iban',
         'captured_by',
@@ -63,6 +70,7 @@ class ParticipantRefund extends InstancedModel
 
     protected $casts = [
         'amount' => AmountCast::class,
+        'retained_amount' => AmountCast::class,
         'released_at' => 'datetime',
         'accepted_at' => 'datetime',
         'cancelled_at' => 'datetime',
@@ -129,4 +137,32 @@ class ParticipantRefund extends InstancedModel
     {
         return (string) ($this->reasonRelation()->first()?->name ?? '');
     }
+
+    /** Der Einbehaltungsgrund als Stammdatensatz -- leer, wenn voll erstattet wurde. */
+    public function retentionReasonRelation(): BelongsTo
+    {
+        return $this->belongsTo(RetentionReason::class, 'retention_reason', 'slug');
+    }
+
+    public function retentionReasonLabel(): string
+    {
+        return (string) ($this->retentionReasonRelation()->first()?->name ?? '');
+    }
+
+    /** Der auf dem Beleg auszuweisende Text zur Einbehaltung. */
+    public function retentionReasonText(): string
+    {
+        return $this->retentionReasonRelation()->first()?->documentText($this->retention_reason_note) ?? '';
+    }
+
+    /**
+     * Ob etwas beim Verband bleibt -- die halbe Cent-Toleranz fängt die Float-Rundung ab.
+     *
+     * Der Betrag steht in `retained_amount` und wird beim Einreichen festgeschrieben. Ihn zur Laufzeit
+     * aus `amount_paid` zu rechnen ginge schief: Danach führt das Feld bereits den Rest.
+     */
+    public function hasRetention(): bool
+    {
+        return ($this->retained_amount?->getAmount() ?? 0.0) > 0.005;
+    }
 }