Fix parent ticket assignment and display

app/Http/Requests/StoreProjectTicketRequest.php

@@ -4,9 +4,12 @@ namespace App\Http\Requests;
 
 use App\Actions\Tickets\Support\AcceptanceCriteriaChecklistMapper;
 use App\Models\Project;
+use App\Models\Ticket;
 use Illuminate\Contracts\Validation\ValidationRule;
 use Illuminate\Foundation\Http\FormRequest;
+use Illuminate\Support\Arr;
 use Illuminate\Validation\Rule;
+use Illuminate\Validation\Validator;
 
 class StoreProjectTicketRequest extends FormRequest
 {
@@ -55,6 +58,11 @@ class StoreProjectTicketRequest extends FormRequest
             'acceptance_criteria.*.indent' => ['required', 'integer', 'min:0', 'max:'.AcceptanceCriteriaChecklistMapper::MAX_INDENT_LEVEL],
             'assignee_user_id' => ['nullable', 'integer', Rule::exists('users', 'id')],
             'description' => ['nullable', 'string'],
+            'parent_ticket_id' => [
+                'nullable',
+                'integer',
+                Rule::exists('tickets', 'id')->where('project_id', $project->id),
+            ],
             'ticket_priority_id' => [
                 'required',
                 'integer',
@@ -74,4 +82,35 @@ class StoreProjectTicketRequest extends FormRequest
             'title' => ['required', 'string', 'max:255'],
         ];
     }
+
+    /**
+     * @return array<int, callable(Validator): void>
+     */
+    public function after(): array
+    {
+        return [
+            function (Validator $validator): void {
+                /** @var array<string, mixed> $validated */
+                $validated = $this->safe()->all();
+
+                /** @var Project $project */
+                $project = $this->route('project');
+
+                $parentTicketId = Arr::get($validated, 'parent_ticket_id');
+
+                if ($parentTicketId === null) {
+                    return;
+                }
+
+                $parentTicket = Ticket::query()
+                    ->where('project_id', $project->id)
+                    ->with('ticketType')
+                    ->find($parentTicketId);
+
+                if ($parentTicket !== null && ! $parentTicket->ticketType?->is_parent) {
+                    $validator->errors()->add('parent_ticket_id', 'Only tickets with a parent-enabled type can be selected as a parent.');
+                }
+            },
+        ];
+    }
 }