<?php

namespace App\Modules\CustomField\Actions;

use App\Models\User;
use App\Modules\Client\Models\Client;
use App\Modules\CustomField\Models\CustomFieldDefinition;
use App\Modules\CustomField\Models\CustomFieldValue;
use App\Modules\History\Models\HistoryEntry;
use App\Modules\History\Models\HistoryEntryType;
use Illuminate\Support\Facades\DB;

final class UpdateCustomFieldValueAction
{
    /**
     * Upsert a client's value for one custom field. When the value actually
     * changes, append a read-only entry to the Verlauf log (history_entries)
     * so every base-data change is audited alongside the manual notes.
     */
    public function handle(
        Client $client,
        CustomFieldDefinition $definition,
        ?string $value,
        User $author
    ): CustomFieldValue {
        $new = $value === null || $value === '' ? null : (string) $value;

        return DB::transaction(function () use ($client, $definition, $new, $author) {
            $record = CustomFieldValue::firstOrNew([
                'client_id' => $client->id,
                'custom_field_definition_id' => $definition->id,
            ]);

            $old = $record->value;

            if ($old === $new) {
                return $record;
            }

            $record->value = $new;
            $record->author_id = $author->id;
            $record->save();

            HistoryEntry::create([
                'client_id' => $client->id,
                'type' => HistoryEntryType::FieldChange,
                'body' => $this->changeBody($definition->label, $old, $new),
                'custom_field_definition_id' => $definition->id,
                'author_id' => $author->id,
            ]);

            return $record;
        });
    }

    private function changeBody(string $label, ?string $old, ?string $new): string
    {
        if ($old === null) {
            return "{$label} gesetzt: „{$new}“";
        }

        if ($new === null) {
            return "{$label} entfernt (war „{$old}“)";
        }

        return "{$label} geändert: „{$old}“ → „{$new}“";
    }
}