muninn/app/Support/VideoWorkflow/StepHandlers/ThumbnailGenerationHandler.php

<?php

namespace App\Support\VideoWorkflow\StepHandlers;

use App\Models\AiProvider;
use App\Models\VideoProject;
use App\Models\WorkflowStep;
use App\Support\AiProviders\AiGenerationException;
use App\Support\AiProviders\AiProviderManager;
use App\Support\AssetStorage\AssetStorage;
use App\Support\VideoWorkflow\WorkflowEngine;

/**
 * Generates thumbnail candidates via a StabilityAI-backed AiProvider. One
 * variant per style in step.input.styles (default: two contrasting styles),
 * all stored as assets on the same step — the approval UI already shows
 * every asset on an awaiting_approval step side by side, so this is the
 * A/B comparison the task calls for, with no extra UI needed.
 */
class ThumbnailGenerationHandler implements StepHandler
{
    private const DEFAULT_STYLES = ['vibrant and colorful', 'minimalist and clean'];

    public function __construct(
        private readonly AiProviderManager $aiProviders,
        private readonly AssetStorage $assets,
    ) {}

    public function type(): string
    {
        return 'thumbnail_generation';
    }

    public function handle(WorkflowStep $step, WorkflowEngine $engine): void
    {
        $provider = AiProvider::query()->where('provider', 'stability_ai')->where('is_active', true)->first();

        if (! $provider) {
            $engine->failStep($step, 'No active StabilityAI provider configured.');

            return;
        }

        $input = $step->input ?? [];
        $basePrompt = $input['prompt'] ?? $this->defaultPrompt($step->videoProject);
        $styles = $input['styles'] ?? self::DEFAULT_STYLES;

        $assetIds = [];

        foreach (array_values($styles) as $i => $style) {
            $prompt = "{$basePrompt}. Eye-catching YouTube thumbnail, bold, high contrast, {$style}.";

            try {
                $result = $this->aiProviders->generate($provider, $prompt);
            } catch (AiGenerationException $e) {
                $engine->failStep($step, 'variant '.($i + 1).": {$e->getMessage()}");

                return;
            }

            $extension = str($result->contentType)->after('image/')->toString() ?: 'png';

            $asset = $this->assets->store(
                $step->videoProject,
                'image',
                $result->content,
                $extension,
                step: $step,
                mimeType: $result->contentType,
                metadata: ['kind' => 'thumbnail', 'variant' => $i + 1, 'style' => $style],
            );

            $assetIds[] = $asset->id;
        }

        $engine->completeStep($step, [
            'asset_ids' => $assetIds,
            'variant_count' => count($assetIds),
        ]);
    }

    private function defaultPrompt(VideoProject $project): string
    {
        return trim(($project->title ?? '').'. '.($project->description ?? ''));
    }
}