<?php

namespace App\Support\VideoWorkflow\StepHandlers;

use App\Models\Asset;
use App\Models\WorkflowStep;
use App\Support\AssetStorage\AssetStorage;
use App\Support\VideoWorkflow\WorkflowEngine;
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\File;
use Illuminate\Support\Facades\Process;
use Illuminate\Support\Facades\Storage;

/**
 * Assembles the scene images from a completed video_generation step and
 * (optionally) the project's voiceover audio into an actual video file,
 * via the ffmpeg/ffprobe CLIs. Each scene image is shown for an equal
 * share of the audio's duration (or a fixed duration if there's no
 * audio); no transitions/effects — that's future scope, not what this
 * pass covers.
 */
class VideoEditingHandler implements StepHandler
{
    private const DEFAULT_SECONDS_PER_SCENE = 4.0;

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

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

    public function handle(WorkflowStep $step, WorkflowEngine $engine): void
    {
        $images = $this->resolveSceneImages($step);

        if (! $images || $images->isEmpty()) {
            $engine->failStep($step, 'No scene images available — complete a video_generation step first.');

            return;
        }

        $audioAsset = $this->resolveAudio($step);

        $tempDir = storage_path('app/tmp/video-editing-'.$step->id.'-'.uniqid());
        File::ensureDirectoryExists($tempDir);

        try {
            $imagePaths = $images->map(fn (Asset $a) => Storage::path($a->disk_path))->all();
            $audioPath = $audioAsset ? Storage::path($audioAsset->disk_path) : null;

            $duration = null;

            if ($audioPath) {
                $duration = $this->probeDuration($audioPath);

                if ($duration === null) {
                    $engine->failStep($step, 'Could not read the voiceover audio\'s duration.');

                    return;
                }
            }

            $input = $step->input ?? [];
            $perScene = $input['seconds_per_scene'] ?? ($duration ? $duration / count($imagePaths) : self::DEFAULT_SECONDS_PER_SCENE);

            $concatListPath = "{$tempDir}/concat.txt";
            $this->writeConcatList($concatListPath, $imagePaths, $perScene);

            $silentVideoPath = "{$tempDir}/silent.mp4";
            $result = Process::timeout(300)->run([
                'ffmpeg', '-y', '-f', 'concat', '-safe', '0', '-i', $concatListPath,
                '-vsync', 'vfr', '-pix_fmt', 'yuv420p', $silentVideoPath,
            ]);

            if ($result->failed()) {
                $engine->failStep($step, 'ffmpeg failed to assemble scene images: '.trim($result->errorOutput()));

                return;
            }

            $finalVideoPath = "{$tempDir}/final.mp4";

            if ($audioPath) {
                $result = Process::timeout(300)->run([
                    'ffmpeg', '-y', '-i', $silentVideoPath, '-i', $audioPath,
                    '-c:v', 'copy', '-c:a', 'aac', '-shortest', $finalVideoPath,
                ]);

                if ($result->failed()) {
                    $engine->failStep($step, 'ffmpeg failed to mux the voiceover audio: '.trim($result->errorOutput()));

                    return;
                }
            } else {
                File::copy($silentVideoPath, $finalVideoPath);
            }

            $asset = $this->assets->store(
                $step->videoProject,
                'video',
                File::get($finalVideoPath),
                'mp4',
                step: $step,
                mimeType: 'video/mp4',
                metadata: ['scene_count' => count($imagePaths), 'duration_seconds' => $duration ?? ($perScene * count($imagePaths))],
            );

            $engine->completeStep($step, ['asset_id' => $asset->id]);
        } finally {
            File::deleteDirectory($tempDir);
        }
    }

    private function probeDuration(string $path): ?float
    {
        $result = Process::timeout(60)->run(['ffprobe', '-v', 'error', '-show_entries', 'format=duration', '-of', 'csv=p=0', $path]);

        if ($result->failed()) {
            return null;
        }

        $value = trim($result->output());

        return is_numeric($value) ? (float) $value : null;
    }

    private function writeConcatList(string $path, array $imagePaths, float $secondsPerImage): void
    {
        $lines = [];

        foreach ($imagePaths as $imagePath) {
            $lines[] = "file '".addslashes($imagePath)."'";
            $lines[] = "duration {$secondsPerImage}";
        }

        // ffmpeg's concat demuxer ignores the last entry's duration, so the
        // final image needs to be repeated once more without one.
        $lines[] = "file '".addslashes(end($imagePaths))."'";

        File::put($path, implode("\n", $lines));
    }

    /**
     * @return Collection<int, Asset>|null
     */
    private function resolveSceneImages(WorkflowStep $step): ?Collection
    {
        $input = $step->input ?? [];

        $ids = $input['image_asset_ids'] ?? null;

        if (! $ids) {
            $videoGenStep = $step->videoProject->steps()
                ->where('type', 'video_generation')
                ->where('status', 'completed')
                ->orderByDesc('completed_at')
                ->first();

            $ids = $videoGenStep?->output['asset_ids'] ?? null;
        }

        if (! $ids) {
            return null;
        }

        $assetsById = Asset::whereIn('id', $ids)->get()->keyBy('id');

        return collect($ids)->map(fn ($id) => $assetsById->get($id))->filter()->values();
    }

    private function resolveAudio(WorkflowStep $step): ?Asset
    {
        $input = $step->input ?? [];

        if (! empty($input['audio_asset_id'])) {
            return Asset::find($input['audio_asset_id']);
        }

        return $step->videoProject->assets()
            ->where('type', 'audio')
            ->orderByDesc('version')
            ->first();
    }
}