<?php

namespace App\Helpers\FirstParty\Render;

use App\Models\Video;
use Illuminate\Support\Collection;
use Illuminate\Support\Str;
use Symfony\Component\Process\Process;

/**
 * Class FfmpegVideoRenderer
 *
 * Builds and optionally executes an ffmpeg command using VideoElement models and render settings.
 */
class FfmpegVideoRenderer
{
    /**
     * Render the given Video to a file via ffmpeg.
     *
     * @return object { string $name, string $path }
     *
     * @throws \InvalidArgumentException if required elements missing
     * @throws \RuntimeException on ffmpeg failure
     */
    public static function render(Video $video): object
    {
        $elements = self::get_video_elements($video);
        $settings = self::get_render_settings($video);

        // Gather elements by type and sort by time
        $slide_images = $elements->where('external_reference', 'slideshow')->sortBy('time')->values();
        $overlay_images = $elements->where('type', 'image')
            ->where('external_reference', '!=', 'slideshow')
            ->sortBy('time')
            ->values();
        $video_element = $elements->firstWhere('type', 'video');
        $audio_tracks = $elements->where('type', 'audio')->sortBy('time')->values();

        if ($slide_images->isEmpty() || ! $video_element) {
            throw new \InvalidArgumentException('At least one slideshow and one video element are required.');
        }

        // Build ffmpeg input arguments
        $input_args = [];
        foreach ($slide_images as $slide) {
            $duration = number_format($slide->duration, 2);
            $input_args[] = "-loop 1 -t {$duration} -i \"{$slide->asset_url}\"";
        }
        foreach ($overlay_images as $overlay) {
            $duration = number_format($overlay->duration, 2);
            $input_args[] = "-loop 1 -t {$duration} -i \"{$overlay->asset_url}\"";
        }
        $input_args[] = "-i \"{$video_element->asset_url}\"";
        foreach ($audio_tracks as $audio) {
            $input_args[] = "-i \"{$audio->asset_url}\"";
        }

        // Build filter_complex chains
        $filters = [];
        $slide_count = $slide_images->count();
        $concat_input = '';
        for ($i = 0; $i < $slide_count; $i++) {
            $concat_input .= "[{$i}:v]";
        }
        $filters[] = "{$concat_input}concat=n={$slide_count}:v=1:a=0[slideshow]";

        $current_label = 'slideshow';
        foreach ($overlay_images as $idx => $overlay) {
            $stream_idx = $slide_count + $idx;
            $start_time = number_format($overlay->time, 2);
            $end_time = number_format($overlay->time + $overlay->duration, 2);
            $next_label = "overlay{$idx}";
            $filters[] = "[{$current_label}][{$stream_idx}:v]overlay=enable=between(t\,{$start_time}\,{$end_time})[{$next_label}]";
            $current_label = $next_label;
        }

        $video_idx = $slide_count + $overlay_images->count();
        $v_start = number_format($video_element->time, 2);
        $v_end = number_format($video_element->time + $video_element->duration, 2);
        $filters[] = "[{$current_label}][{$video_idx}:v]overlay=enable=between(t\,{$v_start}\,{$v_end})[v_out]";

        $audio_labels = [];
        $first_audio = $video_idx + 1;
        foreach ($audio_tracks as $idx => $audio) {
            $stream_idx = $first_audio + $idx;
            $dur = number_format($audio->duration, 2);
            $start_time = number_format($audio->time, 2);

            $chain = "[{$stream_idx}:a]atrim=duration={$dur},asetpts=PTS-STARTPTS";
            if ($audio->time > 0) {
                $delay_ms = (int) round($audio->time * 1000);
                $chain .= ",adelay={$delay_ms}|{$delay_ms}";
            }

            $label = "a{$idx}";
            $filters[] = "{$chain}[{$label}]";
            $audio_labels[] = $label;
        }

        $mix_input = '';
        foreach ($audio_labels as $lbl) {
            $mix_input .= "[{$lbl}]";
        }
        $audio_count = count($audio_labels);
        $filters[] = "{$mix_input}amix=inputs={$audio_count}:duration=longest[a_out]";

        $filter_complex = implode(';', $filters);

        // Prepare output
        $filename = Str::random(12).'.mp4';
        $output_path = sys_get_temp_dir().DIRECTORY_SEPARATOR.$filename;

        // FFmpeg command, including render settings
        $video_bitrate = $settings['video_bitrate'];
        $audio_bitrate = $settings['audio_bitrate'];
        $fps = $settings['fps'];

        $command = 'ffmpeg '.implode(' ', $input_args)
            ." -r {$fps}"
            ." -filter_complex \"{$filter_complex}\""
            .' -map "[v_out]" -map "[a_out]"'
            ." -c:v libx264 -b:v {$video_bitrate}"
            ." -c:a aac -b:a {$audio_bitrate}"
            ." -shortest \"{$output_path}\" -y";

        $process = Process::fromShellCommandline($command, null, null, null, 300);
        $process->run();

        if (! $process->isSuccessful()) {
            return (object) [
                'success' => false,
                'exception' => new \RuntimeException('FFmpeg failed: '.$process->getErrorOutput()),
            ];
            throw new \RuntimeException('FFmpeg failed: '.$process->getErrorOutput());
        }

        return (object) [
            'success' => true,
            'name' => $filename,
            'path' => $output_path,
        ];
    }

    /**
     * Fetch video elements for rendering.
     */
    private static function get_video_elements(Video $video): Collection
    {
        return $video->video_elements;
    }

    /**
     * Extract render settings or defaults.
     */
    private static function get_render_settings(Video $video): array
    {
        return [
            'video_bitrate' => $video->render_settings?->video_bitrate ?? '3M',
            'audio_bitrate' => $video->render_settings?->audio_bitrate ?? '128k',
            'fps' => $video->render_settings?->fps ?? '30',
        ];
    }
}