<?php

namespace App\Services;

use App\Models\Video;
use App\Models\VideoAudioTrack;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\Log;

class VideoMergeService
{
    public function __construct(private NasSyncService $nas) {}

    /**
     * Preview counts for merging $source into $target. Read-only.
     */
    public function preview(Video $source, Video $target): array
    {
        $tracks    = DB::table('video_audio_tracks')->where('video_id', $source->id)->count();
        $slides    = DB::table('video_slides')->where('video_id', $source->id)->count();
        $comments  = DB::table('comments')->where('video_id', $source->id)->count();
        $views     = DB::table('video_views')->where('video_id', $source->id)->count();
        $downloads = DB::table('video_downloads')->where('video_id', $source->id)->count();
        $shares    = DB::table('video_shares')->where('video_id', $source->id)->count();

        $srcLikeUsers = DB::table('video_likes')->where('video_id', $source->id)->pluck('user_id');
        $tgtLikeUsers = DB::table('video_likes')->where('video_id', $target->id)->pluck('user_id')->flip();
        $newLikes     = $srcLikeUsers->reject(fn ($uid) => $tgtLikeUsers->has($uid))->count();

        $srcPlaylists = DB::table('playlist_videos')->where('video_id', $source->id)->pluck('playlist_id');
        $tgtPlaylists = DB::table('playlist_videos')->where('video_id', $target->id)->pluck('playlist_id')->flip();
        $plMerged     = $srcPlaylists->reject(fn ($pid) => $tgtPlaylists->has($pid))->count();

        return [
            'tracks'             => $tracks + 1, // +1 = source's primary becomes a new track on target
            'slides'             => $slides,
            'comments'           => $comments,
            'views'              => $views,
            'downloads'          => $downloads,
            'shares'             => $shares,
            'likes_source'       => $srcLikeUsers->count(),
            'likes_after_dedupe' => $newLikes,
            'playlists_merged'   => $plMerged,
        ];
    }

    /**
     * Merge $source video into $target. Both must be music-type.
     *
     * Simplified model: everything under sourceDir moves to targetDir, filename
     * prefixes are rewritten in one pass, and the user rearranges tracks/slides
     * in the edit UI afterwards. No special "primary vs extra" bookkeeping.
     */
    public function merge(Video $source, Video $target): void
    {
        if ($source->id === $target->id) {
            throw new \InvalidArgumentException('Cannot merge a video with itself.');
        }
        if ($source->type !== 'music' || $target->type !== 'music') {
            throw new \InvalidArgumentException('Only music-type videos can be merged.');
        }
        if (!$this->nas->isEnabled()) {
            throw new \RuntimeException(
                'NAS is currently unreachable — merge is disabled until it comes back online.'
            );
        }

        $source->loadMissing(['audioTracks']);

        $sourceDir = $this->nas->resolveVideoDir($source);
        $targetDir = $this->nas->resolveVideoDir($target);

        if ($sourceDir === $targetDir) {
            throw new \RuntimeException('Source and target resolve to the same folder — refusing to merge.');
        }

        Log::info('Merge: begin', [
            'source_id'  => $source->id,
            'target_id'  => $target->id,
            'source_dir' => $sourceDir,
            'target_dir' => $targetDir,
        ]);

        // Ensure target has a tracks/ subfolder on both NAS and local
        $this->nas->mkdirp("{$targetDir}/tracks");
        @mkdir(storage_path("app/{$targetDir}/tracks"), 0755, true);

        DB::transaction(function () use ($source, $target, $sourceDir, $targetDir) {

            // ── 1. Promote source's primary audio to a new track on target ─
            $srcPrimaryExt      = pathinfo($source->filename ?: 'audio.mp3', PATHINFO_EXTENSION) ?: 'mp3';
            $srcPrimaryFilename = "audio.{$srcPrimaryExt}";
            $srcPrimaryOldFolder = "{$sourceDir}/tracks/" . $this->nas->trackFolderName($source, null);

            $newPrimaryTrack = VideoAudioTrack::create([
                'video_id'    => $target->id,
                'language'    => $source->language ?: 'xx',
                'label'       => $source->title ?: null,
                'title'       => $source->title ?: null,
                'description' => $source->description,
                'filename'    => $srcPrimaryFilename,
                'path'        => '',
            ]);
            if (!$newPrimaryTrack || !$newPrimaryTrack->id) {
                throw new \RuntimeException('Failed to create promoted primary track record.');
            }

            $newPrimaryFolder = "{$targetDir}/tracks/" . $this->nas->trackFolderName($target, $newPrimaryTrack);
            $this->moveFolder($srcPrimaryOldFolder, $newPrimaryFolder);
            $newPrimaryTrack->update(['path' => "{$newPrimaryFolder}/{$srcPrimaryFilename}"]);

            // ── 2. Move each source extra track's folder into target/tracks/
            //     The folder basename ({lang}-{track_id}) is globally unique because
            //     track ids are globally unique — no collisions with target's own tracks.
            foreach ($source->audioTracks as $track) {
                $basename  = $this->nas->trackFolderName($source, $track);
                $oldFolder = "{$sourceDir}/tracks/{$basename}";
                $newFolder = "{$targetDir}/tracks/{$basename}";
                $this->moveFolder($oldFolder, $newFolder);

                $newTrackPath = $track->path && str_starts_with($track->path, $oldFolder . '/')
                    ? $newFolder . '/' . substr($track->path, strlen($oldFolder) + 1)
                    : $track->path;

                $track->video_id = $target->id;
                $track->path     = $newTrackPath;
                $track->save();
            }

            // ── 3. Move ALL slides for the source video ────────────────────
            //     One pass: re-parent every source slide, rewrite any filename
            //     that started with sourceDir/... to targetDir/..., and if the
            //     slide had NULL audio_track_id (belonged to source's primary),
            //     point it at the newly-created primary track.
            $sourcePrefix = $sourceDir . '/';
            $targetPrefix = $targetDir . '/';
            $slides = DB::table('video_slides')->where('video_id', $source->id)->get();
            foreach ($slides as $s) {
                $newFilename = $s->filename;
                if (is_string($s->filename) && str_starts_with($s->filename, $sourcePrefix)) {
                    $newFilename = $targetPrefix . substr($s->filename, strlen($sourcePrefix));
                }
                $updates = [
                    'video_id' => $target->id,
                    'filename' => $newFilename,
                ];
                if ($s->audio_track_id === null) {
                    $updates['audio_track_id'] = $newPrimaryTrack->id;
                }
                DB::table('video_slides')->where('id', $s->id)->update($updates);
            }

            // ── 4. Re-parent comments / views / downloads / shares ─────────
            DB::table('comments')->where('video_id', $source->id)->update(['video_id' => $target->id]);
            DB::table('video_views')->where('video_id', $source->id)->update(['video_id' => $target->id]);
            DB::table('video_downloads')->where('video_id', $source->id)->update(['video_id' => $target->id]);
            DB::table('video_shares')->where('video_id', $source->id)->update(['video_id' => $target->id]);

            // ── 5. Likes — dedupe by user_id ────────────────────────────────
            $existingLikeUsers = DB::table('video_likes')->where('video_id', $target->id)->pluck('user_id')->all();
            if (!empty($existingLikeUsers)) {
                DB::table('video_likes')
                    ->where('video_id', $source->id)
                    ->whereIn('user_id', $existingLikeUsers)
                    ->delete();
            }
            DB::table('video_likes')->where('video_id', $source->id)->update(['video_id' => $target->id]);

            // ── 6. Playlist pivots — dedupe by playlist_id ─────────────────
            $existingPlaylists = DB::table('playlist_videos')->where('video_id', $target->id)->pluck('playlist_id')->all();
            if (!empty($existingPlaylists)) {
                DB::table('playlist_videos')
                    ->where('video_id', $source->id)
                    ->whereIn('playlist_id', $existingPlaylists)
                    ->delete();
            }
            DB::table('playlist_videos')->where('video_id', $source->id)->update(['video_id' => $target->id]);

            // ── 7. Counters ────────────────────────────────────────────────
            DB::table('videos')->where('id', $target->id)->update([
                'download_count' => DB::raw('COALESCE(download_count,0) + ' . (int) $source->download_count),
                'share_count'    => DB::raw('COALESCE(share_count,0) + ' . (int) $source->share_count),
            ]);

            // ── 8. Redirect row (remember source folder for later repair) ──
            DB::table('video_redirects')->insert([
                'source_id'     => $source->id,
                'target_id'     => $target->id,
                'source_folder' => $sourceDir,
                'created_at'    => now(),
            ]);

            // ── 9. Delete source video row ─────────────────────────────────
            DB::table('videos')->where('id', $source->id)->delete();
        });

        // ── 10. Best-effort cleanup of the emptied source folder ───────────
        $this->pruneEmptyFolder("{$sourceDir}/tracks");
        $this->pruneEmptyFolder($sourceDir);

        Log::info('Merge: complete', ['source_id' => $source->id, 'target_id' => $target->id]);
    }

    /**
     * Move a folder on both NAS and local disk. Logs the outcome.
     */
    private function moveFolder(string $oldRel, string $newRel): void
    {
        if ($oldRel === $newRel) return;

        $nasMoved = false;
        if ($this->nas->isEnabled()) {
            $this->nas->renameNasPath($oldRel, $newRel);
            $nasMoved = true;
        }

        $oldLocal = storage_path('app/' . $oldRel);
        $newLocal = storage_path('app/' . $newRel);
        $localMoved = false;
        if (is_dir($oldLocal)) {
            @mkdir(dirname($newLocal), 0755, true);
            $localMoved = @rename($oldLocal, $newLocal);
        }
        Log::info('Merge: moveFolder', [
            'old' => $oldRel, 'new' => $newRel,
            'nas' => $nasMoved, 'local' => $localMoved,
        ]);
    }

    private function pruneEmptyFolder(string $rel): void
    {
        if ($this->nas->isEnabled()) {
            $this->nas->deleteFile("{$rel}/meta.json");
            $this->nas->deleteFolder($rel);
        }
        $local = storage_path('app/' . $rel);
        if (is_dir($local)) {
            @unlink($local . '/meta.json');
            @rmdir($local);
        }
    }
}