import express from 'express';
import { Playlist } from '../models/Playlist.js';
import { Request, Response } from 'express';

const router = express.Router();

// Get all playlists
router.get('/', async (req: Request, res: Response) => {
  try {
    const playlists = await Playlist.find({});
    res.json(playlists);
  } catch (error) {
    console.error('Error fetching playlists:', error);
    res.status(500).json({ message: 'Error fetching playlists', error });
  }
});

// Get playlist structure only (without track data) for faster loading
router.get('/structure', async (req: Request, res: Response) => {
  try {
    const playlists = await Playlist.find({});
    
    // Keep track counts but remove full track data to reduce payload size
    const structureOnly = playlists.map(playlist => {
      const cleanPlaylist = playlist.toObject() as any;
      
      // Replace tracks array with track count for the main playlist
      if (cleanPlaylist.tracks) {
        cleanPlaylist.trackCount = cleanPlaylist.tracks.length;
        delete cleanPlaylist.tracks;
      } else {
        cleanPlaylist.trackCount = 0;
      }
      
      // Recursively process children
      const cleanChildren = (children: any[]): any[] => {
        return children.map(child => {
          const cleanChild = { ...child } as any;
          
          // Replace tracks array with track count
          if (cleanChild.tracks) {
            cleanChild.trackCount = cleanChild.tracks.length;
            delete cleanChild.tracks;
          } else {
            cleanChild.trackCount = 0;
          }
          
          if (cleanChild.children && cleanChild.children.length > 0) {
            cleanChild.children = cleanChildren(cleanChild.children);
          }
          return cleanChild;
        });
      };
      
      if (cleanPlaylist.children && cleanPlaylist.children.length > 0) {
        cleanPlaylist.children = cleanChildren(cleanPlaylist.children);
      }
      
      return cleanPlaylist;
    });
    
    res.json(structureOnly);
  } catch (error) {
    console.error('Error fetching playlist structure:', error);
    res.status(500).json({ message: 'Error fetching playlist structure', error });
  }
});

// Save playlists in batch (replacing all existing ones)
router.post('/batch', async (req, res) => {
  try {
    // Replace all playlists atomically
    await Playlist.deleteMany({});
    const payload = Array.isArray(req.body) ? req.body : [];
    const playlists = await Playlist.insertMany(payload, { ordered: false });
    res.json(playlists);
  } catch (error) {
    console.error('Error saving playlists:', error);
    res.status(500).json({ error: 'Failed to save playlists' });
  }
});

// Reorder tracks inside a playlist (by name). Stores order separately in `order` to avoid interfering with original `tracks`.
router.post('/reorder', async (req: Request, res: Response) => {
  try {
    const { playlistName, orderedIds } = req.body as { playlistName: string; orderedIds: string[] };
    if (!playlistName || !Array.isArray(orderedIds)) {
      return res.status(400).json({ message: 'playlistName and orderedIds are required' });
    }

    const playlists = await Playlist.find({});

    let updated = false;
    const reorderNode = (node: any): any => {
      if (!node) return node;
      if (node.type === 'playlist' && node.name === playlistName) {
        // Store order separately; do not mutate tracks
        const unique = Array.from(new Set(orderedIds));
        node.order = unique;
        updated = true;
        return node;
      }
      if (Array.isArray(node.children)) {
        node.children = node.children.map(reorderNode);
      }
      return node;
    };

    for (const p of playlists) {
      reorderNode(p as any);
      // Force Mongoose to see deep changes under Mixed children
      p.markModified('children');
      p.markModified('tracks');
      await p.save();
    }

    if (!updated) {
      return res.status(404).json({ message: `Playlist "${playlistName}" not found` });
    }

    res.json({ message: 'Playlist order updated', playlistName, newLength: orderedIds.length });
  } catch (error) {
    console.error('Error reordering playlist:', error);
    res.status(500).json({ error: 'Failed to reorder playlist' });
  }
});

// Move a single track before another (stable, full-playlist context)
router.post('/reorder-move', async (req: Request, res: Response) => {
  try {
    const { playlistName, fromId, toId } = req.body as { playlistName: string; fromId: string; toId?: string };
    if (!playlistName || !fromId) {
      return res.status(400).json({ message: 'playlistName and fromId are required' });
    }

    const playlists = await Playlist.find({});
    let updated = false;

    const applyMove = (node: any): any => {
      if (!node) return node;
      if (node.type === 'playlist' && node.name === playlistName) {
        const base: string[] = Array.isArray(node.tracks) ? node.tracks : [];
        const order: string[] = Array.isArray(node.order) ? node.order : [];
        // Build effective order
        const baseSet = new Set(base);
        const effective = [
          ...order.filter((id: string) => baseSet.has(id)),
          ...base.filter((id: string) => !order.includes(id))
        ];

        // Remove fromId if present
        const without = effective.filter(id => id !== fromId);
        let insertIndex = typeof toId === 'string' ? without.indexOf(toId) : without.length;
        if (insertIndex < 0) insertIndex = without.length;
        without.splice(insertIndex, 0, fromId);

        console.log('[REORDER_MOVE] playlist:', playlistName, 'from:', fromId, 'to:', toId, 'baseLen:', base.length, 'orderLenBefore:', order.length, 'orderLenAfter:', without.length);
        console.log('[REORDER_MOVE] sample order:', without.slice(0, 5));
        node.order = without; // store full order overlay
        updated = true;
        return node;
      }
      if (Array.isArray(node.children)) {
        node.children = node.children.map(applyMove);
      }
      return node;
    };

    for (const p of playlists) {
      applyMove(p as any);
      p.markModified('children');
      p.markModified('order');
      await p.save();
    }

    if (!updated) {
      return res.status(404).json({ message: `Playlist "${playlistName}" not found` });
    }

    res.json({ message: 'Track moved', playlistName });
  } catch (error) {
    console.error('Error moving track in playlist:', error);
    res.status(500).json({ error: 'Failed to move track' });
  }
});

// Move multiple tracks before another (en bloc, preserves relative order)
router.post('/reorder-move-many', async (req: Request, res: Response) => {
  try {
    const { playlistName, fromIds, toId } = req.body as { playlistName: string; fromIds: string[]; toId?: string };
    if (!playlistName || !Array.isArray(fromIds) || fromIds.length === 0) {
      return res.status(400).json({ message: 'playlistName and fromIds are required' });
    }

    const playlists = await Playlist.find({});
    let updated = false;

    const applyMoveMany = (node: any): any => {
      if (!node) return node;
      if (node.type === 'playlist' && node.name === playlistName) {
        const base: string[] = Array.isArray(node.tracks) ? node.tracks : [];
        const order: string[] = Array.isArray(node.order) ? node.order : [];
        const baseSet = new Set(base);
        const effective: string[] = [
          ...order.filter((id: string) => baseSet.has(id)),
          ...base.filter((id: string) => !order.includes(id))
        ];

        const moveSet = new Set(fromIds);
        const movingOrdered = effective.filter(id => moveSet.has(id));
        if (movingOrdered.length === 0) {
          return node;
        }

        // Remove all moving ids
        const without = effective.filter(id => !moveSet.has(id));
        let insertIndex = typeof toId === 'string' ? without.indexOf(toId) : without.length;
        if (insertIndex < 0) insertIndex = without.length;
        // Insert block preserving relative order
        without.splice(insertIndex, 0, ...movingOrdered);

        console.log('[REORDER_MOVE_MANY] playlist:', playlistName, 'count:', movingOrdered.length, 'to:', toId, 'baseLen:', base.length, 'orderLenBefore:', order.length, 'orderLenAfter:', without.length);
        console.log('[REORDER_MOVE_MANY] sample order:', without.slice(0, 7));
        node.order = without;
        updated = true;
        return node;
      }
      if (Array.isArray(node.children)) {
        node.children = node.children.map(applyMoveMany);
      }
      return node;
    };

    for (const p of playlists) {
      applyMoveMany(p as any);
      p.markModified('children');
      p.markModified('order');
      await p.save();
    }

    if (!updated) {
      return res.status(404).json({ message: `Playlist "${playlistName}" not found` });
    }

    res.json({ message: 'Tracks moved', playlistName });
  } catch (error) {
    console.error('Error moving tracks in playlist:', error);
    res.status(500).json({ message: 'Error moving tracks in playlist', error });
  }
});

export const playlistsRouter = router;