const multer = require('multer');
const path = require('path');
const fs = require('fs');
const pdf = require('pdf-parse');
const { Document, sequelize } = require('../models');
const { Op } = require('sequelize');
const logger = require('../utils/logger');
const embeddingService = require('../services/embeddingService');
const graphRagService = require('../services/graphRagService');

// Configure multer for file uploads
const storage = multer.diskStorage({
  destination: (req, file, cb) => {
    const uploadPath = path.join(__dirname, '../../uploads');
    if (!fs.existsSync(uploadPath)) {
      fs.mkdirSync(uploadPath, { recursive: true });
    }
    cb(null, uploadPath);
  },
  filename: (req, file, cb) => {
    const uniqueSuffix = Date.now() + '-' + Math.round(Math.random() * 1E9);
    cb(null, file.fieldname + '-' + uniqueSuffix + path.extname(file.originalname));
  }
});

const upload = multer({
  storage: storage,
  limits: {
    fileSize: 10 * 1024 * 1024, // 10MB for testing
    fieldSize: 10 * 1024 * 1024, // 10MB for field values
    fieldNameSize: 100, // 100 bytes for field names
    files: 1 // Only 1 file at a time
  },
  fileFilter: (req, file, cb) => {
    const allowedTypes = ['.pdf', '.txt', '.doc', '.docx'];
    const ext = path.extname(file.originalname).toLowerCase();
    
    if (allowedTypes.includes(ext)) {
      cb(null, true);
    } else {
      cb(new Error('Invalid file type. Only PDF, TXT, DOC, DOCX files are allowed.'));
    }
  }
});

const uploadDocument = async (req, res) => {
  try {
    if (!req.file) {
      return res.status(400).json({
        success: false,
        error: 'No file uploaded'
      });
    }

    const { category, tags } = req.body;
    let extractedText = '';

    // Extract text from PDF
    if (req.file.mimetype === 'application/pdf') {
      try {
        const dataBuffer = fs.readFileSync(req.file.path);
        const pdfData = await pdf(dataBuffer);
        extractedText = pdfData.text;
      } catch (error) {
        logger.error('PDF extraction error:', error);
        extractedText = 'Error extracting text from PDF';
      }
    } else if (req.file.mimetype === 'text/plain') {
      extractedText = fs.readFileSync(req.file.path, 'utf8');
    }

    // Create document record
    const document = await Document.create({
      filename: req.file.filename,
      original_filename: req.file.originalname,
      file_path: req.file.path,
      file_type: req.file.mimetype,
      file_size: req.file.size,
      content: extractedText,
      extracted_text: extractedText,
      category: category || 'general',
      tags: tags ? tags.split(',').map(tag => tag.trim()) : [],
      indexing_status: 'processing'
    });

    // Generate and store embeddings (if text available)
    if (extractedText && extractedText.trim().length > 0) {
      try {
        const embedding = await embeddingService.embedText(extractedText.slice(0, 15000));
        await document.update({ embeddings: embedding, is_indexed: true, indexing_status: 'completed' });
      } catch (e) {
        logger.error('Embedding generation failed:', e);
        await document.update({ is_indexed: false, indexing_status: 'failed' });
      }
    } else {
      await document.update({ is_indexed: false, indexing_status: 'failed' });
    }

    logger.info(`Document uploaded: ${document.id}`);

    res.status(201).json({
      success: true,
      data: { document }
    });
  } catch (error) {
    logger.error('Upload document error:', error);
    
    // Clean up uploaded file if document creation failed
    if (req.file && fs.existsSync(req.file.path)) {
      fs.unlinkSync(req.file.path);
    }
    
    res.status(500).json({
      success: false,
      error: 'Internal server error'
    });
  }
};

const getDocuments = async (req, res) => {
  try {
    const { page = 1, limit = 10, category, search, isIndexed } = req.query;

    const whereClause = {};
    if (category) whereClause.category = category;
    if (isIndexed !== undefined) whereClause.is_indexed = isIndexed === 'true';
    if (search) {
      whereClause[Op.or] = [
        { original_filename: { [Op.iLike]: `%${search}%` } },
        { extracted_text: { [Op.iLike]: `%${search}%` } }
      ];
    }

    const documents = await Document.findAndCountAll({
      where: whereClause,
      order: [['created_at', 'DESC']],
      limit: parseInt(limit),
      offset: (parseInt(page) - 1) * parseInt(limit)
    });

    res.json({
      success: true,
      data: {
        documents: documents.rows,
        pagination: {
          page: parseInt(page),
          limit: parseInt(limit),
          total: documents.count,
          pages: Math.ceil(documents.count / parseInt(limit))
        }
      }
    });
  } catch (error) {
    logger.error('Get documents error:', error);
    res.status(500).json({
      success: false,
      error: 'Internal server error'
    });
  }
};

const getDocument = async (req, res) => {
  try {
    const { documentId } = req.params;

    const document = await Document.findByPk(documentId);

    if (!document) {
      return res.status(404).json({
        success: false,
        error: 'Document not found'
      });
    }

    res.json({
      success: true,
      data: { document }
    });
  } catch (error) {
    logger.error('Get document error:', error);
    res.status(500).json({
      success: false,
      error: 'Internal server error'
    });
  }
};

const searchDocuments = async (req, res) => {
  try {
    const { query, category, limit = 10 } = req.query;

    if (!query) {
      return res.status(400).json({
        success: false,
        error: 'Search query is required'
      });
    }

    const whereClause = {
      is_indexed: true,
      ...(category ? { category } : {})
    };

    // Embed query and compute cosine similarity in JS for now
    const queryEmbedding = await embeddingService.embedText(query);

    const candidates = await Document.findAll({
      where: whereClause,
      attributes: ['id', 'original_filename', 'extracted_text', 'embeddings', 'category', 'created_at']
    });

    const scored = [];
    for (const doc of candidates) {
      const emb = doc.embeddings || [];
      const score = embeddingService.cosineSimilarity(queryEmbedding, emb);
      scored.push({
        id: doc.id,
        original_filename: doc.original_filename,
        snippet: (doc.extracted_text || '').slice(0, 300),
        category: doc.category,
        created_at: doc.created_at,
        score
      });
    }

    scored.sort((a, b) => b.score - a.score);
    const top = scored.slice(0, parseInt(limit));

    res.json({ success: true, data: { results: top } });
  } catch (error) {
    logger.error('Search documents error:', error);
    res.status(500).json({
      success: false,
      error: 'Internal server error'
    });
  }
};

const graphSearchDocuments = async (req, res) => {
  try {
    const { query, category } = req.query;

    if (!query) {
      return res.status(400).json({ success: false, error: 'Search query is required' });
    }

    const result = await graphRagService.graphSearch({ query, category });
    res.json({ success: true, data: result });
  } catch (error) {
    logger.error('Graph search error:', error);
    res.status(500).json({ success: false, error: 'Internal server error' });
  }
};

const deleteDocument = async (req, res) => {
  try {
    const { documentId } = req.params;

    const document = await Document.findByPk(documentId);

    if (!document) {
      return res.status(404).json({
        success: false,
        error: 'Document not found'
      });
    }

    // Delete physical file
    if (fs.existsSync(document.file_path)) {
      fs.unlinkSync(document.file_path);
    }

    // Delete database record
    await document.destroy();

    logger.info(`Document deleted: ${documentId}`);

    res.json({
      success: true,
      message: 'Document deleted successfully'
    });
  } catch (error) {
    logger.error('Delete document error:', error);
    res.status(500).json({
      success: false,
      error: 'Internal server error'
    });
  }
};

module.exports = {
  uploadDocument,
  getDocuments,
  getDocument,
  searchDocuments,
  graphSearchDocuments,
  deleteDocument,
  upload // Export multer middleware
};