import fs from 'fs';
import path from 'path';
import { modalClient } from './modal-client';
import { nebiusClient } from './nebius-client';
import { FileProcessor } from './file-upload';
import { storage } from './storage';
import { type Document, type InsertDocument } from '@shared/schema';

export interface ProcessingResult {
  success: boolean;
  extractedText?: string;
  embeddings?: number[];
  modalTaskId?: string;
  error?: string;
  processingTime: number;
}

export interface BatchProcessingResult {
  success: boolean;
  processedCount: number;
  failedCount: number;
  results: Array<{
    documentId: number;
    success: boolean;
    extractedText?: string;
    embeddings?: number[];
    error?: string;
  }>;
  totalProcessingTime: number;
}

export class DocumentProcessor {
  private static instance: DocumentProcessor;

  static getInstance(): DocumentProcessor {
    if (!DocumentProcessor.instance) {
      DocumentProcessor.instance = new DocumentProcessor();
    }
    return DocumentProcessor.instance;
  }

  /**
   * Process a single document using Modal for heavy workloads
   */
  async processDocument(
    document: Document,
    operations: Array<'extract_text' | 'generate_embedding' | 'build_index'> = ['extract_text']
  ): Promise<ProcessingResult> {
    const startTime = Date.now();
    
    try {
      let extractedText = document.content;
      let embeddings: number[] | undefined;
      let modalTaskId: string | undefined;

      // Step 1: Extract text if needed (for PDFs and images)
      if (operations.includes('extract_text') && document.filePath) {
        const textResult = await this.extractText(document);
        if (textResult.success) {
          extractedText = textResult.extractedText || document.content;
          modalTaskId = textResult.modalTaskId;
        } else {
          console.warn(`Text extraction failed for document ${document.id}: ${textResult.error}`);
        }
      }

      // Step 2: Generate embeddings if requested
      if (operations.includes('generate_embedding') && extractedText) {
        const embeddingResult = await this.generateEmbeddings(extractedText);
        if (embeddingResult.success) {
          embeddings = embeddingResult.embeddings;
        } else {
          console.warn(`Embedding generation failed for document ${document.id}: ${embeddingResult.error}`);
        }
      }

      const processingTime = Date.now() - startTime;

      return {
        success: true,
        extractedText,
        embeddings,
        modalTaskId,
        processingTime
      };

    } catch (error) {
      const processingTime = Date.now() - startTime;
      return {
        success: false,
        error: error instanceof Error ? error.message : String(error),
        processingTime
      };
    }
  }

  /**
   * Process multiple documents in batch using Modal's distributed computing
   */
  async batchProcessDocuments(
    documents: Document[],
    operations: Array<'extract_text' | 'generate_embedding' | 'build_index'> = ['extract_text']
  ): Promise<BatchProcessingResult> {
    const startTime = Date.now();
    const results: BatchProcessingResult['results'] = [];
    
    try {
      // Separate documents by processing requirements
      const documentsForModal = documents.filter(doc => 
        doc.filePath && FileProcessor.requiresOCR(doc.mimeType || '')
      );
      
      const documentsForLocal = documents.filter(doc => 
        !doc.filePath || !FileProcessor.requiresOCR(doc.mimeType || '')
      );

      // Process Modal-required documents in batch
      if (documentsForModal.length > 0 && operations.includes('extract_text')) {
        try {
          const modalResults = await this.batchExtractTextModal(documentsForModal);
          results.push(...modalResults);
        } catch (error) {
          console.error('Modal batch processing failed:', error);
          // Fall back to individual processing
          for (const doc of documentsForModal) {
            const result = await this.processDocument(doc, operations);
            results.push({
              documentId: doc.id,
              success: result.success,
              extractedText: result.extractedText,
              embeddings: result.embeddings,
              error: result.error
            });
          }
        }
      }

      // Process local documents
      for (const doc of documentsForLocal) {
        const result = await this.processDocument(doc, operations);
        results.push({
          documentId: doc.id,
          success: result.success,
          extractedText: result.extractedText,
          embeddings: result.embeddings,
          error: result.error
        });
      }

      const totalProcessingTime = Date.now() - startTime;
      const successCount = results.filter(r => r.success).length;
      const failedCount = results.length - successCount;

      return {
        success: true,
        processedCount: successCount,
        failedCount,
        results,
        totalProcessingTime
      };

    } catch (error) {
      const totalProcessingTime = Date.now() - startTime;
      return {
        success: false,
        processedCount: 0,
        failedCount: documents.length,
        results: documents.map(doc => ({
          documentId: doc.id,
          success: false,
          error: error instanceof Error ? error.message : String(error)
        })),
        totalProcessingTime
      };
    }
  }

  /**
   * Extract text from a document using Modal for PDFs/images or direct reading for text files
   */
  private async extractText(document: Document): Promise<{
    success: boolean;
    extractedText?: string;
    modalTaskId?: string;
    error?: string;
  }> {
    if (!document.filePath) {
      return { success: true, extractedText: document.content };
    }

    const mimeType = document.mimeType || '';

    try {
      // For text files, read directly
      if (FileProcessor.isTextFile(mimeType)) {
        const content = await FileProcessor.readTextFile(document.filePath);
        return { success: true, extractedText: content };
      }

      // For PDFs and images, use Modal
      if (FileProcessor.requiresOCR(mimeType)) {
        return await this.extractTextModal(document);
      }

      // Fallback: return existing content
      return { success: true, extractedText: document.content };

    } catch (error) {
      return {
        success: false,
        error: error instanceof Error ? error.message : String(error)
      };
    }
  }

  /**
   * Extract text using Modal for OCR-required files
   */
  private async extractTextModal(document: Document): Promise<{
    success: boolean;
    extractedText?: string;
    modalTaskId?: string;
    error?: string;
  }> {
    try {
      if (!document.filePath) {
        throw new Error('No file path provided for Modal processing');
      }

      // Read file and convert to base64
      const fileBuffer = await fs.promises.readFile(document.filePath);
      const base64Content = fileBuffer.toString('base64');

      // Prepare document for Modal
      const modalDocument = {
        id: document.id.toString(),
        content: base64Content,
        contentType: document.mimeType || 'application/octet-stream'
      };

      // Call Modal extract-text endpoint
      const result = await modalClient.extractTextFromDocuments([modalDocument]);
      
      if (result.status === 'completed' && result.results?.length > 0) {
        const extractionResult = result.results[0];
        if (extractionResult.status === 'completed') {
          return {
            success: true,
            extractedText: extractionResult.extracted_text,
            modalTaskId: result.task_id
          };
        } else {
          return {
            success: false,
            error: extractionResult.error || 'Modal extraction failed'
          };
        }
      } else {
        return {
          success: false,
          error: result.error || 'Modal processing failed'
        };
      }

    } catch (error) {
      console.error('Modal text extraction failed:', error);
      return {
        success: false,
        error: error instanceof Error ? error.message : String(error)
      };
    }
  }

  /**
   * Batch extract text using Modal
   */
  private async batchExtractTextModal(documents: Document[]): Promise<Array<{
    documentId: number;
    success: boolean;
    extractedText?: string;
    error?: string;
  }>> {
    const modalDocuments = await Promise.all(
      documents.map(async (doc) => {
        if (!doc.filePath) return null;
        
        try {
          const fileBuffer = await fs.promises.readFile(doc.filePath);
          return {
            id: doc.id.toString(),
            content: fileBuffer.toString('base64'),
            contentType: doc.mimeType || 'application/octet-stream'
          };
        } catch (error) {
          console.error(`Failed to read file for document ${doc.id}:`, error);
          return null;
        }
      })
    );

    const validDocuments = modalDocuments.filter(doc => doc !== null) as any[];
    
    if (validDocuments.length === 0) {
      return documents.map(doc => ({
        documentId: doc.id,
        success: false,
        error: 'No valid documents for processing'
      }));
    }

    try {
      const batchResult = await modalClient.batchProcessDocuments({
        documents: validDocuments,
        modelName: 'text-embedding-3-small',
        batchSize: Math.min(validDocuments.length, 10)
      });

      if (batchResult.status === 'completed' && batchResult.extraction_results) {
        return batchResult.extraction_results.map((result: any) => ({
          documentId: parseInt(result.id),
          success: result.status === 'completed',
          extractedText: result.extracted_text,
          error: result.error
        }));
      } else {
        throw new Error(batchResult.error || 'Batch processing failed');
      }

    } catch (error) {
      console.error('Modal batch processing failed:', error);
      return documents.map(doc => ({
        documentId: doc.id,
        success: false,
        error: error instanceof Error ? error.message : String(error)
      }));
    }
  }

  /**
   * Generate embeddings using Nebius AI
   */
  private async generateEmbeddings(text: string): Promise<{
    success: boolean;
    embeddings?: number[];
    error?: string;
  }> {
    try {
      // Truncate text if too long (most embedding models have token limits)
      const maxLength = 8000; // Conservative limit
      const truncatedText = text.length > maxLength ? text.substring(0, maxLength) : text;
      
      const result = await nebiusClient.generateEmbeddings(truncatedText);
      
      if (result.success && result.embeddings) {
        return {
          success: true,
          embeddings: result.embeddings
        };
      } else {
        return {
          success: false,
          error: result.error || 'Embedding generation failed'
        };
      }

    } catch (error) {
      return {
        success: false,
        error: error instanceof Error ? error.message : String(error)
      };
    }
  }

  /**
   * Build vector index using Modal
   */
  async buildVectorIndex(
    documents: Document[],
    indexName = 'research_papers_clean_v2'
  ): Promise<{
    success: boolean;
    indexName?: string;
    documentCount?: number;
    error?: string;
  }> {
    try {
      const modalDocuments = documents.map(doc => ({
        id: doc.id.toString(),
        content: doc.content,
        title: doc.title,
        source: doc.source
      }));

      const result = await modalClient.buildVectorIndex(modalDocuments, {
        indexName,
        dimension: 1536, // Standard OpenAI embedding dimension
        indexType: 'IVF',
        nlist: Math.min(100, Math.max(10, Math.floor(documents.length / 10)))
      });

      if (result.status === 'completed') {
        return {
          success: true,
          indexName: result.index_name,
          documentCount: result.document_count
        };
      } else {
        return {
          success: false,
          error: result.error || 'Index building failed'
        };
      }

    } catch (error) {
      return {
        success: false,
        error: error instanceof Error ? error.message : String(error)
      };
    }
  }

  /**
   * Search vector index using Modal
   */
  async searchVectorIndex(
    query: string,
    indexName = 'research_papers_clean_v2',
    maxResults = 10
  ): Promise<{
    success: boolean;
    results?: Array<{
      id: string;
      title: string;
      content: string;
      source: string;
      relevanceScore: number;
      rank: number;
      snippet: string;
    }>;
    error?: string;
  }> {
    try {
      const result = await modalClient.vectorSearch(query, indexName, maxResults);
      if (result.status === 'completed') {
        // Enrich vector search results with complete document data from database
        const enrichedResults = await Promise.all(
          result.results.map(async (vectorResult: any) => {
            try {
              // Get complete document data from database using the ID
              const dbDocument = await storage.getDocument(parseInt(vectorResult.id));
              if (dbDocument) {
                // Merge vector search metadata with database document
                // Ensure the URL field is preserved from the database
                const enriched = {
                  id: dbDocument.id,
                  title: dbDocument.title,
                  content: dbDocument.content,
                  source: dbDocument.source,
                  sourceType: dbDocument.sourceType,
                  url: dbDocument.url, // Explicitly preserve URL
                  metadata: dbDocument.metadata,
                  createdAt: dbDocument.createdAt,
                  // Add vector search specific fields
                  relevanceScore: vectorResult.relevanceScore,
                  rank: vectorResult.rank,
                  snippet: vectorResult.snippet || dbDocument.content.substring(0, 200) + '...'
                };
                return enriched;
              } else {
                // Fallback to vector result if database document not found
                return vectorResult;
              }
            } catch (error) {
              console.warn(`Failed to enrich vector result for ID ${vectorResult.id}:`, error);
              return vectorResult;
            }
          })
        );

        return {
          success: true,
          results: enrichedResults
        };
      } else {
        return {
          success: false,
          error: result.error || 'Vector search failed'
        };
      }

    } catch (error) {
      return {
        success: false,
        error: error instanceof Error ? error.message : String(error)
      };
    }
  }
}

export const documentProcessor = DocumentProcessor.getInstance();