import * as path from 'path';
import { promises as fs } from 'fs';
import * as plugins from '../../ts/plugins.js';

/**
 * Corpus loader for managing test invoice files
 */

export interface CorpusFile {
  path: string;
  format: string;
  category: string;
  size: number;
  valid: boolean;
}

export class CorpusLoader {
  private static basePath = path.join(process.cwd(), 'test/assets/corpus');
  private static cache = new Map<string, Buffer>();

  /**
   * Corpus categories with their paths
   */
  static readonly CATEGORIES = {
    CII_XMLRECHNUNG: 'XML-Rechnung/CII',
    UBL_XMLRECHNUNG: 'XML-Rechnung/UBL',
    ZUGFERD_V1_CORRECT: 'ZUGFeRDv1/correct',
    ZUGFERD_V1_FAIL: 'ZUGFeRDv1/fail',
    ZUGFERD_V2_CORRECT: 'ZUGFeRDv2/correct',
    ZUGFERD_V2_FAIL: 'ZUGFeRDv2/fail',
    PEPPOL: 'PEPPOL/Valid/Qvalia',
    FATTURAPA_OFFICIAL: 'fatturaPA/official',
    FATTURAPA_EIGOR: 'fatturaPA/eigor',
    EN16931_CII: 'eInvoicing-EN16931/cii/examples',
    EN16931_UBL_EXAMPLES: 'eInvoicing-EN16931/ubl/examples',
    EN16931_UBL_INVOICE: 'eInvoicing-EN16931/test/Invoice-unit-UBL',
    EN16931_UBL_CREDITNOTE: 'eInvoicing-EN16931/test/CreditNote-unit-UBL',
    EDIFACT_EXAMPLES: 'eInvoicing-EN16931/edifact/examples',
    OTHER: 'other',
    INCOMING: 'incoming',
    UNSTRUCTURED: 'unstructured'
  } as const;

  /**
   * Load a single corpus file
   */
  static async loadFile(filePath: string): Promise<Buffer> {
    const fullPath = path.join(this.basePath, filePath);
    
    // Check cache first
    if (this.cache.has(fullPath)) {
      return this.cache.get(fullPath)!;
    }

    try {
      const buffer = await fs.readFile(fullPath);
      
      // Cache files under 10MB
      if (buffer.length < 10 * 1024 * 1024) {
        this.cache.set(fullPath, buffer);
      }
      
      return buffer;
    } catch (error) {
      throw new Error(`Failed to load corpus file ${filePath}: ${error.message}`);
    }
  }

  /**
   * Load all files from a category
   */
  static async loadCategory(category: keyof typeof CorpusLoader.CATEGORIES): Promise<CorpusFile[]> {
    const categoryPath = this.CATEGORIES[category];
    const fullPath = path.join(this.basePath, categoryPath);
    
    try {
      const entries = await fs.readdir(fullPath, { withFileTypes: true });
      const files: CorpusFile[] = [];
      
      for (const entry of entries) {
        if (entry.isFile() && this.isInvoiceFile(entry.name)) {
          const filePath = path.join(categoryPath, entry.name);
          const stat = await fs.stat(path.join(this.basePath, filePath));
          
          files.push({
            path: filePath,
            format: this.detectFormatFromPath(filePath),
            category: category,
            size: stat.size,
            valid: !categoryPath.includes('fail')
          });
        }
      }
      
      return files;
    } catch (error) {
      console.warn(`Failed to load category ${category}: ${error.message}`);
      return [];
    }
  }

  /**
   * Load files matching a pattern
   */
  static async loadPattern(pattern: string, category?: keyof typeof CorpusLoader.CATEGORIES): Promise<CorpusFile[]> {
    const files: CorpusFile[] = [];
    const categoriesToSearch = category ? [category] : Object.keys(this.CATEGORIES) as Array<keyof typeof CorpusLoader.CATEGORIES>;
    
    for (const cat of categoriesToSearch) {
      const categoryFiles = await this.loadCategory(cat);
      const matchingFiles = categoryFiles.filter(file => 
        path.basename(file.path).match(pattern.replace('*', '.*'))
      );
      files.push(...matchingFiles);
    }
    
    return files;
  }

  /**
   * Get corpus statistics
   */
  static async getStatistics(): Promise<{
    totalFiles: number;
    totalSize: number;
    byFormat: Record<string, number>;
    byCategory: Record<string, number>;
    validFiles: number;
    invalidFiles: number;
  }> {
    const stats = {
      totalFiles: 0,
      totalSize: 0,
      byFormat: {} as Record<string, number>,
      byCategory: {} as Record<string, number>,
      validFiles: 0,
      invalidFiles: 0
    };

    for (const category of Object.keys(this.CATEGORIES) as Array<keyof typeof CorpusLoader.CATEGORIES>) {
      const files = await this.loadCategory(category);
      
      stats.totalFiles += files.length;
      stats.byCategory[category] = files.length;
      
      for (const file of files) {
        stats.totalSize += file.size;
        stats.byFormat[file.format] = (stats.byFormat[file.format] || 0) + 1;
        
        if (file.valid) {
          stats.validFiles++;
        } else {
          stats.invalidFiles++;
        }
      }
    }
    
    return stats;
  }

  /**
   * Clear the file cache
   */
  static clearCache(): void {
    this.cache.clear();
  }

  /**
   * Check if a file is an invoice file
   */
  private static isInvoiceFile(filename: string): boolean {
    const extensions = ['.xml', '.pdf', '.txt'];
    return extensions.some(ext => filename.toLowerCase().endsWith(ext));
  }

  /**
   * Detect format from file path
   */
  private static detectFormatFromPath(filePath: string): string {
    const filename = path.basename(filePath).toLowerCase();
    
    if (filename.includes('.cii.')) return 'CII';
    if (filename.includes('.ubl.')) return 'UBL';
    if (filename.includes('zugferd')) return 'ZUGFeRD';
    if (filename.includes('factur')) return 'Factur-X';
    if (filename.includes('xrechnung')) return 'XRechnung';
    if (filename.includes('fattura')) return 'FatturaPA';
    if (filename.includes('peppol')) return 'PEPPOL';
    if (filename.endsWith('.pdf')) return 'PDF';
    
    return 'Unknown';
  }

  /**
   * Get files from a category (alias for loadCategory for consistency)
   */
  static async getFiles(category: keyof typeof CorpusLoader.CATEGORIES): Promise<string[]> {
    const files = await this.loadCategory(category);
    return files.map(f => path.join(this.basePath, f.path));
  }

  /**
   * Create a test dataset from corpus files
   */
  static async createTestDataset(options: {
    formats?: string[];
    categories?: Array<keyof typeof CorpusLoader.CATEGORIES>;
    maxFiles?: number;
    validOnly?: boolean;
  } = {}): Promise<CorpusFile[]> {
    let files: CorpusFile[] = [];
    
    const categoriesToLoad = options.categories || Object.keys(this.CATEGORIES) as Array<keyof typeof CorpusLoader.CATEGORIES>;
    
    for (const category of categoriesToLoad) {
      const categoryFiles = await this.loadCategory(category);
      files.push(...categoryFiles);
    }
    
    // Filter by format if specified
    if (options.formats && options.formats.length > 0) {
      files = files.filter(f => options.formats!.includes(f.format));
    }
    
    // Filter by validity if specified
    if (options.validOnly) {
      files = files.filter(f => f.valid);
    }
    
    // Limit number of files if specified
    if (options.maxFiles && files.length > options.maxFiles) {
      // Shuffle and take first N files for variety
      files = files.sort(() => Math.random() - 0.5).slice(0, options.maxFiles);
    }
    
    return files;
  }
}