import * as plugins from './plugins.js';
import * as interfaces from './interfaces.js';
import {
  PDFDocument,
  PDFDict,
  PDFName,
  PDFRawStream,
  PDFArray,
  PDFString,
} from 'pdf-lib';
import { ZugferdXmlEncoder } from './classes.encoder.js';
import { ZUGFeRDXmlDecoder } from './classes.decoder.js';

export class XInvoice {
  private xmlString: string;
  private letterData: plugins.tsclass.business.ILetter;
  private pdfUint8Array: Uint8Array;

  private encoderInstance = new ZugferdXmlEncoder(); 
  private decoderInstance: ZUGFeRDXmlDecoder;
  
  constructor() {
    // Decoder will be initialized when we have XML data
  }

  public async addPdfBuffer(pdfBuffer: Uint8Array | Buffer): Promise<void> {
    this.pdfUint8Array = Uint8Array.from(pdfBuffer);
  }

  public async addXmlString(xmlString: string): Promise<void> {
    // Basic XML validation - just check if it starts with <?xml
    if (!xmlString || !xmlString.trim().startsWith('<?xml')) {
      throw new Error('Invalid XML: Missing XML declaration');
    }
    
    // Store the XML string
    this.xmlString = xmlString;
    
    // Initialize the decoder with the XML string
    this.decoderInstance = new ZUGFeRDXmlDecoder(xmlString);
  }

  public async addLetterData(letterData: plugins.tsclass.business.ILetter): Promise<void> {
    this.letterData = letterData;
  }

  public async getXInvoice(): Promise<void> {
    // lets check requirements
    if (!this.pdfUint8Array) {
      throw new Error('No PDF buffer provided!');
    }
    if (!this.xmlString || !this.letterData) {
      // TODO: check if document already has xml

      throw new Error('No XML string or letter data provided!');
    }


    try {
      const pdfDoc = await PDFDocument.load(this.pdfUint8Array);

      // Convert the XML string to a Uint8Array
      const xmlBuffer = new TextEncoder().encode(this.xmlString);

      // Use pdf-lib's .attach() to embed the XML
      pdfDoc.attach(xmlBuffer, plugins.path.basename('invoice.xml'), {
        mimeType: 'application/xml',
        description: 'XRechnung XML Invoice',
      });

      // Save back into this.pdfUint8Array
      const modifiedPdfBytes = await pdfDoc.save();
      this.pdfUint8Array = modifiedPdfBytes;
      console.log(`PDF Buffer updated with new XML attachment!`);
    } catch (error) {
      console.error('Error embedding XML into PDF:', error);
      throw error;
    }
  }

  /**
   * Reads the XML embedded in a PDF and returns it as a string.
   * Validates that it's a properly formatted XInvoice/ZUGFeRD document.
   */
  public async getXmlData(): Promise<string> {
    if (!this.pdfUint8Array) {
      throw new Error('No PDF buffer provided! Use addPdfBuffer() first.');
    }
    
    try {
      const pdfDoc = await PDFDocument.load(this.pdfUint8Array);

      // Get the document's metadata dictionary
      const namesDictObj = pdfDoc.catalog.lookup(PDFName.of('Names'));
      if (!(namesDictObj instanceof PDFDict)) {
        throw new Error('No Names dictionary found in PDF! This PDF does not contain embedded files.');
      }

      const embeddedFilesDictObj = namesDictObj.lookup(PDFName.of('EmbeddedFiles'));
      if (!(embeddedFilesDictObj instanceof PDFDict)) {
        throw new Error('No EmbeddedFiles dictionary found! This PDF does not contain embedded files.');
      }

      const filesSpecObj = embeddedFilesDictObj.lookup(PDFName.of('Names'));
      if (!(filesSpecObj instanceof PDFArray)) {
        throw new Error('No files specified in EmbeddedFiles dictionary!');
      }

      // Try to find an XML file in the embedded files
      let xmlFile: PDFRawStream | undefined;
      let xmlFileName: string | undefined;

      for (let i = 0; i < filesSpecObj.size(); i += 2) {
        const fileNameObj = filesSpecObj.lookup(i);
        const fileSpecObj = filesSpecObj.lookup(i + 1);

        if (!(fileNameObj instanceof PDFString)) {
          continue;
        }
        if (!(fileSpecObj instanceof PDFDict)) {
          continue;
        }

        // Get the filename as string - using string access since value() might not be available in all contexts
        const fileName = fileNameObj.toString();
        
        // Check if it's an XML file (simple check - improved would check MIME type)
        if (fileName.toLowerCase().includes('.xml')) {
          const efDictObj = fileSpecObj.lookup(PDFName.of('EF'));
          if (!(efDictObj instanceof PDFDict)) {
            continue;
          }

          const maybeStream = efDictObj.lookup(PDFName.of('F'));
          if (maybeStream instanceof PDFRawStream) {
            // Found an XML file - save it
            xmlFile = maybeStream;
            xmlFileName = fileName;
            break;
          }
        }
      }

      // If no XML file was found, throw an error
      if (!xmlFile) {
        throw new Error('No embedded XML file found in the PDF!');
      }

      // Decompress and decode the XML content
      const xmlCompressedBytes = xmlFile.getContents().buffer;
      const xmlBytes = plugins.pako.inflate(xmlCompressedBytes);
      const xmlContent = new TextDecoder('utf-8').decode(xmlBytes);

      // Store this XML string
      this.xmlString = xmlContent;
      
      // Initialize the decoder with the XML string if needed
      if (!this.decoderInstance) {
        this.decoderInstance = new ZUGFeRDXmlDecoder(xmlContent);
      }
      
      // Validate the XML format
      const format = this.identifyXmlFormat(xmlContent);
      
      // Log information about the extracted XML
      console.log(`Successfully extracted ${format} XML from PDF file. File name: ${xmlFileName}`);
      
      return xmlContent;
    } catch (error) {
      console.error('Error extracting or parsing embedded XML from PDF:', error);
      throw error;
    }
  }
  
  /**
   * Validates the format of an XML document and returns the identified format
   */
  private identifyXmlFormat(xmlContent: string): string {
    // Simple detection based on string content
    
    // Check for ZUGFeRD/CII
    if (xmlContent.includes('CrossIndustryInvoice') || 
        xmlContent.includes('rsm:') || 
        xmlContent.includes('ram:')) {
      return 'ZUGFeRD/CII';
    }
    
    // Check for UBL
    if (xmlContent.includes('<Invoice') || 
        xmlContent.includes('ubl:Invoice') || 
        xmlContent.includes('oasis:names:specification:ubl')) {
      return 'UBL';
    }
    
    // Check for FatturaPA
    if (xmlContent.includes('FatturaElettronica') || 
        xmlContent.includes('fatturapa.gov.it')) {
      return 'FatturaPA';
    }
    
    // For unknown formats, return generic
    return 'Unknown';
  }

  public async getParsedXmlData(): Promise<interfaces.IXInvoice> {
    if (!this.xmlString && !this.pdfUint8Array) {
      throw new Error('No XML string or PDF buffer provided!');
    }
    
    let localXmlString = this.xmlString;
    if (!localXmlString) {
      localXmlString = await this.getXmlData();
    }
    
    return this.parseXmlToInvoice(localXmlString);
  }

  /**
   * Parses XML content into a structured IXInvoice object
   * Supports different XML invoice formats (ZUGFeRD, UBL, CII)
   */
  private parseXmlToInvoice(xmlContent: string): interfaces.IXInvoice {
    if (!xmlContent) {
      throw new Error('No XML content provided for parsing');
    }
    
    try {
      // Initialize the decoder with XML content if not already done
      this.decoderInstance = new ZUGFeRDXmlDecoder(xmlContent);
      
      // First, attempt to identify the XML format
      const format = this.identifyXmlFormat(xmlContent);
      
      // Parse XML based on detected format
      switch (format) {
        case 'ZUGFeRD/CII':
          return this.parseCIIFormat(xmlContent);
          
        case 'UBL':
          return this.parseUBLFormat(xmlContent);
          
        case 'FatturaPA':
          return this.parseFatturaPAFormat(xmlContent);
          
        default:
          // If format unrecognized, try generic parsing
          return this.parseGenericXml(xmlContent);
      }
    } catch (error) {
      console.error('Error parsing XML to invoice structure:', error);
      throw new Error(`Failed to parse XML: ${error.message}`);
    }
  }
  
  /**
   * Helper to extract XML values using regex
   */
  private extractXmlValueByRegex(xmlContent: string, tagName: string): string {
    const regex = new RegExp(`<${tagName}[^>]*>([^<]+)</${tagName}>`, 'i');
    const match = xmlContent.match(regex);
    return match ? match[1].trim() : '';
  }
  
  /**
   * Parses CII/ZUGFeRD format XML
   */
  private parseCIIFormat(xmlContent: string): interfaces.IXInvoice {
    // For demo implementation, just extract basic information using string operations
    try {
      // Extract invoice number - basic pattern matching
      let invoiceNumber = 'Unknown';
      const invoiceNumberMatch = xmlContent.match(/<ram:ID>([^<]+)<\/ram:ID>/);
      if (invoiceNumberMatch && invoiceNumberMatch[1]) {
        invoiceNumber = invoiceNumberMatch[1].trim();
      }
      
      // Extract date - basic pattern matching
      let dateIssued = new Date().toISOString().split('T')[0];
      const dateMatch = xmlContent.match(/<udt:DateTimeString[^>]*>([^<]+)<\/udt:DateTimeString>/);
      if (dateMatch && dateMatch[1]) {
        dateIssued = dateMatch[1].trim();
      }
      
      // Extract seller name - basic pattern matching
      let sellerName = 'Unknown Seller';
      const sellerMatch = xmlContent.match(/<ram:SellerTradeParty>.*?<ram:Name>([^<]+)<\/ram:Name>/s);
      if (sellerMatch && sellerMatch[1]) {
        sellerName = sellerMatch[1].trim();
      }
      
      // Extract buyer name - basic pattern matching
      let buyerName = 'Unknown Buyer';
      const buyerMatch = xmlContent.match(/<ram:BuyerTradeParty>.*?<ram:Name>([^<]+)<\/ram:Name>/s);
      if (buyerMatch && buyerMatch[1]) {
        buyerName = buyerMatch[1].trim();
      }
      
      // For this demo implementation, create a minimal invoice structure
      return {
        InvoiceNumber: invoiceNumber,
        DateIssued: dateIssued,
        Seller: {
          Name: sellerName,
          Address: {
            Street: 'Unknown',
            City: 'Unknown',
            PostalCode: 'Unknown',
            Country: 'Unknown',
          },
          Contact: {
            Email: 'unknown@example.com',
            Phone: 'Unknown',
          },
        },
        Buyer: {
          Name: buyerName,
          Address: {
            Street: 'Unknown',
            City: 'Unknown',
            PostalCode: 'Unknown',
            Country: 'Unknown',
          },
          Contact: {
            Email: 'unknown@example.com',
            Phone: 'Unknown',
          },
        },
        Items: [
          {
            Description: 'Unknown Item',
            Quantity: 1,
            UnitPrice: 0,
            TotalPrice: 0,
          },
        ],
        TotalAmount: 0,
      };
    } catch (error) {
      console.error('Error parsing CII format:', error);
      return this.parseGenericXml(xmlContent); // Fallback
    }
  }
  
  /**
   * Parses UBL format XML
   */
  private parseUBLFormat(xmlContent: string): interfaces.IXInvoice {
    // Simplified UBL parsing - just extract basic fields
    try {
      const invoiceNumber = this.extractXmlValueByRegex(xmlContent, 'cbc:ID');
      const dateIssued = this.extractXmlValueByRegex(xmlContent, 'cbc:IssueDate');
      const sellerName = this.extractXmlValueByRegex(xmlContent, 'cac:AccountingSupplierParty.*?cbc:Name');
      const buyerName = this.extractXmlValueByRegex(xmlContent, 'cac:AccountingCustomerParty.*?cbc:Name');
      
      return {
        InvoiceNumber: invoiceNumber || 'Unknown',
        DateIssued: dateIssued || new Date().toISOString().split('T')[0],
        Seller: {
          Name: sellerName || 'Unknown Seller',
          Address: {
            Street: 'Unknown',
            City: 'Unknown',
            PostalCode: 'Unknown',
            Country: 'Unknown',
          },
          Contact: {
            Email: 'unknown@example.com',
            Phone: 'Unknown',
          },
        },
        Buyer: {
          Name: buyerName || 'Unknown Buyer',
          Address: {
            Street: 'Unknown',
            City: 'Unknown',
            PostalCode: 'Unknown',
            Country: 'Unknown',
          },
          Contact: {
            Email: 'unknown@example.com',
            Phone: 'Unknown',
          },
        },
        Items: [
          {
            Description: 'Unknown Item',
            Quantity: 1,
            UnitPrice: 0,
            TotalPrice: 0,
          },
        ],
        TotalAmount: 0,
      };
    } catch (error) {
      console.error('Error parsing UBL format:', error);
      return this.parseGenericXml(xmlContent);
    }
  }
  
  /**
   * Parses fatturaPA format XML
   */
  private parseFatturaPAFormat(xmlContent: string): interfaces.IXInvoice {
    // In a full implementation, this would have fatturaPA-specific parsing
    // For now, using a simplified generic parser
    return this.parseGenericXml(xmlContent);
  }
  
  /**
   * Generic XML parser that attempts to extract invoice data
   * from any XML structure
   */
  private parseGenericXml(xmlContent: string): interfaces.IXInvoice {
    // For now, returning a placeholder structure
    // This would be replaced with more intelligent parsing
    return {
      InvoiceNumber: '(Unknown format - invoice number not extracted)',
      DateIssued: new Date().toISOString().split('T')[0],
      Seller: {
        Name: 'Unknown Seller (format not recognized)',
        Address: {
          Street: 'Unknown',
          City: 'Unknown',
          PostalCode: 'Unknown',
          Country: 'Unknown',
        },
        Contact: {
          Email: 'unknown@example.com',
          Phone: 'Unknown',
        },
      },
      Buyer: {
        Name: 'Unknown Buyer (format not recognized)',
        Address: {
          Street: 'Unknown',
          City: 'Unknown',
          PostalCode: 'Unknown',
          Country: 'Unknown',
        },
        Contact: {
          Email: 'unknown@example.com',
          Phone: 'Unknown',
        },
      },
      Items: [
        {
          Description: 'Unknown items (invoice format not recognized)',
          Quantity: 1,
          UnitPrice: 0,
          TotalPrice: 0,
        },
      ],
      TotalAmount: 0,
    };
  }
}