@fin.cx/einvoice
Version:
A TypeScript module for creating, manipulating, and embedding XML data within PDF files specifically tailored for electronic invoice (einvoice) packages.
355 lines (317 loc) • 10.8 kB
text/typescript
import { PDFDocument, PDFDict, PDFName, PDFRawStream, PDFArray, PDFString, pako } from '../../../plugins.js';
/**
* Base class for PDF XML extractors with common functionality
*/
export abstract class BaseXMLExtractor {
/**
* Known XML file names for different invoice formats
*/
protected readonly knownFileNames = [
'factur-x.xml',
'zugferd-invoice.xml',
'ZUGFeRD-invoice.xml',
'xrechnung.xml',
'ubl-invoice.xml',
'invoice.xml',
'metadata.xml'
];
/**
* Known XML formats to validate extracted content
*/
protected readonly knownFormats = [
'CrossIndustryInvoice',
'CrossIndustryDocument',
'Invoice',
'CreditNote',
'ubl:Invoice',
'ubl:CreditNote',
'rsm:CrossIndustryInvoice',
'rsm:CrossIndustryDocument',
'ram:CrossIndustryDocument',
'urn:un:unece:uncefact',
'urn:ferd:CrossIndustryDocument',
'urn:zugferd',
'urn:factur-x',
'factur-x.eu',
'ZUGFeRD',
'FatturaElettronica'
];
/**
* Known XML end tags for extracting content from strings
*/
protected readonly knownEndTags = [
'</CrossIndustryInvoice>',
'</CrossIndustryDocument>',
'</Invoice>',
'</CreditNote>',
'</rsm:CrossIndustryInvoice>',
'</rsm:CrossIndustryDocument>',
'</ram:CrossIndustryDocument>',
'</ubl:Invoice>',
'</ubl:CreditNote>',
'</FatturaElettronica>'
];
/**
* Extract XML from a PDF buffer
* @param pdfBuffer PDF buffer
* @returns XML content or null if not found
*/
public abstract extractXml(pdfBuffer: Uint8Array | Buffer): Promise<string | null>;
/**
* Check if an XML string is valid
* @param xmlString XML string to check
* @returns True if the XML is valid
*/
protected isValidXml(xmlString: string): boolean {
try {
// Basic checks for XML validity
if (!xmlString || typeof xmlString !== 'string') {
return false;
}
// Check if it starts with XML declaration or a valid element
if (!xmlString.includes('<?xml') && !this.hasKnownXmlElement(xmlString)) {
return false;
}
// Check if the XML string contains known invoice formats
const hasKnownFormat = this.hasKnownFormat(xmlString);
if (!hasKnownFormat) {
return false;
}
// Check if the XML string contains binary data or invalid characters
if (this.hasBinaryData(xmlString)) {
return false;
}
// Check if the XML string is too short
if (xmlString.length < 100) {
return false;
}
// Check if XML has a proper structure (contains both opening and closing tags)
if (!this.hasProperXmlStructure(xmlString)) {
return false;
}
return true;
} catch (error) {
console.error('Error validating XML:', error);
return false;
}
}
/**
* Check if the XML string contains a known element
* @param xmlString XML string to check
* @returns True if the XML contains a known element
*/
protected hasKnownXmlElement(xmlString: string): boolean {
for (const format of this.knownFormats) {
// Check for opening tag of format
if (xmlString.includes(`<${format}`)) {
return true;
}
}
return false;
}
/**
* Check if the XML string contains a known format
* @param xmlString XML string to check
* @returns True if the XML contains a known format
*/
protected hasKnownFormat(xmlString: string): boolean {
for (const format of this.knownFormats) {
if (xmlString.includes(format)) {
return true;
}
}
return false;
}
/**
* Check if the XML string has a proper structure
* @param xmlString XML string to check
* @returns True if the XML has a proper structure
*/
protected hasProperXmlStructure(xmlString: string): boolean {
// Check for at least one matching opening and closing tag
for (const endTag of this.knownEndTags) {
const startTag = endTag.replace('/', '');
if (xmlString.includes(startTag) && xmlString.includes(endTag)) {
return true;
}
}
// If no specific tag is found but it has a basic XML structure
return (
(xmlString.includes('<?xml') && xmlString.includes('?>')) ||
(xmlString.match(/<[^>]+>/) !== null && xmlString.match(/<\/[^>]+>/) !== null)
);
}
/**
* Check if the XML string contains binary data
* @param xmlString XML string to check
* @returns True if the XML contains binary data
*/
protected hasBinaryData(xmlString: string): boolean {
// Check for common binary data indicators
const binaryChars = ['\u0000', '\u0001', '\u0002', '\u0003', '\u0004', '\u0005'];
const consecutiveNulls = '\u0000\u0000\u0000';
// Check for control characters that shouldn't be in XML
if (binaryChars.some(char => xmlString.includes(char))) {
return true;
}
// Check for consecutive null bytes which indicate binary data
if (xmlString.includes(consecutiveNulls)) {
return true;
}
// Check for high concentration of non-printable characters
const nonPrintableCount = (xmlString.match(/[\x00-\x08\x0B\x0C\x0E-\x1F]/g) || []).length;
if (nonPrintableCount > xmlString.length * 0.05) { // More than 5% non-printable
return true;
}
return false;
}
/**
* Extract XML from a string
* @param text Text to extract XML from
* @param startIndex Index to start extraction from
* @returns XML content or null if not found
*/
protected extractXmlFromString(text: string, startIndex: number = 0): string | null {
try {
// Find the start of the XML document
let xmlStartIndex = text.indexOf('<?xml', startIndex);
// If no XML declaration, try to find known elements
if (xmlStartIndex === -1) {
for (const format of this.knownFormats) {
const formatStartIndex = text.indexOf(`<${format.split(':').pop()}`, startIndex);
if (formatStartIndex !== -1) {
xmlStartIndex = formatStartIndex;
break;
}
}
// Still didn't find any start marker
if (xmlStartIndex === -1) {
return null;
}
}
// Try to find the end of the XML document
let xmlEndIndex = -1;
for (const endTag of this.knownEndTags) {
const endIndex = text.indexOf(endTag, xmlStartIndex);
if (endIndex !== -1) {
xmlEndIndex = endIndex + endTag.length;
break;
}
}
// If no known end tag found, try to use a heuristic approach
if (xmlEndIndex === -1) {
// Try to find the last closing tag
const lastClosingTagMatch = text.slice(xmlStartIndex).match(/<\/[^>]+>(?!.*<\/[^>]+>)/);
if (lastClosingTagMatch && lastClosingTagMatch.index !== undefined) {
xmlEndIndex = xmlStartIndex + lastClosingTagMatch.index + lastClosingTagMatch[0].length;
} else {
return null;
}
}
// Extract the XML content
const xmlContent = text.substring(xmlStartIndex, xmlEndIndex);
// Validate the extracted content
if (this.isValidXml(xmlContent)) {
return xmlContent;
}
return null;
} catch (error) {
console.error('Error extracting XML from string:', error);
return null;
}
}
/**
* Decompress and decode XML content from a PDF stream
* @param stream PDF stream containing XML data
* @param fileName Name of the file (for logging)
* @returns XML content or null if not valid
*/
protected async extractXmlFromStream(stream: PDFRawStream, fileName: string): Promise<string | null> {
try {
// Get the raw bytes from the stream
const rawBytes = stream.getContents();
// First try without decompression (in case the content is not compressed)
let xmlContent = this.tryDecodeBuffer(rawBytes);
if (xmlContent && this.isValidXml(xmlContent)) {
console.log(`Successfully extracted uncompressed XML from PDF file. File name: ${fileName}`);
return xmlContent;
}
// Try with decompression
try {
const decompressedBytes = this.tryDecompress(rawBytes);
if (decompressedBytes) {
xmlContent = this.tryDecodeBuffer(decompressedBytes);
if (xmlContent && this.isValidXml(xmlContent)) {
console.log(`Successfully extracted decompressed XML from PDF file. File name: ${fileName}`);
return xmlContent;
}
}
} catch (decompressError) {
console.log(`Decompression failed for ${fileName}: ${decompressError}`);
}
return null;
} catch (error) {
console.error('Error extracting XML from stream:', error);
return null;
}
}
/**
* Try to decompress a buffer using different methods
* @param buffer Buffer to decompress
* @returns Decompressed buffer or null if decompression failed
*/
protected tryDecompress(buffer: Uint8Array): Uint8Array | null {
try {
// Try pako inflate (for deflate/zlib compression)
return pako.inflate(buffer);
} catch (error) {
// If pako fails, try other methods if needed
console.warn('Pako decompression failed, might be uncompressed or using a different algorithm');
return null;
}
}
/**
* Try to decode a buffer to a string using different encodings
* @param buffer Buffer to decode
* @returns Decoded string or null if decoding failed
*/
protected tryDecodeBuffer(buffer: Uint8Array): string | null {
try {
// Try UTF-8 first
let content = new TextDecoder('utf-8').decode(buffer);
if (this.isPlausibleXml(content)) {
return content;
}
// Try ISO-8859-1 (Latin1)
content = this.decodeLatin1(buffer);
if (this.isPlausibleXml(content)) {
return content;
}
return null;
} catch (error) {
console.warn('Error decoding buffer:', error);
return null;
}
}
/**
* Decode a buffer using ISO-8859-1 (Latin1) encoding
* @param buffer Buffer to decode
* @returns Decoded string
*/
protected decodeLatin1(buffer: Uint8Array): string {
return Array.from(buffer)
.map(byte => String.fromCharCode(byte))
.join('');
}
/**
* Check if a string is plausibly XML (quick check before validation)
* @param content String to check
* @returns True if the string is plausibly XML
*/
protected isPlausibleXml(content: string): boolean {
return content.includes('<') &&
content.includes('>') &&
(content.includes('<?xml') ||
this.knownFormats.some(format => content.includes(format)));
}
}