@fin.cx/einvoice/dist_ts/formats/pdf/extractors/text.extractor.js

A TypeScript module for creating, manipulating, and embedding XML data within PDF files specifically tailored for electronic invoice (einvoice) packages.

import { BaseXMLExtractor } from './base.extractor.js';
/**
 * Text-based XML extractor for PDF documents
 * Extracts XML by searching for XML patterns in the PDF text
 * Used as a fallback when other extraction methods fail
 */
export class TextXMLExtractor extends BaseXMLExtractor {
    constructor() {
        super(...arguments);
        // Maximum chunk size to process at once (4MB)
        this.CHUNK_SIZE = 4 * 1024 * 1024;
        // Maximum number of chunks to check (effective 20MB search limit)
        this.MAX_CHUNKS = 5;
        // Common XML patterns to look for
        this.XML_PATTERNS = [
            '<?xml',
            '<CrossIndustryInvoice',
            '<CrossIndustryDocument',
            '<Invoice',
            '<CreditNote',
            '<rsm:CrossIndustryInvoice',
            '<rsm:CrossIndustryDocument',
            '<ram:CrossIndustryDocument',
            '<ubl:Invoice',
            '<ubl:CreditNote',
            '<FatturaElettronica'
        ];
    }
    /**
     * Extract XML from a PDF buffer by searching for XML patterns in the text
     * Uses a chunked approach to handle large files efficiently
     * @param pdfBuffer PDF buffer
     * @returns XML content or null if not found
     */
    async extractXml(pdfBuffer) {
        try {
            console.log('Attempting text-based XML extraction from PDF...');
            // Convert Buffer to Uint8Array if needed
            const buffer = Buffer.isBuffer(pdfBuffer) ? new Uint8Array(pdfBuffer) : pdfBuffer;
            // Try extracting XML using the chunked approach
            return this.extractXmlFromBufferChunked(buffer);
        }
        catch (error) {
            console.error('Error in text-based extraction:', error);
            return null;
        }
    }
    /**
     * Extract XML from buffer using a chunked approach
     * This helps avoid memory issues with large PDFs
     * @param buffer Buffer to search in
     * @returns XML content or null if not found
     */
    extractXmlFromBufferChunked(buffer) {
        // Process the PDF in chunks
        for (let chunkIndex = 0; chunkIndex < this.MAX_CHUNKS; chunkIndex++) {
            const startPos = chunkIndex * this.CHUNK_SIZE;
            if (startPos >= buffer.length)
                break;
            const endPos = Math.min(startPos + this.CHUNK_SIZE, buffer.length);
            const chunk = buffer.slice(startPos, endPos);
            // Try to extract XML from this chunk
            const chunkResult = this.processChunk(chunk, startPos);
            if (chunkResult) {
                return chunkResult;
            }
        }
        console.warn('No valid XML found in any chunk of the PDF');
        return null;
    }
    /**
     * Process a single chunk of the PDF buffer
     * @param chunk Chunk buffer to process
     * @param chunkOffset Offset position of the chunk in the original buffer
     * @returns XML content or null if not found
     */
    processChunk(chunk, chunkOffset) {
        try {
            // First try UTF-8 encoding for this chunk
            const utf8String = this.decodeBufferToString(chunk, 'utf-8');
            let xmlContent = this.searchForXmlInString(utf8String);
            if (xmlContent) {
                console.log(`Found XML content in chunk at offset ${chunkOffset} using UTF-8 encoding`);
                return xmlContent;
            }
            // If UTF-8 fails, try Latin-1 (ISO-8859-1) which can handle binary better
            const latin1String = this.decodeBufferToString(chunk, 'latin1');
            xmlContent = this.searchForXmlInString(latin1String);
            if (xmlContent) {
                console.log(`Found XML content in chunk at offset ${chunkOffset} using Latin-1 encoding`);
                return xmlContent;
            }
            // No XML found in this chunk
            return null;
        }
        catch (error) {
            console.warn(`Error processing chunk at offset ${chunkOffset}:`, error);
            return null;
        }
    }
    /**
     * Safely decode a buffer to string using the specified encoding
     * @param buffer Buffer to decode
     * @param encoding Encoding to use ('utf-8' or 'latin1')
     * @returns Decoded string
     */
    decodeBufferToString(buffer, encoding) {
        try {
            if (encoding === 'utf-8') {
                return new TextDecoder('utf-8', { fatal: false }).decode(buffer);
            }
            else {
                // For Latin-1 we can use a direct mapping (bytes 0-255 map directly to code points 0-255)
                // This is more reliable for binary data than TextDecoder for legacy encodings
                return Array.from(buffer)
                    .map(byte => String.fromCharCode(byte))
                    .join('');
            }
        }
        catch (error) {
            console.warn(`Error decoding buffer using ${encoding}:`, error);
            // Return empty string on error to allow processing to continue
            return '';
        }
    }
    /**
     * Search for XML patterns in a string
     * @param content String to search in
     * @returns XML content or null if not found
     */
    searchForXmlInString(content) {
        if (!content)
            return null;
        // Search for each XML pattern
        for (const pattern of this.XML_PATTERNS) {
            const patternIndex = content.indexOf(pattern);
            if (patternIndex !== -1) {
                console.log(`Found XML pattern "${pattern}" at position ${patternIndex}`);
                // Try to extract the XML content starting from the pattern position
                const xmlContent = this.extractXmlFromString(content, patternIndex);
                // Validate the extracted content
                if (xmlContent && this.isValidXml(xmlContent)) {
                    console.log('Successfully extracted and validated XML from text');
                    return xmlContent;
                }
            }
        }
        return null;
    }
}
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