Stirling-PDF/frontend/src/services/pdfMetadataService.ts

import { pdfWorkerManager } from './pdfWorkerManager';
import { FileAnalyzer } from './fileAnalyzer';
import { TrappedStatus, CustomMetadataEntry, ExtractedPDFMetadata } from '../types/metadata';
import { PDFDocumentProxy } from 'pdfjs-dist/types/src/display/api';

export interface MetadataExtractionResult {
  success: true;
  metadata: ExtractedPDFMetadata;
}

export interface MetadataExtractionError {
  success: false;
  error: string;
}

export type MetadataExtractionResponse = MetadataExtractionResult | MetadataExtractionError;

/**
 * Utility to format PDF date strings to required format (yyyy/MM/dd HH:mm:ss)
 * Handles PDF date format: "D:YYYYMMDDHHmmSSOHH'mm'" or standard date strings
 */
function formatPDFDate(dateString: string): string {
  if (!dateString) {
    return '';
  }

  let date: Date;

  // Check if it's a PDF date format (starts with "D:")
  if (dateString.startsWith('D:')) {
    // Parse PDF date format: D:YYYYMMDDHHmmSSOHH'mm'
    const dateStr = dateString.substring(2); // Remove "D:"

    // Extract date parts
    const year = parseInt(dateStr.substring(0, 4));
    const month = parseInt(dateStr.substring(4, 6));
    const day = parseInt(dateStr.substring(6, 8));
    const hour = parseInt(dateStr.substring(8, 10)) || 0;
    const minute = parseInt(dateStr.substring(10, 12)) || 0;
    const second = parseInt(dateStr.substring(12, 14)) || 0;

    // Create date object (month is 0-indexed)
    date = new Date(year, month - 1, day, hour, minute, second);
  } else {
    // Try parsing as regular date string
    date = new Date(dateString);
  }

  if (isNaN(date.getTime())) {
    return '';
  }

  const year = date.getFullYear();
  const month = String(date.getMonth() + 1).padStart(2, '0');
  const day = String(date.getDate()).padStart(2, '0');
  const hours = String(date.getHours()).padStart(2, '0');
  const minutes = String(date.getMinutes()).padStart(2, '0');
  const seconds = String(date.getSeconds()).padStart(2, '0');

  return `${year}/${month}/${day} ${hours}:${minutes}:${seconds}`;
}

/**
 * Convert PDF.js trapped value to TrappedStatus enum
 * PDF.js returns trapped as { name: "True" | "False" } object
 */
function convertTrappedStatus(trapped: unknown): TrappedStatus {
  if (trapped && typeof trapped === 'object' && 'name' in trapped) {
    const name = (trapped as Record<string, string>).name?.toLowerCase();
    if (name === 'true') return TrappedStatus.TRUE;
    if (name === 'false') return TrappedStatus.FALSE;
  }
  return TrappedStatus.UNKNOWN;
}

/**
 * Extract custom metadata fields from PDF.js info object
 * Custom metadata is nested under the "Custom" key
 */
function extractCustomMetadata(custom: unknown): CustomMetadataEntry[] {
  const customMetadata: CustomMetadataEntry[] = [];
  let customIdCounter = 1;


  // Check if there's a Custom object containing the custom metadata
  if (typeof custom === 'object' && custom !== null) {
    const customObj = custom as Record<string, unknown>;

    Object.entries(customObj).forEach(([key, value]) => {
      if (value != null && value !== '') {
        const entry = {
          key,
          value: String(value),
          id: `custom${customIdCounter++}`
        };
        customMetadata.push(entry);
      }
    });
  }

  return customMetadata;
}

/**
 * Safely cleanup PDF document with error handling
 */
function cleanupPdfDocument(pdfDoc: PDFDocumentProxy | null): void {
  if (pdfDoc) {
    try {
      pdfWorkerManager.destroyDocument(pdfDoc);
    } catch (cleanupError) {
      console.warn('Failed to cleanup PDF document:', cleanupError);
    }
  }
}

function getStringMetadata(info: Record<string, unknown>, key: string): string {
  if (typeof info[key] === 'string') {
    return info[key];
  } else {
    return '';
  }
}

/**
 * Extract all metadata from a PDF file
 * Returns a result object with success/error state
 */
export async function extractPDFMetadata(file: File): Promise<MetadataExtractionResponse> {
  // Use existing PDF validation
  const isValidPDF = await FileAnalyzer.isValidPDF(file);
  if (!isValidPDF) {
    return {
      success: false,
      error: 'File is not a valid PDF'
    };
  }

  let pdfDoc: PDFDocumentProxy | null = null;
  let arrayBuffer: ArrayBuffer;
  let metadata;

  try {
    arrayBuffer = await file.arrayBuffer();
    pdfDoc = await pdfWorkerManager.createDocument(arrayBuffer, {
      disableAutoFetch: true,
      disableStream: true
    });
    metadata = await pdfDoc.getMetadata();
  } catch (error) {
    const errorMessage = error instanceof Error ? error.message : 'Unknown error';
    cleanupPdfDocument(pdfDoc);
    return {
      success: false,
      error: `Failed to read PDF: ${errorMessage}`
    };
  }

  const info = metadata.info as Record<string, unknown>;

  // Safely extract metadata with proper type checking
  const extractedMetadata: ExtractedPDFMetadata = {
    title: getStringMetadata(info, 'Title'),
    author: getStringMetadata(info, 'Author'),
    subject: getStringMetadata(info, 'Subject'),
    keywords: getStringMetadata(info, 'Keywords'),
    creator: getStringMetadata(info, 'Creator'),
    producer: getStringMetadata(info, 'Producer'),
    creationDate: formatPDFDate(getStringMetadata(info, 'CreationDate')),
    modificationDate: formatPDFDate(getStringMetadata(info, 'ModDate')),
    trapped: convertTrappedStatus(info.Trapped),
    customMetadata: extractCustomMetadata(info.Custom),
  };

  cleanupPdfDocument(pdfDoc);

  return {
    success: true,
    metadata: extractedMetadata
  };
}