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

import { pdfWorkerManager } from "@app/services/pdfWorkerManager";
import { FileAnalyzer } from "@app/services/fileAnalyzer";
import { TrappedStatus, CustomMetadataEntry, ExtractedPDFMetadata } from "@app/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,
  };
}