PDFPatcher/App/Model/PdfPathDocument.cs

using System;
using System.Collections.Generic;
using iTextSharp.text.pdf;
using PDFPatcher.Processor;

namespace PDFPatcher.Model
{
	sealed class PdfPathDocument : IHierarchicalObject<DocumentObject>
	{
		const int pageGroupNumber = 100;
		readonly PdfReader _pdf;
		readonly DocumentObject[] _rootObjects;
		readonly DocumentObject _trailer;
		readonly DocumentObject _hiddenObjects;
		readonly Dictionary<int, int> _pageMapper;

		public PdfPathDocument(string pdfPath) {
			_pdf = PdfHelper.OpenPdfFile(pdfPath, AppContext.LoadPartialPdfFile, false);
			_pageMapper = _pdf.GetPageRefMapper();
			_trailer = new DocumentObject(this, null, "Trailer", _pdf.Trailer, PdfObjectType.Trailer) {
				IsKeyObject = true,
				Description = "文档根节点",
				FriendlyValue = System.IO.Path.GetFileNameWithoutExtension(pdfPath)
			};
			_hiddenObjects = new DocumentObject(this, null, "隐藏对象", null, PdfObjectType.Hidden);
			var l = _pdf.NumberOfPages;
			if (l > 301) {
				var c = new DocumentObject[1 + (l + pageGroupNumber - 1) / pageGroupNumber + 1];
				c[0] = _trailer;
				for (int i = 1; i < c.Length - 1; i++) {
					var a = (i - 1) * pageGroupNumber + 1;
					var b = Math.Min(l, i * pageGroupNumber);
					c[i] = new DocumentObject(this, null, "Pages", null, PdfObjectType.Pages) { IsKeyObject = true, ExtensiveObject = $"{a}-{b}", FriendlyValue = $"第 {a} 至 {b} 页，共 {l} 页" };
				}
				c[c.Length - 1] = _hiddenObjects;
				_rootObjects = c;
			}
			else {
				_rootObjects = [
					_trailer,
					new DocumentObject (this, null, "Pages", null, PdfObjectType.Pages) { IsKeyObject = true, FriendlyValue = "共 " + l + " 页" },
					_hiddenObjects
				];
			}
		}

		public PdfReader Document => _pdf;

		public DocumentObject Trailer => _trailer;

		public int PageCount => _pdf.NumberOfPages;

		public void Close() {
			_pdf.Close();
		}

		public int GetPageNumber(PdfIndirectReference pdfRef) {
			_pageMapper.TryGetValue(pdfRef.Number, out int page);
			return page;
		}

		#region IHierarchicalObject<DocumentObject> 成员

		bool IHierarchicalObject<DocumentObject>.HasChildren => true;

		ICollection<DocumentObject> IHierarchicalObject<DocumentObject>.Children {
			get {
				var c = new DocumentObject[_rootObjects.Length];
				Array.Copy(_rootObjects, c, _rootObjects.Length);
				return c;
			}
		}

		#endregion
	}
}