PDFPatcher/App/Processor/InfoXmlProcessors/ChangePageNumberProcessor.cs

using System;
using PDFPatcher.Common;

namespace PDFPatcher.Processor
{
	sealed class ChangePageNumberProcessor : IPdfInfoXmlProcessor
	{
		public bool IsAbsolute { get; }
		public int Amount { get; }
		public bool SkipZero { get; }

		public ChangePageNumberProcessor(int amount) : this(amount, false, false) { }
		public ChangePageNumberProcessor(int amount, bool isAbsolute, bool skipZero) {
			IsAbsolute = isAbsolute;
			Amount = amount;
			SkipZero = skipZero;
		}

		#region IInfoDocProcessor 成员

		public string Name => "更改目标页码";

		public IUndoAction Process(System.Xml.XmlElement item) {
			int p;
			var a = item.GetAttribute(Constants.DestinationAttributes.Action);
			if ((String.IsNullOrEmpty(a) && SkipZero == false || a == Constants.ActionType.Goto || a == Constants.ActionType.GotoR) == false && item.HasAttribute(Constants.DestinationAttributes.Page) == false) {
				return null;
			}
			if (item.GetAttribute(Constants.DestinationAttributes.Page).TryParse(out p)) {
				if (IsAbsolute) {
					if (p == Amount) {
						return null;
					}
					p = Amount;
				}
				else {
					p += Amount;
				}
				if (p < 1) {
					return null;
				}
				return UndoAttributeAction.GetUndoAction(item, Constants.DestinationAttributes.Page, p.ToText());
			}
			else {
				var undo = new UndoActionGroup();
				undo.SetAttribute(item, Constants.DestinationAttributes.Page, Amount.ToText());
				if (String.IsNullOrEmpty(a)) {
					undo.SetAttribute(item, Constants.DestinationAttributes.Action, Constants.ActionType.Goto);
				}
				return undo;
			}
		}

		#endregion
	}
}