DiffViewLines.cs

namespace Menees.Diffs.Windows.Forms
{
	#region Using Directives

	using System;
	using System.Collections.Generic;
	using System.Collections.ObjectModel;
	using System.Diagnostics;
	using System.Drawing;

	#endregion

	internal sealed class DiffViewLines : ReadOnlyCollection<DiffViewLine>
	{
		#region Private Data Members

		private readonly int[] diffEndLines;
		private readonly int[] diffStartLines;
		private int maxLineNumber = 1;

		#endregion

		#region Constructors

		public DiffViewLines(IList<string> stringList, EditScript script, bool useA)
			: this()
		{
			int currentLine = 0;

			int totalEdits = script.Count;
			this.diffStartLines = new int[totalEdits];
			this.diffEndLines = new int[totalEdits];

			for (int e = 0; e < totalEdits; e++)
			{
				Edit edit = script[e];

				// Get the starting line for this Edit
				int startingLine;
				bool dummyLine;
				if (useA)
				{
					dummyLine = edit.EditType == EditType.Insert;
					startingLine = edit.StartA;
				}
				else
				{
					dummyLine = edit.EditType == EditType.Delete;
					startingLine = edit.StartB;
				}

				// Put in unedited lines up to this point
				currentLine += this.AddUneditedLines(stringList, currentLine, startingLine, useA);

				// Record where the next diff starts and ends
				this.diffStartLines[e] = this.Count;
				this.diffEndLines[e] = this.Count + edit.Length - 1;

				// Since Inserts occur after the current line
				// instead of at it, we have to decrement the index.
				for (int i = 0; i < edit.Length; i++)
				{
					// A - Shows Deletes and Changes
					// B - Shows Inserts and Changes
					string text = string.Empty;
					int? number = null;
					if (!dummyLine)
					{
						number = startingLine + i;
						text = stringList[number.Value];
						currentLine++;
					}

					this.AddLine(text, number, edit.EditType, useA);
				}
			}

			// Put in any remaining unedited lines
			this.AddUneditedLines(stringList, currentLine, stringList.Count, useA);
		}

		public DiffViewLines(DiffViewLine lineOne, DiffViewLine lineTwo)
			: this()
		{
			this.AddLine(lineOne);
			this.AddLine(lineTwo);
		}

		private DiffViewLines()
			: base(new List<DiffViewLine>())
		{
			// Called by the other constructors.
			this.diffStartLines = CollectionUtility.EmptyArray<int>();
			this.diffEndLines = CollectionUtility.EmptyArray<int>();
		}

		#endregion

		#region Public Properties

		public int[] DiffEndLines => this.diffEndLines;

		public int[] DiffStartLines => this.diffStartLines;

		public int MaxLineNumber => this.maxLineNumber;

		#endregion

		#region Private Methods

		private void AddLine(string text, int? number, EditType editType, bool fromA)
		{
			this.AddLine(new DiffViewLine(text, number, editType, fromA));
		}

		private void AddLine(DiffViewLine line)
		{
			if (line.Number.HasValue && line.Number.Value > this.maxLineNumber)
			{
				this.maxLineNumber = line.Number.Value;
			}

			this.Items.Add(line);
		}

		private int AddUneditedLines(IList<string> stringList, int current, int end, bool fromA)
		{
			for (int i = current; i < end; i++)
			{
				this.AddLine(stringList[i], i, EditType.None, fromA);
			}

			// If the edit script isn't using changes (i.e., just inserts and deletes)
			// then we can hit cases where iEnd < iCurrent, but we don't want to
			// return a negative value for number of added lines.
			int result = Math.Max(end - current, 0);
			return result;
		}

		#endregion
	}
}