/// <summary>
/// Gets th edit script of this line in comparison to its <see cref="Counterpart"/>.
/// The change edit script can then be used to color each letter position in the line
/// to indicate how one line can completely match the other using character based
/// change operations (insert, delete, change, none).
///
/// The method should only be invoked on demand (when a line is actually
/// displayed) - we should wait with pulling it until we have to have it for rendering.
///
/// This object will NOT cache the edit script so the caller should implement an external
/// caching algorithm to avoid multiple computations of the same answer.
///
/// Getting all intra-line diffs at once makes the whole process into an O(n^2) operation
/// instead of just an O(n) operation for line-by-line diffs. So we try to defer the
/// extra work until the user requests to see the changed line. It's still
/// the same amount of work if the user views every line, but it makes the
/// user interface more responsive to split it up like this.
/// </summary>
/// <param name="options"></param>
/// <returns></returns>
public EditScript GetChangeEditScript(ChangeDiffOptions options)
{
EditScript _changeEditScript = null;
if ( //_changeEditScript == null &&
_editType == EditType.Change && this.Counterpart != null)
{
if (this.FromA)
{
int trimCountA, trimCountB;
MyersDiff <char> diff = new MyersDiff <char>(
GetCharactersToDiff(this.text, options, out trimCountA),
GetCharactersToDiff(this.Counterpart.text, options, out trimCountB),
false); // We don't want Change edits; just Deletes and Inserts.
_changeEditScript = diff.Execute(null);
// If we trimmed/ignored leading whitespace, we have to offset each Edit to account for that.
foreach (Edit edit in _changeEditScript)
{
edit.Offset(trimCountA, trimCountB);
}
}
else if (this.Counterpart.FromA && this.Counterpart.Counterpart == this)
{
// Defer to the A line because its edit script changes A into B.
_changeEditScript = this.Counterpart.GetChangeEditScript(options);
}
}
return(_changeEditScript);
}
/// <summary>
/// Makes comparison of two collections of string lines
/// </summary>
/// <param name="listA">Lines sequence A</param>
/// <param name="listB">Lines sequence B</param>
/// <returns>Edit script to transform A to B</returns>
public EditScript Execute(IList <string> listA, IList <string> listB)
{
int[] hashA = HashStringList(listA);
int[] hashB = HashStringList(listB);
MyersDiff <int> diff = new MyersDiff <int>(hashA, hashB, _supportChangeEditType);
EditScript result = diff.Execute();
return(result);
}
