static public SwapInfo?CreateFrom(DocumentChangeEventArgs e)
{
if (e is null)
{
return(null);
}
if (e.RemovalLength != e.InsertionLength)
{
return(null);
}
if (e.OffsetChangeMap.Count != 2)
{
return(null);
}
var x = e.OffsetChangeMap[1];
var y = e.OffsetChangeMap[0];
if (x.Offset > y.Offset)
{
(x, y) = (y, x);
}
if (x.InsertionLength != y.RemovalLength)
{
return(null);
}
if (y.InsertionLength != x.RemovalLength)
{
return(null);
}
var xOldText = e.RemovedText.Text.Substring(0, x.RemovalLength);
var xNewText = e.InsertedText.Text.Substring(e.InsertionLength - x.RemovalLength);
if (xOldText != xNewText)
{
return(null);
}
var yOldText = e.RemovedText.Text.Substring(e.RemovalLength - y.RemovalLength);
var yNewText = e.InsertedText.Text.Substring(0, y.RemovalLength);
if (yOldText != yNewText)
{
return(null);
}
var xNode = new SwapNode(x.Offset, xNewText);
var yNode = new SwapNode(y.Offset, yNewText);
return(new SwapInfo(xNode, yNode));
}
private SwapInfo(SwapNode lower, SwapNode upper)
{
_lower = lower;
_upper = upper;
}
static public SwapInfo CreateFrom(SwapNode lower, SwapNode upper)
{
return(new SwapInfo(lower, upper));
}
