using System.Text.RegularExpressions;
using Microsoft.VisualStudio.TextManager.Interop;
namespace BooLangService
{
/// <summary>
/// Checks the current users line and indents or dedents the next one.
/// </summary>
public class LineIndenter
{
// matches comments on the end of a line
private readonly Regex removeCommentsRegExp = new Regex(@".*((?:#|\/\/|\/\*).*)$", RegexOptions.Compiled);
// matches a dedenting code line (pass, return, return xxx, return if x = x, return xxx unless x = x, etc...)
private readonly Regex dedentRegExp = new Regex(@"(?:return|pass)(?:[\t ]?[\w]*[\t ]?(?<exp>(?:if|unless)))?", RegexOptions.Compiled);
private const string Indent = " ";
private readonly BooSource source;
public LineIndenter(BooSource source)
{
this.source = source;
}
/// <summary>
/// Changes the indentation of the current line based on the last
/// bit of code typed.
/// </summary>
/// <param name="changedArea">Area of changed code</param>
public void ChangeIndentation(TextSpan changedArea)
{
TextSpan area = changedArea;
string text = source.GetText(area);
string line = source.GetTextUptoPosition(area.iStartLine, area.iStartIndex);
if (!line.EndsWith(text))
{
// if commit includes last bit of text typed, the line won't have it yet
// so stick it on for our parsing sanity
// ** probably not the best thing to be doing here, but we can't just
// get the whole line, because we may be pressing return in the centre
// of it
line += text;
}
if (RequiresIndent(line))
{
source.SetText(area, text + Indent); // add an indent to the end of the changed text
MoveCaret(Indent.Length); // move the caret to the new end of line
}
else if (RequiresDedent(line))
{
source.SetText(area, text.Remove(text.Length - Indent.Length)); // remove an indent
MoveCaret(-Indent.Length); // move caret in a bit
}
}
/// <summary>
/// Moves the caret a set number of columns.
/// </summary>
/// <remarks>
/// Use negative numbers to move left.
/// </remarks>
/// <param name="amount">Number of columns to move.</param>
private void MoveCaret(int amount)
{
IVsTextView view = source.LanguageService.GetPrimaryViewForSource(source);
int caretLine = 0;
int caretCol = 0;
view.GetCaretPos(out caretLine, out caretCol);
view.SetCaretPos(caretLine, caretCol + amount);
}
/// <summary>
/// Determines whether the current line should have the newline indented.
/// </summary>
/// <param name="line">Current line</param>
/// <returns>Whether newline line should be indented</returns>
private bool RequiresIndent(string line)
{
line = PrepareLine(line); // cheat and make parsing easier
return line.EndsWith(":");
}
private bool RequiresDedent(string line)
{
line = PrepareLine(line); // cheat and make parsing easier
Match dedentMatch = dedentRegExp.Match(line);
// my regex foo is not strong enough to do this in one, so match
// a dedent line (i.e. return) but then check if it ends with an
// expression (i.e. return "value" if x = 10). Only indent if
// there isn't an expression
if (dedentMatch.Success && !dedentMatch.Groups["exp"].Success)
return true;
return false;
}
private string PrepareLine(string line)
{
// remove comments, makes parsing easier
Match commentMatch = removeCommentsRegExp.Match(line);
if (commentMatch != null && commentMatch.Groups.Count >= 2)
line = line.Remove(line.IndexOf(commentMatch.Groups[1].Value));
// get rid of trailing whitespace
line = line.TrimEnd();
return line;
}
}
}
