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 : ILineIndenter
{
// 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 readonly ISource source;
private readonly IVsTextView view;
private readonly char IndentChar;
public LineIndenter(ISource source, IVsTextView view)
{
this.source = source;
this.view = view;
IndentChar = source.UseTabs ? '\t' : ' ';
}
/// <summary>
/// Sets the indentation for the next lineNumber.
/// </summary>
public void SetIndentationForNextLine(int lineNumber)
{
string previousLine = GetPreviousNonWhitespaceLine(lineNumber);
int indentLevel = GetIndentLevel(previousLine);
if (RequiresIndent(previousLine))
indentLevel++;
else if (RequiresDedent(previousLine) && indentLevel > 0)
indentLevel--;
var nextLine = "".PadRight(indentLevel, IndentChar);
var firstChar = source.ScanToNonWhitespaceChar(lineNumber);
source.SetText(lineNumber, firstChar, nextLine);
view.PositionCaretForEditing(lineNumber, indentLevel);
}
private int GetIndentLevel(string line)
{
var count = 0;
foreach (var c in line)
{
if (c != IndentChar)
break; // got to the text on the line
count++;
}
return count;
}
private string GetPreviousNonWhitespaceLine(int startLine)
{
int prevLineIndex = startLine - 1;
var lineText = source.GetLine(prevLineIndex);
//searchig for not blank line
while (prevLineIndex > 0 && string.IsNullOrEmpty(lineText))
{
prevLineIndex--;
lineText = source.GetLine(prevLineIndex);
}
return lineText;
}
/// <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;
}
}
}
