using System;

using System.Text;

namespace Microsoft.PowerShell

{

internal static class StringBuilderTextObjectExtensions

{

private const string WhiteSpace = " \n\t";

/// <summary>

/// Returns the position of the beginning of the current word as delimited by white space and delimiters

/// This method differs from <see cref="ViFindPreviousWordPoint(string)"/>:

/// - When the cursor location is on the first character of a word, <see cref="ViFindPreviousWordPoint(string)"/>

/// returns the position of the previous word, whereas this method returns the cursor location.

/// - When the cursor location is in a word, both methods return the same result.

/// This method supports VI "iw" text object.

/// </summary>

public static int ViFindBeginningOfWordObjectBoundary(this StringBuilder buffer, int position, string wordDelimiters)

{

// Cursor may be past the end of the buffer when calling this method

// this may happen if the cursor is at the beginning of a new line.

var i = Math.Min(position, buffer.Length - 1);

// If starting on a word consider a text object as a sequence of characters excluding the delimiters,

// otherwise, consider a word as a sequence of delimiters.

var delimiters = wordDelimiters;

var isInWord = buffer.InWord(i, wordDelimiters);

if (isInWord)

{

// For the purpose of this method, whitespace character is considered a delimiter.

delimiters += WhiteSpace;

}

else

{

char c = buffer[i];

if ((wordDelimiters + '\n').IndexOf(c) == -1 && char.IsWhiteSpace(c))

{

// Current position points to a whitespace that is not a newline.

delimiters = WhiteSpace;

}

else

{

delimiters += '\n';

}

}

var isTextObjectChar = isInWord

? (Func<char, bool>)(c => delimiters.IndexOf(c) == -1)

: c => delimiters.IndexOf(c) != -1;

var beginning = i;

while (i >= 0 && isTextObjectChar(buffer[i]))

{

beginning = i--;

}

return beginning;

}

/// <summary>

/// Finds the position of the beginning of the next word object starting from the specified position.

/// If positioned on the last word in the buffer, returns buffer length + 1.

/// This method supports VI "iw" text-object.

/// iw: "inner word", select words. White space between words is counted too.

/// </summary>

public static int ViFindBeginningOfNextWordObjectBoundary(this StringBuilder buffer, int position, string wordDelimiters)

{

// Cursor may be past the end of the buffer when calling this method

// this may happen if the cursor is at the beginning of a new line.

var i = Math.Min(position, buffer.Length - 1);

// Always skip the first newline character.

if (buffer[i] == '\n' && i < buffer.Length - 1)

{

++i;

}

// If starting on a word consider a text object as a sequence of characters excluding the delimiters,

// otherwise, consider a word as a sequence of delimiters.

var delimiters = wordDelimiters;

var isInWord = buffer.InWord(i, wordDelimiters);

if (isInWord)

{

delimiters += WhiteSpace;

}

else if (char.IsWhiteSpace(buffer[i]))

{

delimiters = " \t";

}

var isTextObjectChar = isInWord

? (Func<char, bool>)(c => delimiters.IndexOf(c) == -1)

: c => delimiters.IndexOf(c) != -1;

// Try to skip a second newline characters to replicate vim behaviour.

if (buffer[i] == '\n' && i < buffer.Length - 1)

{

++i;

}

// Skip to next non-word characters.

while (i < buffer.Length && isTextObjectChar(buffer[i]))

{

++i;

}

// Make sure end includes the starting position.

return Math.Max(i, position);

}

}

}