//
// IWordFindStrategy.cs
//
// Author:
//   Mike Krüger <mkrueger@novell.com>
//
// Copyright (C) 2008 Novell, Inc (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
// 
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

using System;

namespace Mono.TextEditor
{
	public interface IWordFindStrategy
	{
		int FindNextWordOffset (Document doc, int offset);
		int FindPrevWordOffset (Document doc, int offset);
		int FindNextSubwordOffset (Document doc, int offset);
		int FindPrevSubwordOffset (Document doc, int offset);
		int FindCurrentWordStart (Document doc, int offset);
		int FindCurrentWordEnd (Document doc, int offset);
	}
	
	public abstract class WordFindStrategy : IWordFindStrategy
	{
		public enum CharacterClass {
			Unknown,
			Whitespace,
			IdentifierPart,
			UppercaseLetter,
			LowercaseLetter,
			Digit
		}
		
		public static CharacterClass GetCharacterClass (char ch)
		{
			return GetCharacterClass (ch, false, false);
		}
		
		public static CharacterClass GetCharacterClass (char ch, bool subword, bool treat_)
		{
			if (Char.IsWhiteSpace (ch))
				return CharacterClass.Whitespace;
			if (Char.IsDigit (ch))
				return subword? CharacterClass.Digit : CharacterClass.IdentifierPart;
			if (Char.IsLetter (ch)) {
				if (!subword)
					return CharacterClass.IdentifierPart;
				else if (Char.IsUpper (ch))
					return CharacterClass.UppercaseLetter;
				else
					return CharacterClass.LowercaseLetter;
			}
			if (!subword && treat_ && ch == '_')
 				return CharacterClass.IdentifierPart;
 			return CharacterClass.Unknown;
 		}
		
		public abstract int FindNextWordOffset (Document doc, int offset);
		public abstract int FindPrevWordOffset (Document doc, int offset);
		
		public virtual int FindNextSubwordOffset (Document doc, int offset)
		{
			return FindNextWordOffset (doc, offset);
		}
		
		public virtual int FindPrevSubwordOffset (Document doc, int offset)
		{
			return FindPrevWordOffset (doc, offset);
		}
		
		public virtual int FindCurrentWordStart (Document doc, int offset)
		{
			return ScanWord (doc, offset, false);
		}
		
		public virtual int FindCurrentWordEnd (Document doc, int offset)
		{
			return ScanWord (doc, offset, true);
		}
		
		internal static int ScanWord (Document doc, int offset, bool forwardDirection)
		{
			if (offset < 0 || offset >= doc.Length)
				return offset;
			var line = doc.GetLineByOffset (offset);
			char first = doc.GetCharAt (offset);

			while (offset >= line.Offset && offset < line.Offset + line.EditableLength) {
				char ch = doc.GetCharAt (offset);
				if (char.IsWhiteSpace (first) && !char.IsWhiteSpace (ch)
				    || IsNoLetterOrDigit (first) && !IsNoLetterOrDigit (ch)
				    || (char.IsLetterOrDigit (first) || first == '_') && !(char.IsLetterOrDigit (ch) || ch == '_'))
					break;

				offset = forwardDirection ? offset + 1 : offset - 1;
			}
			return System.Math.Min (line.Offset + line.EditableLength,
			                        System.Math.Max (line.Offset, offset + (forwardDirection ? 0 : 1)));
		}
		
		static bool IsNoLetterOrDigit (char ch)
		{
			return !char.IsWhiteSpace (ch) && !char.IsLetterOrDigit (ch);
		}
	}
}
