// NAnt - A .NET build tool
// Copyright (C) 2001-2003 Gerry Shaw
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
//
// Jaroslaw Kowalski (jkowalski@users.sourceforge.net)

using System;
using System.IO;
using System.Text;
using System.Globalization;
using NAnt.Core.Util;

namespace NAnt.Core {

    /// <summary>
    /// Splits an input string into a sequence of tokens used during parsing.
    /// </summary>
    public class ExpressionTokenizer {

        public struct Position {
            private int _charIndex;

            public Position(int charIndex) {
                _charIndex = charIndex;
            }

            public int CharIndex {
                get { return _charIndex; }
            }
        }

        /// <summary>
        /// Available tokens
        /// </summary>
        public enum TokenType {
            BOF,
            EOF,
            Number,
            String,
            Keyword,
            EQ,
            NE,
            LT,
            GT,
            LE,
            GE,
            Plus,
            Minus,
            Mul,
            Div,
            Mod,
            LeftParen,
            RightParen,
            LeftCurlyBrace,
            RightCurlyBrace,
            Not,
            Punctuation,
            Whitespace,
            Dollar,
            Comma,
            Dot,
            DoubleColon,
        }

        #region Public Instance Constructors

        public ExpressionTokenizer() {
        }

        #endregion Public Instance Constructors

        #region Static Constructor

        static ExpressionTokenizer() {
            for (int i = 0; i < 128; ++i) {
                charIndexToTokenType[i] = TokenType.Punctuation;
            };

            foreach (CharToTokenType cht in charToTokenType) {
                charIndexToTokenType[(int)cht.ch] = cht.tokenType;
            }
        }

        #endregion Static Constructor

        #region Public Instance Properties

        public bool IgnoreWhitespace {
            get { return _ignoreWhiteSpace; }
            set { _ignoreWhiteSpace = value; }
        }

        public bool SingleCharacterMode {
            get { return _singleCharacterMode; }
            set { _singleCharacterMode = value; }
        }

        public TokenType CurrentToken {
            get { return _tokenType; }
        }

        public string TokenText {
            get { return _tokenText; }
        }

        public Position CurrentPosition {
            get { return _tokenStartPosition; }
        }

        #endregion Public Instance Properties

        #region Public Instance Methods

        public void InitTokenizer(string s) {
            _text = s;
            _position = 0;
            _tokenType = TokenType.BOF;

            GetNextToken();
        }

        public void GetNextToken() {
            if (_tokenType == TokenType.EOF)
                throw new ExpressionParseException(ResourceUtils.GetString("String_CannotReadPastStream"), -1, -1);

            if (IgnoreWhitespace) {
                SkipWhitespace();
            };

            _tokenStartPosition = new Position(_position);

            int i = PeekChar();
            if (i == -1) {
                _tokenType = TokenType.EOF;
                return ;
            }

            char ch = (char)i;

            if (!SingleCharacterMode) {
                if (!IgnoreWhitespace && Char.IsWhiteSpace(ch)) {
                    StringBuilder sb = new StringBuilder();
                    int ch2;

                    while ((ch2 = PeekChar()) != -1) {
                        if (!Char.IsWhiteSpace((char)ch2)) {
                            break;
                        }

                        sb.Append((char)ch2);
                        ReadChar();
                    };

                    _tokenType = TokenType.Whitespace;
                    _tokenText = sb.ToString();
                    return ;
                }

                if (Char.IsDigit(ch)) {
                    _tokenType = TokenType.Number;
                    string s = "";

                    s += ch;
                    ReadChar();

                    while ((i = PeekChar()) != -1) {
                        ch = (char)i;

                        if (Char.IsDigit(ch)) {
                            s += (char)ReadChar();
                        } else {
                            break;
                        };
                    };

                    _tokenText = s;
                    return ;
                }

                if (ch == '\'') {
                    _tokenType = TokenType.String;

                    string s = "";
                    ReadChar();
                    while ((i = ReadChar()) != -1) {
                        ch = (char)i;

                        if (ch == '\'') {
                            if (PeekChar() == (int)'\'') {
                                ReadChar();
                            } else
                                break;
                        }
                        s += ch;
                    };

                    _tokenText = s;
                    return ;
                }

                if (ch == '_' || Char.IsLetter(ch)) {
                    _tokenType = TokenType.Keyword;

                    StringBuilder sb = new StringBuilder();

                    sb.Append((char)ch);

                    ReadChar();

                    while ((i = PeekChar()) != -1) {
                        if ((char)i == '_' || (char)i == '-' || Char.IsLetterOrDigit((char)i)) {
                            sb.Append((char)ReadChar());
                        } else {
                            break;
                        };
                    };

                    _tokenText = sb.ToString();
                    if (_tokenText.EndsWith("-"))
                        throw new ExpressionParseException(String.Format(CultureInfo.InvariantCulture, 
							ResourceUtils.GetString("NA1182"), _tokenText), CurrentPosition.CharIndex);
                    return ;
                }

                ReadChar();

                if (ch == ':' && PeekChar() == (int)':') {
                    _tokenType = TokenType.DoubleColon;
                    _tokenText = "::";
                    ReadChar();
                    return ;
                }

                if (ch == '!' && PeekChar() == (int)'=') {
                    _tokenType = TokenType.NE;
                    _tokenText = "!=";
                    ReadChar();
                    return ;
                }

                if (ch == '=' && PeekChar() == (int)'=') {
                    _tokenType = TokenType.EQ;
                    _tokenText = "==";
                    ReadChar();
                    return ;
                }

                if (ch == '<' && PeekChar() == (int)'=') {
                    _tokenType = TokenType.LE;
                    _tokenText = "<=";
                    ReadChar();
                    return ;
                }

                if (ch == '>' && PeekChar() == (int)'=') {
                    _tokenType = TokenType.GE;
                    _tokenText = ">=";
                    ReadChar();
                    return ;
                }
            } else {
                ReadChar();
            }
            _tokenText = new String(ch, 1);
            _tokenType = TokenType.Punctuation;
            if (ch >= 32 && ch < 128) {
                _tokenType = charIndexToTokenType[ch];
            }
        }

        public bool IsKeyword(string k) {
            return (_tokenType == TokenType.Keyword) && (_tokenText == k);
        }

        #endregion Public Instance Methods

        #region Private Instance Methods

        private int ReadChar() {
            if (_position < _text.Length) {
                return _text[_position++];
            } else {
                return -1;
            }
        }

        private int PeekChar() {
            if (_position < _text.Length) {
                return _text[_position];
            } else {
                return -1;
            }
        }

        private void SkipWhitespace() {
            int ch;

            while ((ch = PeekChar()) != -1) {
                if (!Char.IsWhiteSpace((char)ch))
                    break;
                ReadChar();
            };
        }

        #endregion Private Instance Methods

        #region Private Instance Fields

        private string _text = null;
        private int _position;
        private Position _tokenStartPosition;
        private TokenType _tokenType;
        private string _tokenText;
        private bool _ignoreWhiteSpace = true;
        private bool _singleCharacterMode = false;

        #endregion Private Instance Fields

        #region Private Static Fields

        private static CharToTokenType[] charToTokenType = {
            new CharToTokenType('+', TokenType.Plus),
            new CharToTokenType('-', TokenType.Minus),
            new CharToTokenType('*', TokenType.Mul),
            new CharToTokenType('/', TokenType.Div),
            new CharToTokenType('%', TokenType.Mod),
            new CharToTokenType('<', TokenType.LT),
            new CharToTokenType('>', TokenType.GT),
            new CharToTokenType('(', TokenType.LeftParen),
            new CharToTokenType(')', TokenType.RightParen),
            new CharToTokenType('{', TokenType.LeftCurlyBrace),
            new CharToTokenType('}', TokenType.RightCurlyBrace),
            new CharToTokenType('!', TokenType.Not),
            new CharToTokenType('$', TokenType.Dollar),
            new CharToTokenType(',', TokenType.Comma),
            new CharToTokenType('.', TokenType.Dot),
        };

        private static TokenType[] charIndexToTokenType = new TokenType[128];

        #endregion Private Static Fields

        private struct CharToTokenType {
            public readonly char ch;
            public readonly TokenType tokenType;

            public CharToTokenType(char ch, TokenType tokenType) {
                this.ch = ch;
                this.tokenType = tokenType;
            }
        }
    }
}