using Lucene.Net.Analysis.Util;

namespace Lucene.Net.Analysis.Fi
{
    /*
     * Licensed to the Apache Software Foundation (ASF) under one or more
     * contributor license agreements.  See the NOTICE file distributed with
     * this work for additional information regarding copyright ownership.
     * The ASF licenses this file to You under the Apache License, Version 2.0
     * (the "License"); you may not use this file except in compliance with
     * the License.  You may obtain a copy of the License at
     *
     *     http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed under the License is distributed on an "AS IS" BASIS,
     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */

    /* 
     * This algorithm is updated based on code located at:
     * http://members.unine.ch/jacques.savoy/clef/
     * 
     * Full copyright for that code follows:
     */

    /*
     * Copyright (c) 2005, Jacques Savoy
     * All rights reserved.
     *
     * Redistribution and use in source and binary forms, with or without 
     * modification, are permitted provided that the following conditions are met:
     *
     * Redistributions of source code must retain the above copyright notice, this 
     * list of conditions and the following disclaimer. Redistributions in binary 
     * form must reproduce the above copyright notice, this list of conditions and
     * the following disclaimer in the documentation and/or other materials 
     * provided with the distribution. Neither the name of the author nor the names 
     * of its contributors may be used to endorse or promote products derived from 
     * this software without specific prior written permission.
     * 
     * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
     * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
     * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE 
     * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
     * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
     * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
     * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
     * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
     * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     * POSSIBILITY OF SUCH DAMAGE.
     */

    /// <summary>
    /// Light Stemmer for Finnish.
    /// <para>
    /// This stemmer implements the algorithm described in:
    /// <c>Report on CLEF-2003 Monolingual Tracks</c>
    /// Jacques Savoy
    /// </para>
    /// </summary>
    public class FinnishLightStemmer
    {
        public virtual int Stem(char[] s, int len)
        {
            if (len < 4)
            {
                return len;
            }

            for (int i = 0; i < len; i++)
            {
                switch (s[i])
                {
                    case 'ä':
                    case 'å':
                        s[i] = 'a';
                        break;
                    case 'ö':
                        s[i] = 'o';
                        break;
                }
            }

            len = Step1(s, len);
            len = Step2(s, len);
            len = Step3(s, len);
            len = Norm1(s, len);
            len = Norm2(s, len);
            return len;
        }

        private int Step1(char[] s, int len)
        {
            if (len > 8)
            {
                if (StemmerUtil.EndsWith(s, len, "kin"))
                {
                    return Step1(s, len - 3);
                }
                if (StemmerUtil.EndsWith(s, len, "ko"))
                {
                    return Step1(s, len - 2);
                }
            }

            if (len > 11)
            {
                if (StemmerUtil.EndsWith(s, len, "dellinen"))
                {
                    return len - 8;
                }
                if (StemmerUtil.EndsWith(s, len, "dellisuus"))
                {
                    return len - 9;
                }
            }
            return len;
        }

        private int Step2(char[] s, int len)
        {
            if (len > 5)
            {
                if (StemmerUtil.EndsWith(s, len, "lla") || StemmerUtil.EndsWith(s, len, "tse") || StemmerUtil.EndsWith(s, len, "sti"))
                {
                    return len - 3;
                }

                if (StemmerUtil.EndsWith(s, len, "ni"))
                {
                    return len - 2;
                }

                if (StemmerUtil.EndsWith(s, len, "aa"))
                {
                    return len - 1; // aa -> a
                }
            }

            return len;
        }

        private int Step3(char[] s, int len)
        {
            if (len > 8)
            {
                if (StemmerUtil.EndsWith(s, len, "nnen"))
                {
                    s[len - 4] = 's';
                    return len - 3;
                }

                if (StemmerUtil.EndsWith(s, len, "ntena"))
                {
                    s[len - 5] = 's';
                    return len - 4;
                }

                if (StemmerUtil.EndsWith(s, len, "tten"))
                {
                    return len - 4;
                }

                if (StemmerUtil.EndsWith(s, len, "eiden"))
                {
                    return len - 5;
                }
            }

            if (len > 6)
            {
                if (StemmerUtil.EndsWith(s, len, "neen") || StemmerUtil.EndsWith(s, len, "niin") || StemmerUtil.EndsWith(s, len, "seen") || StemmerUtil.EndsWith(s, len, "teen") || StemmerUtil.EndsWith(s, len, "inen"))
                {
                    return len - 4;
                }

                if (s[len - 3] == 'h' && IsVowel(s[len - 2]) && s[len - 1] == 'n')
                {
                    return len - 3;
                }

                if (StemmerUtil.EndsWith(s, len, "den"))
                {
                    s[len - 3] = 's';
                    return len - 2;
                }

                if (StemmerUtil.EndsWith(s, len, "ksen"))
                {
                    s[len - 4] = 's';
                    return len - 3;
                }

                if (StemmerUtil.EndsWith(s, len, "ssa") || StemmerUtil.EndsWith(s, len, "sta") || StemmerUtil.EndsWith(s, len, "lla") || StemmerUtil.EndsWith(s, len, "lta") || StemmerUtil.EndsWith(s, len, "tta") || StemmerUtil.EndsWith(s, len, "ksi") || StemmerUtil.EndsWith(s, len, "lle"))
                {
                    return len - 3;
                }
            }

            if (len > 5)
            {
                if (StemmerUtil.EndsWith(s, len, "na") || StemmerUtil.EndsWith(s, len, "ne"))
                {
                    return len - 2;
                }

                if (StemmerUtil.EndsWith(s, len, "nei"))
                {
                    return len - 3;
                }
            }

            if (len > 4)
            {
                if (StemmerUtil.EndsWith(s, len, "ja") || StemmerUtil.EndsWith(s, len, "ta"))
                {
                    return len - 2;
                }

                if (s[len - 1] == 'a')
                {
                    return len - 1;
                }

                if (s[len - 1] == 'n' && IsVowel(s[len - 2]))
                {
                    return len - 2;
                }

                if (s[len - 1] == 'n')
                {
                    return len - 1;
                }
            }

            return len;
        }

        private int Norm1(char[] s, int len)
        {
            if (len > 5 && StemmerUtil.EndsWith(s, len, "hde"))
            {
                s[len - 3] = 'k';
                s[len - 2] = 's';
                s[len - 1] = 'i';
            }

            if (len > 4)
            {
                if (StemmerUtil.EndsWith(s, len, "ei") || StemmerUtil.EndsWith(s, len, "at"))
                {
                    return len - 2;
                }
            }

            if (len > 3)
            {
                switch (s[len - 1])
                {
                    case 't':
                    case 's':
                    case 'j':
                    case 'e':
                    case 'a':
                    case 'i':
                        return len - 1;
                }
            }

            return len;
        }

        private int Norm2(char[] s, int len)
        {
            if (len > 8)
            {
                if (s[len - 1] == 'e' || s[len - 1] == 'o' || s[len - 1] == 'u')
                {
                    len--;
                }
            }

            if (len > 4)
            {
                if (s[len - 1] == 'i')
                {
                    len--;
                }

                if (len > 4)
                {
                    char ch = s[0];
                    for (int i = 1; i < len; i++)
                    {
                        if (s[i] == ch && (ch == 'k' || ch == 'p' || ch == 't'))
                        {
                            len = StemmerUtil.Delete(s, i--, len);
                        }
                        else
                        {
                            ch = s[i];
                        }
                    }
                }
            }

            return len;
        }

        private bool IsVowel(char ch)
        {
            switch (ch)
            {
                case 'a':
                case 'e':
                case 'i':
                case 'o':
                case 'u':
                case 'y':
                    return true;
                default:
                    return false;
            }
        }
    }
}