/* 
 * C# port of Mozilla Character Set Detector
 * 
 * Original Mozilla License Block follows
 * 
 */

#region License Block
// Version: MPL 1.1/GPL 2.0/LGPL 2.1
//
// The contents of this file are subject to the Mozilla Public License Version
// 1.1 (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.mozilla.org/MPL/
//
// Software distributed under the License is distributed on an "AS IS" basis,
// WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
// for the specific language governing rights and limitations under the
// License.
//
// The Original Code is Mozilla Universal charset detector code.
//
// The Initial Developer of the Original Code is
// Netscape Communications Corporation.
// Portions created by the Initial Developer are Copyright (C) 2001
// the Initial Developer. All Rights Reserved.
//
// Contributor(s):
//          Shy Shalom <shooshX@gmail.com>
//
// Alternatively, the contents of this file may be used under the terms of
// either the GNU General Public License Version 2 or later (the "GPL"), or
// the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
// in which case the provisions of the GPL or the LGPL are applicable instead
// of those above. If you wish to allow use of your version of this file only
// under the terms of either the GPL or the LGPL, and not to allow others to
// use your version of this file under the terms of the MPL, indicate your
// decision by deleting the provisions above and replace them with the notice
// and other provisions required by the GPL or the LGPL. If you do not delete
// the provisions above, a recipient may use your version of this file under
// the terms of any one of the MPL, the GPL or the LGPL.
#endregion

using System;

namespace Mozilla.CharDet
{
    class Latin1Prober : AbstractCSProber
    {
        const int FREQ_CAT_NUM = 4;

        public Latin1Prober() { Reset(); }

        public override ProbingState HandleData(byte[] aBuf)
        {
            return HandleData(aBuf, aBuf.Length);
        }

        public override ProbingState HandleData(byte[] aBuf, int length)
        {
            byte[] newBuf1 = new byte[aBuf.Length];
            int newLen1 = 0;

            newLen1 = FilterWithEnglishLetters(aBuf, newBuf1);

            byte charClass;
            byte freq;
            for (int i = 0; i < newLen1; i++)
            {
                charClass = Latin1_CharToClass[(byte)newBuf1[i]];
                freq = Latin1ClassModel[mLastCharClass * CLASS_NUM + charClass];
                if (freq == 0)
                {
                    mState = ProbingState.NotMe;
                    break;
                }
                mFreqCounter[freq]++;
                mLastCharClass = charClass;
            }

            if (newBuf1 != aBuf)
                newBuf1 = null;

            return mState;
        }

        public override void Reset()
        {
            mState = ProbingState.Detecting;
            mLastCharClass = OTH;
            for (int i = 0; i < FREQ_CAT_NUM; i++)
                mFreqCounter[i] = 0;
            active = true;
        }

        public override string CharSetName { get { return "windows-1252"; } }

        public override ProbingState State { get { return mState; } }

        public override float GetConfidence()
        {
            if (mState == ProbingState.NotMe)
                return 0.01f;

            float confidence;
            int total = 0;
            for (int i = 0; i < FREQ_CAT_NUM; i++)
                total += mFreqCounter[i];

            if (total == 0)
                confidence = 0.0f;
            else
            {
                confidence = mFreqCounter[3] * 1.0f / total;
                confidence -= mFreqCounter[1] * 20.0f / total;
            }

            if (confidence < 0.0f)
                confidence = 0.0f;

            // lower the confidence of latin1 so that other more accurate detector 
            // can take priority.
            confidence *= 0.50f;

            return confidence;
        }
        public override void SetOpion() { }

        public override bool IsActive
        {
            get { return active; }
            set { active = value; }
        }


        protected ProbingState mState;
        protected byte mLastCharClass;
        protected int[] mFreqCounter = new int[FREQ_CAT_NUM];
        protected bool active;


        const byte UDF = 0;        // undefined
        const byte OTH = 1;        // other
        const byte ASC = 2;        // ascii capital letter
        const byte ASS = 3;        // ascii small letter
        const byte ACV = 4;        // accent capital vowel
        const byte ACO = 5;        // accent capital other
        const byte ASV = 6;        // accent small vowel
        const byte ASO = 7;        // accent small other
        const byte CLASS_NUM = 8;  // total classes

        static readonly byte[] Latin1_CharToClass = new byte[] {
            OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   // 00 - 07
            OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   // 08 - 0F
            OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   // 10 - 17
            OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   // 18 - 1F
            OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   // 20 - 27
            OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   // 28 - 2F
            OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   // 30 - 37
            OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   // 38 - 3F
            OTH, ASC, ASC, ASC, ASC, ASC, ASC, ASC,   // 40 - 47
            ASC, ASC, ASC, ASC, ASC, ASC, ASC, ASC,   // 48 - 4F
            ASC, ASC, ASC, ASC, ASC, ASC, ASC, ASC,   // 50 - 57
            ASC, ASC, ASC, OTH, OTH, OTH, OTH, OTH,   // 58 - 5F
            OTH, ASS, ASS, ASS, ASS, ASS, ASS, ASS,   // 60 - 67
            ASS, ASS, ASS, ASS, ASS, ASS, ASS, ASS,   // 68 - 6F
            ASS, ASS, ASS, ASS, ASS, ASS, ASS, ASS,   // 70 - 77
            ASS, ASS, ASS, OTH, OTH, OTH, OTH, OTH,   // 78 - 7F
            OTH, UDF, OTH, ASO, OTH, OTH, OTH, OTH,   // 80 - 87
            OTH, OTH, ACO, OTH, ACO, UDF, ACO, UDF,   // 88 - 8F
            UDF, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   // 90 - 97
            OTH, OTH, ASO, OTH, ASO, UDF, ASO, ACO,   // 98 - 9F
            OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   // A0 - A7
            OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   // A8 - AF
            OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   // B0 - B7
            OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH,   // B8 - BF
            ACV, ACV, ACV, ACV, ACV, ACV, ACO, ACO,   // C0 - C7
            ACV, ACV, ACV, ACV, ACV, ACV, ACV, ACV,   // C8 - CF
            ACO, ACO, ACV, ACV, ACV, ACV, ACV, OTH,   // D0 - D7
            ACV, ACV, ACV, ACV, ACV, ACO, ACO, ACO,   // D8 - DF
            ASV, ASV, ASV, ASV, ASV, ASV, ASO, ASO,   // E0 - E7
            ASV, ASV, ASV, ASV, ASV, ASV, ASV, ASV,   // E8 - EF
            ASO, ASO, ASV, ASV, ASV, ASV, ASV, OTH,   // F0 - F7
            ASV, ASV, ASV, ASV, ASV, ASO, ASO, ASO,   // F8 - FF
        };

        /*  0 : illegal 
            1 : very unlikely 
            2 : normal 
            3 : very likely
         */
        static readonly byte[] Latin1ClassModel = new byte[] {
            /*      UDF OTH ASC ASS ACV ACO ASV ASO  */
            /*UDF*/  0,  0,  0,  0,  0,  0,  0,  0,
            /*OTH*/  0,  3,  3,  3,  3,  3,  3,  3,
            /*ASC*/  0,  3,  3,  3,  3,  3,  3,  3, 
            /*ASS*/  0,  3,  3,  3,  1,  1,  3,  3,
            /*ACV*/  0,  3,  3,  3,  1,  2,  1,  2,
            /*ACO*/  0,  3,  3,  3,  3,  3,  3,  3, 
            /*ASV*/  0,  3,  1,  3,  1,  1,  1,  3, 
            /*ASO*/  0,  3,  1,  3,  1,  1,  3,  3,
        };
    }
}
