using Lucene.Net.Analysis.TokenAttributes;
using Lucene.Net.Store;
using Lucene.Net.Util;
using Lucene.Net.Util.Fst;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using JCG = J2N.Collections.Generic;

namespace Lucene.Net.Analysis.Synonym
{
    /*
     * 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.
     */

    /// <summary>
    /// A map of synonyms, keys and values are phrases.
    /// @lucene.experimental
    /// </summary>
    public class SynonymMap
    {
        /// <summary>
        /// for multiword support, you must separate words with this separator </summary>
        public const char WORD_SEPARATOR = (char)0;
        /// <summary>
        /// map&lt;input word, list&lt;ord&gt;&gt; </summary>
        public FST<BytesRef> Fst => fst;

        private readonly FST<BytesRef> fst;

        /// <summary>
        /// map&lt;ord, outputword&gt; </summary>
        public BytesRefHash Words => words;

        private readonly BytesRefHash words;

        /// <summary>
        /// maxHorizontalContext: maximum context we need on the tokenstream </summary>
        public int MaxHorizontalContext => maxHorizontalContext;

        private readonly int maxHorizontalContext;

        public SynonymMap(FST<BytesRef> fst, BytesRefHash words, int maxHorizontalContext)
        {
            this.fst = fst;
            this.words = words;
            this.maxHorizontalContext = maxHorizontalContext;
        }

        /// <summary>
        /// Builds an FSTSynonymMap.
        /// <para>
        /// Call <see cref="Add(CharsRef, CharsRef, bool)"/> until you have added all the mappings, then call <see cref="Build"/> to get an FSTSynonymMap
        /// @lucene.experimental
        /// </para>
        /// </summary>
        public class Builder
        {
            internal readonly IDictionary<CharsRef, MapEntry> workingSet = new JCG.Dictionary<CharsRef, MapEntry>();
            internal readonly BytesRefHash words = new BytesRefHash();
            internal readonly BytesRef utf8Scratch = new BytesRef(8);
            internal int maxHorizontalContext;
            internal readonly bool dedup;

            /// <summary>
            /// If dedup is true then identical rules (same input,
            ///  same output) will be added only once. 
            /// </summary>
            public Builder(bool dedup)
            {
                this.dedup = dedup;
            }

            internal class MapEntry
            {
                internal bool includeOrig;
                // we could sort for better sharing ultimately, but it could confuse people
                internal List<int> ords = new List<int>();
            }

            /// <summary>
            /// Sugar: just joins the provided terms with 
            /// <see cref="SynonymMap.WORD_SEPARATOR"/>. reuse and its chars
            /// must not be null. 
            /// </summary>
            public static CharsRef Join(string[] words, CharsRef reuse)
            {
                int upto = 0;
                char[] buffer = reuse.Chars;
                foreach (string word in words)
                {
                    int wordLen = word.Length;
                    int needed = (0 == upto ? wordLen : 1 + upto + wordLen); // Add 1 for WORD_SEPARATOR
                    if (needed > buffer.Length)
                    {
                        reuse.Grow(needed);
                        buffer = reuse.Chars;
                    }
                    if (upto > 0)
                    {
                        buffer[upto++] = SynonymMap.WORD_SEPARATOR;
                    }

                    word.CopyTo(0, buffer, upto, wordLen - 0);
                    upto += wordLen;
                }
                reuse.Length = upto;
                return reuse;
            }

            /// <summary>
            /// only used for asserting!
            /// </summary>
            internal virtual bool HasHoles(CharsRef chars)
            {
                int end = chars.Offset + chars.Length;
                for (int idx = chars.Offset + 1; idx < end; idx++)
                {
                    if (chars.Chars[idx] == SynonymMap.WORD_SEPARATOR && chars.Chars[idx - 1] == SynonymMap.WORD_SEPARATOR)
                    {
                        return true;
                    }
                }
                if (chars.Chars[chars.Offset] == '\u0000')
                {
                    return true;
                }
                if (chars.Chars[chars.Offset + chars.Length - 1] == '\u0000')
                {
                    return true;
                }

                return false;
            }

            // NOTE: while it's tempting to make this public, since
            // caller's parser likely knows the
            // numInput/numOutputWords, sneaky exceptions, much later
            // on, will result if these values are wrong; so we always
            // recompute ourselves to be safe:
            internal virtual void Add(CharsRef input, int numInputWords, CharsRef output, int numOutputWords, bool includeOrig)
            {
                // first convert to UTF-8
                if (numInputWords <= 0)
                {
                    throw new ArgumentException("numInputWords must be > 0 (got " + numInputWords + ")");
                }
                if (input.Length <= 0)
                {
                    throw new ArgumentException("input.length must be > 0 (got " + input.Length + ")");
                }
                if (numOutputWords <= 0)
                {
                    throw new ArgumentException("numOutputWords must be > 0 (got " + numOutputWords + ")");
                }
                if (output.Length <= 0)
                {
                    throw new ArgumentException("output.length must be > 0 (got " + output.Length + ")");
                }

                Debug.Assert(!HasHoles(input), "input has holes: " + input);
                Debug.Assert(!HasHoles(output), "output has holes: " + output);

                //System.out.println("fmap.add input=" + input + " numInputWords=" + numInputWords + " output=" + output + " numOutputWords=" + numOutputWords);
                UnicodeUtil.UTF16toUTF8(output.Chars, output.Offset, output.Length, utf8Scratch);
                // lookup in hash
                int ord = words.Add(utf8Scratch);
                if (ord < 0)
                {
                    // already exists in our hash
                    ord = (-ord) - 1;
                    //System.out.println("  output=" + output + " old ord=" + ord);
                }
                else
                {
                    //System.out.println("  output=" + output + " new ord=" + ord);
                }

                if (!workingSet.TryGetValue(input, out MapEntry e) || e == null)
                {
                    e = new MapEntry();
                    workingSet[CharsRef.DeepCopyOf(input)] = e; // make a copy, since we will keep around in our map
                }

                e.ords.Add(ord);
                e.includeOrig |= includeOrig;
                maxHorizontalContext = Math.Max(maxHorizontalContext, numInputWords);
                maxHorizontalContext = Math.Max(maxHorizontalContext, numOutputWords);
            }

            internal virtual int CountWords(CharsRef chars)
            {
                int wordCount = 1;
                int upto = chars.Offset;
                int limit = chars.Offset + chars.Length;
                while (upto < limit)
                {
                    if (chars.Chars[upto++] == SynonymMap.WORD_SEPARATOR)
                    {
                        wordCount++;
                    }
                }
                return wordCount;
            }

            /// <summary>
            /// Add a phrase->phrase synonym mapping.
            /// Phrases are character sequences where words are
            /// separated with character zero (U+0000).  Empty words
            /// (two U+0000s in a row) are not allowed in the input nor
            /// the output!
            /// </summary>
            /// <param name="input"> input phrase </param>
            /// <param name="output"> output phrase </param>
            /// <param name="includeOrig"> true if the original should be included </param>
            public virtual void Add(CharsRef input, CharsRef output, bool includeOrig)
            {
                Add(input, CountWords(input), output, CountWords(output), includeOrig);
            }

            /// <summary>
            /// Builds an <see cref="SynonymMap"/> and returns it.
            /// </summary>
            public virtual SynonymMap Build()
            {
                ByteSequenceOutputs outputs = ByteSequenceOutputs.Singleton;
                // TODO: are we using the best sharing options?
                var builder = new Builder<BytesRef>(FST.INPUT_TYPE.BYTE4, outputs);

                BytesRef scratch = new BytesRef(64);
                ByteArrayDataOutput scratchOutput = new ByteArrayDataOutput();

                ISet<int?> dedupSet;

                if (dedup)
                {
                    dedupSet = new JCG.HashSet<int?>();
                }
                else
                {
                    dedupSet = null;
                }


                var spare = new byte[5];

                ICollection<CharsRef> keys = workingSet.Keys;
                CharsRef[] sortedKeys = new CharsRef[keys.Count];
                keys.CopyTo(sortedKeys, 0);
#pragma warning disable 612, 618
                System.Array.Sort(sortedKeys, CharsRef.UTF16SortedAsUTF8Comparer);
#pragma warning restore 612, 618


                Int32sRef scratchIntsRef = new Int32sRef();

                //System.out.println("fmap.build");
                for (int keyIdx = 0; keyIdx < sortedKeys.Length; keyIdx++)
                {
                    CharsRef input = sortedKeys[keyIdx];
                    MapEntry output = workingSet[input];

                    int numEntries = output.ords.Count;
                    // output size, assume the worst case
                    int estimatedSize = 5 + numEntries * 5; // numEntries + one ord for each entry

                    scratch.Grow(estimatedSize);
                    scratchOutput.Reset(scratch.Bytes, scratch.Offset, scratch.Bytes.Length);
                    Debug.Assert(scratch.Offset == 0);

                    // now write our output data:
                    int count = 0;
                    for (int i = 0; i < numEntries; i++)
                    {
                        if (dedupSet != null)
                        {
                            // box once
                            int? ent = output.ords[i];
                            if (dedupSet.Contains(ent))
                            {
                                continue;
                            }
                            dedupSet.Add(ent);
                        }
                        scratchOutput.WriteVInt32(output.ords[i]);
                        count++;
                    }

                    int pos = scratchOutput.Position;
                    scratchOutput.WriteVInt32(count << 1 | (output.includeOrig ? 0 : 1));
                    int pos2 = scratchOutput.Position;
                    int vIntLen = pos2 - pos;

                    // Move the count + includeOrig to the front of the byte[]:
                    Array.Copy(scratch.Bytes, pos, spare, 0, vIntLen);
                    Array.Copy(scratch.Bytes, 0, scratch.Bytes, vIntLen, pos);
                    Array.Copy(spare, 0, scratch.Bytes, 0, vIntLen);

                    if (dedupSet != null)
                    {
                        dedupSet.Clear();
                    }

                    scratch.Length = scratchOutput.Position - scratch.Offset;
                    //System.out.println("  add input=" + input + " output=" + scratch + " offset=" + scratch.offset + " length=" + scratch.length + " count=" + count);
                    builder.Add(Lucene.Net.Util.Fst.Util.ToUTF32(input.ToString(), scratchIntsRef), BytesRef.DeepCopyOf(scratch));
                }

                FST<BytesRef> fst = builder.Finish();
                return new SynonymMap(fst, words, maxHorizontalContext);
            }
        }

        /// <summary>
        /// Abstraction for parsing synonym files.
        /// 
        /// @lucene.experimental
        /// </summary>
        public abstract class Parser : Builder
        {
            private readonly Analyzer analyzer;

            public Parser(bool dedup, Analyzer analyzer) 
                : base(dedup)
            {
                this.analyzer = analyzer;
            }

            /// <summary>
            /// Parse the given input, adding synonyms to the inherited <see cref="Builder"/>. </summary>
            /// <param name="in"> The input to parse </param>
            public abstract void Parse(TextReader @in);

            /// <summary>
            /// Sugar: analyzes the text with the analyzer and
            /// separates by <see cref="SynonymMap.WORD_SEPARATOR"/>.
            /// reuse and its chars must not be null. 
            /// </summary>
            public virtual CharsRef Analyze(string text, CharsRef reuse)
            {
                IOException priorException = null;
                TokenStream ts = analyzer.GetTokenStream("", text);
                try
                {
                    var termAtt = ts.AddAttribute<ICharTermAttribute>();
                    var posIncAtt = ts.AddAttribute<IPositionIncrementAttribute>();
                    ts.Reset();
                    reuse.Length = 0;
                    while (ts.IncrementToken())
                    {
                        int length = termAtt.Length;
                        if (length == 0)
                        {
                            throw new ArgumentException("term: " + text + " analyzed to a zero-length token");
                        }
                        if (posIncAtt.PositionIncrement != 1)
                        {
                            throw new ArgumentException("term: " + text + " analyzed to a token with posinc != 1");
                        }
                        reuse.Grow(reuse.Length + length + 1); // current + word + separator
                        int end = reuse.Offset + reuse.Length;
                        if (reuse.Length > 0)
                        {
                            reuse.Chars[end++] = SynonymMap.WORD_SEPARATOR;
                            reuse.Length++;
                        }
                        Array.Copy(termAtt.Buffer, 0, reuse.Chars, end, length);
                        reuse.Length += length;
                    }
                    ts.End();
                }
                catch (IOException e)
                {
                    priorException = e;
                }
                finally
                {
                    IOUtils.DisposeWhileHandlingException(priorException, ts);
                }
                if (reuse.Length == 0)
                {
                    throw new ArgumentException("term: " + text + " was completely eliminated by analyzer");
                }
                return reuse;
            }
        }
    }
}