/**
 * 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.
 */

using System.Collections.Generic;

using IndexOutput = Lucene.Net.Store.IndexOutput;
using Similarity = Lucene.Net.Search.Similarity;

namespace Lucene.Net.Index
{
    // TODO FI: norms could actually be stored as doc store

    /** Writes norms.  Each thread X field accumulates the norms
     *  for the doc/fields it saw, then the flush method below
     *  merges all of these together into a single _X.nrm file.
     */

    internal sealed class NormsWriter : InvertedDocEndConsumer
    {

        private static readonly byte defaultNorm = Similarity.EncodeNorm(1.0f);

        private FieldInfos fieldInfos;
        
        internal override InvertedDocEndConsumerPerThread addThread(DocInverterPerThread docInverterPerThread)
        {
            return new NormsWriterPerThread(docInverterPerThread, this);
        }

        internal override void abort() { }

        // We only write the _X.nrm file at flush
        internal void files(ICollection<object> files) { }

        internal override void setFieldInfos(FieldInfos fieldInfos)
        {
            this.fieldInfos = fieldInfos;
        }

        /** Produce _X.nrm if any document had a field with norms
         *  not disabled */
        internal override void flush(IDictionary<object, ICollection<object>> threadsAndFields, DocumentsWriter.FlushState state)
        {

            IDictionary<object, object> byField = new Dictionary<object, object>();

            // Typically, each thread will have encountered the same
            // field.  So first we collate by field, ie, all
            // per-thread field instances that correspond to the
            // same FieldInfo
            IEnumerator<KeyValuePair<object, ICollection<object>>> it = threadsAndFields.GetEnumerator();
            while (it.MoveNext())
            {
                KeyValuePair<object, ICollection<object>> entry = it.Current;

                ICollection<object> fields = entry.Value;
                IEnumerator<object> fieldsIt = fields.GetEnumerator();
                List<object> fieldsToRemove = new List<object>(fields.Count);

                while (fieldsIt.MoveNext())
                {
                    NormsWriterPerField perField = (NormsWriterPerField)fieldsIt.Current;

                    if (perField.upto > 0)
                    {
                        // It has some norms
                        IList<object> l;
                        if (byField.ContainsKey(perField.fieldInfo))
                        {
                            l = (IList<object>)byField[perField.fieldInfo];
                        }
                        else
                        {
                            l = new List<object>();
                            byField[perField.fieldInfo] = l;
                        }
                        //IList<object> l = (IList<object>)byField[perField.fieldInfo];
                        //if (l == null)
                        //{
                        //    l = new List<object>();
                        //    byField[perField.fieldInfo] = l;
                        //}
                        l.Add(perField);
                    }
                    else
                    {
                        // Remove this field since we haven't seen it
                        // since the previous flush
                        fieldsToRemove.Add(perField);
                        //fields.Remove(perField);
                    }
                }
                for (int i = 0; i < fieldsToRemove.Count; i++) fields.Remove(fieldsToRemove[i]);
            }

            string normsFileName = state.segmentName + "." + IndexFileNames.NORMS_EXTENSION;
            state.flushedFiles[normsFileName] = normsFileName;
            IndexOutput normsOut = state.directory.CreateOutput(normsFileName);

            try
            {
                normsOut.WriteBytes(SegmentMerger.NORMS_HEADER, 0, SegmentMerger.NORMS_HEADER.Length);

                int numField = fieldInfos.Size();

                int normCount = 0;

                for (int fieldNumber = 0; fieldNumber < numField; fieldNumber++)
                {

                    FieldInfo fieldInfo = fieldInfos.FieldInfo(fieldNumber);

                    List<object> toMerge;
                    int upto = 0;
                    if (byField.ContainsKey(fieldInfo))
                    {
                        toMerge = (List<object>)byField[fieldInfo];

                        int numFields = toMerge.Count;

                        normCount++;

                        NormsWriterPerField[] fields = new NormsWriterPerField[numFields];
                        int[] uptos = new int[numFields];

                        for (int j = 0; j < numFields; j++)
                            fields[j] = (NormsWriterPerField)toMerge[j];

                        int numLeft = numFields;

                        while (numLeft > 0)
                        {

                            System.Diagnostics.Debug.Assert(uptos[0] < fields[0].docIDs.Length, " uptos[0]=" + uptos[0] + " len=" + (fields[0].docIDs.Length));

                            int minLoc = 0;
                            int minDocID = fields[0].docIDs[uptos[0]];

                            for (int j = 1; j < numLeft; j++)
                            {
                                int docID = fields[j].docIDs[uptos[j]];
                                if (docID < minDocID)
                                {
                                    minDocID = docID;
                                    minLoc = j;
                                }
                            }

                            System.Diagnostics.Debug.Assert(minDocID < state.numDocsInRAM);

                            // Fill hole
                            for (; upto < minDocID; upto++)
                                normsOut.WriteByte(defaultNorm);

                            normsOut.WriteByte(fields[minLoc].norms[uptos[minLoc]]);
                            (uptos[minLoc])++;
                            upto++;

                            if (uptos[minLoc] == fields[minLoc].upto)
                            {
                                fields[minLoc].reset();
                                if (minLoc != numLeft - 1)
                                {
                                    fields[minLoc] = fields[numLeft - 1];
                                    uptos[minLoc] = uptos[numLeft - 1];
                                }
                                numLeft--;
                            }
                        }

                        // Fill final hole with defaultNorm
                        for (; upto < state.numDocsInRAM; upto++)
                            normsOut.WriteByte(defaultNorm);
                    }
                    else if (fieldInfo.isIndexed && !fieldInfo.omitNorms)
                    {
                        normCount++;
                        // Fill entire field with default norm:
                        for (; upto < state.numDocsInRAM; upto++)
                            normsOut.WriteByte(defaultNorm);
                    }

                    System.Diagnostics.Debug.Assert(4 + normCount * state.numDocsInRAM == normsOut.GetFilePointer(), ".nrm file size mismatch: expected=" + (4 + normCount * state.numDocsInRAM) + " actual=" + normsOut.GetFilePointer());
                }

            }
            finally
            {
                normsOut.Close();
            }
        }

        internal override void closeDocStore(DocumentsWriter.FlushState state) { }
    }
}