using Lucene.Net.Documents;
using NUnit.Framework;
using System.Collections.Generic;
using Assert = Lucene.Net.TestFramework.Assert;

namespace Lucene.Net.Index
{
    /*
     * 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 Directory = Lucene.Net.Store.Directory;
    using DocIdSetIterator = Lucene.Net.Search.DocIdSetIterator;
    using Document = Documents.Document;
    using Field = Field;
    using FixedBitSet = Lucene.Net.Util.FixedBitSet;
    using LuceneTestCase = Lucene.Net.Util.LuceneTestCase;
    using TestUtil = Lucene.Net.Util.TestUtil;

    /// <summary>
    /// Tests the Terms.DocCount statistic
    /// </summary>
    [SuppressCodecs("Lucene3x")]
    [TestFixture]
    public class TestDocCount : LuceneTestCase
    {
        [Test]
        public virtual void TestSimple()
        {
            Directory dir = NewDirectory();
            RandomIndexWriter iw = new RandomIndexWriter(Random, dir);
            int numDocs = AtLeast(100);
            for (int i = 0; i < numDocs; i++)
            {
                iw.AddDocument(Doc());
            }
            IndexReader ir = iw.GetReader();
            VerifyCount(ir);
            ir.Dispose();
            iw.ForceMerge(1);
            ir = iw.GetReader();
            VerifyCount(ir);
            ir.Dispose();
            iw.Dispose();
            dir.Dispose();
        }

        private IEnumerable<IIndexableField> Doc()
        {
            Document doc = new Document();
            int numFields = TestUtil.NextInt32(Random, 1, 10);
            for (int i = 0; i < numFields; i++)
            {
                doc.Add(NewStringField("" + TestUtil.NextInt32(Random, 'a', 'z'), "" + TestUtil.NextInt32(Random, 'a', 'z'), Field.Store.NO));
            }
            return doc;
        }

        private void VerifyCount(IndexReader ir)
        {
            Fields fields = MultiFields.GetFields(ir);
            if (fields is null)
            {
                return;
            }
            foreach (string field in fields)
            {
                Terms terms = fields.GetTerms(field);
                if (terms is null)
                {
                    continue;
                }
                int docCount = terms.DocCount;
                FixedBitSet visited = new FixedBitSet(ir.MaxDoc);
                TermsEnum te = terms.GetEnumerator();
                while (te.MoveNext())
                {
                    DocsEnum de = TestUtil.Docs(Random, te, null, null, DocsFlags.NONE);
                    while (de.NextDoc() != DocIdSetIterator.NO_MORE_DOCS)
                    {
                        visited.Set(de.DocID);
                    }
                }
                Assert.AreEqual(visited.Cardinality, docCount);
            }
        }
    }
}