using System;
using System.Collections.Generic;
using ln.types.btree;
using System.Linq;
using System.IO;
using ln.logging;
using ln.objects.catalog;

namespace ln.types.odb.ng.index
{
    public class SimpleIndex : Index
    {
        BTreeValueList<ODBEntity, Guid> valueIndex = new BTreeValueList<ODBEntity, Guid>();
        BTreeValueList<Guid, ODBEntity> reverseIndex = new BTreeValueList<Guid, ODBEntity>();

        public SimpleIndex(Path path)
            : base(path)
        {
        }

        public override IEnumerable<Guid> GetDocumentIDs(Predicate<ODBEntity> predicate)
        {
            HashSet<Guid> matchedIDs = new HashSet<Guid>();
            foreach (ODBEntity value in valueIndex.Keys)
            {
                if (predicate(value))
                    foreach (Guid id in valueIndex[value])
                        matchedIDs.Add(id);
            }
            return matchedIDs;
        }

        public override void Add(Guid documentID, ODBEntity value)
        {
            valueIndex.Add(value, documentID);
            reverseIndex.Add(documentID, value);
        }

        public override void Remove(Guid documentID)
        {
            if (reverseIndex.ContainsKey(documentID))
            {
                foreach (ODBEntity value in reverseIndex[documentID].ToArray())
                {
                    valueIndex.Remove(value, documentID);
                }
                reverseIndex.Remove(documentID);
            }
        }

        public override bool LoadIndex(string basePath, long lastCloseTimestamp)
        {
            if (File.Exists(System.IO.Path.Combine(basePath, String.Format("{0}.idx", IndexName))))
                using (FileStream fileStream = new FileStream(System.IO.Path.Combine(basePath, String.Format("{0}.idx", IndexName)), FileMode.Open))
                {
                    byte[] indexBytes = fileStream.ReadBytes((int)fileStream.Length);
                    Document indexDocument = new Document(indexBytes, 0, indexBytes.Length);

                    long idxLastCloseTimestamp = indexDocument["LastCloseTimestamp"].As<long>();
                    if (idxLastCloseTimestamp != lastCloseTimestamp)
                    {
                        Logging.Log(LogLevel.WARNING, "Index timestamp {0} is not matching ( {1} != {2} )", IndexName, idxLastCloseTimestamp, lastCloseTimestamp);
                        return false;
                    }
                    else
                    {
                        foreach (ODBEntity key in indexDocument.Keys)
                        {
                            if (key is ODBGuid)
                            {
                                Guid documentID = key.As<Guid>();
                                ODBList valueList = indexDocument[key] as ODBList;
                                foreach (ODBEntity value in valueList)
                                {
                                    Add(documentID, value);
                                }

                            }
                        }
                        return true;
                    }
                }
            return false;
        }
        public override bool SaveIndex(string basePath, long lastCloseTimestamp)
        {
            Document indexDocument = new Document();
            indexDocument["LastCloseTimestamp"] = new ODBLong(lastCloseTimestamp);

            foreach (Guid documentID in reverseIndex.Keys)
            {
                ODBList valueList = new ODBList();
                valueList.AddRange(reverseIndex[documentID]);
                indexDocument[new ODBGuid(documentID)] = valueList;
            }

            byte[] indexBytes = indexDocument.GetStorageBytes();

            using (FileStream fileStream = new FileStream(System.IO.Path.Combine(basePath, String.Format("{0}.idx", IndexName)), FileMode.Create))
            {
                fileStream.WriteBytes(indexBytes);
                fileStream.Close();
            }

            return true;
        }
    }
}