using AppDiagnostic.Logging;
using System.Collections.Generic;
using System.Linq;

namespace AppDiagnostic
{
    public sealed class DiagnosticLogStore
    {
        private const int MaximumLogCount = 10000;
        private static readonly DiagnosticLogStore instance = new DiagnosticLogStore();
        private readonly object syncRoot = new object();
        private readonly List<DiagnosticLogEntry> entries = new List<DiagnosticLogEntry>();
        private long totalReceived;
        private long version;

        private DiagnosticLogStore()
        {
        }

        public static DiagnosticLogStore Instance => instance;

        public long TotalReceived
        {
            get
            {
                lock (syncRoot)
                {
                    return totalReceived;
                }
            }
        }

        public long Version
        {
            get
            {
                lock (syncRoot)
                {
                    return version;
                }
            }
        }

        public void Add(DiagnosticLogEntry entry)
        {
            if (entry == null)
            {
                return;
            }

            lock (syncRoot)
            {
                entries.Add(entry);
                totalReceived++;
                version++;

                int excessCount = entries.Count - MaximumLogCount;
                if (excessCount > 0)
                {
                    entries.RemoveRange(0, excessCount);
                }
            }
        }

        public List<DiagnosticLogEntry> GetSnapshot()
        {
            lock (syncRoot)
            {
                return entries.ToList();
            }
        }

        public void Clear()
        {
            lock (syncRoot)
            {
                entries.Clear();
                version++;
            }
        }
    }
}