// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.

namespace System.Data.Entity.Core.Metadata.Edm
{
    using System.Collections.Generic;
    using System.Diagnostics;
    using System.Linq;
    using System.Reflection;

    // <summary>
    // This class is responsible for keeping track of which assemblies we have already
    // considered so we don't reconsider them again.
    // The current rules for an assembly to be "seen" is
    // 1. It is already in our dictionary
    // AND
    // 1.  We are in attribute loading mode
    // OR
    // 2. We have seen it already with a non null EdmItemCollection
    // OR
    // 3. We are seeing it with a null EdmItemCollection this time
    // </summary>
    internal class KnownAssembliesSet
    {
        private readonly Dictionary<Assembly, KnownAssemblyEntry> _assemblies;

        internal KnownAssembliesSet()
        {
            _assemblies = new Dictionary<Assembly, KnownAssemblyEntry>();
        }

        internal KnownAssembliesSet(KnownAssembliesSet set)
        {
            _assemblies = new Dictionary<Assembly, KnownAssemblyEntry>(set._assemblies);
        }

        internal virtual bool TryGetKnownAssembly(
            Assembly assembly, object loaderCookie, EdmItemCollection itemCollection, out KnownAssemblyEntry entry)
        {
            if (!_assemblies.TryGetValue(assembly, out entry))
            {
                return false;
            }

            if (!entry.HaveSeenInCompatibleContext(loaderCookie, itemCollection))
            {
                return false;
            }

            return true;
        }

        internal IEnumerable<Assembly> Assemblies
        {
            get { return _assemblies.Keys; }
        }

        public IEnumerable<KnownAssemblyEntry> GetEntries(object loaderCookie, EdmItemCollection itemCollection)
        {
            return _assemblies.Values.Where(e => e.HaveSeenInCompatibleContext(loaderCookie, itemCollection));
        }

        internal bool Contains(Assembly assembly, object loaderCookie, EdmItemCollection itemCollection)
        {
            KnownAssemblyEntry entry;
            return TryGetKnownAssembly(assembly, loaderCookie, itemCollection, out entry);
        }

        internal void Add(Assembly assembly, KnownAssemblyEntry knownAssemblyEntry)
        {
            KnownAssemblyEntry current;
            if (_assemblies.TryGetValue(assembly, out current))
            {
                Debug.Assert(
                    current.SeenWithEdmItemCollection != knownAssemblyEntry.SeenWithEdmItemCollection &&
                    knownAssemblyEntry.SeenWithEdmItemCollection,
                    "should only be updating if we haven't seen it with an edmItemCollection yet.");
                _assemblies[assembly] = knownAssemblyEntry;
            }
            else
            {
                _assemblies.Add(assembly, knownAssemblyEntry);
            }
        }
    }
}
