// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
using osu.Game.Database;
using SQLite.Net;

namespace osu.Game.Rulesets
{
    /// <summary>
    /// Todo: All of this needs to be moved to a RulesetStore.
    /// </summary>
    public class RulesetStore : DatabaseBackedStore
    {
        private static readonly Dictionary<Assembly, Type> loaded_assemblies = new Dictionary<Assembly, Type>();

        public IEnumerable<RulesetInfo> AllRulesets => Query<RulesetInfo>().Where(r => r.Available);

        public RulesetStore(SQLiteConnection connection) : base(connection)
        {
        }

        static RulesetStore()
        {
            AppDomain.CurrentDomain.AssemblyResolve += currentDomain_AssemblyResolve;

            foreach (string file in Directory.GetFiles(Environment.CurrentDirectory, $"{ruleset_library_prefix}.*.dll"))
                loadRulesetFromFile(file);
        }

        private static Assembly currentDomain_AssemblyResolve(object sender, ResolveEventArgs args) => loaded_assemblies.Keys.FirstOrDefault(a => a.FullName == args.Name);

        private const string ruleset_library_prefix = "osu.Game.Rulesets";

        protected override void Prepare(bool reset = false)
        {
            Connection.CreateTable<RulesetInfo>();

            if (reset)
            {
                Connection.DeleteAll<RulesetInfo>();
            }

            var instances = loaded_assemblies.Values.Select(r => (Ruleset)Activator.CreateInstance(r, new RulesetInfo()));

            Connection.RunInTransaction(() =>
            {
                //add all legacy modes in correct order
                foreach (var r in instances.Where(r => r.LegacyID >= 0).OrderBy(r => r.LegacyID))
                {
                    Connection.InsertOrReplace(createRulesetInfo(r));
                }

                //add any other modes
                foreach (var r in instances.Where(r => r.LegacyID < 0))
                {
                    var us = createRulesetInfo(r);

                    var existing = Query<RulesetInfo>().Where(ri => ri.InstantiationInfo == us.InstantiationInfo).FirstOrDefault();

                    if (existing == null)
                        Connection.Insert(us);
                }
            });

            Connection.RunInTransaction(() =>
            {
                //perform a consistency check
                foreach (var r in Query<RulesetInfo>())
                {
                    try
                    {
                        r.CreateInstance();
                        r.Available = true;
                    }
                    catch
                    {
                        r.Available = false;
                    }

                    Connection.Update(r);
                }
            });
        }

        private static void loadRulesetFromFile(string file)
        {
            var filename = Path.GetFileNameWithoutExtension(file);

            if (loaded_assemblies.Values.Any(t => t.Namespace == filename))
                return;

            try
            {
                var assembly = Assembly.LoadFrom(file);
                loaded_assemblies[assembly] = assembly.GetTypes().First(t => t.IsSubclassOf(typeof(Ruleset)));
            }
            catch (Exception) { }
        }

        private RulesetInfo createRulesetInfo(Ruleset ruleset) => new RulesetInfo
        {
            Name = ruleset.Description,
            InstantiationInfo = ruleset.GetType().AssemblyQualifiedName,
            ID = ruleset.LegacyID
        };

        protected override Type[] ValidTypes => new[] { typeof(RulesetInfo) };

        public RulesetInfo GetRuleset(int id) => Query<RulesetInfo>().First(r => r.ID == id);
    }
}
