#region Copyright & License Information
/*
 * Copyright 2007-2015 The OpenRA Developers (see AUTHORS)
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation. For more information,
 * see COPYING.
 */
#endregion

using System;
using System.Collections.Generic;
using System.Linq;
using OpenRA.Primitives;
using OpenRA.Traits;

namespace OpenRA
{
	// TODO: This is not exported into the documentation yet.
	[Desc("A unit/building inside the game. Every rules starts with one and adds trait to it.",
		"Special actors like world or player are usually defined in system.yaml and affect everything.")]
	public class ActorInfo
	{
		[Desc("The actor name can be anything, but the sprites used in the Render*: traits default to this one.",
			"If you add an ^ in front of the name, the engine will recognize this as a collection of traits",
			"that can be inherited by others (using Inherits:) and not a real unit.",
			"You can remove inherited traits by adding a - infront of them as in -TraitName: to inherit everything, but this trait.")]
		public readonly string Name;
		public readonly TypeDictionary Traits = new TypeDictionary();
		List<ITraitInfo> constructOrderCache = null;

		public ActorInfo(string name, MiniYaml node, Dictionary<string, MiniYaml> allUnits)
		{
			try
			{
				var mergedNode = MergeWithParent(node, allUnits).ToDictionary();

				Name = name;
				foreach (var t in mergedNode)
					if (t.Key != "Inherits" && !t.Key.StartsWith("-"))
						Traits.Add(LoadTraitInfo(t.Key.Split('@')[0], t.Value));
			}
			catch (YamlException e)
			{
				throw new YamlException("Actor type {0}: {1}".F(name, e.Message));
			}
		}

		static MiniYaml GetParent(MiniYaml node, Dictionary<string, MiniYaml> allUnits)
		{
			MiniYaml inherits;
			node.ToDictionary().TryGetValue("Inherits", out inherits);
			if (inherits == null || string.IsNullOrEmpty(inherits.Value))
				return null;

			MiniYaml parent;
			allUnits.TryGetValue(inherits.Value, out parent);
			if (parent == null)
				throw new InvalidOperationException(
					"Bogus inheritance -- actor type {0} does not exist".F(inherits.Value));

			return parent;
		}

		static MiniYaml MergeWithParent(MiniYaml node, Dictionary<string, MiniYaml> allUnits)
		{
			var parent = GetParent(node, allUnits);
			if (parent != null)
			{
				var result = MiniYaml.MergeStrict(node, MergeWithParent(parent, allUnits));

				// strip the '-'
				result.Nodes.RemoveAll(a => a.Key.StartsWith("-"));
				return result;
			}

			return node;
		}

		static ITraitInfo LoadTraitInfo(string traitName, MiniYaml my)
		{
			if (!string.IsNullOrEmpty(my.Value))
				throw new YamlException("Junk value `{0}` on trait node {1}"
				.F(my.Value, traitName));
			var info = Game.CreateObject<ITraitInfo>(traitName + "Info");
			FieldLoader.Load(info, my);
			return info;
		}

		public IEnumerable<ITraitInfo> TraitsInConstructOrder()
		{
			if (constructOrderCache != null)
				return constructOrderCache;

			var source = Traits.WithInterface<ITraitInfo>().Select(i => new
			{
				Trait = i,
				Type = i.GetType(),
				Dependencies = PrerequisitesOf(i).ToList()
			}).ToList();

			var resolved = source.Where(s => !s.Dependencies.Any()).ToList();
			var unresolved = source.Except(resolved);

			var testResolve = new Func<Type, Type, bool>((a, b) => a == b || a.IsAssignableFrom(b));
			var more = unresolved.Where(u => u.Dependencies.All(d => resolved.Exists(r => testResolve(d, r.Type))));

			// Re-evaluate the vars above until sorted
			while (more.Any())
				resolved.AddRange(more);

			if (unresolved.Any())
			{
				var exceptionString = "ActorInfo(\"" + Name + "\") failed to initialize because of the following:\r\n";
				var missing = unresolved.SelectMany(u => u.Dependencies.Where(d => !source.Any(s => testResolve(d, s.Type)))).Distinct();

				exceptionString += "Missing:\r\n";
				foreach (var m in missing)
					exceptionString += m + " \r\n";

				exceptionString += "Unresolved:\r\n";
				foreach (var u in unresolved)
				{
					var deps = u.Dependencies.Where(d => !resolved.Exists(r => r.Type == d));
					exceptionString += u.Type + ": { " + string.Join(", ", deps) + " }\r\n";
				}

				throw new Exception(exceptionString);
			}

			constructOrderCache = resolved.Select(r => r.Trait).ToList();
			return constructOrderCache;
		}

		static IEnumerable<Type> PrerequisitesOf(ITraitInfo info)
		{
			return info
				.GetType()
				.GetInterfaces()
				.Where(t => t.IsGenericType && t.GetGenericTypeDefinition() == typeof(Requires<>))
				.Select(t => t.GetGenericArguments()[0]);
		}

		public IEnumerable<Pair<string, Type>> GetInitKeys()
		{
			var inits = Traits.WithInterface<ITraitInfo>().SelectMany(
				t => t.GetType().GetInterfaces()
					.Where(i => i.IsGenericType && i.GetGenericTypeDefinition() == typeof(UsesInit<>))
					.Select(i => i.GetGenericArguments()[0])).ToList();

			inits.Add(typeof(OwnerInit));		/* not exposed by a trait; this is used by the Actor itself */

			return inits.Select(
				i => Pair.New(
					i.Name.Replace("Init", ""), i));
		}
	}
}