using System;
using System.Collections.Generic;
using System.Linq;
using OpenRa.FileFormats;

namespace RulesConverter
{
	using MiniYamlNodes = Dictionary<string, MiniYaml>;

	static class MiniYamlExts
	{
		public static void OptimizeInherits( this MiniYamlNodes y, MiniYamlNodes baseYaml )
		{
			foreach( var key in y.Keys.ToList() )
			{
				var node = y[ key ];
				try
				{
					MiniYaml inherits;
					node.Nodes.TryGetValue( "Inherits", out inherits );
					if( inherits == null || string.IsNullOrEmpty( inherits.Value ) )
						continue;

					MiniYaml parent;
					baseYaml.TryGetValue( inherits.Value, out parent );
					if( parent == null )
						continue;

					bool remove;
					y[ key ] = Diff( node, parent, out remove );
					if( remove )
						y.Add( "-" + key, new MiniYaml( null ) );
					if( y[ key ] == null )
						y.Remove( key );
				}
				catch
				{
					node.Nodes.Remove( "Inherits" );
				}
			}
		}

		static MiniYamlNodes Diff( MiniYamlNodes a, MiniYamlNodes b )
		{
			if( a.Count == 0 && b.Count == 0 )
				return null;
			if( b.Count == 0 )
				return a;
			if( a.Count == 0 )
				throw new NotImplementedException( "parent has key not in child" );

			var ret = new MiniYamlNodes();

			var keys = a.Keys.Union( b.Keys ).ToList();

			foreach( var key in keys )
			{
				MiniYaml aa, bb;
				a.TryGetValue( key, out aa );
				b.TryGetValue( key, out bb );
				bool remove;
				var diff = Diff( aa, bb, out remove );
				if( remove )
					ret.Add( "-" + key, new MiniYaml( null ) );

				if( diff != null )
					ret.Add( key, diff );
			}

			if( ret.Count == 0 ) return null;
			return ret;
		}

		static MiniYaml Diff( MiniYaml a, MiniYaml b, out bool remove )
		{
			remove = false;
			if( a == null && b == null )
				throw new InvalidOperationException( "can't happen" );
			else if( a == null )
			{
				remove = true;
				return a;
			}
			else if( b == null )
				return a;

			var diff = Diff( a.Nodes, b.Nodes );
			if( diff == null && a.Value == b.Value )
				return null;
			return new MiniYaml( a.Value, diff );
		}
	}
}