context: #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.IO;
  using System.Linq;
  using OpenRA.Graphics;
  
  namespace OpenRA.Mods.Common.Graphics
  {
  	public class DefaultSpriteSequenceLoader : ISpriteSequenceLoader
  	{
  		public Action<string> OnMissingSpriteError { get; set; }
  		public DefaultSpriteSequenceLoader(ModData modData) { }
  
  		public virtual ISpriteSequence CreateSequence(ModData modData, TileSet tileSet, SpriteCache cache, string sequence, string animation, MiniYaml info)
  		{
  			return new DefaultSpriteSequence(modData, tileSet, cache, this, sequence, animation, info);
  		}
  
  		public IReadOnlyDictionary<string, ISpriteSequence> ParseSequences(ModData modData, TileSet tileSet, SpriteCache cache, MiniYamlNode node)
  		{
  			var sequences = new Dictionary<string, ISpriteSequence>();
  			var nodes = node.Value.ToDictionary();
  
  			MiniYaml defaults;
  			if (nodes.TryGetValue("Defaults", out defaults))
  			{
  				nodes.Remove("Defaults");
  				nodes = nodes.ToDictionary(kv => kv.Key, kv => MiniYaml.MergeStrict(kv.Value, defaults));
  
  				foreach (var n in nodes)
  					n.Value.Value = n.Value.Value ?? defaults.Value;
  			}
  
  			foreach (var kvp in nodes)
  			{
  				using (new Support.PerfTimer("new Sequence(\"{0}\")".F(node.Key), 20))
  				{
  					try
  					{
  						sequences.Add(kvp.Key, CreateSequence(modData, tileSet, cache, node.Key, kvp.Key, kvp.Value));
  					}
  					catch (FileNotFoundException ex)
  					{
  						// Eat the FileNotFound exceptions from missing sprites
  						OnMissingSpriteError(ex.Message);
  					}
  				}
  			}
  
  			return new ReadOnlyDictionary<string, ISpriteSequence>(sequences);
  		}
  	}
  
  	public class DefaultSpriteSequence : ISpriteSequence
  	{
  		static readonly WDist DefaultShadowSpriteZOffset = new WDist(-5);
  		readonly Sprite[] sprites;
  		readonly bool reverseFacings, transpose;
  
  		protected readonly ISpriteSequenceLoader Loader;
  
  		public string Name { get; private set; }
  		public int Start { get; private set; }
  		public int Length { get; private set; }
  		public int Stride { get; private set; }
  		public int Facings { get; private set; }
  		public int Tick { get; private set; }
  		public int ZOffset { get; private set; }
  		public int ShadowStart { get; private set; }
  		public int ShadowZOffset { get; private set; }
  		public int[] Frames { get; private set; }
  
  		protected virtual string GetSpriteSrc(ModData modData, TileSet tileSet, string sequence, string animation, string sprite, Dictionary<string, MiniYaml> d)
  		{
  			return sprite ?? sequence;
  		}
  
  		protected static T LoadField<T>(Dictionary<string, MiniYaml> d, string key, T fallback)
  		{
  			MiniYaml value;
  			if (d.TryGetValue(key, out value))
  				return FieldLoader.GetValue<T>(key, value.Value);
  
  			return fallback;
  		}
  
  		public DefaultSpriteSequence(ModData modData, TileSet tileSet, SpriteCache cache, ISpriteSequenceLoader loader, string sequence, string animation, MiniYaml info)
  		{
  			Name = animation;
  			Loader = loader;
  			var d = info.ToDictionary();
  
  			try
  			{
  				Start = LoadField<int>(d, "Start", 0);
  				ShadowStart = LoadField<int>(d, "ShadowStart", -1);
  				ShadowZOffset = LoadField<WDist>(d, "ShadowZOffset", DefaultShadowSpriteZOffset).Length;
  				ZOffset = LoadField<WDist>(d, "ZOffset", WDist.Zero).Length;
  				Tick = LoadField<int>(d, "Tick", 40);
  				transpose = LoadField<bool>(d, "Transpose", false);
  				Frames = LoadField<int[]>(d, "Frames", null);
  
  				Facings = LoadField<int>(d, "Facings", 1);
  				if (Facings < 0)
  				{
  					reverseFacings = true;
  					Facings = -Facings;
  				}
  
  				var offset = LoadField<float2>(d, "Offset", float2.Zero);
  				var blendMode = LoadField<BlendMode>(d, "BlendMode", BlendMode.Alpha);
  
  				MiniYaml combine;
  				if (d.TryGetValue("Combine", out combine))
  				{
  					var combined = Enumerable.Empty<Sprite>();
  					foreach (var sub in combine.Nodes)
  					{
  						var sd = sub.Value.ToDictionary();
  
  						// Allow per-sprite offset, start, and length
  						var subStart = LoadField<int>(sd, "Start", 0);
  						var subOffset = LoadField<float2>(sd, "Offset", float2.Zero);
  
  						var subSrc = GetSpriteSrc(modData, tileSet, sequence, animation, sub.Key, sd);
  						var subSprites = cache[subSrc].Select(
  							s => new Sprite(s.Sheet, s.Bounds, s.Offset + subOffset + offset, s.Channel, blendMode));
  
  						var subLength = 0;
  						MiniYaml subLengthYaml;
  						if (sd.TryGetValue("Length", out subLengthYaml) && subLengthYaml.Value == "*")
  							subLength = subSprites.Count() - subStart;
  						else
  							subLength = LoadField<int>(sd, "Length", 1);
  
  						combined = combined.Concat(subSprites.Skip(subStart).Take(subLength));
  					}
  
  					sprites = combined.ToArray();
  				}
  				else
  				{
  					// Apply offset to each sprite in the sequence
  					// Different sequences may apply different offsets to the same frame
  					var src = GetSpriteSrc(modData, tileSet, sequence, animation, info.Value, d);
  					sprites = cache[src].Select(
  						s => new Sprite(s.Sheet, s.Bounds, s.Offset + offset, s.Channel, blendMode)).ToArray();
  				}
  
  				MiniYaml length;
  				if (d.TryGetValue("Length", out length) && length.Value == "*")
  					Length = sprites.Length - Start;
  				else
  					Length = LoadField<int>(d, "Length", 1);
  
  				// Plays the animation forwards, and then in reverse
  				if (LoadField<bool>(d, "Reverses", false))
  				{
  					var frames = Frames ?? Exts.MakeArray(Length, i => Start + i);
  					Frames = frames.Concat(frames.Skip(1).Take(frames.Length - 2).Reverse()).ToArray();
  					Length = 2 * Length - 2;
  				}
  
  				Stride = LoadField<int>(d, "Stride", Length);
  
  				if (Length > Stride)
  					throw new InvalidOperationException(
  						"{0}: Sequence {1}.{2}: Length must be <= stride"
  						.F(info.Nodes[0].Location, sequence, animation));
  
  				if (Start < 0 || Start + Facings * Stride > sprites.Length)
  					throw new InvalidOperationException(
  						"{5}: Sequence {0}.{1} uses frames [{2}..{3}], but only 0..{4} actually exist"
  						.F(sequence, animation, Start, Start + Facings * Stride - 1, sprites.Length - 1,
  							info.Nodes[0].Location));
  
  				if (ShadowStart + Facings * Stride > sprites.Length)
  					throw new InvalidOperationException(
  						"{5}: Sequence {0}.{1}'s shadow frames use frames [{2}..{3}], but only [0..{4}] actually exist"
  						.F(sequence, animation, ShadowStart, ShadowStart + Facings * Stride - 1, sprites.Length - 1,
  							info.Nodes[0].Location));
  			}
  			catch (FormatException f)
  			{
  				throw new FormatException("Failed to parse sequences for {0}.{1} at {2}:\n{3}".F(sequence, animation, info.Nodes[0].Location, f));
  			}
  		}
  
  		public Sprite GetSprite(int frame)
  		{
  			return GetSprite(Start, frame, 0);
  		}
  
  		public Sprite GetSprite(int frame, int facing)
  		{
  			return GetSprite(Start, frame, facing);
  		}
  
  		public Sprite GetShadow(int frame, int facing)
  		{
  			return ShadowStart >= 0 ? GetSprite(ShadowStart, frame, facing) : null;
  		}
  
  		protected virtual Sprite GetSprite(int start, int frame, int facing)
  		{
  			var f = OpenRA.Traits.Util.QuantizeFacing(facing, Facings);
  
  			if (reverseFacings)
  				f = (Facings - f) % Facings;
  
  
gt: 			var i = transpose ? (frame % Length) * Facings + f :