#region Copyright & License Information
/*
 * Copyright 2007-2022 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, either version 3 of
 * the License, or (at your option) any later version. For more
 * information, see COPYING.
 */
#endregion

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.IO;
using System.Linq;
using OpenRA.Graphics;
using OpenRA.Primitives;

namespace OpenRA.Mods.Common.Graphics
{
	public class EmbeddedSpritePalette
	{
		readonly uint[] filePalette = null;
		readonly Dictionary<int, uint[]> framePalettes = null;

		public EmbeddedSpritePalette(uint[] filePalette = null, Dictionary<int, uint[]> framePalettes = null)
		{
			this.filePalette = filePalette;
			this.framePalettes = framePalettes;
		}

		public bool TryGetPaletteForFrame(int frame, out uint[] palette)
		{
			if (framePalettes == null || !framePalettes.TryGetValue(frame, out palette))
				palette = filePalette;

			return palette != null;
		}
	}

	public class DefaultSpriteSequenceLoader : ISpriteSequenceLoader
	{
		[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "IDE0060:Remove unused parameter", Justification = "Load game API")]
		public DefaultSpriteSequenceLoader(ModData modData) { }

		public virtual ISpriteSequence CreateSequence(ModData modData, string 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, string tileSet, SpriteCache cache, MiniYamlNode node)
		{
			var sequences = new Dictionary<string, ISpriteSequence>();
			var nodes = node.Value.ToDictionary();

			try
			{
				if (nodes.TryGetValue("Defaults", out var defaults))
				{
					nodes.Remove("Defaults");
					foreach (var n in nodes)
					{
						n.Value.Nodes = MiniYaml.Merge(new[] { defaults.Nodes, n.Value.Nodes });
						n.Value.Value = n.Value.Value ?? defaults.Value;
					}
				}
			}
			catch (Exception e)
			{
				throw new InvalidDataException($"Error occurred while parsing {node.Key}", e);
			}

			foreach (var kvp in nodes)
			{
				using (new Support.PerfTimer($"new Sequence(\"{node.Key}\")", 20))
				{
					try
					{
						sequences.Add(kvp.Key, CreateSequence(modData, tileSet, cache, node.Key, kvp.Key, kvp.Value));
					}
					catch (FileNotFoundException ex)
					{
						// Defer exception until something tries to access the sequence
						// This allows the asset installer and OpenRA.Utility to load the game without having the actor assets
						sequences.Add(kvp.Key, new FileNotFoundSequence(ex));
					}
				}
			}

			return new ReadOnlyDictionary<string, ISpriteSequence>(sequences);
		}
	}

	public class FileNotFoundSequence : ISpriteSequence
	{
		readonly FileNotFoundException exception;

		public FileNotFoundSequence(FileNotFoundException exception)
		{
			this.exception = exception;
		}

		public string Filename => exception.FileName;

		string ISpriteSequence.Name => throw exception;
		int ISpriteSequence.Start => throw exception;
		int ISpriteSequence.Length => throw exception;
		int ISpriteSequence.Stride => throw exception;
		int ISpriteSequence.Facings => throw exception;
		int ISpriteSequence.Tick => throw exception;
		int ISpriteSequence.ZOffset => throw exception;
		int ISpriteSequence.ShadowStart => throw exception;
		int ISpriteSequence.ShadowZOffset => throw exception;
		int[] ISpriteSequence.Frames => throw exception;
		Rectangle ISpriteSequence.Bounds => throw exception;
		bool ISpriteSequence.IgnoreWorldTint => throw exception;
		float ISpriteSequence.Scale => throw exception;
		Sprite ISpriteSequence.GetSprite(int frame) { throw exception; }
		Sprite ISpriteSequence.GetSprite(int frame, WAngle facing) { throw exception; }
		Sprite ISpriteSequence.GetShadow(int frame, WAngle facing) { throw exception; }
		float ISpriteSequence.GetAlpha(int frame) { throw exception; }
	}

	public struct SpriteSequenceField<T>
	{
		public string Key;
		public T DefaultValue;

		public SpriteSequenceField(string key, T defaultValue)
		{
			Key = key;
			DefaultValue = defaultValue;
		}
	}

	[Desc("Generic sprite sequence implementation, mostly unencumbered with game- or artwork-specific logic.")]
	public class DefaultSpriteSequence : ISpriteSequence
	{
		protected Sprite[] sprites;
		readonly bool reverseFacings, transpose;
		readonly string sequence;

		protected readonly ISpriteSequenceLoader Loader;

		public Rectangle Bounds { get; }

		public string Name { get; }

		[Desc("Frame index to start from.")]
		static readonly SpriteSequenceField<int> Start = new SpriteSequenceField<int>(nameof(Start), 0);
		int ISpriteSequence.Start => start;
		int start;

		[Desc("Number of frames to use. Does not have to be the total amount the sprite sheet has.")]
		static readonly SpriteSequenceField<int> Length = new SpriteSequenceField<int>(nameof(Length), 1);
		int ISpriteSequence.Length => length;
		int length;

		[Desc("Overrides Length if a different number of frames is defined between facings.")]
		static readonly SpriteSequenceField<int> Stride = new SpriteSequenceField<int>(nameof(Stride), -1);
		int ISpriteSequence.Stride => stride;
		int stride;

		[Desc("The amount of directions the unit faces. Use negative values to rotate counter-clockwise.")]
		static readonly SpriteSequenceField<int> Facings = new SpriteSequenceField<int>(nameof(Facings), 1);
		int ISpriteSequence.Facings => facings;
		protected int facings;

		[Desc("Time (in milliseconds at default game speed) to wait until playing the next frame in the animation.")]
		static readonly SpriteSequenceField<int> Tick = new SpriteSequenceField<int>(nameof(Tick), 40);
		int ISpriteSequence.Tick => tick;
		readonly int tick;

		[Desc("Value controlling the Z-order. A higher values means rendering on top of other sprites at the same position. " +
			"Use power of 2 values to avoid glitches.")]
		static readonly SpriteSequenceField<WDist> ZOffset = new SpriteSequenceField<WDist>(nameof(ZOffset), WDist.Zero);
		int ISpriteSequence.ZOffset => zOffset;
		readonly int zOffset;

		[Desc("Additional sprite depth Z offset to apply as a function of sprite Y (0: vertical, 1: flat on terrain)")]
		static readonly SpriteSequenceField<int> ZRamp = new SpriteSequenceField<int>(nameof(ZRamp), 0);

		[Desc("If the shadow is not part of the sprite, but baked into the same sprite sheet at a fixed offset, " +
			"set this to the frame index where it starts.")]
		static readonly SpriteSequenceField<int> ShadowStart = new SpriteSequenceField<int>(nameof(ShadowStart), -1);
		int ISpriteSequence.ShadowStart => shadowStart;
		readonly int shadowStart;

		[Desc("Set Z-Offset for the separate shadow. Used by the later Westwood 2.5D titles.")]
		static readonly SpriteSequenceField<WDist> ShadowZOffset = new SpriteSequenceField<WDist>(nameof(ShadowZOffset), new WDist(-5));
		int ISpriteSequence.ShadowZOffset => shadowZOffset;
		readonly int shadowZOffset;

		[Desc("The individual frames to play instead of going through them sequentially from the `Start`.")]
		static readonly SpriteSequenceField<int[]> Frames = new SpriteSequenceField<int[]>(nameof(Frames), null);
		int[] ISpriteSequence.Frames => frames;
		int[] frames;

		[Desc("Don't apply terrain lighting or colored overlays.")]
		static readonly SpriteSequenceField<bool> IgnoreWorldTint = new SpriteSequenceField<bool>(nameof(IgnoreWorldTint), false);
		bool ISpriteSequence.IgnoreWorldTint => ignoreWorldTint;
		readonly bool ignoreWorldTint;

		[Desc("Adjusts the rendered size of the sprite")]
		static readonly SpriteSequenceField<float> Scale = new SpriteSequenceField<float>(nameof(Scale), 1);
		float ISpriteSequence.Scale => scale;
		readonly float scale;

		[Desc("Play the sprite sequence back and forth.")]
		static readonly SpriteSequenceField<bool> Reverses = new SpriteSequenceField<bool>(nameof(Reverses), false);

		[Desc("Support a frame order where each animation step is split per each direction.")]
		static readonly SpriteSequenceField<bool> Transpose = new SpriteSequenceField<bool>(nameof(Transpose), false);

		[Desc("Mirror on the X axis.")]
		static readonly SpriteSequenceField<bool> FlipX = new SpriteSequenceField<bool>(nameof(FlipX), false);

		[Desc("Mirror on the Y axis.")]
		static readonly SpriteSequenceField<bool> FlipY = new SpriteSequenceField<bool>(nameof(FlipY), false);

		[Desc("Change the position in-game on X, Y, Z.")]
		static readonly SpriteSequenceField<float3> Offset = new SpriteSequenceField<float3>(nameof(Offset), float3.Zero);

		[Desc("Apply an OpenGL/Photoshop inspired blend mode.")]
		static readonly SpriteSequenceField<BlendMode> BlendMode = new SpriteSequenceField<BlendMode>(nameof(BlendMode), OpenRA.BlendMode.Alpha);

		[Desc("Allows to append multiple sequence definitions which are indented below this node " +
			"like when offsets differ per frame or a sequence is spread across individual files.")]
		static readonly SpriteSequenceField<MiniYaml> Combine = new SpriteSequenceField<MiniYaml>(nameof(Combine), null);

		[Desc("Sets transparency - use one value to set for all frames or provide a value for each frame.")]
		static readonly SpriteSequenceField<float[]> Alpha = new SpriteSequenceField<float[]>(nameof(Alpha), null);
		readonly float[] alpha;

		[Desc("Fade the animation from fully opaque on the first frame to fully transparent after the last frame.")]
		static readonly SpriteSequenceField<bool> AlphaFade = new SpriteSequenceField<bool>(nameof(AlphaFade), false);

		[Desc("Name of the file containing the depth data sprite.")]
		static readonly SpriteSequenceField<string> DepthSprite = new SpriteSequenceField<string>(nameof(DepthSprite), null);

		[Desc("Frame index containing the depth data.")]
		static readonly SpriteSequenceField<int> DepthSpriteFrame = new SpriteSequenceField<int>(nameof(DepthSpriteFrame), 0);

		[Desc("X, Y offset to apply to the depth sprite.")]
		static readonly SpriteSequenceField<float2> DepthSpriteOffset = new SpriteSequenceField<float2>(nameof(DepthSpriteOffset), float2.Zero);

		[Desc("Make a custom palette embedded in the sprite available to the PaletteFromEmbeddedSpritePalette trait.")]
		static readonly SpriteSequenceField<bool> HasEmbeddedPalette = new SpriteSequenceField<bool>(nameof(HasEmbeddedPalette), false);

		public readonly uint[] EmbeddedPalette;

		protected virtual string GetSpriteSrc(ModData modData, string 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)
		{
			if (d.TryGetValue(key, out var value))
				return FieldLoader.GetValue<T>(key, value.Value);

			return fallback;
		}

		protected static T LoadField<T>(Dictionary<string, MiniYaml> d, SpriteSequenceField<T> field)
		{
			if (d.TryGetValue(field.Key, out var value))
				return FieldLoader.GetValue<T>(field.Key, value.Value);

			return field.DefaultValue;
		}

		protected static Rectangle FlipRectangle(Rectangle rect, bool flipX, bool flipY)
		{
			var left = flipX ? rect.Right : rect.Left;
			var top = flipY ? rect.Bottom : rect.Top;
			var right = flipX ? rect.Left : rect.Right;
			var bottom = flipY ? rect.Top : rect.Bottom;

			return Rectangle.FromLTRB(left, top, right, bottom);
		}

		public DefaultSpriteSequence(ModData modData, string tileSet, SpriteCache cache, ISpriteSequenceLoader loader, string sequence, string animation, MiniYaml info)
		{
			this.sequence = sequence;
			Name = animation;
			Loader = loader;
			var d = info.ToDictionary();

			try
			{
				start = LoadField(d, Start);
				shadowStart = LoadField(d, ShadowStart);
				shadowZOffset = LoadField(d, ShadowZOffset).Length;
				zOffset = LoadField(d, ZOffset).Length;
				tick = LoadField(d, Tick);
				transpose = LoadField(d, Transpose);
				frames = LoadField(d, Frames);
				ignoreWorldTint = LoadField(d, IgnoreWorldTint);
				scale = LoadField(d, Scale);

				var flipX = LoadField(d, FlipX);
				var flipY = LoadField(d, FlipY);
				var zRamp = LoadField(d, ZRamp);

				facings = LoadField(d, Facings);
				if (facings < 0)
				{
					reverseFacings = true;
					facings = -facings;
				}

				var offset = LoadField(d, Offset);
				var blendMode = LoadField(d, BlendMode);

				Func<int, IEnumerable<int>> getUsedFrames = frameCount =>
				{
					if (d.TryGetValue(Length.Key, out var lengthYaml) && lengthYaml.Value == "*")
						length = frames?.Length ?? frameCount - start;
					else
						length = LoadField(d, Length);

					// Plays the animation forwards, and then in reverse
					if (LoadField(d, Reverses))
					{
						var frames = this.frames != null ? this.frames.Skip(start).Take(length).ToArray() : Exts.MakeArray(length, i => start + i);
						this.frames = frames.Concat(frames.Skip(1).Take(length - 2).Reverse()).ToArray();
						length = 2 * length - 2;
						start = 0;
					}

					// Overrides Length with a custom stride
					stride = LoadField(d, Stride.Key, length);

					if (length > stride)
						throw new YamlException($"Sequence {sequence}.{animation}: Length must be <= stride");

					if (frames != null && length > frames.Length)
						throw new YamlException($"Sequence {sequence}.{animation}: Length must be <= Frames.Length");

					var end = start + (facings - 1) * stride + length - 1;
					if (frames != null)
					{
						foreach (var f in frames)
							if (f < 0 || f >= frameCount)
								throw new YamlException($"Sequence {sequence}.{animation} defines a Frames override that references frame {f}, but only [{start}..{end}] actually exist");

						if (start < 0 || end >= frames.Length)
							throw new YamlException($"Sequence {sequence}.{animation} uses indices [{start}..{end}] of the Frames list, but only {frames.Length} frames are defined");
					}
					else if (start < 0 || end >= frameCount)
						throw new YamlException($"Sequence {sequence}.{animation} uses frames [{start}..{end}], but only [0..{frameCount - 1}] actually exist");

					if (shadowStart >= 0 && shadowStart + (facings - 1) * stride + length > frameCount)
						throw new YamlException($"Sequence {sequence}.{animation}'s shadow frames use frames [{shadowStart}..{shadowStart + (facings - 1) * stride + length - 1}], but only [0..{frameCount - 1}] actually exist");

					var usedFrames = new List<int>();
					for (var facing = 0; facing < facings; facing++)
					{
						for (var frame = 0; frame < length; frame++)
						{
							var i = transpose ? (frame % length) * facings + facing :
								(facing * stride) + (frame % length);

							usedFrames.Add(frames != null ? frames[i] : start + i);
						}
					}

					if (shadowStart >= 0)
						return usedFrames.Concat(usedFrames.Select(i => i + shadowStart - start));

					return usedFrames;
				};

				if (d.TryGetValue(Combine.Key, out var combine))
				{
					var combined = Enumerable.Empty<Sprite>();
					foreach (var sub in combine.Nodes)
					{
						var sd = sub.Value.ToDictionary();

						// Allow per-sprite offset, flipping, start, and length
						// These shouldn't inherit Start/Offset/etc from the main definition
						var subStart = LoadField(sd, Start);
						var subOffset = LoadField(sd, Offset);
						var subFlipX = LoadField(sd, FlipX);
						var subFlipY = LoadField(sd, FlipY);
						var subFrames = LoadField(sd, Frames);
						var subLength = 0;

						Func<int, IEnumerable<int>> subGetUsedFrames = subFrameCount =>
						{
							if (sd.TryGetValue(Length.Key, out var subLengthYaml) && subLengthYaml.Value == "*")
								subLength = subFrames != null ? subFrames.Length : subFrameCount - subStart;
							else
								subLength = LoadField(sd, Length);

							return subFrames != null ? subFrames.Skip(subStart).Take(subLength) : Enumerable.Range(subStart, subLength);
						};

						var subSrc = GetSpriteSrc(modData, tileSet, sequence, animation, sub.Key, sd);
						var subSprites = cache[subSrc, subGetUsedFrames].Select(s =>
						{
							if (s == null)
								return null;

							var bounds = FlipRectangle(s.Bounds, subFlipX, subFlipY);
							var dx = subOffset.X + offset.X + (subFlipX ? -s.Offset.X : s.Offset.X);
							var dy = subOffset.Y + offset.Y + (subFlipY ? -s.Offset.Y : s.Offset.Y);
							var dz = subOffset.Z + offset.Z + s.Offset.Z + zRamp * dy;

							return new Sprite(s.Sheet, bounds, zRamp, new float3(dx, dy, dz), s.Channel, blendMode);
						}).ToList();

						var frames = subFrames != null ? subFrames.Skip(subStart).Take(subLength).ToArray() : Exts.MakeArray(subLength, i => subStart + i);
						combined = combined.Concat(frames.Select(i => subSprites[i]));
					}

					sprites = combined.ToArray();
					getUsedFrames(sprites.Length);
				}
				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, getUsedFrames].Select(s =>
					{
						if (s == null)
							return null;

						var bounds = FlipRectangle(s.Bounds, flipX, flipY);
						var dx = offset.X + (flipX ? -s.Offset.X : s.Offset.X);
						var dy = offset.Y + (flipY ? -s.Offset.Y : s.Offset.Y);
						var dz = offset.Z + s.Offset.Z + zRamp * dy;

						return new Sprite(s.Sheet, bounds, zRamp, new float3(dx, dy, dz), s.Channel, blendMode);
					}).ToArray();
				}

				alpha = LoadField(d, Alpha);
				if (alpha != null)
				{
					if (alpha.Length == 1)
						alpha = Exts.MakeArray(length, _ => alpha[0]);
					else if (alpha.Length != length)
						throw new YamlException($"Sequence {sequence}.{animation} must define either 1 or {length} Alpha values.");
				}

				if (LoadField(d, AlphaFade))
				{
					if (alpha != null)
						throw new YamlException($"Sequence {sequence}.{animation} cannot define both AlphaFade and Alpha.");

					alpha = Exts.MakeArray(length, i => float2.Lerp(1f, 0f, i / (length - 1f)));
				}

				var depthSprite = LoadField(d, DepthSprite);
				if (!string.IsNullOrEmpty(depthSprite))
				{
					var depthSpriteFrame = LoadField(d, DepthSpriteFrame);
					var depthOffset = LoadField(d, DepthSpriteOffset);
					IEnumerable<int> GetDepthFrame(int _) => new[] { depthSpriteFrame };
					var ds = cache[depthSprite, GetDepthFrame][depthSpriteFrame];

					sprites = sprites.Select(s =>
					{
						if (s == null)
							return null;

						var cw = (ds.Bounds.Left + ds.Bounds.Right) / 2 + (int)(s.Offset.X + depthOffset.X);
						var ch = (ds.Bounds.Top + ds.Bounds.Bottom) / 2 + (int)(s.Offset.Y + depthOffset.Y);
						var w = s.Bounds.Width / 2;
						var h = s.Bounds.Height / 2;

						var r = Rectangle.FromLTRB(cw - w, ch - h, cw + w, ch + h);
						return new SpriteWithSecondaryData(s, ds.Sheet, r, ds.Channel);
					}).ToArray();
				}

				if (LoadField(d, HasEmbeddedPalette))
				{
					var src = GetSpriteSrc(modData, tileSet, sequence, animation, info.Value, d);

					var metadata = cache.FrameMetadata(src);
					var i = frames != null ? frames[0] : start;
					var palettes = metadata?.GetOrDefault<EmbeddedSpritePalette>();
					if (palettes == null || !palettes.TryGetPaletteForFrame(i, out EmbeddedPalette))
						throw new YamlException($"Cannot export palette from {src}: frame {i} does not define an embedded palette");
				}

				var boundSprites = SpriteBounds(sprites, frames, start, facings, length, stride, transpose);
				if (shadowStart > 0)
					boundSprites = boundSprites.Concat(SpriteBounds(sprites, frames, shadowStart, facings, length, stride, transpose));

				Bounds = boundSprites.Union();
			}
			catch (FormatException f)
			{
				throw new FormatException($"Failed to parse sequences for {sequence}.{animation} at {info.Nodes[0].Location}:\n{f}");
			}
		}

		/// <summary>Returns the bounds of all of the sprites that can appear in this animation</summary>
		static IEnumerable<Rectangle> SpriteBounds(Sprite[] sprites, int[] frames, int start, int facings, int length, int stride, bool transpose)
		{
			for (var facing = 0; facing < facings; facing++)
			{
				for (var frame = 0; frame < length; frame++)
				{
					var i = transpose ? (frame % length) * facings + facing :
								(facing * stride) + (frame % length);
					var s = frames != null ? sprites[frames[i]] : sprites[start + i];
					if (!s.Bounds.IsEmpty)
						yield return new Rectangle(
							(int)(s.Offset.X - s.Size.X / 2),
							(int)(s.Offset.Y - s.Size.Y / 2),
							s.Bounds.Width, s.Bounds.Height);
				}
			}
		}

		public Sprite GetSprite(int frame)
		{
			return GetSprite(start, frame, WAngle.Zero);
		}

		public Sprite GetSprite(int frame, WAngle facing)
		{
			return GetSprite(start, frame, facing);
		}

		public Sprite GetShadow(int frame, WAngle facing)
		{
			return shadowStart >= 0 ? GetSprite(shadowStart, frame, facing) : null;
		}

		protected virtual Sprite GetSprite(int start, int frame, WAngle facing)
		{
			var f = GetFacingFrameOffset(facing);
			if (reverseFacings)
				f = (facings - f) % facings;

			var i = transpose ? (frame % length) * facings + f :
				(f * stride) + (frame % length);

			var j = frames != null ? frames[i] : start + i;
			if (sprites[j] == null)
				throw new InvalidOperationException($"Attempted to query unloaded sprite from {Name}.{sequence} start={start} frame={frame} facing={facing}");

			return sprites[j];
		}

		protected virtual int GetFacingFrameOffset(WAngle facing)
		{
			return Util.IndexFacing(facing, facings);
		}

		public virtual float GetAlpha(int frame)
		{
			return alpha?[frame] ?? 1f;
		}
	}
}