using Shogi.Domain.Pathing;
using System.Diagnostics;

namespace Shogi.Domain.Pieces
{
	[DebuggerDisplay("{WhichPiece} {Owner}")]
	public abstract class Piece
	{
		/// <summary>
		/// Creates a clone of an existing piece.
		/// </summary>
		public static Piece Create(Piece piece) => Create(piece.WhichPiece, piece.Owner, piece.IsPromoted);
		public static Piece Create(WhichPiece piece, WhichPlayer owner, bool isPromoted = false)
		{
			return piece switch
			{
				WhichPiece.King => new King(owner, isPromoted),
				WhichPiece.GoldGeneral => new GoldGeneral(owner, isPromoted),
				WhichPiece.SilverGeneral => new SilverGeneral(owner, isPromoted),
				WhichPiece.Bishop => new Bishop(owner, isPromoted),
				WhichPiece.Rook => new Rook(owner, isPromoted),
				WhichPiece.Knight => new Knight(owner, isPromoted),
				WhichPiece.Lance => new Lance(owner, isPromoted),
				WhichPiece.Pawn => new Pawn(owner, isPromoted),
				_ => throw new ArgumentException($"Unknown {nameof(WhichPiece)} when cloning a {nameof(Piece)}.")
			};
		}

		// TODO: MoveSet doesn't account for Player2's pieces which are upside-down.
		public abstract IEnumerable<Path> MoveSet { get; }
		public WhichPiece WhichPiece { get; }
		public WhichPlayer Owner { get; private set; }
		public bool IsPromoted { get; private set; }
		public bool IsUpsideDown => Owner == WhichPlayer.Player2;

		protected Piece(WhichPiece piece, WhichPlayer owner, bool isPromoted = false)
		{
			WhichPiece = piece;
			Owner = owner;
			IsPromoted = isPromoted;
		}

		public bool CanPromote => !IsPromoted
			&& WhichPiece != WhichPiece.King
			&& WhichPiece != WhichPiece.GoldGeneral;

		public void Promote() => IsPromoted = CanPromote;

		/// <summary>
		/// Prep the piece for capture by changing ownership and demoting.
		/// </summary>
		public void Capture(WhichPlayer newOwner)
		{
			Owner = newOwner;
			IsPromoted = false;
		}

		/// <summary>
		/// Respecting the move-set of the Piece, collect all positions from start to end.
		/// Useful if you need to iterate a move-set.
		/// </summary>
		/// <param name="start"></param>
		/// <param name="end"></param>
		/// <returns>An empty list if the piece cannot legally traverse from start to end. Otherwise, a list of positions.</returns>
		public IEnumerable<Vector2> GetPathFromStartToEnd(Vector2 start, Vector2 end)
		{
			var steps = new List<Vector2>(10);

			var path = this.MoveSet.GetNearestPath(start, end);
			var position = start;
			while (Vector2.Distance(start, position) < Vector2.Distance(start, end))
			{
				position += path.Direction;
				steps.Add(position);
			}

			if (position == end)
			{
				return steps;
			}

			return Array.Empty<Vector2>();
		}
	}
}