using System;
using System.Collections.Generic;
using System.Linq;

namespace GridAStar;

public struct AStarPath
{
	public AStarPathBuilder Settings { get; internal set; }
	public List<AStarNode> Nodes { get; set; } = new();
	public Grid Grid => Settings.Grid;
	public int Count => Nodes?.Count() ?? 0;
	public bool IsEmpty => Nodes == null || Count == 0;
	float length = 0f;
	public float Length
	{
		get
		{
			if ( length == 0 )
			{
				var newLength = CalculateLength();
				length = newLength;
			}

			return length;
		}
	}

	public AStarPath() { }

	public AStarPath( AStarPathBuilder builder, List<AStarNode> nodes ) : this()
	{
		Settings = builder;
		Nodes = nodes;
	}

	public static AStarPath From( AStarPathBuilder builder, List<AStarNode> nodes ) => new AStarPath( builder, nodes );

	public static AStarPath Empty() => new AStarPath();

	public float CalculateLength()
	{
		var length = 0f;
		for ( int i = 0; i < Nodes.Count - 1; i++ )
			length += Nodes[i].EndPosition.Distance( Nodes[i + 1].EndPosition );

		return length;
	}

	/// <summary>
	/// Simplify the path by iterating over line of sights between the given segment size, joining them if valid
	/// </summary>
	public void Simplify( int segmentAmounts = 2, int iterations = 8, params string[] tagsToExclude )
	{
		for ( int iteration = 0; iteration < iterations; iteration++ )
		{
			var segmentStart = 0;
			var segmentEnd = Math.Min( segmentAmounts, Count - 1 );

			while ( Count > 2 && segmentEnd < Count - 1 )
			{
				var currentNode = Nodes[segmentStart];
				var nextNode = Nodes[segmentStart + 1];
				var furtherNode = Nodes[segmentEnd];

				if ( !currentNode.Tags.Has( tagsToExclude ) && !nextNode.Tags.Has( tagsToExclude ) && !furtherNode.Tags.Has( tagsToExclude ) )
					if ( nextNode.MovementTag == "" || nextNode.MovementTag == string.Empty || furtherNode.MovementTag == "" || furtherNode.MovementTag == string.Empty )
						if ( Settings.Grid.LineOfSight( currentNode.Current, furtherNode.Current, Settings.PathCreator ) )
							for ( int toDelete = segmentStart + 1; toDelete < segmentEnd; toDelete++ )
								Nodes.RemoveAt( toDelete );


				if ( segmentEnd == Count - 1 )
					break;

				segmentStart++;
				segmentEnd = Math.Min( segmentStart + segmentAmounts, Count - 1 );
			}
		}

		length = CalculateLength();
	}
}