using System.Runtime.InteropServices;

namespace AdvancedMappingTools;

public enum FloorFit
{
	[Title( "Inside The Walls" )] Inside,
	[Title( "Wall Centre" )] Center,
	[Title( "Outside The Walls" )] Outside
}

/// <summary>
/// Draw the outline of a floor or ceiling slab, straight or curved. Points near the corners of
/// finished walls land on them, at the foot for a floor and at the top for a ceiling, and the
/// slab then fits inside the walls, on their centre or over them.
/// </summary>
[ToolCategory( "Walls & Floors" )]
[Title( "Floor" ), Icon( "grid_on" )]
public sealed class FloorEditor( PrimitiveTool tool ) : PathEditor( tool )
{
	protected override int MinPoints => 3;
	protected override bool AlwaysClosed => true;

	[Property, Range( 0, 512, slider: false ), WideMode, Description( "Slab thickness below the drawn outline. Zero makes a single face." )]
	public float Thickness { get; set; } = 8.0f;

	[Property, Range( -4096, 4096, slider: false ), WideMode, Description( "Raises the slab above the drawn outline." )]
	public float Elevation { get; set; } = 0.0f;

	[Property, Group( "Walls" ), WideMode, Description( "Where a slab drawn on wall corners ends: on the inner face, on the centre of the walls, or on their outer face." )]
	public FloorFit Fit { get; set; } = FloorFit.Inside;

	[Property, Advanced, Group( "Walls" ), Title( "Wall Margin" ), Range( 0, 256, slider: false ), WideMode, Description( "Half the wall, set when the points snap onto wall corners. Fit moves the outline in or out by this much." )]
	public float WallMargin { get; set; } = 0.0f;

	protected override bool Connects => true;

	const float CornerReach = 16.0f;

	protected override Vector3? UnderCursor( Vector3 point ) => WallCornerUnderCursor( point, CornerReach ) ?? base.UnderCursor( point );

	/// <summary>
	/// A point near a wall corner lands on it, at its foot or its top, whichever the click was nearer to.
	/// </summary>
	protected override Vector3 Dock( Vector3 point )
	{
		var docked = base.Dock( point );

		if ( !ConnectFinished || SceneEditorSession.Active is null ) return docked;

		var corner = WallTops.Nearest( SceneEditorSession.Active.Scene, docked, DockRadius + CornerReach );

		if ( Points.Count == 0 ) WallMargin = corner?.Half ?? 0.0f;

		if ( corner is not { } found ) return docked;

		WallMargin = MathF.Max( WallMargin, found.Half );

		// The click itself says which: docking may have pulled it onto a corner of the wall mesh.
		var top = MathF.Abs( point.z - found.Top.z ) < MathF.Abs( point.z - found.Foot.z );
		var spot = top ? found.Top : found.Foot;

		DrawLabel( spot, top ? "Wall top" : "Wall foot", Color.Green );

		return spot;
	}

	/// <summary>
	/// The outline moved out (positive) or in (negative) by a distance, corner by corner.
	/// </summary>
	static List<Vector3> Offset( List<Vector3> ring, float distance )
	{
		if ( MathF.Abs( distance ) < 0.001f ) return ring;

		var result = new List<Vector3>( ring.Count );
		var limit = MathF.Abs( distance ) * 4.0f;

		for ( var i = 0; i < ring.Count; i++ )
		{
			var before = ring[(i + ring.Count - 1) % ring.Count];
			var at = ring[i];
			var after = ring[(i + 1) % ring.Count];

			// Outward normals of the two edges of a counter clockwise outline.
			var a = (at - before).WithZ( 0.0f ).Normal;
			var b = (after - at).WithZ( 0.0f ).Normal;
			var na = new Vector3( a.y, -a.x, 0.0f );
			var nb = new Vector3( b.y, -b.x, 0.0f );
			var bisector = (na + nb).Normal;
			var cos = bisector.Dot( na );
			var length = cos > 0.05f ? MathF.Min( distance / cos, limit ) : distance;

			result.Add( at + bisector * (MathF.Abs( length ) * MathF.Sign( distance )) );
		}

		return result;
	}

	protected override bool IsShapeValid
	{
		get
		{
			var ring = SamplePath();
			return ring.Count >= 3 && Mesh.TriangulatePolygon( CollectionsMarshal.AsSpan( ring ) ).Length >= 3;
		}
	}

	protected override void BuildMesh( MeshKit kit )
	{
		var ring = SamplePath();
		if ( SignedArea( ring ) < 0.0f ) ring.Reverse();

		var margin = MathF.Max( WallMargin, 0.0f );
		ring = Offset( ring, Fit switch { FloorFit.Inside => -margin, FloorFit.Outside => margin, _ => 0.0f } );

		var top = Vector3.Up * Elevation;
		var bottom = Vector3.Up * (Elevation - Thickness);

		kit.Face( [.. ring.Select( x => x + top )] );

		if ( Thickness <= 0.0f ) return;

		kit.Material = TrimMaterial;
		kit.Face( [.. ring.AsEnumerable().Reverse().Select( x => x + bottom )] );

		for ( var i = 0; i < ring.Count; i++ )
		{
			var a = ring[i];
			var b = ring[(i + 1) % ring.Count];
			kit.Face( a + bottom, b + bottom, b + top, a + top );
		}
	}
}