/// Credit jack.sydorenko, firagon
/// Sourced from - http://forum.unity3d.com/threads/new-ui-and-line-drawing.253772/
/// Updated/Refactored from - http://forum.unity3d.com/threads/new-ui-and-line-drawing.253772/#post-2528050

using System.Collections.Generic;

namespace UnityEngine.UI.Extensions
{
    [AddComponentMenu("UI/Extensions/Primitives/UILineRenderer")]
    [RequireComponent(typeof(RectTransform))]
    public class UILineRenderer : UIPrimitiveBase
	{
		private enum SegmentType
		{
			Start,
            Middle,
            End,
            Full,
		}

		public enum JoinType
		{
			Bevel,
            Miter
		}

		public enum BezierType
		{
			None,
            Quick,
            Basic,
            Improved,
            Catenary,
        }

		private const float MIN_MITER_JOIN = 15 * Mathf.Deg2Rad;

		// A bevel 'nice' join displaces the vertices of the line segment instead of simply rendering a
		// quad to connect the endpoints. This improves the look of textured and transparent lines, since
		// there is no overlapping.
        private const float MIN_BEVEL_NICE_JOIN = 30 * Mathf.Deg2Rad;

		private static Vector2 UV_TOP_LEFT, UV_BOTTOM_LEFT, UV_TOP_CENTER_LEFT, UV_TOP_CENTER_RIGHT, UV_BOTTOM_CENTER_LEFT, UV_BOTTOM_CENTER_RIGHT, UV_TOP_RIGHT, UV_BOTTOM_RIGHT;
		private static Vector2[] startUvs, middleUvs, endUvs, fullUvs;

        [SerializeField, Tooltip("Points to draw lines between\n Can be improved using the Resolution Option")]
        internal Vector2[] m_points;

        [SerializeField, Tooltip("Thickness of the line")]
        internal float lineThickness = 2;
        [SerializeField, Tooltip("Use the relative bounds of the Rect Transform (0,0 -> 0,1) or screen space coordinates")]
        internal bool relativeSize;
        [SerializeField, Tooltip("Do the points identify a single line or split pairs of lines")]
        internal bool lineList;
        [SerializeField, Tooltip("Add end caps to each line\nMultiple caps when used with Line List")]
        internal bool lineCaps;
        [SerializeField, Tooltip("Resolution of the Bezier curve, different to line Resolution")]
        internal int bezierSegmentsPerCurve = 10;

        public float LineThickness
        {
            get { return lineThickness; }
            set { lineThickness = value; SetAllDirty(); }
        }

        public bool RelativeSize
        {
            get { return relativeSize; }
            set { relativeSize = value; SetAllDirty(); }
        }

        public bool LineList
        {
            get { return lineList; }
            set { lineList = value; SetAllDirty(); }
        }

        public bool LineCaps
        {
            get { return lineCaps; }
            set { lineCaps = value; SetAllDirty(); }
        }

        [Tooltip("The type of Join used between lines, Square/Mitre or Curved/Bevel")]
		public JoinType LineJoins = JoinType.Bevel;

        [Tooltip("Bezier method to apply to line, see docs for options\nCan't be used in conjunction with Resolution as Bezier already changes the resolution")]
        public BezierType BezierMode = BezierType.None;

        public int BezierSegmentsPerCurve
        {
            get { return bezierSegmentsPerCurve; }
            set { bezierSegmentsPerCurve = value; }
        }

        [HideInInspector]
        public bool drivenExternally = false;


		/// <summary>
		/// Points to be drawn in the line.
		/// </summary>
        public Vector2[] Points
		{
			get
			{
				return m_points;
			}

			set
			{
				if (m_points == value)
					return;
				m_points = value;
				SetAllDirty();
			}
		}

        protected override void OnPopulateMesh(VertexHelper vh)
		{
			if (m_points == null)
				return;
            GeneratedUVs();
			Vector2[] pointsToDraw = m_points;
			//If Bezier is desired, pick the implementation
            if (BezierMode != BezierType.None && BezierMode != BezierType.Catenary && m_points.Length > 3)
			{
				BezierPath bezierPath = new BezierPath();

				bezierPath.SetControlPoints(pointsToDraw);
				bezierPath.SegmentsPerCurve = bezierSegmentsPerCurve;
				List<Vector2> drawingPoints;
				switch (BezierMode)
				{
					case BezierType.Basic:
                        drawingPoints = bezierPath.GetDrawingPoints0();
					break;
					case BezierType.Improved:
                        drawingPoints = bezierPath.GetDrawingPoints1();
					break;
					default:
                        drawingPoints = bezierPath.GetDrawingPoints2();
					break;
				}

				pointsToDraw = drawingPoints.ToArray();
			}
            if (BezierMode == BezierType.Catenary && m_points.Length == 2)
            {
                CableCurve cable = new CableCurve(pointsToDraw);
                cable.slack = Resoloution;
                cable.steps = BezierSegmentsPerCurve;
                pointsToDraw = cable.Points();
            }

            if (ImproveResolution != ResolutionMode.None)
            {
                pointsToDraw = IncreaseResolution(pointsToDraw);
            }

            // scale based on the size of the rect or use absolute, this is switchable
            var sizeX = !relativeSize ? 1 : rectTransform.rect.width;
            var sizeY = !relativeSize ? 1 : rectTransform.rect.height;
            var offsetX = -rectTransform.pivot.x * sizeX;
            var offsetY = -rectTransform.pivot.y * sizeY;

			vh.Clear();

			// Generate the quads that make up the wide line
            var segments = new List<UIVertex[]>();
			if (lineList)
			{
				for (var i = 1; i < pointsToDraw.Length; i += 2)
				{
					var start = pointsToDraw[i - 1];
					var end = pointsToDraw[i];
					start = new Vector2(start.x * sizeX + offsetX, start.y * sizeY + offsetY);
					end = new Vector2(end.x * sizeX + offsetX, end.y * sizeY + offsetY);

					if (lineCaps)
					{
						segments.Add(CreateLineCap(start, end, SegmentType.Start));
					}

					//segments.Add(CreateLineSegment(start, end, SegmentType.Full));
					segments.Add(CreateLineSegment(start, end, SegmentType.Middle));

                    if (lineCaps)
					{
						segments.Add(CreateLineCap(start, end, SegmentType.End));
					}
				}
			}
			else
			{
				for (var i = 1; i < pointsToDraw.Length; i++)
				{
					var start = pointsToDraw[i - 1];
					var end = pointsToDraw[i];
					start = new Vector2(start.x * sizeX + offsetX, start.y * sizeY + offsetY);
					end = new Vector2(end.x * sizeX + offsetX, end.y * sizeY + offsetY);

					if (lineCaps && i == 1)
					{
						segments.Add(CreateLineCap(start, end, SegmentType.Start));
					}

					segments.Add(CreateLineSegment(start, end, SegmentType.Middle));
					//segments.Add(CreateLineSegment(start, end, SegmentType.Full));

					if (lineCaps && i == pointsToDraw.Length - 1)
					{
						segments.Add(CreateLineCap(start, end, SegmentType.End));
					}
				}
			}

			// Add the line segments to the vertex helper, creating any joins as needed
            for (var i = 0; i < segments.Count; i++)
			{
				if (!lineList && i < segments.Count - 1)
				{
					var vec1 = segments[i][1].position - segments[i][2].position;
					var vec2 = segments[i + 1][2].position - segments[i + 1][1].position;
					var angle = Vector2.Angle(vec1, vec2) * Mathf.Deg2Rad;

					// Positive sign means the line is turning in a 'clockwise' direction
                    var sign = Mathf.Sign(Vector3.Cross(vec1.normalized, vec2.normalized).z);

					// Calculate the miter point
                    var miterDistance = lineThickness / (2 * Mathf.Tan(angle / 2));
					var miterPointA = segments[i][2].position - vec1.normalized * miterDistance * sign;
					var miterPointB = segments[i][3].position + vec1.normalized * miterDistance * sign;

					var joinType = LineJoins;
					if (joinType == JoinType.Miter)
					{
						// Make sure we can make a miter join without too many artifacts.
                        if (miterDistance < vec1.magnitude / 2 && miterDistance < vec2.magnitude / 2 && angle > MIN_MITER_JOIN)
						{
							segments[i][2].position = miterPointA;
							segments[i][3].position = miterPointB;
							segments[i + 1][0].position = miterPointB;
							segments[i + 1][1].position = miterPointA;
						}
						else
						{
							joinType = JoinType.Bevel;
						}
					}

					if (joinType == JoinType.Bevel)
					{
						if (miterDistance < vec1.magnitude / 2 && miterDistance < vec2.magnitude / 2 && angle > MIN_BEVEL_NICE_JOIN)
						{
							if (sign < 0)
							{
								segments[i][2].position = miterPointA;
								segments[i + 1][1].position = miterPointA;
							}
							else
							{
								segments[i][3].position = miterPointB;
								segments[i + 1][0].position = miterPointB;
							}
						}

						var join = new UIVertex[] { segments[i][2], segments[i][3], segments[i + 1][0], segments[i + 1][1] };
						vh.AddUIVertexQuad(join);
					}
				}

				vh.AddUIVertexQuad(segments[i]);
			}
            if (vh.currentVertCount > 64000)
            {
                Debug.LogError("Max Verticies size is 64000, current mesh vertcies count is [" + vh.currentVertCount + "] - Cannot Draw");
                vh.Clear();
                return;
            }
        }

		private UIVertex[] CreateLineCap(Vector2 start, Vector2 end, SegmentType type)
		{
			if (type == SegmentType.Start)
			{
				var capStart = start - ((end - start).normalized * lineThickness / 2);
				return CreateLineSegment(capStart, start, SegmentType.Start);
			}
			else if (type == SegmentType.End)
			{
				var capEnd = end + ((end - start).normalized * lineThickness / 2);
				return CreateLineSegment(end, capEnd, SegmentType.End);
			}

			Debug.LogError("Bad SegmentType passed in to CreateLineCap. Must be SegmentType.Start or SegmentType.End");
			return null;
		}

		private UIVertex[] CreateLineSegment(Vector2 start, Vector2 end, SegmentType type)
		{
			Vector2 offset = new Vector2((start.y - end.y), end.x - start.x).normalized * lineThickness / 2;

			var v1 = start - offset;
			var v2 = start + offset;
			var v3 = end + offset;
			var v4 = end - offset;
            //Return the VDO with the correct uvs
            switch (type)
            {
                case SegmentType.Start:
                    return SetVbo(new[] { v1, v2, v3, v4 }, startUvs);
                case SegmentType.End:
                    return SetVbo(new[] { v1, v2, v3, v4 }, endUvs);
                case SegmentType.Full:
                    return SetVbo(new[] { v1, v2, v3, v4 }, fullUvs);
                default:
                    return SetVbo(new[] { v1, v2, v3, v4 }, middleUvs);
            }
		}

        protected override void GeneratedUVs()
        {
            if (activeSprite != null)
            {
                var outer = Sprites.DataUtility.GetOuterUV(activeSprite);
                var inner = Sprites.DataUtility.GetInnerUV(activeSprite);
                UV_TOP_LEFT = new Vector2(outer.x, outer.y);
                UV_BOTTOM_LEFT = new Vector2(outer.x, outer.w);
                UV_TOP_CENTER_LEFT = new Vector2(inner.x, inner.y);
                UV_TOP_CENTER_RIGHT = new Vector2(inner.z, inner.y);
                UV_BOTTOM_CENTER_LEFT = new Vector2(inner.x, inner.w);
                UV_BOTTOM_CENTER_RIGHT = new Vector2(inner.z, inner.w);
                UV_TOP_RIGHT = new Vector2(outer.z, outer.y);
                UV_BOTTOM_RIGHT = new Vector2(outer.z, outer.w);
            }
            else
            {
                UV_TOP_LEFT = Vector2.zero;
                UV_BOTTOM_LEFT = new Vector2(0, 1);
                UV_TOP_CENTER_LEFT = new Vector2(0.5f, 0);
                UV_TOP_CENTER_RIGHT = new Vector2(0.5f, 0);
                UV_BOTTOM_CENTER_LEFT = new Vector2(0.5f, 1);
                UV_BOTTOM_CENTER_RIGHT = new Vector2(0.5f, 1);
                UV_TOP_RIGHT = new Vector2(1, 0);
                UV_BOTTOM_RIGHT = Vector2.one;
            }


            startUvs = new[] { UV_TOP_LEFT, UV_BOTTOM_LEFT, UV_BOTTOM_CENTER_LEFT, UV_TOP_CENTER_LEFT };
            middleUvs = new[] { UV_TOP_CENTER_LEFT, UV_BOTTOM_CENTER_LEFT, UV_BOTTOM_CENTER_RIGHT, UV_TOP_CENTER_RIGHT };
            endUvs = new[] { UV_TOP_CENTER_RIGHT, UV_BOTTOM_CENTER_RIGHT, UV_BOTTOM_RIGHT, UV_TOP_RIGHT };
            fullUvs = new[] { UV_TOP_LEFT, UV_BOTTOM_LEFT, UV_BOTTOM_RIGHT, UV_TOP_RIGHT };
        }

        protected override void ResolutionToNativeSize(float distance)
        {
            if (UseNativeSize)
            {
                m_Resolution = distance / (activeSprite.rect.width / pixelsPerUnit);
                lineThickness = activeSprite.rect.height / pixelsPerUnit;
            }
        }
    }
}