using System.Collections.Generic;
using System.Linq;
using System.Diagnostics;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using System.Collections;
using System;

public class Line
{
    private List<Vector2> points;
    private float thickness;

    public enum JoinType
    {
        None,
        Miter,
        Bevel,
        Round
    }

    public enum LineCaps
    {
        None,
        Round
    }

    private Color LineColor { get; set; }
    private LineCaps LineEndings { get; set; }
    private JoinType JoinTypes { get; set; }

    //Graphical representation
    private VertexBuffer vbo;
    private IndexBuffer ibo;
    private GraphicsDevice gDevice;

    private class LinkedMeshList : IEnumerable<LinkedMeshListNode>
    {
        public int Count { get; set; }

        public LinkedMeshListNode FirstNode { get; private set; }

        public LinkedMeshListNode LastNode { get; private set; }

        public LinkedMeshList()
        {
            this.Count = 0;
        }

        public void Remove(LinkedMeshListNode node)
        {
            throw new NotImplementedException();
        }

        public void AddBefore(LinkedMeshListNode node, LinkedMeshListNode beforeNode)
        {
            var oldBefore = node.Previous;

            oldBefore.Next = beforeNode;
            beforeNode.Previous = oldBefore;

            beforeNode.Next = node;
            node.Previous = beforeNode;

            Count++;
        }

        public void AddAfter(LinkedMeshListNode node, LinkedMeshListNode afterNode)
        {
            var oldNext = node.Next;

            node.Next = afterNode;
            afterNode.Previous = node;

            afterNode.Next = oldNext;
            oldNext.Previous = afterNode;

            Count++;
        }

        public void Append(LinkedMeshListNode node)
        {
            if(this.Count == 0)
            {
                this.FirstNode = node;
                this.LastNode = node;
                Count++;
                return;
            }

            this.LastNode.Next = node;
            node.Previous = this.LastNode;
            this.LastNode = node;
            this.Count++;
        }

        public List<VertexPositionColorTexture> GetVerticeList()
        {
            List<VertexPositionColorTexture> verticesList = new List<VertexPositionColorTexture>();
            foreach(var node in this)
            {
                verticesList.AddRange(node.GenerateVerticeList());
            }
            return verticesList;
        }

        public List<ushort> GetIndiceList()
        {
            List<ushort> indeicesList = new List<ushort>();
            foreach(var node in this)
            {
                indeicesList.AddRange(node.GenerateIndiceList());
            }
            return indeicesList;
        }

        public IEnumerator<LinkedMeshListNode> GetEnumerator()
        {
            LinkedMeshListNode curNode = this.FirstNode;
            while(curNode != null)
            {
                yield
                return curNode;
                curNode = curNode.Next;
            }
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            throw new NotImplementedException();
        }
    }

    private abstract class LinkedMeshListNode
    {
        public LinkedMeshListNode Next { get; set; }

        private LinkedMeshListNode previous;
        public LinkedMeshListNode Previous { 
            get {
                return this.previous;
            }
            set {
                this.IndexOffset = value.IndexOffset + value.GetVertexCount();
                this.previous = value;
            }
        }

        public int IndexOffset { get; private set; }

        public abstract int GetVertexCount();

        public abstract List<VertexPositionColorTexture> GenerateVerticeList();
        public abstract List<ushort> GenerateIndiceList();

        public LinkedMeshListNode()
        {
            this.IndexOffset = 0;
        }
    }

    private class Segment : LinkedMeshListNode   {
        public Vector2 Start { get; private set; }
        public Vector2 End { get; private set; }
        public Vector2 Normal { get; private set; }
        public const ushort INDEX_BL = 0;
        public const ushort INDEX_BR = 1;
        public const ushort INDEX_TL = 2;
        public const ushort INDEX_TR = 3;
        private Color color { get; set; }
        
        public Segment(Vector2 start, Vector2 end, Color color) : base()
        {
            this.Start = start;
            this.End = end;
            Vector2 dir = end - start;
            Vector2 perpendincularVector = new Vector2(dir.Y, -dir.X);
            perpendincularVector.Normalize();
            this.Normal = perpendincularVector;
            this.color = color;
        }

        public override List<VertexPositionColorTexture> GenerateVerticeList()
        {
            List<VertexPositionColorTexture> vertices = new List<VertexPositionColorTexture>();
            var offsetPoint1 = new Vector3(this.Start.X, this.Start.Y ,0.0f);
            vertices.Add(new VertexPositionColorTexture(offsetPoint1, this.color, this.Normal));
            vertices.Add(new VertexPositionColorTexture(offsetPoint1, this.color, this.Normal * -1));
            var offsetPoint1Next = new Vector3(this.End.X, this.End.Y ,0.0f);
            vertices.Add(new VertexPositionColorTexture(offsetPoint1Next, this.color, this.Normal));
            vertices.Add(new VertexPositionColorTexture(offsetPoint1Next, this.color, this.Normal * -1));
            return vertices;
        }

        public override List<ushort> GenerateIndiceList()
        {
            List<ushort> indices = new List<ushort>();
            indices.Add((ushort)(this.IndexOffset + INDEX_BL));
            indices.Add((ushort)(this.IndexOffset + INDEX_BR));
            indices.Add((ushort)(this.IndexOffset + INDEX_TL));

            indices.Add((ushort)(this.IndexOffset + INDEX_TL));
            indices.Add((ushort)(this.IndexOffset + INDEX_BR));
            indices.Add((ushort)(this.IndexOffset + INDEX_TR));

            return indices;
        }

        public override int GetVertexCount()
        {
            return 4;
        }
    }

    private class BevelLineJoin : LinkedMeshListNode
    {
        private Color color { get; set; }

        public BevelLineJoin(Color color) : base()
        {
            this.color = color;
        }

        public override List<ushort> GenerateIndiceList()
        {
            Debug.Assert(this.Previous != null);
            Debug.Assert(this.Previous is Segment);
            Debug.Assert(this.Next != null);
            Debug.Assert(this.Next is Segment);
            var next = this.Next as Segment;
            var previous = this.Previous as Segment;

            ushort lastOffset = (ushort) previous.IndexOffset;
            ushort nextOffset = (ushort) next.IndexOffset;

            List<ushort> indices = new List<ushort>();
            indices.Add((ushort)(lastOffset+Segment.INDEX_TL));
            indices.Add((ushort)(lastOffset+Segment.INDEX_TR));
            indices.Add((ushort)(nextOffset+Segment.INDEX_BL));

            indices.Add((ushort)(lastOffset+Segment.INDEX_TL));
            indices.Add((ushort)(lastOffset+Segment.INDEX_TR));
            indices.Add((ushort)(nextOffset+Segment.INDEX_BR));
            return indices;
        }

        public override List<VertexPositionColorTexture> GenerateVerticeList()
        {
            return new List<VertexPositionColorTexture>();
        }

        public override int GetVertexCount()
        {
            return 0;
        }
    }

    public Line(List<Vector2> points) 
    : this(points, 1.0f)
    {}

    public Line(List<Vector2> points, float thickness) 
    : this(points, thickness, Color.Black)
    {}

    public Line(List<Vector2> points, float thickness, Color color)
    : this(points,thickness, color, JoinType.None)
    {}

    public Line(List<Vector2> points, float thickness, Color color, JoinType joinType)
    : this(points, thickness, color, joinType, LineCaps.None)
    {}

    public Line(List<Vector2> points, float thickness, Color color, JoinType joinType, LineCaps caps)
    {
        this.points = points;
        this.thickness = thickness;
        this.LineColor = color;
        this.JoinTypes = joinType;
        this.LineEndings = caps;
    }

    public void InitOnGraphicalDevice(GraphicsDevice device)
    {
        this.gDevice = device;
        Debug.Assert(this.points.Count >= 2);

        LinkedMeshList meshList = new LinkedMeshList();
        
        for(int i = 0; i < this.points.Count - 1 ; i++)
        {
            var p = this.points[i];
            var pNext = this.points[i+1];
            meshList.Append(new Segment(p, pNext, this.LineColor));
        }

        var curNode = meshList.FirstNode;
        while(curNode != null && curNode.Next != null)
        {
            meshList.AddAfter(curNode, new BevelLineJoin(this.LineColor));
            curNode = curNode.Next.Next;
        }

        List<VertexPositionColorTexture> vertices = meshList.GetVerticeList();
        List<ushort> indices = meshList.GetIndiceList();

        this.vbo = new VertexBuffer(device, typeof(VertexPositionColorTexture), vertices.Count, BufferUsage.WriteOnly);
        this.vbo.SetData<VertexPositionColorTexture>(vertices.ToArray());
        this.ibo = new IndexBuffer(device, typeof(ushort), indices.Count,BufferUsage.WriteOnly);
        this.ibo.SetData<ushort>(indices.ToArray());
    }

    public void Draw(Effect lineEffect)
    {
        this.gDevice.SetVertexBuffer(this.vbo);
        this.gDevice.Indices = this.ibo;
        RasterizerState rasterizerState = new RasterizerState();
        // rasterizerState.CullMode = CullMode.None;
        //rasterizerState.FillMode = FillMode.WireFrame;
        this.gDevice.RasterizerState = rasterizerState;
        lineEffect.Parameters["thickness"].SetValue(this.thickness);
        foreach (EffectPass pass in lineEffect.CurrentTechnique.Passes)
        {
            pass.Apply();
            this.gDevice.DrawIndexedPrimitives(PrimitiveType.TriangleList,0,0,this.ibo.IndexCount / 3);
            //this.gDevice.DrawPrimitives(PrimitiveType.LineList, 0, this.vbo.VertexCount);
        }        
    }
}