using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using TransportGame.Model;
using TransportGame.Model.Road;
using TransportGame.Utils;
using UnityEngine;
using Vector2 = TransportGame.Model.Vector2;

//#define DEBUG_ROAD_MESH_GENERATOR

namespace TransportGame.Unity
{
    class RoadMeshGenerator
    {
        #region Constants
        
        private const float SidewalkWidth = .8f;
        private const float LaneWidth = 1f;

        private const float RaiseOffset = 0.8f; // Raises road above actual height of terrain
        private const float SidewalkHeight = 0.1f; // Height of sidewalk
        private const float SideCoverHeight = 0.1f; // On the sides of the roads, so that we can't see the road from the underside

        #endregion

        #region Private fields

        private Map map;

        private Dictionary<int, Vector2[]> segmentTerminal1Limit = new Dictionary<int, Vector2[]>();
        private Dictionary<int, Vector2[]> segmentTerminal2Limit = new Dictionary<int, Vector2[]>();

        private GameObject parent = new GameObject("roadNetwork");

        #endregion

        public Material RoadMaterial { get; set; }
        public Material SidewalkMaterial { get; set; }

        public IEnumerable Generate(Map map)
        {
            this.map = map;

            List<int> visitedNodes = new List<int>();
            List<int> visitedSegments = new List<int>();
            Queue<RoadNode> queue = new Queue<RoadNode>();
            queue.Enqueue(map.RoadNetwork.Nodes.First().Value);
            int i = 0;

            while (queue.Count > 0)
            {
                // Pop a node
                RoadNode node = queue.Dequeue();
                visitedNodes.Add(node.Id);

                // Generate intersection
                GenerateIntersection(node);

                // Enqueue
                foreach (var segment in node.ArticulationSegments)
                {
                    // Generate segments linked to node that have been visited
                    if (visitedNodes.Contains(segment.Terminal1Id) && visitedNodes.Contains(segment.Terminal2Id))
                    {
                        if (!visitedSegments.Contains(segment.Id))
                        {
                            GenerateSegment(segment);
                            visitedSegments.Add(segment.Id);
                        }
                    }
                    else
                    {
                        if (node == segment.Terminal1)
                            queue.Enqueue(segment.Terminal2);
                        else queue.Enqueue(segment.Terminal1);
                    }
                }

                // Take a break
                ++i;
                if (i % 20 == 0)
                    yield return null;
            }

            Logger.Info("Finished generating road mesh.");
        }

        private int LanesTo(RoadSegment segment, RoadNode terminal)
        {
            if (segment.Terminal1 == terminal)
                return segment.LanesTo1;

            if (segment.Terminal2 == terminal)
                return segment.LanesTo2;

            return -1;
        }

        private int LanesFrom(RoadSegment segment, RoadNode terminal)
        {
            if (segment.Terminal1 == terminal)
                return segment.LanesTo2;

            if (segment.Terminal2 == terminal)
                return segment.LanesTo1;

            return -1;
        }

        private Vector2 DirectionFrom(RoadSegment segment, RoadNode terminal)
        {
            return (segment.Terminal1 == terminal) ? segment.Direction : -segment.Direction;
        }

        public void GenerateIntersection(RoadNode node)
        {
            List<Vector3> vertices = new List<Vector3>();
            List<UnityEngine.Vector2> uv = new List<UnityEngine.Vector2>();
            List<int> triangles = new List<int>();
            int vindex = 0;

            // Helper function
            Action<Vector2, float> addV = (v, h) => 
            {
                Vector3 v3 = new Vector3(v.Y, map.GetHeight((int)node.X, (int)node.Y) + RaiseOffset + h, v.X);
                UnityEngine.Vector2 v2 = new UnityEngine.Vector2(v.Y / 3 - v3.y, v.X / 3 - v3.y);

                vertices.Add(v3);
                uv.Add(v2);
            };

            // Add current node
            addV(node.Position, 0);
            vindex += 1;

            // Sort adjacent segments in trigonometric order
            var segs = node.ArticulationSegments.OrderBy(segment =>
                {
                    Vector2 dir = DirectionFrom(segment, node);

                    if (dir.X >= 0 && dir.Y >= 0)       // First quadrant:
                        return dir.Y;                   // Y coordinate grows from 0 to 1

                    else if (dir.X <= 0 && dir.Y >= 0)  // Second quadrant:
                        return 1 + Math.Abs(dir.X);     // X goes from 0 to -1

                    else if (dir.X <= 0 && dir.Y <= 0)  // Third quadrant:
                        return 2 + Math.Abs(dir.Y);     // Y goes from 0 to -1

                    else return 3 + dir.X;              // Fourth quadrant: X grows from 0 to 1
                }).ToArray();

            Vector2[] sideCrns = new Vector2[segs.Length];
            Vector2[] strCrns = new Vector2[segs.Length];

            // Holds intersection points for perpendicular on segment that goes through sidewalk corners
            // 0, 1, 2, 3 - 0 sidewalk, 1 street, 2 street, 3 sidewalk (in trigonometric order). (when first segment)
            // 4, 5, 6, 7 - the same (when second segment)
            Vector2[,] p = new Vector2[8, segs.Length]; 

            // Process each pair of segments
            for (int i = 0; i < segs.Length; ++i)
            {
                // Wrap around
                int j = i + 1;
                if (j >= segs.Length)
                    j = 0;

                // Get direction vectors
                var dir0 = DirectionFrom(segs[i], node);
                var dir1 = DirectionFrom(segs[j], node);
                float cross = Vector2.Cross(dir0, dir1);

                // Colliniar vectors
                if (Math.Abs(cross) < 1e-2)
                {
                    var dirP = dir0.RotateDeg(90);

                    strCrns[i] = node.Position + dirP * LanesTo(segs[i], node) * LaneWidth;
                    sideCrns[i] = strCrns[i] + dirP * SidewalkWidth;
                }

                // Vectors not colliniar
                else
                {
                    Vector2 off0 = dir0 * ((LanesFrom(segs[j], node) * LaneWidth) / cross);
                    Vector2 off1 = dir1 * ((LanesTo(segs[i], node) * LaneWidth) / cross);
                    strCrns[i] = node.Position + off0 + off1;
                    sideCrns[i] = strCrns[i] + dir0 * (SidewalkWidth / cross) + dir1 * (SidewalkWidth / cross);
                }

                // Calculate perpendicular vectors from sidewalk corner on first segment
                Vector2 perp0 = dir0.RotateDeg(-90);
                p[3, i] = sideCrns[i];
                p[2, i] = p[3, i] + perp0 * SidewalkWidth;
                p[1, i] = p[2, i] + perp0 * (segs[i].LanesTo1 + segs[i].LanesTo2) * LaneWidth;
                p[0, i] = p[1, i] + perp0 * SidewalkWidth;

                // Calculate perpendicular vectors from sidewalk corner on second segment
                Vector2 perp1 = dir1.RotateDeg(90);
                p[4, j] = sideCrns[i];
                p[5, j] = p[4, j] + perp1 * SidewalkWidth;
                p[6, j] = p[5, j] + perp1 * (segs[j].LanesTo1 + segs[j].LanesTo2) * LaneWidth;
                p[7, j] = p[6, j] + perp1 * SidewalkWidth;
            }

            if (segs.Length == 1)
            {
                var dir = DirectionFrom(segs[0], node);
                Vector2 perp = dir.RotateDeg(-90);
                Vector2[] end = new[] { 
                    node.Position + perp * (LanesFrom(segs[0], node) * LaneWidth + SidewalkWidth),
                    node.Position + perp * (LanesFrom(segs[0], node) * LaneWidth),
                    node.Position - perp * (LanesTo(segs[0], node) * LaneWidth),
                    node.Position - perp * (LanesTo(segs[0], node) * LaneWidth + SidewalkWidth)
                };

                if (segs[0].Terminal1 == node)
                {
                    segmentTerminal1Limit[segs[0].Id] = end;
                }
                else
                {
                    segmentTerminal2Limit[segs[0].Id] = end;
                }
            }
            else
            {

                // Now we generate for each segment
                for (int i = 0; i < segs.Length; i++)
                {
                    // Find furthest perpendicular
                    float dist0 = (p[0, i] - node.Position).LengthSq;
                    float dist1 = (p[4, i] - node.Position).LengthSq;

                    int furth = (dist0 > dist1) ? 0 : 4;
                    int cornerLeft = i;
                    int cornerRight = (i - 1 >= 0) ? i - 1 : segs.Length - 1;

                    // Add to limit dictionaries
                    if (segs[i].Terminal1 == node)
                    {
                        segmentTerminal1Limit[segs[i].Id] = new[] { p[furth, i], p[furth + 1, i], p[furth + 2, i], p[furth + 3, i] };
                    }
                    else
                    {
                        segmentTerminal2Limit[segs[i].Id] = new[] { p[furth, i], p[furth + 1, i], p[furth + 2, i], p[furth + 3, i] };
                    }

                    // Build road
                    // Right side
                    addV(p[furth, i], SidewalkHeight);                                  // 0 - p0 raised
                    addV(sideCrns[cornerRight], SidewalkHeight);                        // 1 - side corner raised
                    addV(sideCrns[cornerRight], SidewalkHeight - SideCoverHeight);      // 2 - side corner cover
                    addV(p[furth, i], SidewalkHeight - SideCoverHeight);                // 3 - p0 cover
                    addV(p[furth + 1, i], SidewalkHeight);                              // 4 - p1 raised
                    addV(strCrns[cornerRight], SidewalkHeight);                         // 5 - street corner raised
                    addV(strCrns[cornerRight], 0);                                      // 6 - street corner
                    addV(p[furth + 1, i], 0);                                           // 7 - p1

                    // Left side
                    addV(p[furth + 2, i], 0);                                           // 8 - p2
                    addV(strCrns[cornerLeft], 0);                                       // 9 - street corner
                    addV(strCrns[cornerLeft], SidewalkHeight);                          //10 - street corner raised
                    addV(p[furth + 2, i], SidewalkHeight);                              //11 - p2 raised
                    addV(p[furth + 3, i], SidewalkHeight - SideCoverHeight);            //12 - p3 cover
                    addV(sideCrns[cornerLeft], SidewalkHeight - SideCoverHeight);       //13 - side corner cover
                    addV(sideCrns[cornerLeft], SidewalkHeight);                         //14 - side corner raised
                    addV(p[furth + 3, i], SidewalkHeight);                              //15 - p3 raised

                    // Right sidewalk
                    triangles.AddRange(new[] { vindex, vindex + 1, vindex + 2 });       // sidewalk side cover 0
                    triangles.AddRange(new[] { vindex, vindex + 2, vindex + 3 });       // sidewalk side cover 1
                    triangles.AddRange(new[] { vindex, vindex + 4, vindex + 1 });       // sidewalk surface 0
                    triangles.AddRange(new[] { vindex + 4, vindex + 5, vindex + 1 });   // sidewalk surface 1
                    triangles.AddRange(new[] { vindex + 4, vindex + 7, vindex + 6 });   // sidewalk road raise 0
                    triangles.AddRange(new[] { vindex + 4, vindex + 6, vindex + 5 });   // sidewalk road raise 1

                    // Road surface
                    triangles.AddRange(new[] { vindex + 8, vindex + 6, vindex + 7 });   // road surface 0
                    triangles.AddRange(new[] { vindex + 8, vindex + 9, vindex + 6 });   // road surface 0
                    triangles.AddRange(new[] { vindex + 6, vindex + 9, 0 });            // road surface 0

                    // Left sidewalk
                    triangles.AddRange(new[] { vindex + 11, vindex + 10, vindex + 9 }); // sidewalk road raise 0
                    triangles.AddRange(new[] { vindex + 11, vindex + 9, vindex + 8 });  // sidewalk road raise 1
                    triangles.AddRange(new[] { vindex + 11, vindex + 14, vindex + 10 });// sidewalk surface 0
                    triangles.AddRange(new[] { vindex + 11, vindex + 15, vindex + 14 });// sidewalk surface 1
                    triangles.AddRange(new[] { vindex + 15, vindex + 12, vindex + 13 });// sidewalk side cover 0
                    triangles.AddRange(new[] { vindex + 15, vindex + 13, vindex + 14 });// sidewalk side cover 1

                    // update vindex
                    vindex = vertices.Count;
                }

                // Construct mesh
                Mesh mesh = new Mesh();
                mesh.vertices = vertices.ToArray();
                mesh.triangles = triangles.ToArray();
                mesh.uv = uv.ToArray();
                mesh.RecalculateNormals();

                // Construct game object
                GameObject inters = new GameObject("intersection" + node.Id);
                inters.transform.parent = parent.transform;

                MeshFilter meshFilter = inters.AddComponent<MeshFilter>();
                meshFilter.mesh = mesh;

                MeshRenderer meshRenderer = inters.AddComponent<MeshRenderer>();
                meshRenderer.materials = new[] { RoadMaterial };
            }

#if DEBUG_ROAD_MESH_GENERATOR
            // Debug draw
            Debug.DrawLine(
                new Vector3(node.Y, map.GetHeight((int)node.X, (int)node.Y) + 0.5f, node.X),
                new Vector3(node.Y, map.GetHeight((int)node.X, (int)node.Y) + 1.2f, node.X),
                Color.white, 10000);

            foreach (var sidewalkCorner in sideCrns)
                Debug.DrawLine(
                    new Vector3(sidewalkCorner.Y, map.GetHeight((int)sidewalkCorner.X, (int)sidewalkCorner.Y) + 0.5f, sidewalkCorner.X),
                    new Vector3(sidewalkCorner.Y, map.GetHeight((int)sidewalkCorner.X, (int)sidewalkCorner.Y) + 1.1f, sidewalkCorner.X),
                    Color.cyan, 10000);

            foreach (var strCorner in strCrns)
                Debug.DrawLine(
                    new Vector3(strCorner.Y, map.GetHeight((int)strCorner.X, (int)strCorner.Y) + 0.5f, strCorner.X),
                    new Vector3(strCorner.Y, map.GetHeight((int)strCorner.X, (int)strCorner.Y) + 1.1f, strCorner.X),
                    Color.blue, 10000);

            for (int i = 0; i < segs.Length; i++)
                for (int j = 0; j < 8; j++)
                    Debug.DrawLine(
                        new Vector3(p[j, i].Y, map.GetHeight((int)p[j, i].X, (int)p[j, i].Y) + 0.5f, p[j, i].X),
                        new Vector3(p[j, i].Y, map.GetHeight((int)p[j, i].X, (int)p[j, i].Y) + 1.0f, p[j, i].X),
                        Color.green, 10000);
#endif
        }

        public void GenerateSegment(RoadSegment s)
        {
            List<Vector3> vertices = new List<Vector3>();
            List<UnityEngine.Vector2> uv = new List<UnityEngine.Vector2>();
            List<int> triangles = new List<int>();

            // Helper function
            Action<Vector2, float, int> addV = (v, h, term) =>
            {
                if (term == 1)
                    h += map.GetHeight((int)s.Terminal1.X, (int)s.Terminal1.Y);
                else
                    h += map.GetHeight((int)s.Terminal2.X, (int)s.Terminal2.Y);

                Vector3 v3 = new Vector3(v.Y, RaiseOffset + h, v.X);
                UnityEngine.Vector2 v2 = new UnityEngine.Vector2(v.Y / 3 - v3.y, v.X / 3 - v3.y);

                vertices.Add(v3);
                uv.Add(v2);
            };

            Vector2[] pT1 = segmentTerminal1Limit[s.Id];
            Vector2[] pT2 = segmentTerminal2Limit[s.Id];
            
            addV(pT1[0], SidewalkHeight - SideCoverHeight, 1);
            addV(pT1[0], SidewalkHeight, 1);
            addV(pT1[1], SidewalkHeight, 1);
            addV(pT1[1], 0, 1);
            addV(pT1[2], 0, 1);
            addV(pT1[2], SidewalkHeight, 1);
            addV(pT1[3], SidewalkHeight, 1);
            addV(pT1[3], SidewalkHeight - SideCoverHeight, 1);

            addV(pT2[0], SidewalkHeight - SideCoverHeight, 2);
            addV(pT2[0], SidewalkHeight, 2);
            addV(pT2[1], SidewalkHeight, 2);
            addV(pT2[1], 0, 2);
            addV(pT2[2], 0, 2);
            addV(pT2[2], SidewalkHeight, 2);
            addV(pT2[3], SidewalkHeight, 2);
            addV(pT2[3], SidewalkHeight - SideCoverHeight, 2);

            triangles.AddRange(new[] { 0, 15, 14 });       // sidewalk side cover 0
            triangles.AddRange(new[] { 0, 14, 1 });       // sidewalk side cover 1
            triangles.AddRange(new[] { 1, 14, 13 });       // sidewalk surface 0
            triangles.AddRange(new[] { 1, 13, 2 });   // sidewalk surface 1
            triangles.AddRange(new[] { 2, 12, 3 });   // sidewalk road raise 0
            triangles.AddRange(new[] { 2, 13, 12 });   // sidewalk road raise 1

            // Road surface
            triangles.AddRange(new[] { 3, 12, 11 });   // road surface 0
            triangles.AddRange(new[] { 3, 11, 4 });   // road surface 0

            // Left sidewalk
            triangles.AddRange(new[] { 4, 11, 10 }); // sidewalk road raise 0
            triangles.AddRange(new[] { 4, 10, 5 });  // sidewalk road raise 1
            triangles.AddRange(new[] { 5, 10, 9 }); // sidewalk surface 0
            triangles.AddRange(new[] { 5, 9, 6 });  // sidewalk surface 1
            triangles.AddRange(new[] { 6, 9, 8 });  // sidewalk side cover 0
            triangles.AddRange(new[] { 6, 8, 7 });  // sidewalk side cover 1

            // Construct mesh
            Mesh mesh = new Mesh();
            mesh.vertices = vertices.ToArray();
            mesh.triangles = triangles.ToArray();
            mesh.uv = uv.ToArray();
            mesh.RecalculateNormals();

            // Construct game object
            GameObject inters = new GameObject("road" + s.Id);
            inters.transform.parent = parent.transform;

            MeshFilter meshFilter = inters.AddComponent<MeshFilter>();
            meshFilter.mesh = mesh;

            MeshRenderer meshRenderer = inters.AddComponent<MeshRenderer>();
            meshRenderer.materials = new[] { RoadMaterial };

#if DEBUG_ROAD_MESH_GENERATOR
            // Debug draw
            Color color = (s.LanesTo1 >= 3) ? Color.magenta : Color.red;
            Debug.DrawLine(
                new Vector3(s.Terminal1.Y, map.GetHeight((int)s.Terminal1.X, (int)s.Terminal1.Y) + 1f, s.Terminal1.X),
                new Vector3(s.Terminal2.Y, map.GetHeight((int)s.Terminal2.X, (int)s.Terminal2.Y) + 1f, s.Terminal2.X),
                color, 10000);
#endif
        }
    }
}