///
/// Copyright (c) 2020-2021 Sensus Slovensko a.s.
///
using System;
using System.Collections.Generic;

namespace SchematicDrawing
{
    public class Pipe
    {
        public IDrawingItem StartItem;
        public int StartNodeId;
        public IDrawingItem EndItem;
        public int EndNodeId;
        public Sz Sz;

        public bool CoordinatesAreValid;
        public int x1, y1, x2, y2;
        public bool HasIntersection;
        public float P;


        public Pipe(IDrawingItem startItem, int startNodeId, IDrawingItem endItem, int endNodeId, Sz sz)
        {
            StartItem = startItem;
            StartNodeId = startNodeId;
            EndItem = endItem;
            EndNodeId = endNodeId;
            Sz = sz;
            CoordinatesAreValid = false;
            HasIntersection = false;
        }

        public Pipe(string pipeStr, Sz sz, Dictionary<int, IDrawingItem> id2Item)
        {
            String2Items(pipeStr, id2Item, out StartItem, out StartNodeId, out EndItem, out EndNodeId);
            Sz = sz;
            CoordinatesAreValid = false;
            HasIntersection = false;
        }

        public override string ToString()
        {
            return (StartItem != null && EndItem != null) ? string.Format("{0}~{1}~{2}~{3}", StartItem.Id, StartNodeId, EndItem.Id, EndNodeId) : string.Empty;
        }


        /// <summary>
        /// Calculates coordinates of the start- and the end-point
        /// </summary>
        /// <param name="x1">Start point X</param>
        /// <param name="y1">Start point Y</param>
        /// <param name="x2">End point X</param>
        /// <param name="y2">End point Y</param>
        /// <returns>true when calculation successful</returns>
        public bool GetCoordinates()
        {
            DrawingShape startDShape = DrawingShape.GetDrawingShape(StartItem);
            DrawingShape endDShape = DrawingShape.GetDrawingShape(EndItem);

            if (StartItem != null && EndItem != null && startDShape != null && endDShape != null)
            {
                Node startNode = startDShape.GetRotatedFlippedNode(StartItem, StartNodeId);
                Node endNode = endDShape.GetRotatedFlippedNode(EndItem, EndNodeId);

                x1 = StartItem.X + startNode.X * Const.GridSize;
                y1 = StartItem.Y + startNode.Y * Const.GridSize;
                x2 = EndItem.X + endNode.X * Const.GridSize;
                y2 = EndItem.Y + endNode.Y * Const.GridSize;
                CoordinatesAreValid = true;

                return true;
            }
            else
            {
                return false;
            }
        }

        /// <summary>
        /// Converts pipe string to start and end items
        /// </summary>
        /// <param name="pipeStr">Edge string</param>
        /// <param name="name2Item">Dictionary of items</param>
        /// <param name="startItem">Start item</param>
        /// <param name="endItem">End item</param>
        /// <returns>true when conversion successful</returns>
        public static bool String2Items(string pipeStr, Dictionary<int, IDrawingItem> id2Item, out IDrawingItem startItem, out int startNid, out IDrawingItem endItem, out int endNid)
        {
            string[] fields = pipeStr.Split(new char[] { '~' });

            int startId, endId;
            IDrawingItem start, end;
            DrawingShape dshapeFrom, dshapeTo;
            if (fields.Length == 4 && int.TryParse(fields[0], out startId) && id2Item.TryGetValue(startId, out start)
                 && (null != (dshapeFrom = DrawingShape.Shapes[DrawingShape.DrShIx(start.Shape, start.Sz)]))
                 && int.TryParse(fields[1], out startNid) && (startNid >= 0) && (startNid < dshapeFrom.Nodes.Length)
                 && int.TryParse(fields[2], out endId) && id2Item.TryGetValue(endId, out end)
                 && (null != (dshapeTo = DrawingShape.Shapes[DrawingShape.DrShIx(end.Shape, end.Sz)]))
                 && int.TryParse(fields[3], out endNid) && (endNid >= 0) && (endNid < dshapeTo.Nodes.Length))
            {
                startItem = start;
                endItem = end;
                return true;
            }

            startItem = null;
            endItem = null;
            startNid = 0;
            endNid = 0;
            return false;
        }

        /// <summary>
        /// Returns true when two pipes have an intersection
        /// </summary>
        /// <param name="pipe2">Second pipe</param>
        /// <returns>true when ipes intersect</returns>
        public bool CalculateIntersectionWith(Pipe pipe2)
        {
            if (!this.CoordinatesAreValid) GetCoordinates();
            if (!pipe2.CoordinatesAreValid) pipe2.GetCoordinates();

            int D = (x2 - x1) * (pipe2.y2 - pipe2.y1) - (y2 - y1) * (pipe2.x2 - pipe2.x1);
            float Dp = Convert.ToSingle((pipe2.x1 - x1) * (pipe2.y2 - pipe2.y1) - (pipe2.y1 - y1) * (pipe2.x2 - pipe2.x1));
            float Dq = Convert.ToSingle((x2 - x1) * (pipe2.y1 - y1) - (y2 - y1) * (pipe2.x1 - x1));

            if (D == 0)
            {
                return false;       /// Parallel pipes -> no intersection
            }

            float Df = Convert.ToSingle(D);
            float p = Dp / Df;
            float q = -Dq / Df;
            if (p > 0.01 && p < 0.99 && q > 0.01 && q < 0.99)
            {
                this.HasIntersection = true;
                this.P = p;
                return true;        /// Pipes intersect, pipes touching by their ends are not considered
            }

            return false;           /// Pipes do not intersect
        }
    }
}