using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using Microsoft.Msagl.Core.Geometry;

namespace Microsoft.Msagl.Layout.Layered {
    /// <summary>
    /// Following "Improving Layered Graph Layouts with Edge Bundling" and
    /// "Two polynomial time algorithms for the bundle-Line crossing minimization problem"
    /// Postprocessing minimizing crossings step that works on the layered graph
    /// </summary>
    internal class MetroMapOrdering {
        LayerArrays layerArrays;
        Dictionary<int, Point> nodePositions;
        ProperLayeredGraph properLayeredGraph;

        MetroMapOrdering(ProperLayeredGraph properLayeredGraph, LayerArrays layerArrays,
                         Dictionary<int, Point> nodePositions) {
            this.properLayeredGraph = properLayeredGraph;
            this.layerArrays = layerArrays;
            this.nodePositions = nodePositions;
        }

        /// <summary>
        /// Reorder only points having identical nodePositions
        /// </summary>
        internal static void UpdateLayerArrays(ProperLayeredGraph properLayeredGraph, LayerArrays layerArrays,
                                               Dictionary<int, Point> nodePositions) {
            new MetroMapOrdering(properLayeredGraph, layerArrays, nodePositions).UpdateLayerArrays();
        }

        /// <summary>
        /// Reorder virtual nodes between the same pair of real nodes
        /// </summary>
        internal static void UpdateLayerArrays(ProperLayeredGraph properLayeredGraph, LayerArrays layerArrays) {
            Dictionary<int, Point> nodePositions = BuildInitialNodePositions(properLayeredGraph, layerArrays);
            UpdateLayerArrays(properLayeredGraph, layerArrays, nodePositions);
        }

        static Dictionary<int, Point> BuildInitialNodePositions(ProperLayeredGraph properLayeredGraph,
                                                                LayerArrays layerArrays) {
            var result = new Dictionary<int, Point>();
            for (int i = 0; i < layerArrays.Layers.Length; i++) {
                int prev = 0, curr = 0;
                while (curr < layerArrays.Layers[i].Length) {
                    while (curr < layerArrays.Layers[i].Length &&
                           properLayeredGraph.IsVirtualNode(layerArrays.Layers[i][curr])) curr++;
                    for (int j = prev; j < curr; j++)
                        result[layerArrays.Layers[i][j]] = new Point(i, prev);

                    if (curr < layerArrays.Layers[i].Length)
                        result[layerArrays.Layers[i][curr]] = new Point(i, curr);
                    curr++;
                    prev = curr;
                }
            }

            return result;
        }

        void UpdateLayerArrays() {
#if TEST_MSAGL
            //    int initialCrossingNumber = Ordering.GetCrossingsTotal(properLayeredGraph, layerArrays);
#endif

            //algo stuff here
            Dictionary<Point, List<int>> ordering = CreateInitialOrdering();
            ordering = BuildOrdering(ordering);
            RestoreLayerArrays(ordering);

#if TEST_MSAGL
//            int finalCrossingNumber = Ordering.GetCrossingsTotal(properLayeredGraph, layerArrays);
//            double gain = (initialCrossingNumber > 0 ? (double)(initialCrossingNumber - finalCrossingNumber) / initialCrossingNumber * 100.0 : 0);
//            Console.WriteLine("Crossing number reduced on {0:0.00}% (initial:{1}, final:{2})", gain, initialCrossingNumber, finalCrossingNumber);
#endif
        }

        Dictionary<Point, List<int>> CreateInitialOrdering() {
            var initialOrdering = new Dictionary<Point, List<int>>();
            for (int i = 0; i < layerArrays.Layers.Length; i++)
                for (int j = 0; j < layerArrays.Layers[i].Length; j++) {
                    int node = layerArrays.Layers[i][j];
                    if (!initialOrdering.ContainsKey(nodePositions[node]))
                        initialOrdering[nodePositions[node]] = new List<int>();
                    initialOrdering[nodePositions[node]].Add(node);
                }

            return initialOrdering;
        }


        Dictionary<Point, List<int>> BuildOrdering(Dictionary<Point, List<int>> initialOrdering) {
            //run through nodes points and build order
            var result = new Dictionary<Point, List<int>>();
            var reverseOrder = new Dictionary<int, int>();
            for (int i = 0; i < layerArrays.Layers.Length; i++)
                for (int j = 0; j < layerArrays.Layers[i].Length; j++) {
                    int node = layerArrays.Layers[i][j];

                    //already processed
                    if (result.ContainsKey(nodePositions[node])) continue;

                    result[nodePositions[node]] = BuildNodeOrdering(initialOrdering[nodePositions[node]], reverseOrder);
                }

            return result;
        }

        List<int> BuildNodeOrdering(List<int> nodeOrdering, Dictionary<int, int> inverseToOrder) {
            List<int> result = nodeOrdering;

            result.Sort(Comparison(inverseToOrder));

            for (int i = 0; i < result.Count; i++)
                inverseToOrder[result[i]] = i;
            return result;
        }

        Comparison<int> Comparison(Dictionary<int, int> inverseToOrder) {
            return delegate(int node1, int node2) {
                       Debug.Assert(properLayeredGraph.IsVirtualNode(node1) &&
                                    properLayeredGraph.IsVirtualNode(node2));

                       int succ1 = properLayeredGraph.Succ(node1).ElementAt(0);
                       int succ2 = properLayeredGraph.Succ(node2).ElementAt(0);
                       int pred1 = properLayeredGraph.Pred(node1).ElementAt(0);
                       int pred2 = properLayeredGraph.Pred(node2).ElementAt(0);

                       Point succPoint1 = nodePositions[succ1];
                       Point succPoint2 = nodePositions[succ2];
                       Point predPoint1 = nodePositions[pred1];
                       Point predPoint2 = nodePositions[pred2];

                       if (succPoint1 != succPoint2) {
                           if (predPoint1 != predPoint2)
                               return predPoint1.CompareTo(predPoint2);
                           return succPoint1.CompareTo(succPoint2);
                       }
                       if (properLayeredGraph.IsVirtualNode(succ1)) {
                           if (predPoint1 != predPoint2)
                               return predPoint1.CompareTo(predPoint2);

                           int o1 = inverseToOrder[succ1];
                           int o2 = inverseToOrder[succ2];
                           Debug.Assert(o1 != -1 && o2 != -1);
                           return (o1.CompareTo(o2));
                       }
                       while (nodePositions[pred1] == nodePositions[pred2] &&
                              properLayeredGraph.IsVirtualNode(pred1)) {
                           pred1 = properLayeredGraph.Pred(pred1).ElementAt(0);
                           pred2 = properLayeredGraph.Pred(pred2).ElementAt(0);
                       }

                       if (nodePositions[pred1] == nodePositions[pred2])
                           return node1.CompareTo(node2);
                       return nodePositions[pred1].CompareTo(nodePositions[pred2]);
                   };
        }

        void RestoreLayerArrays(Dictionary<Point, List<int>> ordering) {
            for (int i = 0; i < layerArrays.Layers.Length; i++) {
                int pred = 0, tec = 0;
                while (tec < layerArrays.Layers[i].Length) {
                    while (tec < layerArrays.Layers[i].Length &&
                           nodePositions[layerArrays.Layers[i][pred]] == nodePositions[layerArrays.Layers[i][tec]])
                        tec++;
                    for (int j = pred; j < tec; j++)
                        layerArrays.Layers[i][j] = ordering[nodePositions[layerArrays.Layers[i][j]]][j - pred];
                    pred = tec;
                }
            }

            layerArrays.UpdateXFromLayers();
        }
    }
}