/*
*  Copyright (C) 1998-2023 by Northwoods Software Corporation. All Rights Reserved.
*/

/*
* This is an extension and not part of the main GoJS library.
* Note that the API for this class may change with any version, even point releases.
* If you intend to use an extension in production, you should copy the code to your own source directory.
* Extensions can be found in the GoJS kit under the extensions or extensionsJSM folders.
* See the Extensions intro page (https://gojs.net/latest/intro/extensions.html) for more information.
*/

import * as go from '../release/go-module.js';

/**
 * A custom {@link TreeLayout} that can be used for laying out stylized flowcharts.
 * Each layout requires a single "Split" node and a single "Merge" node.
 * The "Split" node should be the root of a tree-like structure if one excludes links to the "Merge" node.
 * This will position the "Merge" node to line up with the "Split" node.
 *
 * You can set all of the TreeLayout properties that you like,
 * except that for simplicity this code just works for angle === 0 or angle === 90.
 *
 * If you want to experiment with this extension, try the <a href="../../extensionsJSM/Parallel.html">Parallel Layout</a> sample.
 * @category Layout Extension
 */
export class ParallelLayout extends go.TreeLayout {
  private _splitNode: go.Node | null = null;
  private _mergeNode: go.Node | null = null;

  /**
   * Constructs a ParallelLayout and sets the following properties:
   *   - {@link #isRealtime} = false
   *   - {@link #alignment} = {@link TreeLayout.AlignmentCenterChildren}
   *   - {@link #compaction} = {@link TreeLayout.CompactionNone}
   *   - {@link #alternateAlignment} = {@link TreeLayout.AlignmentCenterChildren}
   *   - {@link #alternateCompaction} = {@link TreeLayout.CompactionNone}
   */
  constructor() {
    super();
    this.isRealtime = false;
    this.alignment = go.TreeLayout.AlignmentCenterChildren;
    this.compaction = go.TreeLayout.CompactionNone;
    this.alternateAlignment = go.TreeLayout.AlignmentCenterChildren;
    this.alternateCompaction = go.TreeLayout.CompactionNone;
  }

  /**
   * This read-only property returns the node that the tree will extend from.
   */
  get splitNode(): go.Node | null { return this._splitNode; }
  set splitNode(val: go.Node | null) { this._splitNode = val; }

  /**
   * This read-only property returns the node that the tree will converge at.
   */
  get mergeNode(): go.Node | null { return this._mergeNode; }
  set mergeNode(val: go.Node | null) { this._mergeNode = val; }

  /**
   * Overridable predicate for deciding if a Node is a Split node.
   * By default this checks the node's {@link Part#category} to see if it is
   * "Split", "Start", "For", "While", "If", or "Switch".
   * @param {Node} node
   * @return {boolean}
   */
  isSplit(node: go.Node | null): boolean {
    if (!(node instanceof go.Node)) return false;
    var cat = node.category;
    return (cat === "Split" || cat === "Start" || cat === "For" || cat === "While" || cat === "If" || cat === "Switch");
  }

  /**
   * Overridable predicate for deciding if a Node is a Merge node.
   * By default this checks the node's {@link Part#category} to see if it is
   * "Merge", "End", "EndFor", "EndWhile", "EndIf", or "EndSwitch".
   * @param {Node} node
   * @return {boolean}
   */
  isMerge(node: go.Node | null): boolean {
    if (!(node instanceof go.Node)) return false;
    var cat = node.category;
    return (cat === "Merge" || cat === "End" || cat === "EndFor" || cat === "EndWhile" || cat === "EndIf" || cat === "EndSwitch");
  }

  /**
   * Overridable predicate for deciding if a Node is a conditional or "If" type of Split Node
   * expecting to have two links coming out of the sides.
   * @param {Node} node
   * @return {boolean}
   */
  isConditional(node: go.Node | null): boolean {
    if (!(node instanceof go.Node)) return false;
    return node.category === "If";
  }

  /**
   * Overridable predicate for deciding if a Node is a "Switch" type of Split Node
   * expecting to have three links coming out of the bottom/right side.
   * @param {Node} node
   * @return {boolean}
   */
  isSwitch(node: go.Node | null): boolean {
    if (!(node instanceof go.Node)) return false;
    return node.category === "Switch";
  }

  /**
   * Find a Split vertex and a Merge vertex for this layout.
   * This signals an error if there is not exactly one vertex/Node that {@link #isSplit}
   * and exactly one vertex/Node that {@link #isMerge}.
   * This can be overridden; any override must set {@link #splitNode} and {@link #mergeNode}.
   * @param {Iterable<TreeVertex>} vertexes
   */
  findSplitMerge(vertexes: go.Iterable<go.TreeVertex>): void {
    var split = null;
    var merge = null;
    var it = vertexes.iterator;
    while (it.next()) {
      var v = it.value;
      if (!v.node) continue;
      if (this.isSplit(v.node)) {
        if (split) throw new Error("Split node already exists in " + this + " -- existing: " + split + " new: " + v.node);
        split = v.node;
      } else if (this.isMerge(v.node)) {
        if (merge) throw new Error("Merge node already exists in " + this + " -- existing: " + merge + " new: " + v.node);
        merge = v.node;
      }
    }
    if (!split) throw new Error("Missing Split node in " + this);
    if (!merge) throw new Error("Missing Merge node in " + this);
    this._splitNode = split;
    this._mergeNode = merge;
  }

  /**
   * @hidden @internal
   */
  public override makeNetwork(coll: go.Iterable<go.Part>): go.TreeNetwork {
    const net = super.makeNetwork(coll) as go.TreeNetwork;
    // Groups might be unbalanced -- position them so that the Split node is centered under the parent node.
    var it = net.vertexes.iterator;
    while (it.next()) {
      var v = it.value;
      var g = v.node;
      if (g instanceof go.Group && g.isSubGraphExpanded && g.placeholder !== null && g.layout instanceof ParallelLayout) {
        var split = g.layout.splitNode;
        if (split) {
          if (this.angle === 0) {
            v.focusY = split.location.y - g.position.y;
          } else if (this.angle === 90) {
            v.focusX = split.location.x - g.position.x;
          }
        }
      }
    }
    if (this.group && !this.group.isSubGraphExpanded) return net;
    // look for and remember the one Split node and the one Merge node
    this.findSplitMerge(net.vertexes.iterator as go.Iterator<go.TreeVertex>);
    // don't have TreeLayout lay out the Merge node; commitNodes will do it
    if (this.mergeNode) net.deleteNode(this.mergeNode);
    // for each vertex that does not have an incoming edge,
    // connect to it from the splitNode vertex with a dummy edge
    if (this.splitNode) {
      var splitv = net.findVertex(this.splitNode);
      net.vertexes.each(v => {
        if (splitv === null || v === splitv) return;
        if (v.sourceEdges.count === 0) {
          net.linkVertexes(splitv, v, null);
        }
      });
    }
    return net;
  }

  /**
   * @hidden @internal
   */
  public override commitNodes(): void {
    super.commitNodes();
    // Line up the Merge node to the center of the Split node
    var mergeNode = this.mergeNode;
    var splitNode = this.splitNode;
    if (mergeNode === null || splitNode === null || this.network === null) return;
    var splitVertex = this.network.findVertex(splitNode) as go.TreeVertex;
    if (splitVertex === null) return;
    if (this.angle === 0) {
      mergeNode.location = new go.Point(splitVertex.x + splitVertex.subtreeSize.width + this.layerSpacing + mergeNode.actualBounds.width/2,
                                        splitVertex.centerY);
    } else if (this.angle === 90) {
      mergeNode.location = new go.Point(splitVertex.centerX,
                                        splitVertex.y + splitVertex.subtreeSize.height + this.layerSpacing + mergeNode.actualBounds.height/2);
    }
    mergeNode.ensureBounds();
  }

  /**
   * @hidden @internal
   */
  public override commitLinks(): void {
    const splitNode = this.splitNode;
    const mergeNode = this.mergeNode;
    if (splitNode === null || mergeNode === null || this.network === null) return;
    // set default link spots based on this.angle
    const it = this.network.edges.iterator;
    while (it.next()) {
      const e = it.value;
      const link = e.link;
      if (!link) continue;
      if (this.angle === 0) {
        if (this.setsPortSpot) link.fromSpot = go.Spot.Right;
        if (this.setsChildPortSpot) link.toSpot = go.Spot.Left;
      } else if (this.angle === 90) {
        if (this.setsPortSpot) link.fromSpot = go.Spot.Bottom;
        if (this.setsChildPortSpot) link.toSpot = go.Spot.Top;
      }
    }
    // Make sure links coming into and going out of a Split node come in the correct way
    if (splitNode) {
      // Handle links coming into the Split node
      const cond = this.isConditional(splitNode);
      const swtch = this.isSwitch(splitNode);
      // Handle links going out of the Split node
      let first = true;  // handle "If" nodes specially
      const lit = splitNode.findLinksOutOf();
      while (lit.next()) {
        const link = lit.value;
        if (this.angle === 0) {
          if (this.setsPortSpot) link.fromSpot = cond ? (first ? go.Spot.Top : go.Spot.Bottom) : (swtch ? go.Spot.RightSide : go.Spot.Right);
          if (this.setsChildPortSpot) link.toSpot = go.Spot.Left;
        } else if (this.angle === 90) {
          if (this.setsPortSpot) link.fromSpot = cond ? (first ? go.Spot.Left : go.Spot.Right) : (swtch ? go.Spot.BottomSide : go.Spot.Bottom);
          if (this.setsChildPortSpot) link.toSpot = go.Spot.Top;
        }
        first = false;
      }
    }
    if (mergeNode) {
      // Handle links going into the Merge node
      const iit = mergeNode.findLinksInto();
      while (iit.next()) {
        const link = iit.value;
        if (!this.isSplit(link.fromNode)) {  // if link connects Split with Merge directly, only set fromSpot once
          if (this.angle === 0) {
            if (this.setsPortSpot) link.fromSpot = go.Spot.Right;
            if (this.setsChildPortSpot) link.toSpot = go.Spot.Left;
          } else if (this.angle === 90) {
            if (this.setsPortSpot) link.fromSpot = go.Spot.Bottom;
            if (this.setsChildPortSpot) link.toSpot = go.Spot.Top;
          }
        }
        if (!link.isOrthogonal) continue;
        // have all of the links coming into the Merge node have segments
        // that share a common X (or if angle==90, Y) coordinate
        link.updateRoute();
        if (link.pointsCount >= 6) {
          const pts = link.points.copy();
          const p2 = pts.elt(pts.length - 4);
          const p3 = pts.elt(pts.length - 3);
          if (this.angle === 0 && p2.x === p3.x) {
            const x = mergeNode.position.x - this.layerSpacing / 2;
            pts.setElt(pts.length - 4, new go.Point(x, p2.y));
            pts.setElt(pts.length - 3, new go.Point(x, p3.y));
          } else if (this.angle === 90 && p2.y === p3.y) {
            const y = mergeNode.position.y - this.layerSpacing / 2;
            pts.setElt(pts.length - 4, new go.Point(p2.x, y));
            pts.setElt(pts.length - 3, new go.Point(p3.x, y));
          }
          link.points = pts;
        }
      }
      // handle links coming out of the Merge node, looping back left/up
      const oit = mergeNode.findLinksOutOf();
      while (oit.next()) {
        const link = oit.value;
        // if connects internal with external node, it isn't a loop-back link
        if (link.toNode && link.toNode.containingGroup !== mergeNode.containingGroup) continue;
        if (this.angle === 0) {
          if (this.setsPortSpot) link.fromSpot = go.Spot.TopBottomSides;
          if (this.setsChildPortSpot) link.toSpot = go.Spot.TopBottomSides;
        } else if (this.angle === 90) {
          if (this.setsPortSpot) link.fromSpot = go.Spot.LeftRightSides;
          if (this.setsChildPortSpot) link.toSpot = go.Spot.LeftRightSides;
        }
        link.routing = go.Link.AvoidsNodes;
      }
    }
  }
}