import {Tree, TreeNode, UrlSegment, RouteSegment, rootNode, UrlTree, RouteTree} from './segments';
import {isBlank, isPresent, isString, isStringMap} from '@angular/facade/src/lang';
import {ListWrapper} from '@angular/facade/src/collection';

export function link(segment: RouteSegment, routeTree: RouteTree, urlTree: UrlTree,
                     change: any[]): UrlTree {
  if (change.length === 0) return urlTree;

  let startingNode;
  let normalizedChange;

  if (isString(change[0]) && change[0].startsWith("./")) {
    normalizedChange = ["/", change[0].substring(2)].concat(change.slice(1));
    startingNode = _findStartingNode(_findUrlSegment(segment, routeTree), rootNode(urlTree));

  } else if (isString(change[0]) && change.length === 1 && change[0] == "/") {
    normalizedChange = change;
    startingNode = rootNode(urlTree);

  } else if (isString(change[0]) && !change[0].startsWith("/")) {
    normalizedChange = ["/"].concat(change);
    startingNode = _findStartingNode(_findUrlSegment(segment, routeTree), rootNode(urlTree));

  } else {
    normalizedChange = ["/"].concat(change);
    startingNode = rootNode(urlTree);
  }

  let updated = _update(startingNode, normalizedChange);
  let newRoot = _constructNewTree(rootNode(urlTree), startingNode, updated);

  return new UrlTree(newRoot);
}

function _findUrlSegment(segment: RouteSegment, routeTree: RouteTree): UrlSegment {
  let s = segment;
  let res = null;
  while (isBlank(res)) {
    res = ListWrapper.last(s.urlSegments);
    s = routeTree.parent(s);
  }
  return res;
}

function _findStartingNode(segment: UrlSegment, node: TreeNode<UrlSegment>): TreeNode<UrlSegment> {
  if (node.value === segment) return node;
  for (var c of node.children) {
    let r = _findStartingNode(segment, c);
    if (isPresent(r)) return r;
  }
  return null;
}

function _constructNewTree(node: TreeNode<UrlSegment>, original: TreeNode<UrlSegment>,
                           updated: TreeNode<UrlSegment>): TreeNode<UrlSegment> {
  if (node === original) {
    return new TreeNode<UrlSegment>(node.value, updated.children);
  } else {
    return new TreeNode<UrlSegment>(
        node.value, node.children.map(c => _constructNewTree(c, original, updated)));
  }
}

function _update(node: TreeNode<UrlSegment>, changes: any[]): TreeNode<UrlSegment> {
  let rest = changes.slice(1);
  let outlet = _outlet(changes);
  let segment = _segment(changes);
  if (isString(segment) && segment[0] == "/") segment = segment.substring(1);

  // reach the end of the tree => create new tree nodes.
  if (isBlank(node)) {
    let urlSegment = new UrlSegment(segment, null, outlet);
    let children = rest.length === 0 ? [] : [_update(null, rest)];
    return new TreeNode<UrlSegment>(urlSegment, children);

    // different outlet => preserve the subtree
  } else if (outlet != node.value.outlet) {
    return node;

    // same outlet => modify the subtree
  } else {
    let urlSegment = isStringMap(segment) ? new UrlSegment(null, segment, null) :
                                            new UrlSegment(segment, null, outlet);
    if (rest.length === 0) {
      return new TreeNode<UrlSegment>(urlSegment, []);
    }

    return new TreeNode<UrlSegment>(urlSegment,
                                    _updateMany(ListWrapper.clone(node.children), rest));
  }
}

function _updateMany(nodes: TreeNode<UrlSegment>[], changes: any[]): TreeNode<UrlSegment>[] {
  let outlet = _outlet(changes);
  let nodesInRightOutlet = nodes.filter(c => c.value.outlet == outlet);
  if (nodesInRightOutlet.length > 0) {
    let nodeRightOutlet = nodesInRightOutlet[0];  // there can be only one
    nodes[nodes.indexOf(nodeRightOutlet)] = _update(nodeRightOutlet, changes);
  } else {
    nodes.push(_update(null, changes));
  }

  return nodes;
}

function _segment(changes: any[]): any {
  if (!isString(changes[0])) return changes[0];
  let parts = changes[0].toString().split(":");
  return parts.length > 1 ? parts[1] : changes[0];
}

function _outlet(changes: any[]): string {
  if (!isString(changes[0])) return null;
  let parts = changes[0].toString().split(":");
  return parts.length > 1 ? parts[0] : null;
}