import { UrlTree, UrlSegment } from './url_tree';
import { flatten, first, merge } from './utils/collection';
import { TreeNode } from './utils/tree';
import { RouterStateSnapshot, ActivatedRouteSnapshot } from './router_state';
import { Params, PRIMARY_OUTLET } from './shared';
import { RouterConfig, Route } from './config';
import { Type } from '@angular/core';
import { Observable } from 'rxjs/Observable';

class CannotRecognize {}

export function recognize(rootComponentType: Type, config: RouterConfig, url: UrlTree): Observable<RouterStateSnapshot> {
  try {
    const match = new MatchResult(rootComponentType, config, [url.root], {}, url._root.children, [], PRIMARY_OUTLET, null, url.root);
    const roots = constructActivatedRoute(match);
    const res = new RouterStateSnapshot(roots[0], url.queryParameters, url.fragment);
    return new Observable<RouterStateSnapshot>(obs => {
      obs.next(res);
      obs.complete();
    });
  } catch(e) {
    if (e instanceof CannotRecognize) {
      return new Observable<RouterStateSnapshot>(obs => obs.error(new Error("Cannot match any routes")));
    } else {
      return new Observable<RouterStateSnapshot>(obs => obs.error(e));
    }
  }
}

function constructActivatedRoute(match: MatchResult): TreeNode<ActivatedRouteSnapshot>[] {
  const activatedRoute = createActivatedRouteSnapshot(match);
  const children = match.leftOverUrl.length > 0 ?
    recognizeMany(match.children, match.leftOverUrl) : recognizeLeftOvers(match.children, match.lastUrlSegment);
  checkOutletNameUniqueness(children);
  children.sort((a, b) => {
    if (a.value.outlet === PRIMARY_OUTLET) return -1;
    if (b.value.outlet === PRIMARY_OUTLET) return 1;
    return a.value.outlet.localeCompare(b.value.outlet)
  });
  return [new TreeNode<ActivatedRouteSnapshot>(activatedRoute, children)];
}

function recognizeLeftOvers(config: Route[], lastUrlSegment: UrlSegment): TreeNode<ActivatedRouteSnapshot>[] {
  if (!config) return [];
  const mIndex = matchIndex(config, [], lastUrlSegment);
  return mIndex ? constructActivatedRoute(mIndex) : [];
}

function recognizeMany(config: Route[], urls: TreeNode<UrlSegment>[]): TreeNode<ActivatedRouteSnapshot>[] {
  return flatten(urls.map(url => recognizeOne(config, url)));
}

function createActivatedRouteSnapshot(match: MatchResult): ActivatedRouteSnapshot {
  return new ActivatedRouteSnapshot(match.consumedUrlSegments, match.parameters, match.outlet, match.component, match.route, match.lastUrlSegment);
}

function recognizeOne(config: Route[], url: TreeNode<UrlSegment>): TreeNode<ActivatedRouteSnapshot>[] {
  const matches = match(config, url);
  for(let match of matches) {
    try {
      const primary = constructActivatedRoute(match);
      const secondary = recognizeMany(config, match.secondary);
      const res = primary.concat(secondary);
      checkOutletNameUniqueness(res);
      return res;
    } catch (e) {
      if (! (e instanceof CannotRecognize)) {
        throw e;
      }
    }
  }
  throw new CannotRecognize();
}

function checkOutletNameUniqueness(nodes: TreeNode<ActivatedRouteSnapshot>[]): TreeNode<ActivatedRouteSnapshot>[] {
  let names = {};
  nodes.forEach(n => {
    let routeWithSameOutletName = names[n.value.outlet];
    if (routeWithSameOutletName) {
      const p = routeWithSameOutletName.urlSegments.map(s => s.toString()).join("/");
      const c = n.value.urlSegments.map(s => s.toString()).join("/");
      throw new Error(`Two segments cannot have the same outlet name: '${p}' and '${c}'.`);
    }
    names[n.value.outlet] = n.value;
  });
  return nodes;
}

function match(config: Route[], url: TreeNode<UrlSegment>): MatchResult[] {
  const res = [];
  for (let r of config) {
    if (r.index) {
      res.push(createIndexMatch(r, [url], url.value));
    } else {
      const m = matchWithParts(r, url);
      if (m) res.push(m);
    }
  }
  return res;
}

function createIndexMatch(r: Route, leftOverUrls:TreeNode<UrlSegment>[], lastUrlSegment:UrlSegment): MatchResult {
  const outlet = r.outlet ? r.outlet : PRIMARY_OUTLET;
  const children = r.children ? r.children : [];
  return new MatchResult(r.component, children, [], lastUrlSegment.parameters, leftOverUrls, [], outlet, r, lastUrlSegment);
}

function matchIndex(config: Route[], leftOverUrls: TreeNode<UrlSegment>[], lastUrlSegment: UrlSegment): MatchResult | null {
  for (let r of config) {
    if (r.index) {
      return createIndexMatch(r, leftOverUrls, lastUrlSegment);
    }
  }
  return null;
}

function matchWithParts(route: Route, url: TreeNode<UrlSegment>): MatchResult | null {
  if (!route.path) return null;
  if ((route.outlet ? route.outlet : PRIMARY_OUTLET) !== url.value.outlet) return null;

  const path = route.path.startsWith("/") ? route.path.substring(1) : route.path;
  if (path === "**") {
    const consumedUrl = [];
    let u:TreeNode<UrlSegment>|null = url;
    while (u) {
      consumedUrl.push(u.value);
      u = first(u.children);
    }
    const last = consumedUrl[consumedUrl.length - 1];
    return new MatchResult(route.component, [], consumedUrl, last.parameters, [], [], PRIMARY_OUTLET, route, last);
  }

  const parts = path.split("/");
  const positionalParams = {};
  const consumedUrlSegments = [];

  let lastParent: TreeNode<UrlSegment>|null = null;
  let lastSegment: TreeNode<UrlSegment>|null = null;

  let current: TreeNode<UrlSegment>|null = url;
  for (let i = 0; i < parts.length; ++i) {
    if (!current) return null;

    const p = parts[i];
    const isLastSegment = i === parts.length - 1;
    const isLastParent = i === parts.length - 2;
    const isPosParam = p.startsWith(":");

    if (!isPosParam && p != current.value.path) return null;
    if (isLastSegment) {
      lastSegment = current;
    }
    if (isLastParent) {
      lastParent = current;
    }

    if (isPosParam) {
      positionalParams[p.substring(1)] = current.value.path;
    }

    consumedUrlSegments.push(current.value);

    current = first(current.children);
  }

  if (!lastSegment) throw "Cannot be reached";

  const p = lastSegment.value.parameters;
  const parameters = <{[key: string]: string}>merge(p, positionalParams);
  const secondarySubtrees = lastParent ? lastParent.children.slice(1) : [];
  const children = route.children ? route.children : [];
  const outlet = route.outlet ? route.outlet : PRIMARY_OUTLET;

  return new MatchResult(route.component, children, consumedUrlSegments, parameters, lastSegment.children,
    secondarySubtrees, outlet, route, lastSegment.value);
}

class MatchResult {
  constructor(public component: Type | string,
              public children: Route[],
              public consumedUrlSegments: UrlSegment[],
              public parameters: {[key: string]: string},
              public leftOverUrl: TreeNode<UrlSegment>[],
              public secondary: TreeNode<UrlSegment>[],
              public outlet: string,
              public route: Route | null,
              public lastUrlSegment: UrlSegment
  ) {}
}