/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

import {EnvironmentInjector, Type, ɵRuntimeError as RuntimeError} from '@angular/core';
import {from, Observable, of} from 'rxjs';
import {catchError, concatMap, defaultIfEmpty, first, last as rxjsLast, map, mergeMap, scan, switchMap, tap} from 'rxjs/operators';

import {AbsoluteRedirect, ApplyRedirects, canLoadFails, noMatch, NoMatch} from './apply_redirects';
import {createUrlTreeFromSnapshot} from './create_url_tree';
import {RuntimeErrorCode} from './errors';
import {Data, LoadedRouterConfig, ResolveData, Route, Routes} from './models';
import {runCanLoadGuards} from './operators/check_guards';
import {RouterConfigLoader} from './router_config_loader';
import {ActivatedRouteSnapshot, getInherited, ParamsInheritanceStrategy, RouterStateSnapshot} from './router_state';
import {PRIMARY_OUTLET} from './shared';
import {UrlSegment, UrlSegmentGroup, UrlSerializer, UrlTree} from './url_tree';
import {last} from './utils/collection';
import {getOutlet, sortByMatchingOutlets} from './utils/config';
import {isImmediateMatch, match, MatchResult, matchWithChecks, noLeftoversInUrl, split} from './utils/config_matching';
import {TreeNode} from './utils/tree';
import {isEmptyError} from './utils/type_guards';

/**
 * Class used to indicate there were no additional route config matches but that all segments of
 * the URL were consumed during matching so the route was URL matched. When this happens, we still
 * try to match child configs in case there are empty path children.
 */
class NoLeftoversInUrl {}

export function recognize(
    injector: EnvironmentInjector, configLoader: RouterConfigLoader,
    rootComponentType: Type<any>|null, config: Routes, urlTree: UrlTree,
    urlSerializer: UrlSerializer,
    paramsInheritanceStrategy: ParamsInheritanceStrategy =
        'emptyOnly'): Observable<{state: RouterStateSnapshot, tree: UrlTree}> {
  return new Recognizer(
             injector, configLoader, rootComponentType, config, urlTree, paramsInheritanceStrategy,
             urlSerializer)
      .recognize();
}

const MAX_ALLOWED_REDIRECTS = 31;

export class Recognizer {
  private applyRedirects = new ApplyRedirects(this.urlSerializer, this.urlTree);
  private absoluteRedirectCount = 0;
  allowRedirects = true;

  constructor(
      private injector: EnvironmentInjector, private configLoader: RouterConfigLoader,
      private rootComponentType: Type<any>|null, private config: Routes, private urlTree: UrlTree,
      private paramsInheritanceStrategy: ParamsInheritanceStrategy,
      private readonly urlSerializer: UrlSerializer) {}

  private noMatchError(e: NoMatch): any {
    return new RuntimeError(
        RuntimeErrorCode.NO_MATCH,
        (typeof ngDevMode === 'undefined' || ngDevMode) &&
            `Cannot match any routes. URL Segment: '${e.segmentGroup}'`);
  }

  recognize(): Observable<{state: RouterStateSnapshot, tree: UrlTree}> {
    const rootSegmentGroup = split(this.urlTree.root, [], [], this.config).segmentGroup;

    return this.match(rootSegmentGroup).pipe(map(children => {
      // Use Object.freeze to prevent readers of the Router state from modifying it outside
      // of a navigation, resulting in the router being out of sync with the browser.
      const root = new ActivatedRouteSnapshot(
          [], Object.freeze({}), Object.freeze({...this.urlTree.queryParams}),
          this.urlTree.fragment, {}, PRIMARY_OUTLET, this.rootComponentType, null, {});

      const rootNode = new TreeNode(root, children);
      const routeState = new RouterStateSnapshot('', rootNode);
      const tree =
          createUrlTreeFromSnapshot(root, [], this.urlTree.queryParams, this.urlTree.fragment);
      // https://github.com/angular/angular/issues/47307
      // Creating the tree stringifies the query params
      // We don't want to do this here so reassign them to the original.
      tree.queryParams = this.urlTree.queryParams;
      routeState.url = this.urlSerializer.serialize(tree);
      this.inheritParamsAndData(routeState._root, null);
      return {state: routeState, tree};
    }));
  }


  private match(rootSegmentGroup: UrlSegmentGroup): Observable<TreeNode<ActivatedRouteSnapshot>[]> {
    const expanded$ =
        this.processSegmentGroup(this.injector, this.config, rootSegmentGroup, PRIMARY_OUTLET);
    return expanded$.pipe(catchError((e: any) => {
      if (e instanceof AbsoluteRedirect) {
        this.urlTree = e.urlTree;
        return this.match(e.urlTree.root);
      }
      if (e instanceof NoMatch) {
        throw this.noMatchError(e);
      }

      throw e;
    }));
  }

  inheritParamsAndData(
      routeNode: TreeNode<ActivatedRouteSnapshot>, parent: ActivatedRouteSnapshot|null): void {
    const route = routeNode.value;
    const i = getInherited(route, parent, this.paramsInheritanceStrategy);

    route.params = Object.freeze(i.params);
    route.data = Object.freeze(i.data);

    routeNode.children.forEach(n => this.inheritParamsAndData(n, route));
  }

  processSegmentGroup(
      injector: EnvironmentInjector, config: Route[], segmentGroup: UrlSegmentGroup,
      outlet: string): Observable<TreeNode<ActivatedRouteSnapshot>[]> {
    if (segmentGroup.segments.length === 0 && segmentGroup.hasChildren()) {
      return this.processChildren(injector, config, segmentGroup);
    }

    return this.processSegment(injector, config, segmentGroup, segmentGroup.segments, outlet, true)
        .pipe(map(child => child instanceof TreeNode ? [child] : []));
  }

  /**
   * Matches every child outlet in the `segmentGroup` to a `Route` in the config. Returns `null` if
   * we cannot find a match for _any_ of the children.
   *
   * @param config - The `Routes` to match against
   * @param segmentGroup - The `UrlSegmentGroup` whose children need to be matched against the
   *     config.
   */
  processChildren(injector: EnvironmentInjector, config: Route[], segmentGroup: UrlSegmentGroup):
      Observable<TreeNode<ActivatedRouteSnapshot>[]> {
    // Expand outlets one at a time, starting with the primary outlet. We need to do it this way
    // because an absolute redirect from the primary outlet takes precedence.
    const childOutlets: string[] = [];
    for (const child of Object.keys(segmentGroup.children)) {
      if (child === 'primary') {
        childOutlets.unshift(child);
      } else {
        childOutlets.push(child);
      }
    }
    return from(childOutlets)
        .pipe(
            concatMap(childOutlet => {
              const child = segmentGroup.children[childOutlet];
              // Sort the config so that routes with outlets that match the one being activated
              // appear first, followed by routes for other outlets, which might match if they have
              // an empty path.
              const sortedConfig = sortByMatchingOutlets(config, childOutlet);
              return this.processSegmentGroup(injector, sortedConfig, child, childOutlet);
            }),
            scan((children, outletChildren) => {
              children.push(...outletChildren);
              return children;
            }),
            defaultIfEmpty(null as TreeNode<ActivatedRouteSnapshot>[] | null),
            rxjsLast(),
            mergeMap(children => {
              if (children === null) return noMatch(segmentGroup);
              // Because we may have matched two outlets to the same empty path segment, we can have
              // multiple activated results for the same outlet. We should merge the children of
              // these results so the final return value is only one `TreeNode` per outlet.
              const mergedChildren = mergeEmptyPathMatches(children);
              if (typeof ngDevMode === 'undefined' || ngDevMode) {
                // This should really never happen - we are only taking the first match for each
                // outlet and merge the empty path matches.
                checkOutletNameUniqueness(mergedChildren);
              }
              sortActivatedRouteSnapshots(mergedChildren);
              return of(mergedChildren);
            }),
        );
  }

  processSegment(
      injector: EnvironmentInjector, routes: Route[], segmentGroup: UrlSegmentGroup,
      segments: UrlSegment[], outlet: string,
      allowRedirects: boolean): Observable<TreeNode<ActivatedRouteSnapshot>|NoLeftoversInUrl> {
    return from(routes).pipe(
        concatMap(r => {
          return this
              .processSegmentAgainstRoute(
                  r._injector ?? injector, routes, r, segmentGroup, segments, outlet,
                  allowRedirects)
              .pipe(catchError((e: any) => {
                if (e instanceof NoMatch) {
                  return of(null);
                }
                throw e;
              }));
        }),
        first((x): x is TreeNode<ActivatedRouteSnapshot>|NoLeftoversInUrl => !!x), catchError(e => {
          if (isEmptyError(e)) {
            if (noLeftoversInUrl(segmentGroup, segments, outlet)) {
              return of(new NoLeftoversInUrl());
            }
            return noMatch(segmentGroup);
          }
          throw e;
        }));
  }

  processSegmentAgainstRoute(
      injector: EnvironmentInjector, routes: Route[], route: Route, rawSegment: UrlSegmentGroup,
      segments: UrlSegment[], outlet: string,
      allowRedirects: boolean): Observable<TreeNode<ActivatedRouteSnapshot>|NoLeftoversInUrl> {
    if (!isImmediateMatch(route, rawSegment, segments, outlet)) return noMatch(rawSegment);

    if (route.redirectTo === undefined) {
      return this.matchSegmentAgainstRoute(injector, rawSegment, route, segments, outlet);
    }

    if (this.allowRedirects && allowRedirects) {
      return this.expandSegmentAgainstRouteUsingRedirect(
          injector, rawSegment, routes, route, segments, outlet);
    }

    return noMatch(rawSegment);
  }

  private expandSegmentAgainstRouteUsingRedirect(
      injector: EnvironmentInjector, segmentGroup: UrlSegmentGroup, routes: Route[], route: Route,
      segments: UrlSegment[],
      outlet: string): Observable<TreeNode<ActivatedRouteSnapshot>|NoLeftoversInUrl> {
    const {
      matched,
      consumedSegments,
      positionalParamSegments,
      remainingSegments,
    } = route.path === '**' ? createWildcardMatchResult(segments) :
                              match(segmentGroup, route, segments);
    if (!matched) return noMatch(segmentGroup);

    // TODO(atscott): Move all of this under an if(ngDevMode) as a breaking change and allow stack
    // size exceeded in production
    if (route.redirectTo!.startsWith('/')) {
      this.absoluteRedirectCount++;
      if (this.absoluteRedirectCount > MAX_ALLOWED_REDIRECTS) {
        if (ngDevMode) {
          throw new RuntimeError(
              RuntimeErrorCode.INFINITE_REDIRECT,
              `Detected possible infinite redirect when redirecting from '${this.urlTree}' to '${
                  route.redirectTo}'.\n` +
                  `This is currently a dev mode only error but will become a` +
                  ` call stack size exceeded error in production in a future major version.`);
        }
        this.allowRedirects = false;
      }
    }
    const newTree = this.applyRedirects.applyRedirectCommands(
        consumedSegments, route.redirectTo!, positionalParamSegments);

    return this.applyRedirects.lineralizeSegments(route, newTree)
        .pipe(mergeMap((newSegments: UrlSegment[]) => {
          return this.processSegment(
              injector, routes, segmentGroup, newSegments.concat(remainingSegments), outlet, false);
        }));
  }

  matchSegmentAgainstRoute(
      injector: EnvironmentInjector, rawSegment: UrlSegmentGroup, route: Route,
      segments: UrlSegment[], outlet: string): Observable<TreeNode<ActivatedRouteSnapshot>> {
    let matchResult: Observable<MatchResult>;

    if (route.path === '**') {
      matchResult = of(createWildcardMatchResult(segments));
      // Prior versions of the route matching algorithm would stop matching at the wildcard route.
      // We should investigate a better strategy for any existing children. Otherwise, these
      // child segments are silently dropped from the navigation.
      // https://github.com/angular/angular/issues/40089
      rawSegment.children = {};
    } else {
      matchResult = matchWithChecks(rawSegment, route, segments, injector, this.urlSerializer);
    }

    return matchResult.pipe(switchMap((result) => {
      if (!result.matched) {
        return noMatch(rawSegment);
      }

      // If the route has an injector created from providers, we should start using that.
      injector = route._injector ?? injector;
      return this.getChildConfig(injector, route, segments)
          .pipe(switchMap(({routes: childConfig}) => {
            const childInjector = route._loadedInjector ?? injector;

            const {consumedSegments, remainingSegments, parameters} = result;
            const snapshot = new ActivatedRouteSnapshot(
                consumedSegments, parameters, Object.freeze({...this.urlTree.queryParams}),
                this.urlTree.fragment, getData(route), getOutlet(route),
                route.component ?? route._loadedComponent ?? null, route, getResolve(route));

            const {segmentGroup, slicedSegments} =
                split(rawSegment, consumedSegments, remainingSegments, childConfig);

            if (slicedSegments.length === 0 && segmentGroup.hasChildren()) {
              return this.processChildren(childInjector, childConfig, segmentGroup)
                  .pipe(map(children => {
                    if (children === null) {
                      return null;
                    }
                    return new TreeNode(snapshot, children);
                  }));
            }

            if (childConfig.length === 0 && slicedSegments.length === 0) {
              return of(new TreeNode(snapshot, []));
            }

            const matchedOnOutlet = getOutlet(route) === outlet;
            // If we matched a config due to empty path match on a different outlet, we need to
            // continue passing the current outlet for the segment rather than switch to PRIMARY.
            // Note that we switch to primary when we have a match because outlet configs look like
            // this: {path: 'a', outlet: 'a', children: [
            //  {path: 'b', component: B},
            //  {path: 'c', component: C},
            // ]}
            // Notice that the children of the named outlet are configured with the primary outlet
            return this
                .processSegment(
                    childInjector, childConfig, segmentGroup, slicedSegments,
                    matchedOnOutlet ? PRIMARY_OUTLET : outlet, true)
                .pipe(map(child => {
                  return new TreeNode(snapshot, child instanceof TreeNode ? [child] : []);
                }));
          }));
    }));
  }
  private getChildConfig(injector: EnvironmentInjector, route: Route, segments: UrlSegment[]):
      Observable<LoadedRouterConfig> {
    if (route.children) {
      // The children belong to the same module
      return of({routes: route.children, injector});
    }

    if (route.loadChildren) {
      // lazy children belong to the loaded module
      if (route._loadedRoutes !== undefined) {
        return of({routes: route._loadedRoutes, injector: route._loadedInjector});
      }

      return runCanLoadGuards(injector, route, segments, this.urlSerializer)
          .pipe(mergeMap((shouldLoadResult: boolean) => {
            if (shouldLoadResult) {
              return this.configLoader.loadChildren(injector, route)
                  .pipe(tap((cfg: LoadedRouterConfig) => {
                    route._loadedRoutes = cfg.routes;
                    route._loadedInjector = cfg.injector;
                  }));
            }
            return canLoadFails(route);
          }));
    }

    return of({routes: [], injector});
  }
}

function sortActivatedRouteSnapshots(nodes: TreeNode<ActivatedRouteSnapshot>[]): void {
  nodes.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);
  });
}

function hasEmptyPathConfig(node: TreeNode<ActivatedRouteSnapshot>) {
  const config = node.value.routeConfig;
  return config && config.path === '';
}

/**
 * Finds `TreeNode`s with matching empty path route configs and merges them into `TreeNode` with
 * the children from each duplicate. This is necessary because different outlets can match a
 * single empty path route config and the results need to then be merged.
 */
function mergeEmptyPathMatches(nodes: Array<TreeNode<ActivatedRouteSnapshot>>):
    Array<TreeNode<ActivatedRouteSnapshot>> {
  const result: Array<TreeNode<ActivatedRouteSnapshot>> = [];
  // The set of nodes which contain children that were merged from two duplicate empty path nodes.
  const mergedNodes: Set<TreeNode<ActivatedRouteSnapshot>> = new Set();

  for (const node of nodes) {
    if (!hasEmptyPathConfig(node)) {
      result.push(node);
      continue;
    }

    const duplicateEmptyPathNode =
        result.find(resultNode => node.value.routeConfig === resultNode.value.routeConfig);
    if (duplicateEmptyPathNode !== undefined) {
      duplicateEmptyPathNode.children.push(...node.children);
      mergedNodes.add(duplicateEmptyPathNode);
    } else {
      result.push(node);
    }
  }
  // For each node which has children from multiple sources, we need to recompute a new `TreeNode`
  // by also merging those children. This is necessary when there are multiple empty path configs
  // in a row. Put another way: whenever we combine children of two nodes, we need to also check
  // if any of those children can be combined into a single node as well.
  for (const mergedNode of mergedNodes) {
    const mergedChildren = mergeEmptyPathMatches(mergedNode.children);
    result.push(new TreeNode(mergedNode.value, mergedChildren));
  }
  return result.filter(n => !mergedNodes.has(n));
}

function checkOutletNameUniqueness(nodes: TreeNode<ActivatedRouteSnapshot>[]): void {
  const names: {[k: string]: ActivatedRouteSnapshot} = {};
  nodes.forEach(n => {
    const routeWithSameOutletName = names[n.value.outlet];
    if (routeWithSameOutletName) {
      const p = routeWithSameOutletName.url.map(s => s.toString()).join('/');
      const c = n.value.url.map(s => s.toString()).join('/');
      throw new RuntimeError(
          RuntimeErrorCode.TWO_SEGMENTS_WITH_SAME_OUTLET,
          (typeof ngDevMode === 'undefined' || ngDevMode) &&
              `Two segments cannot have the same outlet name: '${p}' and '${c}'.`);
    }
    names[n.value.outlet] = n.value;
  });
}

function getData(route: Route): Data {
  return route.data || {};
}

function getResolve(route: Route): ResolveData {
  return route.resolve || {};
}

function createWildcardMatchResult(segments: UrlSegment[]): MatchResult {
  return {
    matched: true,
    parameters: segments.length > 0 ? last(segments)!.parameters : {},
    consumedSegments: segments,
    remainingSegments: [],
    positionalParamSegments: {},
  };
}