ui/code-owners-service.js - plugins/code-owners - Git at Google

 /**
  * @license
  * Copyright (C) 2020 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 /**
  * All statuses returned for owner status.
  *
  * @enum
  */
 export const OwnerStatus = {
   INSUFFICIENT_REVIEWERS: 'INSUFFICIENT_REVIEWERS',
   PENDING: 'PENDING',
   APPROVED: 'APPROVED',
 };

 /**
  * @enum
  */
 const FetchStatus = {
   NOT_STARTED: 0,
   FETCHING: 1,
   FINISHED: 2,
   ABORT: 3,
 };

 /**
  * Specifies status for a change. The same as ChangeStatus enum in gerrit
  *
  * @enum
  */
 const ChangeStatus = {
   ABANDONED: 'ABANDONED',
   MERGED: 'MERGED',
   NEW: 'NEW',
 };

 /**
  * @enum
  */
 const UserRole = {
   ANONYMOUS: 'ANONYMOUS',
   AUTHOR: 'AUTHOR',
   CHANGE_OWNER: 'CHANGE_OWNER',
   REVIEWER: 'REVIEWER',
   CC: 'CC',
   REMOVED_REVIEWER: 'REMOVED_REVIEWER',
   OTHER: 'OTHER',
 };

 /**
  * Responsible for communicating with the rest-api
  *
  * @see resources/Documentation/rest-api.md
  */
 class CodeOwnerApi {
   constructor(restApi) {
     this.restApi = restApi;
   }

   /**
    * Returns a promise fetching the owner statuses for all files within the change.
    *
    * @doc https://gerrit.googlesource.com/plugins/code-owners/+/refs/heads/master/resources/Documentation/rest-api.md#change-endpoints
    * @param {string} changeId
    */
   listOwnerStatus(changeId) {
     return this.restApi.get(`/changes/${changeId}/code_owners.status`);
   }

   /**
    * Returns a promise fetching the owners for a given path.
    *
    * @doc https://gerrit.googlesource.com/plugins/code-owners/+/refs/heads/master/resources/Documentation/rest-api.md#list-code-owners-for-path-in-branch
    * @param {string} changeId
    * @param {string} path
    */
   listOwnersForPath(changeId, path) {
     return this.restApi.get(
         `/changes/${changeId}/revisions/current/code_owners` +
         `/${encodeURIComponent(path)}?limit=5&o=DETAILS`
     );
   }

   /**
    * Returns a promise fetching the owners config for a given path.
    *
    * @doc https://gerrit.googlesource.com/plugins/code-owners/+/refs/heads/master/resources/Documentation/rest-api.md#branch-endpoints
    * @param {string} project
    * @param {string} branch
    * @param {string} path
    */
   getConfigForPath(project, branch, path) {
     return this.restApi.get(
         `/projects/${encodeURIComponent(project)}/` +
         `branches/${encodeURIComponent(branch)}/` +
         `code_owners.config/${encodeURIComponent(path)}`
     );
   }

   /**
    * Returns a promise fetching the owners config for a given branch.
    *
    * @doc https://gerrit.googlesource.com/plugins/code-owners/+/refs/heads/master/resources/Documentation/rest-api.md#branch-endpoints
    * @param {string} project
    * @param {string} branch
    */
   async getBranchConfig(project, branch) {
     const config = await this.restApi.get(
         `/projects/${encodeURIComponent(project)}/` +
         `branches/${encodeURIComponent(branch)}/` +
         `code_owners.branch_config`
     );
     if (config.override_approval && !(config.override_approval instanceof Array)) {
       // In the upcoming backend changes, the override_approval will be changed
       // to array with (possible) multiple items.
       // While this transition is in progress, the frontend supports both API -
       // the old one and the new one.
       return {...config, override_approval: [config.override_approval]};
     }
     return config;
   }
 }

 /**
  * Wrapper around codeOwnerApi, sends each requests only once and then cache
  * the response. A new CodeOwnersCacheApi instance is created every time when a
  * new change object is assigned.
  * Gerrit never updates existing change object, but instead always assigns a new
  * change object. Particularly, a new change object is assigned when a change
  * is updated and user clicks reload toasts to see the updated change.
  * As a result, the lifetime of a cache is the same as a lifetime of an assigned
  * change object.
  * Periodical cache invalidation can lead to inconsistency in UI, i.e.
  * user can see the old reviewers list (reflects a state when a change was
  * loaded) and code-owners status for the current reviewer list. To avoid
  * this inconsistency, the cache doesn't invalidate.
  */
 export class CodeOwnersCacheApi {
   constructor(codeOwnerApi, change) {
     this.codeOwnerApi = codeOwnerApi;
     this.change = change;
     this.promises = {};
   }

   _fetchOnce(cacheKey, asyncFn) {
     if (!this.promises[cacheKey]) {
       this.promises[cacheKey] = asyncFn();
     }
     return this.promises[cacheKey];
   }

   getAccount() {
     return this._fetchOnce('getAccount', () => this._getAccount());
   }

   async _getAccount() {
     const loggedIn = await this.codeOwnerApi.restApi.getLoggedIn();
     if (!loggedIn) return undefined;
     return await this.codeOwnerApi.restApi.getAccount();
   }

   listOwnerStatus() {
     return this._fetchOnce('listOwnerStatus',
         () => this.codeOwnerApi.listOwnerStatus(this.change._number));
   }

   getBranchConfig() {
     return this._fetchOnce('getBranchConfig',
         () => this.codeOwnerApi.getBranchConfig(this.change.project,
             this.change.branch));
   }

   listOwnersForPath(path) {
     return this._fetchOnce(`listOwnersForPath:${path}`,
         () => this.codeOwnerApi.listOwnersForPath(this.change.id, path));
   }
 }

 export class OwnersFetcher {
   constructor(restApi, change, options) {
     // fetched files and fetching status
     this._fetchedOwners = new Map();
     this._fetchStatus = FetchStatus.NOT_STARTED;
     this._totalFetchCount = 0;
     this.change = change;
     this.options = options;
     this.codeOwnerApi = new CodeOwnerApi(restApi);
   }

   getStatus() {
     return this._fetchStatus;
   }

   getProgressString() {
     return this._totalFetchCount === 0 ?
       `Loading suggested owners ...` :
       `${this._fetchedOwners.size} out of ${this._totalFetchCount} files have returned suggested owners.`;
   }

   getFiles() {
     const result = [];
     for (const [path, info] of this._fetchedOwners.entries()) {
       result.push({path, info});
     }
     return result;
   }

   async fetchSuggestedOwners(codeOwnerStatusMap) {
     // reset existing temporary storage
     this._fetchedOwners = new Map();
     this._fetchStatus = FetchStatus.FETCHING;
     this._totalFetchCount = 0;

     // only fetch those not approved yet
     const filesGroupByStatus = [...codeOwnerStatusMap.keys()].reduce(
         (list, file) => {
           const status = codeOwnerStatusMap
               .get(file).status;
           if (status === OwnerStatus.INSUFFICIENT_REVIEWERS) {
             list.missing.push(file);
           } else if (status === OwnerStatus.PENDING) {
             list.pending.push(file);
           }
           return list;
         }
         , {pending: [], missing: []});
     // always fetch INSUFFICIENT_REVIEWERS first and then pending
     const filesToFetch = filesGroupByStatus.missing
         .concat(filesGroupByStatus.pending);
     this._totalFetchCount = filesToFetch.length;
     await this._batchFetchCodeOwners(filesToFetch);
     this._fetchStatus = FetchStatus.FINISHED;
   }

   /**
    * Recursively fetches code owners for all files until finished.
    *
    * @param {!Array<string>} files
    */
   async _batchFetchCodeOwners(files) {
     if (this._fetchStatus === FetchStatus.ABORT) {
       return this._fetchedOwners;
     }

     const batchRequests = [];
     const maxConcurrentRequests = this.options.maxConcurrentRequests;
     for (let i = 0; i < maxConcurrentRequests; i++) {
       const filePath = files[i];
       if (filePath) {
         this._fetchedOwners.set(filePath, {});
         batchRequests.push(this._fetchOwnersForPath(this.change.id, filePath));
       }
     }
     const resPromise = Promise.all(batchRequests);
     await resPromise;
     if (files.length > maxConcurrentRequests) {
       return await this._batchFetchCodeOwners(
           files.slice(maxConcurrentRequests));
     }
     return this._fetchedOwners;
   }

   async _fetchOwnersForPath(changeId, filePath) {
     try {
       const owners = await this.codeOwnerApi.listOwnersForPath(changeId,
           filePath);
       // In the upcoming backend changes, the api will return an object instead
       // of array. While this transition is in progress, the frontend supports
       // both API - the old one and the new one.
       this._fetchedOwners.get(filePath).owners = new Set(
           owners instanceof Array ? owners : owners.code_owners);
     } catch (e) {
       this._fetchedOwners.get(filePath).error = e;
     }
   }

   abort() {
     this._fetchStatus = FetchStatus.ABORT;
     this._fetchedOwners = new Map();
     this._totalFetchCount = 0;
   }
 }

 /**
  * Service for the data layer used in the plugin UI.
  */
 export class CodeOwnerService {
   constructor(restApi, change, options = {}) {
     this.restApi = restApi;
     this.change = change;
     const codeOwnerApi = new CodeOwnerApi(restApi);
     this.codeOwnerCacheApi = new CodeOwnersCacheApi(codeOwnerApi, change);

     const fetcherOptions = {
       maxConcurrentRequests: options.maxConcurrentRequests || 10,
     };
     this.ownersFetcher = new OwnersFetcher(restApi, change, fetcherOptions);
   }

   /**
    * Prefetch data
    */
   async prefetch() {
     try {
       await Promise.all([
         this.codeOwnerCacheApi.getAccount(),
         this.getStatus(),
       ]);
     } catch {
       // Ignore any errors during prefetch.
       // The same call from a different place throws the same exception
       // again. The CodeOwnerService is not responsible for error processing.
     }
   }

   /**
    * Returns the role of the current user. The returned value reflects the
    * role of the user at the time when the change is loaded.
    * For example, if a user removes themselves as a reviewer, the returned
    * role 'REVIEWER' remains unchanged until the change view is reloaded.
    */
   async getLoggedInUserInitialRole() {
     const account = await this.codeOwnerCacheApi.getAccount();
     if (!account) {
       return UserRole.ANONYMOUS;
     }
     const change = this.change;
     if (
       change.revisions &&
       change.current_revision &&
       change.revisions[change.current_revision]
     ) {
       const commit = change.revisions[change.current_revision].commit;
       if (
         commit &&
         commit.author &&
         account.email &&
         commit.author.email === account.email
       ) {
         return UserRole.AUTHOR;
       }
     }
     if (change.owner._account_id === account._account_id) {
       return UserRole.CHANGE_OWNER;
     }
     if (change.reviewers) {
       if (this._accountInReviewers(change.reviewers.REVIEWER, account)) {
         return UserRole.REVIEWER;
       } else if (this._accountInReviewers(change.reviewers.CC, account)) {
         return UserRole.CC;
       } else if (this._accountInReviewers(change.reviewers.REMOVED, account)) {
         return UserRole.REMOVED_REVIEWER;
       }
     }
     return UserRole.OTHER;
   }

   _accountInReviewers(reviewers, account) {
     if (!reviewers) {
       return false;
     }
     return reviewers.some(reviewer =>
       reviewer._account_id === account._account_id);
   }

   async getStatus() {
     const status = await this._getStatus();
     if (status.enabled && !this.isOnLatestPatchset(status.patchsetNumber)) {
       // status is outdated, abort and re-init
       this.abort();
       this.prefetch();
       return await this.codeOwnerCacheApi.getStatus();
     }
     return status;
   }

   async _getStatus() {
     const enabled = await this.isCodeOwnerEnabled();
     if (!enabled) {
       return {
         patchsetNumber: 0,
         enabled: false,
         codeOwnerStatusMap: new Map(),
         rawStatuses: [],
       };
     }

     const onwerStatus = await this.codeOwnerCacheApi.listOwnerStatus();

     return {
       enabled: true,
       patchsetNumber: onwerStatus.patch_set_number,
       codeOwnerStatusMap: this._formatStatuses(
           onwerStatus.file_code_owner_statuses
       ),
       rawStatuses: onwerStatus.file_code_owner_statuses,
     };
   }

   async areAllFilesApproved() {
     const {rawStatuses} = await this.getStatus();
     return !rawStatuses.some(status => {
       const oldPathStatus = status.old_path_status;
       const newPathStatus = status.new_path_status;
       // For deleted files, no new_path_status exists
       return (newPathStatus && newPathStatus.status !== OwnerStatus.APPROVED)
         || (oldPathStatus && oldPathStatus.status !== OwnerStatus.APPROVED);
     });
   }

   /**
    * Gets owner suggestions.
    *
    * @returns {{
    *  finished?: boolean,
    *  progress?: string,
    *  suggestions: Array<{
    *    groupName: {
    *      name: string,
    *      prefix: string
    *    },
    *    error?: Error,
    *    owners?: Array,
    *    files: Array,
    *  }>
    * }}
    */
   async getSuggestedOwners() {
     const {codeOwnerStatusMap} = await this.getStatus();

     // In case its aborted due to outdated patches
     // should kick start the fetching again
     // Note: we currently are not reusing the instance when switching changes,
     // so if its `abort` due to different changes, the whole instance will be
     // outdated and not used.
     if (this.ownersFetcher.getStatus() === FetchStatus.NOT_STARTED
       || this.ownersFetcher.getStatus() === FetchStatus.ABORT) {
       await this.ownersFetcher.fetchSuggestedOwners(codeOwnerStatusMap);
     }

     return {
       finished: this.ownersFetcher.getStatus() === FetchStatus.FINISHED,
       status: this.ownersFetcher.getStatus(),
       progress: this.ownersFetcher.getProgressString(),
       suggestions: this._groupFilesByOwners(codeOwnerStatusMap,
           this.ownersFetcher.getFiles()),
     };
   }

   async getSuggestedOwnersProgress() {
     const {codeOwnerStatusMap} = await this.getStatus();
     return {
       finished: this.ownersFetcher.getStatus() === FetchStatus.FINISHED,
       status: this.ownersFetcher.getStatus(),
       progress: this.ownersFetcher.getProgressString(),
       suggestions: this._groupFilesByOwners(codeOwnerStatusMap,
           this.ownersFetcher.getFiles()),
     };
   }

   _formatStatuses(statuses) {
     // convert the array of statuses to map between file path -> status
     return statuses.reduce((prev, cur) => {
       const newPathStatus = cur.new_path_status;
       const oldPathStatus = cur.old_path_status;
       if (oldPathStatus) {
         prev.set(oldPathStatus.path, {
           changeType: cur.change_type,
           status: oldPathStatus.status,
           newPath: newPathStatus ? newPathStatus.path : null,
         });
       }
       if (newPathStatus) {
         prev.set(newPathStatus.path, {
           changeType: cur.change_type,
           status: newPathStatus.status,
           oldPath: oldPathStatus ? oldPathStatus.path : null,
         });
       }
       return prev;
     }, new Map());
   }

   _computeFileStatus(fileStatusMap, path) {
     // empty for modified files and old-name files
     // Show `Renamed` for renamed file
     const status = fileStatusMap.get(path);
     if (status.oldPath) {
       return 'Renamed';
     }
     return;
   }

   _groupFilesByOwners(codeOwnerStatusMap, files) {
     // Note: for renamed or moved files, they will have two entries in the map
     // we will treat them as two entries when group as well
     const ownersFilesMap = new Map();
     const failedToFetchFiles = new Set();
     for (const file of files) {
       const fileInfo = {
         path: file.path,
         status: this._computeFileStatus(codeOwnerStatusMap, file.path),
       };
       // for files failed to fetch, add them to the special group
       if (file.info.error) {
         failedToFetchFiles.add(fileInfo);
         continue;
       }

       // do not include files still in fetching
       if (!file.info.owners) {
         continue;
       }
       const owners = [...file.info.owners];
       const ownersKey = owners
           .map(owner => owner.account._account_id)
           .sort()
           .join(',');
       ownersFilesMap.set(
           ownersKey,
           ownersFilesMap.get(ownersKey) || {files: [], owners}
       );
       ownersFilesMap.get(ownersKey).files.push(fileInfo);
     }
     const groupedItems = [];
     for (const ownersKey of ownersFilesMap.keys()) {
       const groupName = this.getGroupName(ownersFilesMap.get(ownersKey).files);
       groupedItems.push({
         groupName,
         files: ownersFilesMap.get(ownersKey).files,
         owners: ownersFilesMap.get(ownersKey).owners,
       });
     }

     if (failedToFetchFiles.size > 0) {
       const failedFiles = [...failedToFetchFiles];
       groupedItems.push({
         groupName: this.getGroupName(failedFiles),
         files: failedFiles,
         error: new Error(
             'Failed to fetch code owner info. Try to refresh the page.'),
       });
     }

     return groupedItems;
   }

   getGroupName(files) {
     const fileName = files[0].path.split('/').pop();
     return {
       name: fileName,
       prefix: files.length > 1 ? `+ ${files.length - 1} more` : '',
     };
   }

   isOnLatestPatchset(patchsetId) {
     const latestRevision = this.change.revisions[this.change.current_revision];
     return `${latestRevision._number}` === `${patchsetId}`;
   }

   abort() {
     this.ownersFetcher.abort();
     const codeOwnerApi = new CodeOwnerApi(this.restApi);
     this.codeOwnerCacheApi = new CodeOwnersCacheApi(codeOwnerApi, change);
   }

   async getBranchConfig() {
     return this.codeOwnerCacheApi.getBranchConfig();
   }

   async isCodeOwnerEnabled() {
     if (this.change.status === ChangeStatus.ABANDONED ||
         this.change.status === ChangeStatus.MERGED) {
       return false;
     }
     const config = await this.codeOwnerCacheApi.getBranchConfig();
     return config && !config.disabled;
   }

   static getOwnerService(restApi, change) {
     if (!this.ownerService || this.ownerService.change !== change) {
       this.ownerService = new CodeOwnerService(restApi, change, {
         // Chrome has a limit of 6 connections per host name, and a max of 10 connections.
         maxConcurrentRequests: 6,
       });
       this.ownerService.prefetch();
     }
     return this.ownerService;
   }
 }
	/**
	* @license
	* Copyright (C) 2020 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	/**
	* All statuses returned for owner status.
	*
	* @enum
	*/
	export const OwnerStatus = {
	INSUFFICIENT_REVIEWERS: 'INSUFFICIENT_REVIEWERS',
	PENDING: 'PENDING',
	APPROVED: 'APPROVED',
	};

	/**
	* @enum
	*/
	const FetchStatus = {
	NOT_STARTED: 0,
	FETCHING: 1,
	FINISHED: 2,
	ABORT: 3,
	};

	/**
	* Specifies status for a change. The same as ChangeStatus enum in gerrit
	*
	* @enum
	*/
	const ChangeStatus = {
	ABANDONED: 'ABANDONED',
	MERGED: 'MERGED',
	NEW: 'NEW',
	};

	/**
	* @enum
	*/
	const UserRole = {
	ANONYMOUS: 'ANONYMOUS',
	AUTHOR: 'AUTHOR',
	CHANGE_OWNER: 'CHANGE_OWNER',
	REVIEWER: 'REVIEWER',
	CC: 'CC',
	REMOVED_REVIEWER: 'REMOVED_REVIEWER',
	OTHER: 'OTHER',
	};

	/**
	* Responsible for communicating with the rest-api
	*
	* @see resources/Documentation/rest-api.md
	*/
	class CodeOwnerApi {
	constructor(restApi) {
	this.restApi = restApi;
	}

	/**
	* Returns a promise fetching the owner statuses for all files within the change.
	*
	* @doc https://gerrit.googlesource.com/plugins/code-owners/+/refs/heads/master/resources/Documentation/rest-api.md#change-endpoints
	* @param {string} changeId
	*/
	listOwnerStatus(changeId) {
	return this.restApi.get(`/changes/${changeId}/code_owners.status`);
	}

	/**
	* Returns a promise fetching the owners for a given path.
	*
	* @doc https://gerrit.googlesource.com/plugins/code-owners/+/refs/heads/master/resources/Documentation/rest-api.md#list-code-owners-for-path-in-branch
	* @param {string} changeId
	* @param {string} path
	*/
	listOwnersForPath(changeId, path) {
	return this.restApi.get(
	`/changes/${changeId}/revisions/current/code_owners` +
	`/${encodeURIComponent(path)}?limit=5&o=DETAILS`
	);
	}

	/**
	* Returns a promise fetching the owners config for a given path.
	*
	* @doc https://gerrit.googlesource.com/plugins/code-owners/+/refs/heads/master/resources/Documentation/rest-api.md#branch-endpoints
	* @param {string} project
	* @param {string} branch
	* @param {string} path
	*/
	getConfigForPath(project, branch, path) {
	return this.restApi.get(
	`/projects/${encodeURIComponent(project)}/` +
	`branches/${encodeURIComponent(branch)}/` +
	`code_owners.config/${encodeURIComponent(path)}`
	);
	}

	/**
	* Returns a promise fetching the owners config for a given branch.
	*
	* @doc https://gerrit.googlesource.com/plugins/code-owners/+/refs/heads/master/resources/Documentation/rest-api.md#branch-endpoints
	* @param {string} project
	* @param {string} branch
	*/
	async getBranchConfig(project, branch) {
	const config = await this.restApi.get(
	`/projects/${encodeURIComponent(project)}/` +
	`branches/${encodeURIComponent(branch)}/` +
	`code_owners.branch_config`
	);
	if (config.override_approval && !(config.override_approval instanceof Array)) {
	// In the upcoming backend changes, the override_approval will be changed
	// to array with (possible) multiple items.
	// While this transition is in progress, the frontend supports both API -
	// the old one and the new one.
	return {...config, override_approval: [config.override_approval]};
	}
	return config;
	}
	}

	/**
	* Wrapper around codeOwnerApi, sends each requests only once and then cache
	* the response. A new CodeOwnersCacheApi instance is created every time when a
	* new change object is assigned.
	* Gerrit never updates existing change object, but instead always assigns a new
	* change object. Particularly, a new change object is assigned when a change
	* is updated and user clicks reload toasts to see the updated change.
	* As a result, the lifetime of a cache is the same as a lifetime of an assigned
	* change object.
	* Periodical cache invalidation can lead to inconsistency in UI, i.e.
	* user can see the old reviewers list (reflects a state when a change was
	* loaded) and code-owners status for the current reviewer list. To avoid
	* this inconsistency, the cache doesn't invalidate.
	*/
	export class CodeOwnersCacheApi {
	constructor(codeOwnerApi, change) {
	this.codeOwnerApi = codeOwnerApi;
	this.change = change;
	this.promises = {};
	}

	_fetchOnce(cacheKey, asyncFn) {
	if (!this.promises[cacheKey]) {
	this.promises[cacheKey] = asyncFn();
	}
	return this.promises[cacheKey];
	}

	getAccount() {
	return this._fetchOnce('getAccount', () => this._getAccount());
	}

	async _getAccount() {
	const loggedIn = await this.codeOwnerApi.restApi.getLoggedIn();
	if (!loggedIn) return undefined;
	return await this.codeOwnerApi.restApi.getAccount();
	}

	listOwnerStatus() {
	return this._fetchOnce('listOwnerStatus',
	() => this.codeOwnerApi.listOwnerStatus(this.change._number));
	}

	getBranchConfig() {
	return this._fetchOnce('getBranchConfig',
	() => this.codeOwnerApi.getBranchConfig(this.change.project,
	this.change.branch));
	}

	listOwnersForPath(path) {
	return this._fetchOnce(`listOwnersForPath:${path}`,
	() => this.codeOwnerApi.listOwnersForPath(this.change.id, path));
	}
	}

	export class OwnersFetcher {
	constructor(restApi, change, options) {
	// fetched files and fetching status
	this._fetchedOwners = new Map();
	this._fetchStatus = FetchStatus.NOT_STARTED;
	this._totalFetchCount = 0;
	this.change = change;
	this.options = options;
	this.codeOwnerApi = new CodeOwnerApi(restApi);
	}

	getStatus() {
	return this._fetchStatus;
	}

	getProgressString() {
	return this._totalFetchCount === 0 ?
	`Loading suggested owners ...` :
	`${this._fetchedOwners.size} out of ${this._totalFetchCount} files have returned suggested owners.`;
	}

	getFiles() {
	const result = [];
	for (const [path, info] of this._fetchedOwners.entries()) {
	result.push({path, info});
	}
	return result;
	}

	async fetchSuggestedOwners(codeOwnerStatusMap) {
	// reset existing temporary storage
	this._fetchedOwners = new Map();
	this._fetchStatus = FetchStatus.FETCHING;
	this._totalFetchCount = 0;

	// only fetch those not approved yet
	const filesGroupByStatus = [...codeOwnerStatusMap.keys()].reduce(
	(list, file) => {
	const status = codeOwnerStatusMap
	.get(file).status;
	if (status === OwnerStatus.INSUFFICIENT_REVIEWERS) {
	list.missing.push(file);
	} else if (status === OwnerStatus.PENDING) {
	list.pending.push(file);
	}
	return list;
	}
	, {pending: [], missing: []});
	// always fetch INSUFFICIENT_REVIEWERS first and then pending
	const filesToFetch = filesGroupByStatus.missing
	.concat(filesGroupByStatus.pending);
	this._totalFetchCount = filesToFetch.length;
	await this._batchFetchCodeOwners(filesToFetch);
	this._fetchStatus = FetchStatus.FINISHED;
	}

	/**
	* Recursively fetches code owners for all files until finished.
	*
	* @param {!Array<string>} files
	*/
	async _batchFetchCodeOwners(files) {
	if (this._fetchStatus === FetchStatus.ABORT) {
	return this._fetchedOwners;
	}

	const batchRequests = [];
	const maxConcurrentRequests = this.options.maxConcurrentRequests;
	for (let i = 0; i < maxConcurrentRequests; i++) {
	const filePath = files[i];
	if (filePath) {
	this._fetchedOwners.set(filePath, {});
	batchRequests.push(this._fetchOwnersForPath(this.change.id, filePath));
	}
	}
	const resPromise = Promise.all(batchRequests);
	await resPromise;
	if (files.length > maxConcurrentRequests) {
	return await this._batchFetchCodeOwners(
	files.slice(maxConcurrentRequests));
	}
	return this._fetchedOwners;
	}

	async _fetchOwnersForPath(changeId, filePath) {
	try {
	const owners = await this.codeOwnerApi.listOwnersForPath(changeId,
	filePath);
	// In the upcoming backend changes, the api will return an object instead
	// of array. While this transition is in progress, the frontend supports
	// both API - the old one and the new one.
	this._fetchedOwners.get(filePath).owners = new Set(
	owners instanceof Array ? owners : owners.code_owners);
	} catch (e) {
	this._fetchedOwners.get(filePath).error = e;
	}
	}

	abort() {
	this._fetchStatus = FetchStatus.ABORT;
	this._fetchedOwners = new Map();
	this._totalFetchCount = 0;
	}
	}

	/**
	* Service for the data layer used in the plugin UI.
	*/
	export class CodeOwnerService {
	constructor(restApi, change, options = {}) {
	this.restApi = restApi;
	this.change = change;
	const codeOwnerApi = new CodeOwnerApi(restApi);
	this.codeOwnerCacheApi = new CodeOwnersCacheApi(codeOwnerApi, change);

	const fetcherOptions = {
	maxConcurrentRequests: options.maxConcurrentRequests \|\| 10,
	};
	this.ownersFetcher = new OwnersFetcher(restApi, change, fetcherOptions);
	}

	/**
	* Prefetch data
	*/
	async prefetch() {
	try {
	await Promise.all([
	this.codeOwnerCacheApi.getAccount(),
	this.getStatus(),
	]);
	} catch {
	// Ignore any errors during prefetch.
	// The same call from a different place throws the same exception
	// again. The CodeOwnerService is not responsible for error processing.
	}
	}

	/**
	* Returns the role of the current user. The returned value reflects the
	* role of the user at the time when the change is loaded.
	* For example, if a user removes themselves as a reviewer, the returned
	* role 'REVIEWER' remains unchanged until the change view is reloaded.
	*/
	async getLoggedInUserInitialRole() {
	const account = await this.codeOwnerCacheApi.getAccount();
	if (!account) {
	return UserRole.ANONYMOUS;
	}
	const change = this.change;
	if (
	change.revisions &&
	change.current_revision &&
	change.revisions[change.current_revision]
	) {
	const commit = change.revisions[change.current_revision].commit;
	if (
	commit &&
	commit.author &&
	account.email &&
	commit.author.email === account.email
	) {
	return UserRole.AUTHOR;
	}
	}
	if (change.owner._account_id === account._account_id) {
	return UserRole.CHANGE_OWNER;
	}
	if (change.reviewers) {
	if (this._accountInReviewers(change.reviewers.REVIEWER, account)) {
	return UserRole.REVIEWER;
	} else if (this._accountInReviewers(change.reviewers.CC, account)) {
	return UserRole.CC;
	} else if (this._accountInReviewers(change.reviewers.REMOVED, account)) {
	return UserRole.REMOVED_REVIEWER;
	}
	}
	return UserRole.OTHER;
	}

	_accountInReviewers(reviewers, account) {
	if (!reviewers) {
	return false;
	}
	return reviewers.some(reviewer =>
	reviewer._account_id === account._account_id);
	}

	async getStatus() {
	const status = await this._getStatus();
	if (status.enabled && !this.isOnLatestPatchset(status.patchsetNumber)) {
	// status is outdated, abort and re-init
	this.abort();
	this.prefetch();
	return await this.codeOwnerCacheApi.getStatus();
	}
	return status;
	}

	async _getStatus() {
	const enabled = await this.isCodeOwnerEnabled();
	if (!enabled) {
	return {
	patchsetNumber: 0,
	enabled: false,
	codeOwnerStatusMap: new Map(),
	rawStatuses: [],
	};
	}

	const onwerStatus = await this.codeOwnerCacheApi.listOwnerStatus();

	return {
	enabled: true,
	patchsetNumber: onwerStatus.patch_set_number,
	codeOwnerStatusMap: this._formatStatuses(
	onwerStatus.file_code_owner_statuses
	),
	rawStatuses: onwerStatus.file_code_owner_statuses,
	};
	}

	async areAllFilesApproved() {
	const {rawStatuses} = await this.getStatus();
	return !rawStatuses.some(status => {
	const oldPathStatus = status.old_path_status;
	const newPathStatus = status.new_path_status;
	// For deleted files, no new_path_status exists
	return (newPathStatus && newPathStatus.status !== OwnerStatus.APPROVED)
	\|\| (oldPathStatus && oldPathStatus.status !== OwnerStatus.APPROVED);
	});
	}

	/**
	* Gets owner suggestions.
	*
	* @returns {{
	* finished?: boolean,
	* progress?: string,
	* suggestions: Array<{
	* groupName: {
	* name: string,
	* prefix: string
	* },
	* error?: Error,
	* owners?: Array,
	* files: Array,
	* }>
	* }}
	*/
	async getSuggestedOwners() {
	const {codeOwnerStatusMap} = await this.getStatus();

	// In case its aborted due to outdated patches
	// should kick start the fetching again
	// Note: we currently are not reusing the instance when switching changes,
	// so if its `abort` due to different changes, the whole instance will be
	// outdated and not used.
	if (this.ownersFetcher.getStatus() === FetchStatus.NOT_STARTED
	\|\| this.ownersFetcher.getStatus() === FetchStatus.ABORT) {
	await this.ownersFetcher.fetchSuggestedOwners(codeOwnerStatusMap);
	}

	return {
	finished: this.ownersFetcher.getStatus() === FetchStatus.FINISHED,
	status: this.ownersFetcher.getStatus(),
	progress: this.ownersFetcher.getProgressString(),
	suggestions: this._groupFilesByOwners(codeOwnerStatusMap,
	this.ownersFetcher.getFiles()),
	};
	}

	async getSuggestedOwnersProgress() {
	const {codeOwnerStatusMap} = await this.getStatus();
	return {
	finished: this.ownersFetcher.getStatus() === FetchStatus.FINISHED,
	status: this.ownersFetcher.getStatus(),
	progress: this.ownersFetcher.getProgressString(),
	suggestions: this._groupFilesByOwners(codeOwnerStatusMap,
	this.ownersFetcher.getFiles()),
	};
	}

	_formatStatuses(statuses) {
	// convert the array of statuses to map between file path -> status
	return statuses.reduce((prev, cur) => {
	const newPathStatus = cur.new_path_status;
	const oldPathStatus = cur.old_path_status;
	if (oldPathStatus) {
	prev.set(oldPathStatus.path, {
	changeType: cur.change_type,
	status: oldPathStatus.status,
	newPath: newPathStatus ? newPathStatus.path : null,
	});
	}
	if (newPathStatus) {
	prev.set(newPathStatus.path, {
	changeType: cur.change_type,
	status: newPathStatus.status,
	oldPath: oldPathStatus ? oldPathStatus.path : null,
	});
	}
	return prev;
	}, new Map());
	}

	_computeFileStatus(fileStatusMap, path) {
	// empty for modified files and old-name files
	// Show `Renamed` for renamed file
	const status = fileStatusMap.get(path);
	if (status.oldPath) {
	return 'Renamed';
	}
	return;
	}

	_groupFilesByOwners(codeOwnerStatusMap, files) {
	// Note: for renamed or moved files, they will have two entries in the map
	// we will treat them as two entries when group as well
	const ownersFilesMap = new Map();
	const failedToFetchFiles = new Set();
	for (const file of files) {
	const fileInfo = {
	path: file.path,
	status: this._computeFileStatus(codeOwnerStatusMap, file.path),
	};
	// for files failed to fetch, add them to the special group
	if (file.info.error) {
	failedToFetchFiles.add(fileInfo);
	continue;
	}

	// do not include files still in fetching
	if (!file.info.owners) {
	continue;
	}
	const owners = [...file.info.owners];
	const ownersKey = owners
	.map(owner => owner.account._account_id)
	.sort()
	.join(',');
	ownersFilesMap.set(
	ownersKey,
	ownersFilesMap.get(ownersKey) \|\| {files: [], owners}
	);
	ownersFilesMap.get(ownersKey).files.push(fileInfo);
	}
	const groupedItems = [];
	for (const ownersKey of ownersFilesMap.keys()) {
	const groupName = this.getGroupName(ownersFilesMap.get(ownersKey).files);
	groupedItems.push({
	groupName,
	files: ownersFilesMap.get(ownersKey).files,
	owners: ownersFilesMap.get(ownersKey).owners,
	});
	}

	if (failedToFetchFiles.size > 0) {
	const failedFiles = [...failedToFetchFiles];
	groupedItems.push({
	groupName: this.getGroupName(failedFiles),
	files: failedFiles,
	error: new Error(
	'Failed to fetch code owner info. Try to refresh the page.'),
	});
	}

	return groupedItems;
	}

	getGroupName(files) {
	const fileName = files[0].path.split('/').pop();
	return {
	name: fileName,
	prefix: files.length > 1 ? `+ ${files.length - 1} more` : '',
	};
	}

	isOnLatestPatchset(patchsetId) {
	const latestRevision = this.change.revisions[this.change.current_revision];
	return `${latestRevision._number}` === `${patchsetId}`;
	}

	abort() {
	this.ownersFetcher.abort();
	const codeOwnerApi = new CodeOwnerApi(this.restApi);
	this.codeOwnerCacheApi = new CodeOwnersCacheApi(codeOwnerApi, change);
	}

	async getBranchConfig() {
	return this.codeOwnerCacheApi.getBranchConfig();
	}

	async isCodeOwnerEnabled() {
	if (this.change.status === ChangeStatus.ABANDONED \|\|
	this.change.status === ChangeStatus.MERGED) {
	return false;
	}
	const config = await this.codeOwnerCacheApi.getBranchConfig();
	return config && !config.disabled;
	}

	static getOwnerService(restApi, change) {
	if (!this.ownerService \|\| this.ownerService.change !== change) {
	this.ownerService = new CodeOwnerService(restApi, change, {
	// Chrome has a limit of 6 connections per host name, and a max of 10 connections.
	maxConcurrentRequests: 6,
	});
	this.ownerService.prefetch();
	}
	return this.ownerService;
	}
	}