/*---------------------------------------------------------------------------------------------
 *  Copyright (c) Microsoft Corporation. All rights reserved.
 *  Licensed under the MIT License. See License.txt in the project root for license information.
 *--------------------------------------------------------------------------------------------*/

import * as vscode from 'vscode';
import { v4 as uuid } from 'uuid';
import { Keychain } from './common/keychain';
import { GitHubServer, NETWORK_ERROR } from './githubServer';
import Logger from './common/logger';
import { arrayEquals } from './common/utils';
import { ExperimentationTelemetry } from './experimentationService';

export const onDidChangeSessions = new vscode.EventEmitter<vscode.AuthenticationProviderAuthenticationSessionsChangeEvent>();

interface SessionData {
	id: string;
	account?: {
		label?: string;
		displayName?: string;
		id: string;
	}
	scopes: string[];
	accessToken: string;
}

export class GitHubAuthenticationProvider {
	private _sessions: vscode.AuthenticationSession[] = [];
	private _githubServer: GitHubServer;

	private _keychain: Keychain;

	constructor(context: vscode.ExtensionContext, telemetryReporter: ExperimentationTelemetry) {
		this._keychain = new Keychain(context);
		this._githubServer = new GitHubServer(telemetryReporter);
	}

	public async initialize(context: vscode.ExtensionContext): Promise<void> {
		try {
			this._sessions = await this.readSessions();
			await this.verifySessions();
		} catch (e) {
			// Ignore, network request failed
		}

		context.subscriptions.push(context.secrets.onDidChange(() => this.checkForUpdates()));
	}

	async getSessions(scopes?: string[]): Promise<vscode.AuthenticationSession[]> {
		return scopes
			? this._sessions.filter(session => arrayEquals(session.scopes, scopes))
			: this._sessions;
	}

	private async verifySessions(): Promise<void> {
		const verifiedSessions: vscode.AuthenticationSession[] = [];
		const verificationPromises = this._sessions.map(async session => {
			try {
				await this._githubServer.getUserInfo(session.accessToken);
				this._githubServer.checkIsEdu(session.accessToken);
				verifiedSessions.push(session);
			} catch (e) {
				// Remove sessions that return unauthorized response
				if (e.message !== 'Unauthorized') {
					verifiedSessions.push(session);
				}
			}
		});

		Promise.all(verificationPromises).then(_ => {
			if (this._sessions.length !== verifiedSessions.length) {
				this._sessions = verifiedSessions;
				this.storeSessions();
			}
		});
	}

	private async checkForUpdates() {
		let storedSessions: vscode.AuthenticationSession[];
		try {
			storedSessions = await this.readSessions();
		} catch (e) {
			// Ignore, network request failed
			return;
		}

		const added: vscode.AuthenticationSession[] = [];
		const removed: vscode.AuthenticationSession[] = [];

		storedSessions.forEach(session => {
			const matchesExisting = this._sessions.some(s => s.id === session.id);
			// Another window added a session to the keychain, add it to our state as well
			if (!matchesExisting) {
				Logger.info('Adding session found in keychain');
				this._sessions.push(session);
				added.push(session);
			}
		});

		this._sessions.map(session => {
			const matchesExisting = storedSessions.some(s => s.id === session.id);
			// Another window has logged out, remove from our state
			if (!matchesExisting) {
				Logger.info('Removing session no longer found in keychain');
				const sessionIndex = this._sessions.findIndex(s => s.id === session.id);
				if (sessionIndex > -1) {
					this._sessions.splice(sessionIndex, 1);
				}

				removed.push(session);
			}
		});

		if (added.length || removed.length) {
			onDidChangeSessions.fire({ added, removed, changed: [] });
		}
	}

	private async readSessions(): Promise<vscode.AuthenticationSession[]> {
		const storedSessions = await this._keychain.getToken() || await this._keychain.tryMigrate();
		if (storedSessions) {
			try {
				const sessionData: SessionData[] = JSON.parse(storedSessions);
				const sessionPromises = sessionData.map(async (session: SessionData): Promise<vscode.AuthenticationSession> => {
					const needsUserInfo = !session.account;
					let userInfo: { id: string, accountName: string };
					if (needsUserInfo) {
						userInfo = await this._githubServer.getUserInfo(session.accessToken);
					}

					return {
						id: session.id,
						account: {
							label: session.account
								? session.account.label || session.account.displayName!
								: userInfo!.accountName,
							id: session.account?.id ?? userInfo!.id
						},
						scopes: session.scopes,
						accessToken: session.accessToken
					};
				});

				return Promise.all(sessionPromises);
			} catch (e) {
				if (e === NETWORK_ERROR) {
					return [];
				}

				Logger.error(`Error reading sessions: ${e}`);
				await this._keychain.deleteToken();
			}
		}

		return [];
	}

	private async storeSessions(): Promise<void> {
		await this._keychain.setToken(JSON.stringify(this._sessions));
	}

	get sessions(): vscode.AuthenticationSession[] {
		return this._sessions;
	}

	public async createSession(scopes: string): Promise<vscode.AuthenticationSession> {
		const token = await this._githubServer.login(scopes);
		const session = await this.tokenToSession(token, scopes.split(' '));
		this._githubServer.checkIsEdu(token);
		await this.setToken(session);
		return session;
	}

	public async manuallyProvideToken(): Promise<void> {
		this._githubServer.manuallyProvideToken();
	}

	private async tokenToSession(token: string, scopes: string[]): Promise<vscode.AuthenticationSession> {
		const userInfo = await this._githubServer.getUserInfo(token);
		return {
			id: uuid(),
			accessToken: token,
			account: { label: userInfo.accountName, id: userInfo.id },
			scopes
		};
	}

	private async setToken(session: vscode.AuthenticationSession): Promise<void> {
		const sessionIndex = this._sessions.findIndex(s => s.id === session.id);
		if (sessionIndex > -1) {
			this._sessions.splice(sessionIndex, 1, session);
		} else {
			this._sessions.push(session);
		}

		await this.storeSessions();
	}

	public async removeSession(id: string): Promise<vscode.AuthenticationSession | undefined> {
		Logger.info(`Logging out of ${id}`);
		const sessionIndex = this._sessions.findIndex(session => session.id === id);
		let session: vscode.AuthenticationSession | undefined;
		if (sessionIndex > -1) {
			session = this._sessions[sessionIndex];
			this._sessions.splice(sessionIndex, 1);
		} else {
			Logger.error('Session not found');
		}

		await this.storeSessions();
		return session;
	}
}