// ******************************************************************************
// Copyright 2024 TypeFox GmbH
// This program and the accompanying materials are made available under the
// terms of the MIT License, which is available in the project root.
// ******************************************************************************

import { inject, injectable, postConstruct } from 'inversify';
import { User, isUser } from './types.js';
import { UserManager } from './user-manager.js';
import * as jose from 'jose';
import { nanoid, customAlphabet } from 'nanoid';
import { Disposable, Emitter, Event } from 'open-collaboration-protocol';
import { Logger } from './utils/logging.js';
import { UserInfo } from './auth-endpoints/auth-endpoint.js';
import { Configuration } from './utils/configuration.js';
import { getLocalFilename } from './collaboration-server.js';

export interface DelayedAuth extends Disposable {
    update(jwt: string): void;
    onUpdate: Event<string>;
    onFail: Event<Error>;
    jwt?: string;
}

@injectable()
export class CredentialsManager {

    @inject(UserManager)
    protected readonly userManager: UserManager;

    @inject(Logger) protected logger: Logger;

    @inject(Configuration) protected configuration: Configuration;

    protected deferredAuths = new Map<string, DelayedAuth>();
    protected nanoid = this.generateAlphabet();

    @postConstruct()
    initialize() {
        if (this.configuration.getValue('oct-jwt-private-key') === undefined) {
            this.logger.warn('OCT_JWT_PRIVATE_KEY env variable is not set. Using a static key for development purposes.');
        }
    }

    async confirmUser(confirmToken: string, user: UserInfo): Promise<string> {
        const auth = this.deferredAuths.get(confirmToken);
        if (!auth) {
            throw this.logger.createErrorAndLog('Login timed out');
        }
        const registeredUser = await this.userManager.registerUser(user);
        const userClaim: User = {
            id: registeredUser.id,
            name: registeredUser.name,
            email: registeredUser.email,
            authProvider: registeredUser.authProvider
        };
        this.logger.info(`Will generate JWT for user [id: ${userClaim.id} | name: ${userClaim.name} | email: ${userClaim.email}]`);
        const jwt = await this.generateJwt(userClaim);
        auth.update(jwt);
        return jwt;
    }

    async startAuth(): Promise<string> {
        const confirmToken = this.secureId();
        const updateEmitter = new Emitter<string>();
        const failureEmitter = new Emitter<Error>();
        const dispose = () => {
            clearTimeout(timeout);
            this.deferredAuths.delete(confirmToken);
            updateEmitter.dispose();
            failureEmitter.dispose();
        };
        const timeout = setTimeout(() => {
            failureEmitter.fire(new Error('Request timed out'));
            dispose();
        }, 300_000); // 5 minutes of timeout
        const delayedAuth: DelayedAuth = {
            update: jwt => {
                delayedAuth.jwt = jwt;
                updateEmitter.fire(jwt);
            },
            onUpdate: updateEmitter.event,
            onFail: failureEmitter.event,
            dispose
        };
        this.deferredAuths.set(confirmToken, delayedAuth);
        return confirmToken;
    }

    async getAuth(confirmToken: string): Promise<DelayedAuth | undefined> {
        return this.deferredAuths.get(confirmToken);
    }

    async getUser(token: string): Promise<User | undefined> {
        const user = await this.verifyJwt(token, isUser);
        if (typeof user.id !== 'string' || typeof user.name !== 'string') {
            throw this.logger.createErrorAndLog('User token is not valid');
        }
        return user;
    }

    async verifyJwt<T extends object>(jwt: string, verify: (obj: unknown) => obj is T): Promise<T> {
        const key = this.getJwtPrivateKey();
        const { payload } = await jose.jwtVerify(jwt, key);
        if (verify(payload)) {
            return payload;
        } else {
            throw this.logger.createErrorAndLog('JWT payload is not valid');
        }
    }

    protected getJwtPrivateKey(): Uint8Array {
        const key = this.configuration.getValue('oct-jwt-private-key') ?? getLocalFilename(import.meta.url);
        return Buffer.from(key);
    }

    async generateJwt(payload: object): Promise<string> {
        const [key, expiration] = await Promise.all([
            this.getJwtPrivateKey(),
            this.getJwtExpiration()
        ]);
        const signJwt = new jose.SignJWT(payload as jose.JWTPayload)
            .setProtectedHeader({ alg: 'HS256' })
            .setIssuedAt();
        if (expiration !== undefined) {
            signJwt.setExpirationTime(expiration);
        }
        return signJwt.sign(key);
    }

    protected async getJwtExpiration(): Promise<string | number | undefined> {
        return undefined;
    }

    protected generateAlphabet(): typeof nanoid {
        let alphabet = '';
        for (let digit = 48 /* '0' */; digit <= 57 /* '9' */; digit++) {
            alphabet += String.fromCharCode(digit);
        }
        for (let letter = 65 /* 'A' */; letter <= 90 /* 'Z' */; letter++) {
            alphabet += String.fromCharCode(letter);
        }
        for (let letter = 97 /* 'a' */; letter <= 122 /* 'z' */; letter++) {
            alphabet += String.fromCharCode(letter);
        }
        return customAlphabet(alphabet, 24);
    }

    secureId(): string {
        return this.nanoid(24);
    }
}