import * as querystring from 'querystring';
import axios from 'axios';

const RootPath = `authentication/v1`;

interface ITokenCache {
    promise: Promise<string>;
    expires_at: number;
}

export interface ITwoLeggedToken {
    access_token: string;
    expires_in: number;
}

export interface IThreeLeggedToken extends ITwoLeggedToken {
    refresh_token: string;
}

export interface IUserProfile {
    userId: string;
    userName: string;
    emailId: string;
    firstName: string;
    lastName: string;
    emailVerified: boolean;
    '2FaEnabled': boolean;
    countryCode: string;
    language: string;
    optin: boolean;
    lastModified: string;
    websiteUrl: string;
    profileImages: { [key: string]: string };
}

/**
 * Client providing access to Autodesk Forge {@link https://forge.autodesk.com/en/docs/oauth/v2|authentication APIs}.
 * @tutorial authentication
 */
export class AuthenticationClient {
    private client_id: string;
    private client_secret: string;
    private host: string;
    private _cached: { [key: string]: ITokenCache };

    get clientId() { return this.client_id; }

    /**
     * Initializes new client with specific Forge app credentials.
     * @param {string} client_id Forge application client ID. 
     * @param {string} client_secret Forge application client secret.
     * @param {string} [host="https://developer.api.autodesk.com"] Forge API host.
     */
    constructor(client_id: string, client_secret: string, host: string = 'https://developer.api.autodesk.com') {
        this.client_id = client_id;
        this.client_secret = client_secret;
        this.host = host;
        this._cached = {};
    }

    // Helper method for POST requests with urlencoded params
    protected async post(endpoint: string, params: any) {
        return axios.post(this.host + '/' + RootPath + '/' + endpoint, querystring.stringify(params));
    }

    /**
     * Retrieves 2-legged access token for a specific set of scopes
     * ({@link https://forge.autodesk.com/en/docs/oauth/v2/reference/http/authenticate-POST|docs}).
     * Unless the {@see force} parameter is used, the access tokens are cached
     * based on their scopes and the 'expires_in' field in the response.
     * @param {string[]} scopes List of requested {@link https://forge.autodesk.com/en/docs/oauth/v2/developers_guide/scopes|scopes}.
     * @param {boolean} [force] Skip cache, if there is any, and retrieve a new token.
     * @returns {Promise<ITwoLeggedToken>} Promise of 2-legged authentication object containing two fields,
     * 'access_token' with the actual token, and 'expires_in' with expiration time (in seconds).
     */
    authenticate(scopes: string[], force: boolean = false): Promise<ITwoLeggedToken> {
        // Check if there's a cached token, unexpired, and with the same scopes
        const key = 'two-legged/' + scopes.join('/');
        if (!force && key in this._cached) {
            const cache = this._cached[key];
            if (cache.expires_at > Date.now()) {
                return cache.promise.then((token) => ({
                    access_token: token,
                    expires_in: Math.floor((cache.expires_at - Date.now()) / 1000)
                }));
            }
        }

        // Otherwise request a new token and cache it
        const params = {
            'client_id': this.client_id,
            'client_secret': this.client_secret,
            'grant_type': 'client_credentials',
            'scope': scopes.join(' ')
        };
        const cache = this._cached[key] = {
            expires_at: Number.MAX_VALUE,
            promise: this.post('authenticate', params).then((resp) => {
                const { data } = resp;
                this._cached[key].expires_at = Date.now() + data.expires_in * 1000;
                return data.access_token;
            })
        };
        return cache.promise.then((token) => ({
            access_token: token,
            expires_in: Math.floor((cache.expires_at - Date.now()) / 1000)
        }));
    }

    /**
     * Generates a URL for 3-legged authentication.
     * @param {string[]} scopes List of requested {@link https://forge.autodesk.com/en/docs/oauth/v2/developers_guide/scopes|scopes}.
     * @param {string} redirectUri Same redirect URI as defined by the Forge app.
     * @returns {string} Autodesk login URL.
     */
    getAuthorizeRedirect(scopes: string[], redirectUri: string): string {
        return `${this.host}/${RootPath}/authorize?response_type=code&client_id=${this.client_id}&redirect_uri=${redirectUri}&scope=${scopes.join(' ')}`;
    }

    /**
     * Exchanges 3-legged authentication code for an access token
     * ({@link https://forge.autodesk.com/en/docs/oauth/v2/reference/http/gettoken-POST|docs}).
     * @async
     * @param {string} code Authentication code returned from the Autodesk login process.
     * @param {string} redirectUri Same redirect URI as defined by the Forge app.
     * @returns {Promise<IThreeLeggedToken>} Promise of 3-legged authentication object containing
     * 'access_token', 'refresh_token', and 'expires_in' with expiration time (in seconds).
     */
    async getToken(code: string, redirectUri: string): Promise<IThreeLeggedToken> {
        const params = {
            'client_id': this.client_id,
            'client_secret': this.client_secret,
            'grant_type': 'authorization_code',
            'code': code,
            'redirect_uri': redirectUri
        };
        const resp = await this.post(`gettoken`, params);
        return resp.data;
    }

    /**
     * Refreshes 3-legged access token
     * ({@link https://forge.autodesk.com/en/docs/oauth/v2/reference/http/refreshtoken-POST}).
     * @async
     * @param {string[]} scopes List of requested {@link https://forge.autodesk.com/en/docs/oauth/v2/developers_guide/scopes|scopes}.
     * @param {string} refreshToken Refresh token.
     * @returns {Promise<IThreeLeggedToken>} Promise of 3-legged authentication object containing
     * 'access_token', 'refresh_token', and 'expires_in' with expiration time (in seconds).
     */
    async refreshToken(scopes: string[], refreshToken: string): Promise<IThreeLeggedToken> {
        const params = {
            'client_id': this.client_id,
            'client_secret': this.client_secret,
            'grant_type': 'refresh_token',
            'refresh_token': refreshToken,
            'scope': scopes.join(' ')
        };
        const resp = await this.post(`refreshtoken`, params);
        return resp.data;
    }

    /**
     * Gets profile information for a user based on their 3-legged auth token
     * ({@link https://forge.autodesk.com/en/docs/oauth/v2/reference/http/users-@me-GET|docs}).
     * @async
     * @param {string} token 3-legged authentication token.
     * @returns {Promise<IUserProfile>} User profile information.
     */
    async getUserProfile(token: string): Promise<IUserProfile> {
        const config = {
            headers: {
                'Authorization': 'Bearer ' + token
            }
        };
        const resp = await axios.get(this.host + '/userprofile/v1/users/@me', config);
        return resp.data;
    }
}