"use strict";

const cl = global.botanLoader;
const Dragonfly = global.Dragonfly;

const crypto = require( "crypto" );
const util = require( "util" );
const EventEmitter = require( "events" ).EventEmitter;
const http = require( "http" );
const HttpRequest = cl.load( "botanss.net.HttpRequest" );

class SignInEventArgs
{
	constructor({ message, redirect, data = [], success = false } = {})
	{
		this.success = success;
		this._message = message;
		this._redirect = redirect;
		this.data = data
	}

	get message()
	{
		return this._message;
	}

	get location()
	{
		return this._redirect + "?" + this.data.join( "&" );
	}
}

class Signin extends EventEmitter
{
	/** Conf structure
	 * {
	 *   "spec": process.env.OPENID_SPEC_URI
	 *   , "authorization_endpoint_params": {
	 *     "client_id": process.env.AZURE_AD_CLIENT_ID
	 *     , "redirect_url": `https://${HOST_NAME}/user/login/`
	 *     , "nonce": "{RANDSTR}"
	 *     , "state": "{RANDSTR}"
	 *     , "scope": "openid profile email"
	 *     , "response_mode": "form_post"
	 *     , "response_type": "id_token"
	 *   }
	 *   , "end_session_endpoint_params": {
	 *   "post_logout_redirect_uri": `https://${HOST_NAME}/user/logout/`
	 * }
	 *
	 * NOTE:
	 *   set Signin().RANDSTR = () => SecureRandStr(); to enable custom templated functions
	 *   * Only support "^{FUNCTION_NAME}$" for now
	 **/
	constructor( conf )
	{
		super();
		this.conf = conf;
		this.spec = null;
	}

	Start( action, params, handler )
	{
		var request = new HttpRequest( this.conf.spec );
		var _self = this;

		if( this.spec )
		{
			_self[ action ]( params, handler );
		}
		else
		{
			request.addListener( "RequestComplete", function( sender, e )
			{
				if( e.statusCode == 200 )
				{
					_self.spec = JSON.parse( e.ResponseString );
					_self[ action ]( params, handler );
				}
			} );
			request.Send();
		}
	}

	ValidateAzureAD( params, handler )
	{
		if( !this.spec )
			throw new Error( "OpenID spec is not present" );

		var _self = this;

		var jwt = params[ "id_token" ];
		if( !jwt )
		{
			handler( this, new SignInEventArgs({
				"message": params[ "error_description" ]
			}) );
			return;
		}

		var [ jHeader, jPayload, jSig ] = jwt.split( "." );

		var header = JSON.parse( Buffer.from( jHeader, "base64" ) );
		var payload = JSON.parse( Buffer.from( jPayload, "base64" ) );

		var aud = payload[ "aud" ];
		var clientId = this.conf.authorization_endpoint_params.client_id;

		if( aud !== clientId )
		{
			handler( this, new SignInEventArgs({ message: `aud mismatched: ${aud}` }) );
			return;
		}

		var [ url, data ] = this._endPointRes( "jwks_uri" );

		var request = new HttpRequest( url + "?" + data.join( "&" ) );
		request.addListener( "RequestComplete", function( sender, e )
		{
			var eArgs;

			if( e.statusCode == 200 )
			{
				var respJson = JSON.parse( e.ResponseString );
				var keyId = header[ "kid" ];

				for( let key of respJson[ "keys" ] )
				{
					if( key[ "kid" ] === keyId )
					{
						var hashFunc = crypto.createVerify({
							"RS256": "RSA-SHA256"
						}[ header[ "alg" ] ]);

						hashFunc.write( `${jHeader}.${jPayload}` );
						hashFunc.end();

						var pub = crypto.createPublicKey({
							"key": {
								"kty": key["kty"]
								, "n": key["n"]
								, "e": key["e"]
							}, "format": "jwk"
						});

						eArgs = new SignInEventArgs(
						{
							"success": hashFunc.verify( pub, jSig, "base64" )
							, "data": payload
						});
						break;
					}
				}

				eArgs = eArgs || new SignInEventArgs({
					"message": `Unable to find key: ${keyId}`
				});
			}
			else
			{
				eArgs = new SignInEventArgs({
					"message": `Remote returned ${e.statusCode}`
				});
			}

			handler( _self, eArgs );
		});

		request.Send();
	}

	Authorize( params, handler )
	{
		var [ url, data ] = this._endPointRes( "authorization_endpoint" );
		var eArgs = new SignInEventArgs({ "redirect": url, "data": data });
		handler( this, eArgs );
	}

	Logout( params, handler )
	{
		var [ url, data ] = this._endPointRes( "end_session_endpoint" );
		var eArgs = new SignInEventArgs({ "redirect": url, "data": data });
		handler( this, eArgs );
	}

	_endPointRes( endpoint, handler )
	{
		if( !this.spec )
			throw new Error( "OpenID spec is not present" );

		var url = this.spec[ endpoint ];
		if( !url )
			throw new Error( "No such endpoint" );

		var params = this.conf[ endpoint + "_params" ];
		var requestData = [];

		if( params )
		{
			for( var name in params )
			{
				var val = params[ name ];

				if( val[0] == "{" )
				{
					val = this[ val.replace( "{", "" ).replace( "}", "" ) ]();
				}

				requestData.push( name + "=" + encodeURIComponent( val ) );
			}
		}

		return [ url, requestData ];
	}
}

module.exports = Signin;