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Merge pull request #34 from aoberoi/async-dispatch
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Async dispatch
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@aoberoi
aoberoi committed Mar 20, 2019
1 parent 3aeaa03 commit a8b3ff0
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Showing 4 changed files with 352 additions and 157 deletions.
213 changes: 150 additions & 63 deletions packages/node-slack-interactive-messages/src/adapter.js
View file
Expand Up @@ -100,11 +100,16 @@ export default class SlackMessageAdapter {
debug('instantiated');
}

/* Interface for using the built-in server */

/**
* Create a server that's ready to serve requests from Slack's interactive messages.
* Create a server that dispatches Slack's interactive message actions and menu requests to this
* message adapter instance. Use this method if your application will handle starting the server.
*
* @param {string} [path=/slack/actions] - The path portion of the URL where the server will
* listen for requests from Slack's interactive messages.
* @returns - A promise that resolves to an instance of http.Server and will dispatch interactive
* message actions and options requests to this message adapter instance
*/
createServer(path = '/slack/actions') {
// TODO: more options (like https)
Expand All @@ -123,6 +128,13 @@ export default class SlackMessageAdapter {
});
}

/**
* Start a built-in server that dispatches Slack's interactive message actions and menu requests
* to this message adapter interface.
*
* @param {number} port
* @requires {Promise<void>} - A promise that resolves once the server is ready
*/
start(port) {
return this.createServer()
.then(server => new Promise((resolve, reject) => {
Expand All @@ -133,6 +145,11 @@ export default class SlackMessageAdapter {
}));
}

/**
* Stop the previously started built-in server.
*
* @returns {Promise<void>} - A promise that resolves once the server is cleaned up.
*/
stop() {
return new Promise((resolve, reject) => {
if (this.server) {
Expand All @@ -150,10 +167,30 @@ export default class SlackMessageAdapter {
});
}

/* Interface for bringing your own server */

/**
* Create a middleware function that can be used to integrate with the `express` web framework
* in order for incoming requests to be dispatched to this message adapter instance.
*
* @returns {ExpressMiddlewareFunc} - A middleware function
*/
expressMiddleware() {
return createExpressMiddleware(this);
}

/* Interface for adding handlers */

/**
* Add a handler for an interactive message action.
*
* @param {Object|string|RegExp} matchingConstraints - the callback ID (as a string or RegExp) or
* an object describing the constrants to select actions for the handler.
* @param {string|RegExp} matchingConstraints.callbackId
* @param {string} matchingConstraints.type
* @param {boolean} matchingConstraints.unfurl
* @param {ActionHandler} callback
*/
action(matchingConstraints, callback) {
const actionConstraints = formatMatchingConstraints(matchingConstraints);

Expand All @@ -167,6 +204,16 @@ export default class SlackMessageAdapter {
return this.registerCallback(actionConstraints, callback);
}

/**
* Add a handler for an options request
*
* @param {*} matchingConstraints - the callback ID (as a string or RegExp) or
* an object describing the constrants to select options requests for the handler.
* @param {string|RegExp} matchingConstraints.callbackId
* @param {string} matchingConstraints.type
* @param {boolean} matchingConstraints.unfurl
* @param {OptionsHandler} callback
*/
options(matchingConstraints, callback) {
const optionsConstraints = formatMatchingConstraints(matchingConstraints);

Expand All @@ -179,28 +226,23 @@ export default class SlackMessageAdapter {
return this.registerCallback(optionsConstraints, callback);
}

/* @private */

registerCallback(constraints, callback) {
// Validation
if (!isFunction(callback)) {
debug('did not register callback because its not a function');
throw new TypeError('callback must be a function');
}

this.callbacks.push([constraints, callback]);

return this;
}
/* Interface for HTTP servers (like express middleware) */

/**
* Dispatches the contents of an HTTP request to the registered handlers.
*
* @param {object} payload
* @returns {Promise<{ status: number, content: object|string|undefined }>|undefined} - A promise
* of the response information (an object with status and content that is a JSON serializable
* object or a string or undefined) for the request. An undefined return value indicates that the
* request was not matched.
*/
dispatch(payload) {
const action = payload.actions && payload.actions[0];

// The following result value represents:
// * "no replacement" for message actions
// * "submission is valid" for dialog submissions
// * "no suggestions" for menu options TODO: check that this is true
let result = { status: 200, content: '' };
const callback = this.matchCallback(payload);
if (!callback) {
return undefined;
}
const [, callbackFn] = callback;

// when a response_url is present,`respond()` function created to to send a message using it
let respond;
Expand All @@ -214,12 +256,70 @@ export default class SlackMessageAdapter {
};
}

this.callbacks.some(([constraints, fn]) => {
// Returning false in this function continues the iteration, and returning true ends it.
// The pattern is that we assign a value to `result` and then return true. We only desire one
// result for the response.
let callbackResult;
let callbackResult;
try {
callbackResult = callbackFn.call(this, payload, respond);
} catch (error) {
debug('callback error: %o', error);
return Promise.resolve({ status: 500 });
}

if (callbackResult) {
return promiseTimeout(this.syncResponseTimeout, callbackResult)
.then(content => ({ status: 200, content }))
.catch((error) => {
if (error.code === utilErrorCodes.PROMISE_TIMEOUT) {
// warn and continue for promises that cannot be saved with a later async response.
// this includes dialog submissions because the response_url doesn't have the same
// semantics as the response, any request that doesn't contain a response_url, and
// if this has been explicitly disabled in the configuration.
if (!this.lateResponseFallbackEnabled || !respond || payload.type === 'dialog_submission') {
debug('WARNING: The response Promise did not resolve under the timeout.');
return callbackResult
.then(content => ({ status: 200, content }))
.catch(() => ({ status: 500 }));
}

// save a late promise by sending an empty body in the response, and then use the
// response_url to send the eventually resolved value
callbackResult.then(respond).catch((callbackError) => {
// when the promise is late and fails, we cannot do anything but log it
debug('ERROR: Promise was late and failed. Use `.catch()` to handle errors.');
throw callbackError;
});
return { status: 200 };
}

return { status: 500 };
});
}

// The following result value represents:
// * "no replacement" for message actions
// * "submission is valid" for dialog submissions
// * "no suggestions" for menu options TODO: check that this is true
return Promise.resolve({ status: 200 });
}

/* @private */

registerCallback(constraints, callback) {
// Validation
if (!isFunction(callback)) {
debug('did not register callback because its not a function');
throw new TypeError('callback must be a function');
}

this.callbacks.push([constraints, callback]);

return this;
}


matchCallback(payload) {
const action = payload.actions && payload.actions[0];
return this.callbacks.find(([constraints]) => {
// if the callback ID constraint is specified, only continue if it matches
if (constraints.callbackId) {
if (isString(constraints.callbackId) && payload.callback_id !== constraints.callbackId) {
return false;
Expand All @@ -229,10 +329,12 @@ export default class SlackMessageAdapter {
}
}

// if the action constraint is specified, only continue if it matches
if (action && constraints.type && constraints.type !== action.type) {
return false;
}

// if the unfurl constraint is specified, only continue if it matches
if ('unfurl' in constraints &&
(
(constraints.unfurl && !payload.is_app_unfurl) ||
Expand All @@ -242,44 +344,29 @@ export default class SlackMessageAdapter {
return false;
}

try {
callbackResult = fn.call(this, payload, respond);
} catch (error) {
debug('callback error: %o', error);
result = { status: 500 };
return true;
}

if (callbackResult) {
const contentConsideringTimeout = promiseTimeout(this.syncResponseTimeout, callbackResult)
.catch((error) => {
if (error.code === utilErrorCodes.PROMISE_TIMEOUT) {
// don't save late promises for dialog submission, the response_url doesn't do the
// same thing as the response. developer should be warned that the promise is taking
// too much time
if (!this.lateResponseFallbackEnabled || !respond || payload.type === 'dialog_submission') {
debug('WARNING: The response Promise did not resolve under the timeout.');
return callbackResult;
}

// save a late promise by sending an empty body in the response, and then using the
// response_url to send the eventually resolved value
callbackResult.then(respond).catch((callbackError) => {
// when the promise is late and fails, won't send it to the response_url, log it
debug('ERROR: Promise was late and failed. Use `.catch()` to handle errors.');
throw callbackError;
});
return '';
}
// NOTE: this should either not happen or be configurable
return 'An error occurred. Please report this to the app developer.';
});
result = { status: 200, content: contentConsideringTimeout };
return true;
}
// if there's no reason to eliminate this callback, then its a match!
return true;
});

return result;
}
}

/**
* @name ExpressMiddlewareFunc
* @function
* @param {http.IncomingMessage} req
* @param {http.ServerResponse} res
* @param {function} next
*/

/**
* @name ActionHandler
* @function
* @param {object} payload
* @param {function} respond
*/

/**
* @name OptionsHandler
* @function
* @param {object} payload
*/
42 changes: 17 additions & 25 deletions packages/node-slack-interactive-messages/src/express-middleware.js
View file
Expand Up @@ -15,29 +15,17 @@ export function createExpressMiddleware(adapter) {
function sendResponse(res) {
return function _sendResponse(dispatchResult) {
const { status, content } = dispatchResult;
const contentReady = (content && typeof content.then === 'function') ? content : Promise.resolve(content);
return contentReady.then((c) => {
res.status(status);
res.set('X-Slack-Powered-By', poweredBy);
if (typeof c === 'string') {
res.send(c);
} else if (c) {
res.json(c);
} else {
res.end();
}
return new Promise((resolve, reject) => {
res.on('finish', () => {
// res._headers is an undocumented property, but we feel comfortable using it because:
// 1. express depends on it and express is so foundational in node
// 2. this is logging code and the risk of this causing a break is minimal
// eslint-disable-next-line no-underscore-dangle
debug('response finished - status: %d, headers: %o', res.statusCode, res._headers);
resolve(res);
});
res.on('error', reject);
});
});

res.status(status);
res.set('X-Slack-Powered-By', poweredBy);

if (typeof content === 'string') {
res.send(content);
} else if (content) {
res.json(content);
} else {
res.end();
}
};
}

Expand Down Expand Up @@ -73,7 +61,11 @@ export function createExpressMiddleware(adapter) {
}
debug('request token verification success');

respond(adapter.dispatch(payload))
.catch(next);
const dispatchResult = adapter.dispatch(payload);
if (dispatchResult) {
dispatchResult.then(respond);
} else {
next();
}
};
}

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