How To Promisify Moltin APIs

If you’ve read my last post, then you know that I am having all kinds of geeky fun with Moltin and its APIs. Today I will show you how you can quickly promisify them all.

Moltin APIs

Moltin APIs are all asynchronous HTTP calls with very lightweight wrappers for JavaScript, Python, and many other languages. I am using it with node.js and the main pattern is fairly straightforward (look for js examples).

I am writing a batch import to create a playground product catalog so I find myself doing a lot of this:

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const inventory = Promise.all(goGetTheData()); 

inventory.then((data) => {
return Promise.all(data.products.map(product => {
return new Promise((resolve, reject) => {
moltin.Authenticate(function() {
moltin.Product.Create({
// .. product attributes
}, (result) => {
resolve(result);
}, (error, details) => {
reject(details);
});
});
});
}));
}).then((products) => {
return Promise.all(products.map(p => {
return new Promise((resolve, reject) => {
moltin.Authenticate(function() {
// ...
});
});
}));
}).then((modifiers) => {
// ... you got the idea, a lot of noise
});

I wish I could instead write:

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inventory.then((data) => Promise.all(data.products.map(p => {
return moltin.Product.Create(...);
}))).then((products) => Promise.all(products.map(p => {
return moltin.Modifier.Create(...);
}))).then((modifiers) => {
// ... a lot cleaner and more readable, isn't it?
});

Promisification

There’s moltin-util on NPM that uses Promises but it seems to introduce a new API and I would like to retain the original. Here’s what I quickly put together and I now wonder if it’s worth posting to NPM. Is it? Let me know!

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const request = require('request');
const fs = require('fs');

const promisify = (moltin) => {
const promisified = {}

const executor = (actor, action) => function () {
const args = [...arguments];

let success = (result, pagination) => {
if (result && pagination) {
result.pagination = pagination;
}

return result;
};

let error = (error, details) => details;

if (typeof (args[args.length - 1]) === 'function') {
if (typeof (args[args.length - 2]) === 'function') {
error = args.pop();
success = args.pop();
} else {
success = args.pop();
}
}

return new Promise((resolve, reject) => {
moltin.Authenticate(function () {
actor[action].call(actor, ...args,
(result, pagination) => {
resolve(success.call(null, result, pagination));
},
(err, details) => {
console.error(details);
reject(error.call(null, details));
});
});
});
};

Object.keys(moltin)
.filter(key => key !== 'options' && typeof (moltin[key]) === 'object')
.forEach(member => {
promisified[member] = {};
let actor = moltin[member];

Object.keys(actor.__proto__)
.concat(Object.keys(actor.__proto__.__proto__))
.filter(action => typeof (actor[action]) === 'function')
.forEach(action => {
promisified[member][action] = executor(actor, action);
});
});

return promisified;
}

module.exports = function (moltin) {
return promisify(moltin);
};

My code is now a whole lot cleaner and smaller too. I will soon post it on Github so stay tuned! Here is, for example, how I would go about deleting a whole bunch of products:

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const moltin = require('moltin')({
publicId: process.env.MOLTIN_PUBLIC_ID,
secretKey: process.env.MOLTIN_SECRET_KEY
});
const moltin_p = require('./promisify-moltin')(moltin);

moltin_p.Product.List(null)
.then((products) => Promise.all(products.map(p => {
console.log('Requesting a delete of %s', p.title);
return moltin_p.Product.Delete(p.id);
})))
.then((result) => {
console.log('Deleted %s products', result.length);
})
.catch((error) => {
console.error(error);
});