smcloudstore-localstorage

This package is a provider for SMCloudStore, for local storage hosting. SMCloudStore is a lightweight Node.js module that offers a simple API to interact with the object storage services of multiple cloud providers.

Please refer to the main package for the SMCloudStore documentation and instructions on how to use it.

Provider-specific considerations

There are a few provider-specific considerations for the LocalStorage provider.

Connection argument

When initializing the LocalStorage provider, the options argument is an object with:

• options.signingFn: function(method, path, ttl) returning a String (which can be promised) which returns a publically accessible URL to download/upload from/to the specified path. It should also only last for ttl seconds. (generateRandUid() is exposed to help generate random URL IDs.)
• options.basePath (optional): string representing the base path to store files in(default: ${__dirname}/storage)

Example:

// Require the package
const SMCloudStore = require('smcloudstore')

// Complete with the connection options for LocalStorage
const options = {
    signingFn: (method, path, ttl) => console.log("store the method/path/ttl combo in a DB for later use with a generic route"),
    basePath: __dirname + '/app/storage',
}

// Return an instance of the GenericS3Provider class
const storage = SMCloudStore.create('localstorage', options)

Using pre-signed URLs

In the storage.presignedPutUrl(container, path, [options], [ttl]) and equivalent get methods, the LocalStorage provider ignores the container and options argument, which have no effect.

What is returned, however, is a promise that is resolved using your signingFn function which should return a string (being the final URL). The design intent is to allow you to generate and store a link in your database with a reference to the file to get/put. This gives you full control over how you manage these links.

An example signingFn could be:

// Signing function
async function signingFn(method, path, ttl) {
    let token;
    let curUrl = await db.signedUrls.get(method, path);
    if(curUrl !== null) {
        token = curUrl.token;
        await db.signedUrls.update(method, path, token, Date.now() + (ttl * 1000));
    } else {
        token = storage.client.generateRandomUid();
        await db.signedUrls.put(method, path, token, Date.now() + (ttl * 1000));
    }
    return token;
}

// Usage in express
app.get('/download/:token', (req, res) => {
    let token = req.params.token;
    let url = await db.signedUrls.get(token);
    if(url !== null && url.expire > Date.now()) {
        if(url.method !== "get") return res.status(405).send("405 Method Not Allowed").end();
        return (await storage.getObject(null, url.path)).pipe(res);
    }
    else return res.status(404).send("404 Not Found").end();
});
// .. and do something similar for put

Accessing the LocalStorage library

The LocalStorage provider is built from the ground up and has a couple of additional helper functions, which are exposed by calling storage.client().

By accessing this object, you have access to:

• generateRandomUid(),
• sanitisePath(path)