get-uri

get-uri
=======

$3

This high-level module accepts a URI string and returns a Readable stream
instance. There is built-in support for a variety of "protocols", and it's
easily extensible with more:

| Protocol | Description | Example
|:---------:|:-------------------------------:|:---------------------------------:
| data | [Data URIs][data] | data:text/plain;base64,SGVsbG8sIFdvcmxkIQ%3D%3D
| file | [File URIs][file] | file:///c:/windows/example.ini
| ftp | [FTP URIs][ftp] | ftp://ftp.kernel.org/pub/site/README
| http | [HTTP URIs][http] | http://www.example.com/path/to/name
| https | [HTTPS URIs][https] | https://www.example.com/path/to/name

Example
-------

To simply get a stream.Readable instance from a file: URI, try something like:

``ts
import { getUri } from 'get-uri';

// file: maps to a fs.ReadStream instance…
const stream = await getUri('file:///Users/nrajlich/wat.json');
stream.pipe(process.stdout);
`


Missing Endpoints
-----------------

When you pass in a URI in which the resource referenced does not exist on the
destination server, then a NotFoundError will be thrown. The code of the
error instance is set to "ENOTFOUND", so you can check for that value
to detect when a bad filename is requested:

`ts
try {
await getUri('http://example.com/resource.json');
} catch (err) {
if (err.code === 'ENOTFOUND') {
// bad file path requested
} else {
// something else bad happened...
throw err;
}
}
`


Cacheability
------------

When calling getUri() with the same URI multiple times, the get-uri module
supports sending an indicator that the remote resource has not been modified
since the last time it has been retrieved from that node process.

To do this, define a cache property on the "options object" argument
with the value set to the stream.Readable instance that was previously
returned. If the remote resource has not been changed since the last call for
that same URI, then a NotModifiedError instance will be thrown with its
code property set to "ENOTMODIFIED".

When the "ENOTMODIFIED" error occurs, then you can safely re-use the
results from the previous getUri() call for that same URI:

` js
// First time fetches for real
const stream = await getUri('http://example.com/resource.json');

try {
// … some time later, if you need to get this same URI again, pass in the
// previous stream.Readable instance as cache option to potentially
// have an "ENOTMODIFIED" error thrown:
await getUri('http://example.com/resource.json', { cache: stream });
} catch (err) {
if (err.code === 'ENOTMODIFIED') {
// source file has not been modified since last time it was requested,
// so you are expected to re-use results from a previous call to getUri()
} else {
// something else bad happened...
throw err;
}
}
`


API
---

$3

A uri is required. An optional options object may be passed in:

- cache - A stream.Readable instance from a previous call to getUri() with the same URI. If this option is passed in, and the destination endpoint has not been modified, then an ENOTMODIFIED error is thrown

Any other options passed in to the options object will be passed through
to the low-level connection creation functions (http.get(), ftp.connect(),
etc).

Returns a stream.Readable instance to read the resource at the given uri`.

[data]: http://tools.ietf.org/html/rfc2397
[file]: http://tools.ietf.org/html/draft-hoffman-file-uri-03
[ftp]: http://www.w3.org/Protocols/rfc959/
[http]: http://www.w3.org/Protocols/rfc2616/rfc2616.html
[https]: http://wikipedia.org/wiki/HTTP_Secure