Index: frontend/node_modules/tryer/README.md
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+# tryer
+
+[![Build status](https://gitlab.com/philbooth/tryer/badges/master/pipeline.svg)](https://gitlab.com/philbooth/tryer/pipelines)
+[![Package status](https://img.shields.io/npm/v/tryer.svg)](https://www.npmjs.com/package/tryer)
+[![Downloads](https://img.shields.io/npm/dm/tryer.svg)](https://www.npmjs.com/package/tryer)
+[![License](https://img.shields.io/npm/l/tryer.svg)](https://opensource.org/licenses/MIT)
+
+
+Because everyone loves a tryer!
+Conditional
+and repeated
+function invocation
+for node
+and browser.
+
+* [Say what?](#say-what)
+* [What size is it?](#what-size-is-it)
+* [How do I install it?](#how-do-i-install-it)
+* [How do I use it?](#how-do-i-use-it)
+  * [Loading the library](#loading-the-library)
+  * [Calling the exported function](#calling-the-exported-function)
+  * [Examples](#examples)
+* [How do I set up the dev environment?](#how-do-i-set-up-the-dev-environment)
+* [What license is it released under?](#what-license-is-it-released-under)
+
+## Say what?
+
+Sometimes,
+you want to defer
+calling a function
+until a certain
+pre-requisite condition is met.
+Other times,
+you want to
+call a function
+repeatedly
+until some post-requisite condition
+is satisfied.
+Occasionally,
+you might even want
+to do both
+for the same function.
+
+To save you writing
+explicit conditions
+and loops
+on each of those occasions,
+`tryer` implements
+a predicate-based approach
+that hides the cruft
+behind a simple,
+functional interface.
+
+Additionally,
+it allows you to easily specify
+retry intervals
+and limits,
+so that your code
+doesn't hog the CPU.
+It also supports
+exponential backoff
+of retry intervals,
+which can be useful
+when handling
+indefinite error states
+such as network failure.
+
+## What size is it?
+
+5.6 kb unminified with comments, 1.1 kb minified, 0.5 kb minified + gzipped.
+
+## How do I install it?
+
+Via npm:
+
+```
+npm i tryer --save
+```
+
+Or if you just want the git repo:
+
+```
+git clone git@gitlab.com:philbooth/tryer.git
+```
+
+## How do I use it?
+
+### Loading the library
+
+If you are running in
+Node.js
+or another CommonJS-style
+environment,
+you can `require`
+tryer like so:
+
+```javascript
+const tryer = require('tryer');
+```
+
+It also the supports
+the AMD-style format
+preferred by Require.js.
+
+If you are
+including `tryer`
+with an HTML `<script>` tag,
+or neither of the above environments
+are detected,
+it will be exported globally as `tryer`.
+
+### Calling the exported function
+
+`tryer` is a function
+that can be invoked to
+call other functions
+conditionally and repeatedly,
+without the need for
+explicit `if` statements
+or loops in your own code.
+
+`tryer` takes one argument,
+an options object
+that supports
+the following properties:
+
+* `action`:
+  The function that you want to invoke.
+  If `action` returns a promise,
+  iterations will not end
+  until the promise is resolved or rejected.
+  Alternatively,
+  `action` may take a callback argument, `done`,
+  to signal that it is asynchronous.
+  In that case,
+  you are responsible
+  for calling `done`
+  when the action is finished.
+  If `action` is not set,
+  it defaults to an empty function.
+
+* `when`:
+  A predicate
+  that tests the pre-condition
+  for invoking `action`.
+  Until `when` returns true
+  (or a truthy value),
+  `action` will not be called.
+  Defaults to
+  a function that immediately returns `true`.
+
+* `until`:
+  A predicate
+  that tests the post-condition
+  for invoking `action`.
+  After `until` returns true
+  (or a truthy value),
+  `action` will no longer be called.
+  Defaults to
+  a function that immediately returns `true`.
+
+* `fail`:
+  The error handler.
+  A function
+  that will be called
+  if `limit` falsey values
+  are returned by `when` or `until`.
+  Defaults to an empty function.
+
+* `pass`:
+  Success handler.
+  A function
+  that will be called
+  after `until` has returned truthily.
+  Defaults to an empty function.
+
+* `limit`:
+  Failure limit,
+  representing the maximum number
+  of falsey returns from `when` or `until`
+  that will be permitted
+  before invocation is deemed to have failed.
+  A negative number
+  indicates that the attempt
+  should never fail,
+  instead continuing 
+  for as long as `when` and `until`
+  have returned truthy values.
+  Defaults to `-1`.
+
+* `interval`:
+  The retry interval,
+  in milliseconds.
+  A negative number indicates
+  that each subsequent retry
+  should wait for twice the interval
+  from the preceding iteration
+  (i.e. exponential backoff).
+  The default value is `-1000`,
+  signifying that
+  the initial retry interval
+  should be one second
+  and that each subsequent attempt
+  should wait for double the length
+  of the previous interval.
+
+### Examples
+
+```javascript
+// Attempt to insert a database record, waiting until `db.isConnected`
+// before doing so. The retry interval is 1 second on each iteration
+// and the call will fail after 10 attempts.
+tryer({
+  action: () => db.insert(record),
+  when: () => db.isConnected,
+  interval: 1000,
+  limit: 10,
+  fail () {
+    log.error('No database connection, terminating.');
+    process.exit(1);
+  }
+});
+```
+
+```javascript
+// Attempt to send an email message, optionally retrying with
+// exponential backoff starting at 1 second. Continue to make
+// attempts indefinitely until the call succeeds.
+let sent = false;
+tryer({
+  action (done) {
+    smtp.send(email, error => {
+      if (! error) {
+        sent = true;
+      }
+      done();
+    });
+  },
+  until: () => sent,
+  interval: -1000,
+  limit: -1
+});
+```
+
+```javascript
+// Poll a device at 30-second intervals, continuing indefinitely.
+tryer({
+  action: () => device.poll().then(response => handle(response)),
+  interval: 30000,
+  limit: -1
+});
+```
+
+## How do I set up the dev environment?
+
+The dev environment relies on
+[Chai],
+[JSHint],
+[Mocha],
+[please-release-me],
+[spooks.js] and
+[UglifyJS].
+The source code is in
+`src/tryer.js`
+and the unit tests are in
+`test/unit.js`.
+
+To install the dependencies:
+
+```
+npm i
+```
+
+To run the tests:
+
+```
+npm t
+```
+
+To lint the code:
+
+```
+npm run lint
+```
+
+To regenerate the minified lib:
+
+```
+npm run minify
+```
+
+## What license is it released under?
+
+[MIT](COPYING)
+
+[chai]: http://chaijs.com/
+[jshint]: http://jshint.com/
+[mocha]: http://mochajs.org/
+[please-release-me]: https://gitlab.com/philbooth/please-release-me
+[spooks.js]: https://gitlab.com/philbooth/spooks.js
+[uglifyjs]: http://lisperator.net/uglifyjs/
+[license]: COPYING
+