807dd273fd
the reminder not showing content on the card at dashboard view and the quizes are hardcoded must move to the db make api's for it
142 lines
3.8 KiB
Markdown
142 lines
3.8 KiB
Markdown
# delayed-stream
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Buffers events from a stream until you are ready to handle them.
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## Installation
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``` bash
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npm install delayed-stream
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```
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## Usage
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The following example shows how to write a http echo server that delays its
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response by 1000 ms.
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``` javascript
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var DelayedStream = require('delayed-stream');
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var http = require('http');
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http.createServer(function(req, res) {
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var delayed = DelayedStream.create(req);
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setTimeout(function() {
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res.writeHead(200);
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delayed.pipe(res);
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}, 1000);
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});
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```
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If you are not using `Stream#pipe`, you can also manually release the buffered
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events by calling `delayedStream.resume()`:
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``` javascript
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var delayed = DelayedStream.create(req);
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setTimeout(function() {
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// Emit all buffered events and resume underlaying source
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delayed.resume();
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}, 1000);
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```
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## Implementation
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In order to use this meta stream properly, here are a few things you should
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know about the implementation.
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### Event Buffering / Proxying
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All events of the `source` stream are hijacked by overwriting the `source.emit`
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method. Until node implements a catch-all event listener, this is the only way.
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However, delayed-stream still continues to emit all events it captures on the
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`source`, regardless of whether you have released the delayed stream yet or
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not.
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Upon creation, delayed-stream captures all `source` events and stores them in
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an internal event buffer. Once `delayedStream.release()` is called, all
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buffered events are emitted on the `delayedStream`, and the event buffer is
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cleared. After that, delayed-stream merely acts as a proxy for the underlaying
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source.
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### Error handling
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Error events on `source` are buffered / proxied just like any other events.
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However, `delayedStream.create` attaches a no-op `'error'` listener to the
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`source`. This way you only have to handle errors on the `delayedStream`
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object, rather than in two places.
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### Buffer limits
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delayed-stream provides a `maxDataSize` property that can be used to limit
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the amount of data being buffered. In order to protect you from bad `source`
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streams that don't react to `source.pause()`, this feature is enabled by
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default.
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## API
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### DelayedStream.create(source, [options])
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Returns a new `delayedStream`. Available options are:
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* `pauseStream`
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* `maxDataSize`
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The description for those properties can be found below.
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### delayedStream.source
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The `source` stream managed by this object. This is useful if you are
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passing your `delayedStream` around, and you still want to access properties
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on the `source` object.
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### delayedStream.pauseStream = true
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Whether to pause the underlaying `source` when calling
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`DelayedStream.create()`. Modifying this property afterwards has no effect.
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### delayedStream.maxDataSize = 1024 * 1024
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The amount of data to buffer before emitting an `error`.
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If the underlaying source is emitting `Buffer` objects, the `maxDataSize`
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refers to bytes.
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If the underlaying source is emitting JavaScript strings, the size refers to
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characters.
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If you know what you are doing, you can set this property to `Infinity` to
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disable this feature. You can also modify this property during runtime.
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### delayedStream.dataSize = 0
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The amount of data buffered so far.
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### delayedStream.readable
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An ECMA5 getter that returns the value of `source.readable`.
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### delayedStream.resume()
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If the `delayedStream` has not been released so far, `delayedStream.release()`
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is called.
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In either case, `source.resume()` is called.
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### delayedStream.pause()
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Calls `source.pause()`.
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### delayedStream.pipe(dest)
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Calls `delayedStream.resume()` and then proxies the arguments to `source.pipe`.
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### delayedStream.release()
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Emits and clears all events that have been buffered up so far. This does not
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resume the underlaying source, use `delayedStream.resume()` instead.
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## License
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delayed-stream is licensed under the MIT license.
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