appcd-detect

A engine for detecting and watching filesystem directories for things of interest.

The detect engine is not suitable for detecting individual files. It is intended for detecting if a specific directory is what you're looking for.

Visit https://github.com/appcelerator/appc-daemon for more information.

Report issues to GitHub issues. Official issue tracker in JIRA.

Installation

npm i appcd-detect

Usage

import DetectEngine from 'appcd-detect';

const engine = new DetectEngine({
	checkDir(dir) {
	 	if (dir === '/something/we/are/interested/in') {
			return {
				dir
			};
		}
	},
	depth:     1,
	multiple:  true,
	paths:     '/some/path/to/scan',
	redetect:  true,
	watch:     true
});

engine.on('results', results => {
	console.log(results);
});

const results = await engine.start();
console.log(results);

Windows Registry

On Windows machines, there may be times where the list of paths to scan is derived based on values in the Windows Registry or the search paths should be rescanned when activity occurs in the registry. The DetectEngine supports this via the registryCallback and registryKeys options.

registryCallback

A callback that is fired every refreshPathsInterval milliseconds when the watch option is set to true. By default, refreshPathsInterval is set to 30000 (30 seconds).

registryCallback is supplied a reference to the DetectEngine.

registryCallback must return either a falsey value, an object containing paths and defaultPath, or a Promise that resolves the aforementioned object.

paths may be a string, an array of strings, or falsey.

defaultPath must be a string or falsey. It is assumed the defaultPath is already in the list of paths.

new DetectEngine({
	checkDir(dir) {},
	async registryCallback(engine) {
		// do something
		return {
			paths: [ '/path/to/somewhere' ],
			defaultPath: '/path/to/somewhere' // or `undefined` to autoselect the first path
		};
	},
	watch: true
});

If the list of paths changes, then it triggers a rescan. If paths has not changed since last called, but defaultPath has changed, then only the cached results are processed again. If neither the paths or defaultPath has changed, then no action is taken.

registryKeys

This option contains an array of registry watch parameters.

new DetectEngine({
	checkDir(dir) {},
	registryKeys: [
		{
			key: 'HKLM\\SOFTWARE\\Android Studio',
			value: 'SdkPath'
		},
		{
			key: 'HKLM\\Software\\Microsoft\\Microsoft SDKs\\Windows'
			// depth (Number, defaults to 0)
			// filter (Object w/ `subkeys` and/or `values` filters)
			// transform() (Function)
			// value (String)
		}
	],
	watch: true
});

The registry watcher will watch the specified keys for changes such as the key itself being created, a new subkey, or a new value name. It also supports recursively watching key activity.

A key may specify the hive separate from the key, however the detect engine will just combine them.

If a value name is present, it will collect each value and add them to the list of search paths.

During the detect engine startup, the registry key watchers are initialized and each key is queried and its value added to the list of search paths.

Optionally, each key may contain a transform() callback which is invoked on the value. If the result is undefined, then the original value argument is used. transform() must return an object with a value property, but may also have additional properties such as an isDefault flag.

The depth specifies how many subkeys deep it should watch for changes. Defaults to zero.

The filter property is an object with values and/or subkeys containing a string or regex. Filtering only applies to the existence of subkeys and value "names", but not actual value "values" or the specified value's "value".

registryKeys Examples

{
	key: 'HKLM\\SOFTWARE\\Android Studio',
	value: 'SdkPath'
}

{
	callback(state, keyWatcher) {
		// `state.value` contains the registry key value

		// if needed, you can use `keyWatcher.winreglib.get()` to fetch additional info

		// optionally, you can set `state.isDefault` to help the detect engine prioritize results

		return state; // optional
	},
	key: 'HKLM\\SOFTWARE\\Android Studio',
	value: 'SdkPath'
}

Legal

This project is open source under the Apache Public License v2 and is developed by Axway, Inc and the community. Please read the LICENSE file included in this distribution for more information.