Add an example how to attach persistent metadata to button events

clientlib/nodejs/persistent-metadata-example/README.md

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+# Persistent button metadata example
+
+This is an example how to attach persistent metadata to button events.
+
+## How it works
+
+On start the program fetches a lists of verified Flic buttons and adds a record for each button to a `buttons.json` file. The record can store any number of properties and metadata.
+
+When a button is clicked the metadata for that button is attached to the registered callback function.
+
+## Quick start
+
+1. Start the `flicd` deamon.
+1. Run `node index.js`
+1. Edit the created `buttons.json` file and add some metadata. 
+   ```
+   {
+     "80:e4:da:11:11:1d": {
+       "name": "Button One"
+     },
+     "80:e4:da:22:22:2d": {
+       "name": "Button Two"
+     }
+   }
+   ```
+1. Restart `node index.js`

clientlib/nodejs/persistent-metadata-example/flic.js

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+const flicLib = require('../fliclibNodeJs')
+const JSONStore = require('./jsonStore')
+
+const Flic = (opt) => {
+	const options = Object.assign({
+		dbFile: 'buttons.json',
+		defaultButtonProps: {
+			name: "UNNAMED"
+		}
+	}, opt)
+
+	const state = {
+		buttons: {},
+		eventListeners: {}
+	}
+
+	const client = new flicLib.FlicClient('localhost', 5551)
+
+	const db = JSONStore(options.dbFile)
+
+	const mergeButtons = (defaultButtonProps) => (buttons, buttonId) => {
+		buttons[buttonId] = Object.assign({}, defaultButtonProps, buttons[buttonId])
+		return buttons
+	}
+
+	const getNewAndOldButtons = (buttonIds, defaultButtonProps) => (storedButtons) => {
+		return buttonIds.reduce(mergeButtons(defaultButtonProps), storedButtons)
+	}
+
+	const updateState = (key) => (value) => {
+		state[key] = value
+		return value
+	}
+
+	const addEventListener = (buttonId) => {
+		const cc = new flicLib.FlicConnectionChannel(buttonId)
+		client.addConnectionChannel(cc)
+		cc.on('buttonSingleOrDoubleClickOrHold', (clickType, wasQueued, timeDiff) => {
+			if (state.eventListeners[clickType]) {
+				state.eventListeners[clickType].forEach((callback) => {
+					callback(clickType, wasQueued, timeDiff, state.buttons[buttonId])
+				})
+			}
+		})
+	}
+
+	const addEventListenerToButtons = () => {
+		Object.keys(state.buttons).forEach(addEventListener)
+	}
+
+	client.once('ready', () => {
+		client.getInfo(info => {
+			db.get()
+				.then(getNewAndOldButtons(info.bdAddrOfVerifiedButtons, options.defaultButtonProps))
+				.then(updateState('buttons'))
+				.then(db.save)
+				.then(addEventListenerToButtons)
+		})
+	})
+
+	const on = (type, callback) => {
+		if (!state.eventListeners[type]) {
+			state.eventListeners[type] = []
+		}
+		state.eventListeners[type].push(callback)
+	}
+
+	return {
+		on
+	}
+}
+
+module.exports = Flic

clientlib/nodejs/persistent-metadata-example/index.js

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+const flicConnector = require('./flic')
+
+const flic = flicConnector({
+	defaultButtonProps: {
+		name: "UNNAMED"
+	}
+})
+
+flic.on('ButtonSingleClick', (type, wasQueued, timeDiff, metadata) => {
+	console.log('Click detected on button with metadata', metadata)
+})
+
+flic.on('ButtonHold', (type, wasQueued, timediff, metadata) => {
+	console.log('Hold detected on button with metadata', metadata)
+})
+
+console.log('Listening for single click and button hold')
+

clientlib/nodejs/persistent-metadata-example/jsonStore.js

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+const fs = require('fs')
+
+const JSONStore = (filename) => {
+		const get = () => new Promise((resolve, reject) => {
+			try {
+				resolve(JSON.parse(fs.readFileSync(filename), 'utf8'))
+			} catch (e) {
+				if (e.code === 'ENOENT') {
+					resolve({})
+				} else {
+					reject(e)
+				}
+			}
+		})
+
+		const save = (data) => new Promise((resolve, reject) => {
+			try {
+				fs.writeFileSync(filename, JSON.stringify(data, null, 4), 'utf8')
+				resolve()
+			} catch (e) {
+				reject(e)
+			}
+		})
+
+    return {
+      get,
+      save
+    }
+}
+
+module.exports = JSONStore