Air-Quality-Web/client_src/js/LayerHeatmap.mjs

"use strict";

import HeatmapOverlay from 'leaflet-heatmap';

import Config from './Config.mjs';
import GetFromUrl from './Helpers/GetFromUrl.mjs';


class LayerHeatmap {
	/**
	 * Creates a new heatmap manager wrapper class fort he given map.
	 * @param	{L.Map}	in_map	The leaflet map to attach to.
	 */
	constructor(in_map) {
		this.map = in_map;
		
		this.overlay_config = {
			radius: Config.heatmap.blob_radius,
			minOpacity: 0.5,
			maxOpacity: 0.8,
			scaleRadius: true,
			useLocalExtrema: false,
			
			latField: "latitude",
			lngField: "longitude",
			valueField: "value",
			
			gradient: {
				// 0 to 35 low (green), 36 to 53 moderate (amber) 54 to 70 high (red) and above 71 (purple)
				0.233: "green",
				0.593: "orange",
				0.827: "red",
				1: "purple"
			}
		};
		this.layer = new L.LayerGroup();
		this.map.addLayer(this.layer);
		this.recreate_overlay();
		
		// Custom configuration directives to apply based on the reading type displayed.
		this.reading_type_configs = {
			"PM25": {
				// 0 to 35 low (green), 36 to 53 moderate (amber) 54 to 70 high (red) and above 71 (purple)
				max: 75,
				gradient: {
					"0": "hsla(111, 76%, 42%, 0.00)",
					"0.233": "hsl(111, 76%, 42%)", // green
					"0.593": "orange",
					"0.827": "red",
					"1": "purple"
				}
			},
			"PM10": {
				// 0 to 50 low (green) 51 to75 moderate (amber) 76 to 100 high (red) and more than 100 very high (purple)
				max: 100,
				gradient: {
					"0": "hsla(111, 76%, 42%, 0)",
					"0.45": "hsl(111, 76%, 42%)", // green
					"0.573": "orange",
					"0.8": "red",
					"1": "purple"
				}
			},
			"humidity": {
				max: 100,
				gradient: {
					"0": "hsla(176, 77%, 40%, 0)",
					"0.5": "hsl(176, 77%, 40%)",
					"1": "blue"
				}
			},
			"temperature": {
				max: 40,
				gradient: {
					"-0.25": "blue",
					"0.25": "cyan",
					"0.375": "green",
					"0.5": "yellow",
					"0.75": "orange",
					"1": "red"
				}
			}
		};
		
		this.reading_cache = new Map();
	}
	
	/**
	 * Re-creates the heatmap overlay layer.
	 * Needed sometimes internally to work around an annoying bug.
	 */
	recreate_overlay() {
		if(typeof this.heatmap != "undefined")
			this.layer.removeLayer(this.heatmap);
		this.heatmap = new HeatmapOverlay(this.overlay_config);
		this.layer.addLayer(this.heatmap);
	}
	
	/**
	 * Sets the display data to the given array of data points.
	 * @param {object[]} readings_list The array of data points to display.
	 */
	set_data(readings_list) {
		let data_object = {
			max: 0,
			data: readings_list
		};
		
		if(typeof this.reading_type_configs[this.reading_type] != "undefined")
			data_object.max = this.reading_type_configs[this.reading_type].max;
		else
			data_object.max = readings_list.reduce((prev, next) => next.value > prev ? next.value : prev, 0);
		
		console.log("[map/heatmap] Displaying", this.reading_type, data_object);
		
		this.heatmap.setData(data_object);
	}
	
	/**
	 * Updates the heatmap with data for the specified datetime & reading type,
	 * fetching new data if necessary.
	 * @param	{Date}		datetime		The datetime to display.
	 * @param	{string}	reading_type	The reading type to display data for.
	 * @return	{Promise}	A promise that resolves when the operation is completed.
	 */
	async update_data(datetime, reading_type) {
		if(!(datetime instanceof Date))
			throw new Exception("Error: 'datetime' must be an instance of Date.");
		if(typeof reading_type != "string")
			throw new Exception("Error: 'reading_type' must be a string.");
		
		this.datetime = datetime;
		this.reading_type = reading_type;
		
		console.log("[map/heatmap] Updating values to", this.reading_type, "@", this.datetime);
		
		if(typeof this.reading_type_configs[this.reading_type] != "undefined") {
			this.overlay_config.gradient = this.reading_type_configs[this.reading_type].gradient;
			console.log("[map/heatmap] Gradient is now", this.overlay_config.gradient);
			this.recreate_overlay();
		}
		else {
			delete this.overlay_config.gradient;
		}
		
		try {
			this.set_data(await this.fetch_data(this.datetime, this.reading_type));
		} catch(error) {
			console.log(error);
			alert(error);
		}
	}
	
	/**
	 * Fetches & decodes data for the given datetime and the current reading type.
	 * @param	{Date}		datetime		The Date to fetch data for.
	 * @param	{string}	reading_type	The reading type code to fetch data for.
	 * @return	{Promise}	The requested data array, as the return value of a promise
	 */
	async fetch_data(datetime, reading_type) {
		let cache_key = `${reading_type}|${datetime.toISOString()}`;
		let result = this.reading_cache.get(cache_key);
		
		if(typeof result == "undefined") {
			result = JSON.parse(await GetFromUrl(
				`${Config.api_root}?action=fetch-data&datetime=${encodeURIComponent(datetime.toISOString())}&reading_type=${encodeURIComponent(reading_type)}`
			));
			this.prune_cache(100);
			this.reading_cache.set(cache_key, { data: result, inserted: new Date() });
		}
		else
			result = result.data;
		
		return result;
	}
	
	/**
	 * Prunes the reading cache, leaving at most newest_count items behind.
	 * The items inserted first are deleted first.
	 * @param  {Number} newest_count The numebr of items to leave behind in the cache.
	 * @returns {Number}	The number of items deleted from the cache.
	 */
	prune_cache(newest_count) {
		let items = [];
		for(let next_key of this.reading_cache) {
			let cache_item = this.reading_cache.get(next_key);
			if(typeof cache_item == "undefined") {
				this.reading_cache.delete(cache_item);
				continue;
			}
			items.push({
				key: next_key,
				date: cache_item.inserted
			});
		}
		items.sort((a, b) => a.date - b.date);
		let deleted = 0;
		for(let i = 0; i < items.length - newest_count; i++) {
			this.reading_cache.delete(this.items[i].key);
			deleted++;
		}
		return deleted;
	}
	
	/**
	 * Whether the reading cache contains data for the given datetime & reading type.
	 * @param	{Date}		datetime		The datetime to check.
	 * @param	{string}	reading_type	The reading type code to check.
	 * @return	{Boolean}	Whether the reading cache contains data for the requested datetime & reading type.
	 */
	is_data_cached(datetime, reading_type) {
		let cache_key = Symbol.for(`${reading_type}|${datetime.toISOString()}`);
		return this.reading_cache.has(cache_key);
	}
	
	
	async update_reading_type(reading_type) {
		await this.update_data(
			this.datetime,
			reading_type
		);
	}
}

export default LayerHeatmap;