/**
 * A DataLabel shows a value from an entity from a specific type of the DataManager.
 * Will always be up to date because it subscribes to updates by the DataManager.
 */
class DataLabel extends View {

	constructor(element) {
		super(element);

		this.type = element.getAttribute("data-type");
		this.primaryKey = element.getAttribute("data-primary-key");
		this.fieldName = element.getAttribute("data-value");
		this.useHtml = element.hasAttribute("data-html");
		this.nullText = element.getAttribute("data-null-text");
	}

	/**
	 * Sets the primary key value of the entity from which this label should display a specific value.
	 * Will display the null text if the key is null.
	 * @param key The primary key value of the entity to display.
	 */
	setKey(key) {
		if (key) {
			//Reset the label.
			this.displayValue("");

			if (!this.onDataUpdateBound) {
				this.onDataUpdateBound = this.onDataUpdate.bind(this);
			}
			else {
				//Remove the existing listener.
				TimeCards.dataManager.removeDataListener(this.type, this.onDataUpdateBound);
			}

			var filters = { };
			filters[this.primaryKey] = key;
			TimeCards.dataManager.addDataListener(this.type, filters, this.onDataUpdateBound);
		}
		else {
			this.displayValue(this.nullText);
		}
	}

	onDataUpdate(key, entity) {
		var value = this.nullText;
		if (entity && (this.fieldName in entity) && entity[this.fieldName] != null) {
			value = entity[this.fieldName];
		}

		this.displayValue(value);
	}

	displayValue(value) {
		if (this.useHtml) {
			this.element.innerHTML = value;
		}
		else {
			this.element.innerText = value;
		}
	}

}

UIKit.registerViewType(DataLabel);