namespace formgen.input
{
	
	/**
	 */
	type type_option<type_value> = {
		value : type_value;
		label : string;
	};


	/**
	 */
	export class class_input_select<type_value> implements interface_input<type_value>
	{
		
		/**
		 */
		private additional_classes : Array<string>;
		
		
		/**
		 */
		private label : (null | string);
		
		
		/**
		 */
		private options : Array<type_option<type_value>>;


		/**
		 */
		private value_map : Map<string, int>;


		/**
		 */
		private element_select : (null | HTMLSelectElement);
		
		
		/**
		 */
		public constructor(
			options : Array<type_option<type_value>>,
			{
				"additional_classes": additional_classes = [],
				"label": label = null,
			}
			:
			{
				additional_classes ?: Array<string>,
				label ?: (null | string);
			}
			=
			{
			}
		)
		{
			this.options = options;
			this.additional_classes = ["formgen-input-select"].concat(additional_classes);
			this.label = label;
			this.value_map = new Map<string, int>();
			this.element_select = null;
		}
		
		
		/**
		 * [implementation]
		 */
		public setup(
			target : Element
		) : Promise<void>
		{
			const id : string = formgen.helpers.string.generate();

			const element_container : Element = document.createElement("div");
			element_container.classList.add("formgen-input");
			for (const class_ of this.additional_classes)
			{
				element_container.classList.add(class_);
			}
			// label
			{
				if (this.label === null)
				{
					// do nothing
				}
				else
				{
					const element_label : Element = document.createElement("label");
					element_label.setAttribute("for", id);
					element_label.textContent = this.label;
					element_container.appendChild(element_label);
				}
			}
			// input
			{
				const element_select : HTMLSelectElement = (document.createElement("select") as HTMLSelectElement);
				element_select.setAttribute("id", id);
				for (const index of formgen.helpers.list.sequence(this.options.length))
				{
					const option : type_option<type_value> = this.options[index];
					const virtual_value : string = formgen.helpers.string.generate();
					this.value_map.set(virtual_value, index);
					
					const element_option : Element = document.createElement("option");
					element_option.textContent = option.label;
					element_option.setAttribute("value", virtual_value);
					element_select.appendChild(element_option);
				}
				element_container.appendChild(element_select);
				this.element_select = element_select;
			}
			target.appendChild(element_container);
			return Promise.resolve<void>(undefined);
		}
		
		
		/**
		 * [implementation]
		 */
		public read(
		) : Promise<type_value>
		{
			if (this.element_select === null)
			{
				return Promise.reject(new Error("not properly initialized"));
			}
			else
			{
				const virtual_value : string = this.element_select.value;
				const value : type_value = this.options[this.value_map.get(virtual_value)].value;
				return Promise.resolve<type_value>(value);
			}
		}
		
		
		/**
		 * [implementation]
		 */
		public write(
			value : type_value
		) : Promise<void>
		{
			if (this.element_select === null)
			{
				return Promise.reject(new Error("not properly initialized"));
			}
			else
			{
				return Promise.reject(new Error("not implemented"));
			}
		}
		
	}

}