namespace formgen.input
{
	
	/**
	 */
	type type_item_raw = {
		input : interface_input<unknown>;
		kind ?: string;
		label ?: string;
	}

	
	/**
	 */
	type type_item = {
		input : interface_input<unknown>;
		kind : string;
		label : string;
	}

	
	/**
	 * @todo do not allow empty?
	 */
	export class class_input_sum implements interface_input<(null | {kind : string; value : unknown;})>
	{
		
		/**
		 */
		private items : Array<type_item>;


		/**
		 */
		private label : (null | string);
		
		
		/**
		 */
		private active : (null | string);


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

		/**
		 */
		public constructor(
			items : Array<type_item_raw>,
			{
				"label": label = null,
			}
			:
			{
				label ?: (null | string);
			}
			=
			{
			}
		)
		{
			this.items = (
				items
				.map(
					(item_raw, index) => ({
						"input": item_raw.input,
						"kind": (item_raw.kind ?? ("" + (index + 1).toFixed(0))),
						"label": (item_raw.label ?? ("Art " + (index + 1).toFixed(0))),
					})
				)
			);
			this.label = label;
			this.active = null;
			this.kind_to_index_map = new Map<string, int>();
			for (const index of formgen.helpers.list.sequence(this.items.length))
			{
				this.kind_to_index_map.set(this.items[index].kind, index);
			}
		}


		/**
		 * [implementation]
		 */
		public async setup(
			element_target : Element
		) : Promise<void>
		{
			let element_selection : Element;
			let element_item_inputs : Element;
			// structure
			{
				const element_container : Element = document.createElement("div");
				element_container.classList.add("formgen-input");
				element_container.classList.add("formgen-input-sum");
				// label
				{
					if (this.label === null)
					{
						// do nothing
					}
					else
					{
						const element_label : Element = document.createElement("label");
						element_label.textContent = this.label;
						element_container.appendChild(element_label);
					}
				}
				// selection
				{
					const radio_name : string = formgen.helpers.string.generate({"prefix": "formgen-input-sum-selection-"});
					element_selection = document.createElement("div");
					element_selection.classList.add("formgen-input-sum-selection");
					for (const item of this.items)
					{
						const input_id : string = formgen.helpers.string.generate({"prefix": "input-label-pair-"});
						const element_selector : Element = document.createElement("div");
						element_selector.setAttribute("rel", item.kind);
						element_selector.classList.add("formgen-input-sum-item-selector");
						// input
						{
							const element_selector_input : Element = document.createElement("input");
							element_selector_input.setAttribute("type", "radio");
							element_selector_input.setAttribute("name", radio_name);
							element_selector_input.setAttribute("id", input_id);
							element_selector.appendChild(element_selector_input);
						}
						// label
						{
							const element_selector_label : Element = document.createElement("label");
							element_selector_label.setAttribute("for", input_id);
							element_selector_label.textContent = item.label;
							element_selector.appendChild(element_selector_label);
						}
						element_selection.appendChild(element_selector);
					}
					element_container.appendChild(element_selection);
				}
				// inputs
				{
					element_item_inputs = document.createElement("div");
					element_item_inputs.classList.add("formgen-input-sum-inputs");
					for (const item of this.items)
					{
						const element_item_input : Element = document.createElement("div");
						element_item_input.classList.add("formgen-input-sum-item-input");
						element_item_input.setAttribute("rel", item.kind);
						await item.input.setup(element_item_input);
						element_item_inputs.appendChild(element_item_input);
					}
					element_container.appendChild(element_item_inputs);
				}
				element_target.appendChild(element_container);
			}
			// logic
			{
				element_selection.childNodes.forEach(
					(element) => {
						element.addEventListener(
							"change",
							(event) => {
								if (event.target === null)
								{
									// do nothing
								}
								else
								{
									const parent : (null | Element) = (event.target as Element).parentElement;
									if (parent === null)
									{
										// do nothing
									}
									else
									{
										const kind : (null | string) = parent.getAttribute("rel");
										if (kind === null)
										{
											// do nothing
										}
										else
										{
											const item : type_item = this.items[this.kind_to_index_map.get(kind)];
											this.active = kind;
											element_item_inputs.childNodes.forEach(
												(node) => {
													const element_input = (node as Element);
													element_input.classList.toggle(
														"formgen-input-sum-item-input-active",
														(element_input.getAttribute("rel") === kind)
													);
												}
											);
										}
									}
								}
							}
						);
					}
				);
			}
		}

		
		/**
		 * [implementation]
		 */
		public async read(
		) : Promise<(null | {kind : string; value : unknown;})>
		{
			if (this.active === null)
			{
				// throw (new Error("nothing active"));
				return null;
			}
			else
			{
				const item : type_item = this.items[this.kind_to_index_map.get(this.active)];
				return {
					"kind": item.kind,
					"value": (await item.input.read()),
				};
			}
		}

		
		/**
		 * [implementation]
		 */
		public async write(
			value : (null | {kind : string; value : unknown;})
		) : Promise<void>
		{
			throw (new Error("not implemented"));
		}

	}

}