/*---------------------------------------------------------------------------------------------
 *  Copyright (c) Microsoft Corporation. All rights reserved.
 *  Licensed under the MIT License. See License.txt in the project root for license information.
 *--------------------------------------------------------------------------------------------*/

import { ResourceMap } from 'vs/base/common/map';
import { NotebookEditorWidget } from 'vs/workbench/contrib/notebook/browser/notebookEditorWidget';
import { DisposableStore, IDisposable } from 'vs/base/common/lifecycle';
import { IEditorGroupsService, IEditorGroup, GroupChangeKind, OpenEditorContext } from 'vs/workbench/services/editor/common/editorGroupsService';
import { IInstantiationService, createDecorator, ServicesAccessor } from 'vs/platform/instantiation/common/instantiation';
import { NotebookEditorInput } from 'vs/workbench/contrib/notebook/browser/notebookEditorInput';
import { registerSingleton } from 'vs/platform/instantiation/common/extensions';
import { IEditorService } from 'vs/workbench/services/editor/common/editorService';

export const INotebookEditorWidgetService = createDecorator<INotebookEditorWidgetService>('INotebookEditorWidgetService');

export interface IBorrowValue<T> {
	readonly value: T | undefined;
}

export interface INotebookEditorWidgetService {
	_serviceBrand: undefined;
	retrieveWidget(accessor: ServicesAccessor, group: IEditorGroup, input: NotebookEditorInput): IBorrowValue<NotebookEditorWidget>;
}

class NotebookEditorWidgetService implements INotebookEditorWidgetService {

	readonly _serviceBrand: undefined;

	private _tokenPool = 1;

	private readonly _notebookWidgets = new Map<number, ResourceMap<{ widget: NotebookEditorWidget, token: number | undefined }>>();
	private readonly _disposables = new DisposableStore();

	constructor(
		@IEditorGroupsService editorGroupService: IEditorGroupsService,
		@IEditorService editorService: IEditorService,
	) {

		const groupListener = new Map<number, IDisposable>();
		const onNewGroup = (group: IEditorGroup) => {
			const { id } = group;
			const listener = group.onDidGroupChange(e => {
				const widgets = this._notebookWidgets.get(group.id);
				if (!widgets || e.kind !== GroupChangeKind.EDITOR_CLOSE || !(e.editor instanceof NotebookEditorInput)) {
					return;
				}
				const value = widgets.get(e.editor.resource);
				if (!value) {
					return;
				}
				value.token = undefined;
				this._disposeWidget(value.widget);
				widgets.delete(e.editor.resource);
			});
			groupListener.set(id, listener);
		};
		this._disposables.add(editorGroupService.onDidAddGroup(onNewGroup));
		editorGroupService.groups.forEach(onNewGroup);

		// group removed -> clean up listeners, clean up widgets
		this._disposables.add(editorGroupService.onDidRemoveGroup(group => {
			const listener = groupListener.get(group.id);
			if (listener) {
				listener.dispose();
				groupListener.delete(group.id);
			}
			const widgets = this._notebookWidgets.get(group.id);
			this._notebookWidgets.delete(group.id);
			if (widgets) {
				for (let value of widgets.values()) {
					value.token = undefined;
					this._disposeWidget(value.widget);
				}
			}
		}));

		// HACK
		// we use the open override to spy on tab movements because that's the only
		// way to do that...
		this._disposables.add(editorService.overrideOpenEditor({
			open: (input, _options, group, context) => {
				if (input instanceof NotebookEditorInput && context === OpenEditorContext.MOVE_EDITOR) {
					// when moving a notebook editor we release it from its current tab and we
					// "place" it into its future slot so that the editor can pick it up from there
					this._freeWidget(input, editorGroupService.activeGroup, group);
				}
				return undefined;
			}
		}));
	}

	private _disposeWidget(widget: NotebookEditorWidget): void {
		widget.onWillHide();
		widget.getDomNode().remove();
		widget.dispose();
	}

	private _freeWidget(input: NotebookEditorInput, source: IEditorGroup, target: IEditorGroup): void {
		const targetWidget = this._notebookWidgets.get(target.id)?.get(input.resource);
		if (targetWidget) {
			// not needed
			return;
		}

		const widget = this._notebookWidgets.get(source.id)?.get(input.resource);
		if (!widget) {
			throw new Error('no widget at source group');
		}
		this._notebookWidgets.get(source.id)?.delete(input.resource);
		widget.token = undefined;

		let targetMap = this._notebookWidgets.get(target.id);
		if (!targetMap) {
			targetMap = new ResourceMap();
			this._notebookWidgets.set(target.id, targetMap);
		}
		targetMap.set(input.resource, widget);
	}

	retrieveWidget(accessor: ServicesAccessor, group: IEditorGroup, input: NotebookEditorInput): IBorrowValue<NotebookEditorWidget> {

		let value = this._notebookWidgets.get(group.id)?.get(input.resource);

		if (!value) {
			// NEW widget
			const instantiationService = accessor.get(IInstantiationService);
			const widget = instantiationService.createInstance(NotebookEditorWidget);
			widget.createEditor();
			const token = this._tokenPool++;
			value = { widget, token };

			let map = this._notebookWidgets.get(group.id);
			if (!map) {
				map = new ResourceMap();
				this._notebookWidgets.set(group.id, map);
			}
			map.set(input.resource, value);

		} else {
			// reuse a widget which was either free'ed before or which
			// is simply being reused...
			value.token = this._tokenPool++;
		}

		return this._createBorrowValue(value.token!, value);
	}

	private _createBorrowValue(myToken: number, widget: { widget: NotebookEditorWidget, token: number | undefined }): IBorrowValue<NotebookEditorWidget> {
		return {
			get value() {
				return widget.token === myToken ? widget.widget : undefined;
			}
		};
	}
}

registerSingleton(INotebookEditorWidgetService, NotebookEditorWidgetService, true);