import { defaultFolderIcon, FolderEntity, FolderIcon, NoteEntity, ResourceEntity } from '../services/database/types';
import BaseModel, { DeleteOptions } from '../BaseModel';
import { FolderLoadOptions } from './utils/types';
import time from '../time';
import { _ } from '../locale';
import Note from './Note';
import Database from '../database';
import BaseItem from './BaseItem';
import Resource from './Resource';
import { isRootSharedFolder } from '../services/share/reducer';
import Logger from '@joplin/utils/Logger';
import syncDebugLog from '../services/synchronizer/syncDebugLog';
import ResourceService from '../services/ResourceService';
import { LoadOptions } from './utils/types';
import { getTrashFolder, getTrashFolderId } from '../services/trash';
const { substrWithEllipsis } = require('../string-utils.js');

const logger = Logger.create('models/Folder');

export interface FolderEntityWithChildren extends FolderEntity {
	children?: FolderEntity[];
}

export default class Folder extends BaseItem {
	public static tableName() {
		return 'folders';
	}

	public static modelType() {
		return BaseModel.TYPE_FOLDER;
	}

	public static newFolder(): FolderEntity {
		return {
			id: null,
			title: '',
		};
	}

	public static fieldToLabel(field: string) {
		const fieldsToLabels: any = {
			title: _('title'),
			last_note_user_updated_time: _('updated date'),
		};

		return field in fieldsToLabels ? fieldsToLabels[field] : field;
	}

	public static async notes(parentId: string, options: LoadOptions = null) {
		options = {
			includeConflicts: false,
			...options,
		};

		const where = ['parent_id = ?'];
		if (!options.includeConflicts) {
			where.push('is_conflict = 0');
		}

		if (!options.includeDeleted) {
			where.push('deleted_time = 0');
		}

		return this.modelSelectAll(`SELECT ${this.selectFields(options)} FROM notes WHERE ${where.join(' AND ')}`, [parentId]);
	}

	public static async noteIds(parentId: string, options: LoadOptions = null) {
		const notes = await this.notes(parentId, {
			fields: ['id'],
			...options,
		});
		return notes.map(n => n.id);
	}

	public static async subFolderIds(parentId: string) {
		const rows = await this.db().selectAll('SELECT id FROM folders WHERE parent_id = ?', [parentId]);
		return rows.map((r: FolderEntity) => r.id);
	}

	public static async noteCount(parentId: string) {
		const r = await this.db().selectOne('SELECT count(*) as total FROM notes WHERE is_conflict = 0 AND parent_id = ?', [parentId]);
		return r ? r.total : 0;
	}

	public static markNotesAsConflict(parentId: string) {
		const query = Database.updateQuery('notes', { is_conflict: 1 }, { parent_id: parentId });
		return this.db().exec(query);
	}

	public static byId(items: FolderEntity[], id: string) {
		if (id === getTrashFolderId()) return getTrashFolder();
		return super.byId(items, id);
	}

	public static async deleteAllByShareId(shareId: string, deleteOptions: DeleteOptions = null) {
		const tableNameToClasses: Record<string, any> = {
			'folders': Folder,
			'notes': Note,
			'resources': Resource,
		};

		for (const tableName of ['folders', 'notes', 'resources']) {
			const ItemClass = tableNameToClasses[tableName];
			const rows = await this.db().selectAll(`SELECT id FROM ${tableName} WHERE share_id = ?`, [shareId]);
			const ids: string[] = rows.map(r => r.id);
			await ItemClass.batchDelete(ids, deleteOptions);
		}
	}

	public static async delete(folderId: string, options: DeleteOptions = null) {
		options = {
			deleteChildren: true,
			...options,
		};

		if (folderId === getTrashFolderId()) throw new Error('The trash folder cannot be deleted');

		const toTrash = !!options.toTrash;

		const folder = await Folder.load(folderId);
		if (!folder) return; // noop

		if (options.deleteChildren) {
			const childrenDeleteOptions: DeleteOptions = {
				disableReadOnlyCheck: options.disableReadOnlyCheck,
				deleteChildren: true,
				toTrash,
			};

			const noteIds = await Folder.noteIds(folderId);
			await Note.batchDelete(noteIds, childrenDeleteOptions);

			const subFolderIds = await Folder.subFolderIds(folderId);
			for (let i = 0; i < subFolderIds.length; i++) {
				await Folder.delete(subFolderIds[i], childrenDeleteOptions);
			}
		}

		if (toTrash) {
			const newFolder: FolderEntity = { id: folderId, deleted_time: Date.now() };
			if ('toTrashParentId' in options) newFolder.parent_id = options.toTrashParentId;
			if (options.toTrashParentId === newFolder.id) throw new Error('Parent ID cannot be the same as ID');
			await this.save(newFolder);
		} else {
			await super.delete(folderId, options);
		}

		this.dispatch({
			type: 'FOLDER_DELETE',
			id: folderId,
		});
	}

	public static conflictFolderTitle() {
		return _('Conflicts');
	}

	public static conflictFolderId() {
		return 'c04f1c7c04f1c7c04f1c7c04f1c7c04f';
	}

	public static conflictFolder(): FolderEntity {
		const now = Date.now();

		return {
			type_: this.TYPE_FOLDER,
			id: this.conflictFolderId(),
			parent_id: '',
			title: this.conflictFolderTitle(),
			updated_time: now,
			user_updated_time: now,
			share_id: '',
			is_shared: 0,
		};
	}

	// Calculates note counts for all folders and adds the note_count attribute to each folder
	// Note: this only calculates the overall number of nodes for this folder and all its descendants
	public static async addNoteCounts(folders: FolderEntity[], includeCompletedTodos = true) {
		// This is old code so we keep it, but we should never ever add properties to objects from
		// the database. Eventually we should refactor this.
		interface FolderEntityWithNoteCount extends FolderEntity {
			note_count?: number;
		}

		const foldersById: Record<string, FolderEntityWithNoteCount> = {};
		for (const f of folders) {
			foldersById[f.id] = f;

			if (this.conflictFolderId() === f.id) {
				foldersById[f.id].note_count = await Note.conflictedCount();
			} else {
				foldersById[f.id].note_count = 0;
			}
		}

		const where = [
			'is_conflict = 0',
			'notes.deleted_time = 0',
		];
		if (!includeCompletedTodos) where.push('(notes.is_todo = 0 OR notes.todo_completed = 0)');

		const sql = `
			SELECT folders.id as folder_id, count(notes.parent_id) as note_count 
			FROM folders LEFT JOIN notes ON notes.parent_id = folders.id
			WHERE ${where.join(' AND ')}
			GROUP BY folders.id
		`;

		interface NoteCount {
			folder_id: string;
			note_count: number;
		}

		const noteCounts: NoteCount[] = await this.db().selectAll(sql);
		// eslint-disable-next-line github/array-foreach -- Old code before rule was applied
		noteCounts.forEach((noteCount) => {
			let parentId = noteCount.folder_id;
			do {
				const folder = foldersById[parentId];
				if (!folder) break; // https://github.com/laurent22/joplin/issues/2079
				folder.note_count = (folder.note_count || 0) + noteCount.note_count;

				// Should not happen anymore but just to be safe, add the check below
				// https://github.com/laurent22/joplin/issues/3334
				if (folder.id === folder.parent_id) break;

				parentId = folder.parent_id;
			} while (parentId);
		});
	}

	// Folders that contain notes that have been modified recently go on top.
	// The remaining folders, that don't contain any notes are sorted by their own user_updated_time
	public static async orderByLastModified(folders: FolderEntity[], dir = 'DESC') {
		dir = dir.toUpperCase();
		const sql = 'select parent_id, max(user_updated_time) content_updated_time from notes where parent_id != "" group by parent_id';
		const rows = await this.db().selectAll(sql);

		const folderIdToTime: Record<string, number> = {};
		for (let i = 0; i < rows.length; i++) {
			const row = rows[i];
			folderIdToTime[row.parent_id] = row.content_updated_time;
		}

		const findFolderParent = (folderId: string) => {
			const folder = BaseModel.byId(folders, folderId);
			if (!folder) return null; // For the rare case of notes that are associated with a no longer existing folder
			if (!folder.parent_id) return null;
			for (let i = 0; i < folders.length; i++) {
				if (folders[i].id === folder.parent_id) return folders[i];
			}

			// In some rare cases, some folders may not have a parent, for example
			// if it has not been downloaded via sync yet.
			// https://github.com/laurent22/joplin/issues/2088
			return null;
		};

		const applyChildTimeToParent = (folderId: string) => {
			const parent = findFolderParent(folderId);
			if (!parent) return;

			if (folderIdToTime[parent.id] && folderIdToTime[parent.id] >= folderIdToTime[folderId]) {
				// Don't change so that parent has the same time as the last updated child
			} else {
				folderIdToTime[parent.id] = folderIdToTime[folderId];
			}

			applyChildTimeToParent(parent.id);
		};

		for (const folderId in folderIdToTime) {
			if (!folderIdToTime.hasOwnProperty(folderId)) continue;
			applyChildTimeToParent(folderId);
		}

		const mod = dir === 'DESC' ? +1 : -1;
		const output = folders.slice();
		output.sort((a, b) => {
			const aTime = folderIdToTime[a.id] ? folderIdToTime[a.id] : a.user_updated_time;
			const bTime = folderIdToTime[b.id] ? folderIdToTime[b.id] : b.user_updated_time;

			if (aTime < bTime) return +1 * mod;
			if (aTime > bTime) return -1 * mod;

			return 0;
		});

		return output;
	}

	public static async all(options: FolderLoadOptions = null) {
		let output: FolderEntity[] = await super.all(options);

		if (options && options.includeDeleted === false) {
			output = output.filter(f => !f.deleted_time);
		}

		if (options && options.includeTrash) {
			output.push(getTrashFolder());
		}

		if (options && options.includeConflictFolder) {
			const conflictCount = await Note.conflictedCount();
			if (conflictCount) output.push(this.conflictFolder());
		}

		return output;
	}

	public static async childrenIds(folderId: string, options: LoadOptions = null) {
		options = { ...options };

		const where = ['parent_id = ?'];

		if (!options.includeDeleted) {
			where.push('deleted_time = 0');
		}

		const folders = await this.db().selectAll(`SELECT id FROM folders WHERE ${where.join(' AND ')}`, [folderId]);

		let output: string[] = [];

		for (let i = 0; i < folders.length; i++) {
			const f = folders[i];
			output.push(f.id);
			const subChildrenIds = await this.childrenIds(f.id, options);
			output = output.concat(subChildrenIds);
		}

		return output;
	}

	public static async expandTree(folders: FolderEntity[], parentId: string) {
		const folderPath = await this.folderPath(folders, parentId);
		folderPath.pop(); // We don't expand the leaft notebook

		for (const folder of folderPath) {
			this.dispatch({
				type: 'FOLDER_SET_COLLAPSED',
				id: folder.id,
				collapsed: false,
			});
		}
	}

	public static async allChildrenFolders(folderId: string): Promise<FolderEntity[]> {
		const sql = `
			WITH RECURSIVE
				folders_cte(id, parent_id, share_id) AS (
					SELECT id, parent_id, share_id
						FROM folders
						WHERE parent_id = ?
					UNION ALL
						SELECT folders.id, folders.parent_id, folders.share_id
							FROM folders
							INNER JOIN folders_cte AS folders_cte ON (folders.parent_id = folders_cte.id)
				)
				SELECT id, parent_id, share_id FROM folders_cte;
		`;

		return this.db().selectAll(sql, [folderId]);
	}

	public static async rootSharedFolders(): Promise<FolderEntity[]> {
		return this.db().selectAll('SELECT id, share_id FROM folders WHERE parent_id = "" AND share_id != ""');
	}

	public static async rootShareFoldersByKeyId(keyId: string): Promise<FolderEntity[]> {
		return this.db().selectAll('SELECT id, share_id FROM folders WHERE master_key_id = ?', [keyId]);
	}

	public static async updateFolderShareIds(): Promise<void> {
		// Get all the sub-folders of the shared folders, and set the share_id
		// property.
		const rootFolders = await this.rootSharedFolders();

		let sharedFolderIds: string[] = [];

		const report = {
			shareUpdateCount: 0,
			unshareUpdateCount: 0,
		};

		for (const rootFolder of rootFolders) {
			const children = await this.allChildrenFolders(rootFolder.id);

			report.shareUpdateCount += children.length;

			for (const child of children) {
				if (child.share_id !== rootFolder.share_id) {
					await this.save({
						id: child.id,
						share_id: rootFolder.share_id,
						updated_time: Date.now(),
					}, { autoTimestamp: false });
				}
			}

			sharedFolderIds.push(rootFolder.id);
			sharedFolderIds = sharedFolderIds.concat(children.map(c => c.id));
		}

		// Now that we've set the share ID on all the sub-folders of the shared
		// folders, those that remain should not be shared anymore. For example,
		// if they've been moved out of a shared folder.
		// await this.unshareItems(ModelType.Folder, sharedFolderIds);

		const sql = ['SELECT id, parent_id FROM folders WHERE share_id != ""'];
		if (sharedFolderIds.length) {
			sql.push(` AND id NOT IN ("${sharedFolderIds.join('","')}")`);
		}

		const foldersToUnshare: FolderEntity[] = await this.db().selectAll(sql.join(' '));

		report.unshareUpdateCount += foldersToUnshare.length;

		for (const item of foldersToUnshare) {
			await this.save({
				id: item.id,
				share_id: '',
				updated_time: Date.now(),
				parent_id: item.parent_id,
			}, { autoTimestamp: false });
		}

		logger.debug('updateFolderShareIds:', report);
	}

	public static async updateNoteShareIds() {
		// Find all the notes where the share_id is not the same as the
		// parent share_id because we only need to update those.
		const rows = await this.db().selectAll(`
			SELECT notes.id, folders.share_id, notes.parent_id
			FROM notes
			LEFT JOIN folders ON notes.parent_id = folders.id
			WHERE notes.share_id != folders.share_id
		`);

		logger.debug('updateNoteShareIds: notes to update:', rows.length);

		for (const row of rows) {
			await Note.save({
				id: row.id,
				share_id: row.share_id || '',
				parent_id: row.parent_id,
				updated_time: Date.now(),
			}, { autoTimestamp: false });
		}
	}

	public static async updateResourceShareIds(resourceService: ResourceService) {
		// Updating the share_id property of the resources is complex because:
		//
		// The resource association to the note is done indirectly via the
		// ResourceService
		//
		// And a given resource can appear inside multiple notes. However, for
		// sharing we make the assumption that a resource can be part of only
		// one share (one-to-one relationship because "share_id" is part of the
		// "resources" table), which is usually the case. By copying and pasting
		// note content from one note to another it's however possible to have
		// the same resource in multiple shares (or in a non-shared and a shared
		// folder).
		//
		// So in this function we take this into account - if a shared resource
		// is part of multiple notes, we duplicate that resource so that each
		// note has its own instance. When such duplication happens, we need to
		// resume the process from the start (thus the loop) so that we deal
		// with the right note/resource associations.

		interface Row {
			id: string;
			share_id: string;
			is_shared: number;
			resource_is_shared: number;
			resource_share_id: string;
		}

		for (let i = 0; i < 5; i++) {
			// Find all resources where share_id is different from parent note
			// share_id. Then update share_id on all these resources. Essentially it
			// makes it match the resource share_id to the note share_id. At the
			// same time we also process the is_shared property.

			const rows = (await this.db().selectAll(`
				SELECT
					r.id,
					n.share_id,
					n.is_shared,
					r.is_shared as resource_is_shared,
					r.share_id as resource_share_id
				FROM note_resources nr
				LEFT JOIN resources r ON nr.resource_id = r.id
				LEFT JOIN notes n ON nr.note_id = n.id
				WHERE (
					n.share_id != r.share_id
					OR n.is_shared != r.is_shared
				) AND nr.is_associated = 1
			`)) as Row[];

			if (!rows.length) return;

			logger.debug('updateResourceShareIds: resources to update:', rows.length);

			const resourceIds = rows.map(r => r.id);

			interface NoteResourceRow {
				resource_id: string;
				note_id: string;
				share_id: string;
			}

			// Now we check, for each resource, that it is associated with only
			// one note. If it is not, we create duplicate resources so that
			// each note has its own separate resource.

			const noteResourceAssociations = await this.db().selectAll(`
				SELECT resource_id, note_id, notes.share_id
				FROM note_resources
				LEFT JOIN notes ON notes.id = note_resources.note_id
				WHERE resource_id IN ('${resourceIds.join('\',\'')}')
				AND is_associated = 1
			`) as NoteResourceRow[];

			const resourceIdToNotes: Record<string, NoteResourceRow[]> = {};

			for (const r of noteResourceAssociations) {
				if (!resourceIdToNotes[r.resource_id]) resourceIdToNotes[r.resource_id] = [];
				resourceIdToNotes[r.resource_id].push(r);
			}

			let hasCreatedResources = false;

			for (const [resourceId, rows] of Object.entries(resourceIdToNotes)) {
				if (rows.length <= 1) continue;

				for (let i = 0; i < rows.length - 1; i++) {
					const row = rows[i];
					const note: NoteEntity = await Note.load(row.note_id);
					if (!note) continue; // probably got deleted in the meantime?
					const newResource = await Resource.duplicateResource(resourceId);
					logger.info(`updateResourceShareIds: Automatically created resource "${newResource.id}" to replace resource "${resourceId}" because it is shared and duplicate across notes:`, row);
					const regex = new RegExp(resourceId, 'gi');
					const newBody = note.body.replace(regex, newResource.id);
					await Note.save({
						id: note.id,
						body: newBody,
						parent_id: note.parent_id,
						updated_time: Date.now(),
					}, {
						autoTimestamp: false,
					});
					hasCreatedResources = true;
				}
			}

			// If we have created resources, we refresh the note/resource
			// associations using ResourceService and we resume the process.
			// Normally, if the user didn't create any new notes or resources in
			// the meantime, the second loop should find that each shared
			// resource is associated with only one note.

			if (hasCreatedResources) {
				await resourceService.indexNoteResources();
				continue;
			} else {
				// If all is good, we can set the share_id and is_shared
				// property of the resource.
				const now = Date.now();
				for (const row of rows) {
					const resource: ResourceEntity = {
						id: row.id,
						share_id: row.share_id || '',
						is_shared: row.is_shared,
						updated_time: now,
					};

					// When a resource becomes published or shared, we set
					// `blob_updated_time` to ensure that the resource content
					// is uploaded too during the next sync operation.
					//
					// This is necessary because Joplin Server needs to
					// associate `share_id` or `is_shared` with the resource
					// content for sharing to work. Otherwise the share
					// recipient will only get the resource metadata.
					if (row.is_shared !== row.resource_is_shared || row.share_id !== row.resource_share_id) {
						resource.blob_updated_time = now;
					}

					await Resource.save(resource, { autoTimestamp: false });
				}
				return;
			}
		}

		throw new Error('Failed to update resource share IDs');
	}

	public static async updateAllShareIds(resourceService: ResourceService) {
		await this.updateFolderShareIds();
		await this.updateNoteShareIds();
		await this.updateResourceShareIds(resourceService);
	}

	// Clear the "share_id" property for the items that are associated with a
	// share that no longer exists.
	public static async updateNoLongerSharedItems(activeShareIds: string[]) {
		const tableNameToClasses: Record<string, any> = {
			'folders': Folder,
			'notes': Note,
			'resources': Resource,
		};

		const report: any = {};

		for (const tableName of ['folders', 'notes', 'resources']) {
			const ItemClass = tableNameToClasses[tableName];
			const hasParentId = tableName !== 'resources';

			const fields = ['id'];
			if (hasParentId) fields.push('parent_id');

			const query = activeShareIds.length ? `
				SELECT ${this.db().escapeFields(fields)} FROM ${tableName}
				WHERE share_id != "" AND share_id NOT IN ("${activeShareIds.join('","')}")
			` : `
				SELECT ${this.db().escapeFields(fields)} FROM ${tableName}
				WHERE share_id != ''
			`;

			const rows = await this.db().selectAll(query);

			report[tableName] = rows.length;

			for (const row of rows) {
				const toSave: any = {
					id: row.id,
					share_id: '',
					updated_time: Date.now(),
				};

				if (hasParentId) toSave.parent_id = row.parent_id;

				await ItemClass.save(toSave, { autoTimestamp: false });
			}
		}

		logger.debug('updateNoLongerSharedItems:', report);
	}

	public static async allAsTree(folders: FolderEntity[] = null, options: any = null) {
		interface FolderWithNotes extends FolderEntity {
			notes?: NoteEntity[];
		}

		const all: FolderWithNotes[] = folders ? folders : await this.all(options);

		if (options && options.includeNotes) {
			for (const folder of all) {
				folder.notes = await Note.previews(folder.id);
			}
		}

		// https://stackoverflow.com/a/49387427/561309
		function getNestedChildren(models: FolderEntityWithChildren[], parentId: string) {
			const nestedTreeStructure = [];
			const length = models.length;

			for (let i = 0; i < length; i++) {
				const model = models[i];

				if (model.parent_id === parentId) {
					const children = getNestedChildren(models, model.id);

					if (children.length > 0) {
						model.children = children;
					}

					nestedTreeStructure.push(model);
				}
			}

			return nestedTreeStructure;
		}

		return getNestedChildren(all, '');
	}

	public static folderPath(folders: FolderEntity[], folderId: string) {
		const idToFolders: Record<string, FolderEntity> = {};
		for (let i = 0; i < folders.length; i++) {
			idToFolders[folders[i].id] = folders[i];
		}

		const path = [];
		while (folderId) {
			const folder = idToFolders[folderId];
			if (!folder) break; // Shouldn't happen
			path.push(folder);
			folderId = folder.parent_id;
		}

		path.reverse();

		return path;
	}

	public static folderPathString(folders: FolderEntity[], folderId: string, maxTotalLength = 80) {
		const path = this.folderPath(folders, folderId);

		let currentTotalLength = 0;
		for (let i = 0; i < path.length; i++) {
			currentTotalLength += path[i].title.length;
		}

		let pieceLength = maxTotalLength;
		if (currentTotalLength > maxTotalLength) {
			pieceLength = maxTotalLength / path.length;
		}

		const output = [];
		for (let i = 0; i < path.length; i++) {
			output.push(substrWithEllipsis(path[i].title, 0, pieceLength));
		}

		return output.join(' / ');
	}

	public static buildTree(folders: FolderEntity[]): FolderEntityWithChildren[] {
		const idToFolders: Record<string, any> = {};
		for (let i = 0; i < folders.length; i++) {
			idToFolders[folders[i].id] = { ...folders[i] };
			idToFolders[folders[i].id].children = [];
		}

		const rootFolders = [];
		for (const folderId in idToFolders) {
			if (!idToFolders.hasOwnProperty(folderId)) continue;

			const folder = idToFolders[folderId];
			if (!folder.parent_id) {
				rootFolders.push(folder);
			} else {
				if (!idToFolders[folder.parent_id]) {
					// It means the notebook is referring a folder that doesn't exist. In theory it shouldn't happen
					// but sometimes does - https://github.com/laurent22/joplin/issues/1068#issuecomment-450594708
					rootFolders.push(folder);
				} else {
					idToFolders[folder.parent_id].children.push(folder);
				}
			}
		}

		return rootFolders;
	}

	public static async sortFolderTree(folders: FolderEntityWithChildren[] = null) {
		const output = folders ? folders : await this.allAsTree();

		const sortFoldersAlphabetically = (folders: FolderEntityWithChildren[]) => {
			folders.sort((a: FolderEntityWithChildren, b: FolderEntityWithChildren) => {
				if (a.parent_id === b.parent_id) {
					return a.title.localeCompare(b.title, undefined, { sensitivity: 'accent' });
				}
				return 0;
			});
			return folders;
		};

		const sortFolders = (folders: FolderEntityWithChildren[]) => {
			for (let i = 0; i < folders.length; i++) {
				const folder = folders[i];
				if (folder.children) {
					folder.children = sortFoldersAlphabetically(folder.children);
					sortFolders(folder.children);
				}
			}
			return folders;
		};

		sortFolders(sortFoldersAlphabetically(output));
		return output;
	}

	public static async loadByTitleAndParent(title: string, parentId: string, options: LoadOptions = null): Promise<FolderEntity> {
		return await this.modelSelectOne(`SELECT ${this.selectFields(options)} FROM folders WHERE title = ? and parent_id = ?`, [title, parentId]);
	}

	public static load(id: string, options: LoadOptions = null): Promise<FolderEntity> {
		if (id === this.conflictFolderId()) return Promise.resolve(this.conflictFolder());
		if (id === getTrashFolderId()) return Promise.resolve(getTrashFolder());
		return super.load(id, options);
	}

	public static defaultFolder() {
		return this.modelSelectOne('SELECT * FROM folders ORDER BY created_time DESC LIMIT 1');
	}

	public static async canNestUnder(folderId: string, targetFolderId: string) {
		if (folderId === targetFolderId) return false;

		const folder = await Folder.load(folderId);
		if (isRootSharedFolder(folder)) return false;

		const conflictFolderId = Folder.conflictFolderId();
		if (folderId === conflictFolderId || targetFolderId === conflictFolderId) return false;

		if (!targetFolderId) return true;

		while (true) {
			const folder = await Folder.load(targetFolderId);
			if (!folder.parent_id) break;
			if (folder.parent_id === folderId) return false;
			targetFolderId = folder.parent_id;
		}

		return true;
	}

	public static async moveToFolder(folderId: string, targetFolderId: string) {
		if (!(await this.canNestUnder(folderId, targetFolderId))) throw new Error(_('Cannot move notebook to this location'));

		// When moving a note to a different folder, the user timestamp is not updated.
		// However updated_time is updated so that the note can be synced later on.

		const modifiedFolder = {
			id: folderId,
			parent_id: targetFolderId,
			updated_time: time.unixMs(),
		};

		return Folder.save(modifiedFolder, { autoTimestamp: false });
	}

	// These "duplicateCheck" and "reservedTitleCheck" should only be done when a user is
	// manually creating a folder. They shouldn't be done for example when the folders
	// are being synced to avoid any strange side-effects. Technically it's possible to
	// have folders and notes with duplicate titles (or no title), or with reserved words.
	public static async save(o: FolderEntity, options: any = null) {
		if (!options) options = {};

		if (options.userSideValidation === true) {
			if (!('duplicateCheck' in options)) options.duplicateCheck = true;
			if (!('reservedTitleCheck' in options)) options.reservedTitleCheck = true;
			if (!('stripLeftSlashes' in options)) options.stripLeftSlashes = true;

			if (o.id && o.parent_id && o.id === o.parent_id) {
				throw new Error('Parent ID cannot be the same as ID');
			}
		}

		if (options.stripLeftSlashes === true && o.title) {
			while (o.title.length && (o.title[0] === '/' || o.title[0] === '\\')) {
				o.title = o.title.substr(1);
			}
		}

		// We allow folders with duplicate titles so that folders with the same title can exist under different parent folder. For example:
		//
		// PHP
		//     Code samples
		//     Doc
		// Java
		//     My project
		//     Doc

		// if (options.duplicateCheck === true && o.title) {
		// 	let existingFolder = await Folder.loadByTitle(o.title);
		// 	if (existingFolder && existingFolder.id != o.id) throw new Error(_('A notebook with this title already exists: "%s"', o.title));
		// }

		if (options.reservedTitleCheck === true && o.title) {
			if (o.title === Folder.conflictFolderTitle()) throw new Error(_('Notebooks cannot be named "%s", which is a reserved title.', o.title));
		}

		syncDebugLog.info('Folder Save:', o);

		let savedFolder: FolderEntity = await super.save(o, options);

		// Ensures that any folder added to the state has all the required
		// properties, in particular "share_id" and "parent_id', which are
		// required in various parts of the code.
		if (!('share_id' in savedFolder) || !('parent_id' in savedFolder) || !('deleted_time' in savedFolder)) {
			savedFolder = await this.load(savedFolder.id);
		}

		this.dispatch({
			type: 'FOLDER_UPDATE_ONE',
			item: savedFolder,
		});

		return savedFolder;
	}

	public static async trashItemsOlderThan(ttl: number) {
		const cutOffTime = Date.now() - ttl;

		const getItemIds = async (table: string, cutOffTime: number): Promise<string[]> => {
			const items = await this.db().selectAll(`SELECT id from ${table} WHERE deleted_time > 0 AND deleted_time < ?`, [cutOffTime]);
			return items.map(i => i.id);
		};

		return {
			noteIds: await getItemIds('notes', cutOffTime),
			folderIds: await getItemIds('folders', cutOffTime),
		};
	}

	public static serializeIcon(icon: FolderIcon): string {
		return icon ? JSON.stringify(icon) : '';
	}

	public static unserializeIcon(icon: string): FolderIcon {
		if (!icon) return null;
		return {
			...defaultFolderIcon(),
			...JSON.parse(icon),
		};
	}

	public static shouldShowFolderIcons(folders: FolderEntity[]) {
		// If at least one of the folder has an icon, then we display icons for all
		// folders (those without one will get the default icon). This is so that
		// visual alignment is correct for all folders, otherwise the folder tree
		// looks messy.
		return !!folders.find(f => !!f.icon);
	}

}