joplin/packages/app-desktop/services/sortOrder/notesSortOrderUtils.ts

import Setting from '@joplin/lib/models/Setting';

let fields: string[] = null;
let perFieldReverse: { [field: string]: boolean } = null;

export const notesSortOrderFieldArray = (): string[] => {
	// The order of the fields is strictly determinate.
	if (fields === null) {
		fields = Setting.enumOptionValues('notes.sortOrder.field').sort().reverse();
	}
	return fields;
};

export const notesSortOrderNextField = (currentField: string) => {
	const fields = notesSortOrderFieldArray();
	const index = fields.indexOf(currentField);
	if (index < 0) {
		return currentField;
	} else {
		return fields[(index + 1) % fields.length];
	}
};

export const setNotesSortOrder = (field?: string, reverse?: boolean) => {
	// field: Sort order's field. undefined means changing a field cyclicly.
	// reverse: whether the sort order is reversed or not. undefined means toggling.
	let nextField = field;
	let nextReverse = reverse;
	const currentField = Setting.value('notes.sortOrder.field');
	const currentReverse = Setting.value('notes.sortOrder.reverse');
	const enabled = Setting.value('notes.perFieldReversalEnabled');
	if (enabled) {
		if (perFieldReverse === null) {
			perFieldReverse = { ...Setting.value('notes.perFieldReverse') };
		}
	}
	if (typeof field === 'undefined') {
		if (typeof reverse === 'undefined') {
			// If both arguments are undefined, the next field is selected.
			nextField = notesSortOrderNextField(currentField);
		} else {
			nextField = currentField;
		}
	}
	if (typeof reverse === 'undefined') {
		if (enabled && perFieldReverse.hasOwnProperty(nextField)) {
			nextReverse = !!perFieldReverse[nextField];
		} else {
			nextReverse = currentReverse;
		}
	}
	if (currentField !== nextField) {
		Setting.setValue('notes.sortOrder.field', nextField);
	}
	if (currentReverse !== nextReverse) {
		Setting.setValue('notes.sortOrder.reverse', nextReverse);
	}
	if (enabled) {
		// nextField is sane here.
		nextReverse = !!nextReverse;
		if (perFieldReverse[nextField] !== nextReverse) {
			perFieldReverse[nextField] = nextReverse;
			Setting.setValue('notes.perFieldReverse', { ...perFieldReverse });
		}
	}
};