fontoxpath/src/selectors/functions/builtInFunctions.operators.js

A minimalistic XPath 3.1 engine in JavaScript

import Sequence from '../dataTypes/Sequence';
import createAtomicValue from '../dataTypes/createAtomicValue';
import { ready, notReady, DONE_TOKEN } from '../util/iterators';

function opTo (_dynamicContext, fromSequence, toSequence) {
	// shortcut the non-trivial case of both values being known
	// RangeExpr is inclusive: 1 to 3 will make (1,2,3)
	const from = fromSequence.tryGetFirst();
	const to = toSequence.tryGetFirst();
	let fromValue = null;
	let toValue = null;

	if (from.ready && to.ready) {
		if (from.value === null || to.value === null) {
			return Sequence.empty();
		}
		fromValue = from.value.value;
		toValue = to.value.value;
		if (fromValue > toValue) {
			return Sequence.empty();
		}
		// By providing a length, we do not have to hold an end condition into account
		return new Sequence({
			next: () => ready(createAtomicValue(fromValue++, 'xs:integer'))
		}, toValue - fromValue + 1);
	}
	return new Sequence({
		next: () => {
			if (fromValue === null) {
				const from = fromSequence.tryGetFirst();
				if (!from.ready) {
					return notReady(from.promise);
				}
				if (from.value === null) {
					return DONE_TOKEN;
				}
				fromValue = from.value.value;
			}
			if (toValue === null) {
				const to = toSequence.tryGetFirst();
				if (!to.ready) {
					return notReady(to.promise);
				}
				if (to.value === null) {
					return DONE_TOKEN;
				}
				toValue = to.value.value;
			}
			if (fromValue > toValue) {
				return DONE_TOKEN;
			}
			return ready(createAtomicValue(fromValue++, 'xs:integer'));
		}
	});
}

export default {
	declarations: [
		{
			name: 'op:to',
			argumentTypes: ['xs:integer?', 'xs:integer?'],
			returnType: 'xs:integer*',
			callFunction: opTo
		},
	],
	functions: {
		to: opTo
	}
};