"use strict";

// Simple data type to represent a query path and corresponding schema path tied together, because these are basically always used together, and it would bloat up the implementation code otherwise

function createInstance({ queryPath, schemaPath, queryObject, schemaObject, parent }) {
	let self;
	// eslint-disable-next-line no-return-assign
	return self = {
		queryPath: queryPath,
		schemaPath: schemaPath,
		query: queryObject,
		schema: schemaObject,
		child: function (queryKey) {
			let newQueryPath = (queryKey != null)
				? queryPath.concat([ queryKey ])
				: queryPath;

			let newQueryObject = (queryKey != null)
				? queryObject[queryKey]
				: queryObject;

			// TODO: Is this correct even when the queryKey is null, and so we remain at the same object?
			// $key is used for handling aliases
			let effectiveSchemaKey = (newQueryObject?.$key != null)
				? newQueryObject.$key
				: queryKey;

			let newSchemaPath = (effectiveSchemaKey != null)
				? schemaPath.concat([ effectiveSchemaKey ])
				: schemaPath;

			let newSchemaObject = (effectiveSchemaKey != null)
				? schemaObject[effectiveSchemaKey]
				: schemaObject;

			return createInstance({
				queryPath: newQueryPath,
				schemaPath: newSchemaPath,
				queryObject: newQueryObject,
				schemaObject: newSchemaObject,
				parent: self
			});
		},
		parent: parent,
		override: function ({ query, schema }) {
			return createInstance({
				queryPath: queryPath,
				schemaPath: schemaPath,
				queryObject: query ?? queryObject,
				schemaObject: schema ?? schemaObject,
				// An override doesn't change the path, so the parent shouldn't change either
				parent: self.parent
			});
		},
		toPathString: function () {
			return queryPath
				.map((segment, i) => {
					if (segment === schemaPath[i]) {
						return segment;
					} else {
						// This is used for representing aliases, showing the original schema key in brackets
						return `${segment} [${schemaPath[i]}]`;
					}
				})
				.join(" -> ");
		}
	 };
}

module.exports = function createCursor({ query, schema }) {
	return createInstance({
		queryPath: [],
		schemaPath: [],
		queryObject: query,
		schemaObject: schema,
		parent: undefined
	});
};