node-data-modeling/src/serialization/deserialize.js

"use strict";

const defaultValue = require("default-value");
const mapObj = require("map-obj");

const isPlaceholder = require("../util/is-placeholder");
const createPlaceholderManager = require("./placeholder-manager");

function isReference(serializedData) {
	return (serializedData != null && serializedData._d_sT === "cTR");
}

/* FIXME: Pass both key and value to custom deserializer */

module.exports = function createDeserializer(topLevelType, topLevelData, typeMap, options = {}) {
	let seen = new Map();
	let placeholders = createPlaceholderManager();

	let customDeserializer = defaultValue(options.deserializer, (value) => value);

	function deserializeSequenceItems(itemRule, entries) {
		let seenPlaceholder = false;

		let items = entries.map((item) => {
			let deserializedValue = deserializeEntry(itemRule, item);

			if (isPlaceholder(deserializedValue)) {
				seenPlaceholder = true;
			}

			return deserializedValue;
		});

		return {
			items: items,
			seenPlaceholder: seenPlaceholder
		};
	}

	function deserializeSet(rule, entries) {
		let {items, seenPlaceholder} = deserializeSequenceItems(rule._itemType, entries);
		let set = new Set(items);

		if (seenPlaceholder) {
			placeholders.markSet(set);
		}

		return set;
	}

	function deserializeArray(rule, entries) {
		let {items, seenPlaceholder} = deserializeSequenceItems(rule._itemType, entries);

		if (seenPlaceholder) {
			placeholders.markArray(items);
		}

		return items;
	}

	function deserializeMap(rule, entries) {
		let seenPlaceholder = false;

		let map = new Map(entries.map(([itemKey, itemValue]) => {
			let deserializedKey = deserializeEntry(rule._keyType, itemKey);
			let deserializedValue = deserializeEntry(rule._itemType, itemValue);

			if (isPlaceholder(deserializedKey) || isPlaceholder(deserializedValue)) {
				seenPlaceholder = true;
			}

			return [
				deserializedKey,
				deserializedValue
			];
		}));

		if (seenPlaceholder) {
			placeholders.markMap(map);
		}

		return map;
	}

	function deserializeEntry(rule, serializedData) {
		if (serializedData == null) {
			return customDeserializer(serializedData);
		} else if (rule._isCustomType) {
			return deserializeInstanceOrReference(rule, serializedData);
		} else if (rule._isCustomRegistryType) {
			return deserializeInstanceOrReference(rule._registry._getType(rule._name), serializedData);
		} else if (rule._isRegistryTrait || rule._isTrait) {
			return deserializeInstanceFuzzy(serializedData);
		} else if (rule._collectionType === "set") {
			if (serializedData._d_sT === "gS") {
				return deserializeSet(rule, serializedData.entries);
			} else {
				/* FIXME: Clearer error message */
				throw new Error("Expected guarded set, but got something else instead");
			}
		} else if (rule._collectionType === "map") {
			if (serializedData._d_sT === "gM") {
				return deserializeMap(rule, serializedData.entries);
			} else {
				/* FIXME: Clearer error message */
				throw new Error("Expected guarded map, but got something else instead");
			}
		} else if (rule._collectionType === "array") {
			if (serializedData._d_sT === "gA") {
				return deserializeArray(rule, serializedData.entries);
			} else {
				/* FIXME: Clearer error message */
				throw new Error("Expected guarded array, but got something else instead");
			}
		} else {
			/* This also covers `either` rules where the serializedData is a type instance or reference. */
			return deserializeEntryFuzzy(serializedData);
		}
	}

	function deserializeEntryFuzzy(serializedData) {
		if (serializedData != null && (serializedData._d_sT === "cT" || serializedData._d_sT === "cTR")) {
			return deserializeInstanceFuzzy(serializedData);
		} else {
			return customDeserializer(serializedData);
		}
	}

	function deserializeInstance(typeFactory, serializedData) {
		let placeholderProperties = [];

		let deserializedData = mapObj(serializedData.data, (key, value) => {
			let rule = typeFactory._cumulativeSchema[key];
			let deserializedValue = deserializeEntry(rule, value);

			if (isPlaceholder(deserializedValue)) {
				placeholderProperties.push(key);
			}

			return [key, deserializedValue];
		});

		let instance = typeFactory(deserializedData);

		for (let property of placeholderProperties) {
			placeholders.markProperty(instance, property);
		}

		seen.set(serializedData.id, instance);

		return instance;
	}

	function deserializeReference(serializedData) {
		return {
			_isDeserializationPlaceholder: true,
			_deserializationId: serializedData.id
		};
	}

	function deserializeInstanceOrReference(typeFactory, serializedData) {
		if (isReference(serializedData)) {
			return deserializeReference(serializedData);
		} else {
			return deserializeInstance(typeFactory, serializedData);
		}
	}

	function deserializeInstanceFuzzy(serializedData) {
		if (isReference(serializedData)) {
			return deserializeReference(serializedData);
		} else if (typeMap.has(serializedData.type)) {
			return deserializeInstance(typeMap.get(serializedData.type), serializedData);
		} else {
			throw new Error(`Encountered instance of an unknown type with hash ${serializedData.type}`);
		}
	}

	let topLevelInstance = deserializeInstance(topLevelType, topLevelData);
	placeholders.fillInPlaceholders(seen);
	return topLevelInstance;
};