blob: a9a50791a9021aeb1ca1c0bdadac2dae960f3c02 [file] [log] [blame]
// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
import 'dart:collection';
import 'dart:convert';
import 'dart:typed_data';
import '../schema/schema.dart';
import '../uint8list_ops.dart' as utils;
enum _ComparisonType { equality, inequality }
/// Sledge can be queried to return documents matching certain criteria on certain fields.
/// This class stores the information needed to maintain indexes to respond efficiently to
/// the queries.
/// The indexes can handle equality over multiple fields, and inequality on a single field.
class IndexDefinition {
final Schema _schema;
/// Stores the name of the field concerned by the index, and what kind of comparison is
/// done over the said field.
final _filterMap = SplayTreeMap<String, _ComparisonType>();
static const _jsonFieldsMapKey = 'fields';
static const _jsonSchemaKey = 'schema';
static const int _hashLength = 20;
/// Default constructor.
/// `schema` defines on which Schema this Index applies.
/// `fieldsWithEquality` is the list of fields on which equality statements will be run.
/// `fieldWithInequality` is the name of the field on which the inequality statement and/or sorting can run.
{List<String> fieldsWithEquality, String fieldWithInequality}) {
fieldsWithEquality ??= <String>[];
for (final fieldWithEquality in fieldsWithEquality) {
if (_filterMap.containsKey(fieldWithEquality)) {
throw ArgumentError(
'Field `$fieldWithEquality` must not appear multiple times in fieldsWithEquality.');
if (fieldWithInequality == fieldWithEquality) {
throw ArgumentError(
'Field `$fieldWithEquality` must not be part of both fieldsWithEquality and fieldWithInequality.');
_filterMap[fieldWithEquality] = _ComparisonType.equality;
if (fieldWithInequality != null) {
_filterMap[fieldWithInequality] = _ComparisonType.inequality;
/// Factory that builds an IndexDefinition from a JSON object.
factory IndexDefinition.fromJson(Map<String, dynamic> map) {
List<String> fieldsWithEquality = <String>[];
String fieldWithInequality;
map[_jsonFieldsMapKey].forEach((key, value) {
_ComparisonType comp = _ComparisonType.values[value];
switch (comp) {
case _ComparisonType.equality:
case _ComparisonType.inequality:
fieldWithInequality = key;
Schema schema = Schema.fromJson(map[_jsonSchemaKey]);
return IndexDefinition(schema,
fieldsWithEquality: fieldsWithEquality,
fieldWithInequality: fieldWithInequality);
/// Returns the object'S JSON representation of the IndexDefinition.
/// Called by dart:convert's JsonCodec.
dynamic toJson() {
Map<String, int> jsonFieldMap = _filterMap
.map((key, value) => MapEntry<String, int>(key, value.index));
final jsonMap = <String, dynamic>{
_jsonFieldsMapKey: jsonFieldMap,
_jsonSchemaKey: _schema
return jsonMap;
void _checkBelongsToSchema(String field) {
if (!_schema.schemaDescription.containsKey(field)) {
throw ArgumentError('Field `$field` is not part of the schema.');
/// Returns a 20 byte hash.
Uint8List get hash {
// TODO: Compute a hash not based on the JSON representation.
String jsonString = json.encode(this);
Uint8List bytes = utf8.encode(jsonString);
Uint8List digest = utils.hash(bytes);
assert(digest.length == _hashLength);
return digest;