built_in.dart

// Copyright 2019 Google Inc. Use of this source code is governed by an
// MIT-style license that can be found in the LICENSE file or at
// https://opensource.org/licenses/MIT.

import 'dart:collection';

import '../ast/css.dart';
import '../ast/node.dart';
import '../callable.dart';
import '../exception.dart';
import '../extend/extender.dart';
import '../module.dart';
import '../value.dart';

/// A module provided by Sass, available under the special `sass:` URL space.
class BuiltInModule<T extends AsyncCallable> implements Module<T> {
  final Uri url;
  final Map<String, T> functions;
  final Map<String, T> mixins;
  final Map<String, Value> variables;

  List<Module<T>> get upstream => const [];
  Map<String, AstNode> get variableNodes => const {};
  Extender get extender => Extender.empty;
  CssStylesheet get css => CssStylesheet.empty(url: url);
  bool get transitivelyContainsCss => false;
  bool get transitivelyContainsExtensions => false;

  BuiltInModule(String name,
      {Iterable<T> functions, Iterable<T> mixins, Map<String, Value> variables})
      : url = Uri(scheme: "sass", path: name),
        functions = _callableMap(functions),
        mixins = _callableMap(mixins),
        variables = _variableMap(variables);

  /// Returns a map from [callables]' names to their values.
  static Map<String, T> _callableMap<T extends AsyncCallable>(
          Iterable<T> callables) =>
      UnmodifiableMapView(callables == null
          ? {}
          : UnmodifiableMapView(
              {for (var callable in callables) callable.name: callable}));

  /// Returns a map from [variables]' names to their values.
  static Map<String, V> _variableMap<V>(Map<String, V> variables) =>
      UnmodifiableMapView(
          variables == null ? {} : UnmodifiableMapView(variables));

  void setVariable(String name, Value value, AstNode nodeWithSpan) {
    if (!variables.containsKey(name)) {
      throw SassScriptException("Undefined variable.");
    }
    throw SassScriptException("Cannot modify built-in variable \$$name.");
  }

  Module<T> cloneCss() => this;
}