/**
 * Copyright (c) 2015-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 *  strict
 */

import invariant from '../jsutils/invariant';
import { GraphQLError } from '../error';
import { visit, visitInParallel, visitWithTypeInfo } from '../language/visitor';

import { GraphQLSchema } from '../type/schema';
import { assertValidSchema } from '../type/validate';
import { TypeInfo } from '../utilities/TypeInfo';
import { specifiedRules } from './specifiedRules';
import ValidationContext from './ValidationContext';

/**
 * Implements the "Validation" section of the spec.
 *
 * Validation runs synchronously, returning an array of encountered errors, or
 * an empty array if no errors were encountered and the document is valid.
 *
 * A list of specific validation rules may be provided. If not provided, the
 * default list of rules defined by the GraphQL specification will be used.
 *
 * Each validation rules is a function which returns a visitor
 * (see the language/visitor API). Visitor methods are expected to return
 * GraphQLErrors, or Arrays of GraphQLErrors when invalid.
 *
 * Optionally a custom TypeInfo instance may be provided. If not provided, one
 * will be created from the provided schema.
 */
export function validate(schema, ast, rules, typeInfo) {
  !ast ? invariant(0, 'Must provide document') : void 0;
  // If the schema used for validation is invalid, throw an error.
  assertValidSchema(schema);
  return visitUsingRules(schema, typeInfo || new TypeInfo(schema), ast, rules || specifiedRules);
}

/**
 * This uses a specialized visitor which runs multiple visitors in parallel,
 * while maintaining the visitor skip and break API.
 *
 * @internal
 */
function visitUsingRules(schema, typeInfo, documentAST, rules) {
  var context = new ValidationContext(schema, documentAST, typeInfo);
  var visitors = rules.map(function (rule) {
    return rule(context);
  });
  // Visit the whole document with each instance of all provided rules.
  visit(documentAST, visitWithTypeInfo(typeInfo, visitInParallel(visitors)));
  return context.getErrors();
}