// @flow strict

import inspect from '../../jsutils/inspect';
import invariant from '../../jsutils/invariant';

import { GraphQLError } from '../../error/GraphQLError';

import { Kind } from '../../language/kinds';
import { type ASTVisitor } from '../../language/visitor';
import { type OperationTypeNode } from '../../language/ast';
import {
  type DirectiveLocationEnum,
  DirectiveLocation,
} from '../../language/directiveLocation';

import { specifiedDirectives } from '../../type/directives';

import {
  type ValidationContext,
  type SDLValidationContext,
} from '../ValidationContext';

/**
 * Known directives
 *
 * A GraphQL document is only valid if all `@directives` are known by the
 * schema and legally positioned.
 */
export function KnownDirectivesRule(
  context: ValidationContext | SDLValidationContext,
): ASTVisitor {
  const locationsMap = Object.create(null);

  const schema = context.getSchema();
  const definedDirectives = schema
    ? schema.getDirectives()
    : specifiedDirectives;
  for (const directive of definedDirectives) {
    locationsMap[directive.name] = directive.locations;
  }

  const astDefinitions = context.getDocument().definitions;
  for (const def of astDefinitions) {
    if (def.kind === Kind.DIRECTIVE_DEFINITION) {
      locationsMap[def.name.value] = def.locations.map(name => name.value);
    }
  }

  return {
    Directive(node, _key, _parent, _path, ancestors) {
      const name = node.name.value;
      const locations = locationsMap[name];

      if (!locations) {
        context.reportError(
          new GraphQLError(`Unknown directive "@${name}".`, node),
        );
        return;
      }

      const candidateLocation = getDirectiveLocationForASTPath(ancestors);
      if (candidateLocation && locations.indexOf(candidateLocation) === -1) {
        context.reportError(
          new GraphQLError(
            `Directive "@${name}" may not be used on ${candidateLocation}.`,
            node,
          ),
        );
      }
    },
  };
}

function getDirectiveLocationForASTPath(ancestors) {
  const appliedTo = ancestors[ancestors.length - 1];
  invariant(!Array.isArray(appliedTo));

  switch (appliedTo.kind) {
    case Kind.OPERATION_DEFINITION:
      return getDirectiveLocationForOperation(appliedTo.operation);
    case Kind.FIELD:
      return DirectiveLocation.FIELD;
    case Kind.FRAGMENT_SPREAD:
      return DirectiveLocation.FRAGMENT_SPREAD;
    case Kind.INLINE_FRAGMENT:
      return DirectiveLocation.INLINE_FRAGMENT;
    case Kind.FRAGMENT_DEFINITION:
      return DirectiveLocation.FRAGMENT_DEFINITION;
    case Kind.VARIABLE_DEFINITION:
      return DirectiveLocation.VARIABLE_DEFINITION;
    case Kind.SCHEMA_DEFINITION:
    case Kind.SCHEMA_EXTENSION:
      return DirectiveLocation.SCHEMA;
    case Kind.SCALAR_TYPE_DEFINITION:
    case Kind.SCALAR_TYPE_EXTENSION:
      return DirectiveLocation.SCALAR;
    case Kind.OBJECT_TYPE_DEFINITION:
    case Kind.OBJECT_TYPE_EXTENSION:
      return DirectiveLocation.OBJECT;
    case Kind.FIELD_DEFINITION:
      return DirectiveLocation.FIELD_DEFINITION;
    case Kind.INTERFACE_TYPE_DEFINITION:
    case Kind.INTERFACE_TYPE_EXTENSION:
      return DirectiveLocation.INTERFACE;
    case Kind.UNION_TYPE_DEFINITION:
    case Kind.UNION_TYPE_EXTENSION:
      return DirectiveLocation.UNION;
    case Kind.ENUM_TYPE_DEFINITION:
    case Kind.ENUM_TYPE_EXTENSION:
      return DirectiveLocation.ENUM;
    case Kind.ENUM_VALUE_DEFINITION:
      return DirectiveLocation.ENUM_VALUE;
    case Kind.INPUT_OBJECT_TYPE_DEFINITION:
    case Kind.INPUT_OBJECT_TYPE_EXTENSION:
      return DirectiveLocation.INPUT_OBJECT;
    case Kind.INPUT_VALUE_DEFINITION: {
      const parentNode = ancestors[ancestors.length - 3];
      return parentNode.kind === Kind.INPUT_OBJECT_TYPE_DEFINITION
        ? DirectiveLocation.INPUT_FIELD_DEFINITION
        : DirectiveLocation.ARGUMENT_DEFINITION;
    }
  }
}

function getDirectiveLocationForOperation(
  operation: OperationTypeNode,
): DirectiveLocationEnum {
  switch (operation) {
    case 'query':
      return DirectiveLocation.QUERY;
    case 'mutation':
      return DirectiveLocation.MUTATION;
    case 'subscription':
      return DirectiveLocation.SUBSCRIPTION;
  }

  // Not reachable. All possible types have been considered.
  invariant(false, 'Unexpected operation: ' + inspect((operation: empty)));
}