// @flow strict

import { GraphQLError } from '../../error/GraphQLError';
import { type ASTVisitor } from '../../language/visitor';
import { isEnumType } from '../../type/definition';

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

/**
 * Unique enum value names
 *
 * A GraphQL enum type is only valid if all its values are uniquely named.
 */
export function UniqueEnumValueNamesRule(
  context: SDLValidationContext,
): ASTVisitor {
  const schema = context.getSchema();
  const existingTypeMap = schema ? schema.getTypeMap() : Object.create(null);
  const knownValueNames = Object.create(null);

  return {
    EnumTypeDefinition: checkValueUniqueness,
    EnumTypeExtension: checkValueUniqueness,
  };

  function checkValueUniqueness(node) {
    const typeName = node.name.value;

    if (!knownValueNames[typeName]) {
      knownValueNames[typeName] = Object.create(null);
    }

    /* istanbul ignore next (See https://github.com/graphql/graphql-js/issues/2203) */
    const valueNodes = node.values ?? [];
    const valueNames = knownValueNames[typeName];

    for (const valueDef of valueNodes) {
      const valueName = valueDef.name.value;

      const existingType = existingTypeMap[typeName];
      if (isEnumType(existingType) && existingType.getValue(valueName)) {
        context.reportError(
          new GraphQLError(
            `Enum value "${typeName}.${valueName}" already exists in the schema. It cannot also be defined in this type extension.`,
            valueDef.name,
          ),
        );
      } else if (valueNames[valueName]) {
        context.reportError(
          new GraphQLError(
            `Enum value "${typeName}.${valueName}" can only be defined once.`,
            [valueNames[valueName], valueDef.name],
          ),
        );
      } else {
        valueNames[valueName] = valueDef.name;
      }
    }

    return false;
  }
}