import {
  GraphQLInputType,
  GraphQLNonNull,
  GraphQLOutputType,
  isListType,
  isNamedType,
  isNonNullType,
  isScalarType,
} from 'graphql';

const render = (
  type: GraphQLOutputType | GraphQLInputType,
  nonNull: boolean,
  root: boolean,
  undefinableValues: boolean,
  undefinableFields: boolean,
  wrap: (x: string) => string = (x) => x,
): string => {
  if (root) {
    if (undefinableFields) {
      if (isNonNullType(type)) {
        return `: ${render(type.ofType, true, false, undefinableValues, undefinableFields, wrap)}`;
      } else {
        const rendered = render(type, true, false, undefinableValues, undefinableFields, wrap);
        return undefinableValues ? `?: ${rendered}` : `?: (${rendered} | null)`;
      }
    } else {
      return `: ${render(type, false, false, undefinableValues, undefinableFields, wrap)}`;
    }
  }

  if (isNamedType(type)) {
    let typeName = type.name;

    // if is a scalar use the scalar interface to not expose reserved words
    if (isScalarType(type)) {
      typeName = `Scalars['${typeName}']`;
    }

    const typing = wrap(typeName);

    if (undefinableValues) {
      return nonNull ? typing : `(${typing} | undefined)`;
    } else {
      return nonNull ? typing : `(${typing} | null)`;
    }
  }

  if (isListType(type)) {
    const typing = `${render(type.ofType, false, false, undefinableValues, undefinableFields, wrap)}[]`;

    if (undefinableValues) {
      return nonNull ? typing : `(${typing} | undefined)`;
    } else {
      return nonNull ? typing : `(${typing} | null)`;
    }
  }

  return render((type as GraphQLNonNull<any>).ofType, true, false, undefinableValues, undefinableFields, wrap);
};

export function renderTyping(
  type: GraphQLOutputType | GraphQLInputType,
  undefinableValues: boolean,
  undefinableFields: boolean,
  root = true,
  wrap: any = undefined,
) {
  return render(type, false, root, undefinableValues, undefinableFields, wrap);
}