import { MutationSegment } from './gql-segments/types';

export const MAX_UNIQUE_ID = 10000000000;

function uniqueId(): string {
  return Math.floor(Math.random() * MAX_UNIQUE_ID).toString();
}

function segment(startMatch: RegExp, endMatch: RegExp, seg: string): string {
  const startIndex = seg.search(startMatch);
  const endIndex = seg.search(endMatch);
  return seg.substring(startIndex + startMatch.toString().length - 2, endIndex);
}

export default function generateMutationGql(
  fullGql: string,
  mutationName: string,
): MutationSegment {
  const mutationUniqueId = `${mutationName}_${uniqueId()}`;

  const mutationFunctionName = segment(
    /compass {\n/,
    /\(input/,
    fullGql,
  ).trim();

  const mutation = `${mutationUniqueId}: ${mutationFunctionName}(input: $${mutationUniqueId}) {
      success
      errors {
        message
      }
    }
  `;
  const inputType = segment(/input: /, /\) \{/, fullGql).replace('\n', '');

  return {
    mutationGql: mutation,
    params: [`$${mutationUniqueId}: ${inputType}`],
    inputId: mutationUniqueId,
  };
}