const { Kind, GraphQLScalarType } = require('graphql')

const uuidRegex = /^[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i
const nilUUID = '00000000-0000-0000-0000-000000000000'

function isUUID (value) {
  return uuidRegex.test(value) || nilUUID === value
}

module.exports = new GraphQLScalarType({
  name: 'UUID',
  description: 'The `UUID` scalar type represents UUID values as specified by [RFC 4122](https://datatracker.ietf.org/doc/html/rfc4122).',
  serialize: (value) => {
    if (!isUUID(value)) {
      throw new TypeError(`UUID cannot represent non-UUID value: ${value}`)
    }

    return value.toLowerCase()
  },
  parseValue: (value) => {
    if (!isUUID(value)) {
      throw new TypeError(`UUID cannot represent non-UUID value: ${value}`)
    }

    return value.toLowerCase()
  },
  parseLiteral: (ast) => {
    if (ast.kind === Kind.STRING) {
      if (isUUID(ast.value)) {
        return ast.value
      }
    }

    return undefined
  }
})