import { number, option, ord, readonlyArray } from "fp-ts";
import { flow, pipe } from "fp-ts/lib/function.js";

const RE_URL =
  /(http|https):\/\/([\w_-]+(?:(?:\.[\w_-]+)+))([\w.,@?^=%&:\/~+#-]*[\w@?^=%&\/~+#-])/;

// getMessageUrl :: Message -> Option<string>
const getMessageUrl = (msg) => option.fromNullable(RE_URL.exec(msg.text)?.[0]);

// getMessageEntities :: Message -> ReadonlyArray<MessageEntity>
const getMessageEntities = (msg) => msg.entities ?? readonlyArray.empty;

// isTextLink :: MessageEntity -> boolean
const isTextLink = (msgEntity) => msgEntity.type === "text_link";

const ordStringLength = pipe(
  number.Ord,
  ord.contramap((s) => s.length),
);

// getTextLink :: Message -> Option<string>
const getTextLink = flow(
  getMessageEntities,
  readonlyArray.filterMap(
    flow(option.fromPredicate(isTextLink), option.map((link) => link.url)),
  ),
  readonlyArray.sort(ordStringLength),
  readonlyArray.last,
);

export const extractMessageLink = (msg) =>
  pipe(
    getTextLink(msg),
    option.orElse(() => getMessageUrl(msg)),
  );