type Did<TMethod extends string = string> = `did:${TMethod}:${string}`;

type Nsid = `${string}.${string}.${string}`;

type RecordKey = string;

const DID_RE = /^did:([a-z]+):([a-zA-Z0-9._:%\-]*[a-zA-Z0-9._\-])$/;

const NSID_RE =
  /^[a-zA-Z](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)+(?:\.[a-zA-Z](?:[a-zA-Z0-9]{0,62})?)$/;

const RECORD_KEY_RE = /^(?!\.{1,2}$)[a-zA-Z0-9_~.:-]{1,512}$/;

export const ATURI_RE =
  /^at:\/\/([a-zA-Z0-9._:%-]+)(?:\/([a-zA-Z0-9-.]+)(?:\/([a-zA-Z0-9._~:@!$&%')(*+,;=-]+))?)?(?:#(\/[a-zA-Z0-9._~:@!$&%')(*+,;=\-[\]/\\]*))?$/;

const isDid = (input: unknown): input is Did => {
  return (
    typeof input === "string" && input.length >= 7 && input.length <= 2048 && DID_RE.test(input)
  );
};

const isNsid = (input: unknown): input is Nsid => {
  return (
    typeof input === "string" && input.length >= 5 && input.length <= 317 && NSID_RE.test(input)
  );
};

const isRecordKey = (input: unknown): input is RecordKey => {
  return (
    typeof input === "string" &&
    input.length >= 1 &&
    input.length <= 512 &&
    RECORD_KEY_RE.test(input)
  );
};

export interface AddressedAtUri {
  repo: Did;
  collection: Nsid;
  rkey: string;
  fragment: string | undefined;
}

export const parseAddressedAtUri = (str: string): AddressedAtUri => {
  const match = ATURI_RE.exec(str);
  assert(match !== null, `invalid addressed-at-uri: ${str}`);

  const [, r, c, k, f] = match;
  assert(isDid(r), `invalid repo in addressed-at-uri: ${r}`);
  assert(isNsid(c), `invalid collection in addressed-at-uri: ${c}`);
  assert(isRecordKey(k), `invalid rkey in addressed-at-uri: ${k}`);

  return {
    repo: r,
    collection: c,
    rkey: k,
    fragment: f,
  };
};

function assert(condition: boolean, message: string): asserts condition {
  if (!condition) {
    throw new Error(message);
  }
}