import * as Either from "@effect/data/Either"
import type * as Encoding from "@effect/data/Encoding"
import * as Base64 from "@effect/data/internal/Encoding/Base64"
import { DecodeException } from "@effect/data/internal/Encoding/Common"

/** @internal */
export const encode = (data: Uint8Array) =>
  Base64.encode(data).replace(/=/g, "").replace(/\+/g, "-").replace(/\//g, "_")

/** @internal */
export const decode = (str: string): Either.Either<Encoding.DecodeException, Uint8Array> => {
  const length = str.length
  if (length % 4 === 1) {
    return Either.left(
      DecodeException(str, `Length should be a multiple of 4, but is ${length}`)
    )
  }

  if (!/^[-_A-Z0-9]*?={0,2}$/i.test(str)) {
    return Either.left(DecodeException(str, "Invalid input"))
  }

  // Some variants allow or require omitting the padding '=' signs
  let sanitized = length % 4 === 2 ? `${str}==` : length % 4 === 3 ? `${str}=` : str
  sanitized = sanitized.replace(/-/g, "+").replace(/_/g, "/")

  return Base64.decode(sanitized)
}