module Main where

import Prelude

import Effect (Effect)
import Effect.Aff (Aff, launchAff)
import Effect.Class (liftEffect)
import Effect.Console (log)
import Fetch (fetch)
import Data.Base64 (decodeBase64, fromString)
import Data.Either (Either, note)
import Data.Maybe (Maybe(..))
import Data.ArrayBuffer.Builder (execPut, putInt32be)
import Data.ArrayBuffer.Types (ArrayBuffer)
import Data.Foldable (traverse_)
import Data.String (drop, indexOf', indexOf, splitAt)
import Data.String.Pattern (Pattern(..))

import Crypto.Subtle.Constants.AES (aesGCM, t128)
import Crypto.Subtle.Encrypt (aesGCM, decrypt) as Alg
import Crypto.Subtle.Key.Import (aes)
import Crypto.Subtle.Key.Import (importKey) as SC
import Crypto.Subtle.Key.Types (CryptoKey, decrypt, raw)

nonceE :: Effect ArrayBuffer
nonceE = execPut $ traverse_ putInt32be [0xd0, 0xc3, 0x75, 0x56, 0x58, 0xc1, 0x7e, 0x5f, 0xd6, 0xcc, 0xb6, 0x76]

data AviaryError
    = MalformedKey
    | MalformedUrl
    | DecryptFailed

instance showAviaryError :: Show AviaryError where
    show MalformedKey = "Malformed key!!"
    show MalformedUrl = "Malformed url!!"
    show DecryptFailed = "Either the data provided by the server was bad, or valid but incorrect key.  Expiration likely."

type UrlInfo =
    { server :: String
    , fileId :: String
    , key :: String
    }

parseUrl :: String -> Either AviaryError UrlInfo
parseUrl url = note MalformedUrl do
    slashIndex <- indexOf' (Pattern "/") 8 url
    let { after, before: server } = splitAt (1 + slashIndex) url
    poundIndex <- indexOf (Pattern "#") after
    let { after: key, before: fileId } = splitAt poundIndex after
    Just { server, fileId, key: drop 1 key }

decodeKey :: String -> Either AviaryError ArrayBuffer
decodeKey key = note MalformedKey $ decodeBase64 <$> fromString key

importKey :: ArrayBuffer -> Aff CryptoKey
importKey key =
    SC.importKey raw key (aes aesGCM) false [decrypt]

decryptBlob :: CryptoKey -> ArrayBuffer -> ArrayBuffer -> Aff ArrayBuffer
decryptBlob key cyphertext nonce =
    -- nonce <- makeAff (\_ -> nonceE)
    Alg.decrypt (Alg.aesGCM nonce Nothing (Just t128)) key cyphertext

main_aff :: Aff Unit
main_aff = do
    { status, text } <- fetch "https://envs.sh/Q_V.txt" {}
    responseText <- text
    liftEffect $ log responseText

main :: Effect Unit
main = launchAff main_aff $> unit