-- | Copyright: (c) 2020 berberman
-- SPDX-License-Identifier: MIT
-- Maintainer: berberman <1793913507@qq.com>
-- Stability: experimental
-- Portability: portable
-- This module provides functions operating with 'HackageDB' and 'GenericPackageDescription'.
module Distribution.ArchHs.Hackage
  ( lookupHackagePath,
    loadHackageDB,
    insertDB,
    parseCabalFile,
    getLatestCabal,
    getCabal,
    getPackageFlag,
    traverseHackage,
  )
where

import Control.Applicative (Alternative ((<|>)))
import qualified Data.ByteString as BS
import qualified Data.Map as Map
import Data.Maybe (fromJust)
import Distribution.ArchHs.Types
import Distribution.ArchHs.Utils (getPkgName, getPkgVersion)
import Distribution.Hackage.DB (HackageDB, VersionData (VersionData, cabalFile), readTarball)
import Distribution.PackageDescription.Parsec (parseGenericPackageDescriptionMaybe)
import Distribution.Types.Flag (Flag)
import Distribution.Types.GenericPackageDescription (GenericPackageDescription, genPackageFlags, packageDescription)
import Distribution.Types.PackageName (PackageName)
import Distribution.Version (Version, nullVersion)
import System.Directory (findFile, getHomeDirectory, listDirectory)
import System.FilePath ((</>))

-- | Look up hackage tarball path from @~/.cabal@.
-- Arbitrary hackage mirror is potential to be selected.
-- Preferred to @01-index.tar@, whereas fallback to @00-index.tar@.
lookupHackagePath :: IO FilePath
lookupHackagePath = do
  home <- (\d -> d </> ".cabal" </> "packages") <$> getHomeDirectory
  subs <- fmap (home </>) <$> listDirectory home
  legacy <- findFile subs "00-index.tar"
  new <- findFile subs "01-index.tar"
  case new <|> legacy of
    Just x -> return x
    Nothing -> fail $ "Unable to find hackage index tarball from " <> show subs

-- | Read and parse hackage index tarball.
loadHackageDB :: FilePath -> IO HackageDB
loadHackageDB = readTarball Nothing

-- | Insert a 'GenericPackageDescription' into 'HackageDB'.
insertDB :: GenericPackageDescription -> HackageDB -> HackageDB
insertDB cabal db = Map.insert name packageData db
  where
    name = getPkgName $ packageDescription cabal
    version = getPkgVersion $ packageDescription cabal
    versionData = VersionData cabal $ Map.empty
    packageData = Map.singleton version versionData

-- | Read and parse @.cabal@ file.
parseCabalFile :: FilePath -> IO GenericPackageDescription
parseCabalFile path = do
  bs <- BS.readFile path
  case parseGenericPackageDescriptionMaybe bs of
    Just x -> return x
    _ -> fail $ "Failed to parse .cabal from " <> path

-- | Get the latest 'GenericPackageDescription'.
getLatestCabal :: Members [HackageEnv, WithMyErr] r => PackageName -> Sem r GenericPackageDescription
getLatestCabal name = do
  db <- ask @HackageDB
  case Map.lookup name db of
    (Just m) -> case Map.lookupMax m of
      Just (_, vdata) -> return $ vdata & cabalFile
      Nothing -> throw $ VersionError name nullVersion
    Nothing -> throw $ PkgNotFound name

-- | Get 'GenericPackageDescription' with a specific version.
getCabal :: Members [HackageEnv, WithMyErr] r => PackageName -> Version -> Sem r GenericPackageDescription
getCabal name version = do
  db <- ask @HackageDB
  case Map.lookup name db of
    (Just m) -> case Map.lookup version m of
      Just vdata -> return $ vdata & cabalFile
      Nothing -> throw $ VersionError name version
    Nothing -> throw $ PkgNotFound name

-- | Get flags of a package.
getPackageFlag :: Members [HackageEnv, WithMyErr] r => PackageName -> Sem r [Flag]
getPackageFlag name = do
  cabal <- getLatestCabal name
  return $ cabal & genPackageFlags

-- | Traverse hackage packages.
traverseHackage :: (Member HackageEnv r, Applicative f) => ((PackageName, GenericPackageDescription) -> f b) -> Sem r (f [b])
traverseHackage f = do
  db <- ask @HackageDB
  let x =
        Map.toList
          . Map.map (cabalFile . (^. _2) . fromJust)
          . Map.filter (/= Nothing)
          $ Map.map Map.lookupMax db
  return $ traverse f x