-- Copyright 2016 Google Inc. All Rights Reserved.
--
-- Use of this source code is governed by a BSD-style
-- license that can be found in the LICENSE file or at
-- https://developers.google.com/open-source/licenses/bsd

-- | Helper functions to generate proto files as part of a @Setup.hs@ script.
--
-- These functions assume that the @proto-lens-protoc@ executable is on the
-- PATH, and throw an exception otherwise.  That executable will be installed
-- automatically as part of installing this package; in particular, it should
-- be enough to just list `proto-lens-protoc` in a user package's
-- `build-dependencies`.
--
-- See @README.md@ for instructions on how to use proto-lens with Cabal.
{-# LANGUAGE CPP #-}
module Data.ProtoLens.Setup
    ( defaultMainGeneratingProtos
    , defaultMainGeneratingSpecificProtos
    , generatingProtos
    , generatingSpecificProtos
    , generateProtosWithImports
    , generateProtos
    ) where

#if __GLASGOW_HASKELL__ < 709
import Data.Functor ((<$>))
#endif

import Control.Monad (filterM, forM_, when)
import qualified Distribution.InstalledPackageInfo as InstalledPackageInfo
import Distribution.PackageDescription
    ( PackageDescription(..)
    , benchmarkBuildInfo
    , buildInfo
    , extraSrcFiles
    , hsSourceDirs
    , libBuildInfo
    , testBuildInfo
    )
import Distribution.Simple.BuildPaths (autogenModulesDir)
import Distribution.Simple.InstallDirs (datadir)
import Distribution.Simple.LocalBuildInfo
    ( LocalBuildInfo(..)
    , absoluteInstallDirs
    , componentPackageDeps
    )
import Distribution.Simple.PackageIndex (lookupSourcePackageId)
import Distribution.Simple.Setup (fromFlag, copyDest, copyVerbosity)
import Distribution.Simple.Utils
    ( createDirectoryIfMissingVerbose
    , installOrdinaryFile
    , matchFileGlob
    )
import Distribution.Simple
    ( defaultMainWithHooks
    , simpleUserHooks
    , UserHooks(..)
    )
import Distribution.Verbosity (Verbosity)
import System.FilePath
    ( (</>)
    , equalFilePath
    , isRelative
    , makeRelative
    , takeExtension
    , takeDirectory
    )
import System.Directory
    ( createDirectoryIfMissing
    , doesDirectoryExist
    , findExecutable
    , removeDirectoryRecursive
    )
import System.Process (callProcess)

-- | This behaves the same as 'Distribution.Simple.defaultMain', but
-- auto-generates Haskell files from the .proto files listed in
-- the @.cabal@ file under @extra-source-files@ which are located under the
-- given root directory.
--
-- Writes the generated files to the autogen directory (@dist\/build\/autogen@
-- for Cabal, and @.stack-work\/dist\/...\/build\/autogen@ for stack).
--
-- Throws an exception if the @proto-lens-protoc@ executable is not on the PATH.
defaultMainGeneratingProtos
    :: FilePath -- ^ The root directory under which .proto files can be found.
    -> IO ()
defaultMainGeneratingProtos root
    = defaultMainWithHooks $ generatingProtos root simpleUserHooks

-- | This behaves the same as 'Distribution.Simple.defaultMain', but
-- auto-generates Haskell files from the .proto files listed. The given .proto
-- files should be under the given root directory.
--
-- Writes the generated files to the autogen directory (@dist\/build\/autogen@
-- for Cabal, and @.stack-work\/dist\/...\/build\/autogen@ for stack).
--
-- Throws an exception if the @proto-lens-protoc@ executable is not on the PATH.
defaultMainGeneratingSpecificProtos
    :: FilePath -- ^ The root directory under which .proto files can be found.
    -> (PackageDescription -> IO [FilePath])
    -- ^ A function to return a list of .proto files. Takes the Cabal package
    -- description as input. Non-absolute paths are treated as relative to the
    -- provided root directory.
    -> IO ()
defaultMainGeneratingSpecificProtos root getProtos
    = defaultMainWithHooks
    $ generatingSpecificProtos root getProtos simpleUserHooks

-- | Augment the given 'UserHooks' to auto-generate Haskell files from the
-- .proto files listed in the @.cabal@ file under @extra-source-files@ which
-- are located under the given root directory.
--
-- Writes the generated files to the autogen directory (@dist\/build\/autogen@
-- for Cabal, and @.stack-work\/dist\/...\/build\/autogen@ for stack).
--
-- Throws an exception if the @proto-lens-protoc@ executable is not on the PATH.
generatingProtos
    :: FilePath -- ^ The root directory under which .proto files can be found.
    -> UserHooks -> UserHooks
generatingProtos root = generatingSpecificProtos root getProtos
  where
    getProtos p = do
      -- Replicate Cabal's own logic for parsing file globs.
      files <- concat <$> mapM matchFileGlob (extraSrcFiles p)
      pure $ map (makeRelative root)
           $ filter (isSubdirectoryOf root)
           $ filter (\f -> takeExtension f == ".proto")
               files

-- | Augment the given 'UserHooks' to auto-generate Haskell files from the
-- .proto files returned by a function @getProtos@.
--
-- Writes the generated files to the autogen directory (@dist\/build\/autogen@
-- for Cabal, and @.stack-work\/dist\/...\/build\/autogen@ for stack).
--
-- Throws an exception if the @proto-lens-protoc@ executable is not on the PATH.
generatingSpecificProtos
    :: FilePath -- ^ The root directory under which .proto files can be found.
    -> (PackageDescription -> IO [FilePath])
    -- ^ A function to return a list of .proto files. Takes the Cabal package
    -- description as input. Non-absolute paths are treated as relative to the
    -- provided root directory.
    -> UserHooks -> UserHooks
generatingSpecificProtos root getProtos hooks = hooks
    { buildHook = \p l h f -> generate p l >> buildHook hooks p l h f
    , haddockHook = \p l h f -> generate p l >> haddockHook hooks p l h f
    , replHook = \p l h f args -> generate p l >> replHook hooks p l h f args
    , sDistHook = \p maybe_l h f -> case maybe_l of
            Nothing -> error "Can't run protoc; run 'cabal configure' first."
            Just l -> do
                        generate p l
                        sDistHook hooks (fudgePackageDesc l p) maybe_l h f
    , postCopy = \a flags pkg lbi -> do
                  let verb = fromFlag $ copyVerbosity flags
                  let destDir = datadir (absoluteInstallDirs pkg lbi
                                             $ fromFlag $ copyDest flags)
                              </> protoLensImportsPrefix
                  getProtos pkg >>= copyProtosToDataDir verb root destDir
                  postCopy hooks a flags pkg lbi
    }
  where
    generate p l = getProtos p >>= generateSources root l

-- | Generate Haskell source files for the given input .proto files.
generateSources :: FilePath -- ^ The root directory
                -> LocalBuildInfo
                -> [FilePath] -- ^ Proto files relative to the root directory.
                -> IO ()
generateSources root l files = do
    -- Collect import paths from build-depends of this package.
    importDirs <- filterM doesDirectoryExist
                     [ InstalledPackageInfo.dataDir info </> protoLensImportsPrefix
                     | (_, c, _) <- componentsConfigs l
                     , (_, i) <- componentPackageDeps c
                     , info <- lookupSourcePackageId (installedPkgs l) i
                     ]
    generateProtosWithImports (root : importDirs) (autogenModulesDir l)
                              -- Applying 'root </>' does nothing if the path is already
                              -- absolute.
                              (map (root </>) files)

-- | Copy each .proto file into the installed "data-dir" path,
-- so that it can be included by other packages that depend on this one.
copyProtosToDataDir :: Verbosity
                    -> FilePath -- ^ The root for source .proto files in this
                                -- package.
                    -> FilePath -- ^ The final location where .proto files should
                                -- be installed.
                    -> [FilePath] -- ^ .proto files relative to the root
                    -> IO ()
copyProtosToDataDir verb root destDir files = do
    -- Make the build more hermetic by clearing the output
    -- directory.
    exists <- doesDirectoryExist destDir
    when exists $ removeDirectoryRecursive destDir
    forM_ files $ \f -> do
        let srcFile = root </> f
        let destFile = destDir </> f
        createDirectoryIfMissingVerbose verb True
            (takeDirectory destFile)
        installOrdinaryFile verb srcFile destFile

-- | Imports are stored as $datadir/proto-lens-imports/**/*.proto.
protoLensImportsPrefix :: FilePath
protoLensImportsPrefix = "proto-lens-imports"

-- | Add the autogen directory to the hs-source-dirs of all the targets in the
-- .cabal file.  Used to fool 'sdist' by pointing it to the generated source
-- files.
fudgePackageDesc :: LocalBuildInfo -> PackageDescription -> PackageDescription
fudgePackageDesc lbi p = p
    { library =
        (\lib -> lib { libBuildInfo = fudgeBuildInfo (libBuildInfo lib) })
            <$> library p
    , executables =
        (\exe -> exe { buildInfo = fudgeBuildInfo (buildInfo exe) })
            <$> executables p
    , testSuites =
        (\test -> test { testBuildInfo = fudgeBuildInfo (testBuildInfo test) })
            <$> testSuites p
    , benchmarks =
        (\bench -> bench { benchmarkBuildInfo =
                              fudgeBuildInfo (benchmarkBuildInfo bench) })
            <$> benchmarks p
    }
  where
    fudgeBuildInfo bi =
        bi { hsSourceDirs = autogenModulesDir lbi : hsSourceDirs bi }

-- | Returns whether the @root@ is a parent folder of @f@.
isSubdirectoryOf :: FilePath -> FilePath -> Bool
isSubdirectoryOf root f
    = isRelative f
      -- Note: `makeRelative root f` returns `f` when f doesn't live under the
      -- root.
      && equalFilePath f (root </> makeRelative root f)

-- | Run the proto compiler to generate Haskell files from the given .proto files.
--
-- Writes the generated files to the autogen directory (@dist\/build\/autogen@
-- for Cabal, and @.stack-work\/dist\/...\/build\/autogen@ for stack).
--
-- Throws an exception if the @proto-lens-protoc@ executable is not on the PATH.
generateProtos
    :: FilePath -- ^ The root directory under which .proto files can be found.
    -> FilePath -- ^ The output directory for the generated Haskell files.
    -> [FilePath] -- ^ The .proto files to process.
    -> IO ()
generateProtos root = generateProtosWithImports [root]
--
-- | Run the proto compiler to generate Haskell files from the given .proto files.
--
-- Writes the generated files to the autogen directory (@dist\/build\/autogen@
-- for Cabal, and @.stack-work\/dist\/...\/build\/autogen@ for stack).
--
-- Throws an exception if the @proto-lens-protoc@ executable is not on the PATH.
generateProtosWithImports
    :: [FilePath] -- ^ Directories under which .proto files and/or files that
                  -- they import can be found.
    -> FilePath -- ^ The output directory for the generated Haskell files.
    -> [FilePath] -- ^ The .proto files to process.
    -> IO ()
generateProtosWithImports imports output files = do
    maybeProtoLensProtoc <- findExecutable "proto-lens-protoc"
    case maybeProtoLensProtoc of
        Nothing -> error "Couldn't find executable proto-lens-protoc."
        Just protoLensProtoc -> do
            createDirectoryIfMissing True output
            callProcess "protoc" $
                [ "--plugin=protoc-gen-haskell=" ++ protoLensProtoc
                , "--haskell_out=" ++ output
                ]
                ++ ["--proto_path=" ++ p | p <- imports]
                ++ files