path: root/Biz/Bild.hs

{-# LANGUAGE DeriveAnyClass #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE QuasiQuotes #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE TupleSections #-}
{-# LANGUAGE NoImplicitPrelude #-}

-- | A general purpose build tool.
--
-- : out bild
--
-- == Design constraints
--
--    * only input is one or more a namespaces. no subcommands, no packages
--
--    * no need to write specific build rules, one rule for hs, one for rs, one
--    for scm, and so on
--
--    * no need to distinguish between exe and lib, just have a single output,
--    or figure it out automatically
--
--    * never concerned with deployment/packaging - leave that to another tool
--      (scp? tar?)
--
--    * local dev builds should be preserved, while remote nix builds are used
--    for the final package
--
-- == Features
--
--    * namespace maps to filesystem
--
--        * no need for `bild -l` for listing available targets.
--          Use `ls` or `tree`
--
--        * you build namespaces, not files/modules/packages/etc
--
--    * namespace maps to language modules
--
--        * build settings can be set in the file comments
--
--    * pwd is always considered the the source directory,
--      no `src` vs `doc` etc.
--
--    * build methods automaticatly detected with file extensions
--
--    * flags modify the way to interact with the build, some ideas:
--
--        * -p = turn on profiling
--
--        * -o = optimize level
--
--    * the build is planned out with an analysis, which can be viewed
--      beforehand with `--json`. The analysis includes compiler flags, which
--      can be used in `repl` for testing compilation locally.
--
-- == Example Commands
--
-- > bild [opts] <target..>
--
-- The general scheme is to build the things described by the targets. A target
-- is a namespace. You can list as many as you want, but you must list at least
-- one. It could just be `:!bild %` in vim to build whatever you're working on,
-- or `bild **/*` to build everything, or `fd .hs -X bild` to build all Haskell
-- files.
--
-- Build outputs will go into the `_` directory in the root of the project.
--
-- > bild A/B.hs
--
-- This will build the file at ./A/B.hs, which translates to something like
-- `ghc --make A.B`.
--
-- == Build Metadata
--
-- Metadata is set in the comments with a special syntax. For system-level deps,
-- we list the deps in comments in the target file, like:
--
-- > -- : sys cmark
--
-- The name is used to lookup the package in `nixpkgs.pkgs.<name>`.
-- Language-level deps can automatically determined by passing parsed import
-- statements to a package database, eg `ghc-pkg find-module`.
--
-- The output executable is named with:
--
-- > -- : out my-program
--
-- or
--
-- > -- : out my-app.js
--
-- When multiple compilers are possible we use the @out@ extension to determine
-- target platform. If @out@ does not have an extension, each build type falls
-- back to a default, namely an executable binary.
--
-- This method of setting metadata in the module comments works pretty well,
-- and really only needs to be done in the entrypoint module anyway.
--
-- Local module deps are included by just giving the repo root to the underlying
-- compiler for the target, and the compiler does work of walking the source
-- tree.
module Biz.Bild where

import Alpha hiding (sym, (<.>))
import qualified Biz.Cli as Cli
import qualified Biz.Log as Log
import Biz.Namespace (Namespace (..))
import qualified Biz.Namespace as Namespace
import qualified Biz.Test as Test
import qualified Control.Concurrent.Async as Async
import qualified Data.Aeson as Aeson
import qualified Data.ByteString as BS
import qualified Data.ByteString.Char8 as Char8
import qualified Data.ByteString.Internal as BSI
import qualified Data.ByteString.Lazy as ByteString
import qualified Data.Char as Char
import Data.Conduit ((.|))
import qualified Data.Conduit as Conduit
import qualified Data.Conduit.List as Conduit
import qualified Data.Conduit.Process as Conduit
import qualified Data.Map as Map
import qualified Data.Set as Set
import qualified Data.String as String
import qualified Data.Text as Text
import qualified Data.Text.IO as Text.IO
import qualified System.Directory as Dir
import qualified System.Environment as Env
import qualified System.Exit as Exit
import System.FilePath (replaceExtension, (</>))
import qualified System.IO as IO
import System.IO.Unsafe (unsafePerformIO)
import qualified System.Process as Process
import qualified Text.Regex.Applicative as Regex

main :: IO ()
main = Cli.main <| Cli.Plan help move test_ pure
  where
    test_ =
      Test.group
        "Biz.Bild"
        [ Test.unit "can bild bild" <| do
            root <- Env.getEnv "BIZ_ROOT"
            path <- Dir.makeAbsolute "Biz/Bild.hs"
            case Namespace.fromPath root path of
              Nothing -> Test.assertFailure "can't find ns for bild"
              Just ns ->
                analyze mempty ns
                  +> build False False
                  +> \case
                    [Exit.ExitFailure _] ->
                      Test.assertFailure "can't bild bild"
                    _ ->
                      pure ()
        ]

move :: Cli.Arguments -> IO ()
move args = do
  root <- Env.getEnv "BIZ_ROOT"
  IO.hSetBuffering stdout IO.NoBuffering
    >> pure (Cli.getAllArgs args (Cli.argument "target"))
    /> filter (not <. Namespace.isCab)
    +> filterM Dir.doesFileExist
    +> traverse Dir.makeAbsolute
    /> map (Namespace.fromPath root)
    /> catMaybes
    +> foldM analyze mempty
    /> Map.filter (namespace .> isBuildableNs)
    +> printOrBuild
    +> exitSummary
  where
    printOrBuild :: Analysis -> IO [ExitCode]
    printOrBuild targets
      | args `Cli.has` Cli.longOption "json" =
        Log.wipe >> putJSON targets >> pure [Exit.ExitSuccess]
      | otherwise = do
        root <- Env.getEnv "BIZ_ROOT"
        createHier root
        build isTest isLoud targets
    isTest = args `Cli.has` Cli.longOption "test"
    isLoud = args `Cli.has` Cli.longOption "loud"
    putJSON = Aeson.encode .> ByteString.toStrict .> Char8.putStrLn

nixStore :: String
nixStore = "/nix/store/00000000000000000000000000000000-"

help :: Cli.Docopt
help =
  [Cli.docopt|
bild

Usage:
  bild test
  bild [options] <target>...

Options:
  --test      Run tests on a target after building
  --loud      Show all output from compiler
  --json      Print the build plan as JSON, don't build
  -h, --help  Print this info
|]

exitSummary :: [Exit.ExitCode] -> IO ()
exitSummary exits =
  if failures > 0
    then Exit.die <| show failures
    else Exit.exitSuccess
  where
    failures = length <| filter isFailure exits

type Dep = String

type Arg = String

data Out = Lib String | Bin String | None
  deriving (Show, Eq)

instance Aeson.ToJSON Out where
  toJSON =
    Aeson.String <. Text.pack <. \case
      Bin a -> a
      Lib a -> a
      None -> ""

data Compiler
  = Copy
  | Gcc
  | Ghc
  | Guile
  | NixBuild
  | Rustc
  | Sbcl
  deriving (Eq, Show, Generic)

compilerExe :: IsString a => Compiler -> a
compilerExe = \case
  Copy -> "cp"
  Gcc -> "gcc"
  Ghc -> "ghc"
  Guile -> "guild"
  NixBuild -> "nix-build"
  Rustc -> "rustc"
  Sbcl -> "sbcl"

instance Aeson.ToJSON Compiler where
  toJSON = Aeson.String <. compilerExe

instance ToNixFlag Compiler where
  toNixFlag = compilerExe

data Target = Target
  { -- | Output name
    out :: Out,
    -- | Output path (into cabdir)
    outPath :: FilePath,
    -- | Fully qualified namespace partitioned by '.'
    namespace :: Namespace,
    -- | Absolute path to file
    path :: FilePath,
    -- | Language-specific dependencies
    langdeps :: Set Dep,
    -- | System-level dependencies
    sysdeps :: Set Dep,
    -- | Which compiler should we use?
    compiler :: Compiler,
    -- | Where is this machine being built?
    builder :: Builder,
    -- | Flags and arguments passed to 'Compiler' when building
    compilerFlags :: [Text],
    -- | Wrapper script (if necessary)
    wrapper :: Maybe Text
  }
  deriving (Show, Generic, Aeson.ToJSON)

data Builder
  = -- | Local <user>
    Local Text
  | -- | Remote <user> <host>
    Remote Text Text
  deriving (Show, Generic)

instance Aeson.ToJSON Builder where
  toJSON (Local u) = Aeson.String u
  toJSON (Remote u host) = Aeson.String <| u <> "@" <> host

class ToNixFlag a where
  toNixFlag :: a -> String

instance ToNixFlag Builder where
  toNixFlag = \case
    Local _ -> ""
    Remote u h -> Text.unpack <| Text.concat ["ssh://", u, "@", h, "?ssh-key=/home/", u, "/.ssh/id_rsa"]

-- | We can't build everything yet...
isBuildableNs :: Namespace -> Bool
isBuildableNs = \case
  (Namespace _ Namespace.C) -> True
  (Namespace _ Namespace.Css) -> False
  (Namespace _ Namespace.Hs) -> True
  (Namespace _ Namespace.Json) -> False
  (Namespace _ Namespace.Keys) -> False
  (Namespace _ Namespace.Lisp) -> True
  (Namespace _ Namespace.Md) -> False
  (Namespace _ Namespace.None) -> False
  (Namespace _ Namespace.Py) -> False
  (Namespace _ Namespace.Sh) -> False
  (Namespace _ Namespace.Scm) -> True
  (Namespace _ Namespace.Rs) -> True
  (Namespace path Namespace.Nix)
    | path `elem` nixTargets -> True
    | otherwise -> False
  where
    nixTargets =
      [ ["Biz", "Pie"],
        ["Biz", "Que"],
        ["Biz", "Cloud"],
        ["Biz", "Dev"],
        ["Biz", "Dragons", "Analysis"]
      ]

-- | The default output directory. This is not IO because I don't want to
-- refactor all of my code right now, but it probably should be.
cab :: FilePath
cab =
  Env.lookupEnv "CABDIR"
    /> fromMaybe "_"
    |> unsafePerformIO

-- | Emulate the *nix hierarchy in the cabdir.
outToPath :: Out -> FilePath
outToPath = \case
  Bin o -> cab </> "bin" </> o
  Lib o -> cab </> "lib" </> o
  None -> mempty

intdir, nixdir, vardir :: FilePath
intdir = cab </> "int"
nixdir = cab </> "nix"
vardir = cab </> "var"

createHier :: String -> IO ()
createHier root =
  traverse_
    (Dir.createDirectoryIfMissing True)
    [ root </> (outToPath <| Bin ""),
      root </> (outToPath <| Lib ""),
      root </> intdir,
      root </> nixdir,
      root </> vardir
    ]

-- >>> removeVersion "array-0.5.4.0-DFLKGIjfsadi"
-- "array"
removeVersion :: String -> String
removeVersion = takeWhile (/= '.') .> butlast2
  where
    butlast2 s = take (length s - 2) s

type Analysis = Map Namespace Target

analyze :: Analysis -> Namespace -> IO Analysis
analyze hmap ns = case Map.lookup ns hmap of
  Nothing -> do
    mTarget <- analyzeOne ns
    pure <| maybe hmap (\t -> Map.insert ns t hmap) mTarget
  Just _ -> pure hmap
  where
    analyzeOne :: Namespace -> IO (Maybe Target)
    analyzeOne namespace@(Namespace _ ext) = do
      let path = Namespace.toPath namespace
      content <-
        withFile path ReadMode <| \h ->
          IO.hSetEncoding h IO.utf8_bom
            >> Text.IO.hGetContents h
      let contentLines = Text.lines content
      root <- Env.getEnv "BIZ_ROOT"
      absPath <- Dir.makeAbsolute path
      user <- Env.getEnv "USER" /> Text.pack
      host <- Env.lookupEnv "HOSTNAME" /> fromMaybe "interactive" /> Text.pack
      Log.info ["bild", "analyze", str path]
      case ext of
        -- basically we don't support building these
        Namespace.Css -> pure Nothing
        Namespace.Json -> pure Nothing
        Namespace.Keys -> pure Nothing
        Namespace.Md -> pure Nothing
        Namespace.None -> pure Nothing
        Namespace.Py -> pure Nothing
        Namespace.Sh -> pure Nothing
        Namespace.C -> do
          let out = detectOut (metaOut "//" <|> metaLib "//") contentLines
          let args = detectMeta (metaArg "//") contentLines
          let langdeps = detectMeta (metaDep "//") contentLines
          langdepFlags <-
            if null langdeps
              then pure []
              else
                Process.readProcess
                  "pkg-config"
                  ("--cflags" : Set.toList langdeps)
                  ""
                  /> Text.pack
                  /> Text.words

          let sysdeps = detectMeta (metaSys "//") contentLines
          sysdepFlags <-
            if null sysdeps
              then pure []
              else
                Process.readProcess
                  "pkg-config"
                  ("--libs" : Set.toList sysdeps)
                  ""
                  /> Text.pack
                  /> Text.words
          Target
            { langdeps = Set.empty, -- c has no lang deps...?
              wrapper = Nothing,
              compiler = Gcc,
              builder = Local <| user,
              compilerFlags =
                concat
                  [ [o, dir, Text.pack absPath]
                      ++ langdepFlags
                      ++ sysdepFlags
                      ++ (map Text.pack <| Set.toList args)
                    | let outable = out /= None,
                      o <- outable ?: (["-o"], []),
                      dir <- outable ?: ([Text.pack <| root </> outToPath out], [])
                  ],
              outPath = outToPath out,
              ..
            }
            |> Just
            |> pure
        Namespace.Hs -> do
          langdeps <- detectHaskellImports contentLines
          let out = detectOut (metaOut "--") contentLines
          Just
            </ pure
              Target
                { builder = Local <| user,
                  wrapper = Nothing,
                  compiler = Ghc,
                  compilerFlags =
                    map
                      Text.pack
                      [ "-Werror",
                        "-i" <> root,
                        "-odir",
                        root </> intdir,
                        "-hidir",
                        root </> intdir,
                        "--make",
                        path
                      ]
                      ++ (out /= None)
                      ?: ( map
                             Text.pack
                             [ "-main-is",
                               Namespace.toHaskellModule namespace,
                               "-o",
                               root </> outToPath out
                             ],
                           []
                         ),
                  sysdeps = detectMeta (metaSys "--") contentLines,
                  outPath = outToPath out,
                  ..
                }
        Namespace.Lisp -> do
          let out = detectOut (metaOut ";;") contentLines
          langdeps <- detectLispImports contentLines
          Just
            </ pure
              Target
                { sysdeps = Set.empty,
                  wrapper = Nothing,
                  compiler = Sbcl,
                  compilerFlags =
                    map
                      Text.pack
                      [ "--eval",
                        "(require :asdf)",
                        "--load",
                        path,
                        "--eval",
                        "(sb-ext:save-lisp-and-die #p\"" <> (root </> outToPath out) <> "\" :toplevel #'main :executable t)"
                      ],
                  builder = Local <| user,
                  outPath = outToPath out,
                  ..
                }
        Namespace.Nix -> do
          let builder =
                (host == "lithium")
                  ?: ( Local user,
                       Remote user "dev.simatime.com"
                     )
          Just
            </ pure
              Target
                { langdeps = Set.empty,
                  wrapper = Nothing,
                  sysdeps = Set.empty,
                  compiler = NixBuild,
                  compilerFlags =
                    map
                      Text.pack
                      [ path,
                        "--out-link",
                        root </> nixdir </> Namespace.toPath namespace,
                        "--builders",
                        toNixFlag builder
                      ],
                  out = None,
                  outPath = outToPath None,
                  ..
                }
        Namespace.Scm -> do
          let out = detectOut (metaOut ";;") contentLines
          Just
            </ pure
              Target
                { langdeps = Set.empty,
                  sysdeps = Set.empty,
                  compiler = Guile,
                  compilerFlags =
                    map
                      Text.pack
                      [ "compile",
                        "--r7rs",
                        "--load-path=" ++ root,
                        "--output=" ++ root </> intdir </> replaceExtension path ".scm.go",
                        path
                      ],
                  builder = Local user,
                  outPath = outToPath out,
                  wrapper =
                    Just <| Text.pack
                      <| joinWith
                        "\n"
                        [ "#!/usr/bin/env bash",
                          "guile -C \""
                            <> root </> intdir
                            <> "\" -e main "
                            <> "-s "
                            <> Namespace.toPath namespace
                            <> " \"$@\""
                        ],
                  ..
                }
        Namespace.Rs -> do
          let out = detectOut (metaOut "//") contentLines
          Just
            </ pure
              Target
                { langdeps = Set.empty,
                  wrapper = Nothing,
                  sysdeps = Set.empty,
                  compiler = Rustc,
                  compilerFlags = map Text.pack [path, "-o", root </> outToPath out],
                  builder = Local user,
                  outPath = outToPath out,
                  ..
                }
    detectHaskellImports :: [Text] -> IO (Set Dep)
    detectHaskellImports contentLines = do
      let imports =
            contentLines
              /> Text.unpack
              /> Regex.match haskellImports
              |> catMaybes
      pkgs <- foldM ghcPkgFindModule Set.empty imports
      root <- Env.getEnv "BIZ_ROOT"
      transitivePkgs <-
        imports
          |> map (Namespace.fromHaskellModule .> Namespace.toPath)
          |> traverse Dir.makeAbsolute
          +> filterM Dir.doesFileExist
          /> map (Namespace.fromPath root)
          /> catMaybes
          -- this is still an inefficiency, because this recurses before the
          -- hmap is updated by the fold, transitive imports will be
          -- re-visited. you can see this with `TERM=dumb bild`. to fix this i
          -- need shared state instead of a fold, or figure out how to do a
          -- breadth-first search instead of depth-first.
          +> foldM analyze hmap
          /> Map.elems
          /> map langdeps
          /> mconcat
      pure <| pkgs <> transitivePkgs
    detectLispImports contentLines = do
      let requires = contentLines /> Text.unpack /> Regex.match lispRequires |> catMaybes
      pure <| Set.fromList requires
    detectOut m cl =
      cl
        /> Text.unpack
        /> Regex.match m
        |> catMaybes
        |> head
        |> fromMaybe None
    detectMeta m cl =
      cl
        /> Text.unpack
        /> Regex.match m
        |> catMaybes
        |> Set.fromList

ghcPkgFindModule :: Set String -> String -> IO (Set String)
ghcPkgFindModule acc m = do
  packageDb <- Env.getEnv "GHC_PACKAGE_PATH"
  Process.readProcess
    "ghc-pkg"
    ["--package-db", packageDb, "--names-only", "--simple-output", "find-module", m]
    ""
    /> String.lines
    /> Set.fromList
    /> Set.union acc

isFailure :: Exit.ExitCode -> Bool
isFailure (Exit.ExitFailure _) = True
isFailure Exit.ExitSuccess = False

isSuccess :: Exit.ExitCode -> Bool
isSuccess Exit.ExitSuccess = True
isSuccess _ = False

test :: Bool -> Target -> IO Exit.ExitCode
test loud Target {..} = case compiler of
  Ghc -> do
    root <- Env.getEnv "BIZ_ROOT"
    run
      <| Proc
        { loud = loud,
          cmd = root </> outToPath out,
          args = ["test"],
          ns = namespace,
          onFailure = Log.fail ["test", nschunk namespace] >> Log.br,
          onSuccess = Log.pass ["test", nschunk namespace] >> Log.br
        }
  _ ->
    Log.warn ["test", nschunk namespace, "unavailable"]
      >> Log.br
      >> pure (Exit.ExitFailure 1)

build :: Bool -> Bool -> Analysis -> IO [Exit.ExitCode]
build andTest loud analysis = do
  root <- Env.getEnv "BIZ_ROOT"
  forM (Map.elems analysis) <| \target@Target {..} -> do
    case compiler of
      Gcc ->
        Log.info ["bild", label, "gcc", nschunk namespace]
          >> proc loud namespace compiler compilerFlags
        where
          label = case out of
            Bin _ -> "bin"
            _ -> "lib"
      Ghc -> case out of
        None -> pure Exit.ExitSuccess
        Bin _ -> do
          Log.info ["bild", "dev", "ghc-exe", nschunk namespace]
          exitcode <- proc loud namespace compiler compilerFlags
          if andTest && isSuccess exitcode
            then test loud target
            else pure exitcode
        Lib _ -> do
          Log.info ["bild", "dev", "ghc-lib", nschunk namespace]
          proc loud namespace compiler compilerFlags
      Guile -> do
        Log.info ["bild", "dev", "guile", nschunk namespace]
        _ <- proc loud namespace compiler compilerFlags
        case wrapper of
          Nothing -> pure Exit.ExitSuccess
          Just content -> do
            writeFile (root </> outToPath out) content
            p <- Dir.getPermissions <| root </> outToPath out
            Dir.setPermissions (root </> outToPath out) (Dir.setOwnerExecutable True p)
            pure Exit.ExitSuccess
      NixBuild -> do
        Log.info ["bild", "nix", toLog builder, nschunk namespace]
        proc loud namespace compiler compilerFlags
        where
          toLog (Local u) = u
          toLog (Remote u h) = u <> "@" <> h
      Copy -> do
        Log.warn ["bild", "copy", "not implemented yet", nschunk namespace]
        pure Exit.ExitSuccess
      Rustc -> do
        Log.info ["bild", "dev", "rust", nschunk namespace]
        proc loud namespace compiler compilerFlags
      Sbcl -> do
        Log.info ["bild", "dev", "lisp", nschunk namespace]
        proc loud namespace compiler compilerFlags

data Proc = Proc
  { loud :: Bool,
    cmd :: String,
    args :: [String],
    ns :: Namespace,
    onFailure :: IO (),
    onSuccess :: IO ()
  }

-- | Run a subprocess, streaming output if --loud is set.
run :: Proc -> IO Exit.ExitCode
run Proc {..} =
  Conduit.proc cmd args |> Conduit.streamingProcess
    +> \(Conduit.UseProvidedHandle, stdin_, stderr_, hdl) ->
      loud ?: (verboseLog stdin_ stderr_ hdl, shortLog stdin_ stderr_ hdl)
        +> \case
          Exit.ExitFailure n -> puts stderr_ >> onFailure >> pure (Exit.ExitFailure n)
          Exit.ExitSuccess -> onSuccess >> pure Exit.ExitSuccess
  where
    verboseLog stdin_ stderr_ hdl =
      Async.runConcurrently
        <| Async.Concurrently (puts stdin_)
        *> Async.Concurrently (puts stderr_)
        *> Async.Concurrently (Conduit.waitForStreamingProcess hdl)
    shortLog stdin_ stderr_ hdl =
      Async.runConcurrently
        <| Async.Concurrently (logs ns stdin_)
        *> Async.Concurrently (logs ns stderr_)
        *> Async.Concurrently (Conduit.waitForStreamingProcess hdl)

-- | Helper for running a standard bild subprocess.
proc :: ToNixFlag a => Bool -> Namespace -> a -> [Text] -> IO Exit.ExitCode
proc loud namespace cmd args =
  run
    <| Proc
      { loud = loud,
        ns = namespace,
        cmd = toNixFlag cmd,
        args = map Text.unpack args,
        onFailure = Log.fail ["bild", nschunk namespace] >> Log.br,
        onSuccess = Log.good ["bild", nschunk namespace] >> Log.br
      }

-- | Helper for printing during a subprocess
puts :: Conduit.ConduitM () ByteString IO () -> IO ()
puts src = Conduit.runConduit <| src .| Conduit.mapM_ putStr

-- | Like 'puts' but logs the output via 'Biz.Log'.
logs :: Namespace -> Conduit.ConduitM () ByteString IO () -> IO ()
logs ns src =
  Conduit.runConduit
    <| src
      .| Conduit.mapM_
        ( BS.filter (/= BSI.c2w '\n')
            .> (\t -> Log.fmt ["info", "bild", nschunk ns, decodeUtf8 t])
            .> Text.take 77
            .> (<> "...\r")
            .> putStr
        )

nschunk :: Namespace -> Text
nschunk = Namespace.toPath .> Text.pack

metaDep :: [Char] -> Regex.RE Char Dep
metaDep comment =
  Regex.string (comment ++ " : dep ")
    *> Regex.many (Regex.psym (not <. Char.isSpace))

metaSys :: [Char] -> Regex.RE Char Dep
metaSys comment =
  Regex.string (comment ++ " : sys ")
    *> Regex.many (Regex.psym (not <. Char.isSpace))

metaOut :: [Char] -> Regex.RE Char Out
metaOut comment =
  Regex.string (comment ++ " : out ")
    *> Regex.many (Regex.psym (/= ' '))
    /> Bin

metaLib :: [Char] -> Regex.RE Char Out
metaLib comment =
  Regex.string (comment ++ " : lib ")
    *> Regex.many (Regex.psym (/= ' '))
    /> Lib

metaArg :: [Char] -> Regex.RE Char Arg
metaArg comment =
  Regex.string (comment ++ " : arg ")
    *> Regex.many Regex.anySym

haskellImports :: Regex.RE Char String
haskellImports =
  Regex.string "import"
    *> Regex.some (Regex.psym Char.isSpace)
    *> Regex.many (Regex.psym Char.isLower)
    *> Regex.many (Regex.psym Char.isSpace)
    *> Regex.some (Regex.psym isModuleChar)
    <* Regex.many Regex.anySym

isModuleChar :: Char -> Bool
isModuleChar c =
  elem c <| concat [['A' .. 'Z'], ['a' .. 'z'], ['.', '_'], ['0' .. '9']]

-- Matches on `(require :package)` forms and returns `package`. The `require`
-- function is technically deprecated in Common Lisp, but no new spec has been
-- published with a replacement, and I don't wanna use asdf, so this is what we
-- use for Lisp imports.
lispRequires :: Regex.RE Char String
lispRequires =
  Regex.string "(require"
    *> Regex.some (Regex.psym Char.isSpace)
    *> Regex.many (Regex.psym isQuote)
    *> Regex.many (Regex.psym isModuleChar)
    <* Regex.many (Regex.psym (== ')'))
  where
    isQuote :: Char -> Bool
    isQuote c = c `elem` ['\'', ':']