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

-- | A specific-purpose build tool.
--
-- : out bild
--
-- == Design constraints
--
--    * The only input is one or more a namespaces. No subcommands, no packages,
--      no targets.
--
--    * 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 because we only build
--      exes; 'libs' are just source files in the tree.
--
--    * Never concerned with deployment/packaging - leave that to another tool
--      (scp? tar?)
--
--    * Ability to do 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, or special 'bild'
--          args
--
--    * pwd is always considered the the source directory,
--      no `src` vs `doc` etc.
--
--    * Build rules automaticatly detected from 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.
--
--    * (WIP) Nix is used by default to build everything on a remote build
--      machine, but local, non-Nix builds can be accomplished with `--dev`.
--
-- == 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
-- > -- : sys libssl
--
-- The name is used to lookup the package in `nixpkgs.pkgs.<name>`. Only one
-- package can be listed per line. Language-level deps can automatically
-- determined by passing parsed import statements to a package database, eg
-- `ghc-pkg find-module`. If such a package database is not available, we either
-- keep a hand-written index that maps imports to packages, or we just list the
-- name of the package with:
--
-- > -- : dep package
--
-- 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 the work of walking the source
-- tree.
module Biz.Bild where

import Alpha hiding (sym, (<.>))
import qualified Biz.Bild.Meta as Meta
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 Conduit
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.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

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 :: Meta.Out,
    -- | Output path (into cabdir)
    outPath :: FilePath,
    -- | Fully qualified namespace partitioned by '.'
    namespace :: Namespace,
    -- | Absolute path to file
    path :: FilePath,
    -- | Name of the packageset in Bild.nix to pull langdeps from
    packageSet :: Text,
    -- | Language-specific dependencies, required during compilation
    langdeps :: Set Meta.Dep,
    -- | Local source files on which this target depends
    srcs :: Set FilePath,
    -- | System-level dependencies, required during runtime either via PATH or
    -- linking, depending on the language
    sysdeps :: Set Meta.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)

-- | Use this to just get a target to play with at the repl.
dev_getTarget :: IO Target
dev_getTarget = do
  root <- Env.getEnv "BIZ_ROOT"
  path <- Dir.makeAbsolute "Biz/Bild.hs"
  Namespace.fromPath root path
    |> \case
      Nothing -> panic "Could not get namespace from path"
      Just ns ->
        analyze mempty ns
          /> Map.lookup ns
          /> \case
            Nothing -> panic "Could not retrieve target from analysis"
            Just t -> t

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

outToPath :: Meta.Out -> FilePath
outToPath = \case
  Meta.Bin o -> cab </> "bin" </> o
  Meta.Lib o -> cab </> "lib" </> o
  Meta.None -> mempty

outname :: Meta.Out -> FilePath
outname = \case
  Meta.Bin o -> o
  Meta.Lib o -> o
  Meta.None -> mempty

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

-- | Emulate the *nix hierarchy in the cabdir.
createHier :: String -> IO ()
createHier root =
  traverse_
    (Dir.createDirectoryIfMissing True)
    [ root </> (outToPath <| Meta.Bin ""),
      root </> (outToPath <| Meta.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
      root <- Env.getEnv "BIZ_ROOT"
      let absPath = root </> path
      user <- Env.getEnv "USER" /> Text.pack
      host <- Env.lookupEnv "HOSTNAME" /> fromMaybe "interactive" /> Text.pack
      Log.info ["bild", "analyze", str path]
      let runw cmd args = Process.readProcess cmd args "" /> Text.pack /> Text.words
      contentLines <-
        withFile absPath ReadMode <| \h ->
          IO.hSetEncoding h IO.utf8_bom
            >> Text.IO.hGetContents h
            /> Text.lines
      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 ->
          Meta.detectAll "//" contentLines |> \Meta.Parsed {..} -> do
            nixCFlags <-
              Env.getEnv "NIX_CFLAGS_COMPILE"
                /> Text.pack
                /> Text.words
            langdepFlags <-
              null pdep
                ?. ( runw "pkg-config" ("--cflags" : Set.toList pdep),
                     pure []
                   )
            sysdepFlags <-
              null psys
                ?. ( runw "pkg-config" ("--libs" : Set.toList psys),
                     pure []
                   )
            Target
              { langdeps = pdep,
                sysdeps = psys,
                wrapper = Nothing,
                compiler = Gcc,
                builder = Local user,
                out = pout,
                packageSet = "", -- none, or maybe I should make cPackages?
                compilerFlags =
                  concat
                    [ [o, dir, str absPath]
                        ++ langdepFlags
                        ++ sysdepFlags
                        ++ nixCFlags
                        ++ (map Text.pack <| Set.toList parg)
                      | let outable = pout /= Meta.None,
                        o <- outable ?: (["-o"], []),
                        dir <- outable ?: ([Text.pack <| root </> outToPath pout], [])
                    ],
                outPath = outToPath pout,
                srcs = Set.singleton absPath,
                ..
              }
              |> Just
              |> pure
        Namespace.Hs ->
          contentLines
            |> Meta.detectOut (Meta.out "--")
            |> \out ->
              detectHaskellImports hmap contentLines +> \(langdeps, srcs) ->
                Target
                  { builder = Local user,
                    wrapper = Nothing,
                    compiler = Ghc,
                    packageSet = "ghcWith",
                    compilerFlags =
                      [ "-Werror",
                        "-i$BIZ_ROOT",
                        "-odir",
                        ".",
                        "-hidir",
                        ".",
                        "--make",
                        "$BIZ_ROOT" </> path
                      ]
                        ++ case out of
                          Meta.Bin o ->
                            [ "-main-is",
                              Namespace.toHaskellModule namespace,
                              "-o",
                              o
                            ]
                          _ -> []
                        |> map Text.pack,
                    sysdeps = Meta.detect (Meta.sys "--") contentLines,
                    outPath = outToPath out,
                    ..
                  }
                  |> Just
                  |> pure
        Namespace.Lisp ->
          Meta.detectOut (Meta.out ";;") contentLines |> \out -> do
            langdeps <- detectLispImports contentLines
            Just
              </ pure
                Target
                  { sysdeps = Set.empty,
                    wrapper = Nothing,
                    compiler = Sbcl,
                    packageSet = "sbclWith",
                    compilerFlags =
                      map
                        Text.pack
                        [ "--eval",
                          "(require :asdf)",
                          "--load",
                          absPath,
                          "--eval",
                          "(sb-ext:save-lisp-and-die #p\"" <> (root </> outToPath out) <> "\" :toplevel #'main :executable t)"
                        ],
                    builder = Local <| user,
                    outPath = outToPath out,
                    srcs = Set.singleton absPath,
                    ..
                  }
        Namespace.Nix ->
          (host == "lithium") ?: (Local user, Remote user "dev.simatime.com") |> \builder ->
            Target
              { langdeps = Set.empty,
                wrapper = Nothing,
                sysdeps = Set.empty,
                compiler = NixBuild,
                compilerFlags =
                  [ absPath,
                    "--out-link",
                    root </> nixdir </> Namespace.toPath namespace,
                    "--builders",
                    toNixFlag builder
                  ]
                    |> map Text.pack,
                out = Meta.None,
                outPath = outToPath Meta.None,
                srcs = Set.singleton absPath,
                packageSet = "",
                ..
              }
              |> Just
              |> pure
        Namespace.Scm ->
          Meta.detectAll ";;" contentLines |> \Meta.Parsed {..} ->
            Target
              { langdeps = pdep,
                sysdeps = psys,
                compiler = Guile,
                packageSet = "guilePackages",
                compilerFlags =
                  [ "compile",
                    "--r7rs",
                    "--load-path=" ++ root,
                    "--output=" ++ root </> intdir </> replaceExtension path ".scm.go",
                    absPath
                  ]
                    |> map Text.pack,
                builder = Local user,
                outPath = outToPath pout,
                out = pout,
                srcs = Set.singleton absPath,
                wrapper =
                  (pout == Meta.None)
                    ?: ( Nothing,
                         [ "#!/usr/bin/env bash",
                           "guile -C \""
                             <> root </> intdir
                             <> "\" -e main "
                             <> "-s "
                             <> Namespace.toPath namespace
                             <> " \"$@\""
                         ]
                           |> joinWith "\n"
                           |> Text.pack
                           |> Just
                       ),
                ..
              }
              |> Just
              |> pure
        Namespace.Rs ->
          Meta.detectOut (Meta.out "//") contentLines |> \out ->
            Target
              { langdeps = Set.empty,
                packageSet = "rustPackages",
                wrapper = Nothing,
                sysdeps = Set.empty,
                compiler = Rustc,
                compilerFlags = map Text.pack [absPath, "-o", root </> outToPath out],
                builder = Local user,
                outPath = outToPath out,
                srcs = Set.singleton absPath,
                ..
              }
              |> Just
              |> pure

detectHaskellImports :: Analysis -> [Text] -> IO (Set Meta.Dep, Set FilePath)
detectHaskellImports hmap contentLines =
  Env.getEnv "BIZ_ROOT" +> \root ->
    contentLines
      /> Text.unpack
      /> Regex.match haskellImports
      |> catMaybes
      |> \imports ->
        foldM ghcPkgFindModule Set.empty imports
          +> \pkgs ->
            filepaths imports
              +> \files ->
                findDeps root files
                  +> \deps ->
                    (pkgs <> deps, Set.fromList files)
                      |> pure
  where
    filepaths :: [String] -> IO [FilePath]
    filepaths imports =
      imports
        |> map Namespace.fromHaskellModule
        |> map Namespace.toPath
        |> traverse Dir.makeAbsolute
        +> filterM Dir.doesFileExist
    findDeps :: String -> [FilePath] -> IO (Set Meta.Dep)
    findDeps root fps =
      fps
        |> traverse (pure <. 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 (onlyHaskell hmap)
        /> Map.elems
        /> map langdeps
        /> mconcat
    onlyHaskell :: Analysis -> Analysis
    onlyHaskell = Map.filterWithKey (\ns _ -> ext ns == Namespace.Hs)

detectLispImports :: [Text] -> IO (Set Meta.Dep)
detectLispImports contentLines =
  contentLines
    /> Text.unpack
    /> Regex.match lispRequires
    |> catMaybes
    |> Set.fromList
    |> pure

ghcPkgFindModule :: Set String -> String -> IO (Set String)
ghcPkgFindModule acc m =
  Env.getEnv "GHC_PACKAGE_PATH" +> \packageDb ->
    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, ByteString)
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, mempty)

build :: Bool -> Bool -> Analysis -> IO [Exit.ExitCode]
build andTest loud analysis =
  Env.getEnv "BIZ_ROOT" +> \root ->
    forM (Map.elems analysis) <| \target@Target {..} ->
      fst </ case compiler of
        Gcc ->
          Log.info ["bild", label, "gcc", nschunk namespace]
            >> proc loud namespace (toNixFlag compiler) compilerFlags
          where
            label = case out of
              Meta.Bin _ -> "bin"
              _ -> "lib"
        Ghc -> case out of
          Meta.None -> pure (Exit.ExitSuccess, mempty)
          Meta.Bin _ -> do
            Log.info ["bild", "nix", toLog builder, nschunk namespace]
            result <- nixBuild loud target
            if andTest && (isSuccess <| fst result)
              then test loud target
              else pure result
          Meta.Lib _ -> do
            Log.info ["bild", "dev", "ghc-lib", nschunk namespace]
            proc loud namespace (toNixFlag compiler) compilerFlags
        Guile -> do
          Log.info ["bild", "dev", "guile", nschunk namespace]
          _ <- proc loud namespace (toNixFlag compiler) compilerFlags
          case wrapper of
            Nothing -> pure (Exit.ExitSuccess, mempty)
            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, mempty)
        NixBuild -> do
          Log.info ["bild", "nix", toLog builder, nschunk namespace]
          proc loud namespace (toNixFlag compiler) compilerFlags
        Copy -> do
          Log.warn ["bild", "copy", "not implemented yet", nschunk namespace]
          pure (Exit.ExitSuccess, mempty)
        Rustc -> do
          Log.info ["bild", "dev", "rust", nschunk namespace]
          proc loud namespace (toNixFlag compiler) compilerFlags
        Sbcl -> do
          Log.info ["bild", "dev", "lisp", nschunk namespace]
          proc loud namespace (toNixFlag compiler) compilerFlags

-- | Format for logging
toLog :: Builder -> Text
toLog (Local u) = u
toLog (Remote u h) = u <> "@" <> h

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, ByteString)
run Proc {..} = do
  loud ?| Log.info ["proc", unwords <| map str <| cmd : args] >> Log.br
  Conduit.proc cmd args
    |> Conduit.streamingProcess
    +> \(Conduit.UseProvidedHandle, stdout_, stderr_, hdl) ->
      Conduit.runConduitRes (stdout_ .| Conduit.foldC)
        +> \output ->
          Async.Concurrently (loud ?: (puts stdout_, logs ns stdout_))
            *> Async.Concurrently (loud ?: (puts stderr_, logs ns stderr_))
            *> Async.Concurrently (Conduit.waitForStreamingProcess hdl)
            |> Async.runConcurrently
            +> \case
              Exit.ExitFailure n ->
                puts stderr_
                  >> onFailure
                  >> pure (Exit.ExitFailure n, output)
              Exit.ExitSuccess ->
                onSuccess
                  >> pure (Exit.ExitSuccess, output)

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

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

-- | Like 'puts' but the output goes to a file. Maybe this should use /tmp by default though?
putsToTmp :: Conduit.ConduitT () ByteString (Conduit.ResourceT IO) () -> FilePath -> IO ()
putsToTmp src filepath = Conduit.runConduitRes <| src .| Conduit.sinkFile filepath

-- | Like 'puts' but logs the output via 'Biz.Log'.
logs :: Namespace -> Conduit.ConduitT () ByteString (Conduit.ResourceT IO) () -> IO ()
logs ns src =
  Conduit.runConduitRes
    <| 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

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` ['\'', ':']

nixBuild :: Bool -> Target -> IO (Exit.ExitCode, ByteString)
nixBuild loud Target {..} =
  Env.getEnv "BIZ_ROOT" +> \root ->
    instantiate root |> run +> \case
      (Exit.ExitSuccess, drv) ->
        drv
          |> str
          |> chomp
          |> str
          |> realise
          |> run
          >> run symlink
      x -> pure x
  where
    argstr :: Text -> Text -> [Text]
    argstr n v = ["--argstr", n, v]
    instantiate root =
      Proc
        { loud = loud,
          ns = namespace,
          cmd = "nix-instantiate",
          -- Getting the args quoted correctly is harder than it should be. This
          -- is tightly coupled with the code in the nix builder and there's no
          -- way around that, methinks.
          args =
            [ argstr "srcs" <| unwords <| map str <| (root </> path) : Set.toList srcs,
              argstr "root" <| str root,
              argstr "packageSet" packageSet,
              (argstr "langDeps" <| unwords <| map str <| Set.toList langdeps) <|> mempty,
              argstr "name" <| str <| outname out,
              argstr "buildPhase" <| unwords
                <| (Text.pack <| toNixFlag compiler) :
              compilerFlags,
              [str <| root </> "Biz/Bild/Builder.nix"]
            ]
              |> mconcat
              |> map Text.unpack,
          onFailure = Log.fail ["bild", "instantiate", nschunk namespace] >> Log.br,
          onSuccess = pure ()
        }
    realise drv =
      Proc
        { loud = loud,
          ns = namespace,
          cmd = "nix-store",
          args = ["--realise", drv, "--add-root", nixdir </> outname out],
          onFailure = Log.fail ["bild", "realise", nschunk namespace] >> Log.br,
          onSuccess = Log.good ["bild", nschunk namespace] >> Log.br
        }
    symlink =
      Proc
        { loud = loud,
          ns = namespace,
          cmd = "ln",
          args =
            [ "--relative",
              "--force",
              "--symbolic",
              nixdir </> outname out </> "bin" </> outname out,
              bindir </> outname out
            ],
          onFailure = Log.fail ["bild", "symlink", nschunk namespace] >> Log.br,
          onSuccess = pure ()
        }