{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE QuasiQuotes #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE NoImplicitPrelude #-}

-- | A general purpose build tool.
--
-- Not all of the below design is implemented. Currently:
--
-- - with a nix build, results are linked in _/bild/nix/<target>
-- - with a dev build, results are stored in _/bild/dev/<target>
--
-- -----------------------------------------------------------------------------
--
-- == Design constraints
--
--    * only input is a namespace, 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
--
--    * never concerned with deployment/packaging - leave that to another tool
--      (scp? tar?)
--
-- == 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:
--
--        * -s = jump into a shell and/or repl
--
--        * -p = turn on profiling
--
--        * -t = limit build by type (file extension)
--
--        * -e = exclude some regex in the ns tree
--
--        * -o = optimize level
--
-- == 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 `.` for the current directory. Build outputs will go
-- into the _/bild 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`.
--
-- > bild -s <target>
--
-- Starts a repl/shell for target.
--  - if target.hs, load ghci
--  - if target.scm, load scheme repl
--  - if target.clj, load a clojure repl
--  - if target.nix, load nix-shell
--  - and so on.
--
-- > bild -p <target>
--
-- build target with profiling (if available)
--
-- > bild -t nix target
--
-- only build target.nix, not target.hs and so on (in the case of multiple
-- targets with the same name but different extension).
--
-- == Build Metadata
--
-- Metadata is set in the comments with a special syntax. For third-party deps,
-- we list the deps in comments in the target file, like:
--
-- > -- : dep aeson
--
-- The output executable is named with:
--
-- > -- : out my-program
--
-- or
--
-- > -- : out my-ap.js
--
-- When multiple compilers are possible (e.g. ghc vs ghcjs) we use the @out@
-- extension, for example we chose ghcjs when the target @out@ ends in .js. If
-- @out@ does not have an extension, each build type falls back to a default,
-- usually 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 Data.Char as Char
import qualified Data.List as List
import qualified Data.String as String
import qualified Data.Text as Text
import qualified System.Console.Docopt as Docopt
import qualified System.Directory as Dir
import qualified System.Environment as Env
import System.FilePath ((</>))
import qualified System.FilePath as File
import qualified System.Process as Process
import qualified Text.Regex.Applicative as Regex
import qualified Prelude

main :: IO ()
main = Env.getArgs >>= Docopt.parseArgsOrExit help >>= run
  where
    run args =
      Docopt.getAllArgs args (Docopt.argument "target")
        |> mapM_ (\target -> analyze target >>= build)

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

Usage:
  bild <target>...

Options:
  -v, --verbose    Show output from underlying compiler
|]

data Ext = Hs | Scm | Nix
  deriving (Show)

data Namespace = Namespace [String] Ext
  deriving (Show)

type Dep = String

type Out = String

data Compiler = Ghc | Ghcjs | Guile | NixBuild
  deriving (Show)

data Target = Target
  { -- | Output name
    out :: Out,
    -- | Fully qualified namespace partitioned by '.'
    namespace :: Namespace,
    -- | Absolute path to file
    path :: FilePath,
    -- | Parsed/detected dependencies
    deps :: [Dep],
    -- | Which compiler should we use?
    compiler :: Compiler,
    -- | Where is this machine being built? Schema: user@location
    builder :: String
  }
  deriving (Show)

analyze :: String -> IO Target
analyze s = do
  user <- Env.getEnv "USER"
  root <- Env.getEnv "BIZ_ROOT"
  cwd <- Dir.getCurrentDirectory
  let path = cwd </> s
      namespace =
        require "namespace"
          <| path
          |> reps root ""
          |> List.stripPrefix "/"
          >>= Regex.match metaNamespace
  case File.takeExtension path of
    ".hs" -> do
      content <- String.lines </ Prelude.readFile path
      let out = content /> Regex.match metaOut |> catMaybes |> head |> require "out"
      let compiler = if ".js" `List.isSuffixOf` out then Ghcjs else Ghc
      return
        Target
          { deps = content /> Regex.match metaDep |> catMaybes,
            builder = user <> "@localhost",
            ..
          }
    ".nix" ->
      return
        Target
          { deps = [],
            compiler = NixBuild,
            out = "",
            builder =
              join
                [ "ssh://",
                  user,
                  "@dev.simatime.com?ssh-key=/home/",
                  user,
                  "/.ssh/id_rsa"
                ],
            ..
          }
    ".scm" ->
      return
        Target
          { deps = [],
            compiler = Guile,
            out = "",
            builder = user <> "@localhost",
            ..
          }
    e -> panic <| "bild does not know this extension: " <> Text.pack e

build :: Target -> IO ()
build target@Target {..} = do
  root <- Env.getEnv "BIZ_ROOT"
  case compiler of
    Ghc -> do
      putText <| "bild: dev: ghc: " <> nsToPath namespace
      let outDir = root </> "_/bild/dev/bin"
      Dir.createDirectoryIfMissing True outDir
      putText <| "bild: dev: local: " <> Text.pack builder
      Process.callProcess
        "ghc"
        [ "-Werror",
          "-i" <> root,
          "-odir",
          root </> "_/bild/int",
          "-hidir",
          root </> "_/bild/int",
          "--make",
          path,
          "-main-is",
          nsToHaskellModule namespace,
          "-o",
          outDir </> out
        ]
    Ghcjs -> do
      putText <| "bild: dev: ghcjs: " <> nsToPath namespace
      let outDir = root </> "_/bild/dev/static"
      Dir.createDirectoryIfMissing True outDir
      putText <| "bild: dev: local: " <> Text.pack builder
      Process.callProcess
        "ghcjs"
        [ "-Werror",
          "-i" <> root,
          "-odir",
          root </> "_/bild/int",
          "-hidir",
          root </> "_/bild/int",
          "--make",
          path,
          "-main-is",
          nsToHaskellModule namespace,
          "-o",
          outDir </> out
        ]
    Guile -> do
      putText <| "bild: dev: guile: " <> nsToPath namespace
      putText <| "bild: dev: local: " <> Text.pack builder
      putText "bild: guile TODO"
      putText <| show target
    NixBuild -> do
      putText <| "bild: nix: " <> nsToPath namespace
      let outDir = root </> "_/bild/nix"
      Dir.createDirectoryIfMissing True outDir
      putText <| "bild: nix: remote: " <> Text.pack builder
      Process.callProcess
        "nix-build"
        [ path,
          "-o",
          outDir </> (Text.unpack <| nsToPath namespace),
          -- Set default arguments to nix functions
          "--arg",
          "bild",
          "import " <> root
            </> "Biz/Bild/Rules.nix"
            <> " { nixpkgs = import "
            <> root
            </> "Biz/Bild/Nixpkgs.nix"
            <> "; }",
          "--arg",
          "lib",
          "(import " <> root </> "Biz/Bild/Nixpkgs.nix).lib",
          -- Specify remote builders
          "--builders",
          builder
        ]

nsToHaskellModule :: Namespace -> String
nsToHaskellModule (Namespace parts Hs) = joinWith "." parts
nsToHaskellModule (Namespace _ ext) =
  panic <| "can't convert " <> show ext <> " to a Haskell module"

nsToPath :: Namespace -> Text
nsToPath (Namespace parts ext) =
  Text.pack
    <| joinWith "/" parts
    <> "."
    <> lowercase (show ext)

metaNamespace :: Regex.RE Char Namespace
metaNamespace = Namespace </ path <* Regex.sym '.' <*> ext
  where
    name =
      Regex.many (Regex.psym Char.isUpper)
        <> Regex.many (Regex.psym Char.isLower)
    path = Regex.many (name <* Regex.string "/" <|> name)
    ext =
      Nix <$ Regex.string "nix"
        <|> Hs <$ Regex.string "hs"
        <|> Scm <$ Regex.string "scm"

metaDep :: Regex.RE Char Dep
metaDep = Regex.string "-- : dep " *> Regex.many (Regex.psym Char.isAlpha)

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

-- | Replace 'a' in 's' with 'b'.
reps :: String -> String -> String -> String
reps a b s@(x : xs) =
  if isPrefixOf a s
    then -- then, write 'b' and replace jumping 'a' substring
      b ++ reps a b (drop (length a) s)
    else -- then, write 'x' char and try to replace tail string
      x : reps a b xs
reps _ _ [] = []