Copyright (C) 2009 Mathieu Boespflug <mboes@tweag.net>

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it under the terms of the GNU General Public License as published by
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> module Main where

This file brings together the various pieces that make up the hmk command. The
core logic is in Control.Hmk. That module knows only rules, from which it can
produce a schedule of recipes to run. Despite the name, it is the most generic
part of the application.

Rules may be generated by instantiating meta-rules, as often appears in
mkfile's. Instantiation of meta-rules is done by the parser, with the help of
the Metarule module. In fact most of the work is done by the parser, as it is
also the parser's job to carry forward any variable substitutions.

> import Control.Hmk
> import Control.Hmk.Analyze
> import Parse
> import Eval
> import Metarule
> import Control.Monad
> import Control.Applicative
> import qualified Data.Sequence as Seq
> import qualified Data.Foldable as Seq

The exit code of the command is the exit code of the last recipe executed.

> import System.IO
> import System.Environment
>
>
> main :: IO ()
> main = do
>   targets <- map File <$> getArgs
>   metarules <- eval =<< parse "mkfile" <$> readFile "mkfile"
>   let rules = Seq.toList $ instantiateRecurse (Seq.fromList targets) metarules
>   when (null rules) (fail "No rules in mkfile.")
>   -- completed and coalesced rules.
>   let crules = process Eval.isStale rules

Per the mk man page, if no targets are specified on the command line, then
assume the target is that of the first rule.

>   schedule <- case targets of
>                 [] -> mk crules [target (head rules)]
>                 _  -> mk crules targets
>   sequence_ schedule