Allow includes to be full path or mere package names

SJW.cabal

@@ -32,5 +32,6 @@ executable sjw
                      , mtl
                      , optparse-applicative
                      , text
+                     , unix
   hs-source-dirs:      src
   default-language:    Haskell2010

src/Context.hs

@@ -3,11 +3,16 @@ module Context (
     , Context(..)
     , Contextual
     , Path(..)
+    , packages
   ) where
 
 import Control.Monad.RWS (RWST)
 import Data.List (intercalate)
 import Data.Map (Map)
+import System.Directory (doesDirectoryExist)
+import System.Environment (lookupEnv)
+import System.FilePath ((</>))
+import System.Posix.User (getRealUserID, getUserEntryForID, homeDirectory)
 import Text.ParserCombinators.ReadP (char, munch, sepBy)
 import Text.ParserCombinators.ReadPrec (lift)
 import Text.Read (readPrec)
@@ -32,3 +37,18 @@ instance Read Path where
 
 instance Show CodePath where
   show (CodePath dirs) = intercalate ":" dirs
+
+dbDirectory :: IO FilePath
+dbDirectory = do
+  unixHome <- homeDirectory <$> (getUserEntryForID =<< getRealUserID)
+  home <- maybe unixHome id <$> lookupEnv "HOME"
+  maybe (home </> ".sjw") id <$> lookupEnv "SJW_PACKAGE_DB"
+
+packages :: [String] -> IO [FilePath]
+packages names = do
+  db <- dbDirectory
+  mapM (pathOrPackageName db) names
+  where
+    pathOrPackageName db name = do
+      directoryExists <- doesDirectoryExist name
+      return $ if directoryExists then name else db </> name

src/Main.hs

@@ -2,7 +2,7 @@
 module Main where
 
 import qualified Compiler (main)
-import Context (CodePath(..), Context (..), Path(..))
+import Context (CodePath(..), Context (..), Path(..), packages)
 import Control.Applicative (many, optional)
 import Control.Monad.RWS (evalRWST)
 import qualified Data.Map as Map (empty)
@@ -18,7 +18,7 @@ import qualified Paths_SJW as SJW (version)
 import System.IO (stderr, hPutStrLn)
 
 data Config = Config {
-      includes :: [FilePath]
+      includes :: [String]
     , mainIs :: String
     , outputFile :: FilePath
     , target :: FilePath
@@ -58,9 +58,10 @@ getConfig = execParser $
     (fullDesc <> header ("SJW v" ++ showVersion SJW.version))
 
 runCompiler :: Config -> IO (Text, [String])
-runCompiler (Config {includes, mainIs, target}) =
+runCompiler (Config {includes, mainIs, target}) = do
+  codePaths <- CodePath . (target:) <$> packages includes
   flip (evalRWST Compiler.main) Map.empty $ Context {
-        codePaths = CodePath (target : includes)
+        codePaths
       , mainModule = read mainIs
     }