{-# LANGUAGE TypeFamilies, ScopedTypeVariables #-}
module Language.Haskell.Names.Recursive
  ( computeInterfaces
  , getInterfaces
  , annotateModule
  ) where

import Data.Graph(stronglyConnComp, flattenSCC)
import Data.Monoid
import Data.Data (Data)
import qualified Data.Set as Set
import Control.Monad hiding (forM_)
import Language.Haskell.Exts.Annotated
import Distribution.HaskellSuite.Modules
import Data.Maybe
import Data.Foldable

import Language.Haskell.Names.Types
import Language.Haskell.Names.SyntaxUtils
import Language.Haskell.Names.ScopeUtils
import Language.Haskell.Names.ModuleSymbols
import Language.Haskell.Names.Exports
import Language.Haskell.Names.Imports
import Language.Haskell.Names.Open.Base
import Language.Haskell.Names.Annotated

-- | Take a set of modules and return a list of sets, where each sets for
-- a strongly connected component in the import graph.
-- The boolean determines if imports using @SOURCE@ are taken into account.
groupModules :: forall l . [Module l] -> [[Module l]]
groupModules modules =
  map flattenSCC $ stronglyConnComp $ map mkNode modules
    mkNode :: Module l -> (Module l, ModuleName (), [ModuleName ()])
    mkNode m =
      ( m
      , dropAnn $ getModuleName m
      , map (dropAnn . importModule) $ getImports m

-- | Annotate a module with scoping information. This assumes that all
-- module dependencies have been resolved and cached — usually you need
-- to run 'computeInterfaces' first, unless you have one module in
-- isolation.
  :: (MonadModule m, ModuleInfo m ~ Symbols, Data l, SrcInfo l, Eq l)
  => Language -- ^ base language
  -> [Extension] -- ^ global extensions (e.g. specified on the command line)
  -> Module l -- ^ input module
  -> m (Module (Scoped l)) -- ^ output (annotated) module
annotateModule lang exts mod@(Module lm mh os is ds) = do
  let extSet = moduleExtensions lang exts mod
  (imp, impTbl) <- processImports extSet is
  let tbl = moduleTable impTbl mod
  (exp, _syms) <- processExports tbl mod

    lm' = none lm
    os' = fmap noScope os
    is' = imp
    ds' = annotate (initialScope tbl) `map` ds

    mh' = flip fmap mh $ \(ModuleHead lh n mw _me) ->
        lh' = none lh
        n'  = noScope n
        mw' = fmap noScope mw
        me' = exp
      in ModuleHead lh' n' mw' me'

  return $ Module lm' mh' os' is' ds'

annotateModule _ _ _ = error "annotateModule: non-standard modules are not supported"

-- | Compute interfaces for a set of mutually recursive modules and write
-- the results to the cache. Return the set of import/export errors.
  :: (Ord l, Data l, MonadModule m, ModuleInfo m ~ Symbols)
  => [(Module l, ExtensionSet)]
      -- ^ module and all extensions with which it is to be compiled.
      -- Use 'moduleExtensions' to build this list.
  -> m (Set.Set (Error l))
findFixPoint mods = go mods (map (const mempty) mods) where
  go mods syms = do
    forM_ (zip syms mods) $ \(s,(m, _)) -> insertInCache (getModuleName m) s
    (syms', errors) <- liftM unzip $ forM mods $ \(m, extSet) -> do
      (imp, impTbl) <- processImports extSet $ getImports m
      let tbl = moduleTable impTbl m
      (exp, syms) <- processExports tbl m
      return (syms, foldMap getErrors imp <> foldMap getErrors exp)
    if syms' == syms
      then return $ mconcat errors
      else go mods syms'

-- | 'computeInterfaces' takes a list of possibly recursive modules and
-- computes the interface of each module. The computed interfaces are
-- written into the @m@'s cache and are available to further computations
-- in this monad.
-- Returns the set of import/export errors. Note that the interfaces are
-- registered in the cache regardless of whether there are any errors, but
-- if there are errors, the interfaces may be incomplete.
  :: (MonadModule m, ModuleInfo m ~ Symbols, Data l, SrcInfo l, Ord l)
  => Language -- ^ base language
  -> [Extension] -- ^ global extensions (e.g. specified on the command line)
  -> [Module l] -- ^ input modules
  -> m (Set.Set (Error l)) -- ^ errors in export or import lists
computeInterfaces lang exts =
  liftM fold . mapM findFixPoint . map supplyExtensions . groupModules
    supplyExtensions = map $ \m -> (m, moduleExtensions lang exts m)

-- | Like 'computeInterfaces', but also returns a list of interfaces, one
-- per module and in the same order
  :: (MonadModule m, ModuleInfo m ~ Symbols, Data l, SrcInfo l, Ord l)
  => Language -- ^ base language
  -> [Extension] -- ^ global extensions (e.g. specified on the command line)
  -> [Module l] -- ^ input modules
  -> m ([Symbols], Set.Set (Error l)) -- ^ output modules, and errors in export or import lists
getInterfaces lang exts mods = do
  errs <- computeInterfaces lang exts mods
  ifaces <- forM mods $ \mod ->
    let modName = getModuleName mod in
    fromMaybe (error $ msg modName) `liftM` lookupInCache modName
  return (ifaces, errs)
    msg modName = "getInterfaces: module " ++ modToString modName ++ " is not in the cache"