{-# LANGUAGE TypeFamilies #-}
module Nirum.Constructs.ModulePath ( ModulePath( ModuleName
                                               , ModulePath
                                               , moduleName
                                               , path
                                               )
                                   , ancestors
                                   , fromFilePath
                                   , fromIdentifiers
                                   ) where

import Data.Char (toLower)
import Data.Maybe (fromMaybe, mapMaybe)
import GHC.Exts (IsList(Item, fromList, toList))

import Data.Set (Set, insert, singleton)
import Data.Text (intercalate, pack)
import System.FilePath (splitDirectories, stripExtension)

import Nirum.Constructs (Construct(toCode))
import Nirum.Constructs.Identifier (Identifier, fromText)

data ModulePath = ModulePath { path :: ModulePath
                             , moduleName :: Identifier }
                | ModuleName { moduleName :: Identifier }
                deriving (Eq, Ord, Show)

instance Construct ModulePath where
    toCode = intercalate "." . map toCode . toList

fromIdentifiers :: [Identifier] -> Maybe ModulePath
fromIdentifiers [] = Nothing
fromIdentifiers [identifier] = Just $ ModuleName identifier
fromIdentifiers identifiers = fmap (`ModulePath` last identifiers) init'
  where
    init' :: Maybe ModulePath
    init' = fromIdentifiers $ init identifiers

fromFilePath :: FilePath -> Maybe ModulePath
fromFilePath filePath =
    if length fileIdentifiers == length paths
    then fromIdentifiers fileIdentifiers
    else Nothing
  where
    replaceLast :: (a -> a) -> [a] -> [a]
    replaceLast _ [] = []
    replaceLast f l = init l ++ [f $ last l]
    paths :: [FilePath]
    paths = replaceLast (fromMaybe "" . stripExtension "nrm" . map toLower)
                        (splitDirectories filePath)
    fileIdentifiers :: [Identifier]
    fileIdentifiers = mapMaybe (fromText . pack) paths

ancestors :: ModulePath -> Set ModulePath
ancestors m@ModuleName {} = singleton m
ancestors m@(ModulePath parent _) = m `insert` ancestors parent

instance IsList ModulePath where
    type Item ModulePath = Identifier
    fromList identifiers =
        fromMaybe (error "ModulePath cannot be empty") 
                  (fromIdentifiers identifiers)
    toList (ModuleName identifier) = [identifier]
    toList (ModulePath path' identifier) = toList path' ++ [identifier]