{-# OPTIONS_GHC -Wall #-}
{-# LANGUAGE OverloadedStrings #-}
module ToySolver.Data.MIP.Solution.Gurobi
  ( Solution (..)
  , render
  , writeFile
  , parse
  , readFile
  ) where

import Prelude hiding (readFile, writeFile)
import Control.Applicative
import Data.Default.Class
import Data.Interned (intern, unintern)
import Data.List (foldl')
import qualified Data.Map as Map
import Data.Monoid
import Data.Scientific (Scientific)
import qualified Data.Text.Lazy as TL
import qualified Data.Text.Lazy.Builder as B
import qualified Data.Text.Lazy.Builder.Scientific as B
import qualified Data.Text.Lazy.IO as TLIO
import ToySolver.Data.MIP (Solution)
import qualified ToySolver.Data.MIP as MIP

render :: MIP.Solution Scientific -> TL.Text
render sol = B.toLazyText $ ls1 <> mconcat ls2
  where
    ls1 = case MIP.solObjectiveValue sol of
            Nothing  -> mempty
            Just val -> "# Objective value = " <> B.scientificBuilder val <> B.singleton '\n'
    ls2 = [ B.fromText (unintern name) <> B.singleton ' ' <> B.scientificBuilder val <> B.singleton '\n'
          | (name,val) <- Map.toList (MIP.solVariables sol)
          ]

writeFile :: FilePath -> MIP.Solution Scientific -> IO ()
writeFile fname sol = do
  TLIO.writeFile fname (render sol)

parse :: TL.Text -> MIP.Solution Scientific
parse t = 
  case foldl' f (Nothing,[]) $ TL.lines t of
    (obj, vs) ->
      def{ MIP.solStatus = MIP.StatusFeasible
         , MIP.solObjectiveValue = obj
         , MIP.solVariables = Map.fromList vs
         }
  where
    f :: (Maybe Scientific, [(MIP.Var, Scientific)]) -> TL.Text -> (Maybe Scientific, [(MIP.Var, Scientific)])
    f (obj,vs) l
      | Just l2 <- TL.stripPrefix "# " l
      , Just l3 <- TL.stripPrefix "objective value = " (TL.toLower l2)
      , (r:_) <- [r | (r,[]) <- reads (TL.unpack l3)] =
          (Just r, vs)
      | otherwise =
          case TL.words (TL.takeWhile (/= '#') l) of
            [w1, w2] -> (obj, (intern (TL.toStrict w1), read (TL.unpack w2)) : vs)
            [] -> (obj, vs)
            _ -> error ("ToySolver.Data.MIP.Solution.Gurobi: invalid line " ++ show l)

readFile :: FilePath -> IO (MIP.Solution Scientific)
readFile fname = parse <$> TLIO.readFile fname