-----------------------------------------------------------------------------
-- |
-- Module      :  Distribution.Simple.Program.Db
-- Copyright   :  Isaac Jones 2006, Duncan Coutts 2007-2009
--
-- Maintainer  :  cabal-devel@haskell.org
-- Portability :  portable
--
-- This provides a 'ProgramDb' type which holds configured and not-yet
-- configured programs. It is the parameter to lots of actions elsewhere in
-- Cabal that need to look up and run programs. If we had a Cabal monad,
-- the 'ProgramDb' would probably be a reader or state component of it.
--
-- One nice thing about using it is that any program that is
-- registered with Cabal will get some \"configure\" and \".cabal\"
-- helpers like --with-foo-args --foo-path= and extra-foo-args.
--
-- There's also a hook for adding programs in a Setup.lhs script.  See
-- hookedPrograms in 'Distribution.Simple.UserHooks'.  This gives a
-- hook user the ability to get the above flags and such so that they
-- don't have to write all the PATH logic inside Setup.lhs.

module Distribution.Simple.Program.Db (
    -- * The collection of configured programs we can run
    ProgramDb,
    emptyProgramDb,
    defaultProgramDb,
    restoreProgramDb,

    -- ** Query and manipulate the program db
    addKnownProgram,
    addKnownPrograms,
    lookupKnownProgram,
    knownPrograms,
    userSpecifyPath,
    userSpecifyPaths,
    userMaybeSpecifyPath,
    userSpecifyArgs,
    userSpecifyArgss,
    userSpecifiedArgs,
    lookupProgram,
    updateProgram,

    -- ** Query and manipulate the program db
    configureProgram,
    configureAllKnownPrograms,
    reconfigurePrograms,
    requireProgram,
    requireProgramVersion,

  ) where

import Distribution.Simple.Program.Types
         ( Program(..), ProgArg, ConfiguredProgram(..), ProgramLocation(..) )
import Distribution.Simple.Program.Builtin
         ( builtinPrograms )
import Distribution.Simple.Utils
         ( die, findProgramLocation )
import Distribution.Version
         ( Version, VersionRange, isAnyVersion, withinRange )
import Distribution.Text
         ( display )
import Distribution.Verbosity
         ( Verbosity )

import Data.List
         ( foldl' )
import Data.Maybe
         ( catMaybes )
import qualified Data.Map as Map
import Control.Monad
         ( join, foldM )
import System.Directory
         ( doesFileExist )


-- ------------------------------------------------------------
-- * Programs database
-- ------------------------------------------------------------

-- | The configuration is a collection of information about programs. It
-- contains information both about configured programs and also about programs
-- that we are yet to configure.
--
-- The idea is that we start from a collection of unconfigured programs and one
-- by one we try to configure them at which point we move them into the
-- configured collection. For unconfigured programs we record not just the
-- 'Program' but also any user-provided arguments and location for the program.
data ProgramDb = ProgramDb {
        unconfiguredProgs :: UnconfiguredProgs,
        configuredProgs   :: ConfiguredProgs
    }

type UnconfiguredProgram = (Program, Maybe FilePath, [ProgArg])
type UnconfiguredProgs   = Map.Map String UnconfiguredProgram
type ConfiguredProgs     = Map.Map String ConfiguredProgram


emptyProgramDb :: ProgramDb
emptyProgramDb = ProgramDb Map.empty Map.empty


defaultProgramDb :: ProgramDb
defaultProgramDb = restoreProgramDb builtinPrograms emptyProgramDb


-- internal helpers:
updateUnconfiguredProgs :: (UnconfiguredProgs -> UnconfiguredProgs)
                        -> ProgramDb -> ProgramDb
updateUnconfiguredProgs update conf =
  conf { unconfiguredProgs = update (unconfiguredProgs conf) }

updateConfiguredProgs :: (ConfiguredProgs -> ConfiguredProgs)
                      -> ProgramDb -> ProgramDb
updateConfiguredProgs update conf =
  conf { configuredProgs = update (configuredProgs conf) }


-- Read & Show instances are based on listToFM
-- Note that we only serialise the configured part of the database, this is
-- because we don't need the unconfigured part after the configure stage, and
-- additionally because we cannot read/show 'Program' as it contains functions.
instance Show ProgramDb where
  show = show . Map.toAscList . configuredProgs

instance Read ProgramDb where
  readsPrec p s =
    [ (emptyProgramDb { configuredProgs = Map.fromList s' }, r)
    | (s', r) <- readsPrec p s ]


-- | The Read\/Show instance does not preserve all the unconfigured 'Programs'
-- because 'Program' is not in Read\/Show because it contains functions. So to
-- fully restore a deserialised 'ProgramDb' use this function to add
-- back all the known 'Program's.
--
-- * It does not add the default programs, but you probably want them, use
--   'builtinPrograms' in addition to any extra you might need.
--
restoreProgramDb :: [Program] -> ProgramDb -> ProgramDb
restoreProgramDb = addKnownPrograms


-- -------------------------------
-- Managing unconfigured programs

-- | Add a known program that we may configure later
--
addKnownProgram :: Program -> ProgramDb -> ProgramDb
addKnownProgram prog = updateUnconfiguredProgs $
  Map.insertWith combine (programName prog) (prog, Nothing, [])
  where combine _ (_, path, args) = (prog, path, args)


addKnownPrograms :: [Program] -> ProgramDb -> ProgramDb
addKnownPrograms progs conf = foldl' (flip addKnownProgram) conf progs


lookupKnownProgram :: String -> ProgramDb -> Maybe Program
lookupKnownProgram name =
  fmap (\(p,_,_)->p) . Map.lookup name . unconfiguredProgs


knownPrograms :: ProgramDb -> [(Program, Maybe ConfiguredProgram)]
knownPrograms conf =
  [ (p,p') | (p,_,_) <- Map.elems (unconfiguredProgs conf)
           , let p' = Map.lookup (programName p) (configuredProgs conf) ]


-- |User-specify this path.  Basically override any path information
-- for this program in the configuration. If it's not a known
-- program ignore it.
--
userSpecifyPath :: String   -- ^Program name
                -> FilePath -- ^user-specified path to the program
                -> ProgramDb -> ProgramDb
userSpecifyPath name path = updateUnconfiguredProgs $
  flip Map.update name $ \(prog, _, args) -> Just (prog, Just path, args)


userMaybeSpecifyPath :: String -> Maybe FilePath
                     -> ProgramDb -> ProgramDb
userMaybeSpecifyPath _    Nothing conf     = conf
userMaybeSpecifyPath name (Just path) conf = userSpecifyPath name path conf


-- |User-specify the arguments for this program.  Basically override
-- any args information for this program in the configuration. If it's
-- not a known program, ignore it..
userSpecifyArgs :: String    -- ^Program name
                -> [ProgArg] -- ^user-specified args
                -> ProgramDb
                -> ProgramDb
userSpecifyArgs name args' =
    updateUnconfiguredProgs
      (flip Map.update name $
         \(prog, path, args) -> Just (prog, path, args ++ args'))
  . updateConfiguredProgs
      (flip Map.update name $
         \prog -> Just prog { programOverrideArgs = programOverrideArgs prog
                                                 ++ args' })


-- | Like 'userSpecifyPath' but for a list of progs and their paths.
--
userSpecifyPaths :: [(String, FilePath)]
                 -> ProgramDb
                 -> ProgramDb
userSpecifyPaths paths conf =
  foldl' (\conf' (prog, path) -> userSpecifyPath prog path conf') conf paths


-- | Like 'userSpecifyPath' but for a list of progs and their args.
--
userSpecifyArgss :: [(String, [ProgArg])]
                 -> ProgramDb
                 -> ProgramDb
userSpecifyArgss argss conf =
  foldl' (\conf' (prog, args) -> userSpecifyArgs prog args conf') conf argss


-- | Get the path that has been previously specified for a program, if any.
--
userSpecifiedPath :: Program -> ProgramDb -> Maybe FilePath
userSpecifiedPath prog =
  join . fmap (\(_,p,_)->p) . Map.lookup (programName prog) . unconfiguredProgs


-- | Get any extra args that have been previously specified for a program.
--
userSpecifiedArgs :: Program -> ProgramDb -> [ProgArg]
userSpecifiedArgs prog =
  maybe [] (\(_,_,as)->as) . Map.lookup (programName prog) . unconfiguredProgs


-- -----------------------------
-- Managing configured programs

-- | Try to find a configured program
lookupProgram :: Program -> ProgramDb -> Maybe ConfiguredProgram
lookupProgram prog = Map.lookup (programName prog) . configuredProgs


-- | Update a configured program in the database.
updateProgram :: ConfiguredProgram -> ProgramDb
                                   -> ProgramDb
updateProgram prog = updateConfiguredProgs $
  Map.insert (programId prog) prog


-- ---------------------------
-- Configuring known programs

-- | Try to configure a specific program. If the program is already included in
-- the colleciton of unconfigured programs then we use any user-supplied
-- location and arguments. If the program gets configured sucessfully it gets
-- added to the configured collection.
--
-- Note that it is not a failure if the program cannot be configured. It's only
-- a failure if the user supplied a location and the program could not be found
-- at that location.
--
-- The reason for it not being a failure at this stage is that we don't know up
-- front all the programs we will need, so we try to configure them all.
-- To verify that a program was actually sucessfully configured use
-- 'requireProgram'.
--
configureProgram :: Verbosity
                 -> Program
                 -> ProgramDb
                 -> IO ProgramDb
configureProgram verbosity prog conf = do
  let name = programName prog
  maybeLocation <- case userSpecifiedPath prog conf of
    Nothing   -> programFindLocation prog verbosity
             >>= return . fmap FoundOnSystem
    Just path -> do
      absolute <- doesFileExist path
      if absolute
        then return (Just (UserSpecified path))
        else findProgramLocation verbosity path
         >>= maybe (die notFound) (return . Just . UserSpecified)
      where notFound = "Cannot find the program '" ++ name ++ "' at '"
                     ++ path ++ "' or on the path"
  case maybeLocation of
    Nothing -> return conf
    Just location -> do
      version <- programFindVersion prog verbosity (locationPath location)
      let configuredProg        = ConfiguredProgram {
            programId           = name,
            programVersion      = version,
            programDefaultArgs  = [],
            programOverrideArgs = userSpecifiedArgs prog conf,
            programLocation     = location
          }
      extraArgs <- programPostConf prog verbosity configuredProg
      let configuredProg'       = configuredProg {
            programDefaultArgs  = extraArgs
          }
      return (updateConfiguredProgs (Map.insert name configuredProg') conf)


-- | Configure a bunch of programs using 'configureProgram'. Just a 'foldM'.
--
configurePrograms :: Verbosity
                  -> [Program]
                  -> ProgramDb
                  -> IO ProgramDb
configurePrograms verbosity progs conf =
  foldM (flip (configureProgram verbosity)) conf progs


-- | Try to configure all the known programs that have not yet been configured.
--
configureAllKnownPrograms :: Verbosity
                          -> ProgramDb
                          -> IO ProgramDb
configureAllKnownPrograms verbosity conf =
  configurePrograms verbosity
    [ prog | (prog,_,_) <- Map.elems notYetConfigured ] conf
  where
    notYetConfigured = unconfiguredProgs conf
      `Map.difference` configuredProgs conf


-- | reconfigure a bunch of programs given new user-specified args. It takes
-- the same inputs as 'userSpecifyPath' and 'userSpecifyArgs' and for all progs
-- with a new path it calls 'configureProgram'.
--
reconfigurePrograms :: Verbosity
                    -> [(String, FilePath)]
                    -> [(String, [ProgArg])]
                    -> ProgramDb
                    -> IO ProgramDb
reconfigurePrograms verbosity paths argss conf = do
  configurePrograms verbosity progs
   . userSpecifyPaths paths
   . userSpecifyArgss argss
   $ conf

  where
    progs = catMaybes [ lookupKnownProgram name conf | (name,_) <- paths ]


-- | Check that a program is configured and available to be run.
--
-- It raises an exception if the program could not be configured, otherwise
-- it returns the configured program.
--
requireProgram :: Verbosity -> Program -> ProgramDb
               -> IO (ConfiguredProgram, ProgramDb)
requireProgram verbosity prog conf = do

  -- If it's not already been configured, try to configure it now
  conf' <- case lookupProgram prog conf of
    Nothing -> configureProgram verbosity prog conf
    Just _  -> return conf

  case lookupProgram prog conf' of
    Nothing             -> die notFound
    Just configuredProg -> return (configuredProg, conf')

  where notFound       = programName prog
                      ++ " is required but it could not be found."


-- | Check that a program is configured and available to be run.
--
-- Additionally check that the version of the program number is suitable and
-- return it. For example you could require 'AnyVersion' or
-- @'orLaterVersion' ('Version' [1,0] [])@
--
-- It raises an exception if the program could not be configured or the version
-- is unsuitable, otherwise it returns the configured program and its version
-- number.
--
requireProgramVersion :: Verbosity -> Program -> VersionRange
                      -> ProgramDb
                      -> IO (ConfiguredProgram, Version, ProgramDb)
requireProgramVersion verbosity prog range conf = do

  -- If it's not already been configured, try to configure it now
  conf' <- case lookupProgram prog conf of
    Nothing -> configureProgram verbosity prog conf
    Just _  -> return conf

  case lookupProgram prog conf' of
    Nothing                           -> die notFound
    Just configuredProg@ConfiguredProgram { programLocation = location } ->
      case programVersion configuredProg of
        Just version
          | withinRange version range -> return (configuredProg, version, conf')
          | otherwise                 -> die (badVersion version location)
        Nothing                       -> die (noVersion location)

  where notFound       = programName prog ++ versionRequirement
                      ++ " is required but it could not be found."
        badVersion v l = programName prog ++ versionRequirement
                      ++ " is required but the version found at "
                      ++ locationPath l ++ " is version " ++ display v
        noVersion l    = programName prog ++ versionRequirement
                      ++ " is required but the version of "
                      ++ locationPath l ++ " could not be determined."
        versionRequirement
          | isAnyVersion range = ""
          | otherwise          = " version " ++ display range
