-- cabal-helper: Simple interface to Cabal's configuration state
-- Copyright (C) 2015-2018  Daniel Gröber <cabal-helper@dxld.at>
--
-- This program is free software: you can redistribute it and/or modify
-- it under the terms of the GNU General Public License as published by
-- the Free Software Foundation, either version 3 of the License, or
-- (at your option) any later version.
--
-- This program is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-- GNU General Public License for more details.
--
-- You should have received a copy of the GNU General Public License
-- along with this program.  If not, see <http://www.gnu.org/licenses/>.

{-# LANGUAGE DeriveGeneric, DeriveDataTypeable, DefaultSignatures,
  StandaloneDeriving, GADTs, DataKinds, KindSignatures, RankNTypes, PolyKinds #-}

{-|
Module      : CabalHelper.Compiletime.Types
Description : Types used throughout
License     : GPL-3
-}

module CabalHelper.Compiletime.Types where

import Cabal.Plan
  ( PlanJson )
import Data.ByteString (ByteString)
import Data.IORef
import Data.Version
import Data.Typeable
import GHC.Generics
import System.FilePath (takeDirectory)
import System.Posix.Types
import CabalHelper.Compiletime.Types.RelativePath
import CabalHelper.Shared.InterfaceTypes

import Data.List.NonEmpty (NonEmpty)
--import qualified Data.List.NonEmpty as NonEmpty
import Data.Map.Strict (Map)
--import qualified Data.Map.Strict as Strict

-- | The kind of project being managed by a 'QueryEnv' (pun intended). Used
-- as a phantom-type variable throughout to make the project type being
-- passed into various functions correspond to the correct implementation.
data ProjType
    = Cabal CabalProjType -- ^ @cabal@ project.
    | Stack -- ^ @stack@ project.
      deriving (Eq, Ord, Show, Read)

-- | The kind of a @cabal@ project.
data CabalProjType
    = CV1 -- ^ @cabal v1-build@ project.
    | CV2 -- ^ @cabal v2-build@ project.
      deriving (Eq, Ord, Show, Read)

-- | A "singleton" datatype for 'ProjType' which allows us to establish a
-- correspondence between a runtime representation of 'ProjType' to the
-- compile-time value at the type level.
--
-- If you just want to know the runtime 'ProjType' use 'demoteSProjType' to
-- convert to that.
data SProjType pt where
    SCabal :: !(SCabalProjType pt) -> SProjType ('Cabal pt)
    SStack :: SProjType 'Stack

deriving instance Show (SProjType pt)

-- | This is a singleton, like 'SProjType', but restricted to just the
-- Cabal project types. We use this to restrict some functions which don't
-- make sense for Stack to just the Cabal project types.
data SCabalProjType pt where
    SCV1 :: SCabalProjType 'CV1
    SCV2 :: SCabalProjType 'CV2

deriving instance Show (SCabalProjType pt)

demoteSProjType :: SProjType pt -> ProjType
demoteSProjType (SCabal SCV1) = Cabal CV1
demoteSProjType (SCabal SCV2) = Cabal CV2
demoteSProjType SStack = Stack

-- | Location of a project context. This is usually just the path project's
-- top-level source code directory together with an optional project-type
-- specific config file path.
--
-- To find any recognized default project contexts in a given directory
-- use 'Distribution.Helper.Discover.findProjects'.
--
-- Build tools usually allow the user to specify the location of their
-- project config files manually, so we also support passing this path here
-- with the @*File@ constructors.
--
-- === Correspondence between Project and Package Source Directories
--
-- Note that the project's source directory does not necessarily correspond
-- to the directory containing the project config file, though in some
-- cases it does.
--
-- For example @cabal v2-build@ allows the @cabal.project@ file to be
-- positively anywhere in the filesystem when specified via the
-- @--cabal-project@ command-line flag, corresponding to the
-- 'ProjLocV2File' constructor here. This config file can then refer to
-- package directories with absolute paths in the @packages:@ declaration.
--
-- Hence it isn't actually possible to find /one/ directory which contains
-- the whole project's source code but rather we have to consider each
-- package's source directory individually, see 'Package.pSourceDir'
data ProjLoc (pt :: ProjType) where
    -- | A fully specified @cabal v1-build@ project context. Here you can
    -- specify both the path to the @.cabal@ file and the source directory
    -- of the package. The cabal file path corresponds to the
    -- @--cabal-file=PATH@ flag on the @cabal@ command line.
    --
    -- Note that more than one such files existing in a package directory
    -- is a user error and while cabal will still complain about that we
    -- won't.
    --
    -- Also note that for this project type the concepts of project and
    -- package coincide.
    ProjLocV1CabalFile :: { plCabalFile :: !FilePath, plProjectDirV1 :: !FilePath } -> ProjLoc ('Cabal 'CV1)

    -- | A @cabal v1-build@ project context. Essentially the same as
    -- 'ProjLocV1CabalFile' but this will dynamically search for the cabal
    -- file for you as cabal-install does by default.
    --
    -- If more than one @.cabal@ file is found in the given directory we
    -- will shamelessly throw a obscure exception so prefer
    -- 'ProjLocV1CabalFile' if you don't want that to happen. This mainly
    -- exists for easy upgrading from the @cabal-helper-0.8@ series.
    ProjLocV1Dir :: { plProjectDirV1 :: !FilePath } -> ProjLoc ('Cabal 'CV1)

    -- | A @cabal v2-build@ project context. The path to the
    -- @cabal.project@ file, though you can call it whatever you like. This
    -- configuration file then points to the packages that make up this
    -- project. This corresponds to the @--cabal-project=PATH@ flag on the
    -- @cabal@ command line.
    ProjLocV2File    :: { plCabalProjectFile :: !FilePath, plProjectDirV2 :: !FilePath } -> ProjLoc ('Cabal 'CV2)

    -- | This is equivalent to 'ProjLocV2File' but using the default
    -- @cabal.project@ file name in the given directory.
    ProjLocV2Dir     :: { plProjectDirV2 :: !FilePath } -> ProjLoc ('Cabal 'CV2)

    -- | A @stack@ project context. Specify the path to the @stack.yaml@
    -- file here. This configuration file then points to the packages that
    -- make up this project. Corresponds to @stack@'s @--stack-yaml=PATH@
    -- command line flag if different from the default name, @stack.yaml@.
    --
    -- Note: with Stack the invariant @takeDirectory plStackYaml == projdir@ holds.
    ProjLocStackYaml :: { plStackYaml :: !FilePath } -> ProjLoc 'Stack

deriving instance Show (ProjLoc pt)

plV1Dir :: ProjLoc ('Cabal 'CV1) -> FilePath
plV1Dir ProjLocV1CabalFile {plProjectDirV1} = plProjectDirV1
plV1Dir ProjLocV1Dir {plProjectDirV1} = plProjectDirV1

plCabalProjectDir :: ProjLoc ('Cabal cpt) -> FilePath
plCabalProjectDir ProjLocV1CabalFile {plProjectDirV1} = plProjectDirV1
plCabalProjectDir ProjLocV1Dir  {plProjectDirV1} = plProjectDirV1
plCabalProjectDir ProjLocV2File {plProjectDirV2} = plProjectDirV2
plCabalProjectDir ProjLocV2Dir  {plProjectDirV2} = plProjectDirV2

plStackProjectDir :: ProjLoc 'Stack -> FilePath
plStackProjectDir ProjLocStackYaml {plStackYaml} = takeDirectory plStackYaml

projTypeOfProjLoc :: ProjLoc pt -> SProjType pt
projTypeOfProjLoc ProjLocV1CabalFile{} = SCabal SCV1
projTypeOfProjLoc ProjLocV1Dir{}       = SCabal SCV1
projTypeOfProjLoc ProjLocV2File{}      = SCabal SCV2
projTypeOfProjLoc ProjLocV2Dir{}       = SCabal SCV2
projTypeOfProjLoc ProjLocStackYaml{}   = SStack

-- | A build directory for a certain project type. The @pt@ type variable
-- must be compatible with the 'ProjLoc' used. This is enforced by the type
-- system so you can't get this wrong.
data DistDir (pt :: ProjType) where
    -- | A build-directory for cabal, aka. dist-dir in Cabal
    -- terminology. 'SCabalProjType' specifies whether we should use
    -- /v2-build/ or /v1-build/. This choice must correspond to
    -- 'ProjLoc' \'s project type.
    DistDirCabal :: !(SCabalProjType pt) -> !FilePath -> DistDir ('Cabal pt)

    -- | A build-directory for stack, aka. /work-dir/. Optionally override
    -- Stack's /work-dir/. If you just want to use Stack's default set to
    -- @Nothing@
    DistDirStack :: !(Maybe RelativePath) -> DistDir 'Stack

deriving instance Show (DistDir pt)

projTypeOfDistDir :: DistDir pt -> SProjType pt
projTypeOfDistDir (DistDirCabal pt _) = SCabal pt
projTypeOfDistDir DistDirStack{} = SStack

-- | General purpose existential wrapper. Useful for hiding a phantom type
-- argument.
--
-- Say you have:
--
-- @
-- {-\# LANGUAGE DataKinds, GADTS \#-}
-- data K = A | B | ...
-- data Q k where
--   QA :: ... -> Q 'A
--   QB :: ... -> Q 'B
-- @
--
-- and you want a list of @Q@. You can use @Ex@ to hide the phantom type
-- argument and recover it later by matching on the GADT constructors:
--
-- @
-- qa :: Q A
-- qa = QA
--
-- qb :: Q B
-- qb = QB
--
-- mylist :: [Ex Q]
-- mylist = [Ex qa, Ex qb]
-- @
data Ex a = forall x. Ex (a x)

-- | Environment for running a 'Query'. The constructor is not exposed in the
-- API to allow extending it with more fields without breaking user code.
--
-- To create a 'QueryEnv' use the 'mkQueryEnv' smart constructor instead. Some
-- field accessors are exported and may be used to override the defaults filled
-- in by 'mkQueryEnv'. See below.
--
-- Note that this environment contains an 'IORef' used as a cache. If you want
-- to take advantage of this you should not simply discard the value returned by
-- the smart constructor after one use.
type QueryEnv pt = QueryEnvI QueryCache pt

data QueryEnvI c (pt :: ProjType) = QueryEnv
    { qeReadProcess :: !ReadProcessWithCwdAndEnv
    -- ^ Field accessor for 'QueryEnv'. Function used to to start processes
    -- and capture output. Useful if you need to, for example, redirect
    -- standard error output of programs started by cabal-helper.

    , qeCallProcess :: !(CallProcessWithCwdAndEnv ())
    -- ^ Field accessor for 'QueryEnv'. Function used to to start processes
    -- without capturing output. See also 'qeReadProcess'.

    , qePrograms     :: !Programs
    -- ^ Field accessor for 'QueryEnv'. Paths to various programs we use.

    , qeProjLoc      :: !(ProjLoc pt)
    -- ^ Field accessor for 'QueryEnv'. Defines path to the project directory,
    -- i.e. a directory containing a @cabal.project@ file

    , qeDistDir      :: !(DistDir pt)
    -- ^ Field accessor for 'QueryEnv'. Defines path to the @dist/@ or
    -- @dist-newstyle/@ directory, aka. /builddir/ in Cabal terminology.

    , qeCacheRef     :: !(IORef (c pt))
    -- ^ Cache for query results, only accessible when type parameter @c@ is
    -- instantiated with 'QueryCache'. This is the case wherever the type alias
    -- 'QueryEnv' is used.

    , qeCacheKeys    :: IORef (CacheKeyCache pt)
    }

projTypeOfQueryEnv :: QueryEnvI c pt -> SProjType pt
projTypeOfQueryEnv = projTypeOfProjLoc . qeProjLoc

type ReadProcessWithCwdAndEnv   =
  String -> CallProcessWithCwdAndEnv String

type CallProcessWithCwdAndEnv a =
  Maybe FilePath -> [(String, EnvOverride)] -> FilePath -> [String] -> IO a

-- | Full instansiation of 'QueryCacheI', with all cache fields visible
type QueryCache
  = QueryCacheI
      PreInfo
      Programs
      ProjInfo
      UnitInfo

-- | 'QueryCacheI', only instantiated with 'PreInfo' cache.
type QCPreInfo progs proj_info unit_info
  = QueryCacheI
      PreInfo
      progs
      proj_info
      unit_info

-- | 'QueryCacheI', only instantiated with 'PreInfo' and configured
-- 'Programs' cache.
type QCProgs proj_info unit_info
  = QueryCacheI
      PreInfo
      Programs
      proj_info
      unit_info

data QueryCacheI pre_info progs proj_info unit_info pt = QueryCache
    { qcPreInfo
        :: !(Maybe ((ProjConf pt, ProjConfModTimes), pre_info pt))
    , qcConfProgs :: !(Maybe (Programs, progs))
    , qcProjInfo
        :: !(Maybe ((ProjConf pt, ProjConfModTimes), proj_info pt))
    , qcUnitInfos :: !(Map DistDirLib unit_info)
    }

data CacheKeyCache pt = CacheKeyCache
    { ckcProjConf :: !(Maybe (ProjConf pt, ProjConfModTimes))
    }

newtype DistDirLib = DistDirLib FilePath
    deriving (Eq, Ord, Read, Show)

type Package pt = Package' (NonEmpty (Unit pt))

-- | A 'Package' is a named collection of many 'Unit's.
data Package' units = Package
    { pPackageName :: !String
    , pSourceDir   :: !FilePath
    , pCabalFile   :: !CabalFile
    , pFlags       :: ![(String, Bool)]
    -- | Cabal flags to set when configuring and building this package.
    , pUnits       :: !units
    } deriving (Show)

-- | A 'Unit' is essentially a "build target". It is used to refer to a set
-- of components (exes, libs, tests etc.) which are managed by a certain
-- instance of the Cabal build-system[1]. We may get information on the
-- components in a unit by retriving the corresponding 'UnitInfo'.
--
-- \[1]: No I'm not talking about the cabal-install /build-tool/, I'm
-- talking about the Cabal /build-system/. Note the distinction. Both
-- cabal-install and Stack use the Cabal build-system (aka @lib:Cabal@)
-- underneath.
--
-- Note that a 'Unit' value is only valid within the 'QueryEnv' context it
-- was created in, this is however this is not enforced by the
-- API. Furthermore if the user changes the underlying project
-- configuration while your application is running even a properly scoped
-- 'Unit' could become invalid because the component it belongs to was
-- removed from the cabal file.
data Unit pt = Unit
    { uUnitId      :: !UnitId
    , uPackage     :: !(Package' ())
    , uDistDir     :: !DistDirLib
    , uImpl        :: !(UnitImpl pt)
    } deriving (Show)

data UnitImpl pt where
  UnitImplV1 :: UnitImpl ('Cabal 'CV1)

  UnitImplV2 ::
    { uiV2ComponentNames :: ![ChComponentName]
    , uiV2Components     :: ![String]
    , uiV2OnlyDependencies :: !Bool
    } -> UnitImpl ('Cabal 'CV2)

  UnitImplStack :: UnitImpl 'Stack

deriving instance Show (UnitImpl pt)

-- | This returns the component a 'Unit' corresponds to. This information is
-- only available if the correspondence happens to be unique and known before
-- querying setup-config for the respective project type. Currently this only
-- applies to @pt=@'V2'.
--
-- This is intended to be used as an optimization, to allow reducing the number
-- of helper invocations for clients that don't need to know the entire project
-- structure.
uComponentName :: Unit pt -> Maybe ChComponentName
uComponentName Unit { uImpl=UnitImplV2 { uiV2ComponentNames=[comp] } } =
    Just comp
uComponentName _ =
    Nothing

-- | The @setup-config@ header. Note that Cabal writes all the package names in
-- the header using 'Data.ByteString.Char8' and hence all characters are
-- truncated from Unicode codepoints to 8-bit Latin-1.
--
-- We can be fairly confident that 'uhSetupId' and 'uhCompilerId' won\'t have
-- names that cause trouble here so it's ok to look at them but user packages
-- are free to have any unicode name.
data UnitHeader = UnitHeader
    { uhPackageId  :: !(ByteString, Version)
      -- ^ Name and version of the source package. This is only going to be
      -- usable for unicode package names starting with @Cabal-3.0.0.0@. See
      -- 'uiPackageId' for an alternative that always works.
    , uhSetupId    :: !(ByteString, Version)
      -- ^ Name and version of the @Setup.hs@ implementation. We expect
      -- @"Cabal"@ here, naturally.
    , uhCompilerId :: !(ByteString, Version)
      -- ^ Name and version of the compiler that was used to build
      -- Setup.hs. WARNING: This does not identify the GHC version the project
      -- is configured to use!
    } deriving (Eq, Ord, Read, Show)

newtype UnitId = UnitId String
    deriving (Eq, Ord, Read, Show)

-- | The information extracted from a 'Unit'\'s on-disk configuration cache.
data UnitInfo = UnitInfo
    { uiUnitId                :: !UnitId
    -- ^ A unique identifier of this unit within the originating project.

    , uiPackageId             :: !(String, Version)
    -- ^ The package-name and version this unit belongs to.

    , uiComponents            :: !(Map ChComponentName ChComponentInfo)
    -- ^ The components of the unit: libraries, executables, test-suites,
    -- benchmarks and so on.

    , uiCompilerId            :: !(String, Version)
    -- ^ The version of GHC the unit is configured to use

    , uiPackageFlags          :: !([(String, Bool)])
    -- ^ Flag definitions from cabal file

    , uiConfigFlags           :: ![(String, Bool)]
    -- ^ Flag assignments from active configuration

    , uiNonDefaultConfigFlags :: ![(String, Bool)]
    -- ^ Flag assignments from setup-config which differ from the default
    -- setting. This can also include flags which cabal decided to modify,
    -- i.e. don't rely on these being the flags set by the user directly.

    , uiModTimes              :: !UnitModTimes
    -- ^ Key for cache invalidation. When this is not equal to the value
    -- returned by 'getUnitModTimes' this 'UnitInfo' is considered invalid.
    } deriving (Eq, Ord, Read, Show)

-- | Files relevant to the project-scope configuration. We gather them here so
-- we can refer to their paths conveniently throughout the code. These files are
-- not necessarily guaranteed to even exist.
data ProjConf pt where
  ProjConfV1 ::
    { pcV1CabalFile :: !FilePath
    } -> ProjConf ('Cabal 'CV1)

  ProjConfV2 ::
    { pcV2CabalProjFile       :: !FilePath
    , pcV2CabalProjLocalFile  :: !FilePath
    , pcV2CabalProjFreezeFile :: !FilePath
    } -> ProjConf ('Cabal 'CV2)

  ProjConfStack ::
    { pcStackYaml :: !FilePath
    } -> ProjConf 'Stack

projTypeOfProjConf :: ProjConf pt -> SProjType pt
projTypeOfProjConf ProjConfV1{}    = SCabal SCV1
projTypeOfProjConf ProjConfV2{}    = SCabal SCV2
projTypeOfProjConf ProjConfStack{} = SStack


-- This is supposed to be opaque, as it's only meant to be used only for cache
-- invalidation.
newtype ProjConfModTimes = ProjConfModTimes [(FilePath, EpochTime)]
    deriving (Eq, Show)

-- | Project-scope information cache.
data ProjInfo pt = ProjInfo
  { piCabalVersion     :: !Version
  , piPackages         :: !(NonEmpty (Package pt))
  , piImpl             :: !(ProjInfoImpl pt)
  , piProjConfModTimes :: !ProjConfModTimes
  -- ^ Key for cache invalidation. When this is not equal to the return
  -- value of 'getProjConfModTime' this 'ProjInfo' is considered invalid.
  } deriving (Show)

data ProjInfoImpl pt where
  ProjInfoV1 ::
    { piV1SetupHeader :: !UnitHeader
    } -> ProjInfoImpl ('Cabal 'CV1)

  ProjInfoV2 ::
    { piV2Plan        :: !PlanJson
    , piV2PlanModTime :: !EpochTime
    , piV2CompilerId  :: !(String, Version)
    } -> ProjInfoImpl ('Cabal 'CV2)

  ProjInfoStack :: ProjInfoImpl 'Stack

instance Show (ProjInfoImpl pt) where
    show ProjInfoV1 {..} = concat
      [ "ProjInfoV1 {"
      , "piV1SetupHeader = ", show piV1SetupHeader, ", "
      , "}"
      ]
    show ProjInfoV2 {..} = concat
      [ "ProjInfoV2 {"
      , "piV2Plan = ", show piV2Plan, ", "
      , "piV2PlanModTime = ", show piV2PlanModTime, ", "
      , "piV2CompilerId = ", show piV2CompilerId
      , "}"
      ]
    show ProjInfoStack{} = concat
      [ "ProjInfoStack {"
      , "}"
      ]

data UnitModTimes = UnitModTimes
    { umtPkgYaml     :: !(Maybe (FilePath, EpochTime))
    , umtCabalFile   :: !(FilePath, EpochTime)
    , umtSetupConfig :: !(Maybe (FilePath, EpochTime))
    } deriving (Eq, Ord, Read, Show)
data PreInfo pt where
  PreInfoCabal :: PreInfo ('Cabal cpt)
  PreInfoStack ::
    { piStackProjPaths :: !StackProjPaths
    } -> PreInfo 'Stack

instance Show (PreInfo pt) where
    show PreInfoCabal{} = concat
      [ "PreInfoCabal {"
      , "}"
      ]
    show PreInfoStack {..} = concat
      [ "PreInfoStack {"
      , "piStackProjPaths = ", show piStackProjPaths
      , "}"
      ]

newtype CabalFile = CabalFile FilePath
    deriving (Show)

data StackProjPaths = StackProjPaths
    { sppGlobalPkgDb :: !PackageDbDir
    , sppSnapPkgDb   :: !PackageDbDir
    , sppLocalPkgDb  :: !PackageDbDir
    , sppCompExe     :: !FilePath
    } deriving (Show)


-- Beware: GHC 8.0.2 doesn't like these being recursively defined for some
-- reason so just keep them unrolled.
type Verbose = (?verbose :: Word -> Bool)
type Env     = ( ?progs :: Programs
               , ?verbose :: Word -> Bool)
type Progs   = (?progs :: Programs)

-- | Configurable paths to various programs we use.
data Programs = Programs
    { cabalProgram    :: !FilePath
      -- ^ The path to the @cabal@ program.
    , cabalProjArgs   :: ![String]
    , cabalUnitArgs   :: ![String]

    , stackProgram    :: !FilePath
      -- ^ The path to the @stack@ program.
    , stackProjArgs   :: ![String]
    , stackUnitArgs   :: ![String]
    , stackEnv        :: ![(String, EnvOverride)]
      --  ^ TODO: Stack doesn't support passing the compiler as a
      --  commandline option so we meddle with PATH instead. We should
      --  patch that upstream.

    , ghcProgram    :: !FilePath
    -- ^ The path to the @ghc@ program.

    , ghcPkgProgram :: !FilePath
    -- ^ The path to the @ghc-pkg@ program. If not changed it will be derived
    -- from the path to 'ghcProgram'.
    } deriving (Eq, Ord, Show, Read, Generic, Typeable)

-- | By default all programs use their unqualified names, i.e. they will be
-- searched for on @PATH@.
defaultPrograms :: Programs
defaultPrograms = Programs "cabal" [] []  "stack" [] [] [] "ghc" "ghc-pkg"

data EnvOverride
    = EnvPrepend String
    | EnvAppend String
    | EnvReplace String
      deriving (Eq, Ord, Show, Read, Generic, Typeable)

data CompileOptions = CompileOptions
    { oVerbose       :: Bool
    , oCabalPkgDb    :: Maybe PackageDbDir
    , oCabalVersion  :: Maybe Version
    , oPrograms      :: Programs
    }

oCabalProgram :: Env => FilePath
oCabalProgram = cabalProgram ?progs

defaultCompileOptions :: CompileOptions
defaultCompileOptions =
    CompileOptions False Nothing Nothing defaultPrograms

newtype PackageDbDir = PackageDbDir { unPackageDbDir :: FilePath }
    deriving (Show)
newtype PackageEnvFile = PackageEnvFile { unPackageEnvFile :: FilePath }
    deriving (Show)