module Distribution.Client.Dependency.Modular.IndexConversion where

import Data.List as L
import Data.Map as M
import Data.Maybe
import Prelude hiding (pi)

import qualified Distribution.Client.PackageIndex as CI
import Distribution.Client.Types
import Distribution.Compiler
import Distribution.InstalledPackageInfo as IPI
import Distribution.Package                          -- from Cabal
import Distribution.PackageDescription as PD         -- from Cabal
import qualified Distribution.Simple.PackageIndex as SI
import Distribution.System

import Distribution.Client.Dependency.Modular.Dependency as D
import Distribution.Client.Dependency.Modular.Flag as F
import Distribution.Client.Dependency.Modular.Index
import Distribution.Client.Dependency.Modular.Package
import Distribution.Client.Dependency.Modular.Tree
import Distribution.Client.Dependency.Modular.Version

-- | Convert both the installed package index and the source package
-- index into one uniform solver index.
--
-- We use 'allPackagesBySourcePackageId' for the installed package index
-- because that returns us several instances of the same package and version
-- in order of preference. This allows us in principle to \"shadow\"
-- packages if there are several installed packages of the same version.
-- There are currently some shortcomings in both GHC and Cabal in
-- resolving these situations. However, the right thing to do is to
-- fix the problem there, so for now, shadowing is only activated if
-- explicitly requested.
convPIs :: OS -> Arch -> CompilerInfo -> Bool -> Bool ->
           SI.InstalledPackageIndex -> CI.PackageIndex SourcePackage -> Index
convPIs os arch comp sip strfl iidx sidx =
  mkIndex (convIPI' sip iidx ++ convSPI' os arch comp strfl sidx)

-- | Convert a Cabal installed package index to the simpler,
-- more uniform index format of the solver.
convIPI' :: Bool -> SI.InstalledPackageIndex -> [(PN, I, PInfo)]
convIPI' sip idx =
    -- apply shadowing whenever there are multiple installed packages with
    -- the same version
    [ maybeShadow (convIP idx pkg)
    | (_pkgid, pkgs) <- SI.allPackagesBySourcePackageId idx
    , (maybeShadow, pkg) <- zip (id : repeat shadow) pkgs ]
  where

    -- shadowing is recorded in the package info
    shadow (pn, i, PInfo fdeps fds encs _) | sip = (pn, i, PInfo fdeps fds encs (Just Shadowed))
    shadow x                                     = x

convIPI :: Bool -> SI.InstalledPackageIndex -> Index
convIPI sip = mkIndex . convIPI' sip

-- | Convert a single installed package into the solver-specific format.
convIP :: SI.InstalledPackageIndex -> InstalledPackageInfo -> (PN, I, PInfo)
convIP idx ipi =
  let ipid = IPI.installedPackageId ipi
      i = I (pkgVersion (sourcePackageId ipi)) (Inst ipid)
      pn = pkgName (sourcePackageId ipi)
  in  case mapM (convIPId pn idx) (IPI.depends ipi) of
        Nothing  -> (pn, i, PInfo [] M.empty [] (Just Broken))
        Just fds -> (pn, i, PInfo fds M.empty [] Nothing)
-- TODO: Installed packages should also store their encapsulations!

-- | Convert dependencies specified by an installed package id into
-- flagged dependencies of the solver.
--
-- May return Nothing if the package can't be found in the index. That
-- indicates that the original package having this dependency is broken
-- and should be ignored.
convIPId :: PN -> SI.InstalledPackageIndex -> InstalledPackageId -> Maybe (FlaggedDep PN)
convIPId pn' idx ipid =
  case SI.lookupInstalledPackageId idx ipid of
    Nothing  -> Nothing
    Just ipi -> let i = I (pkgVersion (sourcePackageId ipi)) (Inst ipid)
                    pn = pkgName (sourcePackageId ipi)
                in  Just (D.Simple (Dep pn (Fixed i (Goal (P pn') []))))

-- | Convert a epm source package index to the simpler,
-- more uniform index format of the solver.
convSPI' :: OS -> Arch -> CompilerInfo -> Bool ->
            CI.PackageIndex SourcePackage -> [(PN, I, PInfo)]
convSPI' os arch cinfo strfl = L.map (convSP os arch cinfo strfl) . CI.allPackages

convSPI :: OS -> Arch -> CompilerInfo -> Bool ->
           CI.PackageIndex SourcePackage -> Index
convSPI os arch cinfo strfl = mkIndex . convSPI' os arch cinfo strfl

-- | Convert a single source package into the solver-specific format.
convSP :: OS -> Arch -> CompilerInfo -> Bool -> SourcePackage -> (PN, I, PInfo)
convSP os arch cinfo strfl (SourcePackage (PackageIdentifier pn pv) gpd _ _pl) =
  let i = I pv InRepo
  in  (pn, i, convGPD os arch cinfo strfl (PI pn i) gpd)

-- We do not use 'flattenPackageDescription' or 'finalizePackageDescription'
-- from 'Distribution.PackageDescription.Configuration' here, because we
-- want to keep the condition tree, but simplify much of the test.

-- | Convert a generic package description to a solver-specific 'PInfo'.
--
-- TODO: We currently just take all dependencies from all specified library,
-- executable and test components. This does not quite seem fair.
convGPD :: OS -> Arch -> CompilerInfo -> Bool ->
           PI PN -> GenericPackageDescription -> PInfo
convGPD os arch comp strfl pi
        (GenericPackageDescription _ flags libs exes tests benchs) =
  let
    fds = flagInfo strfl flags
  in
    PInfo
      (maybe []    (convCondTree os arch comp pi fds (const True)          ) libs    ++
       concatMap   (convCondTree os arch comp pi fds (const True)     . snd) exes    ++
      prefix (Stanza (SN pi TestStanzas))
        (L.map     (convCondTree os arch comp pi fds (const True)     . snd) tests)  ++
      prefix (Stanza (SN pi BenchStanzas))
        (L.map     (convCondTree os arch comp pi fds (const True)     . snd) benchs))
      fds
      [] -- TODO: add encaps
      Nothing

prefix :: (FlaggedDeps qpn -> FlaggedDep qpn) -> [FlaggedDeps qpn] -> FlaggedDeps qpn
prefix _ []  = []
prefix f fds = [f (concat fds)]

-- | Convert flag information. Automatic flags are now considered weak
-- unless strong flags have been selected explicitly.
flagInfo :: Bool -> [PD.Flag] -> FlagInfo
flagInfo strfl = M.fromList . L.map (\ (MkFlag fn _ b m) -> (fn, FInfo b m (not (strfl || m))))

-- | Convert condition trees to flagged dependencies.
convCondTree :: OS -> Arch -> CompilerInfo -> PI PN -> FlagInfo ->
                (a -> Bool) -> -- how to detect if a branch is active
                CondTree ConfVar [Dependency] a -> FlaggedDeps PN
convCondTree os arch comp pi@(PI pn _) fds p (CondNode info ds branches)
  | p info    = L.map (D.Simple . convDep pn) ds  -- unconditional dependencies
              ++ concatMap (convBranch os arch comp pi fds p) branches
  | otherwise = []

-- | Branch interpreter.
--
-- Here, we try to simplify one of Cabal's condition tree branches into the
-- solver's flagged dependency format, which is weaker. Condition trees can
-- contain complex logical expression composed from flag choices and special
-- flags (such as architecture, or compiler flavour). We try to evaluate the
-- special flags and subsequently simplify to a tree that only depends on
-- simple flag choices.
convBranch :: OS -> Arch -> CompilerInfo ->
              PI PN -> FlagInfo ->
              (a -> Bool) -> -- how to detect if a branch is active
              (Condition ConfVar,
               CondTree ConfVar [Dependency] a,
               Maybe (CondTree ConfVar [Dependency] a)) -> FlaggedDeps PN
convBranch os arch cinfo pi fds p (c', t', mf') =
  go c' (          convCondTree os arch cinfo pi fds p   t')
        (maybe [] (convCondTree os arch cinfo pi fds p) mf')
  where
    go :: Condition ConfVar ->
          FlaggedDeps PN -> FlaggedDeps PN -> FlaggedDeps PN
    go (Lit True)  t _ = t
    go (Lit False) _ f = f
    go (CNot c)    t f = go c f t
    go (CAnd c d)  t f = go c (go d t f) f
    go (COr  c d)  t f = go c t (go d t f)
    go (Var (Flag fn)) t f = extractCommon t f ++ [Flagged (FN pi fn) (fds ! fn) t f]
    go (Var (OS os')) t f
      | os == os'      = t
      | otherwise      = f
    go (Var (Arch arch')) t f
      | arch == arch'  = t
      | otherwise      = f
    go (Var (Impl cf cvr)) t f
      | matchImpl (compilerInfoId cinfo) ||
            -- fixme: Nothing should be treated as unknown, rather than empty
            --        list. This code should eventually be changed to either
            --        support partial resolution of compiler flags or to
            --        complain about incompletely configured compilers.
        any matchImpl (fromMaybe [] $ compilerInfoCompat cinfo) = t
      | otherwise      = f
      where
        matchImpl (CompilerId cf' cv) = cf == cf' && checkVR cvr cv

    -- If both branches contain the same package as a simple dep, we lift it to
    -- the next higher-level, but without constraints. This heuristic together
    -- with deferring flag choices will then usually first resolve this package,
    -- and try an already installed version before imposing a default flag choice
    -- that might not be what we want.
    extractCommon :: FlaggedDeps PN -> FlaggedDeps PN -> FlaggedDeps PN
    extractCommon ps ps' = [ D.Simple (Dep pn (Constrained [])) | D.Simple (Dep pn _) <- ps, D.Simple (Dep pn' _) <- ps', pn == pn' ]

-- | Convert a Cabal dependency to a solver-specific dependency.
convDep :: PN -> Dependency -> Dep PN
convDep pn' (Dependency pn vr) = Dep pn (Constrained [(vr, Goal (P pn') [])])

-- | Convert a Cabal package identifier to a solver-specific dependency.
convPI :: PN -> PackageIdentifier -> Dep PN
convPI pn' (PackageIdentifier pn v) = Dep pn (Constrained [(eqVR v, Goal (P pn') [])])
