module Distribution.Client.Dependency.Modular.IndexConversion
    ( convPIs
    ) where

import Data.List as L
import Data.Map as M
import Data.Maybe
import Data.Monoid as Mon
import Data.Set as S
import Prelude hiding (pi)

import qualified Distribution.Client.PackageIndex as CI
import Distribution.Client.Types
import Distribution.Client.ComponentDeps (Component(..))
import Distribution.Compiler
import Distribution.InstalledPackageInfo as IPI
import Distribution.Package                          -- from Cabal
import Distribution.PackageDescription as PD         -- from Cabal
import Distribution.PackageDescription.Configuration as PDC
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 loc) -> 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 _) | sip = (pn, i, PInfo fdeps fds (Just Shadowed))
    shadow x                                = x

-- | Convert a single installed package into the solver-specific format.
convIP :: SI.InstalledPackageIndex -> InstalledPackageInfo -> (PN, I, PInfo)
convIP idx ipi =
  case mapM (convIPId pn idx) (IPI.depends ipi) of
        Nothing  -> (pn, i, PInfo []            M.empty (Just Broken))
        Just fds -> (pn, i, PInfo (setComp fds) M.empty Nothing)
 where
  -- We assume that all dependencies of installed packages are _library_ deps
  ipid = IPI.installedUnitId ipi
  i = I (pkgVersion (sourcePackageId ipi)) (Inst ipid)
  pn = pkgName (sourcePackageId ipi)
  setComp = setCompFlaggedDeps (ComponentLib (unPackageName pn))
-- 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 -> UnitId -> Maybe (FlaggedDep () PN)
convIPId pn' idx ipid =
  case SI.lookupUnitId 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 cabal-install source package index to the simpler,
-- more uniform index format of the solver.
convSPI' :: OS -> Arch -> CompilerInfo -> Bool ->
            CI.PackageIndex (SourcePackage loc) -> [(PN, I, PInfo)]
convSPI' os arch cinfo strfl = L.map (convSP os arch cinfo strfl) . CI.allPackages

-- | Convert a single source package into the solver-specific format.
convSP :: OS -> Arch -> CompilerInfo -> Bool -> SourcePackage loc -> (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'.
convGPD :: OS -> Arch -> CompilerInfo -> Bool ->
           PI PN -> GenericPackageDescription -> PInfo
convGPD os arch cinfo strfl pi@(PI pn _)
        (GenericPackageDescription pkg flags libs exes tests benchs) =
  let
    fds  = flagInfo strfl flags

    -- | We have to be careful to filter out dependencies on
    -- internal libraries, since they don't refer to real packages
    -- and thus cannot actually be solved over.  We'll do this
    -- by creating a set of package names which are "internal"
    -- and dropping them as we convert.
    ipns = S.fromList [ PackageName nm
                      | (nm, _) <- libs
                      -- Don't include the true package name;
                      -- qualification could make this relevant.
                      -- TODO: Can we qualify over internal
                      -- dependencies? Not for now!
                      , PackageName nm /= pn ]

    conv :: Mon.Monoid a => Component -> (a -> BuildInfo) ->
            CondTree ConfVar [Dependency] a -> FlaggedDeps Component PN
    conv comp getInfo = convCondTree os arch cinfo pi fds comp getInfo ipns .
                        PDC.addBuildableCondition getInfo

    flagged_deps
        = concatMap (\(nm, ds) -> conv (ComponentLib nm)   libBuildInfo       ds) libs
       ++ concatMap (\(nm, ds) -> conv (ComponentExe nm)   buildInfo          ds) exes
       ++ prefix (Stanza (SN pi TestStanzas))
            (L.map  (\(nm, ds) -> conv (ComponentTest nm)  testBuildInfo      ds) tests)
       ++ prefix (Stanza (SN pi BenchStanzas))
            (L.map  (\(nm, ds) -> conv (ComponentBench nm) benchmarkBuildInfo ds) benchs)
       ++ maybe []    (convSetupBuildInfo pi)    (setupBuildInfo pkg)

  in
    PInfo flagged_deps fds Nothing

-- With convenience libraries, we have to do some work.  Imagine you
-- have the following Cabal file:
--
--      name: foo
--      library foo-internal
--          build-depends: external-a
--      library
--          build-depends: foo-internal, external-b
--      library foo-helper
--          build-depends: foo, external-c
--      test-suite foo-tests
--          build-depends: foo-helper, external-d
--
-- What should the final flagged dependency tree be?  Ideally, it
-- should look like this:
--
--      [ Simple (Dep external-a) (Library foo-internal)
--      , Simple (Dep external-b) (Library foo)
--      , Stanza (SN foo TestStanzas) $
--          [ Simple (Dep external-c) (Library foo-helper)
--          , Simple (Dep external-d) (TestSuite foo-tests) ]
--      ]
--
-- There are two things to note:
--
--      1. First, we eliminated the "local" dependencies foo-internal
--      and foo-helper.  This are implicitly assumed to refer to "foo"
--      so we don't need to have them around.  If you forget this,
--      Cabal will then try to pick a version for "foo-helper" but
--      no such package exists (this is the cost of overloading
--      build-depends to refer to both packages and components.)
--
--      2. Second, it is more precise to have external-c be qualified
--      by a test stanza, since foo-helper only needs to be built if
--      your are building the test suite (and not the main library).
--      If you omit it, Cabal will always attempt to depsolve for
--      foo-helper even if you aren't building the test suite.

-- | Create a flagged dependency tree from a list @fds@ of flagged
-- dependencies, using @f@ to form the tree node (@f@ will be
-- something like @Stanza sn@).
prefix :: (FlaggedDeps comp qpn -> FlaggedDep comp' qpn)
       -> [FlaggedDeps comp qpn] -> FlaggedDeps comp' 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))))

-- | Internal package names, which should not be interpreted as true
-- dependencies.
type IPNs = Set PN

-- | Convenience function to delete a 'FlaggedDep' if it's
-- for a 'PN' that isn't actually real.
filterIPNs :: IPNs -> Dependency -> FlaggedDep Component PN -> FlaggedDeps Component PN
filterIPNs ipns (Dependency pn _) fd
    | S.notMember pn ipns = [fd]
    | otherwise           = []

-- | Convert condition trees to flagged dependencies.  Mutually
-- recursive with 'convBranch'.  See 'convBranch' for an explanation
-- of all arguments preceeding the input 'CondTree'.
convCondTree :: OS -> Arch -> CompilerInfo -> PI PN -> FlagInfo ->
                Component ->
                (a -> BuildInfo) ->
                IPNs ->
                CondTree ConfVar [Dependency] a -> FlaggedDeps Component PN
convCondTree os arch cinfo pi@(PI pn _) fds comp getInfo ipns (CondNode info ds branches) =
                 concatMap
                    (\d -> filterIPNs ipns d (D.Simple (convDep pn d) comp))
                    ds  -- unconditional package dependencies
              ++ L.map (\e -> D.Simple (Ext  e) comp) (PD.allExtensions bi) -- unconditional extension dependencies
              ++ L.map (\l -> D.Simple (Lang l) comp) (PD.allLanguages  bi) -- unconditional language dependencies
              ++ L.map (\(Dependency pkn vr) -> D.Simple (Pkg pkn vr) comp) (PD.pkgconfigDepends bi) -- unconditional pkg-config dependencies
              ++ concatMap (convBranch os arch cinfo pi fds comp getInfo ipns) branches
  where
    bi = getInfo info

-- | Branch interpreter.  Mutually recursive with 'convCondTree'.
--
-- 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.
--
-- This function takes a number of arguments:
--
--      1. Some pre dependency-solving known information ('OS', 'Arch',
--         'CompilerInfo') for @os()@, @arch()@ and @impl()@ variables,
--
--      2. The package instance @'PI' 'PN'@ which this condition tree
--         came from, so that we can correctly associate @flag()@
--         variables with the correct package name qualifier,
--
--      3. The flag defaults 'FlagInfo' so that we can populate
--         'Flagged' dependencies with 'FInfo',
--
--      4. The name of the component 'Component' so we can record where
--         the fine-grained information about where the component came
--         from (see 'convCondTree'), and
--
--      5. A selector to extract the 'BuildInfo' from the leaves of
--         the 'CondTree' (which actually contains the needed
--         dependency information.)
--
--      6. The set of package names which should be considered internal
--         dependencies, and thus not handled as dependencies.
convBranch :: OS -> Arch -> CompilerInfo ->
              PI PN -> FlagInfo ->
              Component ->
              (a -> BuildInfo) ->
              IPNs ->
              (Condition ConfVar,
               CondTree ConfVar [Dependency] a,
               Maybe (CondTree ConfVar [Dependency] a)) -> FlaggedDeps Component PN
convBranch os arch cinfo pi@(PI pn _) fds comp getInfo ipns (c', t', mf') =
  go c' (          convCondTree os arch cinfo pi fds comp getInfo ipns   t')
        (maybe [] (convCondTree os arch cinfo pi fds comp getInfo ipns) mf')
  where
    go :: Condition ConfVar ->
          FlaggedDeps Component PN -> FlaggedDeps Component PN -> FlaggedDeps Component 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.
    --
    -- Note that we make assumptions here on the form of the dependencies that
    -- can occur at this point. In particular, no occurrences of Fixed, and no
    -- occurrences of multiple version ranges, as all dependencies below this
    -- point have been generated using 'convDep'.
    extractCommon :: FlaggedDeps Component PN -> FlaggedDeps Component PN -> FlaggedDeps Component PN
    extractCommon ps ps' = [ D.Simple (Dep pn1 (Constrained [(vr1 .||. vr2, Goal (P pn) [])])) comp
                           | D.Simple (Dep pn1 (Constrained [(vr1, _)])) _ <- ps
                           , D.Simple (Dep pn2 (Constrained [(vr2, _)])) _ <- ps'
                           , pn1 == pn2
                           ]

-- | 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 setup dependencies
convSetupBuildInfo :: PI PN -> SetupBuildInfo -> FlaggedDeps Component PN
convSetupBuildInfo (PI pn _i) nfo =
    L.map (\d -> D.Simple (convDep pn d) ComponentSetup) (PD.setupDepends nfo)