-----------------------------------------------------------------------------
-- |
-- Module      :  Distribution.Simple.PackageIndex
-- Copyright   :  (c) David Himmelstrup 2005,
--                    Bjorn Bringert 2007,
--                    Duncan Coutts 2008-2009
--
-- Maintainer  :  cabal-devel@haskell.org
-- Portability :  portable
--
-- An index of packages.
--
module Distribution.Simple.PackageIndex (
  -- * Package index data type
  PackageIndex,

  -- * Creating an index
  fromList,

  -- * Updates
  merge,

  insert,

  deleteInstalledPackageId,
  deleteSourcePackageId,
  deletePackageName,
--  deleteDependency,

  -- * Queries

  -- ** Precise lookups
  lookupInstalledPackageId,
  lookupSourcePackageId,
  lookupPackageName,
  lookupDependency,

  -- ** Case-insensitive searches
  searchByName,
  SearchResult(..),
  searchByNameSubstring,

  -- ** Bulk queries
  allPackages,
  allPackagesByName,

  -- ** Special queries
  brokenPackages,
  dependencyClosure,
  reverseDependencyClosure,
  topologicalOrder,
  reverseTopologicalOrder,
  dependencyInconsistencies,
  dependencyCycles,
  dependencyGraph,
  moduleNameIndex,
  ) where

import Prelude hiding (lookup)
import Control.Exception (assert)
import qualified Data.Map as Map
import Data.Map (Map)
import qualified Data.Tree  as Tree
import qualified Data.Graph as Graph
import qualified Data.Array as Array
import Data.Array ((!))
import Data.List as List
         ( null, foldl', sort
         , groupBy, sortBy, find, isInfixOf, nubBy, deleteBy, deleteFirstsBy )
import Data.Monoid (Monoid(..))
import Data.Maybe (isNothing, fromMaybe)

import Distribution.Package
         ( PackageName(..), PackageId
         , Package(..), packageName, packageVersion
         , Dependency(Dependency)--, --PackageFixedDeps(..)
         , InstalledPackageId(..) )
import Distribution.ModuleName
         ( ModuleName )
import Distribution.InstalledPackageInfo
         ( InstalledPackageInfo, installedPackageId )
import qualified Distribution.InstalledPackageInfo as IPI
import Distribution.Version
         ( Version, withinRange )
import Distribution.Simple.Utils (lowercase, comparing, equating)


-- | The collection of information about packages from one or more 'PackageDB's.
--
-- Packages are uniquely identified in by their 'InstalledPackageId', they can
-- also be effeciently looked up by package name or by name and version.
--
data PackageIndex = PackageIndex
  -- The primary index. Each InstalledPackageInfo record is uniquely identified
  -- by its InstalledPackageId.
  --
  !(Map InstalledPackageId InstalledPackageInfo)

  -- This auxillary index maps package names (case-sensitively) to all the
  -- versions and instances of that package. This allows us to find all
  -- versions satisfying a dependency.
  --
  -- It is a three-level index. The first level is the package name,
  -- the second is the package version and the final level is instances
  -- of the same package version. These are unique by InstalledPackageId
  -- and are kept in preference order.
  --
  !(Map PackageName (Map Version [InstalledPackageInfo]))

  deriving (Show, Read)

instance Monoid PackageIndex where
  mempty  = PackageIndex Map.empty Map.empty
  mappend = merge
  --save one mappend with empty in the common case:
  mconcat [] = mempty
  mconcat xs = foldr1 mappend xs

invariant :: PackageIndex -> Bool
invariant (PackageIndex pids pnames) =
     map installedPackageId (Map.elems pids)
  == sort
     [ assert pinstOk (installedPackageId pinst)
     | (pname, pvers)  <- Map.toList pnames
     , let pversOk = not (Map.null pvers)
     , (pver,  pinsts) <- assert pversOk $ Map.toList pvers
     , let pinsts'  = sortBy (comparing installedPackageId) pinsts
           pinstsOk = all (\g -> length g == 1)
                          (groupBy (equating installedPackageId) pinsts')
     , pinst           <- assert pinstsOk $ pinsts'
     , let pinstOk = packageName    pinst == pname
                  && packageVersion pinst == pver
     ]


--
-- * Internal helpers
--

mkPackageIndex :: Map InstalledPackageId InstalledPackageInfo
               -> Map PackageName (Map Version [InstalledPackageInfo])
               -> PackageIndex
mkPackageIndex pids pnames = assert (invariant index) index
  where index = PackageIndex pids pnames


--
-- * Construction
--

-- | Build an index out of a bunch of packages.
--
-- If there are duplicates by 'InstalledPackageId' then later ones mask earlier
-- ones.
--
fromList :: [InstalledPackageInfo] -> PackageIndex
fromList pkgs = mkPackageIndex pids pnames
  where
    pids      = Map.fromList [ (installedPackageId pkg, pkg) | pkg <- pkgs ]
    pnames    =
      Map.fromList
        [ (packageName (head pkgsN), pvers)
        | pkgsN <- groupBy (equating  packageName)
                 . sortBy  (comparing packageId)
                 $ pkgs
        , let pvers =
                Map.fromList
                [ (packageVersion (head pkgsNV),
                   nubBy (equating installedPackageId) (reverse pkgsNV))
                | pkgsNV <- groupBy (equating packageVersion) pkgsN
                ]
        ]

--
-- * Updates
--

-- | Merge two indexes.
--
-- Packages from the second mask packages from the first if they have the exact
-- same 'InstalledPackageId'.
--
-- For packages with the same source 'PackageId', packages from the second are
-- \"preferred\" over those from the first. Being preferred means they are top
-- result when we do a lookup by source 'PackageId'. This is the mechanism we
-- use to prefer user packages over global packages.
--
merge :: PackageIndex -> PackageIndex -> PackageIndex
merge (PackageIndex pids1 pnames1) (PackageIndex pids2 pnames2) =
  mkPackageIndex (Map.union pids1 pids2)
                 (Map.unionWith (Map.unionWith mergeBuckets) pnames1 pnames2)
  where
    -- Packages in the second list mask those in the first, however preferred
    -- packages go first in the list.
    mergeBuckets xs ys = ys ++ (xs \\ ys)
    (\\) = deleteFirstsBy (equating installedPackageId)


-- | Inserts a single package into the index.
--
-- This is equivalent to (but slightly quicker than) using 'mappend' or
-- 'merge' with a singleton index.
--
insert :: InstalledPackageInfo -> PackageIndex -> PackageIndex
insert pkg (PackageIndex pids pnames) =
    mkPackageIndex pids' pnames'

  where
    pids'   = Map.insert (installedPackageId pkg) pkg pids
    pnames' = insertPackageName pnames
    insertPackageName =
      Map.insertWith' (\_ -> insertPackageVersion)
                     (packageName pkg)
                     (Map.singleton (packageVersion pkg) [pkg])

    insertPackageVersion =
      Map.insertWith' (\_ -> insertPackageInstance)
                     (packageVersion pkg) [pkg]

    insertPackageInstance pkgs =
      pkg : deleteBy (equating installedPackageId) pkg pkgs


-- | Removes a single installed package from the index.
--
deleteInstalledPackageId :: InstalledPackageId -> PackageIndex -> PackageIndex
deleteInstalledPackageId ipkgid original@(PackageIndex pids pnames) =
  case Map.updateLookupWithKey (\_ _ -> Nothing) ipkgid pids of
    (Nothing,     _)     -> original
    (Just spkgid, pids') -> mkPackageIndex pids'
                                          (deletePkgName spkgid pnames)

  where
    deletePkgName spkgid =
      Map.update (deletePkgVersion spkgid) (packageName spkgid)

    deletePkgVersion spkgid =
        (\m -> if Map.null m then Nothing else Just m)
      . Map.update deletePkgInstance (packageVersion spkgid)

    deletePkgInstance =
        (\xs -> if List.null xs then Nothing else Just xs)
      . List.deleteBy (\_ pkg -> installedPackageId pkg == ipkgid) undefined


-- | Removes all packages with this source 'PackageId' from the index.
--
deleteSourcePackageId :: PackageId -> PackageIndex -> PackageIndex
deleteSourcePackageId pkgid original@(PackageIndex pids pnames) =
  case Map.lookup (packageName pkgid) pnames of
    Nothing     -> original
    Just pvers  -> case Map.lookup (packageVersion pkgid) pvers of
      Nothing   -> original
      Just pkgs -> mkPackageIndex
                     (foldl' (flip (Map.delete . installedPackageId)) pids pkgs)
                     (deletePkgName pnames)
  where
    deletePkgName =
      Map.update deletePkgVersion (packageName pkgid)

    deletePkgVersion =
        (\m -> if Map.null m then Nothing else Just m)
      . Map.delete (packageVersion pkgid)


-- | Removes all packages with this (case-sensitive) name from the index.
--
deletePackageName :: PackageName -> PackageIndex -> PackageIndex
deletePackageName name original@(PackageIndex pids pnames) =
  case Map.lookup name pnames of
    Nothing     -> original
    Just pvers  -> mkPackageIndex
                     (foldl' (flip (Map.delete . installedPackageId)) pids
                             (concat (Map.elems pvers)))
                     (Map.delete name pnames)

{-
-- | Removes all packages satisfying this dependency from the index.
--
deleteDependency :: Dependency -> PackageIndex -> PackageIndex
deleteDependency (Dependency name verstionRange) =
  delete' name (\pkg -> packageVersion pkg `withinRange` verstionRange)
-}

--
-- * Bulk queries
--

-- | Get all the packages from the index.
--
allPackages :: PackageIndex -> [InstalledPackageInfo]
allPackages (PackageIndex pids _) = Map.elems pids

-- | Get all the packages from the index.
--
-- They are grouped by package name, case-sensitively.
--
allPackagesByName :: PackageIndex -> [[InstalledPackageInfo]]
allPackagesByName (PackageIndex _ pnames) =
  concatMap Map.elems (Map.elems pnames)

--
-- * Lookups
--

-- | Does a lookup by source package id (name & version).
--
-- Since multiple package DBs mask each other by 'InstalledPackageId',
-- then we get back at most one package.
--
lookupInstalledPackageId :: PackageIndex -> InstalledPackageId
                         -> Maybe InstalledPackageInfo
lookupInstalledPackageId (PackageIndex pids _) pid = Map.lookup pid pids


-- | Does a lookup by source package id (name & version).
--
-- There can be multiple installed packages with the same source 'PackageId'
-- but different 'InstalledPackageId'. They are returned in order of
-- preference, with the most preferred first.
--
lookupSourcePackageId :: PackageIndex -> PackageId -> [InstalledPackageInfo]
lookupSourcePackageId (PackageIndex _ pnames) pkgid =
  case Map.lookup (packageName pkgid) pnames of
    Nothing     -> []
    Just pvers  -> case Map.lookup (packageVersion pkgid) pvers of
      Nothing   -> []
      Just pkgs -> pkgs -- in preference order


-- | Does a lookup by source package name.
--
lookupPackageName :: PackageIndex -> PackageName
                  -> [(Version, [InstalledPackageInfo])]
lookupPackageName (PackageIndex _ pnames) name =
  case Map.lookup name pnames of
    Nothing     -> []
    Just pvers  -> Map.toList pvers


-- | Does a lookup by source package name and a range of versions.
--
-- We get back any number of versions of the specified package name, all
-- satisfying the version range constraint.
--
lookupDependency :: PackageIndex -> Dependency
                 -> [(Version, [InstalledPackageInfo])]
lookupDependency (PackageIndex _ pnames) (Dependency name versionRange) =
  case Map.lookup name pnames of
    Nothing    -> []
    Just pvers -> [ entry
                  | entry@(ver, _) <- Map.toList pvers
                  , ver `withinRange` versionRange ]

--
-- * Case insensitive name lookups
--

-- | Does a case-insensitive search by package name.
--
-- If there is only one package that compares case-insentiviely to this name
-- then the search is unambiguous and we get back all versions of that package.
-- If several match case-insentiviely but one matches exactly then it is also
-- unambiguous.
--
-- If however several match case-insentiviely and none match exactly then we
-- have an ambiguous result, and we get back all the versions of all the
-- packages. The list of ambiguous results is split by exact package name. So
-- it is a non-empty list of non-empty lists.
--
searchByName :: PackageIndex -> String -> SearchResult [InstalledPackageInfo]
searchByName (PackageIndex _ pnames) name =
  case [ pkgs | pkgs@(PackageName name',_) <- Map.toList pnames
              , lowercase name' == lname ] of
    []               -> None
    [(_,pvers)]      -> Unambiguous (concat (Map.elems pvers))
    pkgss            -> case find ((PackageName name==) . fst) pkgss of
      Just (_,pvers) -> Unambiguous (concat (Map.elems pvers))
      Nothing        -> Ambiguous (map (concat . Map.elems . snd) pkgss)
  where lname = lowercase name

data SearchResult a = None | Unambiguous a | Ambiguous [a]

-- | Does a case-insensitive substring search by package name.
--
-- That is, all packages that contain the given string in their name.
--
searchByNameSubstring :: PackageIndex -> String -> [InstalledPackageInfo]
searchByNameSubstring (PackageIndex _ pnames) searchterm =
  [ pkg
  | (PackageName name, pvers) <- Map.toList pnames
  , lsearchterm `isInfixOf` lowercase name
  , pkgs <- Map.elems pvers
  , pkg <- pkgs ]
  where lsearchterm = lowercase searchterm


--
-- * Special queries
--

-- None of the stuff below depends on the internal representation of the index.
--

-- | Find if there are any cycles in the dependency graph. If there are no
-- cycles the result is @[]@.
--
-- This actually computes the strongly connected components. So it gives us a
-- list of groups of packages where within each group they all depend on each
-- other, directly or indirectly.
--
dependencyCycles :: PackageIndex -> [[InstalledPackageInfo]]
dependencyCycles index =
  [ vs | Graph.CyclicSCC vs <- Graph.stronglyConnComp adjacencyList ]
  where
    adjacencyList = [ (pkg, installedPackageId pkg, IPI.depends pkg)
                    | pkg <- allPackages index ]


-- | All packages that have immediate dependencies that are not in the index.
--
-- Returns such packages along with the dependencies that they're missing.
--
brokenPackages :: PackageIndex -> [(InstalledPackageInfo, [InstalledPackageId])]
brokenPackages index =
  [ (pkg, missing)
  | pkg  <- allPackages index
  , let missing = [ pkg' | pkg' <- IPI.depends pkg
                         , isNothing (lookupInstalledPackageId index pkg') ]
  , not (null missing) ]


-- | Tries to take the transitive closure of the package dependencies.
--
-- If the transitive closure is complete then it returns that subset of the
-- index. Otherwise it returns the broken packages as in 'brokenPackages'.
--
-- * Note that if the result is @Right []@ it is because at least one of
-- the original given 'PackageId's do not occur in the index.
--
dependencyClosure :: PackageIndex
                  -> [InstalledPackageId]
                  -> Either PackageIndex
                            [(InstalledPackageInfo, [InstalledPackageId])]
dependencyClosure index pkgids0 = case closure mempty [] pkgids0 of
  (completed, []) -> Left completed
  (completed, _)  -> Right (brokenPackages completed)
 where
    closure completed failed []             = (completed, failed)
    closure completed failed (pkgid:pkgids) = case lookupInstalledPackageId index pkgid of
      Nothing   -> closure completed (pkgid:failed) pkgids
      Just pkg  -> case lookupInstalledPackageId completed (installedPackageId pkg) of
        Just _  -> closure completed  failed pkgids
        Nothing -> closure completed' failed pkgids'
          where completed' = insert pkg completed
                pkgids'    = IPI.depends pkg ++ pkgids

-- | Takes the transitive closure of the packages reverse dependencies.
--
-- * The given 'PackageId's must be in the index.
--
reverseDependencyClosure :: PackageIndex
                         -> [InstalledPackageId]
                         -> [InstalledPackageInfo]
reverseDependencyClosure index =
    map vertexToPkg
  . concatMap Tree.flatten
  . Graph.dfs reverseDepGraph
  . map (fromMaybe noSuchPkgId . pkgIdToVertex)

  where
    (depGraph, vertexToPkg, pkgIdToVertex) = dependencyGraph index
    reverseDepGraph = Graph.transposeG depGraph
    noSuchPkgId = error "reverseDependencyClosure: package is not in the graph"

topologicalOrder :: PackageIndex -> [InstalledPackageInfo]
topologicalOrder index = map toPkgId
                       . Graph.topSort
                       $ graph
  where (graph, toPkgId, _) = dependencyGraph index

reverseTopologicalOrder :: PackageIndex -> [InstalledPackageInfo]
reverseTopologicalOrder index = map toPkgId
                              . Graph.topSort
                              . Graph.transposeG
                              $ graph
  where (graph, toPkgId, _) = dependencyGraph index

-- | Builds a graph of the package dependencies.
--
-- Dependencies on other packages that are not in the index are discarded.
-- You can check if there are any such dependencies with 'brokenPackages'.
--
dependencyGraph :: PackageIndex
                -> (Graph.Graph,
                    Graph.Vertex -> InstalledPackageInfo,
                    InstalledPackageId -> Maybe Graph.Vertex)
dependencyGraph index = (graph, vertex_to_pkg, id_to_vertex)
  where
    graph = Array.listArray bounds
              [ [ v | Just v <- map id_to_vertex (IPI.depends pkg) ]
              | pkg <- pkgs ]

    pkgs             = sortBy (comparing packageId) (allPackages index)
    vertices         = zip (map installedPackageId pkgs) [0..]
    vertex_map       = Map.fromList vertices
    id_to_vertex pid = Map.lookup pid vertex_map

    vertex_to_pkg vertex = pkgTable ! vertex

    pkgTable   = Array.listArray bounds pkgs
    topBound = length pkgs - 1
    bounds = (0, topBound)

-- | Given a package index where we assume we want to use all the packages
-- (use 'dependencyClosure' if you need to get such a index subset) find out
-- if the dependencies within it use consistent versions of each package.
-- Return all cases where multiple packages depend on different versions of
-- some other package.
--
-- Each element in the result is a package name along with the packages that
-- depend on it and the versions they require. These are guaranteed to be
-- distinct.
--
dependencyInconsistencies :: PackageIndex
                          -> [(PackageName, [(PackageId, Version)])]
dependencyInconsistencies index =
  [ (name, [ (pid,packageVersion dep) | (dep,pids) <- uses, pid <- pids])
  | (name, ipid_map) <- Map.toList inverseIndex
  , let uses = Map.elems ipid_map
  , reallyIsInconsistent (map fst uses) ]

  where -- for each PackageName,
        --   for each package with that name,
        --     the InstalledPackageInfo and the package Ids of packages
        --     that depend on it.
        inverseIndex :: Map PackageName
                            (Map InstalledPackageId
                                 (InstalledPackageInfo, [PackageId]))
        inverseIndex = Map.fromListWith (Map.unionWith (\(a,b) (_,b') -> (a,b++b')))
          [ (packageName dep,
             Map.fromList [(ipid,(dep,[packageId pkg]))])
          | pkg <- allPackages index
          , ipid <- IPI.depends pkg
          , Just dep <- [lookupInstalledPackageId index ipid]
          ]

        reallyIsInconsistent :: [InstalledPackageInfo] -> Bool
        reallyIsInconsistent []       = False
        reallyIsInconsistent [_p]     = False
        reallyIsInconsistent [p1, p2] =
             installedPackageId p1 `notElem` IPI.depends p2
          && installedPackageId p2 `notElem` IPI.depends p1
        reallyIsInconsistent _ = True


moduleNameIndex :: PackageIndex -> Map ModuleName [InstalledPackageInfo]
moduleNameIndex index =
  Map.fromListWith (++)
    [ (moduleName, [pkg])
    | pkg        <- allPackages index
    , moduleName <- IPI.exposedModules pkg ]
