-- | See <https://github.com/ezyang/ghc-proposals/blob/backpack/proposals/0000-backpack.rst>
module Distribution.Backpack.ComponentsGraph (
    ComponentsGraph,
    ComponentsWithDeps,
    mkComponentsGraph,
    componentsGraphToList,
    dispComponentsWithDeps,
    componentCycleMsg
) where

import Prelude ()
import Distribution.Compat.Prelude

import Distribution.Package
import Distribution.PackageDescription
import Distribution.Simple.BuildToolDepends
import Distribution.Simple.LocalBuildInfo
import Distribution.Types.ComponentRequestedSpec
import Distribution.Compat.Graph (Graph, Node(..))
import qualified Distribution.Compat.Graph as Graph
import qualified Distribution.Compat.NonEmptySet as NES
import Distribution.Utils.Generic

import Distribution.Pretty (pretty)
import Text.PrettyPrint

------------------------------------------------------------------------------
-- Components graph
------------------------------------------------------------------------------

-- | A graph of source-level components by their source-level
-- dependencies
--
type ComponentsGraph = Graph (Node ComponentName Component)

-- | A list of components associated with the source level
-- dependencies between them.
--
type ComponentsWithDeps = [(Component, [ComponentName])]

-- | Pretty-print 'ComponentsWithDeps'.
--
dispComponentsWithDeps :: ComponentsWithDeps -> Doc
dispComponentsWithDeps :: ComponentsWithDeps -> Doc
dispComponentsWithDeps ComponentsWithDeps
graph =
    [Doc] -> Doc
vcat [ Doc -> Int -> Doc -> Doc
hang (String -> Doc
text String
"component" Doc -> Doc -> Doc
<+> ComponentName -> Doc
forall a. Pretty a => a -> Doc
pretty (Component -> ComponentName
componentName Component
c)) Int
4
                ([Doc] -> Doc
vcat [ String -> Doc
text String
"dependency" Doc -> Doc -> Doc
<+> ComponentName -> Doc
forall a. Pretty a => a -> Doc
pretty ComponentName
cdep | ComponentName
cdep <- [ComponentName]
cdeps ])
         | (Component
c, [ComponentName]
cdeps) <- ComponentsWithDeps
graph ]

-- | Create a 'Graph' of 'Component', or report a cycle if there is a
-- problem.
--
mkComponentsGraph :: ComponentRequestedSpec
                  -> PackageDescription
                  -> Either [ComponentName] ComponentsGraph
mkComponentsGraph :: ComponentRequestedSpec
-> PackageDescription -> Either [ComponentName] ComponentsGraph
mkComponentsGraph ComponentRequestedSpec
enabled PackageDescription
pkg_descr =
    let g :: ComponentsGraph
g = [Node ComponentName Component] -> ComponentsGraph
forall a. (IsNode a, Show (Key a)) => [a] -> Graph a
Graph.fromDistinctList
                           [ Component
-> ComponentName -> [ComponentName] -> Node ComponentName Component
forall k a. a -> k -> [k] -> Node k a
N Component
c (Component -> ComponentName
componentName Component
c) (Component -> [ComponentName]
componentDeps Component
c)
                           | Component
c <- PackageDescription -> [Component]
pkgBuildableComponents PackageDescription
pkg_descr
                           , ComponentRequestedSpec -> Component -> Bool
componentEnabled ComponentRequestedSpec
enabled Component
c ]
    in case ComponentsGraph -> [[Node ComponentName Component]]
forall a. Graph a -> [[a]]
Graph.cycles ComponentsGraph
g of
          []     -> ComponentsGraph -> Either [ComponentName] ComponentsGraph
forall a b. b -> Either a b
Right ComponentsGraph
g
          [[Node ComponentName Component]]
ccycles -> [ComponentName] -> Either [ComponentName] ComponentsGraph
forall a b. a -> Either a b
Left  [ Component -> ComponentName
componentName Component
c | N Component
c ComponentName
_ [ComponentName]
_ <- [[Node ComponentName Component]] -> [Node ComponentName Component]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat [[Node ComponentName Component]]
ccycles ]
  where
    -- The dependencies for the given component
    componentDeps :: Component -> [ComponentName]
componentDeps Component
component =
        [ComponentName]
toolDependencies [ComponentName] -> [ComponentName] -> [ComponentName]
forall a. [a] -> [a] -> [a]
++ [ComponentName]
libDependencies
      where
        bi :: BuildInfo
bi = Component -> BuildInfo
componentBuildInfo Component
component

        toolDependencies :: [ComponentName]
toolDependencies = UnqualComponentName -> ComponentName
CExeName (UnqualComponentName -> ComponentName)
-> [UnqualComponentName] -> [ComponentName]
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> PackageDescription -> BuildInfo -> [UnqualComponentName]
getAllInternalToolDependencies PackageDescription
pkg_descr BuildInfo
bi

        libDependencies :: [ComponentName]
libDependencies = do
            Dependency PackageName
pkgname VersionRange
_ NonEmptySet LibraryName
lns <- BuildInfo -> [Dependency]
targetBuildDepends BuildInfo
bi
            Bool -> [()]
forall (f :: * -> *). Alternative f => Bool -> f ()
guard (PackageName
pkgname PackageName -> PackageName -> Bool
forall a. Eq a => a -> a -> Bool
== PackageDescription -> PackageName
forall pkg. Package pkg => pkg -> PackageName
packageName PackageDescription
pkg_descr)

            LibraryName
ln <- NonEmptySet LibraryName -> [LibraryName]
forall a. NonEmptySet a -> [a]
NES.toList NonEmptySet LibraryName
lns
            ComponentName -> [ComponentName]
forall a. a -> [a]
forall (m :: * -> *) a. Monad m => a -> m a
return (LibraryName -> ComponentName
CLibName LibraryName
ln)

-- | Given the package description and a 'PackageDescription' (used
-- to determine if a package name is internal or not), sort the
-- components in dependency order (fewest dependencies first).  This is
-- NOT necessarily the build order (although it is in the absence of
-- Backpack.)
--
componentsGraphToList :: ComponentsGraph
                      -> ComponentsWithDeps
componentsGraphToList :: ComponentsGraph -> ComponentsWithDeps
componentsGraphToList =
    (Node ComponentName Component -> (Component, [ComponentName]))
-> [Node ComponentName Component] -> ComponentsWithDeps
forall a b. (a -> b) -> [a] -> [b]
map (\(N Component
c ComponentName
_ [ComponentName]
cs) -> (Component
c, [ComponentName]
cs)) ([Node ComponentName Component] -> ComponentsWithDeps)
-> (ComponentsGraph -> [Node ComponentName Component])
-> ComponentsGraph
-> ComponentsWithDeps
forall b c a. (b -> c) -> (a -> b) -> a -> c
. ComponentsGraph -> [Node ComponentName Component]
forall a. Graph a -> [a]
Graph.revTopSort

-- | Error message when there is a cycle; takes the SCC of components.
componentCycleMsg :: PackageIdentifier -> [ComponentName] -> Doc
componentCycleMsg :: PackageIdentifier -> [ComponentName] -> Doc
componentCycleMsg PackageIdentifier
pn [ComponentName]
cnames =
    String -> Doc
text String
"Components in the package" Doc -> Doc -> Doc
<+> PackageIdentifier -> Doc
forall a. Pretty a => a -> Doc
pretty PackageIdentifier
pn Doc -> Doc -> Doc
<+> String -> Doc
text String
"depend on each other in a cyclic way:"
    Doc -> Doc -> Doc
$$
    String -> Doc
text (String -> [String] -> String
forall a. [a] -> [[a]] -> [a]
intercalate String
" depends on "
            [ String
"'" String -> String -> String
forall a. [a] -> [a] -> [a]
++ ComponentName -> String
showComponentName ComponentName
cname String -> String -> String
forall a. [a] -> [a] -> [a]
++ String
"'"
            | ComponentName
cname <- [ComponentName]
cnames [ComponentName] -> [ComponentName] -> [ComponentName]
forall a. [a] -> [a] -> [a]
++ Maybe ComponentName -> [ComponentName]
forall a. Maybe a -> [a]
maybeToList ([ComponentName] -> Maybe ComponentName
forall a. [a] -> Maybe a
safeHead [ComponentName]
cnames) ])