module Distribution.Solver.Types.DependencyResolver
    ( DependencyResolver
    ) where

import Data.Set (Set)

import Distribution.Solver.Types.LabeledPackageConstraint
import Distribution.Solver.Types.PkgConfigDb ( PkgConfigDb )
import Distribution.Solver.Types.PackagePreferences
import Distribution.Solver.Types.PackageIndex ( PackageIndex )
import Distribution.Solver.Types.Progress
import Distribution.Solver.Types.ResolverPackage
import Distribution.Solver.Types.SourcePackage

import Distribution.Simple.PackageIndex ( InstalledPackageIndex )
import Distribution.Package ( PackageName )
import Distribution.Compiler ( CompilerInfo )
import Distribution.System ( Platform )

-- | A dependency resolver is a function that works out an installation plan
-- given the set of installed and available packages and a set of deps to
-- solve for.
--
-- The reason for this interface is because there are dozens of approaches to
-- solving the package dependency problem and we want to make it easy to swap
-- in alternatives.
--
type DependencyResolver loc = Platform
                           -> CompilerInfo
                           -> InstalledPackageIndex
                           -> PackageIndex (SourcePackage loc)
                           -> PkgConfigDb
                           -> (PackageName -> PackagePreferences)
                           -> [LabeledPackageConstraint]
                           -> Set PackageName
                           -> Progress String String [ResolverPackage loc]