Synnefo » snf-ganeti » ganeti-local

    , compareNameComponent

    , prefixMatch

    , LookupResult(..)

    , MatchPriority(..)

import Data.Function

import Ganeti.HTools.Utils

-- | The priority of a match in a lookup result.

data MatchPriority = ExactMatch

                   | MultipleMatch

                   | PartialMatch

                   | FailMatch

                   deriving (Show, Read, Enum, Eq, Ord)

-- | The result of a name lookup in a list.

data LookupResult = LookupResult

    { lrMatchPriority :: MatchPriority -- ^ The result type

    -- | Matching value (for ExactMatch, PartialMatch), Lookup string otherwise

    , lrContent :: String

    } deriving (Show, Read)

-- | Lookup results have an absolute preference ordering.

instance Eq LookupResult where

  (==) = (==) `on` lrMatchPriority

instance Ord LookupResult where

  compare = compare `on` lrMatchPriority

-- | Check for prefix matches in names.

-- Implemented in Ganeti core utils.text.MatchNameComponent

-- as the regexp r"^%s(\..*)?$" % re.escape(key)

prefixMatch :: String  -- ^ Lookup

            -> String  -- ^ Full name

            -> Bool    -- ^ Whether there is a prefix match

prefixMatch lkp = isPrefixOf (lkp ++ ".")

-- | Is the lookup priority a "good" one?

goodMatchPriority :: MatchPriority -> Bool

goodMatchPriority ExactMatch = True

goodMatchPriority PartialMatch = True

goodMatchPriority _ = False

-- | Is the lookup result an actual match?

goodLookupResult :: LookupResult -> Bool

goodLookupResult = goodMatchPriority . lrMatchPriority

-- | Compares a canonical name and a lookup string.

compareNameComponent :: String        -- ^ Canonical (target) name

                     -> String        -- ^ Partial (lookup) name

                     -> LookupResult  -- ^ Result of the lookup

compareNameComponent cnl lkp =

  select (LookupResult FailMatch lkp)

  [ (cnl == lkp          , LookupResult ExactMatch cnl)

  , (prefixMatch lkp cnl , LookupResult PartialMatch cnl)

  ]

-- | Lookup a string and choose the best result.

chooseLookupResult :: String       -- ^ Lookup key

                   -> String       -- ^ String to compare to the lookup key

                   -> LookupResult -- ^ Previous result

                   -> LookupResult -- ^ New result

chooseLookupResult lkp cstr old =

  -- default: use class order to pick the minimum result

  select (min new old)

  -- special cases:

  -- short circuit if the new result is an exact match

  [ ((lrMatchPriority new) == ExactMatch, new)

  -- if both are partial matches generate a multiple match

  , (partial2, LookupResult MultipleMatch lkp)

  ] where new = compareNameComponent cstr lkp

          partial2 = all ((PartialMatch==) . lrMatchPriority) [old, new]

-- | Find the canonical name for a lookup string in a list of names.

lookupName :: [String]      -- ^ List of keys

           -> String        -- ^ Lookup string

           -> LookupResult  -- ^ Result of the lookup

lookupName l s = foldr (chooseLookupResult s)

                       (LookupResult FailMatch s) l