(.module:
  [library
   [lux "*"
    [abstract
     [equivalence {"+" [Equivalence]}]]
    [data
     [binary {"+" [Binary]}]
     ["." sum]
     ["." product]]]]
  ["." /// "_"
   ["#." hash {"+" [Hash SHA-1 MD5]}]])

(type: .public Status
  (Variant
   #Unverified
   (#Partial (Either (Hash SHA-1)
                     (Hash MD5)))
   (#Verified (Hash SHA-1) (Hash MD5))))

(implementation: any_equivalence
  (Equivalence Any)

  (def: (= _ _)
    true))

(def: .public equivalence
  (Equivalence Status)
  ($_ sum.equivalence
      ..any_equivalence
      ($_ sum.equivalence
          ///hash.equivalence
          ///hash.equivalence)
      ($_ product.equivalence
          ///hash.equivalence
          ///hash.equivalence)
      ))

(def: .public (verified payload)
  (-> Binary Status)
  (#Verified
   (///hash.sha-1 payload)
   (///hash.md5 payload)))