(.module:
  [library
   [lux "*"
    [abstract
     [equivalence {"+" [Equivalence]}]]
    [data
     [binary {"+" [Binary]}]
     ["[0]" sum]
     ["[0]" product]]]]
  ["[0]" /// "_"
   ["[1][0]" 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)})