version 1 .
embeddedType EntityRef.Cap .

# ---------------------------------------------------------------------------
# Binding and connection

SturdyStepType = =ref .

# In a gatekeeper.Step or gatekeeper.PathStep, use Parameters as detail.
SturdyStepDetail = Parameters .
SturdyPathStepDetail = Parameters .

# In a gatekeeper.Description, use the following detail.
SturdyDescriptionDetail = {
  oid: any,
  key: bytes,
} .

# ---------------------------------------------------------------------------
# Macaroons

# The sequence of Caveats is run RIGHT-TO-LEFT.
# That is, the newest Caveats are at the right.
#
# Let f(k,d) = HMAC-BLAKE2s-256(k,d)[0..16),
#     e = canonical machine-oriented serialization of some preserves value, and
#     k = the original secret key for the ref.
#
# The `sig` is then f(f(f(f(k, e(oid)), ...), e(Caveat)), ...).
#
SturdyRef = <ref @parameters Parameters> .
Parameters = {
  oid: any,
  sig: bytes,
} & @caveats CaveatsField .
CaveatsField = @present { caveats: [Caveat ...] } / @invalid { caveats: any } / @absent {} .

# embodies 1st-party caveats over assertion structure, but nothing else
# can add 3rd-party caveats and richer predicates later
Caveat = Rewrite / Alts / Reject / @unknown any .
Rewrite = <rewrite @pattern Pattern @template Template> .
Reject = <reject @pattern Pattern> .
Alts = <or @alternatives [Rewrite ...]>.

Oid = int .
WireRef = @mine [0 @oid Oid] / @yours [1 @oid Oid @attenuation Caveat ...].

# ---------------------------------------------------------------------------

Lit = <lit @value any>.

Pattern = PDiscard / PAtom / PEmbedded / PBind / PAnd / PNot / Lit / PCompound .
PDiscard = <_>.
PAtom = =Boolean / =Float / =Double / =SignedInteger / =String / =ByteString / =Symbol .
PEmbedded = =Embedded .
PBind = <bind @pattern Pattern>.
PAnd = <and @patterns [Pattern ...]>.
PNot = <not @pattern Pattern>.
PCompound =
    / @rec <rec @label any @fields [Pattern ...]>
    / @arr <arr @items [Pattern ...]>
    / @dict <dict @entries { any: Pattern ...:... }> .

Template = TAttenuate / TRef / Lit / TCompound .
TAttenuate = <attenuate @template Template @attenuation [Caveat ...]>.
TRef = <ref @binding int>.
TCompound =
    / @rec <rec @label any @fields [Template ...]>
    / @arr <arr @items [Template ...]>
    / @dict <dict @entries { any: Template ...:... }> .