[clock] Add Clock interface that abstracts away ethereum details

dagger/clock.nim

@@ -0,0 +1,6 @@
+type
+  Clock* = ref object of RootObj
+  SecondsSince1970* = int64
+
+method now*(clock: Clock): SecondsSince1970 {.base.} =
+  raiseAssert "not implemented"

dagger/contracts/clock.nim

@@ -2,19 +2,19 @@ import std/times
 import pkg/ethers
 import pkg/chronos
 import pkg/stint
+import ../clock
 
 type
-  Clock* = ref object
+  OnChainClock* = ref object of Clock
     provider: Provider
     subscription: Subscription
     offset: int64
     started: bool
-  SecondsSince1970* = int64
 
-proc new*(_: type Clock, provider: Provider): Clock =
-  Clock(provider: provider)
+proc new*(_: type OnChainClock, provider: Provider): OnChainClock =
+  OnChainClock(provider: provider)
 
-proc start*(clock: Clock) {.async.} =
+proc start*(clock: OnChainClock) {.async.} =
   if clock.started:
     return
   clock.started = true
@@ -28,13 +28,13 @@ proc start*(clock: Clock) {.async.} =
 
   clock.subscription = await clock.provider.subscribe(onBlock)
 
-proc stop*(clock: Clock) {.async.} =
+proc stop*(clock: OnChainClock) {.async.} =
   if not clock.started:
     return
   clock.started = false
 
   await clock.subscription.unsubscribe()
 
-proc now*(clock: Clock): SecondsSince1970 =
+method now*(clock: OnChainClock): SecondsSince1970 =
   doAssert clock.started, "clock should be started before calling now()"
   getTime().toUnix + clock.offset

tests/contracts/testClock.nim

@@ -3,12 +3,12 @@ import pkg/chronos
 import dagger/contracts/clock
 import ../ethertest
 
-ethersuite "Clock":
+ethersuite "On-Chain Clock":
 
-  var clock: Clock
+  var clock: OnChainClock
 
   setup:
-    clock = Clock.new(provider)
+    clock = OnChainClock.new(provider)
     await clock.start()
 
   teardown:
@@ -32,7 +32,7 @@ ethersuite "Clock":
 
   test "raises when not started":
     expect AssertionError:
-      discard Clock.new(provider).now()
+      discard OnChainClock.new(provider).now()
 
   test "raises when stopped":
     await clock.stop()