use upraises and avoid exceptions on key access

dagger/blockexchange/pendingblocks.nim

@@ -8,6 +8,11 @@
 ## those terms.
 
 import std/tables
+import std/sequtils
+
+import pkg/upraises
+
+push: {.upraises: [].}
 
 import pkg/questionable
 import pkg/chronicles
@@ -19,18 +24,22 @@ import ../blocktype
 logScope:
   topics = "dagger blockexc pendingblocks"
 
+const
+  DefaultBlockTimeout* = 10.minutes
+
 type
   PendingBlocksManager* = ref object of RootObj
     blocks*: Table[Cid, Future[Block]] # pending Block requests
 
-proc addOrAwait*(
+proc getWantHandle*(
   p: PendingBlocksManager,
-  cid: Cid): Future[Block] {.async.} =
+  cid: Cid,
+  timeout = DefaultBlockTimeout): Future[Block] {.async.} =
   ## Add an event for a block
   ##
 
   if cid notin p.blocks:
-     p.blocks[cid] = newFuture[Block]()
+     p.blocks[cid] = newFuture[Block]().wait(timeout)
      trace "Adding pending future for block", cid
 
   try:
@@ -52,11 +61,11 @@ proc resolve*(
   for blk in blocks:
     # resolve any pending blocks
     if blk.cid in p.blocks:
-      let pending = p.blocks[blk.cid]
-      if not pending.finished:
-        trace "Resolving block", cid = $blk.cid
-        pending.complete(blk)
-        p.blocks.del(blk.cid)
+      p.blocks.withValue(blk.cid, pending):
+        if not pending[].finished:
+          trace "Resolving block", cid = $blk.cid
+          pending[].complete(blk)
+          p.blocks.del(blk.cid)
 
 proc pending*(
   p: PendingBlocksManager,
@@ -66,6 +75,17 @@ proc contains*(
   p: PendingBlocksManager,
   cid: Cid): bool = p.pending(cid)
 
+iterator wantList*(p: PendingBlocksManager): Cid =
+  for k in p.blocks.keys:
+    yield k
+
+iterator wantHandles*(p: PendingBlocksManager): Future[Block] =
+  for v in p.blocks.values:
+    yield v
+
+func len*(p: PendingBlocksManager): int =
+  p.blocks.len
+
 func new*(T: type PendingBlocksManager): T =
   T(
     blocks: initTable[Cid, Future[Block]]()