Pagination: Pagination feature/compute index (#225)

* adds the index object

* adds the indexedWakuMessage

* adds the PagingInfo

* Adds PagingInfo to HistoryResponse and HistoryQuery

* adds the computeIndex procedure

* Update waku/node/v2/waku_types.nim

Fixes spacing issues

Co-authored-by: Oskar Thorén <ot@oskarthoren.com>

* Changes timestamp to receivedTime and checks for the  empty contentTopic

* adds a test file for pagination with test scenarios for computeIndex

* changes receivedTimestamp to the unix timestamp

* updates a test case

* replaces std/sha1 with  nimcrypto/sha2

* changes the tests titles

* minor comments

* Some clean up

* fixes some formatting issue

* edits a test-case

* adds comments

* changes the digest type to MDigest[256] and modifies the computeIndex

* fixes formatting issue

* edits indentations and fixes a bug

* minor edits

* changes suite to procSuite and adds a new text case

* fixes all the indentations

* cleanup of the imports

Co-authored-by: Oskar Thorén <ot@oskarthoren.com>

tests/v2/test_waku_pagination.nim

@@ -0,0 +1,27 @@
+import
+  std/unittest,
+  ../../waku/node/v2/waku_types,
+  ../test_helpers
+
+procSuite "pagination":
+  test "computeIndex: empty contentTopic test":
+    let
+      wm = WakuMessage(payload: @[byte 1, 2, 3])
+      index = wm.computeIndex()
+    check:
+      # the fields of the index should be non-empty
+      len(index.digest.data) != 0
+      len(index.digest.data) == 32 # sha2 output length in bytes
+      index.receivedTime != 0 # the timestamp should be a non-zero value
+
+  test "computeIndex: identical WakuMessages test":
+    let
+      wm = WakuMessage(payload: @[byte 1, 2, 3], contentTopic: "topic2")
+      index1 = wm.computeIndex()
+      wm2 = WakuMessage(payload: @[byte 1, 2, 3], contentTopic: "topic2")
+      index2 = wm2.computeIndex()
+
+    check:
+      # the digests of two identical WakuMessages must be the same
+      index1.digest == index2.digest
+

waku/node/v2/waku_types.nim

@@ -3,14 +3,16 @@
 ## TODO Move more common data types here
 
 import
-  std/tables,
+  std/[tables, times],
   chronos, bearssl, stew/byteutils,
   libp2p/[switch, peerinfo, multiaddress, crypto/crypto],
   libp2p/protobuf/minprotobuf,
   libp2p/protocols/protocol,
   libp2p/switch,
   libp2p/stream/connection,
-  libp2p/protocols/pubsub/[pubsub, gossipsub]
+  libp2p/protocols/pubsub/[pubsub, gossipsub],
+  nimcrypto/sha2,
+  stew/byteutils
 
 # Common data types -----------------------------------------------------------
 
@@ -32,11 +34,29 @@ type
 
   QueryHandlerFunc* = proc(response: HistoryResponse) {.gcsafe, closure.}
 
+
+  Index* = object
+    ## This type contains the  description of an index used in the pagination of waku messages
+    digest*: MDigest[256]
+    receivedTime*: float
+
+  IndexedWakuMessage* = object
+    msg*: WakuMessage
+    index*: Index
+
+  PagingInfo* = object
+    ## This type holds the information needed for the pagination
+    pageSize*: int
+    cursor*: Index
+    direction*: bool
+
   HistoryQuery* = object
     topics*: seq[string]
+    pagingInfo*: PagingInfo
 
   HistoryResponse* = object
     messages*: seq[WakuMessage]
+    pagingInfo*: PagingInfo
 
   HistoryRPC* = object
     requestId*: string
@@ -115,7 +135,7 @@ type
     listenStr*: string
     #multiaddrStrings*: seq[string]
 
-# Encoding and decoding -------------------------------------------------------
+  # Encoding and decoding -------------------------------------------------------
 
 proc init*(T: type WakuMessage, buffer: seq[byte]): ProtoResult[T] =
   var msg = WakuMessage()
@@ -154,3 +174,17 @@ proc generateRequestId*(rng: ref BrHmacDrbgContext): string =
   var bytes: array[10, byte]
   brHmacDrbgGenerate(rng[], bytes)
   toHex(bytes)
+
+proc computeIndex*(msg: WakuMessage): Index =
+  ## Takes a WakuMessage and returns its index
+  var ctx: sha256
+  ctx.init()
+  if msg.contentTopic.len != 0: # checks for non-empty contentTopic
+    ctx.update(msg.contentTopic.toBytes()) # converts the topic to bytes
+  ctx.update(msg.payload)
+  let digest = ctx.finish()  # computes the hash
+  ctx.clear()
+
+  result.digest = digest
+  result.receivedTime = epochTime() # gets the unix timestamp
+