Accounting SWAP protocol basic data types and test (#262)

* Start of SWAP

* SWAP basic data types (untested)

* SWAP Add handshake test and fix imports

* SWAP Add cheque encode/decode test and fix bug

tests/all_tests_v2.nim

@@ -7,4 +7,5 @@ import
   ./v2/test_waku_filter,
   ./v2/test_waku_pagination,
   ./v2/test_waku_payload,
-  ./v2/test_rpc_waku
+  ./v2/test_rpc_waku,
+  ./v2/test_waku_swap

tests/v2/test_waku_swap.nim

@@ -0,0 +1,33 @@
+import
+  std/[unittest, options, tables, sets],
+  chronos, chronicles,
+  ../../waku/protocol/v2/waku_swap,
+  ../../waku/node/v2/waku_types,
+  ../test_helpers, ./utils
+
+procSuite "Waku SWAP Accounting":
+  test "Handshake Encode/Decode":
+    let
+      beneficiary = @[byte 0, 1, 2]
+      handshake = Handshake(beneficiary: beneficiary)
+      pb = handshake.encode()
+
+    let decodedHandshake = Handshake.init(pb.buffer)
+
+    check:
+      decodedHandshake.isErr == false
+      decodedHandshake.get().beneficiary == beneficiary
+
+  test "Cheque Encode/Decode":
+    let
+      amount = 1'u32
+      date = 9000'u32
+      beneficiary = @[byte 0, 1, 2]
+      cheque = Cheque(beneficiary: beneficiary, amount: amount, date: date)
+      pb = cheque.encode()
+
+    let decodedCheque = Cheque.init(pb.buffer)
+
+    check:
+      decodedCheque.isErr == false
+      decodedCheque.get() == cheque

waku/node/v2/waku_types.nim

@@ -12,8 +12,10 @@ import
   libp2p/stream/connection,
   libp2p/protocols/pubsub/[pubsub, gossipsub],
   nimcrypto/sha2
-# constants required for pagination -------------------------------------------
-const MaxPageSize* = 100 # Maximum number of waku messages in each page 
+
+# Constants required for pagination -------------------------------------------
+const MaxPageSize* = 100 # Maximum number of waku messages in each page
+
 # Common data types -----------------------------------------------------------
 type
   ContentTopic* = uint32
@@ -147,8 +149,21 @@ type
     #multiaddrStrings*: seq[string]
 
   WakuResult*[T] = Result[T, cstring]
-# Encoding and decoding -------------------------------------------------------
 
+  Beneficiary* = seq[byte]
+
+  # TODO Consider adding payment threshhold and terms field
+  Handshake* = object
+    beneficiary*: Beneficiary
+
+  Cheque* = object
+    beneficiary*: Beneficiary
+    date*: uint32
+    amount*: uint32
+
+# Encoding and decoding -------------------------------------------------------
+# TODO Move out to to waku_message module
+# Possibly same with util functions
 proc init*(T: type WakuMessage, buffer: seq[byte]): ProtoResult[T] =
   var msg = WakuMessage()
   let pb = initProtoBuffer(buffer)
@@ -199,4 +214,4 @@ proc computeIndex*(msg: WakuMessage): Index =
   ctx.clear()
 
   result.digest = digest
-  result.receivedTime = epochTime() # gets the unix timestamp
+  result.receivedTime = epochTime() # gets the unix timestamp

waku/protocol/v2/waku_swap.nim

@@ -0,0 +1,73 @@
+## SWAP implements Accounting for Waku. See
+## https://github.com/vacp2p/specs/issues/24 for more.
+##
+## This is based on the SWAP based approach researched by the Swarm team, and
+## can be thought of as an economic extension to Bittorrent's tit-for-tat
+## economics.
+##
+## It is quite suitable for accounting for imbalances between peers, and
+## specifically for something like the Store protocol.
+##
+## It is structured as follows:
+##
+## 1) First a handshake is made, where terms are agreed upon
+##
+## 2) Then operation occurs as normal with HistoryRequest, HistoryResponse etc
+## through store protocol (or otherwise)
+##
+## 3) When payment threshhold is met, a cheque is sent. This acts as promise to
+## pay. Right now it is best thought of as karma points.
+##
+## Things like settlement is for future work.
+##
+
+import
+  std/[tables, sequtils, future, algorithm, options],
+  bearssl,
+  chronos, chronicles, metrics, stew/[results,byteutils],
+  libp2p/switch,
+  libp2p/crypto/crypto,
+  libp2p/protocols/protocol,
+  libp2p/protobuf/minprotobuf,
+  libp2p/stream/connection,
+  ./message_notifier,
+  ./../../node/v2/waku_types
+
+export waku_types
+
+logScope:
+  topics = "wakuswap"
+
+const WakuSwapCodec* = "/vac/waku/swap/2.0.0-alpha1"
+
+proc encode*(handshake: Handshake): ProtoBuffer =
+  result = initProtoBuffer()
+  result.write(1, handshake.beneficiary)
+
+proc encode*(cheque: Cheque): ProtoBuffer =
+  result = initProtoBuffer()
+  result.write(1, cheque.beneficiary)
+  result.write(2, cheque.date)
+  result.write(3, cheque.amount)
+
+proc init*(T: type Handshake, buffer: seq[byte]): ProtoResult[T] =
+  var beneficiary: seq[byte]
+  var handshake = Handshake()
+  let pb = initProtoBuffer(buffer)
+
+  discard ? pb.getField(1, handshake.beneficiary)
+
+  ok(handshake)
+
+proc init*(T: type Cheque, buffer: seq[byte]): ProtoResult[T] =
+  var beneficiary: seq[byte]
+  var date: uint32
+  var amount: uint32
+  var cheque = Cheque()
+  let pb = initProtoBuffer(buffer)
+
+  discard ? pb.getField(1, cheque.beneficiary)
+  discard ? pb.getField(2, cheque.date)
+  discard ? pb.getField(3, cheque.amount)
+
+  ok(cheque)