mirror of https://github.com/waku-org/nwaku.git
96 lines
2.5 KiB
Nim
96 lines
2.5 KiB
Nim
## Contains types and utilities for pagination.
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{.push raises: [Defect].}
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import
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stew/byteutils,
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nimcrypto
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import
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../protocol/waku_message,
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./time
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type Index* = object
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## This type contains the description of an Index used in the pagination of WakuMessages
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digest*: MDigest[256] # calculated over payload and content topic
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receiverTime*: Timestamp
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senderTime*: Timestamp # the time at which the message is generated
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pubsubTopic*: string
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proc compute*(T: type Index, msg: WakuMessage, receivedTime: Timestamp, pubsubTopic: string): T =
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## Takes a WakuMessage with received timestamp and returns its Index.
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## Received timestamp will default to system time if not provided.
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let
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contentTopic = toBytes(msg.contentTopic)
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payload = msg.payload
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senderTime = msg.timestamp
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var ctx: sha256
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ctx.init()
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ctx.update(contentTopic)
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ctx.update(payload)
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let digest = ctx.finish() # computes the hash
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ctx.clear()
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Index(
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digest:digest,
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receiverTime: receivedTime,
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senderTime: senderTime,
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pubsubTopic: pubsubTopic
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)
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proc `==`*(x, y: Index): bool =
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## receiverTime plays no role in index equality
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(x.senderTime == y.senderTime) and
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(x.digest == y.digest) and
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(x.pubsubTopic == y.pubsubTopic)
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proc cmp*(x, y: Index): int =
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## compares x and y
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## returns 0 if they are equal
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## returns -1 if x < y
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## returns 1 if x > y
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##
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## Default sorting order priority is:
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## 1. senderTimestamp
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## 2. receiverTimestamp (a fallback only if senderTimestamp unset on either side, and all other fields unequal)
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## 3. message digest
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## 4. pubsubTopic
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if x == y:
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# Quick exit ensures receiver time does not affect index equality
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return 0
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# Timestamp has a higher priority for comparison
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let
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# Use receiverTime where senderTime is unset
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xTimestamp = if x.senderTime == 0: x.receiverTime
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else: x.senderTime
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yTimestamp = if y.senderTime == 0: y.receiverTime
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else: y.senderTime
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let timecmp = cmp(xTimestamp, yTimestamp)
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if timecmp != 0:
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return timecmp
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# Continue only when timestamps are equal
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let digestcmp = cmp(x.digest.data, y.digest.data)
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if digestcmp != 0:
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return digestcmp
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return cmp(x.pubsubTopic, y.pubsubTopic)
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type
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PagingDirection* {.pure.} = enum
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## PagingDirection determines the direction of pagination
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BACKWARD = uint32(0)
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FORWARD = uint32(1)
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PagingInfo* = object
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## This type holds the information needed for the pagination
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pageSize*: uint64
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cursor*: Index
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direction*: PagingDirection
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