nim-codex/dagger/purchasing.nim

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import std/times
import pkg/stint
import pkg/chronos
import pkg/questionable
import pkg/nimcrypto
import ./market
export questionable
export market
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type
Purchasing* = ref object
market: Market
proofProbability*: UInt256
requestExpiryInterval*: UInt256
offerExpiryMargin*: UInt256
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Purchase* = ref object
future: Future[void]
market: Market
offerExpiryMargin: UInt256
request*: StorageRequest
offers*: seq[StorageOffer]
selected*: ?StorageOffer
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const DefaultProofProbability = 100.u256
const DefaultRequestExpiryInterval = (10 * 60).u256
const DefaultOfferExpiryMargin = (8 * 60).u256
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proc start(purchase: Purchase) {.gcsafe.}
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proc new*(_: type Purchasing, market: Market): Purchasing =
Purchasing(
market: market,
proofProbability: DefaultProofProbability,
requestExpiryInterval: DefaultRequestExpiryInterval,
offerExpiryMargin: DefaultOfferExpiryMargin
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)
proc populate*(purchasing: Purchasing, request: StorageRequest): StorageRequest =
result = request
if result.proofProbability == 0.u256:
result.proofProbability = purchasing.proofProbability
if result.expiry == 0.u256:
result.expiry = (getTime().toUnix().u256 + purchasing.requestExpiryInterval)
if result.nonce == array[32, byte].default:
doAssert randomBytes(result.nonce) == 32
proc purchase*(purchasing: Purchasing, request: StorageRequest): Purchase =
let request = purchasing.populate(request)
let purchase = Purchase(
request: request,
market: purchasing.market,
offerExpiryMargin: purchasing.offerExpiryMargin
)
purchase.start()
purchase
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proc selectOffer(purchase: Purchase) {.async.} =
var cheapest: ?StorageOffer
for offer in purchase.offers:
without getTime().toUnix().u256 < offer.expiry - purchase.offerExpiryMargin:
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continue
without current =? cheapest:
cheapest = some offer
continue
if current.price > offer.price:
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cheapest = some offer
if cheapest =? cheapest:
await purchase.market.selectOffer(cheapest.id)
proc run(purchase: Purchase) {.async.} =
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proc onOffer(offer: StorageOffer) =
purchase.offers.add(offer)
let market = purchase.market
purchase.request = await market.requestStorage(purchase.request)
let subscription = await market.subscribeOffers(purchase.request.id, onOffer)
await market.waitUntil(purchase.request.expiry)
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await purchase.selectOffer()
await subscription.unsubscribe()
proc start(purchase: Purchase) =
purchase.future = purchase.run()
asyncSpawn purchase.future
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proc wait*(purchase: Purchase) {.async.} =
await purchase.future