nim-ethers/ethers/contract.nim

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Nim
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import std/macros
import pkg/chronos
import pkg/contractabi
import ./basics
import ./provider
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import ./signer
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import ./events
import ./fields
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export basics
export provider
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export events
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type
Contract* = ref object of RootObj
provider: Provider
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signer: ?Signer
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address: Address
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ContractError* = object of EthersError
EventHandler*[E: Event] = proc(event: E) {.gcsafe, upraises:[].}
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func new*(ContractType: type Contract,
address: Address,
provider: Provider): ContractType =
ContractType(provider: provider, address: address)
func new*(ContractType: type Contract,
address: Address,
signer: Signer): ContractType =
ContractType(signer: some signer, provider: signer.provider, address: address)
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func connect*[T: Contract](contract: T, provider: Provider | Signer): T =
T.new(contract.address, provider)
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func provider*(contract: Contract): Provider =
contract.provider
func signer*(contract: Contract): ?Signer =
contract.signer
func address*(contract: Contract): Address =
contract.address
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template raiseContractError(message: string) =
raise newException(ContractError, message)
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proc createTransaction(contract: Contract,
function: string,
parameters: tuple): Transaction =
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let selector = selector(function, typeof parameters).toArray
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let data = @selector & AbiEncoder.encode(parameters)
Transaction(to: contract.address, data: data)
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proc decodeResponse(T: type, bytes: seq[byte]): T =
without decoded =? AbiDecoder.decode(bytes, T):
raiseContractError "unable to decode return value as " & $T
return decoded
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proc call(contract: Contract, function: string, parameters: tuple) {.async.} =
let transaction = createTransaction(contract, function, parameters)
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discard await contract.provider.call(transaction)
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proc call(contract: Contract,
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function: string,
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parameters: tuple,
ReturnType: type): Future[ReturnType] {.async.} =
let transaction = createTransaction(contract, function, parameters)
let response = await contract.provider.call(transaction)
return decodeResponse(ReturnType, response)
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proc send(contract: Contract, function: string, parameters: tuple) {.async.} =
if signer =? contract.signer:
let transaction = createTransaction(contract, function, parameters)
let populated = await signer.populateTransaction(transaction)
await signer.sendTransaction(populated)
else:
await call(contract, function, parameters)
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func getParameterTuple(procedure: NimNode): NimNode =
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let parameters = procedure[3]
var tupl = newNimNode(nnkTupleConstr, parameters)
for parameter in parameters[2..^1]:
for name in parameter[0..^3]:
tupl.add name
return tupl
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func isConstant(procedure: NimNode): bool =
let pragmas = procedure[4]
for pragma in pragmas:
if pragma.eqIdent "view":
return true
elif pragma.eqIdent "pure":
return true
false
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func addContractCall(procedure: var NimNode) =
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let contract = procedure[3][1][0]
let function = $basename(procedure[0])
let parameters = getParameterTuple(procedure)
let returntype = procedure[3][0]
procedure[6] =
if procedure.isConstant:
if returntype.kind == nnkEmpty:
quote:
await call(`contract`, `function`, `parameters`)
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else:
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quote:
return await call(`contract`, `function`, `parameters`, `returntype`)
else:
quote:
await send(`contract`, `function`, `parameters`)
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func addFuture(procedure: var NimNode) =
let returntype = procedure[3][0]
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if returntype.kind != nnkEmpty:
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procedure[3][0] = quote: Future[`returntype`]
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func addAsyncPragma(procedure: var NimNode) =
let pragmas = procedure[4]
if pragmas.kind == nnkEmpty:
procedure[4] = newNimNode(nnkPragma)
procedure[4].add ident("async")
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func checkReturnType(procedure: NimNode) =
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let returntype = procedure[3][0]
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if returntype.kind != nnkEmpty and not procedure.isConstant:
const message =
"only contract functions with {.view.} or {.pure.} " &
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"can have a return type"
error(message, returntype)
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macro contract*(procedure: untyped{nkProcDef|nkMethodDef}): untyped =
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let parameters = procedure[3]
let body = procedure[6]
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parameters.expectMinLen(2) # at least return type and contract instance
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body.expectKind(nnkEmpty)
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procedure.checkReturnType()
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var contractcall = copyNimTree(procedure)
contractcall.addContractCall()
contractcall.addFuture()
contractcall.addAsyncPragma()
contractcall
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template view* {.pragma.}
template pure* {.pragma.}
proc subscribe*[E: Event](contract: Contract,
_: type E,
handler: EventHandler[E]):
Future[Subscription] =
let topic = topic($E, E.fieldTypes).toArray
let filter = Filter(address: contract.address, topics: @[topic])
proc logHandler(log: Log) {.upraises: [].} =
if event =? E.decode(log.data, log.topics):
handler(event)
contract.provider.subscribe(filter, logHandler)