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restore_footprint.md

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Restore Footprint

The RestoreFootprint operation is used to restore a contract data entry's. The restored entry will have its expiration ledger bumped to the minimums the network allows for newly created entries, which is 4096 + current ledger for persistent entries.

A contract instance, wasm hash, and data storage entry (persistent/instance) can expire, so in case you need any of these already expired info, you can use this restore for it. Read more about it:

In this example, we will restore a contract instance of an already expired contract in the network.

Warning Please note that Soroban is still under development, so breaking changes may occur.

Note All this actions require to use simulateTransaction and sendTransaction RPC endpoints when specified in the code comments to achieve the restore footprint.

alias Stellar.TxBuild.{
  Account,
  BaseFee,
  LedgerFootprint,
  LedgerKey,
  RestoreFootprint,
  SCAddress,
  SCVal,
  SequenceNumber,
  Signature,
  SorobanResources,
  SorobanTransactionData
}

alias Stellar.Horizon.Accounts
alias Stellar.KeyPair

server = Stellar.Horizon.Server.testnet()
contract_sc_address = SCAddress.new("CAMGSYINVVL6WP3Q5WPNL7FS4GZP37TWV7MKIRQF5QMYLK3N2SW4P3RC")
key = SCVal.new(ledger_key_contract_instance: nil)

keypair = {public_key, _secret} = KeyPair.from_secret_seed("SCA...3EK")

contract_data =
  LedgerKey.new(
    {:contract_data,
     [
       contract: contract_sc_address,
       key: key,
       durability: :persistent
     ]}
  )

footprint = LedgerFootprint.new(read_write: [contract_data])

soroban_data =
[
  footprint: footprint,
  instructions: 0,
  read_bytes: 0,
  write_bytes: 0
]
|> SorobanResources.new()
|> (&SorobanTransactionData.new(resources: &1, resource_fee: 0)).()
|> SorobanTransactionData.to_xdr()

source_account = Account.new(public_key)
{:ok, seq_num} = Accounts.fetch_next_sequence_number(server, public_key)
sequence_number = SequenceNumber.new(seq_num)
signature = Signature.new(keypair)
restore_footprint_op = RestoreFootprint.new()

# Use this XDR to simulate the transaction and get the soroban_data and min_resource_fee
source_account
|> Stellar.TxBuild.new(sequence_number: sequence_number)
|> Stellar.TxBuild.add_operation(restore_footprint_op)
|> Stellar.TxBuild.set_soroban_data(soroban_data)
|> Stellar.TxBuild.envelope()

# Simulate Transaction
soroban_data =
      "AAAAAAAAAAAAAAABAAAABgAAAAHO/TJVxUVOMxLMlSFIVfYhn4K3jGxh57QYIImRFZhhywAAABQAAAABAAAAAAAAAAAAAAS0AAAEtAAACWgAAAAAAAAB1w=="

min_resource_fee = 37_351
fee = BaseFee.new(min_resource_fee + 100)

# Use the XDR generated here to send it to the futurenet
source_account
|> Stellar.TxBuild.new(sequence_number: sequence_number)
|> Stellar.TxBuild.add_operation(restore_footprint_op)
|> Stellar.TxBuild.set_soroban_data(soroban_data)
|> Stellar.TxBuild.set_base_fee(fee)
|> Stellar.TxBuild.sign(signature)
|> Stellar.TxBuild.envelope()