github.com/onflow/flow-go@v0.33.17/fvm/transactionPayerBalanceChecker.go (about)

     1  package fvm
     2  
     3  import (
     4  	"fmt"
     5  
     6  	"github.com/onflow/cadence"
     7  
     8  	"github.com/onflow/flow-go/fvm/environment"
     9  	"github.com/onflow/flow-go/fvm/errors"
    10  	"github.com/onflow/flow-go/fvm/storage"
    11  )
    12  
    13  type TransactionPayerBalanceChecker struct{}
    14  
    15  func (_ TransactionPayerBalanceChecker) CheckPayerBalanceAndReturnMaxFees(
    16  	proc *TransactionProcedure,
    17  	txnState storage.TransactionPreparer,
    18  	env environment.Environment,
    19  ) (uint64, error) {
    20  	if !env.TransactionFeesEnabled() {
    21  		// if the transaction fees are not enabled,
    22  		// the payer can pay for the transaction,
    23  		// and the max transaction fees are 0.
    24  		// This is also the condition that gets hit during bootstrapping.
    25  		return 0, nil
    26  	}
    27  
    28  	var resultValue cadence.Value
    29  	var err error
    30  	txnState.RunWithAllLimitsDisabled(func() {
    31  		// Don't meter the payer balance check.
    32  		// It has a static cost, and its cost should be part of the inclusion fees, not part of execution fees.
    33  		resultValue, err = env.CheckPayerBalanceAndGetMaxTxFees(
    34  			proc.Transaction.Payer,
    35  			proc.Transaction.InclusionEffort(),
    36  			uint64(txnState.TotalComputationLimit()),
    37  		)
    38  	})
    39  	if err != nil {
    40  		return 0, errors.NewPayerBalanceCheckFailure(proc.Transaction.Payer, err)
    41  	}
    42  
    43  	// parse expected result from the Cadence runtime
    44  	// https://github.com/onflow/flow-core-contracts/blob/7c70c6a1d33c2879b60c78e363fa68fc6fce13b9/contracts/FlowFees.cdc#L75
    45  	result, ok := resultValue.(cadence.Struct)
    46  	if ok && len(result.Fields) == 3 {
    47  		payerCanPay, okBool := result.Fields[0].(cadence.Bool)
    48  		requiredBalance, okBalance := result.Fields[1].(cadence.UFix64)
    49  		maxFees, okFees := result.Fields[2].(cadence.UFix64)
    50  
    51  		if okBool && okBalance && okFees {
    52  			if !payerCanPay {
    53  				return 0, errors.NewInsufficientPayerBalanceError(proc.Transaction.Payer, requiredBalance)
    54  			}
    55  			return uint64(maxFees), nil
    56  		}
    57  	}
    58  
    59  	return 0, errors.NewPayerBalanceCheckFailure(proc.Transaction.Payer, fmt.Errorf("invalid result type"))
    60  }