multisig_state.go

package multisig

import (
	address "github.com/filecoin-project/go-address"
	"github.com/filecoin-project/go-state-types/abi"
	"github.com/filecoin-project/go-state-types/big"
	cid "github.com/ipfs/go-cid"
	"golang.org/x/xerrors"

	"github.com/filecoin-project/specs-actors/v4/actors/builtin"
	"github.com/filecoin-project/specs-actors/v4/actors/util/adt"
)

type State struct {
	Signers               []address.Address // Signers must be canonical ID-addresses.
	NumApprovalsThreshold uint64
	NextTxnID             TxnID

	// Linear unlock
	InitialBalance abi.TokenAmount
	StartEpoch     abi.ChainEpoch
	UnlockDuration abi.ChainEpoch

	PendingTxns cid.Cid // HAMT[TxnID]Transaction
}

// Tests whether an address is in the list of signers.
func (st *State) IsSigner(address address.Address) bool {
	for _, signer := range st.Signers {
		if signer == address {
			return true
		}
	}
	return false
}

func (st *State) SetLocked(startEpoch abi.ChainEpoch, unlockDuration abi.ChainEpoch, lockedAmount abi.TokenAmount) {
	st.StartEpoch = startEpoch
	st.UnlockDuration = unlockDuration
	st.InitialBalance = lockedAmount
}

func (st *State) AmountLocked(elapsedEpoch abi.ChainEpoch) abi.TokenAmount {
	if elapsedEpoch >= st.UnlockDuration {
		return abi.NewTokenAmount(0)
	}
	if elapsedEpoch <= 0 {
		return st.InitialBalance
	}

	unlockDuration := big.NewInt(int64(st.UnlockDuration))
	remainingLockDuration := big.Sub(unlockDuration, big.NewInt(int64(elapsedEpoch)))

	// locked = ceil(InitialBalance * remainingLockDuration / UnlockDuration)
	numerator := big.Mul(st.InitialBalance, remainingLockDuration)
	denominator := unlockDuration
	quot := big.Div(numerator, denominator)
	rem := big.Mod(numerator, denominator)

	locked := quot
	if !rem.IsZero() {
		locked = big.Add(locked, big.NewInt(1))
	}
	return locked
}

// Iterates all pending transactions and removes an address from each list of approvals, if present.
// If an approval list becomes empty, the pending transaction is deleted.
func (st *State) PurgeApprovals(store adt.Store, addr address.Address) error {
	txns, err := adt.AsMap(store, st.PendingTxns, builtin.DefaultHamtBitwidth)
	if err != nil {
		return xerrors.Errorf("failed to load transactions: %w", err)
	}

	// Identify the transactions that need updating.
	var txnIdsToPurge []string              // For stable iteration
	txnsToPurge := map[string]Transaction{} // Values are not pointers, we need copies
	var txn Transaction
	if err = txns.ForEach(&txn, func(txid string) error {
		for _, approver := range txn.Approved {
			if approver == addr {
				txnIdsToPurge = append(txnIdsToPurge, txid)
				txnsToPurge[txid] = txn
				break
			}
		}
		return nil
	}); err != nil {
		return xerrors.Errorf("failed to traverse transactions: %w", err)
	}

	// Update or remove those transactions.
	for _, txid := range txnIdsToPurge {
		txn := txnsToPurge[txid]
		// The right length is almost certainly len-1, but let's not be too clever.
		newApprovers := make([]address.Address, 0, len(txn.Approved))
		for _, approver := range txn.Approved {
			if approver != addr {
				newApprovers = append(newApprovers, approver)
			}
		}

		if len(newApprovers) > 0 {
			txn.Approved = newApprovers
			if err := txns.Put(StringKey(txid), &txn); err != nil {
				return xerrors.Errorf("failed to update transaction approvers: %w", err)
			}
		} else {
			if err := txns.Delete(StringKey(txid)); err != nil {
				return xerrors.Errorf("failed to delete transaction with no approvers: %w", err)
			}
		}
	}

	if newTxns, err := txns.Root(); err != nil {
		return xerrors.Errorf("failed to persist transactions: %w", err)
	} else {
		st.PendingTxns = newTxns
	}
	return nil
}

// return nil if MultiSig maintains required locked balance after spending the amount, else return an error.
func (st *State) assertAvailable(currBalance abi.TokenAmount, amountToSpend abi.TokenAmount, currEpoch abi.ChainEpoch) error {
	if amountToSpend.LessThan(big.Zero()) {
		return xerrors.Errorf("amount to spend %s less than zero", amountToSpend.String())
	}
	if currBalance.LessThan(amountToSpend) {
		return xerrors.Errorf("current balance %s less than amount to spend %s", currBalance.String(), amountToSpend.String())
	}
	if amountToSpend.IsZero() {
		// Always permit a transaction that sends no value, even if the lockup exceeds the current balance.
		return nil
	}

	remainingBalance := big.Sub(currBalance, amountToSpend)
	amountLocked := st.AmountLocked(currEpoch - st.StartEpoch)
	if remainingBalance.LessThan(amountLocked) {
		return xerrors.Errorf("balance %s if spent %s would be less than locked amount %s",
			remainingBalance.String(), amountToSpend, amountLocked.String())
	}

	return nil
}

// An adt.Map key that just preserves the underlying string.
type StringKey string

func (k StringKey) Key() string {
	return string(k)
}