// managedVerifyRenewedContract checks that the contract renewal matches the
// previous contract and makes all of the appropriate payments.
func (h *Host) managedVerifyRenewedContract(so storageObligation, txnSet []types.Transaction, renterPK crypto.PublicKey) error {
	// Check that the transaction set is not empty.
	if len(txnSet) < 1 {
		return extendErr("zero-length transaction set: ", errEmptyObject)
	}
	// Check that the transaction set has a file contract.
	if len(txnSet[len(txnSet)-1].FileContracts) < 1 {
		return extendErr("transaction without file contract: ", errEmptyObject)
	}

	h.mu.RLock()
	blockHeight := h.blockHeight
	externalSettings := h.externalSettings()
	internalSettings := h.settings
	lockedStorageCollateral := h.financialMetrics.LockedStorageCollateral
	publicKey := h.publicKey
	unlockHash := h.unlockHash
	h.mu.RUnlock()
	fc := txnSet[len(txnSet)-1].FileContracts[0]

	// The file size and merkle root must match the file size and merkle root
	// from the previous file contract.
	if fc.FileSize != so.fileSize() {
		return errBadFileSize
	}
	if fc.FileMerkleRoot != so.merkleRoot() {
		return errBadFileMerkleRoot
	}
	// The WindowStart must be at least revisionSubmissionBuffer blocks into
	// the future.
	if fc.WindowStart <= blockHeight+revisionSubmissionBuffer {
		return errEarlyWindow
	}
	// WindowEnd must be at least settings.WindowSize blocks after WindowStart.
	if fc.WindowEnd < fc.WindowStart+externalSettings.WindowSize {
		return errSmallWindow
	}

	// ValidProofOutputs shoud have 2 outputs (renter + host) and missed
	// outputs should have 3 (renter + host + void)
	if len(fc.ValidProofOutputs) != 2 || len(fc.MissedProofOutputs) != 3 {
		return errBadContractOutputCounts
	}
	// The unlock hashes of the valid and missed proof outputs for the host
	// must match the host's unlock hash. The third missed output should point
	// to the void.
	if fc.ValidProofOutputs[1].UnlockHash != unlockHash || fc.MissedProofOutputs[1].UnlockHash != unlockHash || fc.MissedProofOutputs[2].UnlockHash != (types.UnlockHash{}) {
		return errBadPayoutUnlockHashes
	}

	// Check that the collateral does not exceed the maximum amount of
	// collateral allowed.
	expectedCollateral := renewContractCollateral(so, externalSettings, fc)
	if expectedCollateral.Cmp(externalSettings.MaxCollateral) > 0 {
		return errMaxCollateralReached
	}
	// Check that the host has enough room in the collateral budget to add this
	// collateral.
	if lockedStorageCollateral.Add(expectedCollateral).Cmp(internalSettings.CollateralBudget) > 0 {
		return errCollateralBudgetExceeded
	}
	// Check that the missed proof outputs contain enough money, and that the
	// void output contains enough money.
	basePrice := renewBasePrice(so, externalSettings, fc)
	baseCollateral := renewBaseCollateral(so, externalSettings, fc)
	if fc.ValidProofOutputs[1].Value.Cmp(basePrice.Add(baseCollateral)) < 0 {
		return errLowHostValidOutput
	}
	expectedHostMissedOutput := fc.ValidProofOutputs[1].Value.Sub(basePrice).Sub(baseCollateral)
	if fc.MissedProofOutputs[1].Value.Cmp(expectedHostMissedOutput) < 0 {
		return errLowHostMissedOutput
	}
	// Check that the void output has the correct value.
	expectedVoidOutput := basePrice.Add(baseCollateral)
	if fc.MissedProofOutputs[2].Value.Cmp(expectedVoidOutput) > 0 {
		return errLowVoidOutput
	}

	// The unlock hash for the file contract must match the unlock hash that
	// the host knows how to spend.
	expectedUH := types.UnlockConditions{
		PublicKeys: []types.SiaPublicKey{
			{
				Algorithm: types.SignatureEd25519,
				Key:       renterPK[:],
			},
			publicKey,
		},
		SignaturesRequired: 2,
	}.UnlockHash()
	if fc.UnlockHash != expectedUH {
		return errBadUnlockHash
	}

	// Check that the transaction set has enough fees on it to get into the
	// blockchain.
	setFee := modules.CalculateFee(txnSet)
	minFee, _ := h.tpool.FeeEstimation()
	if setFee.Cmp(minFee) < 0 {
		return errLowTransactionFees
	}
	return nil
}
// managedVerifyNewContract checks that an incoming file contract matches the host's
// expectations for a valid contract.
func (h *Host) managedVerifyNewContract(txnSet []types.Transaction, renterPK crypto.PublicKey) error {
	// Check that the transaction set is not empty.
	if len(txnSet) < 1 {
		return extendErr("zero-length transaction set: ", errEmptyObject)
	}
	// Check that there is a file contract in the txnSet.
	if len(txnSet[len(txnSet)-1].FileContracts) < 1 {
		return extendErr("transaction without file contract: ", errEmptyObject)
	}

	h.mu.RLock()
	blockHeight := h.blockHeight
	lockedStorageCollateral := h.financialMetrics.LockedStorageCollateral
	publicKey := h.publicKey
	settings := h.settings
	unlockHash := h.unlockHash
	h.mu.RUnlock()
	fc := txnSet[len(txnSet)-1].FileContracts[0]

	// A new file contract should have a file size of zero.
	if fc.FileSize != 0 {
		return errBadFileSize
	}
	if fc.FileMerkleRoot != (crypto.Hash{}) {
		return errBadFileMerkleRoot
	}
	// WindowStart must be at least revisionSubmissionBuffer blocks into the
	// future.
	if fc.WindowStart <= blockHeight+revisionSubmissionBuffer {
		h.log.Debugf("A renter tried to form a contract that had a window start which was too soon. The contract started at %v, the current height is %v, the revisionSubmissionBuffer is %v, and the comparison was %v <= %v\n", fc.WindowStart, blockHeight, revisionSubmissionBuffer, fc.WindowStart, blockHeight+revisionSubmissionBuffer)
		return errEarlyWindow
	}
	// WindowEnd must be at least settings.WindowSize blocks after
	// WindowStart.
	if fc.WindowEnd < fc.WindowStart+settings.WindowSize {
		return errSmallWindow
	}
	// WindowEnd must not be more than settings.MaxDuration blocks into the
	// future.
	if fc.WindowStart > blockHeight+settings.MaxDuration {
		return errLongDuration
	}

	// ValidProofOutputs shoud have 2 outputs (renter + host) and missed
	// outputs should have 3 (renter + host + void)
	if len(fc.ValidProofOutputs) != 2 || len(fc.MissedProofOutputs) != 3 {
		return errBadContractOutputCounts
	}
	// The unlock hashes of the valid and missed proof outputs for the host
	// must match the host's unlock hash. The third missed output should point
	// to the void.
	if fc.ValidProofOutputs[1].UnlockHash != unlockHash || fc.MissedProofOutputs[1].UnlockHash != unlockHash || fc.MissedProofOutputs[2].UnlockHash != (types.UnlockHash{}) {
		return errBadPayoutUnlockHashes
	}
	// Check that the payouts for the valid proof outputs and the missed proof
	// outputs are the same - this is important because no data has been added
	// to the file contract yet.
	if fc.ValidProofOutputs[1].Value.Cmp(fc.MissedProofOutputs[1].Value) != 0 {
		return errMismatchedHostPayouts
	}
	// Check that there's enough payout for the host to cover at least the
	// contract price. This will prevent negative currency panics when working
	// with the collateral.
	if fc.ValidProofOutputs[1].Value.Cmp(settings.MinContractPrice) < 0 {
		return errLowHostValidOutput
	}
	// Check that the collateral does not exceed the maximum amount of
	// collateral allowed.
	expectedCollateral := contractCollateral(settings, fc)
	if expectedCollateral.Cmp(settings.MaxCollateral) > 0 {
		return errMaxCollateralReached
	}
	// Check that the host has enough room in the collateral budget to add this
	// collateral.
	if lockedStorageCollateral.Add(expectedCollateral).Cmp(settings.CollateralBudget) > 0 {
		return errCollateralBudgetExceeded
	}

	// The unlock hash for the file contract must match the unlock hash that
	// the host knows how to spend.
	expectedUH := types.UnlockConditions{
		PublicKeys: []types.SiaPublicKey{
			{
				Algorithm: types.SignatureEd25519,
				Key:       renterPK[:],
			},
			publicKey,
		},
		SignaturesRequired: 2,
	}.UnlockHash()
	if fc.UnlockHash != expectedUH {
		return errBadUnlockHash
	}

	// Check that the transaction set has enough fees on it to get into the
	// blockchain.
	setFee := modules.CalculateFee(txnSet)
	minFee, _ := h.tpool.FeeEstimation()
	if setFee.Cmp(minFee) < 0 {
		return errLowTransactionFees
	}
	return nil
}