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// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package swap
import (
"fmt"
"math/big"
"sync"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/logger"
"github.com/ethereum/go-ethereum/logger/glog"
)
// SwAP Swarm Accounting Protocol with
// Swift Automatic Payments
// a peer to peer micropayment system
// public swap profile
// public parameters for SWAP, serializable config struct passed in handshake
type Profile struct {
BuyAt *big.Int // accepted max price for chunk
SellAt *big.Int // offered sale price for chunk
PayAt uint // threshold that triggers payment request
DropAt uint // threshold that triggers disconnect
}
// Strategy encapsulates parameters relating to
// automatic deposit and automatic cashing
type Strategy struct {
AutoCashInterval time.Duration // default interval for autocash
AutoCashThreshold *big.Int // threshold that triggers autocash (wei)
AutoDepositInterval time.Duration // default interval for autocash
AutoDepositThreshold *big.Int // threshold that triggers autodeposit (wei)
AutoDepositBuffer *big.Int // buffer that is surplus for fork protection etc (wei)
}
// Params extends the public profile with private parameters relating to
// automatic deposit and automatic cashing
type Params struct {
*Profile
*Strategy
}
// Promise
// 3rd party Provable Promise of Payment
// issued by outPayment
// serialisable to send with Protocol
type Promise interface{}
// interface for the peer protocol for testing or external alternative payment
type Protocol interface {
Pay(int, Promise) // units, payment proof
Drop()
String() string
}
// interface for the (delayed) ougoing payment system with autodeposit
type OutPayment interface {
Issue(amount *big.Int) (promise Promise, err error)
AutoDeposit(interval time.Duration, threshold, buffer *big.Int)
Stop()
}
// interface for the (delayed) incoming payment system with autocash
type InPayment interface {
Receive(promise Promise) (*big.Int, error)
AutoCash(cashInterval time.Duration, maxUncashed *big.Int)
Stop()
}
// swap is the swarm accounting protocol instance
// * pairwise accounting and payments
type Swap struct {
lock sync.Mutex // mutex for balance access
balance int // units of chunk/retrieval request
local *Params // local peer's swap parameters
remote *Profile // remote peer's swap profile
proto Protocol // peer communication protocol
Payment
}
type Payment struct {
Out OutPayment // outgoing payment handler
In InPayment // incoming payment handler
Buys, Sells bool
}
// swap constructor
func New(local *Params, pm Payment, proto Protocol) (self *Swap, err error) {
self = &Swap{
local: local,
Payment: pm,
proto: proto,
}
self.SetParams(local)
return
}
// entry point for setting remote swap profile (e.g from handshake or other message)
func (self *Swap) SetRemote(remote *Profile) {
defer self.lock.Unlock()
self.lock.Lock()
self.remote = remote
if self.Sells && (remote.BuyAt.Cmp(common.Big0) <= 0 || self.local.SellAt.Cmp(common.Big0) <= 0 || remote.BuyAt.Cmp(self.local.SellAt) < 0) {
self.Out.Stop()
self.Sells = false
}
if self.Buys && (remote.SellAt.Cmp(common.Big0) <= 0 || self.local.BuyAt.Cmp(common.Big0) <= 0 || self.local.BuyAt.Cmp(self.remote.SellAt) < 0) {
self.In.Stop()
self.Buys = false
}
glog.V(logger.Debug).Infof("<%v> remote profile set: pay at: %v, drop at: %v, buy at: %v, sell at: %v", self.proto, remote.PayAt, remote.DropAt, remote.BuyAt, remote.SellAt)
}
// to set strategy dynamically
func (self *Swap) SetParams(local *Params) {
defer self.lock.Unlock()
self.lock.Lock()
self.local = local
self.setParams(local)
}
// caller holds the lock
func (self *Swap) setParams(local *Params) {
if self.Sells {
self.In.AutoCash(local.AutoCashInterval, local.AutoCashThreshold)
glog.V(logger.Info).Infof("<%v> set autocash to every %v, max uncashed limit: %v", self.proto, local.AutoCashInterval, local.AutoCashThreshold)
} else {
glog.V(logger.Info).Infof("<%v> autocash off (not selling)", self.proto)
}
if self.Buys {
self.Out.AutoDeposit(local.AutoDepositInterval, local.AutoDepositThreshold, local.AutoDepositBuffer)
glog.V(logger.Info).Infof("<%v> set autodeposit to every %v, pay at: %v, buffer: %v", self.proto, local.AutoDepositInterval, local.AutoDepositThreshold, local.AutoDepositBuffer)
} else {
glog.V(logger.Info).Infof("<%v> autodeposit off (not buying)", self.proto)
}
}
// Add(n)
// n > 0 called when promised/provided n units of service
// n < 0 called when used/requested n units of service
func (self *Swap) Add(n int) error {
defer self.lock.Unlock()
self.lock.Lock()
self.balance += n
if !self.Sells && self.balance > 0 {
glog.V(logger.Detail).Infof("<%v> remote peer cannot have debt (balance: %v)", self.proto, self.balance)
self.proto.Drop()
return fmt.Errorf("[SWAP] <%v> remote peer cannot have debt (balance: %v)", self.proto, self.balance)
}
if !self.Buys && self.balance < 0 {
glog.V(logger.Detail).Infof("<%v> we cannot have debt (balance: %v)", self.proto, self.balance)
return fmt.Errorf("[SWAP] <%v> we cannot have debt (balance: %v)", self.proto, self.balance)
}
if self.balance >= int(self.local.DropAt) {
glog.V(logger.Detail).Infof("<%v> remote peer has too much debt (balance: %v, disconnect threshold: %v)", self.proto, self.balance, self.local.DropAt)
self.proto.Drop()
return fmt.Errorf("[SWAP] <%v> remote peer has too much debt (balance: %v, disconnect threshold: %v)", self.proto, self.balance, self.local.DropAt)
} else if self.balance <= -int(self.remote.PayAt) {
self.send()
}
return nil
}
func (self *Swap) Balance() int {
defer self.lock.Unlock()
self.lock.Lock()
return self.balance
}
// send(units) is called when payment is due
// In case of insolvency no promise is issued and sent, safe against fraud
// No return value: no error = payment is opportunistic = hang in till dropped
func (self *Swap) send() {
if self.local.BuyAt != nil && self.balance < 0 {
amount := big.NewInt(int64(-self.balance))
amount.Mul(amount, self.remote.SellAt)
promise, err := self.Out.Issue(amount)
if err != nil {
glog.V(logger.Warn).Infof("<%v> cannot issue cheque (amount: %v, channel: %v): %v", self.proto, amount, self.Out, err)
} else {
glog.V(logger.Warn).Infof("<%v> cheque issued (amount: %v, channel: %v)", self.proto, amount, self.Out)
self.proto.Pay(-self.balance, promise)
self.balance = 0
}
}
}
// receive(units, promise) is called by the protocol when a payment msg is received
// returns error if promise is invalid.
func (self *Swap) Receive(units int, promise Promise) error {
if units <= 0 {
return fmt.Errorf("invalid units: %v <= 0", units)
}
price := new(big.Int).SetInt64(int64(units))
price.Mul(price, self.local.SellAt)
amount, err := self.In.Receive(promise)
if err != nil {
err = fmt.Errorf("invalid promise: %v", err)
} else if price.Cmp(amount) != 0 {
// verify amount = units * unit sale price
return fmt.Errorf("invalid amount: %v = %v * %v (units sent in msg * agreed sale unit price) != %v (signed in cheque)", price, units, self.local.SellAt, amount)
}
if err != nil {
glog.V(logger.Detail).Infof("<%v> invalid promise (amount: %v, channel: %v): %v", self.proto, amount, self.In, err)
return err
}
// credit remote peer with units
self.Add(-units)
glog.V(logger.Detail).Infof("<%v> received promise (amount: %v, channel: %v): %v", self.proto, amount, self.In, promise)
return nil
}
// stop() causes autocash loop to terminate.
// Called after protocol handle loop terminates.
func (self *Swap) Stop() {
defer self.lock.Unlock()
self.lock.Lock()
if self.Buys {
self.Out.Stop()
}
if self.Sells {
self.In.Stop()
}
}
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