1 files changed, 254 insertions, 0 deletions
diff --git a/swarm/services/swap/swap/swap.go b/swarm/services/swap/swap/swap.go
new file mode 100644
index 000000000..9d5da7c3a
--- /dev/null
+++ b/swarm/services/swap/swap/swap.go
@@ -0,0 +1,254 @@
+// 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()
+	}
+}