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servers.go
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servers.go
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//
// lurkcoin
// Copyright © 2020 by luk3yx
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program 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 Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
//
package lurkcoin
import (
"math/big"
"net/http"
"strings"
"sync"
"time"
)
// Most mutable fields in Server are private to prevent race conditions.
// Note that pendingTransactions has to be ordered to retain lurkcoinV2
// compatibility. If compatibiltiy is ever dropped, it could possibly become a
// map[string]Transaction to improve the efficiency of delete operations.
type Server struct {
UID string
Name string
balance Currency
targetBalance Currency
history []Transaction
pendingTransactions []Transaction
token string
WebhookURL string
lock *sync.RWMutex
modified bool
}
type ServerCollection interface {
GetServer(name string) *Server
}
var MaxTargetBalance = CurrencyFromInt64(500000000)
func (self *Server) GetBalance() Currency {
self.lock.RLock()
defer self.lock.RUnlock()
return self.balance
}
func (self *Server) GetTargetBalance() Currency {
self.lock.RLock()
defer self.lock.RUnlock()
return self.targetBalance
}
// Changes the user's balance, returns false if the user does not have enough
// money. This is an atomic operation, changing the balance manually is not
// recommended.
func (self *Server) ChangeBal(num Currency) bool {
self.lock.Lock()
defer self.lock.Unlock()
new_balance := self.balance.Add(num)
if new_balance.LtZero() {
return false
}
self.balance = new_balance
self.modified = true
return true
}
// Gets the server's history. The slice returned can be modified, however the
// transaction objects should not be.
func (self *Server) GetHistory() []Transaction {
self.lock.RLock()
defer self.lock.RUnlock()
res := make([]Transaction, len(self.history))
copy(res, self.history)
return res
}
var webhookClient = &http.Client{Timeout: time.Second * 5}
func (self *Server) AddToHistory(transaction Transaction) {
self.lock.Lock()
defer self.lock.Unlock()
self.modified = true
// Prepend transaction to self.history
// https://stackoverflow.com/a/53737602
if len(self.history) < 10 {
// Only increase the length of the slice if it is shorter than 10
// elements long, meaning the transaction history cannot be longer
// than 10 elements.
self.history = append(self.history, Transaction{})
}
copy(self.history[1:], self.history)
self.history[0] = transaction
if self.Name != transaction.TargetServer || transaction.Target == "" {
return
}
// Add to pending transactions.
self.pendingTransactions = append(self.pendingTransactions, transaction)
// Validate the webhook URL (if any).
if self.WebhookURL == "" {
return
}
// Send a request to the webhook (in a separate goroutine so it doesn't
// block anything).
go func(webhookURL string) {
url, ok := ValidateWebhookURL(webhookURL)
if !ok {
return
}
reader := strings.NewReader(`{"version": 0}`)
req, err := http.NewRequest("POST", url, reader)
if err != nil {
return
}
req.Header.Set("Content-Type", "application/json")
req.Header.Set("User-Agent", "lurkcoin/3.0")
res, err := webhookClient.Do(req)
if err == nil {
res.Body.Close()
}
}(self.WebhookURL)
}
// Get a list of pending transactions, similar to GetHistory().
func (self *Server) GetPendingTransactions() []Transaction {
self.lock.RLock()
defer self.lock.RUnlock()
res := make([]Transaction, len(self.pendingTransactions))
copy(res, self.pendingTransactions)
return res
}
// Returns true if the server has pending transactions.
func (self *Server) HasPendingTransactions() bool {
self.lock.RLock()
defer self.lock.RUnlock()
return len(self.pendingTransactions) > 0
}
func (self *Server) removeAndReturnPendingTransaction(id string) *Transaction {
self.lock.Lock()
defer self.lock.Unlock()
for i, transaction := range self.pendingTransactions {
if transaction.ID == id {
// Although Currency objects are not themselves pointers, they
// contain a pointer to a big.Int object.
l := len(self.pendingTransactions) - 1
if i < l {
copy(self.pendingTransactions[i:],
self.pendingTransactions[i+1:])
}
self.pendingTransactions[l] = Transaction{}
self.pendingTransactions = self.pendingTransactions[:l]
self.modified = true
return &transaction
}
}
return nil
}
// Remove a pending transaction given its ID.
func (self *Server) RemovePendingTransaction(id string) {
self.removeAndReturnPendingTransaction(id)
}
// Reject (and possibly revert) a pending transaction.
func (self *Server) RejectPendingTransaction(id string,
tr *DatabaseTransaction) {
if tr == nil {
panic("nil *DatabaseTransaction passed to RejectPendingTransaction().")
}
// Get the transaction and ensure
transaction := self.removeAndReturnPendingTransaction(id)
if transaction == nil || !transaction.Revertable {
return
}
// Defer to a goroutine to prevent deadlocks
// TODO: Do this in the current goroutine
db := tr.GetRawDatabase()
currentUID := self.UID
go func() {
// Get the current server (the existing object is now invalid) and the
// source server.
tr := BeginDbTransaction(db)
defer tr.Abort()
servers, ok, _ := tr.GetServers(currentUID, transaction.SourceServer)
if !ok {
return
}
// To try and prevent exploits, the received amount is used and exchange
// rates are re-calculated.
// Note that the source and target get flipped here.
servers[0].Pay(transaction.Target, transaction.Source, servers[1],
transaction.ReceivedAmount, true, false)
tr.Finish()
}()
}
// Remove the first <amount> pending transactions.
// This is here to support lurkcoinV2 and probably shouldn't be used outside of
// that.
func (self *Server) RemoveFirstPendingTransactions(amount int) {
self.lock.Lock()
defer self.lock.Unlock()
if amount < 1 {
return
}
self.modified = true
l := len(self.pendingTransactions)
copy(self.pendingTransactions, self.pendingTransactions[amount:])
for i := l - amount; i < l; i++ {
self.pendingTransactions[i] = Transaction{}
}
self.pendingTransactions = self.pendingTransactions[:l-amount]
}
// Sets the target balance.
func (self *Server) SetTargetBalance(targetBalance Currency) bool {
if targetBalance.LtZero() || targetBalance.Gt(MaxTargetBalance) {
return false
}
self.lock.Lock()
defer self.lock.Unlock()
self.modified = true
self.targetBalance = targetBalance
return true
}
// Validates and sets a webhook URL.
func (self *Server) SetWebhookURL(webhookURL string) (ok bool) {
var safeURL string
if webhookURL == "" {
// Allow clearing the webhook URL
safeURL, ok = "", true
} else {
// This calls ValidateWebhookURL() so that the URL does not change if
// the rules are relaxed in the future.
safeURL, ok = ValidateWebhookURL(webhookURL)
}
if !ok {
return
}
self.lock.Lock()
defer self.lock.Unlock()
self.modified = true
self.WebhookURL = safeURL
return
}
// Gets the exchange rate.
// GetExchangeRate(<lurkcoins>, false) → <local currency>
// GetExchangeRate(<local currency>, true) → <lurkcoins>
var f2 = big.NewFloat(2)
// Exchange rate calculations are horrible at the moment, however they work
// (at least I think they work).
func (self *Server) GetExchangeRate(amount Currency, toLurkcoin bool) (Currency,
*big.Float) {
self.lock.RLock()
defer self.lock.RUnlock()
// Do nothing if the amount is 0 or fixed exchange rates are enabled.
if amount.IsZero() || self.targetBalance.IsZero() {
return amount, big.NewFloat(1)
}
// bal = max(self.balance, 0.01)
bal := self.balance
if !bal.GtZero() {
bal = CurrencyFromString("0.01")
}
// base_exchange = self.TargetBal / bal
base_exchange := self.targetBalance.Div(bal)
// To lurkcoin: adj_bal = bal - amount / base_exchange
// From lurkcoin: adj_bal = bal + amount
var adj_bal Currency
if toLurkcoin {
adj_bal = bal.Sub(CurrencyFromFloat(new(big.Float).Quo(amount.Float(),
base_exchange)))
} else {
adj_bal = bal.Add(amount)
}
// Calculate the "pre-emptive" exchange rate and average the two.
preemptive := new(big.Float).Add(base_exchange,
self.targetBalance.Div(adj_bal))
exchange := new(big.Float).Quo(preemptive, f2)
// Multiply (or divide) the exchange rate and the amount
res := new(big.Float)
if toLurkcoin {
res.Quo(amount.Float(), exchange)
} else {
res.Mul(amount.Float(), exchange)
}
return CurrencyFromFloat(res), exchange
}
// Regenerates the token and returns the new one.
func (self *Server) RegenerateToken() string {
self.lock.Lock()
defer self.lock.Unlock()
self.token = GenerateToken()
self.modified = true
return self.token
}
// "Encoded" servers that have all their values public
type EncodedServer struct {
// A version number for breaking changes, because of the way gob works this
// can be upgraded to a uint16/uint32 at a later time.
Version uint8 `json:"version"`
// The server name (not passed through HomogeniseUsername)
Name string `json:"name"`
// The balance in integer form where 1234 is ¤12.34.
Balance *big.Int `json:"balance"`
// The target balance in the same format as the above balance.
TargetBalance *big.Int `json:"target_balance"`
// Other values
History []Transaction `json:"history"`
PendingTransactions []Transaction `json:"pending_transactions"`
Token string `json:"token"`
WebhookURL string `json:"webhook_url"`
}
func (self *Server) IsModified() bool {
self.lock.RLock()
defer self.lock.RUnlock()
return self.modified
}
func (self *Server) SetModified() {
self.lock.Lock()
defer self.lock.Unlock()
self.modified = true
}
func (self *Server) Encode() EncodedServer {
self.lock.RLock()
defer self.lock.RUnlock()
history := make([]Transaction, len(self.history))
copy(history, self.history)
pendingTransactions := make([]Transaction, len(self.pendingTransactions))
copy(pendingTransactions, self.pendingTransactions)
return EncodedServer{0, self.Name, self.balance.Int(),
self.targetBalance.Int(), history, pendingTransactions, self.token,
self.WebhookURL}
}
func (self *EncodedServer) Decode() *Server {
if self.Version > 0 {
panic("Unrecognised EncodedServer version!")
}
if self.Balance == nil || self.TargetBalance == nil {
panic("Invalid EncodedServer passed to EncodedServer.Decode()!")
}
// Convert Balance and TargetBalance to Currency.
balance := CurrencyFromInt(self.Balance)
targetBalance := CurrencyFromInt(self.TargetBalance)
// Copy History and PendingTransactions.
history := make([]Transaction, len(self.History))
copy(history, self.History)
pendingTransactions := make([]Transaction, len(self.PendingTransactions))
copy(pendingTransactions, self.PendingTransactions)
return &Server{HomogeniseUsername(self.Name), self.Name, balance,
targetBalance, history, pendingTransactions, self.Token,
self.WebhookURL, new(sync.RWMutex), false}
}
// Summaries
type Summary struct {
UID string `json:"uid"`
Name string `json:"name"`
Bal Currency `json:"bal"`
Balance string `json:"balance"`
History []Transaction `json:"history"`
InterestRate float64 `json:"interest_rate"`
TargetBalance Currency `json:"target_balance"`
}
func (self *Server) GetSummary() Summary {
self.lock.RLock()
defer self.lock.RUnlock()
return Summary{self.UID, self.Name, self.balance, self.balance.String(),
self.GetHistory(), 0, self.targetBalance}
}
// Check an API token.
// WARNING: This may leak the length of the stored token, however that is
// probably already deducible by inspecting GenerateToken().
func (self *Server) CheckToken(token string) bool {
if self.token == "" {
return false
}
return ConstantTimeCompare(self.token, token)
}
// Make a new server
// The default target balance is currently ¤500,000.
const DefaultTargetBalance int64 = 500000
func NewServer(name string) *Server {
var server EncodedServer
server.Version = 0
server.Name = name
server.Balance = new(big.Int).SetInt64(0)
server.TargetBalance = new(big.Int).SetInt64(DefaultTargetBalance * 100)
server.Token = GenerateToken()
res := server.Decode()
res.SetModified()
return res
}