0g-chain/internal/x/paychan/keeper.go

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package paychan
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import (
"strconv"
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sdk "github.com/cosmos/cosmos-sdk/types"
"github.com/cosmos/cosmos-sdk/wire"
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)
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// keeper of the paychan store
type Keeper struct {
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storeKey sdk.StoreKey
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cdc *wire.Codec // needed to serialize objects before putting them in the store
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coinKeeper bank.Keeper
// codespace
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//codespace sdk.CodespaceType // ??
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}
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// Called when creating new app.
//func NewKeeper(cdc *wire.Codec, key sdk.StoreKey, ck bank.Keeper, codespace sdk.CodespaceType) Keeper {
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func NewKeeper(cdc *wire.Codec, key sdk.StoreKey, ck bank.Keeper) Keeper {
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keeper := Keeper{
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storeKey: key,
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cdc: cdc,
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coinKeeper: ck,
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//codespace: codespace,
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}
return keeper
}
// bunch of business logic ...
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// Reteive a payment channel struct from the blockchain store.
// They are indexed by a concatenation of sender address, receiver address, and an integer.
func (keeper Keeper) GetPaychan(ctx sdk.Context, sender sdk.Address, receiver sdk.Address, id integer) (Paychan, bool) {
// Return error as second argument instead of bool?
var pych Paychan
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// load from DB
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store := ctx.KVStore(k.storeKey)
bz := store.Get(paychanKey(sender, receiver, id))
if bz == nil {
return pych, false
}
// unmarshal
k.cdc.MustUnmarshalBinary(bz, &pych)
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// return
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return pych, true
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}
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// Store payment channel struct in blockchain store.
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func (keeper Keeper) setPaychan(pych Paychan) sdk.Error {
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store := ctx.KVStore(k.storeKey)
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// marshal
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bz := k.cdc.MustMarshalBinary(pych)
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// write to db
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pychKey := paychanKey(pych.sender, pych.receiver, pych.id)
store.Set(pychKey, bz)
// TODO handler errors
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}
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// Create a new payment channel and lock up sender funds.
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func (keeer Keeper) CreatePaychan(sender sdk.Address, receiver sdkAddress, amt sdk.Coins) (sdk.Tags, sdk.Error) {
// Calculate next id (num existing paychans plus 1)
id := len(keeper.GetPaychans(sender, receiver)) + 1
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// subtract coins from sender
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k.coinKeeper.SubtractCoins(ctx, sender, amt)
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// create new Paychan struct (create ID)
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pych := Paychan{sender,
receiver,
id,
balance: amt}
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// save to db
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err := k.setPaychan(pych)
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// TODO validation
// sender has enough coins - done in Subtract method
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// receiver address exists?
// paychan doesn't exist already
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tags := sdk.NewTags()
return tags, err
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}
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// Close a payment channel and distribute funds to participants.
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func (keeper Keeper) ClosePaychan(sender sdk.Address, receiver sdk.Address, id integer, receiverAmt sdk.Coins) (sdk.Tags, sdk.Error) {
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pych := GetPaychan(ctx, sender, receiver, id)
// compute coin distribution
senderAmt = pych.balance.Minus(receiverAmt) // Minus sdk.Coins method
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// add coins to sender
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k.coinKeeper.AddCoins(ctx, sender, senderAmt)
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// add coins to receiver
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k.coinKeeper.AddCoins(ctx, receiver, receiverAmt)
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// delete paychan from db
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pychKey := paychanKey(pych.sender, pych.receiver, pych.id)
store.Delete(pychKey)
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// TODO validation
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// paychan exists
// output coins are less than paychan balance
// sender and receiver addresses exist?
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//sdk.NewTags(
// "action", []byte("channel closure"),
// "receiver", receiver.Bytes(),
// "sender", sender.Bytes(),
// "id", ??)
tags := sdk.NewTags()
return tags, nil
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}
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// Creates a key to reference a paychan in the blockchain store.
func paychanKey(sender sdk.Address, receiver sdk.Address, id integer) []byte {
//sdk.Address is just a slice of bytes under a different name
//convert id to string then to byte slice
idAsBytes := []byte(strconv.Itoa(id))
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// concat sender and receiver and integer ID
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return append(sender.Bytes(), receiver.Bytes()..., idAsBytes...)
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}
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// Get all paychans between a given sender and receiver.
func (keeper Keeper) GetPaychans(sender sdk.Address, receiver sdk.Address) []Paychan {
var paychans []Paychan
// TODO Implement this
return paychans
}
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// maybe getAllPaychans(sender sdk.address) []Paychan