package paychan import ( "strconv" sdk "github.com/cosmos/cosmos-sdk/types" "github.com/cosmos/cosmos-sdk/wire" "github.com/cosmos/cosmos-sdk/x/bank" ) // keeper of the paychan store // Handles validation internally. Does not rely on calling code to do validation. // Aim to keep public methids safe, private ones not necessaily. type Keeper struct { storeKey sdk.StoreKey cdc *wire.Codec // needed to serialize objects before putting them in the store coinKeeper bank.Keeper // codespace //codespace sdk.CodespaceType // ?? } // Called when creating new app. //func NewKeeper(cdc *wire.Codec, key sdk.StoreKey, ck bank.Keeper, codespace sdk.CodespaceType) Keeper { func NewKeeper(cdc *wire.Codec, key sdk.StoreKey, ck bank.Keeper) Keeper { keeper := Keeper{ storeKey: key, cdc: cdc, coinKeeper: ck, //codespace: codespace, } return keeper } // bunch of business logic ... // Reteive a payment channel struct from the blockchain store. // They are indexed by a concatenation of sender address, receiver address, and an integer. func (k Keeper) GetPaychan(ctx sdk.Context, sender sdk.Address, receiver sdk.Address, id int64) (Paychan, bool) { // Return error as second argument instead of bool? var pych Paychan // load from DB store := ctx.KVStore(k.storeKey) bz := store.Get(paychanKey(sender, receiver, id)) if bz == nil { return pych, false } // unmarshal k.cdc.MustUnmarshalBinary(bz, &pych) // return return pych, true } // Store payment channel struct in blockchain store. func (k Keeper) setPaychan(ctx sdk.Context, pych Paychan) { store := ctx.KVStore(k.storeKey) // marshal bz := k.cdc.MustMarshalBinary(pych) // panics if something goes wrong // write to db pychKey := paychanKey(pych.Sender, pych.Receiver, pych.Id) store.Set(pychKey, bz) // panics if something goes wrong } // Create a new payment channel and lock up sender funds. func (k Keeper) CreatePaychan(ctx sdk.Context, sender sdk.Address, receiver sdk.Address, amount sdk.Coins) (sdk.Tags, sdk.Error) { // TODO move validation somewhere nicer // args present if len(sender) == 0 { return nil, sdk.ErrInvalidAddress(sender.String()) } if len(receiver) == 0 { return nil, sdk.ErrInvalidAddress(receiver.String()) } if len(amount) == 0 { return nil, sdk.ErrInvalidCoins(amount.String()) } // Check if coins are sorted, non zero, positive if !amount.IsValid() { return nil, sdk.ErrInvalidCoins(amount.String()) } if !amount.IsPositive() { return nil, sdk.ErrInvalidCoins(amount.String()) } // sender should exist already as they had to sign. // receiver address exists. am is the account mapper in the coin keeper. // TODO automatically create account if not present? // TODO remove as account mapper not available to this pkg //if k.coinKeeper.am.GetAccount(ctx, receiver) == nil { // return nil, sdk.ErrUnknownAddress(receiver.String()) //} // sender has enough coins - done in Subtract method // TODO check if sender and receiver different? // Calculate next id (just num of existing paychans - zero indexed) id := int64(len(k.GetPaychans(sender, receiver))) // subtract coins from sender _, tags, err := k.coinKeeper.SubtractCoins(ctx, sender, amount) if err != nil { return nil, err } // create new Paychan struct pych := Paychan{ Sender: sender, Receiver: receiver, Id: id, Balance: amount, } // save to db k.setPaychan(ctx, pych) // TODO create tags //tags := sdk.NewTags() return tags, err } // Close a payment channel and distribute funds to participants. func (k Keeper) ClosePaychan(ctx sdk.Context, sender sdk.Address, receiver sdk.Address, id int64, receiverAmount sdk.Coins) (sdk.Tags, sdk.Error) { if len(sender) == 0 { return nil, sdk.ErrInvalidAddress(sender.String()) } if len(receiver) == 0 { return nil, sdk.ErrInvalidAddress(receiver.String()) } if len(receiverAmount) == 0 { return nil, sdk.ErrInvalidCoins(receiverAmount.String()) } // check id ≥ 0 if id < 0 { return nil, sdk.ErrInvalidAddress(strconv.Itoa(int(id))) // TODO implement custom errors } // Check if coins are sorted, non zero, non negative if !receiverAmount.IsValid() { return nil, sdk.ErrInvalidCoins(receiverAmount.String()) } if !receiverAmount.IsPositive() { return nil, sdk.ErrInvalidCoins(receiverAmount.String()) } store := ctx.KVStore(k.storeKey) pych, exists := k.GetPaychan(ctx, sender, receiver, id) if !exists { return nil, sdk.ErrUnknownAddress("paychan not found") // TODO implement custom errors } // compute coin distribution senderAmount := pych.Balance.Minus(receiverAmount) // Minus sdk.Coins method // check that receiverAmt not greater than paychan balance if !senderAmount.IsNotNegative() { return nil, sdk.ErrInsufficientFunds(pych.Balance.String()) } // add coins to sender // creating account if it doesn't exist k.coinKeeper.AddCoins(ctx, sender, senderAmount) // add coins to receiver k.coinKeeper.AddCoins(ctx, receiver, receiverAmount) // delete paychan from db pychKey := paychanKey(pych.Sender, pych.Receiver, pych.Id) store.Delete(pychKey) // TODO create tags //sdk.NewTags( // "action", []byte("channel closure"), // "receiver", receiver.Bytes(), // "sender", sender.Bytes(), // "id", ??) tags := sdk.NewTags() return tags, nil } // Creates a key to reference a paychan in the blockchain store. func paychanKey(sender sdk.Address, receiver sdk.Address, id int64) []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(int(id))) // concat sender and receiver and integer ID key := append(sender.Bytes(), receiver.Bytes()...) key = append(key, idAsBytes...) return key } // Get all paychans between a given sender and receiver. func (k Keeper) GetPaychans(sender sdk.Address, receiver sdk.Address) []Paychan { var paychans []Paychan // TODO Implement this return paychans } // maybe getAllPaychans(sender sdk.address) []Paychan