Start on coin handler

modules/coin/handler.go

@@ -0,0 +1,64 @@
+package coin
+
+import (
+	"github.com/tendermint/basecoin"
+	"github.com/tendermint/basecoin/errors"
+	"github.com/tendermint/basecoin/types"
+)
+
+const (
+	NameCoin = "coin"
+)
+
+// Handler writes
+type Handler struct{}
+
+var _ basecoin.Handler = Handler{}
+
+func (_ Handler) Name() string {
+	return NameCoin
+}
+
+// CheckTx checks if there is enough money in the account
+func (h Handler) CheckTx(ctx basecoin.Context, store types.KVStore, tx basecoin.Tx) (res basecoin.Result, err error) {
+	_, err = checkTx(ctx, tx)
+	if err != nil {
+		return res, err
+	}
+
+	// now make sure there is money
+
+	// otherwise, we are good
+	return res, nil
+}
+
+// DeliverTx moves the money
+func (h Handler) DeliverTx(ctx basecoin.Context, store types.KVStore, tx basecoin.Tx) (res basecoin.Result, err error) {
+	_, err = checkTx(ctx, tx)
+	if err != nil {
+		return res, err
+	}
+
+	// now move the money
+	return basecoin.Result{}, nil
+}
+
+func checkTx(ctx basecoin.Context, tx basecoin.Tx) (*SendTx, error) {
+	// check if the tx is proper type and valid
+	send, ok := tx.Unwrap().(*SendTx)
+	if !ok {
+		return nil, errors.UnknownTxType(tx)
+	}
+	err := send.ValidateBasic()
+	if err != nil {
+		return nil, err
+	}
+
+	// check if all inputs have permission
+	for _, in := range send.Inputs {
+		if !ctx.HasPermission(in.Address) {
+			return nil, errors.Unauthorized()
+		}
+	}
+	return send, nil
+}

modules/coin/tx.go

@@ -98,15 +98,23 @@ func (tx SendTx) ValidateBasic() error {
 	if len(tx.Outputs) == 0 {
 		return errors.NoOutputs()
 	}
+	// make sure all inputs and outputs are individually valid
+	var totalIn, totalOut types.Coins
 	for _, in := range tx.Inputs {
 		if err := in.ValidateBasic(); err != nil {
 			return err
 		}
+		totalIn.Plus(in.Coins)
 	}
 	for _, out := range tx.Outputs {
 		if err := out.ValidateBasic(); err != nil {
 			return err
 		}
+		totalOut.Plus(out.Coins)
+	}
+	// make sure inputs and outputs match
+	if !totalIn.IsEqual(totalOut) {
+		return errors.InvalidCoins()
 	}
 	return nil
 }