From 6029f5c986a26f8c3dbbee908024ac7b8d8a00b6 Mon Sep 17 00:00:00 2001
From: Ethan Frey <ethanfrey@users.noreply.github.com>
Date: Thu, 18 May 2017 17:11:26 +0200
Subject: [PATCH] Introduce the concept of TxLayer

---
 tx.go            | 18 ++++++++++++++++++
 tx_test.go       | 35 +++++++++++++++++++++++++++++++++++
 txs/base.go      | 43 ++++++++++++++++++++++++++++++++-----------
 txs/sigs_test.go | 12 ++++++------
 4 files changed, 91 insertions(+), 17 deletions(-)
 create mode 100644 tx_test.go

diff --git a/tx.go b/tx.go
index 3ee3dc5fe..5a74a7f90 100644
--- a/tx.go
+++ b/tx.go
@@ -3,4 +3,22 @@ package basecoin
 // TODO: add some common functionality here...
 // +gen wrapper:"Tx"
 type TxInner interface {
+	Wrap() Tx
+}
+
+// TxLayer provides a standard way to deal with "middleware" tx,
+// That add context to an embedded tx.
+type TxLayer interface {
+	TxInner
+	Next() Tx
+}
+
+func (t Tx) IsLayer() bool {
+	_, ok := t.Unwrap().(TxLayer)
+	return ok
+}
+
+func (t Tx) GetLayer() TxLayer {
+	l, _ := t.Unwrap().(TxLayer)
+	return l
 }
diff --git a/tx_test.go b/tx_test.go
new file mode 100644
index 000000000..1d4894063
--- /dev/null
+++ b/tx_test.go
@@ -0,0 +1,35 @@
+package basecoin
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// define a Demo struct that implements TxLayer
+type Demo struct{}
+
+var _ TxLayer = Demo{}
+
+func (d Demo) Next() Tx { return Tx{} }
+func (d Demo) Wrap() Tx { return Tx{d} }
+
+// define a Fake struct that doesn't implement TxLayer
+type Fake struct{}
+
+func (f Fake) Wrap() Tx { return Tx{f} }
+
+// Make sure the layer
+func TestLayer(t *testing.T) {
+	assert := assert.New(t)
+
+	// a fake tx, just don't use it...
+	nl := Fake{}.Wrap()
+	assert.False(nl.IsLayer())
+	assert.Nil(nl.GetLayer())
+
+	// a tx containing a TxLayer should respond properly
+	l := Demo{}.Wrap()
+	assert.True(l.IsLayer())
+	assert.NotNil(l.GetLayer())
+}
diff --git a/txs/base.go b/txs/base.go
index 04ab877c3..384aafc29 100644
--- a/txs/base.go
+++ b/txs/base.go
@@ -30,29 +30,50 @@ const (
 
 func init() {
 	basecoin.TxMapper.
-		RegisterImplementation(data.Bytes{}, TypeRaw, ByteRaw).
+		RegisterImplementation(Raw{}, TypeRaw, ByteRaw).
 		RegisterImplementation(&Fee{}, TypeFees, ByteFees)
 }
 
-// WrapBytes converts data.Bytes into a Tx, so we
-// can just pass raw bytes and display in hex in json
-func WrapBytes(d []byte) basecoin.Tx {
-	return basecoin.Tx{data.Bytes(d)}
+// Raw just contains bytes that can be hex-ified
+type Raw struct {
+	data.Bytes
 }
 
-/**** One Sig ****/
+func (r Raw) Wrap() basecoin.Tx {
+	return basecoin.Tx{r}
+}
 
-// OneSig lets us wrap arbitrary data with a go-crypto signature
+func NewRaw(d []byte) Raw {
+	return Raw{data.Bytes(d)}
+}
+
+/**** Fee ****/
+
+// Fee attaches a fee payment to the embedded tx
 type Fee struct {
-	Tx  basecoin.Tx `json:"tx"`
-	Fee types.Coin  `json:"fee"`
+	Tx    basecoin.Tx `json:"tx"`
+	Fee   types.Coin  `json:"fee"`
+	Payer data.Bytes  `json:"payer"` // the address who pays the fee
 	// Gas types.Coin `json:"gas"`  // ?????
 }
 
-func NewFee(tx basecoin.Tx, fee types.Coin) *Fee {
-	return &Fee{Tx: tx, Fee: fee}
+func NewFee(tx basecoin.Tx, fee types.Coin, addr []byte) *Fee {
+	return &Fee{Tx: tx, Fee: fee, Payer: addr}
 }
 
 func (f *Fee) Wrap() basecoin.Tx {
 	return basecoin.Tx{f}
 }
+
+/**** MultiTx  ******/
+type MultiTx struct {
+	Txs []basecoin.Tx `json:"txs"`
+}
+
+func NewMultiTx(txs ...basecoin.Tx) *MultiTx {
+	return &MultiTx{Txs: txs}
+}
+
+func (mt *MultiTx) Wrap() basecoin.Tx {
+	return basecoin.Tx{mt}
+}
diff --git a/txs/sigs_test.go b/txs/sigs_test.go
index f0a5a2c99..1e51bff09 100644
--- a/txs/sigs_test.go
+++ b/txs/sigs_test.go
@@ -6,13 +6,13 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
-	"github.com/tendermint/basecoin"
 	crypto "github.com/tendermint/go-crypto"
 	keys "github.com/tendermint/go-crypto/keys"
 	"github.com/tendermint/go-crypto/keys/cryptostore"
 	"github.com/tendermint/go-crypto/keys/storage/memstorage"
 	wire "github.com/tendermint/go-wire"
-	"github.com/tendermint/go-wire/data"
+
+	"github.com/tendermint/basecoin"
 )
 
 func checkSignBytes(t *testing.T, bytes []byte, expected string) {
@@ -22,9 +22,9 @@ func checkSignBytes(t *testing.T, bytes []byte, expected string) {
 	require.Nil(t, err)
 
 	// now make sure this tx is data.Bytes with the info we want
-	byt, ok := preTx.Unwrap().(data.Bytes)
+	raw, ok := preTx.Unwrap().(Raw)
 	require.True(t, ok)
-	assert.Equal(t, expected, string(byt))
+	assert.Equal(t, expected, string(raw.Bytes))
 }
 
 func TestOneSig(t *testing.T) {
@@ -54,7 +54,7 @@ func TestOneSig(t *testing.T) {
 	}
 
 	for _, tc := range cases {
-		inner := WrapBytes([]byte(tc.data))
+		inner := NewRaw([]byte(tc.data)).Wrap()
 		tx := NewSig(inner)
 		// unsigned version
 		_, err = tx.Signers()
@@ -119,7 +119,7 @@ func TestMultiSig(t *testing.T) {
 	}
 
 	for _, tc := range cases {
-		inner := WrapBytes([]byte(tc.data))
+		inner := NewRaw([]byte(tc.data)).Wrap()
 		tx := NewMulti(inner)
 		// unsigned version
 		_, err = tx.Signers()