From eed1bf753db9574f53f0a8091672a5ae645ab4ee Mon Sep 17 00:00:00 2001
From: Ethan Frey <ethanfrey@users.noreply.github.com>
Date: Tue, 27 Jun 2017 19:22:25 +0200
Subject: [PATCH] Start separating middleware and handler

---
 handler.go       | 41 ++++++++++++++++++++++++++++++++---------
 handlers/base.go | 12 ++++++++++--
 handlers/sigs.go | 10 ++++++++--
 3 files changed, 50 insertions(+), 13 deletions(-)

diff --git a/handler.go b/handler.go
index cbc88d4fed..acebaa4981 100644
--- a/handler.go
+++ b/handler.go
@@ -9,11 +9,31 @@ import (
 	"github.com/tendermint/basecoin/types"
 )
 
+type Named interface {
+	Name() string
+}
+
+type Checker interface {
+	CheckTx(ctx Context, store types.KVStore, tx Tx) (Result, error)
+}
+
+type Deliver interface {
+	DeliverTx(ctx Context, store types.KVStore, tx Tx) (Result, error)
+}
+
+type CheckerMiddle interface {
+	CheckTx(ctx Context, store types.KVStore, tx Tx, next Checker) (Result, error)
+}
+
+type DeliverMiddle interface {
+	DeliverTx(ctx Context, store types.KVStore, tx Tx, next Deliver) (Result, error)
+}
+
 // Handler is anything that processes a transaction
 type Handler interface {
-	CheckTx(ctx Context, store types.KVStore, tx Tx) (Result, error)
-	DeliverTx(ctx Context, store types.KVStore, tx Tx) (Result, error)
-
+	Checker
+	Deliver
+	Named
 	// TODO: flesh these out as well
 	// SetOption(store types.KVStore, key, value string) (log string)
 	// InitChain(store types.KVStore, vals []*abci.Validator)
@@ -21,12 +41,15 @@ type Handler interface {
 	// EndBlock(store types.KVStore, height uint64) abci.ResponseEndBlock
 }
 
-// different apps to authorize
-const (
-	Sigs = "sigs"
-	IBC  = "ibc"
-	Role = "role"
-)
+// Middleware is anything that wraps another handler to enhance functionality.
+//
+// You can use utilities in handlers to construct them, the interfaces
+// are exposed in the top-level package to avoid import loops.
+type Middleware interface {
+	CheckerMiddle
+	DeliverMiddle
+	Named
+}
 
 // TODO: handle this in some secure way, only certain apps can add permissions
 type Permission struct {
diff --git a/handlers/base.go b/handlers/base.go
index 99a9ce08ad..26ca282a79 100644
--- a/handlers/base.go
+++ b/handlers/base.go
@@ -7,6 +7,10 @@ import (
 	"github.com/tendermint/basecoin/types"
 )
 
+const (
+	NameFee = "fee"
+)
+
 type AccountChecker interface {
 	// Get amount checks the current amount
 	GetAmount(store types.KVStore, addr []byte) (types.Coins, error)
@@ -26,6 +30,10 @@ func (h SimpleFeeHandler) Next() basecoin.Handler {
 	return h.Inner
 }
 
+func (_ SimpleFeeHandler) Name() string {
+	return NameFee
+}
+
 var _ basecoin.Handler = SimpleFeeHandler{}
 
 // Yes, I know refactor a bit... really too late already
@@ -41,7 +49,7 @@ func (h SimpleFeeHandler) CheckTx(ctx basecoin.Context, store types.KVStore, tx
 		return res, errors.InsufficientFees()
 	}
 
-	if !ctx.HasPermission(Sigs, feeTx.Payer) {
+	if !ctx.HasPermission(NameSigs, feeTx.Payer) {
 		return res, errors.Unauthorized()
 	}
 
@@ -64,7 +72,7 @@ func (h SimpleFeeHandler) DeliverTx(ctx basecoin.Context, store types.KVStore, t
 		return res, errors.InsufficientFees()
 	}
 
-	if !ctx.HasPermission(Sigs, feeTx.Payer) {
+	if !ctx.HasPermission(NameSigs, feeTx.Payer) {
 		return res, errors.Unauthorized()
 	}
 
diff --git a/handlers/sigs.go b/handlers/sigs.go
index 28baf8f8a1..50d80636e5 100644
--- a/handlers/sigs.go
+++ b/handlers/sigs.go
@@ -9,13 +9,19 @@ import (
 )
 
 // app name for auth
-const Sigs = "sigs"
+const (
+	NameSigs = "sigs"
+)
 
 type SignedHandler struct {
 	AllowMultiSig bool
 	Inner         basecoin.Handler
 }
 
+func (_ SignedHandler) Name() string {
+	return NameSigs
+}
+
 func (h SignedHandler) Next() basecoin.Handler {
 	return h.Inner
 }
@@ -65,7 +71,7 @@ func (h SignedHandler) DeliverTx(ctx basecoin.Context, store types.KVStore, tx b
 func addSigners(ctx basecoin.Context, sigs []crypto.PubKey) basecoin.Context {
 	perms := make([]basecoin.Permission, len(sigs))
 	for i, s := range sigs {
-		perms[i] = basecoin.Permission{App: Sigs, Address: s.Address()}
+		perms[i] = basecoin.Permission{App: NameSigs, Address: s.Address()}
 	}
 
 	// add the signers to the context and continue