From f4393511ee12ddbdd15dfc09e1bc3238a4846193 Mon Sep 17 00:00:00 2001
From: Ethan Frey <ethanfrey@users.noreply.github.com>
Date: Thu, 1 Jun 2017 20:01:19 +0200
Subject: [PATCH] First demo of handlers

---
 handler.go       | 53 +++++++++++++++++++++++++++++++++++++++++
 handlers/base.go | 61 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 114 insertions(+)
 create mode 100644 handler.go
 create mode 100644 handlers/base.go

diff --git a/handler.go b/handler.go
new file mode 100644
index 0000000000..704b2beee9
--- /dev/null
+++ b/handler.go
@@ -0,0 +1,53 @@
+package basecoin
+
+import (
+	abci "github.com/tendermint/abci/types"
+	crypto "github.com/tendermint/go-crypto"
+	"github.com/tendermint/go-wire/data"
+
+	"github.com/tendermint/basecoin/types"
+)
+
+// 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)
+
+	// TODO: flesh these out as well
+	// SetOption(store types.KVStore, key, value string) (log string)
+	// InitChain(store types.KVStore, vals []*abci.Validator)
+	// BeginBlock(store types.KVStore, hash []byte, header *abci.Header)
+	// EndBlock(store types.KVStore, height uint64) abci.ResponseEndBlock
+}
+
+// TODO: Context is a place-holder, soon we add some request data here from the
+// higher-levels (like tell an app who signed).
+// Trust me, we will need it like CallContext now...
+type Context struct {
+	sigs []crypto.PubKey
+}
+
+// TOTALLY insecure.  will redo later, but you get the point
+func (c Context) AddSigners(keys ...crypto.PubKey) Context {
+	return Context{
+		sigs: append(c.sigs, keys...),
+	}
+}
+
+func (c Context) GetSigners() []crypto.PubKey {
+	return c.sigs
+}
+
+// Result captures any non-error abci result
+// to make sure people use error for error cases
+type Result struct {
+	Data data.Bytes
+	Log  string
+}
+
+func (r Result) ToABCI() abci.Result {
+	return abci.Result{
+		Data: r.Data,
+		Log:  r.Log,
+	}
+}
diff --git a/handlers/base.go b/handlers/base.go
new file mode 100644
index 0000000000..a9c0329037
--- /dev/null
+++ b/handlers/base.go
@@ -0,0 +1,61 @@
+package handlers
+
+import (
+	crypto "github.com/tendermint/go-crypto"
+
+	"github.com/tendermint/basecoin"
+	"github.com/tendermint/basecoin/errors"
+	"github.com/tendermint/basecoin/types"
+)
+
+type SignedHandler struct {
+	AllowMultiSig bool
+	Inner         basecoin.Handler
+}
+
+func (h SignedHandler) Next() basecoin.Handler {
+	return h.Inner
+}
+
+var _ basecoin.Handler = SignedHandler{}
+
+type Signed interface {
+	basecoin.TxLayer
+	Signers() ([]crypto.PubKey, error)
+}
+
+func (h SignedHandler) CheckTx(ctx basecoin.Context, store types.KVStore, tx basecoin.Tx) (res basecoin.Result, err error) {
+	var sigs []crypto.PubKey
+
+	stx, ok := tx.Unwrap().(Signed)
+	if !ok {
+		return res, errors.Unauthorized()
+	}
+
+	sigs, err = stx.Signers()
+	if err != nil {
+		return res, err
+	}
+
+	// add the signers to the context and continue
+	ctx2 := ctx.AddSigners(sigs...)
+	return h.Next().CheckTx(ctx2, store, stx.Next())
+}
+
+func (h SignedHandler) DeliverTx(ctx basecoin.Context, store types.KVStore, tx basecoin.Tx) (res basecoin.Result, err error) {
+	var sigs []crypto.PubKey
+
+	stx, ok := tx.Unwrap().(Signed)
+	if !ok {
+		return res, errors.Unauthorized()
+	}
+
+	sigs, err = stx.Signers()
+	if err != nil {
+		return res, err
+	}
+
+	// add the signers to the context and continue
+	ctx2 := ctx.AddSigners(sigs...)
+	return h.Next().DeliverTx(ctx2, store, stx.Next())
+}