From 30eced21c5dddfaa4a541d3cbe31f17fb0aa13aa Mon Sep 17 00:00:00 2001
From: Ethan Frey <ethanfrey@users.noreply.github.com>
Date: Mon, 17 Jul 2017 21:52:02 +0200
Subject: [PATCH] Wrote bulk of ibc post packet middleware

---
 modules/ibc/middleware.go | 77 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 75 insertions(+), 2 deletions(-)

diff --git a/modules/ibc/middleware.go b/modules/ibc/middleware.go
index cb32ea603..869795149 100644
--- a/modules/ibc/middleware.go
+++ b/modules/ibc/middleware.go
@@ -1,6 +1,8 @@
 package ibc
 
 import (
+	"errors"
+
 	"github.com/tendermint/basecoin"
 	"github.com/tendermint/basecoin/stack"
 	"github.com/tendermint/basecoin/state"
@@ -27,11 +29,82 @@ func (Middleware) Name() string {
 // CheckTx verifies the named chain and height is present, and verifies
 // the merkle proof in the packet
 func (m Middleware) CheckTx(ctx basecoin.Context, store state.KVStore, tx basecoin.Tx, next basecoin.Checker) (res basecoin.Result, err error) {
-	return res, nil
+	// if it is not a PostPacket, just let it go through
+	post, ok := tx.Unwrap().(PostPacketTx)
+	if !ok {
+		return next.CheckTx(ctx, store, tx)
+	}
+
+	// parse this packet and get the ibc-enhanced tx and context
+	ictx, itx, err := m.verifyPost(ctx, store, post)
+	if err != nil {
+		return res, err
+	}
+	return next.CheckTx(ictx, store, itx)
 }
 
 // DeliverTx verifies the named chain and height is present, and verifies
 // the merkle proof in the packet
 func (m Middleware) DeliverTx(ctx basecoin.Context, store state.KVStore, tx basecoin.Tx, next basecoin.Deliver) (res basecoin.Result, err error) {
-	return res, nil
+	// if it is not a PostPacket, just let it go through
+	post, ok := tx.Unwrap().(PostPacketTx)
+	if !ok {
+		return next.DeliverTx(ctx, store, tx)
+	}
+
+	// parse this packet and get the ibc-enhanced tx and context
+	ictx, itx, err := m.verifyPost(ctx, store, post)
+	if err != nil {
+		return res, err
+	}
+	return next.DeliverTx(ictx, store, itx)
+}
+
+// verifyPost accepts a message bound for this chain...
+// TODO: think about relay
+func (m Middleware) verifyPost(ctx basecoin.Context, store state.KVStore,
+	tx PostPacketTx) (ictx basecoin.Context, itx basecoin.Tx, err error) {
+
+	// make sure the chain is registered
+	from := tx.FromChainID
+	if !NewChainSet(store).Exists([]byte(from)) {
+		err = ErrNotRegistered(from)
+		return
+	}
+
+	// make sure this sequence number is the next in the list
+	q := InputQueue(store, from)
+	packet := tx.Packet
+	if q.Tail() != packet.Sequence {
+		err = errors.New("Incorrect sequence number - out of order") // TODO
+		return
+	}
+
+	// look up the referenced header
+	space := stack.PrefixedStore(from, store)
+	provider := newDBProvider(space)
+	// TODO: GetExactHeight helper?
+	seed, err := provider.GetByHeight(int(tx.FromChainHeight))
+	if err != nil {
+		return ictx, itx, err
+	}
+	if seed.Height() != int(tx.FromChainHeight) {
+		err = errors.New("no such height") // TODO
+		return
+	}
+
+	// verify the merkle hash....
+	root := seed.Header.AppHash
+	key := []byte("?????") // TODO!
+	tx.Proof.Verify(key, packet.Bytes(), root)
+
+	// TODO: verify packet.Permissions
+
+	// add to input queue
+	q.Push(packet.Bytes())
+
+	// return the wrapped tx along with the extra permissions
+	ictx = ictx.WithPermissions(packet.Permissions...)
+	itx = packet.Tx
+	return
 }