From 03f653b88e673ecf98e99f68c2ffae43674ac5cb Mon Sep 17 00:00:00 2001
From: whyrusleeping <why@ipfs.io>
Date: Sun, 28 Jul 2019 12:19:33 -0700
Subject: [PATCH] expose head change notifications through api

---
 api/api.go           |  2 ++
 api/struct.go        |  6 ++++++
 chain/store/store.go | 16 ++++++++++++----
 go.mod               |  1 -
 node/impl/full.go    |  4 ++++
 5 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/api/api.go b/api/api.go
index 2c9018bf0..5d46ef5fa 100644
--- a/api/api.go
+++ b/api/api.go
@@ -8,6 +8,7 @@ import (
 
 	"github.com/filecoin-project/go-lotus/chain"
 	"github.com/filecoin-project/go-lotus/chain/address"
+	"github.com/filecoin-project/go-lotus/chain/store"
 	"github.com/filecoin-project/go-lotus/chain/types"
 
 	"github.com/ipfs/go-cid"
@@ -64,6 +65,7 @@ type FullNode interface {
 	Common
 
 	// chain
+	ChainNotify(context.Context) (<-chan *store.HeadChange, error)
 	ChainHead(context.Context) (*types.TipSet, error)                // TODO: check serialization
 	ChainSubmitBlock(ctx context.Context, blk *chain.BlockMsg) error // TODO: check serialization
 	ChainGetRandomness(context.Context, *types.TipSet) ([]byte, error)
diff --git a/api/struct.go b/api/struct.go
index 3243bc6c3..430619d44 100644
--- a/api/struct.go
+++ b/api/struct.go
@@ -7,6 +7,7 @@ import (
 
 	"github.com/filecoin-project/go-lotus/chain"
 	"github.com/filecoin-project/go-lotus/chain/address"
+	"github.com/filecoin-project/go-lotus/chain/store"
 	"github.com/filecoin-project/go-lotus/chain/types"
 
 	"github.com/ipfs/go-cid"
@@ -37,6 +38,7 @@ type FullNodeStruct struct {
 	CommonStruct
 
 	Internal struct {
+		ChainNotify           func(context.Context) (<-chan *store.HeadChange, error)        `perm:"read"`
 		ChainSubmitBlock      func(ctx context.Context, blk *chain.BlockMsg) error           `perm:"write"`
 		ChainHead             func(context.Context) (*types.TipSet, error)                   `perm:"read"`
 		ChainGetRandomness    func(context.Context, *types.TipSet) ([]byte, error)           `perm:"read"`
@@ -179,6 +181,10 @@ func (c *FullNodeStruct) ChainGetBlockMessages(ctx context.Context, b cid.Cid) (
 	return c.Internal.ChainGetBlockMessages(ctx, b)
 }
 
+func (c *FullNodeStruct) ChainNotify(ctx context.Context) (<-chan *store.HeadChange, error) {
+	return c.Internal.ChainNotify(ctx)
+}
+
 var _ Common = &CommonStruct{}
 var _ FullNode = &FullNodeStruct{}
 var _ StorageMiner = &StorageMinerStruct{}
diff --git a/chain/store/store.go b/chain/store/store.go
index 2ada7e3d1..0275066f8 100644
--- a/chain/store/store.go
+++ b/chain/store/store.go
@@ -106,13 +106,21 @@ type HeadChange struct {
 	Val  *types.TipSet
 }
 
-func (cs *ChainStore) SubHeadChanges() chan *HeadChange {
+func (cs *ChainStore) SubHeadChanges(ctx context.Context) chan *HeadChange {
 	subch := cs.bestTips.Sub("headchange")
 	out := make(chan *HeadChange, 16)
 	go func() {
 		defer close(out)
-		for val := range subch {
-			out <- val.(*HeadChange)
+		for {
+			select {
+			case val, ok := <-subch:
+				if !ok {
+					return
+				}
+				out <- val.(*HeadChange)
+			case <-ctx.Done():
+				cs.bestTips.Unsub(subch)
+			}
 		}
 	}()
 	return out
@@ -465,7 +473,7 @@ func (cs *ChainStore) GetActor(addr address.Address) (*types.Actor, error) {
 }
 
 func (cs *ChainStore) WaitForMessage(ctx context.Context, mcid cid.Cid) (cid.Cid, *types.MessageReceipt, error) {
-	tsub := cs.SubHeadChanges()
+	tsub := cs.SubHeadChanges(ctx)
 
 	head := cs.GetHeaviestTipSet()
 
diff --git a/go.mod b/go.mod
index 399d591fb..e806e5c6d 100644
--- a/go.mod
+++ b/go.mod
@@ -7,7 +7,6 @@ require (
 	github.com/BurntSushi/toml v0.3.1
 	github.com/filecoin-project/go-bls-sigs v0.0.0-20190718224239-4bc4b8a7bbf8
 	github.com/filecoin-project/go-leb128 v0.0.0-20190212224330-8d79a5489543
-	github.com/filecoin-project/go-sectorbuilder v0.0.0-20190725115349-9b090e700325
 	github.com/gbrlsnchs/jwt/v3 v3.0.0-beta.1
 	github.com/gorilla/websocket v1.4.0
 	github.com/ipfs/go-bitswap v0.1.5
diff --git a/node/impl/full.go b/node/impl/full.go
index 8a467174f..e119ebe11 100644
--- a/node/impl/full.go
+++ b/node/impl/full.go
@@ -31,6 +31,10 @@ type FullNodeAPI struct {
 	Wallet *chain.Wallet
 }
 
+func (a *FullNodeAPI) ChainNotify(ctx context.Context) (<-chan *store.HeadChange, error) {
+	return a.Chain.SubHeadChanges(ctx), nil
+}
+
 func (a *FullNodeAPI) ChainSubmitBlock(ctx context.Context, blk *chain.BlockMsg) error {
 	if err := a.Chain.AddBlock(blk.Header); err != nil {
 		return err