From 6a3a37d5a69ca748e30e5b58d5b3e318c5885599 Mon Sep 17 00:00:00 2001
From: Jae Kwon <jae@tendermint.com>
Date: Fri, 1 Dec 2017 09:24:02 -0800
Subject: [PATCH] Update store types to new spec

---
 store/types.go | 44 +++++++++++++++++++++++---------------------
 1 file changed, 23 insertions(+), 21 deletions(-)

diff --git a/store/types.go b/store/types.go
index 44e2673d0..82388870e 100644
--- a/store/types.go
+++ b/store/types.go
@@ -9,8 +9,8 @@ type CommitID struct {
 	Hash    []byte
 }
 
-type (cid CommitID) IsZero() bool {
-	return cid.Version == 0  && len(cid.Hash) == 0
+func (cid CommitID) IsZero() bool {
+	return cid.Version == 0 && len(cid.Hash) == 0
 }
 
 type Committer interface {
@@ -21,42 +21,44 @@ type Committer interface {
 
 type CommitterLoader func(id CommitID) (Committer, error)
 
-// A Store is anything that can be wrapped with a cache.
-type CacheWrappable interface {
-
-	// CacheWrap() wraps a thing with a cache.  After calling
-	// .Write() on the CacheWrap, all previous CacheWraps on the
-	// object expire.
-	//
-	// CacheWrap() should not return a Committer, since Commit() on
-	// CacheWraps make no sense.  It can return KVStore, IterKVStore,
-	// etc.
-	//
-	// NOTE: https://dave.cheney.net/2017/07/22/should-go-2-0-support-generics.
-	// The returned object may or may not implement CacheWrap() as well.
-	CacheWrap() interface{}
-}
-
 // KVStore is a simple interface to get/set data
 type KVStore interface {
-	CacheWrappable // CacheWrap returns KVStore
-
 	Set(key, value []byte) (prev []byte)
 	Get(key []byte) (value []byte, exists bool)
 	Has(key []byte) (exists bool)
 	Remove(key []byte) (prev []byte, removed bool)
+
+	// CacheKVStore() wraps a thing with a cache.  After
+	// calling .Write() on the CacheKVStore, all previous
+	// CacheWraps on the object expire.
+	CacheKVStore() CacheKVStore
+}
+
+type CacheKVStore interface {
+	KVStore
+	Write() // Writes operations to underlying KVStore
 }
 
 // IterKVStore can be iterated on
 // CONTRACT: No writes may happen within a domain while an iterator exists over it.
 type IterKVStore interface {
-	KVStore // CacheWrap returns IterKVMap
+	KVStore
 
 	Iterator(start, end []byte) Iterator
 	ReverseIterator(start, end []byte) Iterator
 
 	First(start, end []byte) (kv KVPair, ok bool)
 	Last(start, end []byte) (kv KVPair, ok bool)
+
+	// CacheIterKVStore() wraps a thing with a cache.
+	// After calling .Write() on the CacheIterKVStore, all
+	// previous CacheWraps on the object expire.
+	CacheIterKVStore() CacheIterKVStore
+}
+
+type CacheIterKVStore interface {
+	IterKVStore
+	Write() // Writes operations to underlying KVStore
 }
 
 type KVPair struct {