From f5a12a8d3f7ae9eeb7164a6c163f4a321e41479b Mon Sep 17 00:00:00 2001
From: Ian Norden <iannordenn@gmail.com>
Date: Thu, 10 Sep 2020 22:53:34 -0500
Subject: [PATCH] Iterator.Next() method

---
 postgres/database.go |  2 +-
 postgres/iterator.go | 42 ++++++++++++++++++++++++------------------
 postgres/util.go     |  2 +-
 3 files changed, 26 insertions(+), 20 deletions(-)

diff --git a/postgres/database.go b/postgres/database.go
index b2d9f71..0774bd3 100644
--- a/postgres/database.go
+++ b/postgres/database.go
@@ -29,7 +29,7 @@ import (
 
 var errNotSupported = errors.New("this operation is not supported")
 
-var (
+const (
 	hasPgStr         = "SELECT exists(select 1 from eth.key_preimages WHERE eth_key = $1)"
 	getPgStr         = "SELECT data FROM public.blocks INNER JOIN eth.key_preimages ON (ipfs_key = blocks.key) WHERE eth_key = $1"
 	putPgStr         = "INSERT INTO public.blocks (key, data) VALUES ($1, $2) ON CONFLICT (key) DO NOTHING"
diff --git a/postgres/iterator.go b/postgres/iterator.go
index f673729..656a56e 100644
--- a/postgres/iterator.go
+++ b/postgres/iterator.go
@@ -19,17 +19,25 @@ package pgipfsethdb
 import (
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/jmoiron/sqlx"
+	"github.com/sirupsen/logrus"
 )
 
+const (
+	nextPgStr = `SELECT key, data FROM public.blocks
+				INNER JOIN eth.key_preimages ON (ipfs_key = key)
+				WHERE eth_key > $1 ORDER BY eth_key LIMIT 1`
+)
+
+type nextModel struct {
+	Key   []byte `db:"eth_key"`
+	Value []byte `db:"data"`
+}
+
 // Iterator is the type that satisfies the ethdb.Iterator interface for PG-IPFS Ethereum data using a direct Postgres connection
-// Iteratee interface is used in Geth for various tests, trie/sync_bloom.go (for fast sync),
-// rawdb.InspectDatabase, and the new core/state/snapshot features.
-// This should not be confused with trie.NodeIterator or state.NodeIteraor (which can be constructed
-// from the ethdb.KeyValueStoreand ethdb.Database interfaces)
 type Iterator struct {
-	db                 *sqlx.DB
-	currentKey, prefix []byte
-	err                error
+	db                               *sqlx.DB
+	currentKey, prefix, currentValue []byte
+	err                              error
 }
 
 // NewIterator returns an ethdb.Iterator interface for PG-IPFS
@@ -45,9 +53,14 @@ func NewIterator(start, prefix []byte, db *sqlx.DB) ethdb.Iterator {
 // Next moves the iterator to the next key/value pair
 // It returns whether the iterator is exhausted
 func (i *Iterator) Next() bool {
-	// this is complicated by the ipfs db keys not being the keccak256 hashes
-	// go-ethereum usage of this method expects the iteration to occur over keccak256 keys
-	panic("implement me: Next")
+	next := new(nextModel)
+	if err := i.db.Get(next, nextPgStr, i.currentKey); err != nil {
+		logrus.Errorf("iterator.Next() error: %v", err)
+		i.currentKey, i.currentValue = nil, nil
+		return false
+	}
+	i.currentKey, i.currentValue = next.Key, next.Value
+	return true
 }
 
 // Error satisfies the ethdb.Iterator interface
@@ -70,14 +83,7 @@ func (i *Iterator) Key() []byte {
 // The caller should not modify the contents of the returned slice
 // and its contents may change on the next call to Next
 func (i *Iterator) Value() []byte {
-	mhKey, err := MultihashKeyFromKeccak256(i.currentKey)
-	if err != nil {
-		i.err = err
-		return nil
-	}
-	var data []byte
-	i.err = i.db.Get(&data, getPgStr, mhKey)
-	return data
+	return i.currentValue
 }
 
 // Release satisfies the ethdb.Iterator interface
diff --git a/postgres/util.go b/postgres/util.go
index e2a11fe..19d02b3 100644
--- a/postgres/util.go
+++ b/postgres/util.go
@@ -49,9 +49,9 @@ func DatastoreKeyFromGethKey(h []byte) (string, error) {
 	case Prefixed, Suffixed:
 		// This data is not mapped by hash => content by geth, store it using the prefixed/suffixed key directly
 		// I.e. the public.blocks datastore key == the hex representation of the geth key
+		// Alternatively, decompose the data and derive the hash
 		return common.Bytes2Hex(h), nil
 	default:
 		return "", fmt.Errorf("invalid formatting of database key: %x", h)
 	}
-
 }