From 423fdf01b54a1729626ee070c7ec7de05780690b Mon Sep 17 00:00:00 2001
From: Edvard <edvard@hubinette.me>
Date: Wed, 28 Nov 2018 15:40:15 +0100
Subject: [PATCH] Add log_chunker

---
 pkg/transformers/shared/log_chunker.go | 57 ++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)
 create mode 100644 pkg/transformers/shared/log_chunker.go

diff --git a/pkg/transformers/shared/log_chunker.go b/pkg/transformers/shared/log_chunker.go
new file mode 100644
index 00000000..259a7f84
--- /dev/null
+++ b/pkg/transformers/shared/log_chunker.go
@@ -0,0 +1,57 @@
+// Copyright 2018 Vulcanize
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package shared
+
+import (
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+)
+
+type LogChunker struct {
+	addressToNames map[string][]string
+	nameToTopic0   map[string]common.Hash
+}
+
+// Initialises a chunker by creating efficient lookup maps
+func NewLogChunker(transformerConfigs []TransformerConfig) LogChunker {
+	addressToNames := map[string][]string{}
+	nameToTopic0   := map[string]common.Hash{}
+
+	for _, config := range transformerConfigs {
+		for _, address := range config.ContractAddresses {
+			addressToNames[address] = append(addressToNames[address], config.TransformerName)
+			nameToTopic0[config.TransformerName] = common.HexToHash(config.Topic)
+		}
+	}
+
+	return LogChunker{
+		addressToNames,
+		nameToTopic0,
+	}
+}
+
+// Goes through an array of logs, associating relevant logs with transformers
+func (chunker LogChunker) ChunkLogs(logs []types.Log) (chunks map[string][]types.Log) {
+	for _, log := range logs {
+		// Topic0 is not unique to each transformer, also need to consider the contract address
+		relevantTransformers := chunker.addressToNames[log.Address.String()]
+		for _, transformer := range relevantTransformers {
+			if chunker.nameToTopic0[transformer] == log.Topics[0] {
+				chunks[transformer] = append(chunks[transformer], log)
+			}
+		}
+	}
+	return
+}