Merge pull request nanmu42#58 from avislash/add-getblock-by-timestamp

This PR resolves nanmu42#57 .

Author: nanmu42

block.go

@@ -7,6 +7,8 @@
 
 package etherscan
 
+import "strconv"
+
 // BlockReward gets block and uncle rewards by block number
 func (c *Client) BlockReward(blockNum int) (rewards BlockRewards, err error) {
 	param := M{
@@ -16,3 +18,22 @@ func (c *Client) BlockReward(blockNum int) (rewards BlockRewards, err error) {
 	err = c.call("block", "getblockreward", param, &rewards)
 	return
 }
+
+// BlockNumber gets closest block number by UNIX timestamp
+func (c *Client) BlockNumber(timestamp int64, closest string) (blockNumber int, err error) {
+	var result string
+	param := M{
+		"timestamp": strconv.Itoa(int(timestamp)),
+		"closest":   closest,
+	}
+
+	err = c.call("block", "getblocknobytime", param, &result)
+
+	if err != nil {
+		return
+	}
+
+	blockNum, err := strconv.ParseInt(result, 10, 64)
+	blockNumber = int(blockNum)
+	return
+}

block_e2e_test.go

@@ -24,3 +24,23 @@ func TestClient_BlockReward(t *testing.T) {
 		t.Errorf("api.BlockReward not working, got %s, want %s", j, ans)
 	}
 }
+
+func TestClient_BlockNumber(t *testing.T) {
+	//Note: All values taken from docs.etherscan.io/api-endpoints/blocks
+	const ans_before = 9251482
+	const ans_after = 9251483
+
+	blockNumber, err := api.BlockNumber(1578638524, "before")
+	noError(t, err, "api.BlockNumber")
+
+	if blockNumber != ans_before {
+		t.Errorf(`api.BlockNumber(1578638524, "before") not working, got %d, want %d`, blockNumber, ans_before)
+	}
+
+	blockNumber, err = api.BlockNumber(1578638524, "after")
+	noError(t, err, "api.BlockNumber")
+
+	if blockNumber != ans_after {
+		t.Errorf(`api.BlockNumber(1578638524,"after") not working, got %d, want %d`, blockNumber, ans_after)
+	}
+}