[VOL-1349] EPON OLT adapter (package B)

Change-Id: I634ef62c53813dcf4456f54948f13e06358e263c
diff --git a/internal/pkg/core/l2oam/onu_list_access.go b/internal/pkg/core/l2oam/onu_list_access.go
new file mode 100644
index 0000000..0ca4714
--- /dev/null
+++ b/internal/pkg/core/l2oam/onu_list_access.go
@@ -0,0 +1,137 @@
+/*
+ * Copyright 2020-present Open Networking Foundation
+
+ * 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 l2oam
+
+import (
+	"encoding/json"
+	"io/ioutil"
+	"os"
+)
+
+// JSON file name
+const jsonname = "/onu_list.json"
+
+// OnuStatus has ONU status
+type OnuStatus struct {
+	ID           string `json:"id"`
+	AdminState   string `json:"admin_state"`
+	OpeState     string `json:"ope_state"`
+	ConnectState string `json:"con_state"`
+	MacAddress   string `json:"mac_addr"`
+	RebootState  string `json:"reboot_state"`
+}
+
+// ReadOnuStatusList reads JSON file
+func ReadOnuStatusList() ([]OnuStatus, error) {
+	bytes, err := ioutil.ReadFile(os.Getenv("HOME") + jsonname)
+	if err != nil && os.IsNotExist(err) {
+		return nil, nil
+	}
+	var onuList []OnuStatus
+	if err := json.Unmarshal(bytes, &onuList); err != nil {
+		return nil, err
+	}
+	return onuList, nil
+}
+
+// WriteOnuStatusList writes JSON file
+func WriteOnuStatusList(list []OnuStatus) error {
+	bytes, err := json.Marshal(list)
+	if err != nil {
+		return err
+	}
+	return ioutil.WriteFile(os.Getenv("HOME")+jsonname, bytes, 0644)
+}
+
+// AddOnu adds ONU to ONU status list
+func AddOnu(sts *OnuStatus) error {
+	list, err := ReadOnuStatusList()
+	if err != nil {
+		return err
+	}
+	if list == nil {
+		newList := []OnuStatus{*sts}
+		return WriteOnuStatusList(newList)
+	}
+	return WriteOnuStatusList(append(list, *sts))
+}
+
+// UpdateOnu updates ONU status
+func UpdateOnu(upSts *OnuStatus) error {
+	list, err := ReadOnuStatusList()
+	if (err != nil) || (list == nil) {
+		return err
+	}
+	newList := []OnuStatus{}
+	for _, sts := range list {
+		if sts.ID == upSts.ID {
+			newList = append(newList, *upSts)
+		} else {
+			newList = append(newList, sts)
+		}
+	}
+	return WriteOnuStatusList(newList)
+}
+
+// RemoveOnu removes ONU from ONU status list
+func RemoveOnu(id string) error {
+	list, err := ReadOnuStatusList()
+	if (err != nil) || (list == nil) {
+		return err
+	}
+	newList := []OnuStatus{}
+	for _, sts := range list {
+		if sts.ID != id {
+			newList = append(newList, sts)
+		}
+	}
+	return WriteOnuStatusList(newList)
+}
+
+// GetOnuFromDeviceID returns ONU status from ONU status list using its device ID
+func GetOnuFromDeviceID(id string) (*OnuStatus, error) {
+	list, err := ReadOnuStatusList()
+	if err != nil {
+		return nil, err
+	}
+	if list == nil {
+		return nil, nil
+	}
+	for _, sts := range list {
+		if sts.ID != id {
+			return &sts, nil
+		}
+	}
+	return nil, nil
+}
+
+// GetOnuFromMacAddr returns ONU status from ONU status list using its MAC address
+func GetOnuFromMacAddr(addr string) (*OnuStatus, error) {
+	list, err := ReadOnuStatusList()
+	if err != nil {
+		return nil, err
+	}
+	if list == nil {
+		return nil, nil
+	}
+	for _, sts := range list {
+		if sts.MacAddress == addr {
+			return &sts, nil
+		}
+	}
+	return nil, nil
+}