[VOL-4648] Generate basic response with ID and type for get request on devices

Change-Id: I5899ab9c2ae4449863d88439719c9cdf2036c1f7
diff --git a/internal/core/adapter.go b/internal/core/adapter.go
new file mode 100644
index 0000000..a96767f
--- /dev/null
+++ b/internal/core/adapter.go
@@ -0,0 +1,54 @@
+/*
+* Copyright 2022-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 core
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/golang/protobuf/ptypes/empty"
+	"github.com/opencord/voltha-lib-go/v7/pkg/log"
+	"github.com/opencord/voltha-northbound-bbf-adapter/internal/clients"
+)
+
+var AdapterInstance *VolthaYangAdapter
+
+type VolthaYangAdapter struct {
+	volthaNbiClient *clients.VolthaNbiClient
+	oltAppClient    *clients.OltAppClient
+}
+
+func NewVolthaYangAdapter(nbiClient *clients.VolthaNbiClient, oltClient *clients.OltAppClient) *VolthaYangAdapter {
+	return &VolthaYangAdapter{
+		volthaNbiClient: nbiClient,
+		oltAppClient:    oltClient,
+	}
+}
+
+func (t *VolthaYangAdapter) GetDevices(ctx context.Context) ([]YangItem, error) {
+	devices, err := t.volthaNbiClient.Service.ListDevices(ctx, &empty.Empty{})
+	if err != nil {
+		err = fmt.Errorf("get-devices-failed: %v", err)
+		return nil, err
+	}
+
+	items := translateDevices(*devices)
+
+	logger.Debugw(ctx, "get-devices-success", log.Fields{"items": items})
+
+	return items, nil
+}
diff --git a/internal/core/logger.go b/internal/core/logger.go
new file mode 100644
index 0000000..0aa6eef
--- /dev/null
+++ b/internal/core/logger.go
@@ -0,0 +1,32 @@
+/*
+* Copyright 2022-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 core
+
+import (
+	"github.com/opencord/voltha-lib-go/v7/pkg/log"
+)
+
+var logger log.CLogger
+
+func init() {
+	// Setup this package so that it's log level can be modified at run time
+	var err error
+	logger, err = log.RegisterPackage(log.JSON, log.ErrorLevel, log.Fields{})
+	if err != nil {
+		panic(err)
+	}
+}
diff --git a/internal/core/translation.go b/internal/core/translation.go
new file mode 100644
index 0000000..bc7c692
--- /dev/null
+++ b/internal/core/translation.go
@@ -0,0 +1,67 @@
+/*
+* Copyright 2022-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 core
+
+import (
+	"fmt"
+
+	"github.com/opencord/voltha-protos/v5/go/voltha"
+)
+
+const (
+	DeviceAggregationModel = "bbf-device-aggregation"
+	DevicesPath            = "/" + DeviceAggregationModel + ":devices"
+	DeviceTypeOlt          = "bbf-device-types:olt"
+	DeviceTypeOnu          = "bbf-device-types:onu"
+)
+
+type YangItem struct {
+	Path  string
+	Value string
+}
+
+//getDevicePath returns the yang path to the root of the device with a specific ID
+func getDevicePath(id string) string {
+	return fmt.Sprintf("%s/device[name='%s']", DevicesPath, id)
+}
+
+//translateDevice returns a slice of yang items that represent a voltha device
+func translateDevice(device voltha.Device) []YangItem {
+	devicePath := getDevicePath(device.Id)
+
+	typeItem := YangItem{}
+	typeItem.Path = fmt.Sprintf("%s/type", devicePath)
+
+	if device.Root {
+		typeItem.Value = DeviceTypeOlt
+	} else {
+		typeItem.Value = DeviceTypeOnu
+	}
+
+	return []YangItem{typeItem}
+}
+
+//translateDevices returns a slice of yang items that represent a list of voltha devices
+func translateDevices(devices voltha.Devices) []YangItem {
+	result := []YangItem{}
+
+	for _, device := range devices.Items {
+		result = append(result, translateDevice(*device)...)
+	}
+
+	return result
+}
diff --git a/internal/core/translation_test.go b/internal/core/translation_test.go
new file mode 100644
index 0000000..fb2e751
--- /dev/null
+++ b/internal/core/translation_test.go
@@ -0,0 +1,101 @@
+/*
+* Copyright 2022-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 core
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/opencord/voltha-protos/v5/go/voltha"
+	"github.com/stretchr/testify/assert"
+)
+
+const (
+	testDeviceId = "123145abcdef"
+)
+
+func getItemWithPath(items []YangItem, path string) (value string, ok bool) {
+	for _, item := range items {
+		if item.Path == path {
+			return item.Value, true
+		}
+	}
+
+	return "", false
+}
+
+func TestDevicePath(t *testing.T) {
+	path := getDevicePath(testDeviceId)
+	assert.Equal(t, fmt.Sprintf("/bbf-device-aggregation:devices/device[name='%s']", testDeviceId), path)
+}
+
+func TestTranslateDevice(t *testing.T) {
+	olt := voltha.Device{
+		Id:   testDeviceId,
+		Root: true,
+	}
+	items := translateDevice(olt)
+
+	val, ok := getItemWithPath(items, fmt.Sprintf("%s/type", getDevicePath(testDeviceId)))
+	assert.True(t, ok, "No type item for olt")
+	assert.Equal(t, DeviceTypeOlt, val)
+
+	onu := voltha.Device{
+		Id:   testDeviceId,
+		Root: false,
+	}
+	items = translateDevice(onu)
+
+	val, ok = getItemWithPath(items, fmt.Sprintf("%s/type", getDevicePath(testDeviceId)))
+	assert.True(t, ok, "No type item for onu")
+	assert.Equal(t, DeviceTypeOnu, val)
+}
+
+func TestTranslateDevices(t *testing.T) {
+	devicesNum := 10
+
+	//Create test devices
+	devices := voltha.Devices{
+		Items: []*voltha.Device{},
+	}
+
+	for i := 0; i < devicesNum; i++ {
+		devices.Items = append(devices.Items, &voltha.Device{
+			Id:   fmt.Sprintf("%d", i),
+			Root: i%2 == 0,
+		})
+	}
+
+	//Translate them to items
+	items := translateDevices(devices)
+
+	//Check if the number of generated items is correct
+	singleDeviceItemsNum := len(translateDevice(*devices.Items[0]))
+	assert.Equal(t, singleDeviceItemsNum*devicesNum, len(items))
+
+	//Check if the content is right
+	for i := 0; i < devicesNum; i++ {
+		val, ok := getItemWithPath(items, fmt.Sprintf("%s/type", getDevicePath(devices.Items[i].Id)))
+		assert.True(t, ok, fmt.Sprintf("No type item for device %d", i))
+
+		if devices.Items[i].Root {
+			assert.Equal(t, DeviceTypeOlt, val)
+		} else {
+			assert.Equal(t, DeviceTypeOnu, val)
+		}
+	}
+}
diff --git a/internal/sysrepo/plugin.c b/internal/sysrepo/plugin.c
index edbf0e5..f3ff6a3 100644
--- a/internal/sysrepo/plugin.c
+++ b/internal/sysrepo/plugin.c
@@ -14,16 +14,22 @@
 * limitations under the License.
  */
 
+#include <libyang/libyang.h>
 #include <sysrepo.h>
 #include <sysrepo/xpath.h>
 
 //Needed to handle callback functions with a working data type in CGO
 typedef void (*function)(); // https://golang.org/issue/19835
 
-//Exported by sysrepo.go
-void get_data_cb();
+//CGO can't see raw structs
+typedef struct lyd_node lyd_node;
 
-int get_data_cb_wrapper(
+//Exported by sysrepo.go
+sr_error_t get_devices_cb(sr_session_ctx_t *session, lyd_node **parent);
+
+//The wrapper function is needed because CGO cannot express const char*
+//and thus it can't match sysrepo's callback signature
+int get_devices_cb_wrapper(
     sr_session_ctx_t *session,
     uint32_t subscription_id,
     const char *module_name,
@@ -33,7 +39,5 @@
     struct lyd_node **parent,
     void *private_data)
 {
-    get_data_cb();
-
-    return SR_ERR_OK;
+    return get_devices_cb(session, parent);
 }
\ No newline at end of file
diff --git a/internal/sysrepo/sysrepo.go b/internal/sysrepo/sysrepo.go
index b0ebc1f..57de757 100644
--- a/internal/sysrepo/sysrepo.go
+++ b/internal/sysrepo/sysrepo.go
@@ -17,19 +17,16 @@
 package sysrepo
 
 //#cgo CFLAGS: -I/usr/include
-//#cgo LDFLAGS: -lsysrepo -Wl,--allow-multiple-definition
+//#cgo LDFLAGS: -lsysrepo -lyang -Wl,--allow-multiple-definition
 //#include "plugin.c"
 import "C"
 import (
 	"context"
 	"fmt"
+	"unsafe"
 
 	"github.com/opencord/voltha-lib-go/v7/pkg/log"
-)
-
-const (
-	BASE_YANG_MODEL    = "bbf-device-aggregation"
-	DEVICES_YANG_MODEL = "/" + BASE_YANG_MODEL + ":devices"
+	"github.com/opencord/voltha-northbound-bbf-adapter/internal/core"
 )
 
 type SysrepoPlugin struct {
@@ -42,10 +39,48 @@
 	return C.GoString(C.sr_strerror(code))
 }
 
+func freeCString(str *C.char) {
+	if str != nil {
+		C.free(unsafe.Pointer(str))
+		str = nil
+	}
+}
+
+func updateYangItems(ctx context.Context, session *C.sr_session_ctx_t, parent **C.lyd_node, items []core.YangItem) error {
+	conn := C.sr_session_get_connection(session)
+	if conn == nil {
+		return fmt.Errorf("null-connection")
+	}
+
+	//libyang context
+	ly_ctx := C.sr_get_context(conn)
+	if ly_ctx == nil {
+		return fmt.Errorf("null-libyang-context")
+	}
+
+	for _, item := range items {
+		logger.Debugw(ctx, "updating-yang-item", log.Fields{"item": item})
+
+		path := C.CString(item.Path)
+		value := C.CString(item.Value)
+
+		lyErr := C.lyd_new_path(*parent, ly_ctx, path, value, 0, nil)
+		if lyErr != C.LY_SUCCESS {
+			freeCString(path)
+			freeCString(value)
+			return fmt.Errorf("libyang-new-path-failed: %d", lyErr)
+		}
+
+		freeCString(path)
+		freeCString(value)
+	}
+
+	return nil
+}
+
 //createPluginState populates a SysrepoPlugin struct by establishing
 //a connection and a session
 func (p *SysrepoPlugin) createSession(ctx context.Context) error {
-
 	var errCode C.int
 
 	//Populates connection
@@ -70,17 +105,42 @@
 	return nil
 }
 
-//export get_data_cb
-func get_data_cb() {
-	//This function is a callback for the retrieval of data from sysrepo
+//export get_devices_cb
+func get_devices_cb(session *C.sr_session_ctx_t, parent **C.lyd_node) C.sr_error_t {
+	//This function is a callback for the retrieval of devices from sysrepo
 	//The "export" comment instructs CGO to create a C function for it
 
-	//As a placeholder, it just reports that a request to get data
-	//has been received from the netconf server
-
-	//TODO: get actual information
 	ctx := context.Background()
-	logger.Info(ctx, ">>>>>>>RECEIVED REQUEST FROM SYSREPO<<<<<<<")
+	logger.Debug(ctx, "processing-get-data-request")
+
+	if session == nil {
+		logger.Error(ctx, "sysrepo-get-data-null-session")
+		return C.SR_ERR_OPERATION_FAILED
+	}
+
+	if parent == nil {
+		logger.Error(ctx, "sysrepo-get-data-null-parent-node")
+		return C.SR_ERR_OPERATION_FAILED
+	}
+
+	if core.AdapterInstance == nil {
+		logger.Error(ctx, "sysrepo-get-data-nil-translator")
+		return C.SR_ERR_OPERATION_FAILED
+	}
+
+	devices, err := core.AdapterInstance.GetDevices(ctx)
+	if err != nil {
+		logger.Errorw(ctx, "sysrepo-get-data-translator-error", log.Fields{"err": err})
+		return C.SR_ERR_OPERATION_FAILED
+	}
+
+	err = updateYangItems(ctx, session, parent, devices)
+	if err != nil {
+		logger.Errorw(ctx, "sysrepo-get-data-update-error", log.Fields{"err": err})
+		return C.SR_ERR_OPERATION_FAILED
+	}
+
+	return C.SR_ERR_OK
 }
 
 func StartNewPlugin(ctx context.Context) (*SysrepoPlugin, error) {
@@ -98,11 +158,17 @@
 	//Set callbacks for events
 
 	//Subscribe with a callback to the request of data on a certain path
+	module := C.CString(core.DeviceAggregationModel)
+	defer freeCString(module)
+
+	path := C.CString(core.DevicesPath + "/*")
+	defer freeCString(path)
+
 	errCode := C.sr_oper_get_items_subscribe(
 		plugin.session,
-		C.CString(BASE_YANG_MODEL),
-		C.CString(DEVICES_YANG_MODEL+"/*"),
-		C.function(C.get_data_cb_wrapper),
+		module,
+		path,
+		C.function(C.get_devices_cb_wrapper),
 		C.NULL,
 		C.SR_SUBSCR_CTX_REUSE,
 		&plugin.subscription,