VOL-2017 voltha-lib moved from voltha-go;
release version 2.2.1

Based on voltha-go commit 5259f8e52b3e3f5c7ad422a4b0e506e1d07f6b36

Change-Id: I8bbecdf456e420714a4016120eafc0d237c80565
diff --git a/pkg/db/model/node.go b/pkg/db/model/node.go
new file mode 100644
index 0000000..4d8c467
--- /dev/null
+++ b/pkg/db/model/node.go
@@ -0,0 +1,1161 @@
+/*
+ * Copyright 2018-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 model
+
+// TODO: proper error handling
+// TODO: proper logging
+
+import (
+	"context"
+	"fmt"
+	"github.com/golang/protobuf/proto"
+	"github.com/opencord/voltha-lib-go/pkg/common/log"
+	"reflect"
+	"strings"
+	"sync"
+	"time"
+)
+
+// When a branch has no transaction id, everything gets stored in NONE
+const (
+	NONE string = "none"
+)
+
+// Node interface is an abstraction of the node data structure
+type Node interface {
+	MakeLatest(branch *Branch, revision Revision, changeAnnouncement []ChangeTuple)
+
+	// CRUD functions
+	Add(ctx context.Context, path string, data interface{}, txid string, makeBranch MakeBranchFunction) Revision
+	Get(ctx context.Context, path string, hash string, depth int, deep bool, txid string) interface{}
+	List(ctx context.Context, path string, hash string, depth int, deep bool, txid string) interface{}
+	Update(ctx context.Context, path string, data interface{}, strict bool, txid string, makeBranch MakeBranchFunction) Revision
+	Remove(ctx context.Context, path string, txid string, makeBranch MakeBranchFunction) Revision
+	CreateProxy(ctx context.Context, path string, exclusive bool) *Proxy
+
+	GetProxy() *Proxy
+
+	MakeBranch(txid string) *Branch
+	DeleteBranch(txid string)
+	MergeBranch(txid string, dryRun bool) (Revision, error)
+
+	MakeTxBranch() string
+	DeleteTxBranch(txid string)
+	FoldTxBranch(txid string)
+}
+
+type node struct {
+	mutex     sync.RWMutex
+	Root      *root
+	Type      interface{}
+	Branches  map[string]*Branch
+	Tags      map[string]Revision
+	Proxy     *Proxy
+	EventBus  *EventBus
+	AutoPrune bool
+}
+
+// ChangeTuple holds details of modifications made to a revision
+type ChangeTuple struct {
+	Type         CallbackType
+	PreviousData interface{}
+	LatestData   interface{}
+}
+
+// NewNode creates a new instance of the node data structure
+func NewNode(root *root, initialData interface{}, autoPrune bool, txid string) *node {
+	n := &node{}
+
+	n.Root = root
+	n.Branches = make(map[string]*Branch)
+	n.Tags = make(map[string]Revision)
+	n.Proxy = nil
+	n.EventBus = nil
+	n.AutoPrune = autoPrune
+
+	if IsProtoMessage(initialData) {
+		n.Type = reflect.ValueOf(initialData).Interface()
+		dataCopy := proto.Clone(initialData.(proto.Message))
+		n.initialize(dataCopy, txid)
+	} else if reflect.ValueOf(initialData).IsValid() {
+		// FIXME: this block does not reflect the original implementation
+		// it should be checking if the provided initial_data is already a type!??!
+		// it should be checked before IsProtoMessage
+		n.Type = reflect.ValueOf(initialData).Interface()
+	} else {
+		// not implemented error
+		log.Errorf("cannot process initial data - %+v", initialData)
+	}
+
+	return n
+}
+
+// MakeNode creates a new node in the tree
+func (n *node) MakeNode(data interface{}, txid string) *node {
+	return NewNode(n.Root, data, true, txid)
+}
+
+// MakeRevision create a new revision of the node in the tree
+func (n *node) MakeRevision(branch *Branch, data interface{}, children map[string][]Revision) Revision {
+	return n.GetRoot().MakeRevision(branch, data, children)
+}
+
+// makeLatest will mark the revision of a node as being the latest
+func (n *node) makeLatest(branch *Branch, revision Revision, changeAnnouncement []ChangeTuple) {
+	// Keep a reference to the current revision
+	var previous string
+	if branch.GetLatest() != nil {
+		previous = branch.GetLatest().GetHash()
+	}
+
+	branch.AddRevision(revision)
+
+	// If anything is new, then set the revision as the latest
+	if branch.GetLatest() == nil || revision.GetHash() != branch.GetLatest().GetHash() {
+		if revision.GetName() != "" {
+			log.Debugw("saving-latest-data", log.Fields{"hash": revision.GetHash(), "data": revision.GetData()})
+			// Tag a timestamp to that revision
+			revision.SetLastUpdate()
+			GetRevCache().Set(revision.GetName(), revision)
+		}
+		branch.SetLatest(revision)
+	}
+
+	// Delete the previous revision if anything has changed
+	if previous != "" && previous != branch.GetLatest().GetHash() {
+		branch.DeleteRevision(previous)
+	}
+
+	if changeAnnouncement != nil && branch.Txid == "" {
+		if n.Proxy != nil {
+			for _, change := range changeAnnouncement {
+				log.Debugw("adding-callback",
+					log.Fields{
+						"callbacks":    n.GetProxy().getCallbacks(change.Type),
+						"type":         change.Type,
+						"previousData": change.PreviousData,
+						"latestData":   change.LatestData,
+					})
+				n.Root.AddCallback(
+					n.GetProxy().InvokeCallbacks,
+					change.Type,
+					true,
+					change.PreviousData,
+					change.LatestData)
+			}
+		}
+	}
+}
+
+// Latest returns the latest revision of node with or without the transaction id
+func (n *node) Latest(txid ...string) Revision {
+	var branch *Branch
+
+	if len(txid) > 0 && txid[0] != "" {
+		if branch = n.GetBranch(txid[0]); branch != nil {
+			return branch.GetLatest()
+		}
+	} else if branch = n.GetBranch(NONE); branch != nil {
+		return branch.GetLatest()
+	}
+	return nil
+}
+
+// initialize prepares the content of a node along with its possible ramifications
+func (n *node) initialize(data interface{}, txid string) {
+	children := make(map[string][]Revision)
+	for fieldName, field := range ChildrenFields(n.Type) {
+		_, fieldValue := GetAttributeValue(data, fieldName, 0)
+
+		if fieldValue.IsValid() {
+			if field.IsContainer {
+				if field.Key != "" {
+					for i := 0; i < fieldValue.Len(); i++ {
+						v := fieldValue.Index(i)
+
+						if rev := n.MakeNode(v.Interface(), txid).Latest(txid); rev != nil {
+							children[fieldName] = append(children[fieldName], rev)
+						}
+
+						// TODO: The following logic was ported from v1.0.  Need to verify if it is required
+						//var keysSeen []string
+						//_, key := GetAttributeValue(v.Interface(), field.Key, 0)
+						//for _, k := range keysSeen {
+						//	if k == key.String() {
+						//		//log.Errorf("duplicate key - %s", k)
+						//	}
+						//}
+						//keysSeen = append(keysSeen, key.String())
+					}
+
+				} else {
+					for i := 0; i < fieldValue.Len(); i++ {
+						v := fieldValue.Index(i)
+						if newNodeRev := n.MakeNode(v.Interface(), txid).Latest(); newNodeRev != nil {
+							children[fieldName] = append(children[fieldName], newNodeRev)
+						}
+					}
+				}
+			} else {
+				if newNodeRev := n.MakeNode(fieldValue.Interface(), txid).Latest(); newNodeRev != nil {
+					children[fieldName] = append(children[fieldName], newNodeRev)
+				}
+			}
+		} else {
+			log.Errorf("field is invalid - %+v", fieldValue)
+		}
+	}
+
+	branch := NewBranch(n, "", nil, n.AutoPrune)
+	rev := n.MakeRevision(branch, data, children)
+	n.makeLatest(branch, rev, nil)
+
+	if txid == "" {
+		n.SetBranch(NONE, branch)
+	} else {
+		n.SetBranch(txid, branch)
+	}
+}
+
+// findRevByKey retrieves a specific revision from a node tree
+func (n *node) findRevByKey(revs []Revision, keyName string, value interface{}) (int, Revision) {
+	for i, rev := range revs {
+		dataValue := reflect.ValueOf(rev.GetData())
+		dataStruct := GetAttributeStructure(rev.GetData(), keyName, 0)
+
+		fieldValue := dataValue.Elem().FieldByName(dataStruct.Name)
+
+		a := fmt.Sprintf("%s", fieldValue.Interface())
+		b := fmt.Sprintf("%s", value)
+		if a == b {
+			return i, revs[i]
+		}
+	}
+
+	return -1, nil
+}
+
+// Get retrieves the data from a node tree that resides at the specified path
+func (n *node) List(ctx context.Context, path string, hash string, depth int, deep bool, txid string) interface{} {
+	n.mutex.Lock()
+	defer n.mutex.Unlock()
+
+	log.Debugw("node-list-request", log.Fields{"path": path, "hash": hash, "depth": depth, "deep": deep, "txid": txid})
+	if deep {
+		depth = -1
+	}
+
+	for strings.HasPrefix(path, "/") {
+		path = path[1:]
+	}
+
+	var branch *Branch
+	var rev Revision
+
+	if branch = n.GetBranch(txid); txid == "" || branch == nil {
+		branch = n.GetBranch(NONE)
+	}
+
+	if hash != "" {
+		rev = branch.GetRevision(hash)
+	} else {
+		rev = branch.GetLatest()
+	}
+
+	var result interface{}
+	var prList []interface{}
+	if pr := rev.LoadFromPersistence(ctx, path, txid, nil); pr != nil {
+		for _, revEntry := range pr {
+			prList = append(prList, revEntry.GetData())
+		}
+		result = prList
+	}
+
+	return result
+}
+
+// Get retrieves the data from a node tree that resides at the specified path
+func (n *node) Get(ctx context.Context, path string, hash string, depth int, reconcile bool, txid string) interface{} {
+	n.mutex.Lock()
+	defer n.mutex.Unlock()
+
+	log.Debugw("node-get-request", log.Fields{"path": path, "hash": hash, "depth": depth, "reconcile": reconcile, "txid": txid})
+
+	for strings.HasPrefix(path, "/") {
+		path = path[1:]
+	}
+
+	var branch *Branch
+	var rev Revision
+
+	if branch = n.GetBranch(txid); txid == "" || branch == nil {
+		branch = n.GetBranch(NONE)
+	}
+
+	if hash != "" {
+		rev = branch.GetRevision(hash)
+	} else {
+		rev = branch.GetLatest()
+	}
+
+	var result interface{}
+
+	// If there is no request to reconcile, try to get it from memory
+	if !reconcile {
+		// Try to find an entry matching the path value from one of these sources
+		// 1.  Start with the cache which stores revisions by watch names
+		// 2.  Then look in the revision tree, especially if it's a sub-path such as /devices/1234/flows
+		// 3.  Move on to the KV store if that path cannot be found or if the entry has expired
+		if entry, exists := GetRevCache().Get(path); exists && entry.(Revision) != nil {
+			entryAge := time.Now().Sub(entry.(Revision).GetLastUpdate()).Nanoseconds() / int64(time.Millisecond)
+			if entryAge < DataRefreshPeriod {
+				log.Debugw("using-cache-entry", log.Fields{
+					"path": path,
+					"hash": hash,
+					"age":  entryAge,
+				})
+				return proto.Clone(entry.(Revision).GetData().(proto.Message))
+			} else {
+				log.Debugw("cache-entry-expired", log.Fields{"path": path, "hash": hash, "age": entryAge})
+			}
+		} else if result = n.getPath(ctx, rev.GetBranch().GetLatest(), path, depth); result != nil && reflect.ValueOf(result).IsValid() && !reflect.ValueOf(result).IsNil() {
+			log.Debugw("using-rev-tree-entry", log.Fields{"path": path, "hash": hash, "depth": depth, "reconcile": reconcile, "txid": txid})
+			return result
+		} else {
+			log.Debugw("not-using-cache-entry", log.Fields{
+				"path": path,
+				"hash": hash, "depth": depth,
+				"reconcile": reconcile,
+				"txid":      txid,
+			})
+		}
+	} else {
+		log.Debugw("reconcile-requested", log.Fields{
+			"path":      path,
+			"hash":      hash,
+			"reconcile": reconcile,
+		})
+	}
+
+	// If we got to this point, we are either trying to reconcile with the db
+	// or we simply failed at getting information from memory
+	if n.Root.KvStore != nil {
+		if pr := rev.LoadFromPersistence(ctx, path, txid, nil); pr != nil && len(pr) > 0 {
+			// Did we receive a single or multiple revisions?
+			if len(pr) > 1 {
+				var revs []interface{}
+				for _, revEntry := range pr {
+					revs = append(revs, revEntry.GetData())
+				}
+				result = revs
+			} else {
+				result = pr[0].GetData()
+			}
+		}
+	}
+
+	return result
+}
+
+//getPath traverses the specified path and retrieves the data associated to it
+func (n *node) getPath(ctx context.Context, rev Revision, path string, depth int) interface{} {
+	if path == "" {
+		return n.getData(rev, depth)
+	}
+
+	partition := strings.SplitN(path, "/", 2)
+	name := partition[0]
+
+	if len(partition) < 2 {
+		path = ""
+	} else {
+		path = partition[1]
+	}
+
+	names := ChildrenFields(n.Type)
+	field := names[name]
+
+	if field != nil && field.IsContainer {
+		children := make([]Revision, len(rev.GetChildren(name)))
+		copy(children, rev.GetChildren(name))
+
+		if field.Key != "" {
+			if path != "" {
+				partition = strings.SplitN(path, "/", 2)
+				key := partition[0]
+				path = ""
+				keyValue := field.KeyFromStr(key)
+				if _, childRev := n.findRevByKey(children, field.Key, keyValue); childRev == nil {
+					return nil
+				} else {
+					childNode := childRev.GetNode()
+					return childNode.getPath(ctx, childRev, path, depth)
+				}
+			} else {
+				var response []interface{}
+				for _, childRev := range children {
+					childNode := childRev.GetNode()
+					value := childNode.getData(childRev, depth)
+					response = append(response, value)
+				}
+				return response
+			}
+		} else {
+			var response []interface{}
+			if path != "" {
+				// TODO: raise error
+				return response
+			}
+			for _, childRev := range children {
+				childNode := childRev.GetNode()
+				value := childNode.getData(childRev, depth)
+				response = append(response, value)
+			}
+			return response
+		}
+	} else if children := rev.GetChildren(name); children != nil && len(children) > 0 {
+		childRev := children[0]
+		childNode := childRev.GetNode()
+		return childNode.getPath(ctx, childRev, path, depth)
+	}
+
+	return nil
+}
+
+// getData retrieves the data from a node revision
+func (n *node) getData(rev Revision, depth int) interface{} {
+	msg := rev.GetBranch().GetLatest().Get(depth)
+	var modifiedMsg interface{}
+
+	if n.GetProxy() != nil {
+		log.Debugw("invoking-get-callbacks", log.Fields{"data": msg})
+		if modifiedMsg = n.GetProxy().InvokeCallbacks(GET, false, msg); modifiedMsg != nil {
+			msg = modifiedMsg
+		}
+
+	}
+
+	return msg
+}
+
+// Update changes the content of a node at the specified path with the provided data
+func (n *node) Update(ctx context.Context, path string, data interface{}, strict bool, txid string, makeBranch MakeBranchFunction) Revision {
+	n.mutex.Lock()
+	defer n.mutex.Unlock()
+
+	log.Debugw("node-update-request", log.Fields{"path": path, "strict": strict, "txid": txid})
+
+	for strings.HasPrefix(path, "/") {
+		path = path[1:]
+	}
+
+	var branch *Branch
+	if txid == "" {
+		branch = n.GetBranch(NONE)
+	} else if branch = n.GetBranch(txid); branch == nil {
+		branch = makeBranch(n)
+	}
+
+	if branch.GetLatest() != nil {
+		log.Debugf("Branch data : %+v, Passed data: %+v", branch.GetLatest().GetData(), data)
+	}
+	if path == "" {
+		return n.doUpdate(ctx, branch, data, strict)
+	}
+
+	rev := branch.GetLatest()
+
+	partition := strings.SplitN(path, "/", 2)
+	name := partition[0]
+
+	if len(partition) < 2 {
+		path = ""
+	} else {
+		path = partition[1]
+	}
+
+	field := ChildrenFields(n.Type)[name]
+	var children []Revision
+
+	if field == nil {
+		return n.doUpdate(ctx, branch, data, strict)
+	}
+
+	if field.IsContainer {
+		if path == "" {
+			log.Errorf("cannot update a list")
+		} else if field.Key != "" {
+			partition := strings.SplitN(path, "/", 2)
+			key := partition[0]
+			if len(partition) < 2 {
+				path = ""
+			} else {
+				path = partition[1]
+			}
+			keyValue := field.KeyFromStr(key)
+
+			children = make([]Revision, len(rev.GetChildren(name)))
+			copy(children, rev.GetChildren(name))
+
+			idx, childRev := n.findRevByKey(children, field.Key, keyValue)
+
+			if childRev == nil {
+				log.Debugw("child-revision-is-nil", log.Fields{"key": keyValue})
+				return branch.GetLatest()
+			}
+
+			childNode := childRev.GetNode()
+
+			// Save proxy in child node to ensure callbacks are called later on
+			// only assign in cases of non sub-folder proxies, i.e. "/"
+			if childNode.Proxy == nil && n.Proxy != nil && n.GetProxy().getFullPath() == "" {
+				childNode.Proxy = n.Proxy
+			}
+
+			newChildRev := childNode.Update(ctx, path, data, strict, txid, makeBranch)
+
+			if newChildRev.GetHash() == childRev.GetHash() {
+				if newChildRev != childRev {
+					log.Debug("clear-hash - %s %+v", newChildRev.GetHash(), newChildRev)
+					newChildRev.ClearHash()
+				}
+				log.Debugw("child-revisions-have-matching-hash", log.Fields{"hash": childRev.GetHash(), "key": keyValue})
+				return branch.GetLatest()
+			}
+
+			_, newKey := GetAttributeValue(newChildRev.GetData(), field.Key, 0)
+
+			_newKeyType := fmt.Sprintf("%s", newKey)
+			_keyValueType := fmt.Sprintf("%s", keyValue)
+
+			if _newKeyType != _keyValueType {
+				log.Errorf("cannot change key field")
+			}
+
+			// Prefix the hash value with the data type (e.g. devices, logical_devices, adapters)
+			newChildRev.SetName(name + "/" + _keyValueType)
+
+			branch.LatestLock.Lock()
+			defer branch.LatestLock.Unlock()
+
+			if idx >= 0 {
+				children[idx] = newChildRev
+			} else {
+				children = append(children, newChildRev)
+			}
+
+			updatedRev := rev.UpdateChildren(ctx, name, children, branch)
+
+			n.makeLatest(branch, updatedRev, nil)
+			updatedRev.ChildDrop(name, childRev.GetHash())
+
+			return newChildRev
+
+		} else {
+			log.Errorf("cannot index into container with no keys")
+		}
+	} else {
+		childRev := rev.GetChildren(name)[0]
+		childNode := childRev.GetNode()
+		newChildRev := childNode.Update(ctx, path, data, strict, txid, makeBranch)
+
+		branch.LatestLock.Lock()
+		defer branch.LatestLock.Unlock()
+
+		updatedRev := rev.UpdateChildren(ctx, name, []Revision{newChildRev}, branch)
+		n.makeLatest(branch, updatedRev, nil)
+
+		updatedRev.ChildDrop(name, childRev.GetHash())
+
+		return newChildRev
+	}
+
+	return nil
+}
+
+func (n *node) doUpdate(ctx context.Context, branch *Branch, data interface{}, strict bool) Revision {
+	log.Debugw("comparing-types", log.Fields{"expected": reflect.ValueOf(n.Type).Type(), "actual": reflect.TypeOf(data)})
+
+	if reflect.TypeOf(data) != reflect.ValueOf(n.Type).Type() {
+		// TODO raise error
+		log.Errorw("types-do-not-match: %+v", log.Fields{"actual": reflect.TypeOf(data), "expected": n.Type})
+		return nil
+	}
+
+	// TODO: validate that this actually works
+	//if n.hasChildren(data) {
+	//	return nil
+	//}
+
+	if n.GetProxy() != nil {
+		log.Debug("invoking proxy PRE_UPDATE Callbacks")
+		n.GetProxy().InvokeCallbacks(PRE_UPDATE, false, branch.GetLatest(), data)
+	}
+
+	if branch.GetLatest().GetData().(proto.Message).String() != data.(proto.Message).String() {
+		if strict {
+			// TODO: checkAccessViolations(data, Branch.GetLatest.data)
+			log.Debugf("checking access violations")
+		}
+
+		rev := branch.GetLatest().UpdateData(ctx, data, branch)
+		changes := []ChangeTuple{{POST_UPDATE, branch.GetLatest().GetData(), rev.GetData()}}
+		n.makeLatest(branch, rev, changes)
+
+		return rev
+	}
+	return branch.GetLatest()
+}
+
+// Add inserts a new node at the specified path with the provided data
+func (n *node) Add(ctx context.Context, path string, data interface{}, txid string, makeBranch MakeBranchFunction) Revision {
+	n.mutex.Lock()
+	defer n.mutex.Unlock()
+
+	log.Debugw("node-add-request", log.Fields{"path": path, "txid": txid})
+
+	for strings.HasPrefix(path, "/") {
+		path = path[1:]
+	}
+	if path == "" {
+		// TODO raise error
+		log.Errorf("cannot add for non-container mode")
+		return nil
+	}
+
+	var branch *Branch
+	if txid == "" {
+		branch = n.GetBranch(NONE)
+	} else if branch = n.GetBranch(txid); branch == nil {
+		branch = makeBranch(n)
+	}
+
+	rev := branch.GetLatest()
+
+	partition := strings.SplitN(path, "/", 2)
+	name := partition[0]
+
+	if len(partition) < 2 {
+		path = ""
+	} else {
+		path = partition[1]
+	}
+
+	field := ChildrenFields(n.Type)[name]
+
+	var children []Revision
+
+	if field.IsContainer {
+		if path == "" {
+			if field.Key != "" {
+				if n.GetProxy() != nil {
+					log.Debug("invoking proxy PRE_ADD Callbacks")
+					n.GetProxy().InvokeCallbacks(PRE_ADD, false, data)
+				}
+
+				children = make([]Revision, len(rev.GetChildren(name)))
+				copy(children, rev.GetChildren(name))
+
+				_, key := GetAttributeValue(data, field.Key, 0)
+
+				if _, exists := n.findRevByKey(children, field.Key, key.String()); exists != nil {
+					// TODO raise error
+					log.Warnw("duplicate-key-found", log.Fields{"key": key.String()})
+					return exists
+				}
+				childRev := n.MakeNode(data, "").Latest()
+
+				// Prefix the hash with the data type (e.g. devices, logical_devices, adapters)
+				childRev.SetName(name + "/" + key.String())
+
+				branch.LatestLock.Lock()
+				defer branch.LatestLock.Unlock()
+
+				children = append(children, childRev)
+
+				updatedRev := rev.UpdateChildren(ctx, name, children, branch)
+				changes := []ChangeTuple{{POST_ADD, nil, childRev.GetData()}}
+				childRev.SetupWatch(childRev.GetName())
+
+				n.makeLatest(branch, updatedRev, changes)
+
+				return childRev
+			}
+			log.Errorf("cannot add to non-keyed container")
+
+		} else if field.Key != "" {
+			partition := strings.SplitN(path, "/", 2)
+			key := partition[0]
+			if len(partition) < 2 {
+				path = ""
+			} else {
+				path = partition[1]
+			}
+			keyValue := field.KeyFromStr(key)
+
+			children = make([]Revision, len(rev.GetChildren(name)))
+			copy(children, rev.GetChildren(name))
+
+			idx, childRev := n.findRevByKey(children, field.Key, keyValue)
+
+			if childRev == nil {
+				return branch.GetLatest()
+			}
+
+			childNode := childRev.GetNode()
+			newChildRev := childNode.Add(ctx, path, data, txid, makeBranch)
+
+			// Prefix the hash with the data type (e.g. devices, logical_devices, adapters)
+			newChildRev.SetName(name + "/" + keyValue.(string))
+
+			branch.LatestLock.Lock()
+			defer branch.LatestLock.Unlock()
+
+			if idx >= 0 {
+				children[idx] = newChildRev
+			} else {
+				children = append(children, newChildRev)
+			}
+
+			updatedRev := rev.UpdateChildren(ctx, name, children, branch)
+			n.makeLatest(branch, updatedRev, nil)
+
+			updatedRev.ChildDrop(name, childRev.GetHash())
+
+			return newChildRev
+		} else {
+			log.Errorf("cannot add to non-keyed container")
+		}
+	} else {
+		log.Errorf("cannot add to non-container field")
+	}
+
+	return nil
+}
+
+// Remove eliminates a node at the specified path
+func (n *node) Remove(ctx context.Context, path string, txid string, makeBranch MakeBranchFunction) Revision {
+	n.mutex.Lock()
+	defer n.mutex.Unlock()
+
+	log.Debugw("node-remove-request", log.Fields{"path": path, "txid": txid, "makeBranch": makeBranch})
+
+	for strings.HasPrefix(path, "/") {
+		path = path[1:]
+	}
+	if path == "" {
+		// TODO raise error
+		log.Errorf("cannot remove for non-container mode")
+	}
+	var branch *Branch
+	if txid == "" {
+		branch = n.GetBranch(NONE)
+	} else if branch = n.GetBranch(txid); branch == nil {
+		branch = makeBranch(n)
+	}
+
+	rev := branch.GetLatest()
+
+	partition := strings.SplitN(path, "/", 2)
+	name := partition[0]
+	if len(partition) < 2 {
+		path = ""
+	} else {
+		path = partition[1]
+	}
+
+	field := ChildrenFields(n.Type)[name]
+	var children []Revision
+	postAnnouncement := []ChangeTuple{}
+
+	if field.IsContainer {
+		if path == "" {
+			log.Errorw("cannot-remove-without-key", log.Fields{"name": name, "key": path})
+		} else if field.Key != "" {
+			partition := strings.SplitN(path, "/", 2)
+			key := partition[0]
+			if len(partition) < 2 {
+				path = ""
+			} else {
+				path = partition[1]
+			}
+
+			keyValue := field.KeyFromStr(key)
+			children = make([]Revision, len(rev.GetChildren(name)))
+			copy(children, rev.GetChildren(name))
+
+			if path != "" {
+				if idx, childRev := n.findRevByKey(children, field.Key, keyValue); childRev != nil {
+					childNode := childRev.GetNode()
+					if childNode.Proxy == nil {
+						childNode.Proxy = n.Proxy
+					}
+					newChildRev := childNode.Remove(ctx, path, txid, makeBranch)
+
+					branch.LatestLock.Lock()
+					defer branch.LatestLock.Unlock()
+
+					if idx >= 0 {
+						children[idx] = newChildRev
+					} else {
+						children = append(children, newChildRev)
+					}
+
+					rev.SetChildren(name, children)
+					branch.GetLatest().Drop(txid, false)
+					n.makeLatest(branch, rev, nil)
+				}
+				return branch.GetLatest()
+			}
+
+			if idx, childRev := n.findRevByKey(children, field.Key, keyValue); childRev != nil && idx >= 0 {
+				if n.GetProxy() != nil {
+					data := childRev.GetData()
+					n.GetProxy().InvokeCallbacks(PRE_REMOVE, false, data)
+					postAnnouncement = append(postAnnouncement, ChangeTuple{POST_REMOVE, data, nil})
+				} else {
+					postAnnouncement = append(postAnnouncement, ChangeTuple{POST_REMOVE, childRev.GetData(), nil})
+				}
+
+				childRev.StorageDrop(txid, true)
+				GetRevCache().Delete(childRev.GetName())
+
+				branch.LatestLock.Lock()
+				defer branch.LatestLock.Unlock()
+
+				children = append(children[:idx], children[idx+1:]...)
+				rev.SetChildren(name, children)
+
+				branch.GetLatest().Drop(txid, false)
+				n.makeLatest(branch, rev, postAnnouncement)
+
+				return rev
+			} else {
+				log.Errorw("failed-to-find-revision", log.Fields{"name": name, "key": keyValue.(string)})
+			}
+		}
+		log.Errorw("cannot-add-to-non-keyed-container", log.Fields{"name": name, "path": path, "fieldKey": field.Key})
+
+	} else {
+		log.Errorw("cannot-add-to-non-container-field", log.Fields{"name": name, "path": path})
+	}
+
+	return nil
+}
+
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Branching ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+// MakeBranchFunction is a type for function references intented to create a branch
+type MakeBranchFunction func(*node) *Branch
+
+// MakeBranch creates a new branch for the provided transaction id
+func (n *node) MakeBranch(txid string) *Branch {
+	branchPoint := n.GetBranch(NONE).GetLatest()
+	branch := NewBranch(n, txid, branchPoint, true)
+	n.SetBranch(txid, branch)
+	return branch
+}
+
+// DeleteBranch removes a branch with the specified id
+func (n *node) DeleteBranch(txid string) {
+	delete(n.Branches, txid)
+}
+
+func (n *node) mergeChild(txid string, dryRun bool) func(Revision) Revision {
+	f := func(rev Revision) Revision {
+		childBranch := rev.GetBranch()
+
+		if childBranch.Txid == txid {
+			rev, _ = childBranch.Node.MergeBranch(txid, dryRun)
+		}
+
+		return rev
+	}
+	return f
+}
+
+// MergeBranch will integrate the contents of a transaction branch within the latest branch of a given node
+func (n *node) MergeBranch(txid string, dryRun bool) (Revision, error) {
+	srcBranch := n.GetBranch(txid)
+	dstBranch := n.GetBranch(NONE)
+
+	forkRev := srcBranch.Origin
+	srcRev := srcBranch.GetLatest()
+	dstRev := dstBranch.GetLatest()
+
+	rev, changes := Merge3Way(forkRev, srcRev, dstRev, n.mergeChild(txid, dryRun), dryRun)
+
+	if !dryRun {
+		if rev != nil {
+			rev.SetName(dstRev.GetName())
+			n.makeLatest(dstBranch, rev, changes)
+		}
+		n.DeleteBranch(txid)
+	}
+
+	// TODO: return proper error when one occurs
+	return rev, nil
+}
+
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Diff utility ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+//func (n *node) diff(hash1, hash2, txid string) {
+//	branch := n.Branches[txid]
+//	rev1 := branch.GetHash(hash1)
+//	rev2 := branch.GetHash(hash2)
+//
+//	if rev1.GetHash() == rev2.GetHash() {
+//		// empty patch
+//	} else {
+//		// translate data to json and generate patch
+//		patch, err := jsonpatch.MakePatch(rev1.GetData(), rev2.GetData())
+//		patch.
+//	}
+//}
+
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Tag utility ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+// TODO: is tag mgmt used in the python implementation? Need to validate
+
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Internals ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+func (n *node) hasChildren(data interface{}) bool {
+	for fieldName, field := range ChildrenFields(n.Type) {
+		_, fieldValue := GetAttributeValue(data, fieldName, 0)
+
+		if (field.IsContainer && fieldValue.Len() > 0) || !fieldValue.IsNil() {
+			log.Error("cannot update external children")
+			return true
+		}
+	}
+
+	return false
+}
+
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ node Proxy ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+// CreateProxy returns a reference to a sub-tree of the data model
+func (n *node) CreateProxy(ctx context.Context, path string, exclusive bool) *Proxy {
+	return n.createProxy(ctx, path, path, n, exclusive)
+}
+
+func (n *node) createProxy(ctx context.Context, path string, fullPath string, parentNode *node, exclusive bool) *Proxy {
+	log.Debugw("node-create-proxy", log.Fields{
+		"node-type":        reflect.ValueOf(n.Type).Type(),
+		"parent-node-type": reflect.ValueOf(parentNode.Type).Type(),
+		"path":             path,
+		"fullPath":         fullPath,
+	})
+
+	for strings.HasPrefix(path, "/") {
+		path = path[1:]
+	}
+	if path == "" {
+		return n.makeProxy(path, fullPath, parentNode, exclusive)
+	}
+
+	rev := n.GetBranch(NONE).GetLatest()
+	partition := strings.SplitN(path, "/", 2)
+	name := partition[0]
+	var nodeType interface{}
+	if len(partition) < 2 {
+		path = ""
+		nodeType = n.Type
+	} else {
+		path = partition[1]
+		nodeType = parentNode.Type
+	}
+
+	field := ChildrenFields(nodeType)[name]
+
+	if field != nil {
+		if field.IsContainer {
+			log.Debugw("container-field", log.Fields{
+				"node-type":        reflect.ValueOf(n.Type).Type(),
+				"parent-node-type": reflect.ValueOf(parentNode.Type).Type(),
+				"path":             path,
+				"name":             name,
+			})
+			if path == "" {
+				log.Debugw("folder-proxy", log.Fields{
+					"node-type":        reflect.ValueOf(n.Type).Type(),
+					"parent-node-type": reflect.ValueOf(parentNode.Type).Type(),
+					"fullPath":         fullPath,
+					"name":             name,
+				})
+				newNode := n.MakeNode(reflect.New(field.ClassType.Elem()).Interface(), "")
+				return newNode.makeProxy(path, fullPath, parentNode, exclusive)
+			} else if field.Key != "" {
+				log.Debugw("key-proxy", log.Fields{
+					"node-type":        reflect.ValueOf(n.Type).Type(),
+					"parent-node-type": reflect.ValueOf(parentNode.Type).Type(),
+					"fullPath":         fullPath,
+					"name":             name,
+				})
+				partition := strings.SplitN(path, "/", 2)
+				key := partition[0]
+				if len(partition) < 2 {
+					path = ""
+				} else {
+					path = partition[1]
+				}
+				keyValue := field.KeyFromStr(key)
+				var children []Revision
+				children = make([]Revision, len(rev.GetChildren(name)))
+				copy(children, rev.GetChildren(name))
+
+				var childRev Revision
+				if _, childRev = n.findRevByKey(children, field.Key, keyValue); childRev != nil {
+					log.Debugw("found-revision-matching-key-in-memory", log.Fields{
+						"node-type":        reflect.ValueOf(n.Type).Type(),
+						"parent-node-type": reflect.ValueOf(parentNode.Type).Type(),
+						"fullPath":         fullPath,
+						"name":             name,
+					})
+				} else if revs := n.GetBranch(NONE).GetLatest().LoadFromPersistence(ctx, fullPath, "", nil); revs != nil && len(revs) > 0 {
+					log.Debugw("found-revision-matching-key-in-db", log.Fields{
+						"node-type":        reflect.ValueOf(n.Type).Type(),
+						"parent-node-type": reflect.ValueOf(parentNode.Type).Type(),
+						"fullPath":         fullPath,
+						"name":             name,
+					})
+					childRev = revs[0]
+				} else {
+					log.Debugw("no-revision-matching-key", log.Fields{
+						"node-type":        reflect.ValueOf(n.Type).Type(),
+						"parent-node-type": reflect.ValueOf(parentNode.Type).Type(),
+						"fullPath":         fullPath,
+						"name":             name,
+					})
+				}
+				if childRev != nil {
+					childNode := childRev.GetNode()
+					return childNode.createProxy(ctx, path, fullPath, n, exclusive)
+				}
+			} else {
+				log.Errorw("cannot-access-index-of-empty-container", log.Fields{
+					"node-type":        reflect.ValueOf(n.Type).Type(),
+					"parent-node-type": reflect.ValueOf(parentNode.Type).Type(),
+					"path":             path,
+					"name":             name,
+				})
+			}
+		} else {
+			log.Debugw("non-container-field", log.Fields{
+				"node-type":        reflect.ValueOf(n.Type).Type(),
+				"parent-node-type": reflect.ValueOf(parentNode.Type).Type(),
+				"path":             path,
+				"name":             name,
+			})
+			childRev := rev.GetChildren(name)[0]
+			childNode := childRev.GetNode()
+			return childNode.createProxy(ctx, path, fullPath, n, exclusive)
+		}
+	} else {
+		log.Debugw("field-object-is-nil", log.Fields{
+			"node-type":        reflect.ValueOf(n.Type).Type(),
+			"parent-node-type": reflect.ValueOf(parentNode.Type).Type(),
+			"fullPath":         fullPath,
+			"name":             name,
+		})
+	}
+
+	log.Warnw("cannot-create-proxy", log.Fields{
+		"node-type":        reflect.ValueOf(n.Type).Type(),
+		"parent-node-type": reflect.ValueOf(parentNode.Type).Type(),
+		"path":             path,
+		"fullPath":         fullPath,
+		"latest-rev":       rev.GetHash(),
+	})
+	return nil
+}
+
+func (n *node) makeProxy(path string, fullPath string, parentNode *node, exclusive bool) *Proxy {
+	log.Debugw("node-make-proxy", log.Fields{
+		"node-type":        reflect.ValueOf(n.Type).Type(),
+		"parent-node-type": reflect.ValueOf(parentNode.Type).Type(),
+		"path":             path,
+		"fullPath":         fullPath,
+	})
+
+	r := &root{
+		node:                  n,
+		Callbacks:             n.Root.GetCallbacks(),
+		NotificationCallbacks: n.Root.GetNotificationCallbacks(),
+		DirtyNodes:            n.Root.DirtyNodes,
+		KvStore:               n.Root.KvStore,
+		Loading:               n.Root.Loading,
+		RevisionClass:         n.Root.RevisionClass,
+	}
+
+	if n.Proxy == nil {
+		log.Debugw("constructing-new-proxy", log.Fields{
+			"node-type":        reflect.ValueOf(n.Type).Type(),
+			"parent-node-type": reflect.ValueOf(parentNode.Type).Type(),
+			"path":             path,
+			"fullPath":         fullPath,
+		})
+		n.Proxy = NewProxy(r, n, parentNode, path, fullPath, exclusive)
+	} else {
+		log.Debugw("node-has-existing-proxy", log.Fields{
+			"node-type":        reflect.ValueOf(n.GetProxy().Node.Type).Type(),
+			"parent-node-type": reflect.ValueOf(n.GetProxy().ParentNode.Type).Type(),
+			"path":             n.GetProxy().Path,
+			"fullPath":         n.GetProxy().FullPath,
+		})
+		if n.GetProxy().Exclusive {
+			log.Error("node is already owned exclusively")
+		}
+	}
+
+	return n.Proxy
+}
+
+func (n *node) makeEventBus() *EventBus {
+	if n.EventBus == nil {
+		n.EventBus = NewEventBus()
+	}
+	return n.EventBus
+}
+
+func (n *node) SetProxy(proxy *Proxy) {
+	n.Proxy = proxy
+}
+
+func (n *node) GetProxy() *Proxy {
+	return n.Proxy
+}
+
+func (n *node) GetBranch(key string) *Branch {
+	if n.Branches != nil {
+		if branch, exists := n.Branches[key]; exists {
+			return branch
+		}
+	}
+	return nil
+}
+
+func (n *node) SetBranch(key string, branch *Branch) {
+	n.Branches[key] = branch
+}
+
+func (n *node) GetRoot() *root {
+	return n.Root
+}
+func (n *node) SetRoot(root *root) {
+	n.Root = root
+}