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service.go
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service.go
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// Copyright 2019-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 list
import (
listapi "github.com/atomix/atomix-api/go/atomix/primitive/list"
"github.com/atomix/atomix-go-framework/pkg/atomix/errors"
"github.com/atomix/atomix-go-framework/pkg/atomix/meta"
)
func init() {
registerServiceFunc(newService)
}
func newService(context ServiceContext) Service {
return &listService{
ServiceContext: context,
}
}
// listService is a state machine for a list primitive
type listService struct {
ServiceContext
items []listapi.Value
}
func (l *listService) Backup(writer SnapshotWriter) error {
values := make([]ListValue, 0, len(l.items))
for _, item := range l.items {
values = append(values, ListValue{
ObjectMeta: item.ObjectMeta,
Value: item.Value,
})
}
return writer.WriteState(&ListState{
Values: values,
})
}
func (l *listService) Restore(reader SnapshotReader) error {
state, err := reader.ReadState()
if err != nil {
return err
}
l.items = make([]listapi.Value, 0, len(state.Values))
for _, value := range state.Values {
l.items = append(l.items, listapi.Value{
ObjectMeta: value.ObjectMeta,
Value: value.Value,
})
}
return nil
}
func (l *listService) notify(event listapi.Event) error {
output := &listapi.EventsResponse{
Event: event,
}
for _, events := range l.Proposals().Events().List() {
if err := events.Notify(output); err != nil {
return err
}
}
return nil
}
func (l *listService) Size(size SizeProposal) error {
return size.Reply(&listapi.SizeResponse{
Size_: uint32(len(l.items)),
})
}
func (l *listService) Append(app AppendProposal) error {
index := len(l.items)
l.items = append(l.items, app.Request().Value)
err := l.notify(listapi.Event{
Type: listapi.Event_ADD,
Item: listapi.Item{
Index: uint32(index),
Value: app.Request().Value,
},
})
if err != nil {
return err
}
return app.Reply(&listapi.AppendResponse{})
}
func (l *listService) Insert(insert InsertProposal) error {
index := insert.Request().Item.Index
if index >= uint32(len(l.items)) {
return errors.NewInvalid("index %d out of bounds", index)
}
oldValue := l.items[index]
if err := checkPreconditions(oldValue, insert.Request().Preconditions); err != nil {
return err
}
value := insert.Request().Item.Value
values := append(l.items, value)
copy(values[index+1:], values[index:])
values[index] = value
l.items = values
err := l.notify(listapi.Event{
Type: listapi.Event_ADD,
Item: listapi.Item{
Index: uint32(index),
Value: value,
},
})
if err != nil {
return err
}
return insert.Reply(&listapi.InsertResponse{})
}
func (l *listService) Get(get GetProposal) error {
index := int(get.Request().Index)
if index >= len(l.items) {
return errors.NewInvalid("index %d out of bounds", index)
}
value := l.items[index]
return get.Reply(&listapi.GetResponse{
Item: listapi.Item{
Index: uint32(index),
Value: value,
},
})
}
func (l *listService) Set(set SetProposal) error {
index := set.Request().Item.Index
if index >= uint32(len(l.items)) {
return errors.NewInvalid("index %d out of bounds", index)
}
oldValue := l.items[index]
if err := checkPreconditions(oldValue, set.Request().Preconditions); err != nil {
return err
}
newValue := set.Request().Item.Value
l.items[index] = newValue
err := l.notify(listapi.Event{
Type: listapi.Event_REMOVE,
Item: listapi.Item{
Index: uint32(index),
Value: oldValue,
},
})
if err != nil {
return err
}
err = l.notify(listapi.Event{
Type: listapi.Event_ADD,
Item: listapi.Item{
Index: uint32(index),
Value: newValue,
},
})
if err != nil {
return err
}
return set.Reply(&listapi.SetResponse{})
}
func (l *listService) Remove(remove RemoveProposal) error {
index := remove.Request().Index
if index >= uint32(len(l.items)) {
return errors.NewInvalid("index %d out of bounds", index)
}
value := l.items[index]
if err := checkPreconditions(value, remove.Request().Preconditions); err != nil {
return err
}
l.items = append(l.items[:index], l.items[index+1:]...)
err := l.notify(listapi.Event{
Type: listapi.Event_REPLAY,
Item: listapi.Item{
Index: uint32(index),
Value: value,
},
})
if err != nil {
return err
}
return remove.Reply(&listapi.RemoveResponse{
Item: listapi.Item{
Index: uint32(index),
Value: value,
},
})
}
func (l *listService) Clear(clear ClearProposal) error {
l.items = []listapi.Value{}
return clear.Reply(&listapi.ClearResponse{})
}
func (l *listService) Events(events EventsProposal) error {
return nil
}
func (l *listService) Elements(elements ElementsProposal) error {
defer elements.Close()
for index, value := range l.items {
err := elements.Notify(&listapi.ElementsResponse{
Item: listapi.Item{
Index: uint32(index),
Value: value,
},
})
if err != nil {
return err
}
}
return nil
}
func checkPreconditions(value listapi.Value, preconditions []listapi.Precondition) error {
for _, precondition := range preconditions {
switch p := precondition.Precondition.(type) {
case *listapi.Precondition_Metadata:
if !meta.Equal(value.ObjectMeta, *p.Metadata) {
return errors.NewConflict("metadata precondition failed")
}
}
}
return nil
}