etcd: add basic support

Part of #TNTP-4189

Author: bigbes

driver/etcd/etcd.go

@@ -4,11 +4,13 @@ package etcd
 
 import (
 	"context"
+	"errors"
 	"fmt"
 
 	etcd "go.etcd.io/etcd/client/v3"
 
 	"github.com/tarantool/go-storage/driver"
+	"github.com/tarantool/go-storage/kv"
 	"github.com/tarantool/go-storage/operation"
 	"github.com/tarantool/go-storage/predicate"
 	"github.com/tarantool/go-storage/tx"
@@ -23,6 +25,14 @@ type Driver struct {
 
 var (
 	_ driver.Driver = &Driver{} //nolint:exhaustruct
+
+	// Static error definitions to avoid dynamic errors.
+	errUnsupportedPredicateTarget  = errors.New("unsupported predicate target")
+	errValuePredicateRequiresBytes = errors.New("value predicate requires []byte value")
+	errUnsupportedValueOperation   = errors.New("unsupported operation for value predicate")
+	errVersionPredicateRequiresInt = errors.New("version predicate requires int64 value")
+	errUnsupportedVersionOperation = errors.New("unsupported operation for version predicate")
+	errUnsupportedOperationType    = errors.New("unsupported operation type")
 )
 
 // New creates a new etcd driver instance.
@@ -59,16 +69,229 @@ func New(ctx context.Context, endpoints []string) (*Driver, error) {
 // Execute executes a transactional operation with conditional logic.
 // It processes predicates to determine whether to execute thenOps or elseOps.
 func (d Driver) Execute(
-	_ context.Context,
-	_ []predicate.Predicate,
-	_ []operation.Operation,
-	_ []operation.Operation,
+	ctx context.Context,
+	predicates []predicate.Predicate,
+	thenOps []operation.Operation,
+	elseOps []operation.Operation,
 ) (tx.Response, error) {
-	panic("implement me")
+	txn := d.client.Txn(ctx)
+
+	for _, p := range predicates {
+		cmp, err := predicateToCmp(p)
+		if err != nil {
+			return tx.Response{}, fmt.Errorf("failed to convert predicate: %w", err)
+		}
+
+		txn = txn.If(cmp)
+	}
+
+	thenEtcdOps, err := operationsToEtcdOps(thenOps)
+	if err != nil {
+		return tx.Response{}, fmt.Errorf("failed to convert then operations: %w", err)
+	}
+
+	txn = txn.Then(thenEtcdOps...)
+
+	elseEtcdOps, err := operationsToEtcdOps(elseOps)
+	if err != nil {
+		return tx.Response{}, fmt.Errorf("failed to convert else operations: %w", err)
+	}
+
+	txn = txn.Else(elseEtcdOps...)
+
+	resp, err := txn.Commit()
+	if err != nil {
+		return tx.Response{}, fmt.Errorf("transaction failed: %w", err)
+	}
+
+	return etcdResponseToTxResponse(resp), nil
 }
 
 // Watch monitors changes to a specific key and returns a stream of events.
 // It supports optional watch configuration through the opts parameter.
-func (d Driver) Watch(_ context.Context, _ []byte, _ ...watch.Option) <-chan watch.Event {
-	panic("implement me")
+func (d Driver) Watch(ctx context.Context, key []byte, _ ...watch.Option) <-chan watch.Event {
+	// TODO: Apply watch options when implemented.
+	eventCh := make(chan watch.Event, 100) //nolint:mnd
+
+	go func() {
+		defer close(eventCh)
+
+		watchChan := d.client.Watch(ctx, string(key))
+
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case watchResp, ok := <-watchChan:
+				if !ok {
+					return
+				}
+
+				if watchResp.Err() != nil {
+					continue
+				}
+
+				for _, etcdEvent := range watchResp.Events {
+					event := etcdEventToWatchEvent(etcdEvent)
+					select {
+					case eventCh <- event:
+					case <-ctx.Done():
+						return
+					}
+				}
+			}
+		}
+	}()
+
+	return eventCh
+}
+
+// predicateToCmp converts a predicate to an etcd comparison.
+func predicateToCmp(pred predicate.Predicate) (etcd.Cmp, error) {
+	switch pred.Target() {
+	case predicate.TargetValue:
+		return valuePredicateToCmp(pred)
+	case predicate.TargetVersion:
+		return versionPredicateToCmp(pred)
+	default:
+		return etcd.Cmp{}, fmt.Errorf("%w: %v", errUnsupportedPredicateTarget, pred.Target())
+	}
+}
+
+// valuePredicateToCmp converts a value predicate to an etcd comparison.
+func valuePredicateToCmp(pred predicate.Predicate) (etcd.Cmp, error) {
+	key := string(pred.Key())
+	value, ok := pred.Value().([]byte)
+
+	if !ok {
+		return etcd.Cmp{}, errValuePredicateRequiresBytes
+	}
+
+	switch pred.Operation() {
+	case predicate.OpEqual:
+		return etcd.Compare(etcd.Value(key), "=", value), nil
+	case predicate.OpNotEqual:
+		return etcd.Compare(etcd.Value(key), "!=", value), nil
+	case predicate.OpGreater:
+		return etcd.Cmp{}, fmt.Errorf("%w: %v", errUnsupportedValueOperation, pred.Operation())
+	case predicate.OpLess:
+		return etcd.Cmp{}, fmt.Errorf("%w: %v", errUnsupportedValueOperation, pred.Operation())
+	default:
+		return etcd.Cmp{}, fmt.Errorf("%w: %v", errUnsupportedValueOperation, pred.Operation())
+	}
+}
+
+// versionPredicateToCmp converts a version predicate to an etcd comparison.
+func versionPredicateToCmp(pred predicate.Predicate) (etcd.Cmp, error) {
+	key := string(pred.Key())
+	version, ok := pred.Value().(int64)
+
+	if !ok {
+		return etcd.Cmp{}, errVersionPredicateRequiresInt
+	}
+
+	switch pred.Operation() {
+	case predicate.OpEqual:
+		return etcd.Compare(etcd.Version(key), "=", version), nil
+	case predicate.OpNotEqual:
+		return etcd.Compare(etcd.Version(key), "!=", version), nil
+	case predicate.OpGreater:
+		return etcd.Compare(etcd.Version(key), ">", version), nil
+	case predicate.OpLess:
+		return etcd.Compare(etcd.Version(key), "<", version), nil
+	default:
+		return etcd.Cmp{}, fmt.Errorf("%w: %v", errUnsupportedVersionOperation, pred.Operation())
+	}
+}
+
+// operationsToEtcdOps converts operations to etcd operations.
+func operationsToEtcdOps(ops []operation.Operation) ([]etcd.Op, error) {
+	etcdOps := make([]etcd.Op, 0, len(ops))
+	for _, op := range ops {
+		etcdOp, err := operationToEtcdOp(op)
+		if err != nil {
+			return nil, err
+		}
+
+		etcdOps = append(etcdOps, etcdOp)
+	}
+
+	return etcdOps, nil
+}
+
+// operationToEtcdOp converts an operation to an etcd operation.
+func operationToEtcdOp(storageOperation operation.Operation) (etcd.Op, error) {
+	key := string(storageOperation.Key())
+
+	switch storageOperation.Type() {
+	case operation.TypeGet:
+		return etcd.OpGet(key), nil
+	case operation.TypePut:
+		return etcd.OpPut(key, string(storageOperation.Value())), nil
+	case operation.TypeDelete:
+		return etcd.OpDelete(key), nil
+	default:
+		return etcd.Op{}, fmt.Errorf("%w: %v", errUnsupportedOperationType, storageOperation.Type())
+	}
+}
+
+// etcdResponseToTxResponse converts an etcd transaction response to tx.Response.
+func etcdResponseToTxResponse(resp *etcd.TxnResponse) tx.Response {
+	results := make([]tx.RequestResponse, 0, len(resp.Responses))
+
+	for _, etcdResp := range resp.Responses {
+		reqResp := tx.RequestResponse{
+			Success:  true,
+			KeyValue: nil,
+			Error:    nil,
+		}
+
+		switch {
+		case etcdResp.GetResponseRange() != nil:
+			getResp := etcdResp.GetResponseRange()
+			if len(getResp.Kvs) > 0 {
+				etcdKv := getResp.Kvs[0]
+
+				reqResp.KeyValue = &kv.KeyValue{
+					Key:            etcdKv.Key,
+					Value:          etcdKv.Value,
+					CreateRevision: etcdKv.CreateRevision,
+					ModRevision:    etcdKv.ModRevision,
+					Version:        etcdKv.Version,
+				}
+			}
+		case etcdResp.GetResponsePut() != nil:
+			// Put operations don't return data.
+		case etcdResp.GetResponseDeleteRange() != nil:
+			// Delete operations don't return data.
+		}
+
+		results = append(results, reqResp)
+	}
+
+	return tx.Response{
+		Succeeded: resp.Succeeded,
+		Results:   results,
+	}
+}
+
+// etcdEventToWatchEvent converts an etcd event to a watch event.
+func etcdEventToWatchEvent(etcdEvent *etcd.Event) watch.Event {
+	event := watch.Event{
+		Type:  watch.EventType(0), // Will be set below.
+		Key:   etcdEvent.Kv.Key,
+		Value: nil, // Will be set below.
+		Rev:   etcdEvent.Kv.ModRevision,
+	}
+
+	switch etcdEvent.Type {
+	case etcd.EventTypePut:
+		event.Type = watch.EventPut
+		event.Value = etcdEvent.Kv.Value
+	case etcd.EventTypeDelete:
+		event.Type = watch.EventDelete
+		event.Value = nil
+	}
+
+	return event
 }