snapshot of https://github.com/casbin/casbin.git (master, 2026-09-15; blobs > 131072B omitted)

transaction_conflict.go

@@ -0,0 +1,137 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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 casbin
+
+import (
+	"fmt"
+
+	"github.com/casbin/casbin/v3/model"
+	"github.com/casbin/casbin/v3/persist"
+)
+
+// ConflictError represents a transaction conflict error.
+type ConflictError struct {
+	Operation persist.PolicyOperation
+	Reason    string
+}
+
+func (e *ConflictError) Error() string {
+	return fmt.Sprintf("transaction conflict: %s for operation %v", e.Reason, e.Operation)
+}
+
+// ConflictDetector detects conflicts between transaction operations and current model state.
+type ConflictDetector struct {
+	baseModel    model.Model               // Model snapshot when transaction started
+	currentModel model.Model               // Current model state
+	operations   []persist.PolicyOperation // Operations to be applied
+}
+
+// NewConflictDetector creates a new conflict detector instance.
+func NewConflictDetector(baseModel, currentModel model.Model, operations []persist.PolicyOperation) *ConflictDetector {
+	return &ConflictDetector{
+		baseModel:    baseModel,
+		currentModel: currentModel,
+		operations:   operations,
+	}
+}
+
+// DetectConflicts checks for conflicts between the transaction operations and current model state.
+// Returns nil if no conflicts are found, otherwise returns a ConflictError describing the conflict.
+func (cd *ConflictDetector) DetectConflicts() error {
+	for _, op := range cd.operations {
+		var err error
+		switch op.Type {
+		case persist.OperationAdd:
+			// Add operations never conflict
+			continue
+
+		case persist.OperationRemove:
+			err = cd.detectRemoveConflict(op)
+
+		case persist.OperationUpdate:
+			err = cd.detectUpdateConflict(op)
+		}
+
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// detectRemoveConflict checks for conflicts in remove operations.
+func (cd *ConflictDetector) detectRemoveConflict(op persist.PolicyOperation) error {
+	for _, rule := range op.Rules {
+		// Check if policy existed in base model
+		baseHasPolicy, err := cd.baseModel.HasPolicy(op.Section, op.PolicyType, rule)
+		if err != nil {
+			return err
+		}
+		if !baseHasPolicy {
+			continue // Policy didn't exist when transaction started
+		}
+
+		// Check if policy still exists in current model
+		currentHasPolicy, err := cd.currentModel.HasPolicy(op.Section, op.PolicyType, rule)
+		if err != nil {
+			return err
+		}
+		if !currentHasPolicy {
+			return &ConflictError{
+				Operation: op,
+				Reason:    "policy has been removed by another transaction",
+			}
+		}
+	}
+	return nil
+}
+
+// detectUpdateConflict checks for conflicts in update operations.
+func (cd *ConflictDetector) detectUpdateConflict(op persist.PolicyOperation) error {
+	for i, oldRule := range op.OldRules {
+		if i >= len(op.Rules) {
+			break
+		}
+		newRule := op.Rules[i]
+
+		// Check if old policy still exists
+		oldExists, err := cd.currentModel.HasPolicy(op.Section, op.PolicyType, oldRule)
+		if err != nil {
+			return err
+		}
+		if !oldExists {
+			return &ConflictError{
+				Operation: op,
+				Reason:    "policy to be updated no longer exists",
+			}
+		}
+
+		// Check if new policy already exists
+		newExists, err := cd.currentModel.HasPolicy(op.Section, op.PolicyType, newRule)
+		if err != nil {
+			return err
+		}
+		if newExists {
+			return &ConflictError{
+				Operation: op,
+				Reason:    "target policy already exists",
+			}
+		}
+	}
+	return nil
+}