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// Copyright 2025 The casbin Authors. All Rights Reserved.
//
// 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 casbin
import (
"fmt"
"github.com/casbin/casbin/v2/model"
"github.com/casbin/casbin/v2/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
}
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