feat: add checkpoint (#6)

internal/checkpoint/checkpoint.go

@@ -0,0 +1,91 @@
+// Copyright 2023 Harness, Inc.
+//
+// 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 checkpoint
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sync"
+
+	"github.com/harness/harness-migrate/internal/util"
+)
+
+const checkpointFile = "checkpoint.ckpt"
+
+// CheckpointManager manages the checkpoints for different types of data
+type CheckpointManager struct {
+	mu                 sync.Mutex
+	data               map[string]any
+	checkpointLocation string
+}
+
+// NewCheckpointManager creates a new CheckpointManager
+func NewCheckpointManager(checkpointLocation string) *CheckpointManager {
+	return &CheckpointManager{
+		checkpointLocation: checkpointLocation,
+		data:               make(map[string]any),
+	}
+}
+
+// SaveCheckpoint saves a checkpoint for a given key
+func (cm *CheckpointManager) SaveCheckpoint(key string, value any) error {
+	data, err := func() ([]byte, error) {
+		cm.mu.Lock()
+		defer cm.mu.Unlock()
+
+		cm.data[key] = value
+		return json.Marshal(cm.data)
+	}()
+
+	if err != nil {
+		return fmt.Errorf("failed to marshal checkpoint: %v", err)
+	}
+
+	if err := util.WriteFile(filepath.Join(cm.checkpointLocation, checkpointFile), data); err != nil {
+		return fmt.Errorf("failed to write checkpoint file: %v", err)
+	}
+	return nil
+}
+
+// LoadCheckpoint loads the checkpoint data from a file
+func (cm *CheckpointManager) LoadCheckpoint() error {
+	if _, err := os.Stat(filepath.Join(cm.checkpointLocation, checkpointFile)); os.IsNotExist(err) {
+		return nil // No checkpoint file exists
+	}
+
+	data, err := os.ReadFile(filepath.Join(cm.checkpointLocation, checkpointFile))
+	if err != nil {
+		return fmt.Errorf("failed to read checkpoint file: %v", err)
+	}
+
+	cm.mu.Lock()
+	defer cm.mu.Unlock()
+	if err := json.Unmarshal(data, &cm.data); err != nil {
+		return fmt.Errorf("failed to unmarshal checkpoint: %v", err)
+	}
+
+	return nil
+}
+
+// GetCheckpoint gets the checkpoint for a given key
+func (cm *CheckpointManager) GetCheckpoint(key string) (any, bool) {
+	cm.mu.Lock()
+	defer cm.mu.Unlock()
+
+	value, exists := cm.data[key]
+	return value, exists
+}