initial draft of neo4j database driver

pkg/neo4j/serial.go

@@ -0,0 +1,113 @@
+package neo4j
+
+import (
+	"context"
+	"fmt"
+	"sync"
+)
+
+// Serial number management
+// We use a special Marker node in Neo4j to track the next available serial number
+
+const serialCounterKey = "serial_counter"
+
+var (
+	serialMutex sync.Mutex
+)
+
+// getNextSerial atomically increments and returns the next serial number
+func (n *N) getNextSerial() (uint64, error) {
+	serialMutex.Lock()
+	defer serialMutex.Unlock()
+
+	ctx := context.Background()
+
+	// Query current serial value
+	cypher := "MATCH (m:Marker {key: $key}) RETURN m.value AS value"
+	params := map[string]any{"key": serialCounterKey}
+
+	result, err := n.ExecuteRead(ctx, cypher, params)
+	if err != nil {
+		return 0, fmt.Errorf("failed to query serial counter: %w", err)
+	}
+
+	neo4jResult, ok := result.(interface {
+		Next(context.Context) bool
+		Record() *interface{}
+		Err() error
+	})
+	if !ok {
+		return 1, nil
+	}
+
+	var currentSerial uint64 = 1
+	if neo4jResult.Next(ctx) {
+		record := neo4jResult.Record()
+		if record != nil {
+			recordMap, ok := (*record).(map[string]any)
+			if ok {
+				if value, ok := recordMap["value"].(int64); ok {
+					currentSerial = uint64(value)
+				}
+			}
+		}
+	}
+
+	// Increment serial
+	nextSerial := currentSerial + 1
+
+	// Update counter
+	updateCypher := `
+MERGE (m:Marker {key: $key})
+SET m.value = $value`
+	updateParams := map[string]any{
+		"key":   serialCounterKey,
+		"value": int64(nextSerial),
+	}
+
+	_, err = n.ExecuteWrite(ctx, updateCypher, updateParams)
+	if err != nil {
+		return 0, fmt.Errorf("failed to update serial counter: %w", err)
+	}
+
+	return currentSerial, nil
+}
+
+// initSerialCounter initializes the serial counter if it doesn't exist
+func (n *N) initSerialCounter() error {
+	ctx := context.Background()
+
+	// Check if counter exists
+	cypher := "MATCH (m:Marker {key: $key}) RETURN m.value AS value"
+	params := map[string]any{"key": serialCounterKey}
+
+	result, err := n.ExecuteRead(ctx, cypher, params)
+	if err != nil {
+		return fmt.Errorf("failed to check serial counter: %w", err)
+	}
+
+	neo4jResult, ok := result.(interface {
+		Next(context.Context) bool
+		Record() *interface{}
+		Err() error
+	})
+	if ok && neo4jResult.Next(ctx) {
+		// Counter already exists
+		return nil
+	}
+
+	// Initialize counter at 1
+	initCypher := "CREATE (m:Marker {key: $key, value: $value})"
+	initParams := map[string]any{
+		"key":   serialCounterKey,
+		"value": int64(1),
+	}
+
+	_, err = n.ExecuteWrite(ctx, initCypher, initParams)
+	if err != nil {
+		return fmt.Errorf("failed to initialize serial counter: %w", err)
+	}
+
+	n.Logger.Infof("initialized serial counter")
+	return nil
+}