feat(dbmanager): ✨ add support for existing SQL connections

* Introduced NewConnectionFromDB function to create connections from existing *sql.DB instances.
* Added ExistingDBProvider to wrap existing database connections for dbmanager features.
* Implemented tests for NewConnectionFromDB and ExistingDBProvider functionalities.

pkg/dbmanager/factory.go

@@ -1,6 +1,7 @@
 package dbmanager
 
 import (
+	"database/sql"
 	"fmt"
 
 	"github.com/bitechdev/ResolveSpec/pkg/dbmanager/providers"
@@ -49,3 +50,18 @@ func createProvider(dbType DatabaseType) (Provider, error) {
 // Provider is an alias to the providers.Provider interface
 // This allows dbmanager package consumers to use Provider without importing providers
 type Provider = providers.Provider
+
+// NewConnectionFromDB creates a new Connection from an existing *sql.DB
+// This allows you to use dbmanager features (ORM wrappers, health checks, etc.)
+// with a database connection that was opened outside of dbmanager
+//
+// Parameters:
+//   - name: A unique name for this connection
+//   - dbType: The database type (DatabaseTypePostgreSQL, DatabaseTypeSQLite, or DatabaseTypeMSSQL)
+//   - db: An existing *sql.DB connection
+//
+// Returns a Connection that wraps the existing *sql.DB
+func NewConnectionFromDB(name string, dbType DatabaseType, db *sql.DB) Connection {
+	provider := providers.NewExistingDBProvider(db, name)
+	return newSQLConnection(name, dbType, ConnectionConfig{Name: name, Type: dbType}, provider)
+}

pkg/dbmanager/factory_test.go

@@ -0,0 +1,210 @@
+package dbmanager
+
+import (
+	"context"
+	"database/sql"
+	"testing"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+func TestNewConnectionFromDB(t *testing.T) {
+	// Open a SQLite in-memory database
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	// Create a connection from the existing database
+	conn := NewConnectionFromDB("test-connection", DatabaseTypeSQLite, db)
+	if conn == nil {
+		t.Fatal("Expected connection to be created")
+	}
+
+	// Verify connection properties
+	if conn.Name() != "test-connection" {
+		t.Errorf("Expected name 'test-connection', got '%s'", conn.Name())
+	}
+
+	if conn.Type() != DatabaseTypeSQLite {
+		t.Errorf("Expected type DatabaseTypeSQLite, got '%s'", conn.Type())
+	}
+}
+
+func TestNewConnectionFromDB_Connect(t *testing.T) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	conn := NewConnectionFromDB("test-connection", DatabaseTypeSQLite, db)
+	ctx := context.Background()
+
+	// Connect should verify the existing connection works
+	err = conn.Connect(ctx)
+	if err != nil {
+		t.Errorf("Expected Connect to succeed, got error: %v", err)
+	}
+
+	// Cleanup
+	conn.Close()
+}
+
+func TestNewConnectionFromDB_Native(t *testing.T) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	conn := NewConnectionFromDB("test-connection", DatabaseTypeSQLite, db)
+	ctx := context.Background()
+
+	err = conn.Connect(ctx)
+	if err != nil {
+		t.Fatalf("Failed to connect: %v", err)
+	}
+	defer conn.Close()
+
+	// Get native DB
+	nativeDB, err := conn.Native()
+	if err != nil {
+		t.Errorf("Expected Native to succeed, got error: %v", err)
+	}
+
+	if nativeDB != db {
+		t.Error("Expected Native to return the same database instance")
+	}
+}
+
+func TestNewConnectionFromDB_Bun(t *testing.T) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	conn := NewConnectionFromDB("test-connection", DatabaseTypeSQLite, db)
+	ctx := context.Background()
+
+	err = conn.Connect(ctx)
+	if err != nil {
+		t.Fatalf("Failed to connect: %v", err)
+	}
+	defer conn.Close()
+
+	// Get Bun ORM
+	bunDB, err := conn.Bun()
+	if err != nil {
+		t.Errorf("Expected Bun to succeed, got error: %v", err)
+	}
+
+	if bunDB == nil {
+		t.Error("Expected Bun to return a non-nil instance")
+	}
+}
+
+func TestNewConnectionFromDB_GORM(t *testing.T) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	conn := NewConnectionFromDB("test-connection", DatabaseTypeSQLite, db)
+	ctx := context.Background()
+
+	err = conn.Connect(ctx)
+	if err != nil {
+		t.Fatalf("Failed to connect: %v", err)
+	}
+	defer conn.Close()
+
+	// Get GORM
+	gormDB, err := conn.GORM()
+	if err != nil {
+		t.Errorf("Expected GORM to succeed, got error: %v", err)
+	}
+
+	if gormDB == nil {
+		t.Error("Expected GORM to return a non-nil instance")
+	}
+}
+
+func TestNewConnectionFromDB_HealthCheck(t *testing.T) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	conn := NewConnectionFromDB("test-connection", DatabaseTypeSQLite, db)
+	ctx := context.Background()
+
+	err = conn.Connect(ctx)
+	if err != nil {
+		t.Fatalf("Failed to connect: %v", err)
+	}
+	defer conn.Close()
+
+	// Health check should succeed
+	err = conn.HealthCheck(ctx)
+	if err != nil {
+		t.Errorf("Expected HealthCheck to succeed, got error: %v", err)
+	}
+}
+
+func TestNewConnectionFromDB_Stats(t *testing.T) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	conn := NewConnectionFromDB("test-connection", DatabaseTypeSQLite, db)
+	ctx := context.Background()
+
+	err = conn.Connect(ctx)
+	if err != nil {
+		t.Fatalf("Failed to connect: %v", err)
+	}
+	defer conn.Close()
+
+	stats := conn.Stats()
+	if stats == nil {
+		t.Fatal("Expected stats to be returned")
+	}
+
+	if stats.Name != "test-connection" {
+		t.Errorf("Expected stats.Name to be 'test-connection', got '%s'", stats.Name)
+	}
+
+	if stats.Type != DatabaseTypeSQLite {
+		t.Errorf("Expected stats.Type to be DatabaseTypeSQLite, got '%s'", stats.Type)
+	}
+
+	if !stats.Connected {
+		t.Error("Expected stats.Connected to be true")
+	}
+}
+
+func TestNewConnectionFromDB_PostgreSQL(t *testing.T) {
+	// This test just verifies the factory works with PostgreSQL type
+	// It won't actually connect since we're using SQLite
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	conn := NewConnectionFromDB("test-pg", DatabaseTypePostgreSQL, db)
+	if conn == nil {
+		t.Fatal("Expected connection to be created")
+	}
+
+	if conn.Type() != DatabaseTypePostgreSQL {
+		t.Errorf("Expected type DatabaseTypePostgreSQL, got '%s'", conn.Type())
+	}
+}

pkg/dbmanager/providers/existing_db.go

@@ -0,0 +1,111 @@
+package providers
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"sync"
+
+	"go.mongodb.org/mongo-driver/mongo"
+)
+
+// ExistingDBProvider wraps an existing *sql.DB connection
+// This allows using dbmanager features with a database connection
+// that was opened outside of the dbmanager package
+type ExistingDBProvider struct {
+	db   *sql.DB
+	name string
+	mu   sync.RWMutex
+}
+
+// NewExistingDBProvider creates a new provider wrapping an existing *sql.DB
+func NewExistingDBProvider(db *sql.DB, name string) *ExistingDBProvider {
+	return &ExistingDBProvider{
+		db:   db,
+		name: name,
+	}
+}
+
+// Connect verifies the existing database connection is valid
+// It does NOT create a new connection, but ensures the existing one works
+func (p *ExistingDBProvider) Connect(ctx context.Context, cfg ConnectionConfig) error {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+
+	if p.db == nil {
+		return fmt.Errorf("database connection is nil")
+	}
+
+	// Verify the connection works
+	if err := p.db.PingContext(ctx); err != nil {
+		return fmt.Errorf("failed to ping existing database: %w", err)
+	}
+
+	return nil
+}
+
+// Close closes the underlying database connection
+func (p *ExistingDBProvider) Close() error {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+
+	if p.db == nil {
+		return nil
+	}
+
+	return p.db.Close()
+}
+
+// HealthCheck verifies the connection is alive
+func (p *ExistingDBProvider) HealthCheck(ctx context.Context) error {
+	p.mu.RLock()
+	defer p.mu.RUnlock()
+
+	if p.db == nil {
+		return fmt.Errorf("database connection is nil")
+	}
+
+	return p.db.PingContext(ctx)
+}
+
+// GetNative returns the wrapped *sql.DB
+func (p *ExistingDBProvider) GetNative() (*sql.DB, error) {
+	p.mu.RLock()
+	defer p.mu.RUnlock()
+
+	if p.db == nil {
+		return nil, fmt.Errorf("database connection is nil")
+	}
+
+	return p.db, nil
+}
+
+// GetMongo returns an error since this is a SQL database
+func (p *ExistingDBProvider) GetMongo() (*mongo.Client, error) {
+	return nil, ErrNotMongoDB
+}
+
+// Stats returns connection statistics
+func (p *ExistingDBProvider) Stats() *ConnectionStats {
+	p.mu.RLock()
+	defer p.mu.RUnlock()
+
+	stats := &ConnectionStats{
+		Name:      p.name,
+		Type:      "sql", // Generic since we don't know the specific type
+		Connected: p.db != nil,
+	}
+
+	if p.db != nil {
+		dbStats := p.db.Stats()
+		stats.OpenConnections = dbStats.OpenConnections
+		stats.InUse = dbStats.InUse
+		stats.Idle = dbStats.Idle
+		stats.WaitCount = dbStats.WaitCount
+		stats.WaitDuration = dbStats.WaitDuration
+		stats.MaxIdleClosed = dbStats.MaxIdleClosed
+		stats.MaxLifetimeClosed = dbStats.MaxLifetimeClosed
+	}
+
+	return stats
+}

pkg/dbmanager/providers/existing_db_test.go

@@ -0,0 +1,194 @@
+package providers
+
+import (
+	"context"
+	"database/sql"
+	"testing"
+	"time"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+func TestNewExistingDBProvider(t *testing.T) {
+	// Open a SQLite in-memory database
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	// Create provider
+	provider := NewExistingDBProvider(db, "test-db")
+	if provider == nil {
+		t.Fatal("Expected provider to be created")
+	}
+
+	if provider.name != "test-db" {
+		t.Errorf("Expected name 'test-db', got '%s'", provider.name)
+	}
+}
+
+func TestExistingDBProvider_Connect(t *testing.T) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	provider := NewExistingDBProvider(db, "test-db")
+	ctx := context.Background()
+
+	// Connect should verify the connection works
+	err = provider.Connect(ctx, nil)
+	if err != nil {
+		t.Errorf("Expected Connect to succeed, got error: %v", err)
+	}
+}
+
+func TestExistingDBProvider_Connect_NilDB(t *testing.T) {
+	provider := NewExistingDBProvider(nil, "test-db")
+	ctx := context.Background()
+
+	err := provider.Connect(ctx, nil)
+	if err == nil {
+		t.Error("Expected Connect to fail with nil database")
+	}
+}
+
+func TestExistingDBProvider_GetNative(t *testing.T) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	provider := NewExistingDBProvider(db, "test-db")
+
+	nativeDB, err := provider.GetNative()
+	if err != nil {
+		t.Errorf("Expected GetNative to succeed, got error: %v", err)
+	}
+
+	if nativeDB != db {
+		t.Error("Expected GetNative to return the same database instance")
+	}
+}
+
+func TestExistingDBProvider_GetNative_NilDB(t *testing.T) {
+	provider := NewExistingDBProvider(nil, "test-db")
+
+	_, err := provider.GetNative()
+	if err == nil {
+		t.Error("Expected GetNative to fail with nil database")
+	}
+}
+
+func TestExistingDBProvider_HealthCheck(t *testing.T) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	provider := NewExistingDBProvider(db, "test-db")
+	ctx := context.Background()
+
+	err = provider.HealthCheck(ctx)
+	if err != nil {
+		t.Errorf("Expected HealthCheck to succeed, got error: %v", err)
+	}
+}
+
+func TestExistingDBProvider_HealthCheck_ClosedDB(t *testing.T) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+
+	provider := NewExistingDBProvider(db, "test-db")
+
+	// Close the database
+	db.Close()
+
+	ctx := context.Background()
+	err = provider.HealthCheck(ctx)
+	if err == nil {
+		t.Error("Expected HealthCheck to fail with closed database")
+	}
+}
+
+func TestExistingDBProvider_GetMongo(t *testing.T) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	provider := NewExistingDBProvider(db, "test-db")
+
+	_, err = provider.GetMongo()
+	if err != ErrNotMongoDB {
+		t.Errorf("Expected ErrNotMongoDB, got: %v", err)
+	}
+}
+
+func TestExistingDBProvider_Stats(t *testing.T) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	// Set some connection pool settings to test stats
+	db.SetMaxOpenConns(10)
+	db.SetMaxIdleConns(5)
+	db.SetConnMaxLifetime(time.Hour)
+
+	provider := NewExistingDBProvider(db, "test-db")
+
+	stats := provider.Stats()
+	if stats == nil {
+		t.Fatal("Expected stats to be returned")
+	}
+
+	if stats.Name != "test-db" {
+		t.Errorf("Expected stats.Name to be 'test-db', got '%s'", stats.Name)
+	}
+
+	if stats.Type != "sql" {
+		t.Errorf("Expected stats.Type to be 'sql', got '%s'", stats.Type)
+	}
+
+	if !stats.Connected {
+		t.Error("Expected stats.Connected to be true")
+	}
+}
+
+func TestExistingDBProvider_Close(t *testing.T) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+
+	provider := NewExistingDBProvider(db, "test-db")
+
+	err = provider.Close()
+	if err != nil {
+		t.Errorf("Expected Close to succeed, got error: %v", err)
+	}
+
+	// Verify the database is closed
+	err = db.Ping()
+	if err == nil {
+		t.Error("Expected database to be closed")
+	}
+}
+
+func TestExistingDBProvider_Close_NilDB(t *testing.T) {
+	provider := NewExistingDBProvider(nil, "test-db")
+
+	err := provider.Close()
+	if err != nil {
+		t.Errorf("Expected Close to succeed with nil database, got error: %v", err)
+	}
+}

pkg/reflection/model_utils.go

@@ -1102,6 +1102,12 @@ func setFieldValue(field reflect.Value, value interface{}) error {
 		}
 	}
 
+	// If we can convert the type, do it
+	if valueReflect.Type().ConvertibleTo(field.Type()) {
+		field.Set(valueReflect.Convert(field.Type()))
+		return nil
+	}
+
 	// Handle struct types (like SqlTimeStamp, SqlDate, SqlTime which wrap SqlNull[time.Time])
 	if field.Kind() == reflect.Struct {
 
@@ -1113,9 +1119,9 @@ func setFieldValue(field reflect.Value, value interface{}) error {
 				// Call the Scan method with the value
 				results := scanMethod.Call([]reflect.Value{reflect.ValueOf(value)})
 				if len(results) > 0 {
-					// Check if there was an error
-					if err, ok := results[0].Interface().(error); ok && err != nil {
-						return err
+					// The Scan method returns error - check if it's nil
+					if !results[0].IsNil() {
+						return results[0].Interface().(error)
 					}
 					return nil
 				}
@@ -1170,12 +1176,6 @@ func setFieldValue(field reflect.Value, value interface{}) error {
 
 	}
 
-	// If we can convert the type, do it
-	if valueReflect.Type().ConvertibleTo(field.Type()) {
-		field.Set(valueReflect.Convert(field.Type()))
-		return nil
-	}
-
 	return fmt.Errorf("cannot convert %v to %v", valueReflect.Type(), field.Type())
 }
 

pkg/reflection/model_utils_stdlib_sqltypes_test.go

@@ -0,0 +1,120 @@
+package reflection_test
+
+import (
+	"database/sql"
+	"testing"
+	"time"
+
+	"github.com/bitechdev/ResolveSpec/pkg/reflection"
+)
+
+func TestMapToStruct_StandardSqlNullTypes(t *testing.T) {
+	// Test model with standard library sql.Null* types
+	type TestModel struct {
+		ID        int64           `bun:"id,pk" json:"id"`
+		Age       sql.NullInt64   `bun:"age" json:"age"`
+		Name      sql.NullString  `bun:"name" json:"name"`
+		Score     sql.NullFloat64 `bun:"score" json:"score"`
+		Active    sql.NullBool    `bun:"active" json:"active"`
+		UpdatedAt sql.NullTime    `bun:"updated_at" json:"updated_at"`
+	}
+
+	now := time.Now()
+	dataMap := map[string]any{
+		"id":         int64(100),
+		"age":        int64(25),
+		"name":       "John Doe",
+		"score":      95.5,
+		"active":     true,
+		"updated_at": now,
+	}
+
+	var result TestModel
+	err := reflection.MapToStruct(dataMap, &result)
+	if err != nil {
+		t.Fatalf("MapToStruct() error = %v", err)
+	}
+
+	// Verify ID
+	if result.ID != 100 {
+		t.Errorf("ID = %v, want 100", result.ID)
+	}
+
+	// Verify Age (sql.NullInt64)
+	if !result.Age.Valid {
+		t.Error("Age.Valid = false, want true")
+	}
+	if result.Age.Int64 != 25 {
+		t.Errorf("Age.Int64 = %v, want 25", result.Age.Int64)
+	}
+
+	// Verify Name (sql.NullString)
+	if !result.Name.Valid {
+		t.Error("Name.Valid = false, want true")
+	}
+	if result.Name.String != "John Doe" {
+		t.Errorf("Name.String = %v, want 'John Doe'", result.Name.String)
+	}
+
+	// Verify Score (sql.NullFloat64)
+	if !result.Score.Valid {
+		t.Error("Score.Valid = false, want true")
+	}
+	if result.Score.Float64 != 95.5 {
+		t.Errorf("Score.Float64 = %v, want 95.5", result.Score.Float64)
+	}
+
+	// Verify Active (sql.NullBool)
+	if !result.Active.Valid {
+		t.Error("Active.Valid = false, want true")
+	}
+	if !result.Active.Bool {
+		t.Error("Active.Bool = false, want true")
+	}
+
+	// Verify UpdatedAt (sql.NullTime)
+	if !result.UpdatedAt.Valid {
+		t.Error("UpdatedAt.Valid = false, want true")
+	}
+	if !result.UpdatedAt.Time.Equal(now) {
+		t.Errorf("UpdatedAt.Time = %v, want %v", result.UpdatedAt.Time, now)
+	}
+
+	t.Log("All standard library sql.Null* types handled correctly!")
+}
+
+func TestMapToStruct_StandardSqlNullTypes_WithNil(t *testing.T) {
+	// Test nil handling for standard library sql.Null* types
+	type TestModel struct {
+		ID   int64          `bun:"id,pk" json:"id"`
+		Age  sql.NullInt64  `bun:"age" json:"age"`
+		Name sql.NullString `bun:"name" json:"name"`
+	}
+
+	dataMap := map[string]any{
+		"id":   int64(200),
+		"age":  int64(30),
+		"name": nil, // Explicitly nil
+	}
+
+	var result TestModel
+	err := reflection.MapToStruct(dataMap, &result)
+	if err != nil {
+		t.Fatalf("MapToStruct() error = %v", err)
+	}
+
+	// Age should be valid
+	if !result.Age.Valid {
+		t.Error("Age.Valid = false, want true")
+	}
+	if result.Age.Int64 != 30 {
+		t.Errorf("Age.Int64 = %v, want 30", result.Age.Int64)
+	}
+
+	// Name should be invalid (null)
+	if result.Name.Valid {
+		t.Error("Name.Valid = true, want false (null)")
+	}
+
+	t.Log("Nil handling for sql.Null* types works correctly!")
+}