client: add Logger interface to give programs more control

See https://codeberg.org/eduVPN/eduvpn-common/issues/102

2 files changed, 28 insertions, 6 deletions

diff --git a/client/client.go b/client/client.go
index d986fa6..e3f40aa 100644
--- a/client/client.go
+++ b/client/client.go
@@ -50,6 +50,17 @@ func CalculateGateway(cidr string) (string, error) {
 	return ret.String(), nil
 }
 
+// Logger is used by Client to control its logging. Client uses slog for all
+// logging which can be configured by implementations of this interface.
+type Logger interface {
+	// Init initializes the logging through slog. The given directory can
+	// be used to store the log files.
+	Init(dir string) (*slog.Logger, error)
+	// Close is called after logging has ended and should release all
+	// resources from Init.
+	Close() error
+}
+
 // Client is the main struct for the VPN client.
 type Client struct {
 	// The name of the client
@@ -70,8 +81,8 @@ type Client struct {
 	// tokenCacher
 	tokCacher TokenCacher
 
-	// logr is the log file rotater
-	logr *log.FileRotater
+	// logr is the logger
+	logr Logger
 
 	// cfg is the config
 	cfg *config.Config
@@ -137,10 +148,10 @@ func (c *Client) goTransition(id fsm.StateID) error {
 //   - name: the name of the client
 //   - directory: the directory where the config files are stored. Absolute or relative
 //   - stateCallback: the callback function for the FSM that takes two states (old and new) and the data as an interface
-//   - debug: whether or not we want to enable debugging
+//   - logger: the logger interface to use, if nil the default logger is used which logs to files in directory
 //
 // It returns an error if initialization failed, for example when discovery cannot be obtained and when there are no servers.
-func New(name string, version string, directory string, stateCallback func(FSMStateID, FSMStateID, any) bool) (c *Client, err error) {
+func New(name string, version string, directory string, stateCallback func(FSMStateID, FSMStateID, any) bool, logger Logger) (c *Client, err error) {
 	// We create the client by filling fields one by one
 	c = &Client{}
 
@@ -152,11 +163,16 @@ func New(name string, version string, directory string, stateCallback func(FSMSt
 		return nil, i18nerr.NewInternalf("The client registered with an invalid version: '%v'", version)
 	}
 
-	logr, err := log.Init(slog.LevelDebug, directory)
+	// Initialize provided logger or use default
+	if logger == nil {
+		logger = &log.Logger{}
+	}
+	c.logr = logger
+	slogger, err := c.logr.Init(directory)
 	if err != nil {
 		return nil, i18nerr.WrapInternalf(err, "The log file with directory: '%s' failed to initialize", directory)
 	}
-	c.logr = logr
+	slog.SetDefault(slogger)
 
 	// set client name
 	c.Name = name
diff --git a/client/client_test.go b/client/client_test.go
index 3ae5775..372c6c3 100644
--- a/client/client_test.go
+++ b/client/client_test.go
@@ -169,6 +169,7 @@ func TestServer(t *testing.T) {
 			go stateCallback(ck, oldState, newState, data)
 			return true
 		},
+		nil,
 	)
 	if err != nil {
 		t.Fatalf("Creating client error: %v", err)
@@ -216,6 +217,7 @@ func TestTokenExpired(t *testing.T) {
 			go stateCallback(ck, oldState, newState, data)
 			return true
 		},
+		nil,
 	)
 	if err != nil {
 		t.Fatalf("Creating client error: %v", err)
@@ -274,6 +276,7 @@ func TestInvalidProfileCorrected(t *testing.T) {
 			go stateCallback(ck, oldState, newState, data)
 			return true
 		},
+		nil,
 	)
 	if err != nil {
 		t.Fatalf("Creating client error: %v", err)
@@ -330,6 +333,7 @@ func TestConfigStartup(t *testing.T) {
 			go stateCallback(ck, oldState, newState, data)
 			return true
 		},
+		nil,
 	)
 	if err != nil {
 		t.Fatalf("Creating client error: %v", err)
@@ -390,6 +394,7 @@ func TestPreferTCP(t *testing.T) {
 			go stateCallback(ck, oldState, newState, data)
 			return true
 		},
+		nil,
 	)
 	if err != nil {
 		t.Fatalf("Creating client error: %v", err)
@@ -453,6 +458,7 @@ func TestInvalidClientID(t *testing.T) {
 			func(_ FSMStateID, _ FSMStateID, _ any) bool {
 				return true
 			},
+			nil,
 		)
 		if v {
 			if err != nil {