refactor: interfaces and data types into the model package (#642)

## Checklist

- [x] I have read the [contribution guidelines](https://github.com/ooni/probe-cli/blob/master/CONTRIBUTING.md)
- [x] reference issue for this pull request: https://github.com/ooni/probe/issues/1885
- [x] related ooni/spec pull request: N/A

Location of the issue tracker: https://github.com/ooni/probe

## Description

This PR contains a set of changes to move important interfaces and data types into the `./internal/model` package.

The criteria for including an interface or data type in here is roughly that the type should be important and used by several packages. We are especially interested to move more interfaces here to increase modularity.

An additional side effect is that, by reading this package, one should be able to understand more quickly how different parts of the codebase interact with each other.

This is what I want to move in `internal/model`:

- [x] most important interfaces from `internal/netxlite`
- [x] everything that was previously part of `internal/engine/model`
- [x] mocks from `internal/netxlite/mocks` should also be moved in here as a subpackage

internal/engine/legacy/errorsx/dialer_test.go

@@ -8,7 +8,7 @@ import (
 	"testing"
 
 	"github.com/ooni/probe-cli/v3/internal/netxlite"
-	"github.com/ooni/probe-cli/v3/internal/netxlite/mocks"
+	"github.com/ooni/probe-cli/v3/internal/model/mocks"
 )
 
 func TestErrorWrapperDialerFailure(t *testing.T) {

internal/engine/legacy/errorsx/quic.go

@@ -6,8 +6,8 @@ import (
 	"net"
 
 	"github.com/lucas-clemente/quic-go"
+	"github.com/ooni/probe-cli/v3/internal/model"
 	"github.com/ooni/probe-cli/v3/internal/netxlite"
-	"github.com/ooni/probe-cli/v3/internal/netxlite/quicx"
 )
 
 // QUICContextDialer is a dialer for QUIC using Context.
@@ -22,7 +22,7 @@ type QUICContextDialer interface {
 // QUICListener listens for QUIC connections.
 type QUICListener interface {
 	// Listen creates a new listening UDPConn.
-	Listen(addr *net.UDPAddr) (quicx.UDPLikeConn, error)
+	Listen(addr *net.UDPAddr) (model.UDPLikeConn, error)
 }
 
 // ErrorWrapperQUICListener is a QUICListener that wraps errors.
@@ -34,7 +34,7 @@ type ErrorWrapperQUICListener struct {
 var _ QUICListener = &ErrorWrapperQUICListener{}
 
 // Listen implements QUICListener.Listen.
-func (qls *ErrorWrapperQUICListener) Listen(addr *net.UDPAddr) (quicx.UDPLikeConn, error) {
+func (qls *ErrorWrapperQUICListener) Listen(addr *net.UDPAddr) (model.UDPLikeConn, error) {
 	pconn, err := qls.QUICListener.Listen(addr)
 	if err != nil {
 		return nil, SafeErrWrapperBuilder{
@@ -45,15 +45,15 @@ func (qls *ErrorWrapperQUICListener) Listen(addr *net.UDPAddr) (quicx.UDPLikeCon
 	return &errorWrapperUDPConn{pconn}, nil
 }
 
-// errorWrapperUDPConn is a quicx.UDPLikeConn that wraps errors.
+// errorWrapperUDPConn is a model.UDPLikeConn that wraps errors.
 type errorWrapperUDPConn struct {
 	// UDPLikeConn is the underlying conn.
-	quicx.UDPLikeConn
+	model.UDPLikeConn
 }
 
-var _ quicx.UDPLikeConn = &errorWrapperUDPConn{}
+var _ model.UDPLikeConn = &errorWrapperUDPConn{}
 
-// WriteTo implements quicx.UDPLikeConn.WriteTo.
+// WriteTo implements model.UDPLikeConn.WriteTo.
 func (c *errorWrapperUDPConn) WriteTo(p []byte, addr net.Addr) (int, error) {
 	count, err := c.UDPLikeConn.WriteTo(p, addr)
 	if err != nil {
@@ -65,7 +65,7 @@ func (c *errorWrapperUDPConn) WriteTo(p []byte, addr net.Addr) (int, error) {
 	return count, nil
 }
 
-// ReadFrom implements quicx.UDPLikeConn.ReadFrom.
+// ReadFrom implements model.UDPLikeConn.ReadFrom.
 func (c *errorWrapperUDPConn) ReadFrom(b []byte) (int, net.Addr, error) {
 	n, addr, err := c.UDPLikeConn.ReadFrom(b)
 	if err != nil {

internal/engine/legacy/errorsx/quic_test.go

@@ -9,15 +9,16 @@ import (
 	"testing"
 
 	"github.com/lucas-clemente/quic-go"
+	"github.com/ooni/probe-cli/v3/internal/model"
+	"github.com/ooni/probe-cli/v3/internal/model/mocks"
 	"github.com/ooni/probe-cli/v3/internal/netxlite"
-	"github.com/ooni/probe-cli/v3/internal/netxlite/mocks"
-	"github.com/ooni/probe-cli/v3/internal/netxlite/quicx"
+	nlmocks "github.com/ooni/probe-cli/v3/internal/netxlite/mocks"
 )
 
 func TestErrorWrapperQUICListenerSuccess(t *testing.T) {
 	ql := &ErrorWrapperQUICListener{
 		QUICListener: &mocks.QUICListener{
-			MockListen: func(addr *net.UDPAddr) (quicx.UDPLikeConn, error) {
+			MockListen: func(addr *net.UDPAddr) (model.UDPLikeConn, error) {
 				return &net.UDPConn{}, nil
 			},
 		},
@@ -32,7 +33,7 @@ func TestErrorWrapperQUICListenerSuccess(t *testing.T) {
 func TestErrorWrapperQUICListenerFailure(t *testing.T) {
 	ql := &ErrorWrapperQUICListener{
 		QUICListener: &mocks.QUICListener{
-			MockListen: func(addr *net.UDPAddr) (quicx.UDPLikeConn, error) {
+			MockListen: func(addr *net.UDPAddr) (model.UDPLikeConn, error) {
 				return nil, io.EOF
 			},
 		},
@@ -130,7 +131,7 @@ func TestErrorWrapperUDPConnReadFromFailure(t *testing.T) {
 
 func TestErrorWrapperQUICDialerFailure(t *testing.T) {
 	ctx := context.Background()
-	d := &ErrorWrapperQUICDialer{Dialer: &mocks.QUICContextDialer{
+	d := &ErrorWrapperQUICDialer{Dialer: &nlmocks.QUICContextDialer{
 		MockDialContext: func(ctx context.Context, network, address string, tlsConfig *tls.Config, quicConfig *quic.Config) (quic.EarlySession, error) {
 			return nil, io.EOF
 		},

internal/engine/legacy/errorsx/resolver_test.go

@@ -7,7 +7,7 @@ import (
 	"testing"
 
 	"github.com/ooni/probe-cli/v3/internal/netxlite"
-	"github.com/ooni/probe-cli/v3/internal/netxlite/mocks"
+	"github.com/ooni/probe-cli/v3/internal/model/mocks"
 )
 
 func TestErrorWrapperResolverSuccess(t *testing.T) {

internal/engine/legacy/errorsx/tls_test.go

@@ -9,7 +9,7 @@ import (
 	"testing"
 
 	"github.com/ooni/probe-cli/v3/internal/netxlite"
-	"github.com/ooni/probe-cli/v3/internal/netxlite/mocks"
+	"github.com/ooni/probe-cli/v3/internal/model/mocks"
 )
 
 func TestErrorWrapperTLSHandshakerFailure(t *testing.T) {

internal/engine/legacy/netx/emitterdialer_test.go

@@ -10,7 +10,7 @@ import (
 
 	"github.com/ooni/probe-cli/v3/internal/engine/legacy/netx/handlers"
 	"github.com/ooni/probe-cli/v3/internal/engine/legacy/netx/modelx"
-	"github.com/ooni/probe-cli/v3/internal/netxlite/mocks"
+	"github.com/ooni/probe-cli/v3/internal/model/mocks"
 )
 
 func TestEmitterFailure(t *testing.T) {

internal/engine/legacy/netxlogger/netxlogger.go

@@ -9,22 +9,17 @@ import (
 	"strings"
 
 	"github.com/ooni/probe-cli/v3/internal/engine/legacy/netx/modelx"
+	"github.com/ooni/probe-cli/v3/internal/model"
 	"github.com/ooni/probe-cli/v3/internal/netxlite"
 )
 
-// Logger is the interface we expect from a logger
-type Logger interface {
-	Debug(msg string)
-	Debugf(format string, v ...interface{})
-}
-
 // Handler is a handler that logs events.
 type Handler struct {
-	logger Logger
+	logger model.DebugLogger
 }
 
 // NewHandler returns a new logging handler.
-func NewHandler(logger Logger) *Handler {
+func NewHandler(logger model.DebugLogger) *Handler {
 	return &Handler{logger: logger}
 }
 

internal/engine/legacy/oonidatamodel/oonidatamodel.go

@@ -18,7 +18,7 @@ import (
 
 	"github.com/ooni/probe-cli/v3/internal/engine/legacy/netx/modelx"
 	"github.com/ooni/probe-cli/v3/internal/engine/legacy/oonitemplates"
-	"github.com/ooni/probe-cli/v3/internal/engine/model"
+	"github.com/ooni/probe-cli/v3/internal/model"
 	"github.com/ooni/probe-cli/v3/internal/netxlite"
 )