cleanup: move legacy from internal/engine to internal (#759)

No functional change.

See https://github.com/ooni/probe/issues/2115

internal/legacy/assetsdir/assetsdir.go

@@ -0,0 +1,62 @@
+// Package assetsdir contains code to cleanup the assets dir. We removed
+// the assetsdir in the 3.9.0 development cycle.
+package assetsdir
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+)
+
+// ErrEmptyDir indicates that you passed to Cleanup an empty dir.
+var ErrEmptyDir = errors.New("empty assets directory")
+
+// Result is the result of a Cleanup run.
+type Result struct {
+	// ASNDatabaseErr is the error of deleting the
+	// file containing the old ASN database.
+	ASNDatabaseErr error
+
+	// CABundleErr is the error of deleting the file
+	// containing the old CA bundle.
+	CABundleErr error
+
+	// CountryDatabaseErr is the error of deleting the
+	// file containing the old country database.
+	CountryDatabaseErr error
+
+	// RmdirErr is the error of deleting the supposedly
+	// empty directory that contained assets.
+	RmdirErr error
+}
+
+// Cleanup removes data from the assetsdir. This function will
+// try to delete the known assets inside of dir. It then also
+// tries to delete the directory. If the directory is not empty,
+// this operation will fail. That means the user has put some
+// extra data in there and we don't want to remove it.
+//
+// Returns the Result of cleaning up the assets on success and
+// an error on failure. The only cause of error is passing to
+// this function an empty directory. The Result data structure
+// contains the result of each individual remove operation.
+func Cleanup(dir string) (*Result, error) {
+	return fcleanup(dir, os.Remove)
+}
+
+// fcleanup is a version of Cleanup where we can mock the real function
+// used for removing files and dirs, so we can write unit tests.
+func fcleanup(dir string, remove func(name string) error) (*Result, error) {
+	if dir == "" {
+		return nil, ErrEmptyDir
+	}
+	r := &Result{}
+	asndb := filepath.Join(dir, "asn.mmdb")
+	r.ASNDatabaseErr = os.Remove(asndb)
+	cabundle := filepath.Join(dir, "ca-bundle.pem")
+	r.CABundleErr = os.Remove(cabundle)
+	countrydb := filepath.Join(dir, "country.mmdb")
+	r.CountryDatabaseErr = os.Remove(countrydb)
+	r.RmdirErr = os.Remove(dir)
+	return r, nil
+}

internal/legacy/assetsdir/assetsdir_test.go

@@ -0,0 +1,40 @@
+package assetsdir
+
+import (
+	"errors"
+	"strings"
+	"testing"
+)
+
+func TestCleanupNormalUsage(t *testing.T) {
+	result, err := Cleanup("testdata")
+	if err != nil {
+		t.Fatal(err)
+	}
+	// we expect a bunch of ENOENT because the directory does not exist.
+	isExpectedErr := func(err error) bool {
+		return err != nil && strings.HasSuffix(err.Error(), "no such file or directory")
+	}
+	if !isExpectedErr(result.ASNDatabaseErr) {
+		t.Fatal("unexpected error", result.ASNDatabaseErr)
+	}
+	if !isExpectedErr(result.CABundleErr) {
+		t.Fatal("unexpected error", result.CABundleErr)
+	}
+	if !isExpectedErr(result.CountryDatabaseErr) {
+		t.Fatal("unexpected error", result.CountryDatabaseErr)
+	}
+	if !isExpectedErr(result.RmdirErr) {
+		t.Fatal("unexpected error", result.RmdirErr)
+	}
+}
+
+func TestCleanupWithEmptyInput(t *testing.T) {
+	result, err := Cleanup("")
+	if !errors.Is(err, ErrEmptyDir) {
+		t.Fatal("unexpected error", err)
+	}
+	if result != nil {
+		t.Fatal("expected nil result")
+	}
+}