feat: load packet logs from directory source

internal/isphere/file_source_test.go

@@ -2,6 +2,7 @@ package isphere
 
 import (
 	"os"
+	"path/filepath"
 	"reflect"
 	"testing"
 )
@@ -19,6 +20,23 @@ func TestLoadEncryptedPacketLogSourceFromFileReadsNonEmptyLines(t *testing.T) {
 	}
 }
 
+func TestLoadEncryptedPacketLogSourceFromDirectoryReadsSortedLogFiles(t *testing.T) {
+	root := t.TempDir()
+	writePacketLogFileAtPathForTest(t, root+"\\b.log", "\n  line-b1  \n")
+	writePacketLogFileAtPathForTest(t, root+"\\a.log", "line-a1\n\nline-a2\n")
+	writePacketLogFileAtPathForTest(t, root+"\\nested\\c.txt", "line-c1\n")
+	writePacketLogFileAtPathForTest(t, root+"\\ignored.tmp", "ignored\n")
+
+	got, err := LoadEncryptedPacketLogSourceFromDirectory(root)
+	if err != nil {
+		t.Fatalf("LoadEncryptedPacketLogSourceFromDirectory returned error: %v", err)
+	}
+	want := EncryptedPacketLogSource{Lines: []string{"line-a1", "line-a2", "line-b1", "line-c1"}}
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("source = %#v, want %#v", got, want)
+	}
+}
+
 func writePacketLogFileForTest(t *testing.T, content string) string {
 	t.Helper()
 	path := t.TempDir() + "\\packet.log"
@@ -27,3 +45,13 @@ func writePacketLogFileForTest(t *testing.T, content string) string {
 	}
 	return path
 }
+
+func writePacketLogFileAtPathForTest(t *testing.T, path string, content string) {
+	t.Helper()
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		t.Fatalf("create parent for %s: %v", path, err)
+	}
+	if err := os.WriteFile(path, []byte(content), 0o600); err != nil {
+		t.Fatalf("write test packet log %s: %v", path, err)
+	}
+}