[client] Port the file drop bindings to iOS

The iOS SDK package gets the same platform handle the Android bindings
carry: transfers, receiving policy, and per-sender rules on one profile,
attached to the engine when the client starts. Payloads are path-based
rather than stream-based, since the app group container is readable from
both processes, and the platform sink is dropped for the same reason:
delivery lands on the filesystem directly. The default destination is
seeded in the constructor because the app process opens handles of its
own while the extension is down.

client/ios/NetBirdSDK/filedrop_test.go

@@ -0,0 +1,182 @@
+//go:build ios
+
+package NetBirdSDK
+
+import (
+	"errors"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/netbirdio/netbird/client/internal/filedrop"
+)
+
+func TestPayloadFileReadsFromPath(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "greeting.txt")
+	if err := os.WriteFile(path, []byte("hello world"), 0o600); err != nil {
+		t.Fatalf("write payload: %v", err)
+	}
+
+	payloads := NewFileDropPayloads()
+	if err := payloads.AddFile("greeting.txt", 11, "text/plain", path); err != nil {
+		t.Fatalf("AddFile: %v", err)
+	}
+	if payloads.Length() != 1 {
+		t.Fatalf("expected 1 payload, got %d", payloads.Length())
+	}
+
+	stream, err := payloads.items[0].Open(0)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	got, err := io.ReadAll(stream)
+	if err != nil {
+		t.Fatalf("ReadAll: %v", err)
+	}
+	if string(got) != "hello world" {
+		t.Fatalf("got %q, want %q", got, "hello world")
+	}
+	if err := stream.Close(); err != nil {
+		t.Fatalf("Close: %v", err)
+	}
+}
+
+func TestPayloadFileHonoursOffset(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "greeting.txt")
+	if err := os.WriteFile(path, []byte("hello world"), 0o600); err != nil {
+		t.Fatalf("write payload: %v", err)
+	}
+
+	payloads := NewFileDropPayloads()
+	if err := payloads.AddFile("greeting.txt", 11, "", path); err != nil {
+		t.Fatalf("AddFile: %v", err)
+	}
+
+	stream, err := payloads.items[0].Open(6)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	defer stream.Close()
+
+	got, err := io.ReadAll(stream)
+	if err != nil {
+		t.Fatalf("ReadAll: %v", err)
+	}
+	if string(got) != "world" {
+		t.Fatalf("got %q, want %q", got, "world")
+	}
+}
+
+func TestPayloadRejectsMissingPathAndOversizedText(t *testing.T) {
+	payloads := NewFileDropPayloads()
+
+	if err := payloads.AddFile("no-path.bin", 1, "", ""); err == nil {
+		t.Fatal("expected an error for a file without a path")
+	}
+	if err := payloads.AddFile("", 1, "", "/tmp/x"); err == nil {
+		t.Fatal("expected an error for an empty file name")
+	}
+	if err := payloads.AddText("big", strings.Repeat("x", filedrop.MaxInlineTextSize+1)); err == nil {
+		t.Fatal("expected an error for oversized text")
+	}
+	if payloads.Length() != 0 {
+		t.Fatalf("expected no payloads, got %d", payloads.Length())
+	}
+}
+
+func TestFileDropPersistsSettingsPerProfile(t *testing.T) {
+	configDir := t.TempDir()
+	writeTestProfile(t, configDir, "aaaaaaaabbbbbbbbccccccccdddddddd")
+	writeTestProfile(t, configDir, "11111111222222223333333344444444")
+
+	first, err := NewFileDrop(configDir, "aaaaaaaabbbbbbbbccccccccdddddddd")
+	if err != nil {
+		t.Fatalf("NewFileDrop: %v", err)
+	}
+	defer first.Close()
+
+	if err := first.SetMode(FileDropModeAutoAccept); err != nil {
+		t.Fatalf("SetMode: %v", err)
+	}
+	if err := first.SetPeerRule("peer-key", FileDropRuleBlock); err != nil {
+		t.Fatalf("SetPeerRule: %v", err)
+	}
+
+	second, err := NewFileDrop(configDir, "11111111222222223333333344444444")
+	if err != nil {
+		t.Fatalf("NewFileDrop: %v", err)
+	}
+	defer second.Close()
+
+	if got := second.Mode(); got != FileDropModeAsk {
+		t.Fatalf("second profile mode = %d, want the default %d", got, FileDropModeAsk)
+	}
+	if got := second.PeerRule("peer-key"); got != FileDropRuleDefault {
+		t.Fatalf("second profile rule = %d, want %d", got, FileDropRuleDefault)
+	}
+
+	reopened, err := NewFileDrop(configDir, "aaaaaaaabbbbbbbbccccccccdddddddd")
+	if err != nil {
+		t.Fatalf("NewFileDrop: %v", err)
+	}
+	defer reopened.Close()
+
+	if got := reopened.Mode(); got != FileDropModeAutoAccept {
+		t.Fatalf("reopened mode = %d, want %d", got, FileDropModeAutoAccept)
+	}
+	if got := reopened.PeerRule("peer-key"); got != FileDropRuleBlock {
+		t.Fatalf("reopened rule = %d, want %d", got, FileDropRuleBlock)
+	}
+}
+
+func TestFileDropSeedsDefaultDestination(t *testing.T) {
+	configDir := t.TempDir()
+	writeTestProfile(t, configDir, "aaaaaaaabbbbbbbbccccccccdddddddd")
+
+	fd, err := NewFileDrop(configDir, "aaaaaaaabbbbbbbbccccccccdddddddd")
+	if err != nil {
+		t.Fatalf("NewFileDrop: %v", err)
+	}
+	defer fd.Close()
+
+	want := filepath.Join(configDir, filedropDataSubdir, "aaaaaaaabbbbbbbbccccccccdddddddd", "incoming")
+	if got := fd.DestinationDir(); got != want {
+		t.Fatalf("destination = %q, want %q", got, want)
+	}
+}
+
+func TestFileDropSendWithoutTunnelFails(t *testing.T) {
+	configDir := t.TempDir()
+	writeTestProfile(t, configDir, "aaaaaaaabbbbbbbbccccccccdddddddd")
+
+	fd, err := NewFileDrop(configDir, "aaaaaaaabbbbbbbbccccccccdddddddd")
+	if err != nil {
+		t.Fatalf("NewFileDrop: %v", err)
+	}
+	defer fd.Close()
+
+	payloads := NewFileDropPayloads()
+	if err := payloads.AddText("note", "hi"); err != nil {
+		t.Fatalf("AddText: %v", err)
+	}
+
+	if _, err := fd.Send("peer-key", "peer", "100.64.0.2", payloads); !errors.Is(err, filedrop.ErrNotConnected) {
+		t.Fatalf("Send error = %v, want %v", err, filedrop.ErrNotConnected)
+	}
+	if _, err := fd.Send("peer-key", "peer", "100.64.0.2", NewFileDropPayloads()); err == nil {
+		t.Fatal("expected an error when there is nothing to send")
+	}
+	if _, err := fd.Send("peer-key", "peer", "not-an-ip", payloads); err == nil {
+		t.Fatal("expected an error for an unparseable peer address")
+	}
+}
+
+func writeTestProfile(t *testing.T, configDir, id string) {
+	t.Helper()
+
+	if _, err := NewProfileManager(configDir).impl.ProfilePrefs(id); err != nil {
+		t.Fatalf("resolve prefs for %s: %v", id, err)
+	}
+}