feat: enhance completion service with session management and language support

- Introduced session management using Redis for tracking active sessions.
- Added session claiming and releasing functionality in the completion manager.
- Enhanced HTTP and WebSocket completion endpoints to support multiple languages.
- Implemented request timeout and maximum body size configurations for API routes.
- Updated client-side code to handle session IDs and language parameters in completion requests.
- Improved error handling for unsupported languages and session conflicts.
- Added tests for the completion manager to ensure proper session handling and cleanup.

backend/internal/completion/manager_test.go

@@ -0,0 +1,125 @@
+package completion
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"testing"
+	"time"
+)
+
+type fakeRuntimeClient struct {
+	closed bool
+}
+
+func (f *fakeRuntimeClient) DidOpen(_ context.Context, _ string, _ string, _ int) error {
+	return nil
+}
+
+func (f *fakeRuntimeClient) DidChange(_ context.Context, _ string, _ string, _ int) error {
+	return nil
+}
+
+func (f *fakeRuntimeClient) Completion(_ context.Context, _ string, _ int, _ int) (Response, error) {
+	return Response{
+		Items: []Item{{Label: "ok"}},
+	}, nil
+}
+
+func (f *fakeRuntimeClient) Close() error {
+	f.closed = true
+	return nil
+}
+
+func TestManagerCompleteSelectsLanguageAndSession(t *testing.T) {
+	createCount := 0
+	factory := func(_ context.Context, spec LanguageServerSpec, _ string) (RuntimeClient, error) {
+		createCount++
+		if spec.Language != "go" {
+			return nil, fmt.Errorf("unexpected language: %s", spec.Language)
+		}
+		return &fakeRuntimeClient{}, nil
+	}
+
+	m := NewManager(ManagerConfig{WorkspaceDir: "."}, []LanguageServerSpec{
+		{Language: "go", LanguageID: "go", Command: "gopls"},
+	}, factory)
+	defer m.Close()
+
+	for i := 0; i < 2; i++ {
+		resp, err := m.Complete(context.Background(), Request{
+			Language:  "go",
+			SessionID: "s1",
+			URI:       "file:///main.go",
+			Text:      "package main",
+			Line:      0,
+			Character: 0,
+		})
+		if err != nil {
+			t.Fatalf("Complete() error = %v", err)
+		}
+		if len(resp.Items) != 1 || resp.Items[0].Label != "ok" {
+			t.Fatalf("unexpected response: %+v", resp)
+		}
+	}
+
+	if createCount != 1 {
+		t.Fatalf("expected one client creation, got %d", createCount)
+	}
+}
+
+func TestManagerCompleteUnsupportedLanguage(t *testing.T) {
+	m := NewManager(ManagerConfig{}, []LanguageServerSpec{
+		{Language: "go", LanguageID: "go", Command: "gopls"},
+	}, func(_ context.Context, _ LanguageServerSpec, _ string) (RuntimeClient, error) {
+		return &fakeRuntimeClient{}, nil
+	})
+	defer m.Close()
+
+	_, err := m.Complete(context.Background(), Request{
+		Language:  "python",
+		URI:       "file:///main.py",
+		Text:      "print('hi')",
+		Line:      0,
+		Character: 0,
+	})
+	if !errors.Is(err, ErrUnsupportedLanguage) {
+		t.Fatalf("expected ErrUnsupportedLanguage, got %v", err)
+	}
+}
+
+func TestManagerCleanupIdleSession(t *testing.T) {
+	client := &fakeRuntimeClient{}
+	m := NewManager(ManagerConfig{
+		WorkspaceDir:    ".",
+		SessionTTL:      30 * time.Millisecond,
+		CleanupInterval: 10 * time.Millisecond,
+	}, []LanguageServerSpec{
+		{Language: "go", LanguageID: "go", Command: "gopls"},
+	}, func(_ context.Context, _ LanguageServerSpec, _ string) (RuntimeClient, error) {
+		return client, nil
+	})
+	defer m.Close()
+
+	_, err := m.Complete(context.Background(), Request{
+		Language:  "go",
+		SessionID: "s2",
+		URI:       "file:///main.go",
+		Text:      "package main",
+		Line:      0,
+		Character: 0,
+	})
+	if err != nil {
+		t.Fatalf("Complete() error = %v", err)
+	}
+
+	time.Sleep(90 * time.Millisecond)
+
+	sessions := m.ActiveSessions()
+	if sessions["go"] != 0 {
+		t.Fatalf("expected session cleanup, got %+v", sessions)
+	}
+	if !client.closed {
+		t.Fatal("expected client to be closed by cleanup")
+	}
+}