OwnCord/Server/api/upload_handler_test.go

package api_test

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"image"
	"image/color"
	"image/png"
	"io"
	"mime/multipart"
	"net/http"
	"net/http/httptest"
	"os"
	"strings"
	"testing"
	"testing/fstest"

	"github.com/go-chi/chi/v5"
	"github.com/owncord/server/api"
	"github.com/owncord/server/auth"
	"github.com/owncord/server/db"
	"github.com/owncord/server/permissions"
	"github.com/owncord/server/service"
	"github.com/owncord/server/storage"
)

// testPermSvc wires a PermissionService around the test DB so
// MountUploadRoutes can enforce its non-nil contract. The tests don't
// exercise per-channel ACLs directly — they go through the live
// permissions.Checker, which is the production path anyway.
func testPermSvc(database *db.DB) *service.PermissionService {
	return service.NewPermissionService(database, permissions.NewChecker(database))
}

// ─── schema for upload tests ─────────────────────────────────────────────────

var uploadTestSchema = []byte(`
CREATE TABLE IF NOT EXISTS roles (
    id          INTEGER PRIMARY KEY AUTOINCREMENT,
    name        TEXT    NOT NULL UNIQUE,
    color       TEXT,
    permissions INTEGER NOT NULL DEFAULT 0,
    position    INTEGER NOT NULL DEFAULT 0,
    is_default  INTEGER NOT NULL DEFAULT 0
);
INSERT OR IGNORE INTO roles (id, name, color, permissions, position, is_default) VALUES
    (1, 'Owner',     '#E74C3C', 2147483647, 100, 0),
    (2, 'Admin',     '#F39C12', 1073741823,  80, 0),
    (3, 'Moderator', '#3498DB', 1048575,     60, 0),
    (4, 'Member',    NULL,      1635,     40, 1);

CREATE TABLE IF NOT EXISTS users (
    id          INTEGER PRIMARY KEY AUTOINCREMENT,
    username    TEXT    NOT NULL UNIQUE COLLATE NOCASE,
    password    TEXT    NOT NULL,
    avatar      TEXT,
    role_id     INTEGER NOT NULL DEFAULT 4 REFERENCES roles(id),
    totp_secret TEXT,
    status      TEXT    NOT NULL DEFAULT 'offline',
    created_at  TEXT    NOT NULL DEFAULT (datetime('now')),
    last_seen   TEXT,
    banned      INTEGER NOT NULL DEFAULT 0,
    ban_reason  TEXT,
    ban_expires TEXT,
    identity_public_key TEXT
);
CREATE TABLE IF NOT EXISTS sessions (
    id         INTEGER PRIMARY KEY AUTOINCREMENT,
    user_id    INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
    token      TEXT    NOT NULL UNIQUE,
    device     TEXT,
    ip_address TEXT,
    created_at TEXT    NOT NULL DEFAULT (datetime('now')),
    last_used  TEXT    NOT NULL DEFAULT (datetime('now')),
    expires_at TEXT    NOT NULL
);
CREATE INDEX IF NOT EXISTS idx_sessions_token ON sessions(token);

CREATE TABLE IF NOT EXISTS channels (
    id             INTEGER PRIMARY KEY AUTOINCREMENT,
    name           TEXT    NOT NULL,
    type           TEXT    NOT NULL DEFAULT 'text',
    category       TEXT    NOT NULL DEFAULT '',
    topic          TEXT    NOT NULL DEFAULT '',
    position       INTEGER NOT NULL DEFAULT 0,
    slow_mode      INTEGER NOT NULL DEFAULT 0,
    archived       INTEGER NOT NULL DEFAULT 0,
    created_at     TEXT    NOT NULL DEFAULT (datetime('now')),
    voice_max_users INTEGER NOT NULL DEFAULT 0
);
CREATE TABLE IF NOT EXISTS messages (
    id          INTEGER PRIMARY KEY AUTOINCREMENT,
    channel_id  INTEGER NOT NULL REFERENCES channels(id),
    user_id     INTEGER NOT NULL REFERENCES users(id),
    content     TEXT    NOT NULL,
    created_at  TEXT    NOT NULL DEFAULT (datetime('now')),
    edited_at   TEXT,
    deleted     INTEGER NOT NULL DEFAULT 0
);
CREATE TABLE IF NOT EXISTS attachments (
    id          TEXT    PRIMARY KEY,
    message_id  INTEGER,
    filename    TEXT    NOT NULL,
    stored_as   TEXT    NOT NULL,
    mime_type   TEXT    NOT NULL,
    size        INTEGER NOT NULL,
    uploaded_at TEXT    NOT NULL DEFAULT (datetime('now')),
    width       INTEGER,
    height      INTEGER,
    uploader_id INTEGER REFERENCES users(id)
);
CREATE TABLE IF NOT EXISTS dm_participants (
    user_id    INTEGER NOT NULL REFERENCES users(id),
    channel_id INTEGER NOT NULL REFERENCES channels(id),
    opened     INTEGER NOT NULL DEFAULT 1,
    PRIMARY KEY (user_id, channel_id)
);
CREATE TABLE IF NOT EXISTS channel_overrides (
    channel_id INTEGER NOT NULL REFERENCES channels(id),
    role_id    INTEGER NOT NULL REFERENCES roles(id),
    allow      INTEGER NOT NULL DEFAULT 0,
    deny       INTEGER NOT NULL DEFAULT 0,
    PRIMARY KEY (channel_id, role_id)
);

CREATE TABLE IF NOT EXISTS settings (
    key   TEXT PRIMARY KEY,
    value TEXT NOT NULL
);
INSERT OR IGNORE INTO settings (key, value) VALUES
    ('server_name', 'OwnCord Server'),
    ('motd', 'Welcome!');
`)

// ─── helpers ─────────────────────────────────────────────────────────────────

func newUploadTestDB(t *testing.T) *db.DB {
	t.Helper()
	database, err := db.Open(":memory:")
	if err != nil {
		t.Fatalf("db.Open: %v", err)
	}
	t.Cleanup(func() { _ = database.Close() })
	migrFS := fstest.MapFS{"001_schema.sql": {Data: uploadTestSchema}}
	if err := db.MigrateFS(database, migrFS); err != nil {
		t.Fatalf("MigrateFS: %v", err)
	}
	return database
}

func newUploadTestStorage(t *testing.T) *storage.Storage {
	t.Helper()
	dir := t.TempDir()
	store, err := storage.New(dir, 10) // 10 MB max
	if err != nil {
		t.Fatalf("storage.New: %v", err)
	}
	return store
}

func buildUploadRouter(database *db.DB, store *storage.Storage, allowedOrigins []string) http.Handler {
	r := chi.NewRouter()
	limiter := auth.NewRateLimiter()
	api.MountUploadRoutes(r, database, store, limiter, allowedOrigins, testPermSvc(database))
	return r
}

func buildUploadRouterWithLimiter(database *db.DB, store *storage.Storage, limiter *auth.RateLimiter, allowedOrigins []string) http.Handler {
	r := chi.NewRouter()
	if limiter == nil {
		limiter = auth.NewRateLimiter()
	}
	api.MountUploadRoutes(r, database, store, limiter, allowedOrigins, testPermSvc(database))
	return r
}

// uploadCreateToken creates a user+session and returns the plaintext token.
func uploadCreateToken(t *testing.T, database *db.DB, username string, roleID int) string {
	t.Helper()
	_, err := database.CreateUser(context.Background(), username, "$2a$12$fake", roleID)
	if err != nil {
		t.Fatalf("CreateUser %q: %v", username, err)
	}
	token := "upload-test-token-" + username
	hash := auth.HashToken(token)
	_, err = database.ExecContext(context.Background(),
		`INSERT INTO sessions (user_id, token, device, ip_address, expires_at)
		 SELECT id, ?, 'test', '127.0.0.1', '2099-01-01T00:00:00Z' FROM users WHERE username = ?`,
		hash, username,
	)
	if err != nil {
		t.Fatalf("insert session for %q: %v", username, err)
	}
	return token
}

// makeMultipartFile builds a multipart form body with a single "file" field.
func makeMultipartFile(t *testing.T, fieldName, filename string, content []byte) (*bytes.Buffer, string) {
	t.Helper()
	body := &bytes.Buffer{}
	writer := multipart.NewWriter(body)
	part, err := writer.CreateFormFile(fieldName, filename)
	if err != nil {
		t.Fatalf("CreateFormFile: %v", err)
	}
	if _, err := io.Copy(part, bytes.NewReader(content)); err != nil {
		t.Fatalf("writing file part: %v", err)
	}
	if err := writer.Close(); err != nil {
		t.Fatalf("closing multipart writer: %v", err)
	}
	return body, writer.FormDataContentType()
}

// makePNGBytes generates a small valid PNG image and returns its raw bytes.
func makePNGBytes(t *testing.T, width, height int) []byte {
	t.Helper()
	img := image.NewRGBA(image.Rect(0, 0, width, height))
	for y := range height {
		for x := range width {
			img.Set(x, y, color.RGBA{R: 255, G: 0, B: 0, A: 255})
		}
	}
	var buf bytes.Buffer
	if err := png.Encode(&buf, img); err != nil {
		t.Fatalf("png.Encode: %v", err)
	}
	return buf.Bytes()
}

func doUpload(t *testing.T, router http.Handler, token, fieldName, filename string, content []byte) *httptest.ResponseRecorder {
	t.Helper()
	body, contentType := makeMultipartFile(t, fieldName, filename, content)
	req := httptest.NewRequest(http.MethodPost, "/api/v1/uploads", body)
	req.Header.Set("Content-Type", contentType)
	if token != "" {
		req.Header.Set("Authorization", "Bearer "+token)
	}
	req.RemoteAddr = "127.0.0.1:9999"
	rr := httptest.NewRecorder()
	router.ServeHTTP(rr, req)
	return rr
}

func doServeFile(t *testing.T, router http.Handler, fileID, token string, headers map[string]string) *httptest.ResponseRecorder {
	t.Helper()
	req := httptest.NewRequest(http.MethodGet, "/api/v1/files/"+fileID, nil)
	if token != "" {
		req.Header.Set("Authorization", "Bearer "+token)
	}
	for k, v := range headers {
		req.Header.Set(k, v)
	}
	req.RemoteAddr = "127.0.0.1:9999"
	rr := httptest.NewRecorder()
	router.ServeHTTP(rr, req)
	return rr
}

// ─── MountUploadRoutes ──────────────────────────────────────────────────────

func TestUpload_RoutesAreMounted(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "routeuser", 1)

	// POST /api/v1/uploads should not return 404/405.
	body, contentType := makeMultipartFile(t, "file", "test.txt", []byte("hello"))
	req := httptest.NewRequest(http.MethodPost, "/api/v1/uploads", body)
	req.Header.Set("Content-Type", contentType)
	req.Header.Set("Authorization", "Bearer "+token)
	req.RemoteAddr = "127.0.0.1:9999"
	rr := httptest.NewRecorder()
	router.ServeHTTP(rr, req)
	if rr.Code == http.StatusNotFound || rr.Code == http.StatusMethodNotAllowed {
		t.Errorf("POST /api/v1/uploads returned %d, route not mounted", rr.Code)
	}

	// GET /api/v1/files/{id} should not return 405 (401 or 404 are valid).
	req2 := httptest.NewRequest(http.MethodGet, "/api/v1/files/some-id", nil)
	req2.RemoteAddr = "127.0.0.1:9999"
	rr2 := httptest.NewRecorder()
	router.ServeHTTP(rr2, req2)
	if rr2.Code == http.StatusMethodNotAllowed {
		t.Errorf("GET /api/v1/files/{id} returned 405, route not mounted")
	}
}

// ─── handleUpload ───────────────────────────────────────────────────────────

func TestUpload_Success_TextFile(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "uploader1", 1)

	content := []byte("hello world this is a text file with enough bytes for detection")
	rr := doUpload(t, router, token, "file", "notes.txt", content)

	if rr.Code != http.StatusCreated {
		t.Fatalf("status = %d, want 201; body: %s", rr.Code, rr.Body.String())
	}

	var resp map[string]any
	if err := json.NewDecoder(rr.Body).Decode(&resp); err != nil {
		t.Fatalf("decode response: %v", err)
	}
	if resp["filename"] != "notes.txt" {
		t.Errorf("filename = %v, want notes.txt", resp["filename"])
	}
	if resp["url"] == nil || resp["url"] == "" {
		t.Error("expected non-empty url in response")
	}
	if resp["id"] == nil || resp["id"] == "" {
		t.Error("expected non-empty id in response")
	}
	if resp["mime"] == nil || resp["mime"] == "" {
		t.Error("expected non-empty mime in response")
	}

	// Verify attachment record was created in DB.
	att, err := database.GetAttachmentByID(context.Background(), resp["id"].(string))
	if err != nil {
		t.Fatalf("GetAttachmentByID: %v", err)
	}
	if att == nil {
		t.Fatal("expected attachment record in DB, got nil")
	}
	if att.Filename != "notes.txt" {
		t.Errorf("DB filename = %q, want notes.txt", att.Filename)
	}
}

func TestUpload_Success_PNGImage(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "imguploader", 1)

	pngData := makePNGBytes(t, 16, 8)
	rr := doUpload(t, router, token, "file", "image.png", pngData)

	if rr.Code != http.StatusCreated {
		t.Fatalf("status = %d, want 201; body: %s", rr.Code, rr.Body.String())
	}

	var resp map[string]any
	if err := json.NewDecoder(rr.Body).Decode(&resp); err != nil {
		t.Fatalf("decode response: %v", err)
	}
	if resp["mime"] != "image/png" {
		t.Errorf("mime = %v, want image/png", resp["mime"])
	}
	// Image upload should include dimensions.
	if resp["width"] == nil {
		t.Error("expected width for image upload")
	}
	if resp["height"] == nil {
		t.Error("expected height for image upload")
	}
	if int(resp["width"].(float64)) != 16 {
		t.Errorf("width = %v, want 16", resp["width"])
	}
	if int(resp["height"].(float64)) != 8 {
		t.Errorf("height = %v, want 8", resp["height"])
	}
}

func TestUpload_Unauthenticated(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)

	rr := doUpload(t, router, "", "file", "test.txt", []byte("hello"))
	if rr.Code != http.StatusUnauthorized {
		t.Errorf("status = %d, want 401", rr.Code)
	}
}

func TestUpload_InvalidToken(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)

	rr := doUpload(t, router, "invalid-token-123", "file", "test.txt", []byte("hello"))
	if rr.Code != http.StatusUnauthorized {
		t.Errorf("status = %d, want 401", rr.Code)
	}
}

func TestUpload_MissingFileField(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "nofield", 1)

	// Upload with wrong field name "attachment" instead of "file".
	rr := doUpload(t, router, token, "attachment", "test.txt", []byte("hello world"))
	if rr.Code != http.StatusBadRequest {
		t.Errorf("status = %d, want 400; body: %s", rr.Code, rr.Body.String())
	}

	var resp map[string]any
	if err := json.NewDecoder(rr.Body).Decode(&resp); err != nil {
		t.Fatalf("decode response: %v", err)
	}
	if resp["message"] != "missing file field" {
		t.Errorf("message = %v, want 'missing file field'", resp["message"])
	}
}

func TestUpload_InvalidMultipartForm(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "badform", 1)

	// Send a request with Content-Type claiming multipart but with a plain body.
	req := httptest.NewRequest(http.MethodPost, "/api/v1/uploads", bytes.NewReader([]byte("not multipart")))
	req.Header.Set("Content-Type", "multipart/form-data; boundary=nonexistent")
	req.Header.Set("Authorization", "Bearer "+token)
	req.RemoteAddr = "127.0.0.1:9999"
	rr := httptest.NewRecorder()
	router.ServeHTTP(rr, req)

	if rr.Code != http.StatusBadRequest {
		t.Errorf("status = %d, want 400; body: %s", rr.Code, rr.Body.String())
	}
}

func TestUpload_BlockedFileType_Executable(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "exeuploader", 1)

	// PE executable starts with "MZ".
	exeContent := append([]byte("MZ"), make([]byte, 100)...)
	rr := doUpload(t, router, token, "file", "malware.exe", exeContent)

	if rr.Code != http.StatusBadRequest {
		t.Errorf("status = %d, want 400; body: %s", rr.Code, rr.Body.String())
	}

	var resp map[string]any
	if err := json.NewDecoder(rr.Body).Decode(&resp); err != nil {
		t.Fatalf("decode response: %v", err)
	}
	msg, _ := resp["message"].(string)
	if msg == "" {
		t.Error("expected non-empty error message for blocked file type")
	}
}

func TestUpload_BlockedFileType_ShellScript(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "shuploader", 1)

	// Shell script starts with "#!".
	shContent := []byte("#!/bin/bash\necho hello\n")
	rr := doUpload(t, router, token, "file", "script.sh", shContent)

	if rr.Code != http.StatusBadRequest {
		t.Errorf("status = %d, want 400; body: %s", rr.Code, rr.Body.String())
	}
}

func TestUpload_BlockedFileType_ELF(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "elfuploader", 1)

	// ELF binary starts with \x7fELF.
	elfContent := append([]byte("\x7fELF"), make([]byte, 100)...)
	rr := doUpload(t, router, token, "file", "binary", elfContent)

	if rr.Code != http.StatusBadRequest {
		t.Errorf("status = %d, want 400; body: %s", rr.Code, rr.Body.String())
	}
}

func TestUpload_RateLimitedAfterBurst(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	limiter := auth.NewRateLimiter()
	router := buildUploadRouterWithLimiter(database, store, limiter, nil)
	token := uploadCreateToken(t, database, "burstuser", 1)
	otherToken := uploadCreateToken(t, database, "otherburstuser", 1)
	content := []byte("upload payload with enough bytes for content type detection")

	for range 10 {
		rr := doUpload(t, router, token, "file", "burst.txt", content)
		if rr.Code != http.StatusCreated {
			t.Fatalf("pre-limit upload status = %d, want 201; body: %s", rr.Code, rr.Body.String())
		}
	}

	rr := doUpload(t, router, token, "file", "burst.txt", content)
	if rr.Code != http.StatusTooManyRequests {
		t.Fatalf("rate-limited upload status = %d, want 429; body: %s", rr.Code, rr.Body.String())
	}

	var resp map[string]any
	if err := json.NewDecoder(rr.Body).Decode(&resp); err != nil {
		t.Fatalf("decode rate-limit response: %v", err)
	}
	if resp["error"] != "RATE_LIMITED" {
		t.Errorf("error = %v, want RATE_LIMITED", resp["error"])
	}

	rr = doUpload(t, router, otherToken, "file", "burst.txt", content)
	if rr.Code != http.StatusCreated {
		t.Fatalf("other user upload status = %d, want 201; body: %s", rr.Code, rr.Body.String())
	}
}

func TestUpload_OversizedFileRejected(t *testing.T) {
	database := newUploadTestDB(t)
	dir := t.TempDir()
	store, err := storage.New(dir, 1)
	if err != nil {
		t.Fatalf("storage.New: %v", err)
	}
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "largeupload", 1)
	content := bytes.Repeat([]byte("a"), (1<<20)+1)

	rr := doUpload(t, router, token, "file", "too-large.txt", content)
	if rr.Code != http.StatusBadRequest {
		t.Fatalf("oversized upload status = %d, want 400; body: %s", rr.Code, rr.Body.String())
	}

	var resp map[string]any
	if err := json.NewDecoder(rr.Body).Decode(&resp); err != nil {
		t.Fatalf("decode oversized response: %v", err)
	}
	message, _ := resp["message"].(string)
	if !strings.Contains(message, "file exceeds maximum size") {
		t.Fatalf("message = %q, want size rejection", message)
	}
	if resp["error"] != "BAD_REQUEST" {
		t.Errorf("error = %v, want BAD_REQUEST", resp["error"])
	}
}

func TestUpload_DBCreateAttachmentFailureDeletesStoredFile(t *testing.T) {
	database := newUploadTestDB(t)
	dir := t.TempDir()
	store, err := storage.New(dir, 10)
	if err != nil {
		t.Fatalf("storage.New: %v", err)
	}
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "dbfailupload", 1)

	if _, err := database.ExecContext(context.Background(), `DROP TABLE attachments`); err != nil {
		t.Fatalf("drop attachments table: %v", err)
	}

	content := []byte("content that will save to disk before attachment insert fails")
	rr := doUpload(t, router, token, "file", "cleanup.txt", content)
	if rr.Code != http.StatusInternalServerError {
		t.Fatalf("upload status = %d, want 500; body: %s", rr.Code, rr.Body.String())
	}

	var resp map[string]any
	if err := json.NewDecoder(rr.Body).Decode(&resp); err != nil {
		t.Fatalf("decode db failure response: %v", err)
	}
	if resp["error"] != "INTERNAL_ERROR" {
		t.Errorf("error = %v, want INTERNAL_ERROR", resp["error"])
	}

	entries, err := os.ReadDir(dir)
	if err != nil {
		t.Fatalf("ReadDir: %v", err)
	}
	if len(entries) != 0 {
		t.Fatalf("expected stored file cleanup on DB failure, found %d entries", len(entries))
	}
}

func TestUpload_SanitizesReservedFilenameToUnnamed(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "sanitizeupload", 1)
	content := []byte("content for reserved filename sanitization")

	rr := doUpload(t, router, token, "file", ".", content)
	if rr.Code != http.StatusCreated {
		t.Fatalf("status = %d, want 201; body: %s", rr.Code, rr.Body.String())
	}

	var resp map[string]any
	if err := json.NewDecoder(rr.Body).Decode(&resp); err != nil {
		t.Fatalf("decode response: %v", err)
	}
	if resp["filename"] != "unnamed" {
		t.Fatalf("filename = %v, want unnamed", resp["filename"])
	}

	att, err := database.GetAttachmentByID(context.Background(), resp["id"].(string))
	if err != nil {
		t.Fatalf("GetAttachmentByID: %v", err)
	}
	if att == nil {
		t.Fatal("expected attachment record in DB, got nil")
	}
	if att.Filename != "unnamed" {
		t.Fatalf("DB filename = %q, want unnamed", att.Filename)
	}
}

func TestUpload_SuccessfulUploadCreatesDBRecord(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "dbcheck", 1)

	content := []byte("some file content for database record verification test")
	rr := doUpload(t, router, token, "file", "dbtest.txt", content)

	if rr.Code != http.StatusCreated {
		t.Fatalf("status = %d, want 201; body: %s", rr.Code, rr.Body.String())
	}

	var resp map[string]any
	_ = json.NewDecoder(rr.Body).Decode(&resp)

	fileID := resp["id"].(string)
	att, err := database.GetAttachmentByID(context.Background(), fileID)
	if err != nil {
		t.Fatalf("GetAttachmentByID: %v", err)
	}
	if att == nil {
		t.Fatal("expected attachment record in DB")
	}
	if att.Filename != "dbtest.txt" {
		t.Errorf("filename = %q, want dbtest.txt", att.Filename)
	}
	if att.Size != int64(len(content)) {
		t.Errorf("size = %d, want %d", att.Size, len(content))
	}
	// message_id should be nil (unlinked upload).
	if att.MessageID != nil {
		t.Errorf("message_id = %v, want nil (unlinked)", att.MessageID)
	}
}

func TestUpload_ResponseFields(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "respfields", 1)

	content := []byte("response field validation content data")
	rr := doUpload(t, router, token, "file", "fields.dat", content)

	if rr.Code != http.StatusCreated {
		t.Fatalf("status = %d, want 201; body: %s", rr.Code, rr.Body.String())
	}

	var resp map[string]any
	if err := json.NewDecoder(rr.Body).Decode(&resp); err != nil {
		t.Fatalf("decode: %v", err)
	}

	// All required fields should be present.
	requiredFields := []string{"id", "filename", "size", "mime", "url"}
	for _, field := range requiredFields {
		if resp[field] == nil {
			t.Errorf("missing required field %q in response", field)
		}
	}

	// URL should contain the file ID.
	url, _ := resp["url"].(string)
	id, _ := resp["id"].(string)
	expectedURL := "/api/v1/files/" + id
	if url != expectedURL {
		t.Errorf("url = %q, want %q", url, expectedURL)
	}

	// Non-image files should not have width/height.
	if resp["width"] != nil {
		t.Errorf("expected nil width for non-image, got %v", resp["width"])
	}
	if resp["height"] != nil {
		t.Errorf("expected nil height for non-image, got %v", resp["height"])
	}
}

// ─── handleServeFile ────────────────────────────────────────────────────────

func TestServeFile_Success(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "serve1", 1)

	// Upload a file first.
	content := []byte("served file content with enough bytes for mime detection")
	rr := doUpload(t, router, token, "file", "served.txt", content)
	if rr.Code != http.StatusCreated {
		t.Fatalf("upload status = %d, want 201; body: %s", rr.Code, rr.Body.String())
	}

	var uploadResp map[string]any
	_ = json.NewDecoder(rr.Body).Decode(&uploadResp)
	fileID := uploadResp["id"].(string)

	// Serve the file (uploader is also the requester — allowed for unlinked files).
	rr2 := doServeFile(t, router, fileID, token, nil)
	if rr2.Code != http.StatusOK {
		t.Fatalf("serve status = %d, want 200; body: %s", rr2.Code, rr2.Body.String())
	}

	// Verify content type header is set.
	ct := rr2.Header().Get("Content-Type")
	if ct == "" {
		t.Error("expected Content-Type header on served file")
	}

	// Verify cache control header. Access-controlled downloads must be marked
	// private + no-cache so shared/proxy caches never store them (info-leak).
	cc := rr2.Header().Get("Cache-Control")
	if cc != "private, no-cache" {
		t.Errorf("Cache-Control = %q, want 'private, no-cache'", cc)
	}

	// Verify Content-Disposition header.
	cd := rr2.Header().Get("Content-Disposition")
	if cd == "" {
		t.Error("expected Content-Disposition header on served file")
	}
}

func TestServeFile_Success_PNG(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "servepng", 1)

	pngData := makePNGBytes(t, 4, 4)
	rr := doUpload(t, router, token, "file", "icon.png", pngData)
	if rr.Code != http.StatusCreated {
		t.Fatalf("upload status = %d, want 201; body: %s", rr.Code, rr.Body.String())
	}

	var uploadResp map[string]any
	_ = json.NewDecoder(rr.Body).Decode(&uploadResp)
	fileID := uploadResp["id"].(string)

	rr2 := doServeFile(t, router, fileID, token, nil)
	if rr2.Code != http.StatusOK {
		t.Fatalf("serve status = %d, want 200", rr2.Code)
	}

	ct := rr2.Header().Get("Content-Type")
	if ct != "image/png" {
		t.Errorf("Content-Type = %q, want image/png", ct)
	}
}

func TestServeFile_NotFound(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "notfounduser", 1)

	rr := doServeFile(t, router, "nonexistent-uuid-12345", token, nil)
	if rr.Code != http.StatusNotFound {
		t.Errorf("status = %d, want 404", rr.Code)
	}
}

func TestServeFile_EmptyID(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)

	// Request to /api/v1/files/ with no ID should 404 (chi won't match the route).
	req := httptest.NewRequest(http.MethodGet, "/api/v1/files/", nil)
	req.RemoteAddr = "127.0.0.1:9999"
	rr := httptest.NewRecorder()
	router.ServeHTTP(rr, req)

	if rr.Code != http.StatusNotFound {
		t.Errorf("status = %d, want 404", rr.Code)
	}
}

func TestServeFile_CORS_MatchingOrigin(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, []string{"https://app.example.com"})
	token := uploadCreateToken(t, database, "corsuser", 1)

	// Upload a file.
	content := []byte("cors test file content with sufficient length for detection")
	rr := doUpload(t, router, token, "file", "cors.txt", content)
	if rr.Code != http.StatusCreated {
		t.Fatalf("upload: %d; body: %s", rr.Code, rr.Body.String())
	}
	var uploadResp map[string]any
	_ = json.NewDecoder(rr.Body).Decode(&uploadResp)
	fileID := uploadResp["id"].(string)

	// Serve with matching origin.
	rr2 := doServeFile(t, router, fileID, token, map[string]string{
		"Origin": "https://app.example.com",
	})
	if rr2.Code != http.StatusOK {
		t.Fatalf("serve status = %d, want 200", rr2.Code)
	}
	acao := rr2.Header().Get("Access-Control-Allow-Origin")
	if acao != "https://app.example.com" {
		t.Errorf("ACAO = %q, want https://app.example.com", acao)
	}
}

func TestServeFile_CORS_NonMatchingOrigin(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, []string{"https://app.example.com"})
	token := uploadCreateToken(t, database, "corsmismatch", 1)

	content := []byte("cors non-matching test file content with sufficient length")
	rr := doUpload(t, router, token, "file", "cors2.txt", content)
	if rr.Code != http.StatusCreated {
		t.Fatalf("upload: %d", rr.Code)
	}
	var uploadResp map[string]any
	_ = json.NewDecoder(rr.Body).Decode(&uploadResp)
	fileID := uploadResp["id"].(string)

	rr2 := doServeFile(t, router, fileID, token, map[string]string{
		"Origin": "https://evil.example.com",
	})
	if rr2.Code != http.StatusOK {
		t.Fatalf("serve status = %d, want 200", rr2.Code)
	}
	acao := rr2.Header().Get("Access-Control-Allow-Origin")
	if acao != "" {
		t.Errorf("ACAO should be empty for non-matching origin, got %q", acao)
	}
}

func TestServeFile_CORS_WildcardOrigin(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, []string{"*"})
	token := uploadCreateToken(t, database, "corswildcard", 1)

	content := []byte("wildcard cors test file content with sufficient length")
	rr := doUpload(t, router, token, "file", "wild.txt", content)
	if rr.Code != http.StatusCreated {
		t.Fatalf("upload: %d", rr.Code)
	}
	var uploadResp map[string]any
	_ = json.NewDecoder(rr.Body).Decode(&uploadResp)
	fileID := uploadResp["id"].(string)

	rr2 := doServeFile(t, router, fileID, token, map[string]string{
		"Origin": "https://anything.example.com",
	})
	if rr2.Code != http.StatusOK {
		t.Fatalf("serve status = %d, want 200", rr2.Code)
	}
	acao := rr2.Header().Get("Access-Control-Allow-Origin")
	if acao != "https://anything.example.com" {
		t.Errorf("ACAO = %q, want https://anything.example.com for wildcard", acao)
	}
}

func TestServeFile_CORS_NoOriginHeader(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, []string{"*"})
	token := uploadCreateToken(t, database, "corsnoorigin", 1)

	content := []byte("no origin header test file content with sufficient length")
	rr := doUpload(t, router, token, "file", "noorigin.txt", content)
	if rr.Code != http.StatusCreated {
		t.Fatalf("upload: %d", rr.Code)
	}
	var uploadResp map[string]any
	_ = json.NewDecoder(rr.Body).Decode(&uploadResp)
	fileID := uploadResp["id"].(string)

	// No Origin header — CORS headers should not be set.
	rr2 := doServeFile(t, router, fileID, token, nil)
	if rr2.Code != http.StatusOK {
		t.Fatalf("serve status = %d, want 200", rr2.Code)
	}
	acao := rr2.Header().Get("Access-Control-Allow-Origin")
	if acao != "" {
		t.Errorf("ACAO should be empty when no Origin sent, got %q", acao)
	}
}

func TestServeFile_DBRecordMissing_ReturnsNotFound(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "dbmissing", 1)

	// No file uploaded — DB has no record.
	rr := doServeFile(t, router, "aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee", token, nil)
	if rr.Code != http.StatusNotFound {
		t.Errorf("status = %d, want 404", rr.Code)
	}
}

func TestServeFile_StorageFileMissing_ReturnsNotFound(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "storemissing", 1)

	// Upload a file, then delete it from storage.
	content := []byte("file that will be deleted from storage backend")
	rr := doUpload(t, router, token, "file", "vanish.txt", content)
	if rr.Code != http.StatusCreated {
		t.Fatalf("upload: %d; body: %s", rr.Code, rr.Body.String())
	}
	var uploadResp map[string]any
	_ = json.NewDecoder(rr.Body).Decode(&uploadResp)
	fileID := uploadResp["id"].(string)

	// Delete the file from storage directly.
	if err := store.Delete(fileID); err != nil {
		t.Fatalf("store.Delete: %v", err)
	}

	// Serve should return 404 because the file is missing from disk.
	rr2 := doServeFile(t, router, fileID, token, nil)
	if rr2.Code != http.StatusNotFound {
		t.Errorf("status = %d, want 404 for missing storage file", rr2.Code)
	}
}

// ─── Table-driven tests for blocked file types ──────────────────────────────

func TestUpload_BlockedFileTypes(t *testing.T) {
	tests := []struct {
		name     string
		filename string
		content  []byte
	}{
		{"PE executable", "test.exe", append([]byte("MZ"), make([]byte, 50)...)},
		{"ELF binary", "test.bin", append([]byte("\x7fELF"), make([]byte, 50)...)},
		{"Mach-O 64-bit", "test.macho", append([]byte("\xcf\xfa\xed\xfe"), make([]byte, 50)...)},
		{"Mach-O 32-bit", "test.macho32", append([]byte("\xce\xfa\xed\xfe"), make([]byte, 50)...)},
		{"shell script", "test.sh", []byte("#!/bin/bash\necho hello\n")},
	}

	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			database := newUploadTestDB(t)
			store := newUploadTestStorage(t)
			router := buildUploadRouter(database, store, nil)
			token := uploadCreateToken(t, database, fmt.Sprintf("blocked_%s", tc.name), 1)

			rr := doUpload(t, router, token, "file", tc.filename, tc.content)
			if rr.Code != http.StatusBadRequest {
				t.Errorf("status = %d, want 400 for %s; body: %s", rr.Code, tc.name, rr.Body.String())
			}
		})
	}
}

// ─── End-to-end upload then serve round-trip ────────────────────────────────

func TestUpload_ThenServe_RoundTrip(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "roundtrip", 1)

	content := []byte("round trip test content for full upload and serve cycle")
	rr := doUpload(t, router, token, "file", "roundtrip.txt", content)
	if rr.Code != http.StatusCreated {
		t.Fatalf("upload: %d; body: %s", rr.Code, rr.Body.String())
	}

	var uploadResp map[string]any
	_ = json.NewDecoder(rr.Body).Decode(&uploadResp)
	fileID := uploadResp["id"].(string)
	url := uploadResp["url"].(string)

	// Serve using the URL from the upload response.
	req := httptest.NewRequest(http.MethodGet, url, nil)
	req.Header.Set("Authorization", "Bearer "+token)
	req.RemoteAddr = "127.0.0.1:9999"
	rr2 := httptest.NewRecorder()
	router.ServeHTTP(rr2, req)

	if rr2.Code != http.StatusOK {
		t.Fatalf("serve status = %d, want 200", rr2.Code)
	}

	// Verify the served content matches what was uploaded.
	servedBody := rr2.Body.Bytes()
	if !bytes.Equal(servedBody, content) {
		t.Errorf("served content length = %d, want %d", len(servedBody), len(content))
	}

	_ = fileID // used above
}

func TestUpload_ThenServe_PNG_RoundTrip(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "pngrt", 1)

	pngData := makePNGBytes(t, 32, 32)
	rr := doUpload(t, router, token, "file", "test.png", pngData)
	if rr.Code != http.StatusCreated {
		t.Fatalf("upload: %d; body: %s", rr.Code, rr.Body.String())
	}

	var uploadResp map[string]any
	_ = json.NewDecoder(rr.Body).Decode(&uploadResp)
	url := uploadResp["url"].(string)

	req := httptest.NewRequest(http.MethodGet, url, nil)
	req.Header.Set("Authorization", "Bearer "+token)
	req.RemoteAddr = "127.0.0.1:9999"
	rr2 := httptest.NewRecorder()
	router.ServeHTTP(rr2, req)

	if rr2.Code != http.StatusOK {
		t.Fatalf("serve: %d", rr2.Code)
	}
	if rr2.Header().Get("Content-Type") != "image/png" {
		t.Errorf("Content-Type = %q, want image/png", rr2.Header().Get("Content-Type"))
	}

	// Verify served bytes match original.
	if !bytes.Equal(rr2.Body.Bytes(), pngData) {
		t.Error("served PNG bytes differ from uploaded bytes")
	}
}

// ─── Access Control Tests (BUG-092) ────────────────────────────────────────

func TestServeFile_Unauthenticated_Returns401(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "acl401uploader", 1)

	// Upload a file.
	content := []byte("private file content for unauthenticated access test")
	rr := doUpload(t, router, token, "file", "private.txt", content)
	if rr.Code != http.StatusCreated {
		t.Fatalf("upload: %d; body: %s", rr.Code, rr.Body.String())
	}
	var resp map[string]any
	_ = json.NewDecoder(rr.Body).Decode(&resp)
	fileID := resp["id"].(string)

	// Request without auth token.
	rr2 := doServeFile(t, router, fileID, "", nil)
	if rr2.Code != http.StatusUnauthorized {
		t.Errorf("status = %d, want 401 for unauthenticated file request", rr2.Code)
	}
}

func TestServeFile_UnlinkedFile_UploaderCanAccess(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "acluploader", 1)

	content := []byte("file owned by uploader for ownership access test")
	rr := doUpload(t, router, token, "file", "mine.txt", content)
	if rr.Code != http.StatusCreated {
		t.Fatalf("upload: %d; body: %s", rr.Code, rr.Body.String())
	}
	var resp map[string]any
	_ = json.NewDecoder(rr.Body).Decode(&resp)
	fileID := resp["id"].(string)

	// Uploader can access their own unlinked file.
	rr2 := doServeFile(t, router, fileID, token, nil)
	if rr2.Code != http.StatusOK {
		t.Errorf("status = %d, want 200 for uploader accessing own file", rr2.Code)
	}
}

func TestServeFile_UnlinkedFile_OtherUserForbidden(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	uploaderToken := uploadCreateToken(t, database, "aclowner", 4) // Member role
	otherToken := uploadCreateToken(t, database, "aclother", 4)    // Member role

	content := []byte("private file content for other-user forbidden test")
	rr := doUpload(t, router, uploaderToken, "file", "secret.txt", content)
	if rr.Code != http.StatusCreated {
		t.Fatalf("upload: %d; body: %s", rr.Code, rr.Body.String())
	}
	var resp map[string]any
	_ = json.NewDecoder(rr.Body).Decode(&resp)
	fileID := resp["id"].(string)

	// Other user cannot access unlinked file.
	rr2 := doServeFile(t, router, fileID, otherToken, nil)
	if rr2.Code != http.StatusForbidden {
		t.Errorf("status = %d, want 403 for other user accessing unlinked file", rr2.Code)
	}
}

func TestServeFile_AdminBypassesAllChecks(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	uploaderToken := uploadCreateToken(t, database, "acluploaderadmin", 4) // Member
	adminToken := uploadCreateToken(t, database, "acladmin", 1)            // Owner (admin)

	content := []byte("file for admin bypass test content with sufficient bytes")
	rr := doUpload(t, router, uploaderToken, "file", "restricted.txt", content)
	if rr.Code != http.StatusCreated {
		t.Fatalf("upload: %d; body: %s", rr.Code, rr.Body.String())
	}
	var resp map[string]any
	_ = json.NewDecoder(rr.Body).Decode(&resp)
	fileID := resp["id"].(string)

	// Admin can access any file regardless of ownership.
	rr2 := doServeFile(t, router, fileID, adminToken, nil)
	if rr2.Code != http.StatusOK {
		t.Errorf("status = %d, want 200 for admin bypass", rr2.Code)
	}
}

func TestServeFile_LinkedToGuildChannel_MemberWithPerm(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token := uploadCreateToken(t, database, "guildmember", 4) // Member role (perms=1635, includes ReadMessages=0x0002)

	// Upload a file.
	content := []byte("guild channel attachment content for permission test")
	rr := doUpload(t, router, token, "file", "guild.txt", content)
	if rr.Code != http.StatusCreated {
		t.Fatalf("upload: %d; body: %s", rr.Code, rr.Body.String())
	}
	var resp map[string]any
	_ = json.NewDecoder(rr.Body).Decode(&resp)
	fileID := resp["id"].(string)

	// Create a guild channel and link the attachment via a message.
	_, err := database.ExecContext(context.Background(), `INSERT INTO channels (id, name, type) VALUES (1, 'general', 'text')`)
	if err != nil {
		t.Fatalf("insert channel: %v", err)
	}
	// Get the uploader's user ID.
	var userID int64
	if err := database.QueryRowContext(context.Background(), `SELECT id FROM users WHERE username = 'guildmember'`).Scan(&userID); err != nil {
		t.Fatalf("get user id: %v", err)
	}
	_, err = database.ExecContext(context.Background(), `INSERT INTO messages (id, channel_id, user_id, content) VALUES (1, 1, ?, 'test')`, userID)
	if err != nil {
		t.Fatalf("insert message: %v", err)
	}
	_, err = database.ExecContext(context.Background(), `UPDATE attachments SET message_id = 1 WHERE id = ?`, fileID)
	if err != nil {
		t.Fatalf("link attachment: %v", err)
	}

	// Member with ReadMessages should be able to access.
	rr2 := doServeFile(t, router, fileID, token, nil)
	if rr2.Code != http.StatusOK {
		t.Errorf("status = %d, want 200 for guild member with READ_MESSAGES", rr2.Code)
	}
}

func TestServeFile_LinkedToGuildChannel_MemberWithoutPerm(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	uploaderToken := uploadCreateToken(t, database, "guilduploader2", 1) // Owner (to upload)
	memberToken := uploadCreateToken(t, database, "guildnoperm", 4)      // Member

	// Upload a file.
	content := []byte("guild channel attachment content for denied permission test")
	rr := doUpload(t, router, uploaderToken, "file", "restricted.txt", content)
	if rr.Code != http.StatusCreated {
		t.Fatalf("upload: %d; body: %s", rr.Code, rr.Body.String())
	}
	var resp map[string]any
	_ = json.NewDecoder(rr.Body).Decode(&resp)
	fileID := resp["id"].(string)

	// Create channel and link.
	_, err := database.ExecContext(context.Background(), `INSERT INTO channels (id, name, type) VALUES (1, 'secret', 'text')`)
	if err != nil {
		t.Fatalf("insert channel: %v", err)
	}
	var uploaderID int64
	if err := database.QueryRowContext(context.Background(), `SELECT id FROM users WHERE username = 'guilduploader2'`).Scan(&uploaderID); err != nil {
		t.Fatalf("get user id: %v", err)
	}
	_, err = database.ExecContext(context.Background(), `INSERT INTO messages (id, channel_id, user_id, content) VALUES (1, 1, ?, 'test')`, uploaderID)
	if err != nil {
		t.Fatalf("insert message: %v", err)
	}
	_, err = database.ExecContext(context.Background(), `UPDATE attachments SET message_id = 1 WHERE id = ?`, fileID)
	if err != nil {
		t.Fatalf("link attachment: %v", err)
	}
	// Deny ReadMessages (0x0002) for role 4 (Member) on channel 1.
	_, err = database.ExecContext(context.Background(), `INSERT INTO channel_overrides (channel_id, role_id, allow, deny) VALUES (1, 4, 0, 2)`)
	if err != nil {
		t.Fatalf("insert channel_override: %v", err)
	}

	// Member without ReadMessages should get 403.
	rr2 := doServeFile(t, router, fileID, memberToken, nil)
	if rr2.Code != http.StatusForbidden {
		t.Errorf("status = %d, want 403 for guild member without READ_MESSAGES", rr2.Code)
	}
}

func TestServeFile_LinkedToDM_ParticipantAllowed(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token1 := uploadCreateToken(t, database, "dmalice", 4)
	_ = uploadCreateToken(t, database, "dmbob", 4)

	// Upload a file.
	content := []byte("dm attachment content for participant access test")
	rr := doUpload(t, router, token1, "file", "dm.txt", content)
	if rr.Code != http.StatusCreated {
		t.Fatalf("upload: %d; body: %s", rr.Code, rr.Body.String())
	}
	var resp map[string]any
	_ = json.NewDecoder(rr.Body).Decode(&resp)
	fileID := resp["id"].(string)

	// Create DM channel, add participants, link attachment.
	_, err := database.ExecContext(context.Background(), `INSERT INTO channels (id, name, type) VALUES (1, 'dm-1', 'dm')`)
	if err != nil {
		t.Fatalf("insert channel: %v", err)
	}
	var aliceID, bobID int64
	_ = database.QueryRowContext(context.Background(), `SELECT id FROM users WHERE username = 'dmalice'`).Scan(&aliceID)
	_ = database.QueryRowContext(context.Background(), `SELECT id FROM users WHERE username = 'dmbob'`).Scan(&bobID)
	_, _ = database.ExecContext(context.Background(), `INSERT INTO dm_participants (user_id, channel_id) VALUES (?, 1)`, aliceID)
	_, _ = database.ExecContext(context.Background(), `INSERT INTO dm_participants (user_id, channel_id) VALUES (?, 1)`, bobID)
	_, _ = database.ExecContext(context.Background(), `INSERT INTO messages (id, channel_id, user_id, content) VALUES (1, 1, ?, 'hi')`, aliceID)
	_, _ = database.ExecContext(context.Background(), `UPDATE attachments SET message_id = 1 WHERE id = ?`, fileID)

	// DM participant can access.
	rr2 := doServeFile(t, router, fileID, token1, nil)
	if rr2.Code != http.StatusOK {
		t.Errorf("status = %d, want 200 for DM participant", rr2.Code)
	}
}

func TestServeFile_LinkedToDM_NonParticipantForbidden(t *testing.T) {
	database := newUploadTestDB(t)
	store := newUploadTestStorage(t)
	router := buildUploadRouter(database, store, nil)
	token1 := uploadCreateToken(t, database, "dmowner", 4)
	_ = uploadCreateToken(t, database, "dmpartner", 4)
	outsiderToken := uploadCreateToken(t, database, "dmoutsider", 4)

	// Upload a file.
	content := []byte("dm attachment content for non-participant forbidden test")
	rr := doUpload(t, router, token1, "file", "dmsecret.txt", content)
	if rr.Code != http.StatusCreated {
		t.Fatalf("upload: %d; body: %s", rr.Code, rr.Body.String())
	}
	var resp map[string]any
	_ = json.NewDecoder(rr.Body).Decode(&resp)
	fileID := resp["id"].(string)

	// Create DM channel with two participants (not the outsider).
	_, err := database.ExecContext(context.Background(), `INSERT INTO channels (id, name, type) VALUES (1, 'dm-1', 'dm')`)
	if err != nil {
		t.Fatalf("insert channel: %v", err)
	}
	var ownerID, partnerID int64
	_ = database.QueryRowContext(context.Background(), `SELECT id FROM users WHERE username = 'dmowner'`).Scan(&ownerID)
	_ = database.QueryRowContext(context.Background(), `SELECT id FROM users WHERE username = 'dmpartner'`).Scan(&partnerID)
	_, _ = database.ExecContext(context.Background(), `INSERT INTO dm_participants (user_id, channel_id) VALUES (?, 1)`, ownerID)
	_, _ = database.ExecContext(context.Background(), `INSERT INTO dm_participants (user_id, channel_id) VALUES (?, 1)`, partnerID)
	_, _ = database.ExecContext(context.Background(), `INSERT INTO messages (id, channel_id, user_id, content) VALUES (1, 1, ?, 'hi')`, ownerID)
	_, _ = database.ExecContext(context.Background(), `UPDATE attachments SET message_id = 1 WHERE id = ?`, fileID)

	// Non-participant gets 403.
	rr2 := doServeFile(t, router, fileID, outsiderToken, nil)
	if rr2.Code != http.StatusForbidden {
		t.Errorf("status = %d, want 403 for DM non-participant", rr2.Code)
	}
}