package agent

import (
	"net/http"
	"net/http/httptest"
	"os"
	"path/filepath"
	"strings"
	"sync/atomic"
	"testing"

	"github.com/mhsanaei/3x-ui/v3/internal/config"
)

// V2.0.1 ①: a node missing its sing-box core fetches the pinned
// release build, self-checks it, and only then reports ready. A
// failed fetch installs nothing and backs off instead of hammering
// the release host on every config poll.

// fakeFetchedCore mimics the self-built release binary: it runs,
// and its `version` carries no stamp ("unknown") — the shape that
// makes telemetry fall back to the install-time version record.
const fakeFetchedCore = "#!/bin/sh\necho 'sing-box version unknown'\n"

func fakeCoreServer(t *testing.T, hits *atomic.Int32, status int) *httptest.Server {
	t.Helper()
	asset, err := singboxCoreAssetName()
	if err != nil {
		t.Skipf("no core asset for this arch: %v", err)
	}
	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		hits.Add(1)
		if status != http.StatusOK {
			w.WriteHeader(status)
			return
		}
		if strings.HasSuffix(r.URL.Path, asset) {
			_, _ = w.Write([]byte(fakeFetchedCore))
			return
		}
		http.NotFound(w, r)
	}))
}

func useCoreBase(t *testing.T, url string) {
	t.Helper()
	orig := singboxCoreBaseURL
	singboxCoreBaseURL = url
	t.Cleanup(func() { singboxCoreBaseURL = orig })
}

func TestFetchSingboxCoreInstallsAndSelfChecks(t *testing.T) {
	binDir := t.TempDir()
	t.Setenv("XUI_BIN_FOLDER", binDir)
	var hits atomic.Int32
	srv := fakeCoreServer(t, &hits, http.StatusOK)
	defer srv.Close()
	useCoreBase(t, srv.URL)

	a := &Agent{httpClient: http.DefaultClient}
	if !a.singboxCoreReady() {
		t.Fatal("core not ready after fetch")
	}
	dest := filepath.Join(binDir, singboxBinaryName())
	info, err := os.Stat(dest)
	if err != nil {
		t.Fatalf("core not installed: %v", err)
	}
	if info.Mode()&0o111 == 0 {
		t.Errorf("installed core is not executable: %v", info.Mode())
	}
	if got, ok := a.cachedSingboxVersion(); !ok || got != singboxCoreVersion {
		t.Errorf("reported core version = %q (ok %v), want %q (from the version record)", got, ok, singboxCoreVersion)
	}
	if config.GetBinFolderPath() != binDir {
		t.Fatalf("bin folder override not in effect")
	}
	// Second call: binary present, no further download.
	if !a.singboxCoreReady() || hits.Load() != 1 {
		t.Errorf("ready check re-downloaded: hits = %d", hits.Load())
	}
}

func TestFetchSingboxCoreFailureKeepsNothingAndBacksOff(t *testing.T) {
	binDir := t.TempDir()
	t.Setenv("XUI_BIN_FOLDER", binDir)
	var hits atomic.Int32
	srv := fakeCoreServer(t, &hits, http.StatusBadGateway)
	defer srv.Close()
	useCoreBase(t, srv.URL)

	a := &Agent{httpClient: http.DefaultClient}
	if a.singboxCoreReady() {
		t.Fatal("core reported ready after a failed fetch")
	}
	if _, err := os.Stat(filepath.Join(binDir, singboxBinaryName())); !os.IsNotExist(err) {
		t.Errorf("failed fetch left a core binary behind: %v", err)
	}
	// Backoff: an immediate retry must not hit the server again.
	if err := a.fetchSingboxCoreThrottled(); err == nil {
		t.Fatal("throttled retry returned no error")
	}
	if hits.Load() != 1 {
		t.Errorf("backoff violated: server hits = %d, want 1", hits.Load())
	}
	// And the switch gate stays closed: ready remains false.
	if a.singboxCoreReady() {
		t.Error("core became ready during backoff")
	}
}

func TestFetchSingboxCoreRejectsBrokenDownload(t *testing.T) {
	binDir := t.TempDir()
	t.Setenv("XUI_BIN_FOLDER", binDir)
	var hits atomic.Int32
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		hits.Add(1)
		_, _ = w.Write([]byte("this is not a binary at all"))
	}))
	defer srv.Close()
	useCoreBase(t, srv.URL)

	a := &Agent{httpClient: http.DefaultClient}
	if err := a.fetchSingboxCore(); err == nil {
		t.Fatal("broken download passed the self-check")
	}
	if _, err := os.Stat(filepath.Join(binDir, singboxBinaryName())); !os.IsNotExist(err) {
		t.Errorf("broken download was installed: %v", err)
	}
}