package agent

import (
	"net/http"
	"net/http/httptest"
	"strings"
	"sync/atomic"
	"testing"
)

// V2.0.1 ① integration: the master serves a sing-box config but the
// node has no core and the fetch fails — the switch must NOT latch
// (xray stays the runtime and the next poll retries), because the
// B5 switch retires xray the moment it engages.
func TestSwitchGateStaysOpenWhenCoreFetchFails(t *testing.T) {
	binDir := t.TempDir()
	t.Setenv("XUI_BIN_FOLDER", binDir)

	var hits atomic.Int32
	coreSrv := fakeCoreServer(t, &hits, http.StatusBadGateway)
	defer coreSrv.Close()
	useCoreBase(t, coreSrv.URL)

	master := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if strings.HasSuffix(r.URL.Path, "/config") {
			w.Header().Set("Content-Type", "application/json")
			_, _ = w.Write([]byte(`{"config_hash":"x1","singbox_config_hash":"sb1",` +
				`"singbox_config":{"inbounds":[]}}`))
			return
		}
		http.NotFound(w, r)
	}))
	defer master.Close()

	a := &Agent{
		config:     &Config{MasterURL: master.URL, Token: "tok", NodeName: "n"},
		httpClient: http.DefaultClient,
		probes:     newProbeRunner(),
	}
	if err := a.fetchAndApplyConfig(); err != nil {
		t.Fatalf("fetchAndApplyConfig: %v", err)
	}
	if a.sbSwitched {
		t.Fatal("switch latched although the sing-box core could not be fetched")
	}
	if hits.Load() != 1 {
		t.Errorf("core fetch attempts = %d, want exactly 1", hits.Load())
	}
	// A second poll inside the backoff window must not re-download.
	if err := a.fetchAndApplyConfig(); err != nil {
		t.Fatalf("second fetchAndApplyConfig: %v", err)
	}
	if hits.Load() != 1 {
		t.Errorf("backoff violated on the config path: hits = %d", hits.Load())
	}
	if a.sbSwitched {
		t.Fatal("switch latched during backoff")
	}
}