package metrics

import (
	"bytes"
	"errors"
	"net/http/httptest"
	"testing"
)

func TestCapacityPressureEventsWriteTextAndReset(t *testing.T) {
	t.Parallel()
	m := NewMetrics()
	if got := m.GetStats().CapacityPressureEvents; got != 0 {
		t.Fatalf("initial CapacityPressureEvents=%d, want 0", got)
	}

	NoteSoftEviction(m, "memory", 0)
	if got := m.GetStats().CapacityPressureEvents; got != 0 {
		t.Fatalf("zero-byte eviction counted: %d", got)
	}

	NoteSoftEviction(m, "memory", 128)
	st := m.GetStats()
	if st.CapacityPressureEvents != 1 {
		t.Fatalf("after memory eviction, CapacityPressureEvents=%d, want 1", st.CapacityPressureEvents)
	}
	if st.Evictions != 1 {
		t.Fatalf("after memory eviction, Evictions=%d, want 1 (existing counter kept)", st.Evictions)
	}

	NoteSoftEviction(m, "disk", 64)
	NoteNoSpace(m, errors.New("no space left on device"))
	st = m.GetStats()
	if st.CapacityPressureEvents != 3 {
		t.Fatalf("after disk eviction + ENOSPC, CapacityPressureEvents=%d, want 3", st.CapacityPressureEvents)
	}
	if st.Evictions != 2 {
		t.Fatalf("ENOSPC must not increment evictions; Evictions=%d, want 2", st.Evictions)
	}

	rec := httptest.NewRecorder()
	WriteText(rec, st)
	body := rec.Body.Bytes()
	if !bytes.Contains(body, []byte("capacity_pressure_events 3")) {
		t.Errorf("WriteText missing capacity_pressure_events 3: %q", rec.Body.String())
	}
	if !bytes.Contains(body, []byte("evictions 2")) {
		t.Errorf("WriteText missing evictions 2: %q", rec.Body.String())
	}

	m.Reset()
	st = m.GetStats()
	if st.CapacityPressureEvents != 0 || st.Evictions != 0 {
		t.Errorf("after Reset, CapacityPressureEvents=%d Evictions=%d, want 0", st.CapacityPressureEvents, st.Evictions)
	}
}

func TestNoteSoftEvictionNilMetrics(t *testing.T) {
	t.Parallel()
	// Must not panic when metrics are not wired (unit tests / early init).
	NoteSoftEviction(nil, "memory", 10)
	NoteNoSpace(nil, errors.New("ENOSPC"))
}