package accounting

import (
	"testing"
	"time"
)

// Two control planes each allowing a key six of its ten a minute: once each
// has heard the other's count, neither allows another.
func TestALimitIsTheClustersOnceTheCountsAreShared(t *testing.T) {
	now := time.Date(2026, 11, 1, 12, 0, 10, 0, time.UTC)
	a, b := NewLimiter(), NewLimiter()
	a.now, b.now = func() time.Time { return now }, func() time.Time { return now }
	for range 6 {
		if !a.Allow("k", 10, 1) || !b.Allow("k", 10, 1) {
			t.Fatal("refused within the limit")
		}
	}
	a.SetOthers(b.Counts())
	b.SetOthers(a.Counts())
	if a.Allow("k", 10, 1) || b.Allow("k", 10, 1) {
		t.Error("twelve of ten allowed once both knew")
	}
	// Reporting the same counts again changes nothing: they are absolute.
	a.SetOthers(b.Counts())
	if got := a.Rate("k"); got != 12 {
		t.Errorf("rate %v after the same counts twice", got)
	}
	// What the others counted is never charged back to them.
	if c := a.Counts(); c.Current["k"] != 6 {
		t.Errorf("own count %d", c.Current["k"])
	}
}

// A key only the others have used is limited here from its first request,
// and their counts move into the previous minute with the clock.
func TestOthersCountsFollowTheMinute(t *testing.T) {
	now := time.Date(2026, 11, 1, 12, 0, 50, 0, time.UTC)
	a, b := NewLimiter(), NewLimiter()
	a.now, b.now = func() time.Time { return now }, func() time.Time { return now }
	for range 10 {
		b.Allow("k", 10, 1)
	}
	a.SetOthers(b.Counts())
	if a.Allow("k", 10, 1) {
		t.Error("a key the cluster has used up was allowed where it had not been seen")
	}
	now = now.Add(20 * time.Second) // 12:01:10, a sixth into the next minute
	if got := a.Rate("k"); got < 8 || got > 8.5 {
		t.Errorf("rate %v: the others' last minute should weigh five sixths", got)
	}
	// Counts of a minute ago, sent late, land in the previous minute.
	old := b.Counts()
	old.Minute = now.Truncate(time.Minute).Add(-time.Minute)
	old.Current, old.Previous = map[string]int64{"k": 3}, nil
	a.SetOthers(old)
	if got := a.Rate("k"); got < 2 || got > 3 {
		t.Errorf("rate %v from late counts", got)
	}
}

func TestRatesAddAlignsMinutes(t *testing.T) {
	m := time.Date(2026, 11, 1, 12, 1, 0, 0, time.UTC)
	sum := NewRates(m)
	sum.Add(Rates{Requests: Counts{Minute: m, Current: map[string]int64{"k": 2}, Previous: map[string]int64{"k": 1}}})
	sum.Add(Rates{Requests: Counts{Minute: m.Add(-time.Minute), Current: map[string]int64{"k": 5}}})
	sum.Add(Rates{Requests: Counts{Minute: m.Add(-2 * time.Minute), Current: map[string]int64{"k": 100}}})
	if sum.Requests.Current["k"] != 2 || sum.Requests.Previous["k"] != 6 {
		t.Errorf("sum %+v", sum.Requests)
	}
}