package analytics

import "testing"

func TestTopKExactBelowCapAndBoundedAbove(t *testing.T) {
	k := NewTopK()
	for i := 0; i < 100; i++ {
		k.Add("/p"+itoa(i), int64(i+1))
	}
	f := k.Fold()
	if len(f) != 100 || f["/p99"] != 100 || k.Approximate() {
		t.Fatalf("below cap must be exact: len=%d p99=%d approx=%v", len(f), f["/p99"], k.Approximate())
	}
	for i := 0; i < 2000; i++ {
		k.Add("/q"+itoa(i), 1)
	}
	f = k.Fold()
	if len(f) > TopKSize+1 || !k.Approximate() || f[OtherKey] == 0 {
		t.Fatalf("above cap: len=%d approx=%v other=%d", len(f), k.Approximate(), f[OtherKey])
	}
	// Total mass is conserved between counters and _other.
	var total int64
	for _, v := range f {
		total += v
	}
	if total != 100*101/2+2000 {
		t.Fatalf("mass %d", total)
	}
	// A heavy hitter survives.
	if f["/p99"] < 100-2000/TopKSize {
		t.Fatalf("heavy hitter undercounted: %d", f["/p99"])
	}
}

func TestTopKMergeRefolds(t *testing.T) {
	a, b := NewTopK(), NewTopK()
	for i := 0; i < 400; i++ {
		a.Add("/a"+itoa(i), 2)
		b.Add("/b"+itoa(i), 3)
	}
	a.Merge(b)
	f := a.Fold()
	if len(f) > TopKSize+1 || f[OtherKey] == 0 {
		t.Fatalf("merged 800 keys must fold to ≤501: %d", len(f))
	}
	r := TopKFrom(f)
	if r.other != f[OtherKey] || len(r.counts) != len(f)-1 {
		t.Fatal("TopKFrom must invert Fold")
	}
	long := NewTopK()
	long.Add(string(make([]byte, 300)), 1)
	for key := range long.Fold() {
		if len(key) > MaxKeyLen {
			t.Fatal("keys must be capped at 256 bytes")
		}
	}
}