package rrd

import "testing"

func f(v float64) *float64 { return &v }

func TestDownsampleNoop(t *testing.T) {
	in := []Point{{T: 1, V: f(1)}, {T: 2, V: f(2)}, {T: 3, V: f(3)}}
	out := downsample(in, 10)
	if len(out) != len(in) {
		t.Fatalf("expected no-op for points <= target, got %d points", len(out))
	}
}

func TestDownsampleAveragesBuckets(t *testing.T) {
	// 10 points, 0..9, bucketed down to 5: expect roughly paired averages.
	in := make([]Point, 10)
	for i := range in {
		in[i] = Point{T: int64(i), V: f(float64(i))}
	}
	out := downsample(in, 5)
	if len(out) != 5 {
		t.Fatalf("expected 5 points, got %d", len(out))
	}
	want := []float64{0.5, 2.5, 4.5, 6.5, 8.5}
	for i, pt := range out {
		if pt.V == nil {
			t.Fatalf("bucket %d: expected a value, got nil", i)
		}
		if *pt.V != want[i] {
			t.Errorf("bucket %d: got %v, want %v", i, *pt.V, want[i])
		}
	}
}

func TestDownsampleTreatsNullsAsZeroInsideNonEmptyBucket(t *testing.T) {
	in := []Point{{T: 1, V: f(2)}, {T: 2, V: nil}, {T: 3, V: f(4)}, {T: 4, V: nil}}
	out := downsample(in, 1)
	if len(out) != 1 {
		t.Fatalf("expected 1 bucket, got %d", len(out))
	}
	if out[0].V == nil || *out[0].V != 1.5 {
		t.Fatalf("expected NULL-as-zero bucket average (1.5), got %v", out[0].V)
	}
}

func TestDownsampleAllNullBucketStaysNull(t *testing.T) {
	in := []Point{{T: 1, V: nil}, {T: 2, V: nil}}
	out := downsample(in, 1)
	if len(out) != 1 {
		t.Fatalf("expected 1 bucket, got %d", len(out))
	}
	if out[0].V != nil {
		t.Fatalf("expected nil for an all-null bucket, got %v", *out[0].V)
	}
}

func TestDownsampleMaxKeepsPeak(t *testing.T) {
	in := []Point{{T: 1, V: f(1)}, {T: 2, V: f(7)}, {T: 3, V: nil}, {T: 4, V: f(3)}}
	out := downsampleMax(in, 1)
	if len(out) != 1 {
		t.Fatalf("expected 1 bucket, got %d", len(out))
	}
	if out[0].V == nil || *out[0].V != 7 {
		t.Fatalf("expected bucket peak 7, got %v", out[0].V)
	}
}