package utils

import (
	"math"
	"testing"
)

func assertVectorsEqual(t *testing.T, got, want []float64) {
	t.Helper()
	if len(got) != len(want) {
		t.Fatalf("length %d, want %d", len(got), len(want))
	}
	for i := range want {
		if math.Abs(got[i]-want[i]) > 1e-9 {
			t.Fatalf("index %d = %v, want %v", i, got, want)
		}
	}
}

func TestAverageVector(t *testing.T) {
	tests := []struct {
		name string
		in   [][]float64
		want []float64
	}{
		{name: "empty input", in: nil, want: nil},
		{name: "empty slice", in: [][]float64{}, want: nil},
		{name: "all empty vectors", in: [][]float64{{}, {}, {}}, want: nil},
		{name: "single vector", in: [][]float64{{0.4, -0.2}}, want: []float64{0.4, -0.2}},
		{name: "multiple vectors", in: [][]float64{{0.1, 0.2}, {0.3, 0.4}}, want: []float64{0.2, 0.3}},
		{name: "first vector empty", in: [][]float64{{}, {0.1, 0.2}, {0.3, 0.4}}, want: []float64{0.2, 0.3}},
		{name: "trailing empty vectors", in: [][]float64{{0.1, 0.2}, {}, {0.3, 0.4}}, want: []float64{0.2, 0.3}},
		{name: "only first valid", in: [][]float64{{}, {}, {0.1, 0.2}}, want: []float64{0.1, 0.2}},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			got := AverageVector(tt.in)
			if tt.want == nil {
				if got != nil {
					t.Fatalf("AverageVector(%v) = %v, want nil", tt.in, got)
				}
				return
			}
			assertVectorsEqual(t, got, tt.want)
		})
	}
}