package helper

import (
	"math"
	"testing"
)

func TestClampRGB(t *testing.T) {
	t.Run("values in legal ranges should be unmodified", func(t *testing.T) {
		const steps = 8

		for rI := range steps {
			for gI := range steps {
				for bI := range steps {
					want := [3]float64{
						float64(rI) * (1 / (steps - 1)),
						float64(gI) * (1 / (steps - 1)),
						float64(bI) * (1 / (steps - 1)),
					}

					if got := collect3(ClampRGB(want[0], want[1], want[2])); got != want {
						t.Errorf("Clamp(%v) = %v, expected values to be unmodified", want, got)
						return
					}
				}
			}
		}
	})

	tests := []struct {
		name   string
		values [3]float64
		want   [3]float64
	}{

		{
			// any component being infinity should result in white.
			name:   "+inf",
			values: [3]float64{-1, .5, math.Inf(1)},
			want:   [3]float64{1, 1, 1},
		}, {
			// ... except the case where any other component was NaN or -infinity.
			name:   "+inf, -inf, NaN",
			values: [3]float64{math.Inf(-1), math.NaN(), math.Inf(1)},
			want:   [3]float64{0, 0, 1},
		}, {
			// colors that are too bright should be scaled back to the legal range, and then
			// interpolate to white by 1-1/max_value.
			name:   "normalize over-bright colours and fade them to white",
			values: [3]float64{1, 2, 3},
			want:   [3]float64{1./3*(1./3) + (1 - 1./3), 2./3*(1./3) + (1 - 1./3), 1}, // note that
		}, {
			name:   "negative values should be clamped to 0",
			values: [3]float64{-1, math.Inf(-1), .5},
			want:   [3]float64{0, 0, .5},
		}, {
			name:   "except where the logic for over-bright colors would bring them back to the legal range",
			values: [3]float64{-1, 0, 3},
			want:   [3]float64{-1./3*(1./3) + (1 - 1./3), 1 - 1./3, 1},
		},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			for _, order := range permuteOrder3 {
				values := permute3(tt.values, order)
				want := permute3(tt.want, order)

				if got := collect3(ClampRGB(values[0], values[1], values[2])); !EqFloat64SliceFuzzy(got[:], want[:]) {
					t.Errorf("ClampRGB(%v) = %v, want %v", values, got, want)
					return
				}
			}
		})
	}
}