line_string_test.go

package resample

import (
	"testing"

	"github.com/paulmach/orb"
	"github.com/paulmach/orb/planar"
)

func TestResample(t *testing.T) {
	ls := orb.LineString{}
	Resample(ls, planar.Distance, 10) // should not panic

	ls = append(ls, orb.Point{0, 0})
	Resample(ls, planar.Distance, 10) // should not panic

	ls = append(ls, orb.Point{1.5, 1.5})
	ls = append(ls, orb.Point{2, 2})

	// resample to 0?
	result := Resample(ls, planar.Distance, 0)
	if len(result) != 0 {
		t.Error("down to zero should be empty line")
	}

	// resample to 1
	result = Resample(ls, planar.Distance, 1)
	answer := orb.LineString{{0, 0}}

	if !result.Equal(answer) {
		t.Error("down to 1 should be first point")
	}

	result = Resample(ls, planar.Distance, 2)
	answer = orb.LineString{{0, 0}, {2, 2}}
	if !result.Equal(answer) {
		t.Error("resample downsampling")
	}

	result = Resample(ls, planar.Distance, 5)
	answer = orb.LineString{{0, 0}, {0.5, 0.5}, {1, 1}, {1.5, 1.5}, {2, 2}}
	if !result.Equal(answer) {
		t.Error("resample upsampling")
		t.Log(result)
		t.Log(answer)
	}

	// round off error case, triggered on my laptop
	p1 := orb.LineString{{-88.145243, 42.321059}, {-88.145232, 42.325902}}
	p1 = Resample(p1, planar.Distance, 109)
	if len(p1) != 109 {
		t.Errorf("incorrect length: %v != 109", len(p1))
	}

	// duplicate points
	ls = orb.LineString{{1, 0}, {1, 0}, {1, 0}}
	ls = Resample(ls, planar.Distance, 10)
	if l := len(ls); l != 10 {
		t.Errorf("length incorrect: %d != 10", l)
	}

	expected := orb.Point{1, 0}
	for i := 0; i < len(ls); i++ {
		if !ls[i].Equal(expected) {
			t.Errorf("incorrect point: %v != %v", ls[i], expected)
		}
	}
}

func TestToInterval(t *testing.T) {
	ls := orb.LineString{{0, 0}, {0, 1}, {0, 10}}

	cases := []struct {
		name     string
		distance float64
		line     orb.LineString
		expected orb.LineString
	}{
		{
			name:     "same number of points",
			distance: 5.0,
			expected: orb.LineString{{0, 0}, {0, 5}, {0, 10}},
		},
		{
			name:     "dist less than 0",
			distance: -5.0,
			expected: nil,
		},
		{
			name:     "dist less than 0",
			distance: -5.0,
			expected: nil,
		},
		{
			name:     "return same if short line",
			distance: 5.0,
			line:     orb.LineString{{0, 0}},
			expected: orb.LineString{{0, 0}},
		},
	}

	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			in := ls.Clone()
			if tc.line != nil {
				in = tc.line
			}

			ls := ToInterval(in, planar.Distance, tc.distance)
			if !ls.Equal(tc.expected) {
				t.Errorf("incorrect point: %v != %v", ls, tc.expected)
			}
		})
	}
}

func TestLineStringResampleEdgeCases(t *testing.T) {
	ls := orb.LineString{{0, 0}}

	_, ret := resampleEdgeCases(ls, 10)
	if !ret {
		t.Errorf("should return true")
	}

	// duplicate points
	ls = append(ls, orb.Point{0, 0})
	ls, ret = resampleEdgeCases(ls, 10)
	if !ret {
		t.Errorf("should return true")
	}

	if l := len(ls); l != 10 {
		t.Errorf("should reset to suggested points: %v != 10", l)
	}

	ls, _ = resampleEdgeCases(ls, 5)
	if l := len(ls); l != 5 {
		t.Errorf("should shorten if necessary: %v != 5", l)
	}
}