Grand test fixup (#138)

* start fixing up tests

* fix up tests + automate with drone

* fiddle with linting

* messing about with drone.yml

* some more fiddling

* hmmm

* add cache

* add vendor directory

* verbose

* ci updates

* update some little things

* update sig

vendor/github.com/golang/geo/s2/latlng.go

@@ -0,0 +1,101 @@
+// Copyright 2014 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package s2
+
+import (
+	"fmt"
+	"math"
+
+	"github.com/golang/geo/r3"
+	"github.com/golang/geo/s1"
+)
+
+const (
+	northPoleLat = s1.Angle(math.Pi/2) * s1.Radian
+	southPoleLat = -northPoleLat
+)
+
+// LatLng represents a point on the unit sphere as a pair of angles.
+type LatLng struct {
+	Lat, Lng s1.Angle
+}
+
+// LatLngFromDegrees returns a LatLng for the coordinates given in degrees.
+func LatLngFromDegrees(lat, lng float64) LatLng {
+	return LatLng{s1.Angle(lat) * s1.Degree, s1.Angle(lng) * s1.Degree}
+}
+
+// IsValid returns true iff the LatLng is normalized, with Lat ∈ [-π/2,π/2] and Lng ∈ [-π,π].
+func (ll LatLng) IsValid() bool {
+	return math.Abs(ll.Lat.Radians()) <= math.Pi/2 && math.Abs(ll.Lng.Radians()) <= math.Pi
+}
+
+// Normalized returns the normalized version of the LatLng,
+// with Lat clamped to [-π/2,π/2] and Lng wrapped in [-π,π].
+func (ll LatLng) Normalized() LatLng {
+	lat := ll.Lat
+	if lat > northPoleLat {
+		lat = northPoleLat
+	} else if lat < southPoleLat {
+		lat = southPoleLat
+	}
+	lng := s1.Angle(math.Remainder(ll.Lng.Radians(), 2*math.Pi)) * s1.Radian
+	return LatLng{lat, lng}
+}
+
+func (ll LatLng) String() string { return fmt.Sprintf("[%v, %v]", ll.Lat, ll.Lng) }
+
+// Distance returns the angle between two LatLngs.
+func (ll LatLng) Distance(ll2 LatLng) s1.Angle {
+	// Haversine formula, as used in C++ S2LatLng::GetDistance.
+	lat1, lat2 := ll.Lat.Radians(), ll2.Lat.Radians()
+	lng1, lng2 := ll.Lng.Radians(), ll2.Lng.Radians()
+	dlat := math.Sin(0.5 * (lat2 - lat1))
+	dlng := math.Sin(0.5 * (lng2 - lng1))
+	x := dlat*dlat + dlng*dlng*math.Cos(lat1)*math.Cos(lat2)
+	return s1.Angle(2*math.Atan2(math.Sqrt(x), math.Sqrt(math.Max(0, 1-x)))) * s1.Radian
+}
+
+// NOTE(mikeperrow): The C++ implementation publicly exposes latitude/longitude
+// functions. Let's see if that's really necessary before exposing the same functionality.
+
+func latitude(p Point) s1.Angle {
+	return s1.Angle(math.Atan2(p.Z, math.Sqrt(p.X*p.X+p.Y*p.Y))) * s1.Radian
+}
+
+func longitude(p Point) s1.Angle {
+	return s1.Angle(math.Atan2(p.Y, p.X)) * s1.Radian
+}
+
+// PointFromLatLng returns an Point for the given LatLng.
+// The maximum error in the result is 1.5 * dblEpsilon. (This does not
+// include the error of converting degrees, E5, E6, or E7 into radians.)
+func PointFromLatLng(ll LatLng) Point {
+	phi := ll.Lat.Radians()
+	theta := ll.Lng.Radians()
+	cosphi := math.Cos(phi)
+	return Point{r3.Vector{math.Cos(theta) * cosphi, math.Sin(theta) * cosphi, math.Sin(phi)}}
+}
+
+// LatLngFromPoint returns an LatLng for a given Point.
+func LatLngFromPoint(p Point) LatLng {
+	return LatLng{latitude(p), longitude(p)}
+}
+
+// ApproxEqual reports whether the latitude and longitude of the two LatLngs
+// are the same up to a small tolerance.
+func (ll LatLng) ApproxEqual(other LatLng) bool {
+	return ll.Lat.ApproxEqual(other.Lat) && ll.Lng.ApproxEqual(other.Lng)
+}