photoprism/pkg/pluscode/pluscode.go

/*

Package pluscode provides an abstraction for Google's Open Location Code package.

Copyright (c) 2018 - 2020 Michael Mayer <hello@photoprism.org>

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as published
    by the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.

    PhotoPrism™ is a registered trademark of Michael Mayer.  You may use it as required
    to describe our software, run your own server, for educational purposes, but not for
    offering commercial goods, products, or services without prior written permission.
    In other words, please ask.

Feel free to send an e-mail to hello@photoprism.org if you have questions,
want to support our work, or just want to say hello.

Additional information can be found in our Developer Guide:
https://docs.photoprism.org/developer-guide/

*/
package pluscode

import (
	"fmt"

	olc "github.com/google/open-location-code/go"
	"github.com/photoprism/photoprism/pkg/s2"
)

var defaultLen = 8

// Encode returns the plus code for the given coordinates using the default length.
func Encode(lat, lng float64) string {
	result, _ := EncodeLength(lat, lng, defaultLen)

	return result
}

// EncodeLength returns the plus code for the given coordinates.
func EncodeLength(lat, lng float64, length int) (plusCode string, err error) {
	if lat < -90 || lat > 90 {
		return "", fmt.Errorf("latitude out of range (%f)", lat)
	}

	if lng < -180 || lng > 180 {
		return "", fmt.Errorf("longitude out of range (%f)", lng)
	}

	return olc.Encode(lat, lng, length), nil
}

// LatLng returns the coordinates for a plus code token.
func LatLng(token string) (lat, lng float64) {
	if token == "" || token == "-" {
		return lat, lng
	}

	c, err := olc.Decode(token)

	if err != nil {
		return lat, lng
	}

	lat, lng = c.Center()

	return lat, lng
}

// S2 returns the S2 cell token for the plus code using the default cell level.
func S2(plusCode string) string {
	lat, lng := LatLng(plusCode)

	s2Token := s2.Token(lat, lng)

	return s2Token
}