PHPCoord\IrishGridPoint

Complexity

Total Complexity

6

Size/Duplication

Total Lines	71
Duplicated Lines	0 %

Test Coverage

Coverage

93.55%

Importance

Changes	1
Bugs	0	Features	0

4 Methods

Rating	Name	Duplication	Size	Complexity
A	gridReference()	0	23	2
A	fromGridReference()	0	19	2
A	__construct()	0	3	1
A	asGridReference()	0	3	1

<?php
/**
 * PHPCoord.
 *
 * @author Doug Wright
 */
declare(strict_types=1);

namespace PHPCoord;

use DateTimeInterface;
use function floor;
use function implode;
use PHPCoord\CoordinateReferenceSystem\Projected;
use PHPCoord\Exception\InvalidCoordinateException;
use PHPCoord\UnitOfMeasure\Length\Length;
use PHPCoord\UnitOfMeasure\Length\Metre;
use function str_pad;
use function strlen;
use function strpos;
use function substr;

/**
 * N.B. This is the older 1975 system, not the current ITM system for which @see IrishTransverseMercatorPoint.
 */
class IrishGridPoint extends ProjectedPoint
{
    private const GRID_LETTERS = 'VWXYZQRSTULMNOPFGHJKABCDE';

    public function __construct(Length $easting, Length $northing, ?DateTimeInterface $epoch = null)
    {
        parent::__construct($easting, $northing, null, null, Projected::fromSRID(Projected::EPSG_TM75_IRISH_GRID), $epoch);
    }

    /**
     * @param string Irish grid reference (e.g. "T514131")
     */
    public static function fromGridReference(string $reference, ?DateTimeInterface $epoch = null): self
    {
        if (strlen($reference) % 2 === 0) {
            throw new InvalidCoordinateException('Grid ref must be an even number of characters');
        }

        //Letter is 100km grid sq, origin at 0,0 of this square
        $minorEasting = strpos(static::GRID_LETTERS, $reference[0]) % 5 * 100000;
        $minorNorthing = (floor(strpos(static::GRID_LETTERS, $reference[0]) / 5)) * 100000;

        //numbers are a division of that square into smaller and smaller pieces
        $numericPortion = substr($reference, 1);
        $numericPortionSize = strlen($numericPortion) / 2;
        $gridSizeInMetres = 1 * (10 ** (5 - $numericPortionSize));

        $easting = $minorEasting + (substr($numericPortion, 0, $numericPortionSize) * $gridSizeInMetres);
        $northing = $minorNorthing + (substr($numericPortion, -$numericPortionSize, $numericPortionSize) * $gridSizeInMetres);

        return new static(new Metre($easting), new Metre($northing), $epoch);
    }

    /**
     * Grid reference without spaces. e.g. T514131.
     */
    public function asGridReference(int $length): string
    {
        return implode('', $this->gridReference($length));
    }

    /**
     * Convert this grid reference into a grid reference string of a
     * given length (2, 4, 6, 8 or 10) including the character
     * designation for the 100km square. e.g. T514131.
     *
     * @return string
     */
    protected function gridReference(int $length): array
    {
        if ($length % 2 !== 0) {
            throw new InvalidCoordinateException('Chosen length must be an even number');
        }

        $halfLength = $length / 2;

        $x = $this->easting->asMetres()->getValue();
        $y = $this->northing->asMetres()->getValue();
        $easting = str_pad((string) $x, 6, '0', STR_PAD_LEFT);
        $northing = str_pad((string) $y, 6, '0', STR_PAD_LEFT);

        //second (minor) letter is 100km grid sq, origin at 0,0 of this square
        $minorSquaresEast = $easting[0] % 5;
        $minorSquaresNorth = $northing[0] % 5;
        $minorLetterIndex = (5 * $minorSquaresNorth + $minorSquaresEast);
        $minorLetter = substr(self::GRID_LETTERS, $minorLetterIndex, 1);

        return [
            $minorLetter,
            substr($easting, 1, $halfLength),
            substr($northing, 1, $halfLength),
        ];
    }
}