Initial commit

src/Scientific/Quantity.php

@@ -0,0 +1,86 @@
+<?php
+
+namespace Scientific;
+
+use InvalidArgumentException;
+
+abstract class Quantity
+{
+    /*
+     * https://en.wikipedia.org/wiki/Metric_prefix
+     */
+    private const METRIC_PREFIXES = [
+        'yotta' => 'Y',
+        'zetta' => 'Z',
+        'exa'   => 'E',
+        'peta'  => 'P',
+        'tera'  => 'T',
+        'giga'  => 'G',
+        'mega'  => 'M',
+        'kilo'  => 'k',
+        'hecto' => 'h',
+        'deca'  => 'da',
+        'unit'  => '',
+        'deci'  => 'd',
+        'centi' => 'c',
+        'milli' => 'm',
+        'micro' => 'μ',
+        'nano'  => 'n',
+        'pico'  => 'p',
+        'femto' => 'f',
+        'atto'  => 'a',
+        'zepto' => 'z',
+        'yocto' => 'y',
+    ];
+
+    abstract protected function getSymbol(): string;
+
+    abstract protected function getName(): string;
+
+    public function __construct(
+        private Unit $value
+    )
+    {
+    }
+
+    final public static function fromValue(float $value): static
+    {
+        return new static(new Unit($value));
+    }
+
+    final public function getValue(): Unit
+    {
+        return $this->value;
+    }
+
+    final public function format(string $prefix = 'auto'): string
+    {
+        if ($prefix === 'auto') {
+            $prefix = $this->getAppropriatePrefix();
+        } else if (!method_exists($this->value, $prefix)) {
+            throw new InvalidArgumentException('Invalid size: ' . $prefix);
+        }
+
+        $value = $this->value->{$prefix}();
+        $prefix = self::METRIC_PREFIXES[$prefix] ?? '?';
+        $symbol = $this->getSymbol();
+
+        return sprintf('%.3g %s%s', $value, $prefix, $symbol);
+    }
+
+    private function getAppropriatePrefix(): string
+    {
+        foreach (array_keys(self::METRIC_PREFIXES) as $prefix) {
+            $value = $this->value->{$prefix}();
+            if ($value >= 1. && $value < 1000.) {
+                return $prefix;
+            }
+        }
+        return 'unit';
+    }
+
+    public function __toString(): string
+    {
+        return $this->format();
+    }
+}