UnitParser.java

package org.andork.unit;

import java.text.CharacterIterator;
import java.util.function.Function;

import org.andork.func.CharPredicate;

public class UnitParser<T extends UnitType<T>> implements Function<CharacterIterator, Unit<T>> {
	T unitType;
	CharPredicate isUnitStartChar;
	CharPredicate isUnitChar;
	Function<String, Unit<T>> unitLookup;

	public UnitParser(T unitType, CharPredicate isUnitStartChar, CharPredicate isUnitChar,
			Function<String, Unit<T>> unitLookup) {
		super();
		this.unitType = unitType;
		this.isUnitStartChar = isUnitStartChar;
		this.isUnitChar = isUnitChar;
		this.unitLookup = unitLookup;
	}

	@Override
	public Unit<T> apply(CharacterIterator t) {
		char c = t.current();

		while (Character.isWhitespace(c)) {
			c = t.next();
		}

		if (!isUnitStartChar.test(c)) {
			return null;
		}

		StringBuilder sb = new StringBuilder();

		while (isUnitStartChar.test(c)) {
			if (sb.length() > 0) {
				sb.append(' ');
			}

			while (isUnitChar.test(c)) {
				sb.append(c);
				c = t.next();
			}

			while (Character.isWhitespace(c)) {
				c = t.next();
			}
		}

		Unit<T> result = unitLookup.apply(sb.toString());
		if (result == null) {
			throw new IllegalArgumentException("Unrecognized unit: " + sb.toString());
		}
		return result;
	}
}