/**
 * Copyright (c) 2005, 2011, Werner Keil, JScience and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *    Werner Keil, Jean-Marie Dautelle - initial API and implementation
 */
package org.eclipse.uomo.units.impl.system;

import static org.eclipse.uomo.units.AbstractUnit.ONE;

import java.math.BigInteger;
import org.eclipse.uomo.units.Messages;
import org.eclipse.uomo.units.impl.AlternateUnit;
import org.eclipse.uomo.units.impl.BaseUnit;
import org.eclipse.uomo.units.impl.ProductUnit;
import org.eclipse.uomo.units.impl.TransformedUnit;
import org.eclipse.uomo.units.impl.converter.RationalConverter;
import javax.measure.spi.SystemOfUnits;
import javax.measure.Unit;
import javax.measure.quantity.*;

/**
 * <p>
 * This class contains SI (Système International d'Unités) base units, and
 * derived units.
 * </p>
 * 
 * <p>
 * It also defines an inner class for the 20 SI prefixes used to form decimal
 * multiples and submultiples of SI units. For example:[code] import static
 * org.eclipse.uomo.units.SI.*; // Static import. ... Unit<Pressure> HECTOPASCAL
 * = HECTO(PASCAL); Unit<Length> KILOMETRE = KILO(METRE); [/code]
 * </p>
 * 
 * @noextend This class is not intended to be extended by clients.
 * 
 * @author <a href="mailto:jean-marie@dautelle.com">Jean-Marie Dautelle</a>
 * @author <a href="mailto:units@catmedia.us">Werner Keil</a>
 * @version 1.32 ($Revision: 232 $), $Date: 2011-09-11 14:50:08 +0200 $
 * @see <a
 *      href="http://en.wikipedia.org/wiki/International_System_of_Units">Wikipedia:
 *      International System of Units</a>
 */
public final class SI extends AbstractSystemOfUnits {

	/**
	 * The singleton instance of {@code SI}.
	 */
	private static final SI INSTANCE = new SI();

	/**
	 * Returns the singleton instance of this class.
	 * 
	 * @return the SI (metric) system instance.
	 */
	public static final SystemOfUnits getInstance() {
		return INSTANCE;
	}

	// //////////////
	// BASE UNITS //
	// //////////////
	/**
	 * The base unit for electric current quantities (<code>A</code>). The
	 * Ampere is that constant current which, if maintained in two straight
	 * parallel conductors of infinite length, of negligible circular
	 * cross-section, and placed 1 meter apart in vacuum, would produce between
	 * these conductors a force equal to 2 * 10-7 newton per meter of length. It
	 * is named after the French physicist Andre Ampere (1775-1836).
	 */
	public static final Unit<ElectricCurrent> AMPERE = addUnit(new BaseUnit<ElectricCurrent>(
			Messages.SI_A));

	/**
	 * The base unit for luminous intensity quantities (<code>cd</code>). The
	 * candela is the luminous intensity, in a given direction, of a source that
	 * emits monochromatic radiation of frequency 540 * 1012 hertz and that has
	 * a radiant intensity in that direction of 1/683 watt per steradian
	 * 
	 * @see <a href="http://en.wikipedia.org/wiki/Candela"> Wikipedia:
	 *      Candela</a>
	 */
	public static final Unit<LuminousIntensity> CANDELA = addUnit(new BaseUnit<LuminousIntensity>(
			Messages.SI_cd));

	/**
	 * The base unit for thermodynamic temperature quantities (<code>K</code>).
	 * The kelvin is the 1/273.16th of the thermodynamic temperature of the
	 * triple point of water. It is named after the Scottish mathematician and
	 * physicist William Thomson 1st Lord Kelvin (1824-1907)
	 */
	public static final Unit<Temperature> KELVIN = addUnit(new BaseUnit<Temperature>(
			Messages.SI_K));

	/**
	 * The base unit for mass quantities (<code>kg</code>). It is the only SI
	 * unit with a prefix as part of its name and symbol. The kilogram is equal
	 * to the mass of an international prototype in the form of a
	 * platinum-iridium cylinder kept at Sevres in France.
	 * 
	 * @see #GRAM
	 */
	public static final Unit<Mass> KILOGRAM = addUnit(new BaseUnit<Mass>(
			Messages.SI_kg, Messages.SI_kg_name));

	/**
	 * The base unit for length quantities (<code>m</code>). One metre was
	 * redefined in 1983 as the distance traveled by light in a vacuum in
	 * 1/299,792,458 of a second.
	 */
	public static final Unit<Length> METRE = addUnit(new BaseUnit<Length>(
			Messages.SI_m, Messages.SI_m_name));

	/**
	 * The base unit for amount of substance quantities (<code>mol</code>). The
	 * mole is the amount of substance of a system which contains as many
	 * elementary entities as there are atoms in 0.012 kilogram of carbon 12.
	 */
	public static final Unit<AmountOfSubstance> MOLE = addUnit(new BaseUnit<AmountOfSubstance>(
			Messages.SI_mol));

	/**
	 * The base unit for time quantities (<code>s</code>). It is defined as the
	 * duration of 9,192,631,770 cycles of radiation corresponding to the
	 * transition between two hyperfine levels of the ground state of cesium
	 * (1967 Standard).
	 * 
	 * FIXME this is not aligned with TimeUnit from ICU4J due to TimeUnit so far cannot be extended 
	 */
	public static final Unit<Time> SECOND = addUnit(new BaseUnit<Time>(
			Messages.SI_s));
	// //////////////////////////////
	// SI DERIVED ALTERNATE UNITS //
	// //////////////////////////////

	/**
	 * The unit for magnetomotive force (<code>At</code>).
	 */
	public static final Unit<MagnetomotiveForce> AMPERE_TURN = addUnit(new AlternateUnit<MagnetomotiveForce>(
			Messages.SI_At, (AbstractUnit<?>) SI.AMPERE));

	/**
	 * The derived unit for mass quantities (<code>g</code>). The base unit for
	 * mass quantity is {@link #KILOGRAM}.
	 */
	public static final Unit<Mass> GRAM = KILOGRAM.divide(1000);

	/**
	 * The unit for plane angle quantities (<code>rad</code>). One radian is the
	 * angle between two radii of a circle such that the length of the arc
	 * between them is equal to the radius.
	 */
	public static final Unit<Angle> RADIAN = addUnit(new AlternateUnit<Angle>(
			Messages.SI_rad, AbstractUnit.ONE));

	/**
	 * The unit for solid angle quantities (<code>sr</code>). One steradian is
	 * the solid angle subtended at the center of a sphere by an area on the
	 * surface of the sphere that is equal to the radius squared. The total
	 * solid angle of a sphere is 4*Pi steradians.
	 */
	public static final Unit<SolidAngle> STERADIAN = addUnit(new AlternateUnit<SolidAngle>(
			Messages.SI_sr, AbstractUnit.ONE));

	/**
	 * The derived unit for frequency (<code>Hz</code>). A unit of frequency
	 * equal to one cycle per second. After Heinrich Rudolf Hertz (1857-1894),
	 * German physicist who was the first to produce radio waves artificially.
	 */
	public static final Unit<Frequency> HERTZ = addUnit(new AlternateUnit<Frequency>(
			Messages.SI_Hz,
			(AbstractUnit<?>) AbstractUnit.ONE.divide(SECOND)));

	/**
	 * The derived unit for force (<code>N</code>). One newton is the force
	 * required to give a mass of 1 kilogram an Force of 1 metre per second per
	 * second. It is named after the English mathematician and physicist Sir
	 * Isaac Newton (1642-1727).
	 */
	public static final Unit<Force> NEWTON = addUnit(new AlternateUnit<Force>(
			Messages.SI_N, (AbstractUnit<?>) METRE.multiply(KILOGRAM)
					.divide(SECOND.pow(2))));

	/**
	 * The derived unit for pressure, stress (<code>Pa</code>). One pascal is
	 * equal to one newton per square meter. It is named after the French
	 * philosopher and mathematician Blaise Pascal (1623-1662).
	 */
	public static final Unit<Pressure> PASCAL = addUnit(new AlternateUnit<Pressure>(
			Messages.SI_Pa, (AbstractUnit<?>) NEWTON.divide(METRE.pow(2))));

	/**
	 * The derived unit for energy, work, quantity of heat (<code>J</code>). One
	 * joule is the amount of work done when an applied force of 1 newton moves
	 * through a distance of 1 metre in the direction of the force. It is named
	 * after the English physicist James Prescott Joule (1818-1889).
	 */
	public static final Unit<Energy> JOULE = addUnit(new AlternateUnit<Energy>(
			Messages.SI_J, (AbstractUnit<?>) NEWTON.multiply(METRE)));

	/**
	 * The derived unit for power, radiant, flux (<code>W</code>). One watt is
	 * equal to one joule per second. It is named after the British scientist
	 * James Watt (1736-1819).
	 */
	public static final Unit<Power> WATT = addUnit(new AlternateUnit<Power>(
			Messages.SI_W, (AbstractUnit<?>) JOULE.divide(SECOND)));

	/**
	 * The derived unit for electric charge, quantity of electricity (
	 * <code>C</code>). One Coulomb is equal to the quantity of charge
	 * transferred in one second by a steady current of one ampere. It is named
	 * after the French physicist Charles Augustin de Coulomb (1736-1806).
	 */
	public static final Unit<ElectricCharge> COULOMB = addUnit(new AlternateUnit<ElectricCharge>(
			Messages.SI_C, (AbstractUnit<?>) SECOND.multiply(AMPERE)));

	/**
	 * The derived unit for electric potential difference, electromotive force (
	 * <code>V</code>). One Volt is equal to the difference of electric
	 * potential between two points on a conducting wire carrying a constant
	 * current of one ampere when the power dissipated between the points is one
	 * watt. It is named after the Italian physicist Count Alessandro Volta
	 * (1745-1827).
	 */
	public static final Unit<ElectricPotential> VOLT = addUnit(new AlternateUnit<ElectricPotential>(
			Messages.SI_V, (AbstractUnit<?>) WATT.divide(AMPERE)));

	/**
	 * The derived unit for capacitance (<code>F</code>). One Farad is equal to
	 * the capacitance of a capacitor having an equal and opposite charge of 1
	 * coulomb on each plate and a potential difference of 1 volt between the
	 * plates. It is named after the British physicist and chemist Michael
	 * Faraday (1791-1867).
	 */
	public static final Unit<ElectricCapacitance> FARAD = addUnit(new AlternateUnit<ElectricCapacitance>(
			Messages.SI_F, (AbstractUnit<?>) COULOMB.divide(VOLT)));

	/**
	 * The derived unit for electric resistance (<code>Ohm</code>). One Ohm is
	 * equal to the resistance of a conductor in which a current of one ampere
	 * is produced by a potential of one volt across its terminals. It is named
	 * after the German physicist Georg Simon Ohm (1789-1854).
	 */
	public static final Unit<ElectricResistance> OHM = addUnit(new AlternateUnit<ElectricResistance>(
			Messages.SI_OhmS, (AbstractUnit<?>) VOLT.divide(AMPERE)));

	/**
	 * The derived unit for electric conductance (<code>S</code>). One Siemens
	 * is equal to one ampere per volt. It is named after the German engineer
	 * Ernst Werner von Siemens (1816-1892).
	 */
	public static final Unit<ElectricConductance> SIEMENS = addUnit(new AlternateUnit<ElectricConductance>(
			Messages.SI_S, (AbstractUnit<?>) AMPERE.divide(VOLT)));

	/**
	 * The derived unit for magnetic flux (<code>Wb</code>). One Weber is equal
	 * to the magnetic flux that in linking a circuit of one turn produces in it
	 * an electromotive force of one volt as it is uniformly reduced to zero
	 * within one second. It is named after the German physicist Wilhelm Eduard
	 * Weber (1804-1891).
	 */
	public static final Unit<MagneticFlux> WEBER = addUnit(new AlternateUnit<MagneticFlux>(
			Messages.SI_Wb, (AbstractUnit<?>) VOLT.multiply(SECOND)));

	/**
	 * The derived unit for magnetic flux density (<code>T</code>). One Tesla is
	 * equal equal to one weber per square metre. It is named after the
	 * Serbian-born American electrical engineer and physicist Nikola Tesla
	 * (1856-1943).
	 */
	public static final Unit<MagneticFluxDensity> TESLA = addUnit(new AlternateUnit<MagneticFluxDensity>(
			Messages.SI_T, (AbstractUnit<?>) WEBER.divide(METRE.pow(2))));

	/**
	 * The derived unit for inductance (<code>H</code>). One Henry is equal to
	 * the inductance for which an induced electromotive force of one volt is
	 * produced when the current is varied at the rate of one ampere per second.
	 * It is named after the American physicist Joseph Henry (1791-1878).
	 */
	public static final Unit<ElectricInductance> HENRY = addUnit(new AlternateUnit<ElectricInductance>(
			Messages.SI_H, (AbstractUnit<?>) WEBER.divide(AMPERE)));

	/**
	 * The derived unit for Celsius temperature (<code>Cel</code>). This is a
	 * unit of temperature such as the freezing point of water (at one
	 * atmosphere of pressure) is 0 Cel, while the boiling point is 100 Cel.
	 */
	public static final Unit<Temperature> CELSIUS = addUnit(KELVIN.add(273.15));

	/**
	 * The derived unit for luminous flux (<code>lm</code>). One Lumen is equal
	 * to the amount of light given out through a solid angle by a source of one
	 * candela intensity radiating equally in all directions.
	 */
	public static final Unit<LuminousFlux> LUMEN = addUnit(new AlternateUnit<LuminousFlux>(
			Messages.SI_lm, (AbstractUnit<?>) CANDELA.multiply(STERADIAN)));

	/**
	 * The derived unit for illuminance (<code>lx</code>). One Lux is equal to
	 * one lumen per square metre.
	 */
	public static final Unit<Illuminance> LUX = addUnit(new AlternateUnit<Illuminance>(
			Messages.SI_lx, (AbstractUnit<?>) LUMEN.divide(METRE.pow(2))));

	/**
	 * The derived unit for activity of a radionuclide (<code>Bq</code>). One
	 * becquerel is the radiation caused by one disintegration per second. It is
	 * named after the French physicist, Antoine-Henri Becquerel (1852-1908).
	 */
	public static final Unit<RadioactiveActivity> BECQUEREL = addUnit(new AlternateUnit<RadioactiveActivity>(
			Messages.SI_Bq,
			(AbstractUnit<?>) AbstractUnit.ONE.divide(SECOND)));

	/**
	 * The derived unit for absorbed dose, specific energy (imparted), kerma (
	 * <code>Gy</code>). One gray is equal to the dose of one joule of energy
	 * absorbed per one kilogram of matter. It is named after the British
	 * physician L. H. Gray (1905-1965).
	 */
	public static final Unit<RadiationDoseAbsorbed> GRAY = addUnit(new AlternateUnit<RadiationDoseAbsorbed>(
			Messages.SI_Gy, (AbstractUnit<?>) JOULE.divide(KILOGRAM)));

	/**
	 * The derived unit for dose equivalent (<code>Sv</code>). One Sievert is
	 * equal is equal to the actual dose, in grays, multiplied by a
	 * "quality factor" which is larger for more dangerous forms of radiation.
	 * It is named after the Swedish physicist Rolf Sievert (1898-1966).
	 */
	public static final Unit<RadiationDoseEffective> SIEVERT = addUnit(new AlternateUnit<RadiationDoseEffective>(
			Messages.SI_Sv, (AbstractUnit<?>) JOULE.divide(KILOGRAM)));

	/**
	 * The derived unit for catalytic activity (<code>kat</code>).
	 */
	public static final Unit<CatalyticActivity> KATAL = addUnit(new AlternateUnit<CatalyticActivity>(
			Messages.SI_kat, (AbstractUnit<?>) MOLE.divide(SECOND)));
	// ////////////////////////////
	// SI DERIVED PRODUCT UNITS //
	// ////////////////////////////

	/**
	 * The metric unit for velocity quantities (<code>m/s</code>).
	 * 
	 */
	public static final Unit<Velocity> METRES_PER_SECOND = addUnit(new ProductUnit<Velocity>(
			(AbstractUnit<?>) METRE.divide(SECOND)));

	/**
	 * The metric unit for acceleration quantities (<code>m/s2</code>).
	 */
	public static final Unit<Acceleration> METRES_PER_SQUARE_SECOND = addUnit(new ProductUnit<Acceleration>(
			(AbstractUnit<?>) METRES_PER_SECOND.divide(SECOND)));

	/**
	 * The metric unit for area quantities (<code>m2</code>).
	 */
	public static final Unit<Area> SQUARE_METRE = addUnit(new ProductUnit<Area>(
			(AbstractUnit<?>) METRE.multiply(METRE)));

	/**
	 * The metric unit for volume quantities (<code>m3</code>).
	 */
	public static final Unit<Volume> CUBIC_METRE = addUnit(new ProductUnit<Volume>(
			(AbstractUnit<?>) SQUARE_METRE.multiply(METRE)));

    /////////////////////////////////////////////////////////////////
	// Units outside the SI that are accepted for use with the SI. //
	/////////////////////////////////////////////////////////////////

	/**
	* A dimensionless unit accepted for use with SI units (standard name <code>%</code>).
	*/
	public static final TransformedUnit<Dimensionless> PERCENT
	= new TransformedUnit<Dimensionless>(ONE, new RationalConverter(1, 100));
	
	// //////////
	// Others //
	// //////////
	/**
	 * A unit used to measure the ionizing ability of radiation (standard name
	 * <code>Roentgen</code>).
	 */
	@SuppressWarnings("unchecked")
	public static final Unit<IonizingRadiation> ROENTGEN = (Unit<IonizingRadiation>) addUnit(COULOMB.divide(KILOGRAM)
			.multiply(2.58e-4), Messages.NonSI_R_name);
	
}