package org.openslx.virtualization;

import java.util.List;
import java.util.function.Predicate;

/**
 * Represents a version information.
 * 
 * The version information is used in the field of virtualization (for virtualizers, disk images,
 * virtualization configuration files, ...).
 * 
 * @author Manuel Bentele
 * @version 1.0
 */
public class Version implements Comparable<Version>
{
	private final short major;
	private final short minor;
	private final String name;

	/**
	 * Creates a new version.
	 * 
	 * The version consists of a major version, whereas the minor version is set to the value
	 * <code>0</code> and the version name is undefined.
	 * 
	 * @param major
	 */
	public Version( short major )
	{
		this( major, Short.valueOf( "0" ), null );
	}

	/**
	 * Creates a new version.
	 * 
	 * The version consists of a major version labeled with a version name, whereas the minor version
	 * is set to the value <code>0</code>.
	 * 
	 * @param major major version.
	 * @param name version name.
	 */
	public Version( short major, String name )
	{
		this( major, Short.valueOf( "0" ), name );
	}

	/**
	 * Creates a new version.
	 * 
	 * The version consists of a major and a minor version, whereas the version name is undefined.
	 * 
	 * @param major major version.
	 * @param minor minor version.
	 */
	public Version( short major, short minor )
	{
		this( major, minor, null );
	}

	/**
	 * Creates a new version.
	 * 
	 * The version consists of a major and a minor version labeled with a version name.
	 * 
	 * @param major major version.
	 * @param minor minor version.
	 * @param name version name.
	 */
	public Version( short major, short minor, String name )
	{
		this.major = major;
		this.minor = minor;
		this.name = name;
	}

	/**
	 * Returns the major version.
	 * 
	 * @return major version.
	 */
	public short getMajor()
	{
		return this.major;
	}

	/**
	 * Returns the minor version.
	 * 
	 * @return minor version.
	 */
	public short getMinor()
	{
		return this.minor;
	}

	/**
	 * Returns the full version as {@link Integer}.
	 * 
	 * The full version consists of the major and minor version where both are combined in one
	 * {@link Integer} value. The upper 16-bits of the value represent the major number, whereas
	 * the lower 16-bits represent the minor number.
	 * 
	 * @return full version as {@link Integer}.
	 */
	public int getVersion()
	{
		final int major = this.major;
		final int minor = this.minor;

		return ( major << Short.SIZE ) | minor;
	}

	/**
	 * Returns the name of the version.
	 * 
	 * @return name of the version.
	 */
	public String getName()
	{
		return this.name;
	}

	/**
	 * Checks if version is supported by a version from a list of supported versions.
	 * 
	 * @param supportedVersions list of supported versions.
	 * @return state whether version is supported by a version from the list of versions or not.
	 */
	public boolean isSupported( List<Version> supportedVersions )
	{
		return supportedVersions.contains( this );
	}

	/**
	 * Returns a version from a list of supported versions by its given major version.
	 * 
	 * @param major version.
	 * @param supportedVersions list of supported versions.
	 * @return version from a list of supported versions by its given major version.
	 */
	public static Version getInstanceByMajorFromVersions( short major, List<Version> supportedVersions )
	{
		final Predicate<Version> byMajor = version -> major == version.getMajor();
		return supportedVersions.stream().filter( byMajor ).findFirst().orElse( null );
	}

	@Override
	public boolean equals( Object obj )
	{
		if ( obj == null ) {
			return false;
		} else if ( this.getClass() != obj.getClass() ) {
			return false;
		} else if ( this.compareTo( Version.class.cast( obj ) ) == 0 ) {
			return true;
		} else {
			return false;
		}
	}

	@Override
	public int compareTo( Version v )
	{
		// compare the current version to the specified version
		if ( this.getMajor() < v.getMajor() ) {
			// current major version is smaller than the given major version
			return -1;
		} else if ( this.getMajor() > v.getMajor() ) {
			// current major version is larger than the given major version
			return 1;
		} else {
			// current major version is equal to the given major version
			// so compare the current minor version to the specified minor version
			if ( this.getMinor() < v.getMinor() ) {
				// current minor version is smaller than the given minor version
				// so the entire version is smaller than the given version
				return -1;
			} else if ( this.getMinor() > v.getMinor() ) {
				// current minor version is larger than the given minor version
				// so the entire version is larger than the given version
				return 1;
			} else {
				// current minor version is equal to the given minor version
				// so the entire version is equal to the given version
				return 0;
			}
		}
	}
}