/*******************************************************************************
 * Copyright (c) 2000, 2003 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jface.preference;

import org.eclipse.jface.util.IPropertyChangeListener;

/**
 * The <code>IPreferenceStore</code> interface represents a table mapping
 * named preferences to values. If there is no value for a given name, 
 * then that preferences's default value is returned; and if there is no
 * default value for that preference, then a default-default value is returned.
 * The default-default values for the primitive types are as follows:
 * <ul>
 * 	<li><code>boolean</code> = <code>false</code></li>
 * 	<li><code>double</code> = <code>0.0</code></li>
 * 	<li><code>float</code> = <code>0.0f</code></li>
 * 	<li><code>int</code> = <code>0</code></li>
 *  <li><code>long</code> = <code>0</code></li>
 * 	<li><code>String</code> = <code>""</code> (the empty string)</li>
 * </ul>
 * <p>
 * Thus a preference store maintains two values for each of a set of
 * names: a current value and a default value.
 * The typical usage is to establish the defaults for all known preferences
 * and then restore previously stored values for preferences whose values 
 * were different from their defaults. After the current values of
 * the preferences have been modified, it is a simple matter to write
 * out only those preferences whose values are different from their defaults.
 * This two-tiered approach to saving and restoring preference setting
 * minimized the number of preferences that need to be persisted; indeed,
 * the normal starting state does not require storing any preferences
 * at all.
 * </p>
 * <p>
 * A property change event is reported whenever a preferences current
 * value actually changes (whether through <code>setValue</code>,
 * <code>setToDefault</code>, or other unspecified means). Note, however,
 * that manipulating default values (with <code>setDefault</code>)
 * does not cause such events to be reported.
 * </p>
 * <p>
 * Clients who need a preference store may implement this interface or 
 * instantiate the standard implementation <code>PreferenceStore</code>.
 * </p>
 *
 * @see PreferenceStore
 */
public interface IPreferenceStore {

	/**
	 * The default-default value for boolean preferences (<code>false</code>).
	 */
	public static final boolean BOOLEAN_DEFAULT_DEFAULT = false;

	/**
	 * The default-default value for double preferences (<code>0.0</code>).
	 */
	public static final double DOUBLE_DEFAULT_DEFAULT = 0.0;

	/**
	 * The default-default value for float preferences (<code>0.0f</code>).
	 */
	public static final float FLOAT_DEFAULT_DEFAULT = 0.0f;

	/**
	 * The default-default value for int preferences (<code>0</code>).
	 */
	public static final int INT_DEFAULT_DEFAULT = 0;

	/**
	 * The default-default value for long preferences (<code>0L</code>).
	 */
	public static final long LONG_DEFAULT_DEFAULT = 0L;

	/**
	 * The default-default value for String preferences (<code>""</code>).
	 */
	public static final String STRING_DEFAULT_DEFAULT = ""; //$NON-NLS-1$

	/**
	 * The string representation used for <code>true</code> (<code>"true"</code>).
	 */
	public static final String TRUE = "true"; //$NON-NLS-1$

	/**
	 * The string representation used for <code>false</code> (<code>"false"</code>).
	 */
	public static final String FALSE = "false"; //$NON-NLS-1$
/**
 * Adds a property change listener to this preference store.
 *
 * @param listener a property change listener
 */
public void addPropertyChangeListener(IPropertyChangeListener listener);
/**
 * Returns whether the named preference is known to this preference
 * store.
 *
 * @param name the name of the preference
 * @return <code>true</code> if either a current value or a default
 *  value is known for the named preference, and <code>false</code>otherwise
 */
public boolean contains(String name);
/**
 * Fires a property change event corresponding to a change to the
 * current value of the preference with the given name.
 * <p>
 * This method is provided on this interface to simplify the implementation 
 * of decorators. There is normally no need to call this method since
 * <code>setValue</code> and <code>setToDefault</code> report such
 * events in due course. Implementations should funnel all preference
 * changes through this method.
 * </p>
 *
 * @param name the name of the preference, to be used as the property
 *  in the event object
 * @param oldValue the old value
 * @param newValue the new value
 */
public void firePropertyChangeEvent(String name, Object oldValue, Object newValue);
/**
 * Returns the current value of the boolean-valued preference with the
 * given name.
 * Returns the default-default value (<code>false</code>) if there
 * is no preference with the given name, or if the current value 
 * cannot be treated as a boolean.
 *
 * @param name the name of the preference
 * @return the boolean-valued preference
 */
public boolean getBoolean(String name);
/**
 * Returns the default value for the boolean-valued preference
 * with the given name.
 * Returns the default-default value (<code>false</code>) if there
 * is no default preference with the given name, or if the default 
 * value cannot be treated as a boolean.
 *
 * @param name the name of the preference
 * @return the default value of the named preference
 */
public boolean getDefaultBoolean(String name);
/**
 * Returns the default value for the double-valued preference
 * with the given name.
 * Returns the default-default value (<code>0.0</code>) if there
 * is no default preference with the given name, or if the default 
 * value cannot be treated as a double.
 *
 * @param name the name of the preference
 * @return the default value of the named preference
 */
public double getDefaultDouble(String name);
/**
 * Returns the default value for the float-valued preference
 * with the given name.
 * Returns the default-default value (<code>0.0f</code>) if there
 * is no default preference with the given name, or if the default 
 * value cannot be treated as a float.
 *
 * @param name the name of the preference
 * @return the default value of the named preference
 */
public float getDefaultFloat(String name);
/**
 * Returns the default value for the integer-valued preference
 * with the given name.
 * Returns the default-default value (<code>0</code>) if there
 * is no default preference with the given name, or if the default 
 * value cannot be treated as an integer.
 *
 * @param name the name of the preference
 * @return the default value of the named preference
 */
public int getDefaultInt(String name);
/**
 * Returns the default value for the long-valued preference
 * with the given name.
 * Returns the default-default value (<code>0L</code>) if there
 * is no default preference with the given name, or if the default 
 * value cannot be treated as a long.
 *
 * @param name the name of the preference
 * @return the default value of the named preference
 */
public long getDefaultLong(String name);
/**
 * Returns the default value for the string-valued preference
 * with the given name.
 * Returns the default-default value (the empty string <code>""</code>) 
 * is no default preference with the given name, or if the default 
 * value cannot be treated as a string.
 *
 * @param name the name of the preference
 * @return the default value of the named preference
 */
public String getDefaultString(String name);
/**
 * Returns the current value of the double-valued preference with the
 * given name.
 * Returns the default-default value (<code>0.0</code>) if there
 * is no preference with the given name, or if the current value 
 * cannot be treated as a double.
 *
 * @param name the name of the preference
 * @return the double-valued preference
 */
public double getDouble(String name);
/**
 * Returns the current value of the float-valued preference with the
 * given name.
 * Returns the default-default value (<code>0.0f</code>) if there
 * is no preference with the given name, or if the current value 
 * cannot be treated as a float.
 *
 * @param name the name of the preference
 * @return the float-valued preference
 */
public float getFloat(String name);
/**
 * Returns the current value of the integer-valued preference with the
 * given name.
 * Returns the default-default value (<code>0</code>) if there
 * is no preference with the given name, or if the current value 
 * cannot be treated as an integter.
 *
 * @param name the name of the preference
 * @return the int-valued preference
 */
public int getInt(String name);
/**
 * Returns the current value of the long-valued preference with the
 * given name.
 * Returns the default-default value (<code>0L</code>) if there
 * is no preference with the given name, or if the current value 
 * cannot be treated as a long.
 *
 * @param name the name of the preference
 * @return the long-valued preference
 */
public long getLong(String name);
/**
 * Returns the current value of the string-valued preference with the
 * given name.
 * Returns the default-default value (the empty string <code>""</code>)
 * if there is no preference with the given name, or if the current value 
 * cannot be treated as a string.
 *
 * @param name the name of the preference
 * @return the string-valued preference
 */
public String getString(String name);
/**
 * Returns whether the current value of the preference with the given name
 * has the default value.
 *
 * @param name the name of the preference
 * @return <code>true</code> if the preference has a known default value
 * and its current value is the same, and <code>false</code> otherwise
 * (including the case where the preference is unknown to this store)
 */
public boolean isDefault(String name);
/**
 * Returns whether the current values in this property store
 * require saving.
 *
 * @return <code>true</code> if at least one of the preferences
 *  known to this store has a current value different from its
 *  default value, and <code>false</code> otherwise
 */
public boolean needsSaving();
/**
 * Sets the current value of the preference with the given name to
 * the given string value.
 * <p>
 * This method is provided on this interface to simplify the implementation 
 * of decorators, and does not report a property change event.
 * Normal clients should instead call <code>setValue</code>.
 * </p>
 *
 * @param name the name of the preference
 * @param value the new current value of the preference
 */
public void putValue(String name, String value);
/**
 * Removes the given listener from this preference store.
 * Has no affect if the listener is not registered.
 *
 * @param listener a property change listener
 */
public void removePropertyChangeListener(IPropertyChangeListener listener);
/**
 * Sets the default value for the double-valued preference with the
 * given name. 
 * <p>
 * Note that the current value of the preference is affected if
 * the preference's current value was its old default value, in which
 * case it changes to the new default value. If the preference's current
 * is different from its old default value, its current value is
 * unaffected. No property change events are reported by changing default
 * values.
 * </p>
 *
 * @param name the name of the preference
 * @param value the new default value for the preference
 */
public void setDefault(String name, double value);
/**
 * Sets the default value for the float-valued preference with the
 * given name. 
 * <p>
 * Note that the current value of the preference is affected if
 * the preference's current value was its old default value, in which
 * case it changes to the new default value. If the preference's current
 * is different from its old default value, its current value is
 * unaffected. No property change events are reported by changing default
 * values.
 * </p>
 *
 * @param name the name of the preference
 * @param value the new default value for the preference
 */
public void setDefault(String name, float value);
/**
 * Sets the default value for the integer-valued preference with the
 * given name. 
 * <p>
 * Note that the current value of the preference is affected if
 * the preference's current value was its old default value, in which
 * case it changes to the new default value. If the preference's current
 * is different from its old default value, its current value is
 * unaffected. No property change events are reported by changing default
 * values.
 * </p>
 *
 * @param name the name of the preference
 * @param value the new default value for the preference
 */
public void setDefault(String name, int value);
/**
 * Sets the default value for the long-valued preference with the
 * given name. 
 * <p>
 * Note that the current value of the preference is affected if
 * the preference's current value was its old default value, in which
 * case it changes to the new default value. If the preference's current
 * is different from its old default value, its current value is
 * unaffected. No property change events are reported by changing default
 * values.
 * </p>
 *
 * @param name the name of the preference
 * @param value the new default value for the preference
 */
public void setDefault(String name, long value);
/**
 * Sets the default value for the string-valued preference with the
 * given name. 
 * <p>
 * Note that the current value of the preference is affected if
 * the preference's current value was its old default value, in which
 * case it changes to the new default value. If the preference's current
 * is different from its old default value, its current value is
 * unaffected. No property change events are reported by changing default
 * values.
 * </p>
 *
 * @param name the name of the preference
 * @param value the new default value for the preference
 */
public void setDefault(String name, String defaultObject);
/**
 * Sets the default value for the boolean-valued preference with the
 * given name. 
 * <p>
 * Note that the current value of the preference is affected if
 * the preference's current value was its old default value, in which
 * case it changes to the new default value. If the preference's current
 * is different from its old default value, its current value is
 * unaffected. No property change events are reported by changing default
 * values.
 * </p>
 *
 * @param name the name of the preference
 * @param value the new default value for the preference
 */
public void setDefault(String name, boolean value);
/**
 * Sets the current value of the preference with the given name back
 * to its default value.
 * <p>
 * Note that the preferred way of re-initializing a preference to the
 * appropriate default value is to call <code>setToDefault</code>.
 * This is implemented by removing the named value from the store, 
 * thereby exposing the default value.
 * </p>
 *
 * @param name the name of the preference
 */
public void setToDefault(String name);
/**
 * Sets the current value of the double-valued preference with the
 * given name.
 * <p>
 * A property change event is reported if the current value of the 
 * preference actually changes from its previous value. In the event
 * object, the property name is the name of the preference, and the
 * old and new values are wrapped as objects.
 * </p>
 * <p>
 * Note that the preferred way of re-initializing a preference to its
 * default value is to call <code>setToDefault</code>.
 * </p>
 *
 * @param name the name of the preference
 * @param value the new current value of the preference
 */
public void setValue(String name, double value);
/**
 * Sets the current value of the float-valued preference with the
 * given name.
 * <p>
 * A property change event is reported if the current value of the 
 * preference actually changes from its previous value. In the event
 * object, the property name is the name of the preference, and the
 * old and new values are wrapped as objects.
 * </p>
 * <p>
 * Note that the preferred way of re-initializing a preference to its
 * default value is to call <code>setToDefault</code>.
 * </p>
 *
 * @param name the name of the preference
 * @param value the new current value of the preference
 */
public void setValue(String name, float value);
/**
 * Sets the current value of the integer-valued preference with the
 * given name.
 * <p>
 * A property change event is reported if the current value of the 
 * preference actually changes from its previous value. In the event
 * object, the property name is the name of the preference, and the
 * old and new values are wrapped as objects.
 * </p>
 * <p>
 * Note that the preferred way of re-initializing a preference to its
 * default value is to call <code>setToDefault</code>.
 * </p>
 *
 * @param name the name of the preference
 * @param value the new current value of the preference
 */
public void setValue(String name, int value);
/**
 * Sets the current value of the long-valued preference with the
 * given name.
 * <p>
 * A property change event is reported if the current value of the 
 * preference actually changes from its previous value. In the event
 * object, the property name is the name of the preference, and the
 * old and new values are wrapped as objects.
 * </p>
 * <p>
 * Note that the preferred way of re-initializing a preference to its
 * default value is to call <code>setToDefault</code>.
 * </p>
 *
 * @param name the name of the preference
 * @param value the new current value of the preference
 */
public void setValue(String name, long value);
/**
 * Sets the current value of the string-valued preference with the
 * given name.
 * <p>
 * A property change event is reported if the current value of the 
 * preference actually changes from its previous value. In the event
 * object, the property name is the name of the preference, and the
 * old and new values are wrapped as objects.
 * </p>
 * <p>
 * Note that the preferred way of re-initializing a preference to its
 * default value is to call <code>setToDefault</code>.
 * </p>
 *
 * @param name the name of the preference
 * @param value the new current value of the preference
 */
public void setValue(String name, String value);
/**
 * Sets the current value of the boolean-valued preference with the
 * given name.
 * <p>
 * A property change event is reported if the current value of the 
 * preference actually changes from its previous value. In the event
 * object, the property name is the name of the preference, and the
 * old and new values are wrapped as objects.
 * </p>
 * <p>
 * Note that the preferred way of re-initializing a preference to its
 * default value is to call <code>setToDefault</code>.
 * </p>
 *
 * @param name the name of the preference
 * @param value the new current value of the preference
 */
public void setValue(String name, boolean value);
}