/*******************************************************************************
 * Copyright (c) 2000, 2008 IBM Corporation 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:
 *     IBM Corporation - initial API and implementation
 * Port to the D programming language:
 *     Frank Benoit <benoit@tionex.de>
 *******************************************************************************/
module dwt.layout.FormAttachment;

import dwt.DWT;
import dwt.widgets.Control;
import dwt.layout.FormLayout;
import dwt.layout.FormData;

import tango.text.convert.Format;
import dwt.dwthelper.utils;

/**
 * Instances of this class are used to define the edges of a control
 * within a <code>FormLayout</code>.
 * <p>
 * <code>FormAttachments</code> are set into the top, bottom, left,
 * and right fields of the <code>FormData</code> for a control.
 * For example:
 * <pre>
 *      FormData data = new FormData();
 *      data.top = new FormAttachment(0,5);
 *      data.bottom = new FormAttachment(100,-5);
 *      data.left = new FormAttachment(0,5);
 *      data.right = new FormAttachment(100,-5);
 *      button.setLayoutData(data);
 * </pre>
 * </p>
 * <p>
 * A <code>FormAttachment</code> defines where to attach the side of
 * a control by using the equation, y = ax + b. The "a" term represents
 * a fraction of the parent composite's width (from the left) or height
 * (from the top). It can be defined using a numerator and denominator,
 * or just a percentage value. If a percentage is used, the denominator
 * is set to 100. The "b" term in the equation represents an offset, in
 * pixels, from the attachment position. For example:
 * <pre>
 *      FormAttachment attach = new FormAttachment (20, -5);
 * </pre>
 * specifies that the side to which the <code>FormAttachment</code>
 * object belongs will lie at 20% of the parent composite, minus 5 pixels.
 * </p>
 * <p>
 * Control sides can also be attached to another control.
 * For example:
 * <pre>
 *      FormAttachment attach = new FormAttachment (button, 10);
 * </pre>
 * specifies that the side to which the <code>FormAttachment</code>
 * object belongs will lie in the same position as the adjacent side of
 * the <code>button</code> control, plus 10 pixels. The control side can
 * also be attached to the opposite side of the specified control.
 * For example:
 * <pre>
 *      FormData data = new FormData ();
 *      data.left = new FormAttachment (button, 0, DWT.LEFT);
 * </pre>
 * specifies that the left side of the control will lie in the same position
 * as the left side of the <code>button</code> control. The control can also
 * be attached in a position that will center the control on the specified
 * control. For example:
 * <pre>
 *      data.left = new FormAttachment (button, 0, DWT.CENTER);
 * </pre>
 * specifies that the left side of the control will be positioned so that it is
 * centered between the left and right sides of the <code>button</code> control.
 * If the alignment is not specified, the default is to attach to the adjacent side.
 * </p>
 *
 * @see FormLayout
 * @see FormData
 * @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a>
 *
 * @since 2.0
 */
public final class FormAttachment {
    /**
     * numerator specifies the numerator of the "a" term in the
     * equation, y = ax + b, which defines the attachment.
     */
    public int numerator;

    /**
     * denominator specifies the denominator of the "a" term in the
     * equation, y = ax + b, which defines the attachment.
     *
     * The default value is 100.
     */
    public int denominator = 100;

    /**
     * offset specifies the offset, in pixels, of the control side
     * from the attachment position.
     * If the offset is positive, then the control side is offset
     * to the right of or below the attachment position. If it is
     * negative, then the control side is offset to the left of or
     * above the attachment position.
     *
     * This is equivalent to the "b" term in the equation y = ax + b.
     * The default value is 0.
     */
    public int offset;

    /**
     * control specifies the control to which the control side is
     * attached.
     */
    public Control control;

    /**
     * alignment specifies the alignment of the control side that is
     * attached to a control.
     * <p>
     * For top and bottom attachments, TOP, BOTTOM and CENTER are used. For left
     * and right attachments, LEFT, RIGHT and CENTER are used. If any other case
     * occurs, the default will be used instead.
     * </p>
     *
     * <br>Possible values are: <ul>
     *    <li>{@link DWT#TOP}: Attach the side to the top side of the specified control.</li>
     *    <li>{@link DWT#BOTTOM}: Attach the side to the bottom side of the specified control.</li>
     *    <li>{@link DWT#LEFT}: Attach the side to the left side of the specified control.</li>
     *    <li>{@link DWT#RIGHT}: Attach the side to the right side of the specified control.</li>
     *    <li>{@link DWT#CENTER}: Attach the side at a position which will center the control on the specified control.</li>
     *    <li>{@link DWT#DEFAULT}: Attach the side to the adjacent side of the specified control.</li>
     * </ul>
     */
    public int alignment;

/**
 * Constructs a new instance of this class.
 * Since no numerator, denominator or offset is specified,
 * the attachment is treated as a percentage of the form.
 * The numerator is zero, the denominator is 100 and the
 * offset is zero.
 *
 * @since 3.2
 */
public this () {
}

/**
 * Constructs a new instance of this class given a numerator
 * Since no denominator or offset is specified, the default
 * is to treat the numerator as a percentage of the form, with a
 * denominator of 100. The offset is zero.
 *
 * @param numerator the percentage of the position
 *
 * @since 3.0
 */
public this (int numerator) {
    this (numerator, 100, 0);
}

/**
 * Constructs a new instance of this class given a numerator
 * and an offset. Since no denominator is specified, the default
 * is to treat the numerator as a percentage of the form, with a
 * denominator of 100.
 *
 * @param numerator the percentage of the position
 * @param offset the offset of the side from the position
 */
public this (int numerator, int offset) {
    this (numerator, 100, offset);
}

/**
 * Constructs a new instance of this class given a numerator
 * and denominator and an offset. The position of the side is
 * given by the fraction of the form defined by the numerator
 * and denominator.
 *
 * @param numerator the numerator of the position
 * @param denominator the denominator of the position
 * @param offset the offset of the side from the position
 */
public this (int numerator, int denominator, int offset) {
    if (denominator is 0) DWT.error (DWT.ERROR_CANNOT_BE_ZERO);
    this.numerator = numerator;
    this.denominator = denominator;
    this.offset = offset;
}

/**
 * Constructs a new instance of this class given a control.
 * Since no alignment is specified, the default alignment is
 * to attach the side to the adjacent side of the specified
 * control. Since no offset is specified, an offset of 0 is
 * used.
 *
 * @param control the control the side is attached to
 */
public this (Control control) {
    this (control, 0, DWT.DEFAULT);
}

/**
 * Constructs a new instance of this class given a control
 * and an offset. Since no alignment is specified, the default
 * alignment is to attach the side to the adjacent side of the
 * specified control.
 *
 * @param control the control the side is attached to
 * @param offset the offset of the side from the control
 */
public this (Control control, int offset) {
    this (control, offset, DWT.DEFAULT);
}

/**
 * Constructs a new instance of this class given a control,
 * an offset and an alignment.  The possible alignment values are:
 * <dl>
 * <dt><b>{@link DWT#TOP}</b></dt>
 * <dd>the side will be attached to the top side of the specified control</dd>
 * <dt><b>{@link DWT#BOTTOM}</b></dt>
 * <dd>the side will be attached to the bottom side of the specified control</dd>
 * <dt><b>{@link DWT#LEFT}</b></dt>
 * <dd>the side will be attached to the left side of the specified control</dd>
 * <dt><b>{@link DWT#RIGHT}</b></dt>
 * <dd>the side will be attached to the right side of the specified control</dd>
 * <dt><b>{@link DWT#CENTER}</b></dt>
 * <dd>the side will be centered on the same side of the specified control</dd>
 * <dt><b>{@link DWT#DEFAULT}</b></dt>
 * <dd>the side will be attached to the adjacent side of the specified control</dd>
 * </dl>
 *
 * @param control the control the side is attached to
 * @param offset the offset of the side from the control
 * @param alignment the alignment of the side to the control it is attached to,
 *      one of TOP, BOTTOM, LEFT, RIGHT, CENTER, or DEFAULT
 */
public this (Control control, int offset, int alignment) {
    this.control = control;
    this.offset = offset;
    this.alignment = alignment;
}

FormAttachment divide (int value) {
    return new FormAttachment (numerator, denominator * value, offset / value);
}

int gcd (int m, int n) {
    int temp;
    m = Math.abs (m);
    n = Math.abs (n);
    if (m < n) {
        temp = m;
        m = n;
        n = temp;
    }
    while (n !is 0){
        temp = m;
        m = n;
        n = temp % n;
    }
    return m;
}

FormAttachment minus (FormAttachment attachment) {
    FormAttachment solution = new FormAttachment ();
    solution.numerator = numerator * attachment.denominator - denominator * attachment.numerator;
    solution.denominator = denominator * attachment.denominator;
    int gcd = gcd (solution.denominator, solution.numerator);
    solution.numerator = solution.numerator / gcd;
    solution.denominator = solution.denominator / gcd;
    solution.offset = offset - attachment.offset;
    return solution;
}

FormAttachment minus (int value) {
    return new FormAttachment (numerator, denominator, offset - value);
}

FormAttachment plus (FormAttachment attachment) {
    FormAttachment solution = new FormAttachment ();
    solution.numerator = numerator * attachment.denominator + denominator * attachment.numerator;
    solution.denominator = denominator * attachment.denominator;
    int gcd = gcd (solution.denominator, solution.numerator);
    solution.numerator = solution.numerator / gcd;
    solution.denominator = solution.denominator / gcd;
    solution.offset = offset + attachment.offset;
    return solution;
}

FormAttachment plus (int value) {
    return new FormAttachment (numerator, denominator, offset + value);
}

int solveX (int value) {
    if (denominator is 0) DWT.error (DWT.ERROR_CANNOT_BE_ZERO);
    return ((numerator * value) / denominator) + offset;
}

int solveY (int value) {
    if (numerator is 0) DWT.error (DWT.ERROR_CANNOT_BE_ZERO);
    return (value - offset) * denominator / numerator;
}

/**
 * Returns a string containing a concise, human-readable
 * description of the receiver.
 *
 * @return a string representation of the FormAttachment
 */
public override String toString () {
    String string = control !is null ? control.toString () : Format( "{}/{}", numerator, denominator );
    return Format("{{y = ({})x + {}}", string, ( offset >= 0 ? Format(")x + {}", offset ) : Format( ")x - {}", -offset)));
}

}