package test2;

/**
 * A class that represents the hour on a 24-hour clock.
 * 
 * <p>
 * A 24-hour clock (sometimes called military time) uses the numbers 0-23 to
 * represent the hour of the day starting at midnight. The mapping between a
 * 24-hour clock and a 12-hour clock is shown in the table below:
 * 
 * <table summary="">
 * <tr>
 * <th>24-hour clock hour&nbsp;&nbsp;&nbsp;</th>
 * <th>12-hour clock hour</th>
 * </tr>
 * <tr>
 * <td>0</td>
 * <td>12AM</td>
 * </tr>
 * <tr>
 * <td>1</td>
 * <td>1AM</td>
 * </tr>
 * <tr>
 * <td>2</td>
 * <td>2AM</td>
 * </tr>
 * <tr>
 * <td>3</td>
 * <td>3AM</td>
 * </tr>
 * <tr>
 * <td>4</td>
 * <td>4AM</td>
 * </tr>
 * <tr>
 * <td>5</td>
 * <td>5AM</td>
 * </tr>
 * <tr>
 * <td>6</td>
 * <td>6AM</td>
 * </tr>
 * <tr>
 * <td>7</td>
 * <td>7AM</td>
 * </tr>
 * <tr>
 * <td>8</td>
 * <td>8AM</td>
 * </tr>
 * <tr>
 * <td>9</td>
 * <td>9AM</td>
 * </tr>
 * <tr>
 * <td>10</td>
 * <td>10AM</td>
 * </tr>
 * <tr>
 * <td>11</td>
 * <td>11AM</td>
 * </tr>
 * <tr>
 * <td>12</td>
 * <td>12PM</td>
 * </tr>
 * <tr>
 * <td>13</td>
 * <td>1PM</td>
 * </tr>
 * <tr>
 * <td>14</td>
 * <td>2PM</td>
 * </tr>
 * <tr>
 * <td>15</td>
 * <td>3PM</td>
 * </tr>
 * <tr>
 * <td>16</td>
 * <td>4PM</td>
 * </tr>
 * <tr>
 * <td>17</td>
 * <td>5PM</td>
 * </tr>
 * <tr>
 * <td>18</td>
 * <td>6PM</td>
 * </tr>
 * <tr>
 * <td>19</td>
 * <td>7PM</td>
 * </tr>
 * <tr>
 * <td>20</td>
 * <td>8PM</td>
 * </tr>
 * <tr>
 * <td>21</td>
 * <td>9PM</td>
 * </tr>
 * <tr>
 * <td>22</td>
 * <td>10PM</td>
 * </tr>
 * <tr>
 * <td>23</td>
 * <td>11PM</td>
 * </tr>
 * </table>
 * 
 *
 */
public class Hour {
    /**
     * The string "AM"
     */
    public static final String AM = "AM";

    /**
     * The string "PM"
     */
    public static final String PM = "PM";

    private int hour;

    /**
     * Returns <code>true</code> if <code>hour</code> is a valid hour on a
     * 24-hour clock, and <code>false</code> otherwise.
     * 
     * @param hour
     *            an hour on a 24-hour clock
     * @return <code>true</code> if <code>hour</code> is a valid hour on a
     *         24-hour clock, and <code>false</code> otherwise.
     */
    public static boolean isValid(int hour) {
        return hour >= 0 && hour <= 23;
    }

    /**
     * Returns <code>true</code> if <code>hour</code> is a valid hour on a
     * 12-hour clock and <code>ampm</code> is equal to one of
     * <code>Hour.AM</code> or <code>Hour.PM</code>, and <code>false</code>
     * otherwise.
     * 
     * @param hour
     *            an hour on a 12-hour clock
     * @param ampm
     *            the string <code>Hour.AM</code> or <code>Hour.PM</code>
     * @return <code>true</code> if <code>hour</code> is a valid hour on a
     *         12-hour clock and <code>ampm</code> is equal to one of
     *         <code>Hour.AM</code> or <code>Hour.PM</code>, and
     *         <code>false</code> otherwise
     */
    public static boolean isValid(int hour, String ampm) {
        return hour >= 1 && hour <= 12 && (ampm.equals(Hour.AM) || ampm.equals(Hour.PM));
    }

    /**
     * Checks if an hour and String pair form a valid hour on a 12-hour clock.
     * 
     * @param hour
     *            the hour
     * @param ampm
     *            the string <code>Hour.AM</code> or <code>Hour.PM</code>
     * @throws IllegalArgumentException
     *             if hour is less than 1 or greater than 12
     * @throws IllegalArgumentException
     *             if ampm is not one of <code>Hour.AM</code> or
     *             <code>Hour.PM</code>
     */
    public static void check12(int hour, String ampm) {
        if (!Hour.isValid(hour, ampm)) {
            throw new IllegalArgumentException("");
        }
    }

    /**
     * Checks if an hour is a valid hour on a 24-hour clock.
     * 
     * @param hour
     *            the hour
     * 
     * @throws IllegalArgumentException
     *             if hour is less than 0 or greater than 23
     */
    public static void check24(int hour) {
        if (!Hour.isValid(hour)) {
            throw new IllegalArgumentException("hour must be between 0 and 23 on a 24-hour clock");
        }
    }

    /**
     * Converts an hour defined on a 12-hour clock to the equivalent hour on a
     * 24-hour clock.
     * 
     * @param hour
     *            hour the hour on a 12-hour clock
     * @param ampm
     *            the string Hour.AM or Hour.PM
     * @return the hour on a 24-hour clock equivalent to the given hour defined
     *         on a 12-hour clock
     * @throws IllegalArgumentException
     *             if hour is less than 1 or greater than 12
     * @throws IllegalArgumentException
     *             if ampm is not one of Hour.AM or Hour.PM
     * 
     */
    public static int to24HourClock(int hour, String ampm) {
        Hour.check12(hour, ampm);
        if (hour == 12 && ampm.equals(Hour.AM)) {
            return 0;
        } else if (hour == 12 && ampm.equals(Hour.PM)) {
            return 12;
        } else if (ampm.equals(Hour.AM)) {
            return hour;
        }
        return hour + 12;
    }

    /**
     * Converts an hour defined on a 24-hour clock to the equivalent hour on a
     * 12-hour clock.
     * 
     * @param hour
     *            the hour on a 24-hour clock
     * @return the hour on a 12-hour clock equivalent to the given hour defined
     *         on a 24-hour clock
     * @throws IllegalArgumentException
     *             if hour is less than 0 or greater than 23
     */
    public static int to12HourClock(int hour) {
        Hour.check24(hour);
        if (hour == 0 || hour == 12) {
            return 12;
        } else if (hour < 12) {
            return hour;
        }
        return 23 - hour;
    }

    /**
     * Initializes the hour given the <code>hour</code> on a 24-hour clock.
     * 
     * @param hour
     *            the hour on a 24-hour clock
     * @throws IllegalArgumentException
     *             if hour is less than 0 or greater than 23
     */
    public Hour(int hour) {
        Hour.check24(hour);
        this.hour = hour;
    }

    /**
     * Initializes the hour given the <code>hour</code> on a 12-hour clock and a
     * string indicating AM or PM.
     * 
     * @param hour
     *            the hour on a 12-hour clock
     * @param ampm
     *            the string <code>Hour.AM</code> or <code>Hour.PM</code>
     * @throws IllegalArgumentException
     *             if hour is less than 1 or greater than 12
     * @throws IllegalArgumentException
     *             if ampm is not one of Hour.AM or Hour.PM
     */
    public Hour(int hour, String ampm) {
        Hour.check12(hour, ampm);
        this.hour = Hour.to24HourClock(hour, ampm);
    }

    /**
     * Initializes this hour by copying the hour from a another 24-hour
     * <code>Hour</code> instance.
     * 
     * @param other
     *            another 24-hour Hour instance
     */
    public Hour(Hour other) {
        this.hour = other.hour;
    }

    /**
     * Returns the hour of this 24-hour instance.
     * 
     * @return the hour of this 24-hour instance
     */
    public int getHour() {
        return this.hour;
    }

    /**
     * Sets the hour of this 24-hour instance.
     * 
     * @param hour
     *            the hour on a 24-hour clock
     * @throws IllegalArgumentException
     *             if hour is less than 0 or greater than 23
     */
    public void setHour(int hour) {
        Hour.check24(hour);
        this.hour = hour;
    }

    /**
     * Sets the hour of this 24-hour instance using an hour from a 12-hour
     * clock.
     * 
     * @param hour
     *            the hour on a 12-hour clock
     * @param ampm
     *            the string <code>Hour.AM</code> or <code>Hour.PM</code>
     * @throws IllegalArgumentException
     *             if hour is less than 1 or greater than 12
     * @throws IllegalArgumentException
     *             if ampm is not one of Hour.AM or Hour.PM
     */
    public void setHour(int hour, String ampm) {
        Hour.check12(hour, ampm);
        this.hour = Hour.to24HourClock(hour, ampm);
    }

    /**
     * Compares this hour to a string containing an hour on a 12-hour clock. The
     * string is assumed to start with an integer followed by a space followed
     * by one or more characters; the string does not necessarily represent a
     * valid hour on a 12-hour clock.
     * 
     * <p>
     * The method returns <code>true</code> if and only if all of the following
     * are true:
     * 
     * <ul>
     * <li>the string <code>h</code> is not equal to null
     * <li>the string <code>h</code> represents a valid hour on a 12-hour clock
     * <li>the hour represented by <code>h</code> is equivalent to the hour
     * represented by this <code>Hour</code>
     * </ul>
     * 
     * <p>
     * Some examples:
     * 
     * <pre>
     * Hour hour = new Hour(18); // 6PM
     * String h = "6 PM";
     * boolean eq = hour.equals(h); // eq is equal to true
     * 
     * h = "6 AM";
     * eq = hour.equals(h); // eq is equal to false
     * 
     * h = "100 elephants";
     * eq = hour.equals(h); // eq is equal to false
     * 
     * h = null;
     * eq = hour.equals(h); // eq is equal to false
     * </pre>
     * 
     * @param h
     *            an hour on a 12-hour clock represented as a string
     * @return true if the conditions described above are true, and false
     *         otherwise
     * @pre. h starts with an integer followed by a space followed by one or more
     *      characters
     */
    public boolean equals(String h) {
        String[] parts = h.split(" ");
        int hour = Integer.parseInt(parts[0]);
        String ampm = parts[1];
        boolean eq = h != null && Hour.isValid(hour, ampm);
        if (eq) {
            eq = this.hour == Hour.to24HourClock(hour, ampm);
        }
        return eq;
    }


}