Automated calculation of current year and first Monday.

nigel.stanger / XML

Browse code Automated calculation of current year and first Monday. This means we no longer have to change the dates every year! Note that this does imply that the script now always generates output for the current year, so you can’t run it ahead of time (e.g., in December). master
1 parent 95c6e19 commit f5cfd203b16f7a1d53921353e4d3df1ff6ac149f Nigel Stanger authored on 31 Jan 2019

Browse code

This means we no longer have to change the dates every year! Note that this does imply that the script now always generates output for the current year, so you can’t run it ahead of time (e.g., in December).

master

1 parent 95c6e19 commit f5cfd203b16f7a1d53921353e4d3df1ff6ac149f

Nigel Stanger authored on 31 Jan 2019

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          generate_calendar_dates.php
 */
 
 
/*
	Date of the Monday of the first academic week of the year. Teaching weeks start on Monday, so this is a convenient base point to start from. This will need to be updated annually.
	Date of the Monday of the first academic week of the year (ISO 8601). Teaching weeks start on Monday, so this is a convenient base point to start from. Note that this is always for the *current* year!
*/
$first_monday = new DateTime( "2018-12-31" );
$first_monday = new DateTime();
$first_monday->setISODate(date("Y"), 1);
 
 
 
/*
	Teaching period configuration. This will need to be updated annually. It's easily extensible to a new teaching period simply by adding a new specification for that period. The key should be mixed-case alphanumeric (i.e., no whitespace, no punctuation or other special characters). The components of each period specification are:

            <?php

/*
	This script generates an XSLT include file that contains templates specifying the date ranges for every week of the three main teaching periods through the year (i.e., summer school, first semester, second semester). Simply set the configuration as outlined below and make to regenerate the templates.
*/


/*
	Date of the Monday of the first academic week of the year (ISO 8601). Teaching weeks start on Monday, so this is a convenient base point to start from. Note that this is always for the *current* year!
*/
$first_monday = new DateTime();
$first_monday->setISODate(date("Y"), 1);



/*
	Teaching period configuration. This will need to be updated annually. It's easily extensible to a new teaching period simply by adding a new specification for that period. The key should be mixed-case alphanumeric (i.e., no whitespace, no punctuation or other special characters). The components of each period specification are:
	
	first_week:		The academic week number of the first week of the period.
		
	last_week:		The academic week number of the last week of the period.
		
	break_weeks:	A list of breaks that occur during the teaching period.
					Each is specified by the start (break_start) and end
					(break_end) week. If a break is only one week long, then
					break_start and break_end should be equal. If there are no
					breaks in the teaching period, include a single break
					specification with both break_start and break_end set to zero.
					
					The list should ideally be in ascending order, but the
					script doesn't assume this and sorts the list anyway. Weeks
					are numbered by academic week number rather than week within
					the teaching period.
*/
$periods = array(
	'SS' => array(
        'first_week'  => 2,
        'last_week'   => 7,
        'break_weeks' => array(
            array(
                'break_starts' => 0,
                'break_ends'  => 0,
            ),
        ),
    ),
	'S1' => array(
        'first_week'  => 9,
        'last_week'   => 22,
        'break_weeks' => array(
            array(
                'break_starts' => 17,
                'break_ends'  => 17,
            ),
        ),
    ),
	'S2' => array(
        'first_week'  => 28,
        'last_week'   => 41,
        'break_weeks' => array(
            array(
                'break_starts' => 35,
                'break_ends'  => 35,
            ),
        ),
    ),
	'FY' => array(
        'first_week'  => 9,
        'last_week'   => 41,
        'break_weeks' => array(
            array(
                'break_starts' => 17,
                'break_ends'  => 17,
            ),
            array(
                'break_starts' => 23,
                'break_ends'  => 27,
            ),
            array(
                'break_starts' => 35,
                'break_ends'  => 35,
            ),
        ),
    ),
    # This represents the whole year from start to finish.
    'YY' => array(
        'first_week'  => 1,
        'last_week'   => 52,
        'break_weeks' => array(),
    ),
);


// We need a condition to validate the period code in the templates.
$period_condition = sprintf( "( @period = '%s' )", implode( "' ) or ( @period = '", array_keys( $periods ) ) );

// We also a list of valid period code values for the error string.
$period_list = sprintf( '"%s"', implode( '", "', array_keys( $periods ) ) );

// The period and week variables are defined identically in both templates, so
// let's define them just once here to ensure consistency.
$shared_parameters = <<<EOT
				<xsl:with-param name="period">
					<xsl:choose>
						<xsl:when test="{$period_condition}">
							<xsl:value-of select="@period" />
						</xsl:when>
						<!-- This also covers the case of @period being undefined. -->
						<xsl:otherwise>
							<xsl:message terminate="yes">
								<xsl:text>Attribute "period" must be one of the values {$period_list}.</xsl:text>
							</xsl:message>
						</xsl:otherwise>
					</xsl:choose>
				</xsl:with-param>
	
				<xsl:with-param name="week">
					<xsl:value-of select="@week" />
					<xsl:if test="not( @week )">
						<xsl:message terminate="yes">
							<xsl:text>The "week" attribute is required.</xsl:text>
						</xsl:message>
					</xsl:if>
				</xsl:with-param>
EOT;


// Generate the file header and the wrapper templates.
print<<<EOT
<?xml version="1.0" encoding="utf-8"?>


<!--
	DO NOT EDIT! Automatically generated by ../generate_calendar_dates.php!
	
	Elements and templates for generating teaching period dates. Apart from the wrapper templates, this essentially boils down to a giant parameterised lookup table, which is generated by a script.
-->


<stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

	
	<!--
		Generate a date for a given teaching week in a teaching period, in the specified format. Return the date of the Monday of the week, plus an optional signed offset.
		
		@period: The teaching period for which to generate the date. [required]
		
		@week: The number of the week in the specified teaching period. [required]
		
		@format: How to format the date.
			'day+long-name' => [FNn] [D] [MNn] (e.g., Friday 10 August)
			'day+short-name' => [FNn,*-3] [D] [MNn] (e.g., Fri 10 August)
			'day' => [D] [MNn] (e.g., 10 August)
			'day-short' => [D] [MNn,*-3] (e.g., 10 Aug)
			'day+year' => [D] [MNn], [Y] (e.g., 10 August, 2013)
			'day-short+year' => [D] [MNn,*-3], [Y] (e.g., 10 Aug, 2013)
			'ISO' => [Y0001]-[M01]-[D01] (e.g., 2012-08-10)
			date picture string => Any valid XSLT date picture specification (see http://www.w3.org/TR/xslt20/#date-picture-string).
		
		@offset: A signed offset specified as an XSLT duration, e.g., "P1D" for plus one day, "-P4D" for minus four days.
	-->
	<template name="TeachingPeriodDate" match="TeachingPeriodDate">
		<common>
			<xsl:call-template name="format-teaching-date">
{$shared_parameters}

				<xsl:with-param name="format">
					<xsl:choose>
						<!-- Named date formats. -->
						<xsl:when test="@format = 'day+long-name'">
							<xsl:text>[FNn] [D] [MNn]</xsl:text>
						</xsl:when>
						<xsl:when test="@format = 'day+short-name'">
							<xsl:text>[FNn,*-3] [D] [MNn]</xsl:text>
						</xsl:when>
						<xsl:when test="@format = 'day'">
							<xsl:text>[D] [MNn]</xsl:text>
						</xsl:when>
						<xsl:when test="@format = 'day-short'">
							<xsl:text>[D] [MNn,*-3]</xsl:text>
						</xsl:when>
						<xsl:when test="@format = 'day+year'">
							<xsl:text>[D] [MNn], [Y]</xsl:text>
						</xsl:when>
						<xsl:when test="@format = 'day-short+year'">
							<xsl:text>[D] [MNn,*-3], [Y]</xsl:text>
						</xsl:when>
						<xsl:when test="@format = 'ISO'">
							<xsl:text>[Y0001]-[M01]-[D01]</xsl:text>
						</xsl:when>
						<xsl:otherwise>
							<xsl:value-of select="@format" />
						</xsl:otherwise>
					</xsl:choose>
					<xsl:if test="not( @format )">
						<xsl:text>[Y0001]-[M01]-[D01]</xsl:text>
					</xsl:if>
				</xsl:with-param>
	
				<xsl:with-param name="offset">
					<xsl:value-of select="@offset" />
					<xsl:if test="not( @offset )">
						<xsl:text>P0D</xsl:text>
					</xsl:if>
				</xsl:with-param>
			</xsl:call-template>
		</common>
	</template>
	
	
	<!--
		Generate a date range corresponding to a given teaching week in a teaching period (i.e., Monday to Friday).
		
		@period: The teaching period for which to generate the date. [required]
		
		@week: The number of the week in the specified teaching period. [required]
		
		@format: How to format the month name in the date range.
			'long' => Output the full month name (e.g., August)
			'short' => Output only the first three characters of the month name (e.g., Aug)
		
		@wrap: Whether to wrap the date range across two lines (usually for insertion into a narrow cell in a calendar table).
			'true' [default]
			'false'
	-->
	<template name="TeachingPeriodDateRange" match="TeachingPeriodDateRange">
		<common>
			<xsl:call-template name="format-teaching-date-range">
{$shared_parameters}

				<xsl:with-param name="month-format">
					<xsl:choose>
						<xsl:when test="@format = 'long'">
							<xsl:text>[MNn]</xsl:text>
						</xsl:when>
						<xsl:when test="@format = 'short'">
							<xsl:text>[MNn,*-3]</xsl:text>
						</xsl:when>
						<xsl:otherwise>
							<xsl:message terminate="yes">
								<xsl:text>Attribute "format" must be either "long" or "short", not "</xsl:text>
								<xsl:value-of select="@format" />
								<xsl:text>".</xsl:text>
							</xsl:message>
						</xsl:otherwise>
					</xsl:choose>
				</xsl:with-param>
				
				<!-- Convert @wrap into a boolean value. -->
				<xsl:with-param name="wrap">
					<xsl:value-of select="@wrap = 'yes'" />
				</xsl:with-param>
			</xsl:call-template>
		</common>
	</template>
	
	

EOT;

// Generate the XSLT templates that do all the work. These essentially end up being huge parameterised lookup tables.
generate_template( $first_monday, $periods, 'format-teaching-date' );

generate_template( $first_monday, $periods, 'format-teaching-date-range' );


// Footer boilerplate.
print( "</stylesheet>\n" );

exit;


////////////////////////////////////////////////////////////////////////////////


function generate_template( $first_monday, $periods, $template_name )
{
	// A couple of handy date intervals: four days to the end of the current week,
	// and seven days to the start of next week.
	$plus_four_days = new DateInterval( 'P4D' );
	$plus_seven_days = new DateInterval( 'P7D' );


	// Initial boilerplate for the template.
	switch ( $template_name )
	{
		case 'format-teaching-date':
			print<<<EOT
	<!--
		Generate a date (default Monday) for the specified teaching period and week (or break), using the specified date format, with an optional offset from the Monday of the week. Most of the body of this template is automatically generated by the script ../generate_calendar_dates.php.
		
		See the attributes of the TeachingPeriodDate template above for descriptions of the parameters.
	-->
	<template name="format-teaching-date">
		<common>
			<xsl:param name="period" as="xs:string" />
			<xsl:param name="week" as="xs:string" />
			<xsl:param name="format" as="xs:string" />
			<xsl:param name="offset" as="xs:dayTimeDuration" />
			
			<xsl:choose>

EOT;
			break;
		
		case 'format-teaching-date-range':
			print<<<EOT
	<!--
		Generate a date range for the specified teaching period and week (or break), using the specified month format, with optional wrapping. Most of the body of this template is automatically generated by the script ../generate_calendar_dates.php.
		
		See the attributes of the TeachingPeriodDateRange template above for descriptions of the parameters. \$month-format is derived from @format.
	-->
	<template name="format-teaching-date-range">
		<common>
			<xsl:param name="period" as="xs:string" />
			<xsl:param name="week" as="xs:string" />
			<xsl:param name="month-format" as="xs:string" />
			<xsl:param name="wrap" as="xs:boolean" />
			
			<xsl:choose>

EOT;
			break;
			
		default: // WTF?!?
			print "Unrecognised template name \"$template_name\", terminating.\n";
			exit;
			break;
	} // switch template name

	// Generate XSLT code for each teaching period.
	foreach ( $periods as $period_name => $period_data )
	{
		print<<<EOT
				<xsl:when test="\$period = '{$period_name}'">
					<xsl:choose>

EOT;
		
		$week_start = clone( $first_monday );
		// Jump forward the correct number of weeks to the start of the teaching period.
		$week_start->add( new DateInterval( sprintf( "P%dD", ( $period_data['first_week'] - 1 ) * 7 ) ) );
		
		$week_number = 0;
		$num_breaks = 0;
		
		// Grab the first break week off the front of the list.
		sort( $period_data['break_weeks'] );
		$break_week = array_shift( $period_data['break_weeks'] );
		
		// Generate XSLT code for each teaching week and breaks within the period.
		for ( $week = $period_data['first_week']; $week <= $period_data['last_week']; $week++ )
		{
			$week_end = clone( $week_start );
			$week_end->add( $plus_four_days );
			
			// Handle breaks.
			if ( ( $week >= $break_week['break_starts'] ) && ( $week <= $break_week['break_ends'] ) )
			{
				if ( $week == $break_week['break_starts'] )
				{
					$num_breaks++;
					
					// Work out the end date of the break.
					$break_end = clone( $week_start );
					// Note: +4 days to get to Friday.
					$break_end->add(
						new DateInterval(
							sprintf( "P%dD",  ( ( $break_week['break_ends'] - $break_week['break_starts'] ) * 7 ) + 4 )
						)
					);
					
					switch ( $template_name )
					{
						case 'format-teaching-date':
							generate_date( "B{$num_breaks}", $week_start );
							break;
							
						case 'format-teaching-date-range':
							if ( $week_start->format( 'n' ) == $break_end->format( 'n' ) )
							{
								generate_same_month_date_range( "B{$num_breaks}", $week_start, $break_end );
							} // if break start and break end are in the same month
							else
							{
								generate_different_month_date_range( "B{$num_breaks}", $week_start, $break_end );
							} // else break start and break end are in different months
							break;
							
						default: // WTF?!?
							print "Unrecognised template name \"$template_name\", terminating.\n";
							exit;
							break;
					} // switch template name
				} // if current week == first week of break
				
				if ( $week == $break_week['break_ends'] )
				{
					// Grab the next break week off the front of the list.
					$break_week = array_shift( $period_data['break_weeks'] );
				} // if current week == last week of break
			} // if current week is a break week
			else
			{
				$week_number++;
				
				switch ( $template_name )
				{
					case 'format-teaching-date':
						generate_date( $week_number, $week_start );
						break;
						
					case 'format-teaching-date-range':
						if ( $week_start->format( 'n' ) == $week_end->format( 'n' ) )
						{
							generate_same_month_date_range( $week_number, $week_start, $week_end );
						} // if break start and break end are in the same month
						else
						{
							generate_different_month_date_range( $week_number, $week_start, $week_end );
						} // else break start and break end are in different months
						break;
						
					default: // WTF?!?
						print "Unrecognised template name \"$template_name\", terminating.\n";
						exit;
						break;
				} // switch template name
			} // else normal teaching week
			
			$week_start->add( $plus_seven_days );
		} // for each week
	
		// Terminating boilerplate for this teaching period.
		print<<<EOT
						<xsl:otherwise>
							<xsl:message terminate="yes">
								<xsl:text>Invalid {$period_name} week specification "</xsl:text>
								<xsl:value-of select="\$week" />
								<xsl:text>".</xsl:text>
							</xsl:message>
						</xsl:otherwise>
					</xsl:choose>
				</xsl:when>

EOT;
	} // foreach teaching period

	// Terminating boilerplate for the template.
	print<<<EOT
			</xsl:choose>
		</common>
	</template>

	

EOT;
} // generate_template


////////////////////////////////////////////////////////////////////////////////


function generate_date( $week_spec, $date )
{
	print<<<EOT
						<xsl:when test="\$week = '{$week_spec}'">
							<xsl:value-of select="format-date( xs:date( '{$date->format( 'Y-m-d' )}' ) + \$offset, \$format )" />
						</xsl:when>

EOT;
} // generate_same_month_date_range


////////////////////////////////////////////////////////////////////////////////


function generate_same_month_date_range( $week_spec, $start_date, $end_date )
{
	print<<<EOT
						<xsl:when test="\$week = '{$week_spec}'">
							<xsl:value-of select="format-date( xs:date( '{$start_date->format( 'Y-m-d' )}' ), '[D]' )" />
							<xsl:call-template name="endash" />
							<xsl:value-of select="format-date( xs:date( '{$end_date->format( 'Y-m-d' )}' ), '[D] ' )" />
							<xsl:if test="\$wrap">
								<xsl:call-template name="newline" />
							</xsl:if>
							<xsl:value-of select="format-date( xs:date( '{$end_date->format( 'Y-m-d' )}' ), \$month-format )" />
						</xsl:when>

EOT;
} // generate_same_month_date_range


function generate_different_month_date_range( $week_spec, $start_date, $end_date )
{
	print<<<EOT
						<xsl:when test="\$week = '{$week_spec}'">
							<xsl:value-of select="format-date( xs:date( '{$start_date->format( 'Y-m-d' )}' ), concat( '[D] ', \$month-format ) )" />
							<xsl:if test="\$wrap">
								<xsl:call-template name="newline" />
							</xsl:if>
							<xsl:call-template name="endash" />
							<xsl:value-of select="format-date( xs:date( '{$end_date->format( 'Y-m-d' )}' ), concat( '[D] ', \$month-format ) )" />
						</xsl:when>

EOT;
} // generate_different_month_date_range

?>


            <?php

/*
	This script generates an XSLT include file that contains templates specifying the date ranges for every week of the three main teaching periods through the year (i.e., summer school, first semester, second semester). Simply set the configuration as outlined below and make to regenerate the templates.
*/


/*
	Date of the Monday of the first academic week of the year. Teaching weeks start on Monday, so this is a convenient base point to start from. This will need to be updated annually.
*/
$first_monday = new DateTime( "2018-12-31" );


/*
	Teaching period configuration. This will need to be updated annually. It's easily extensible to a new teaching period simply by adding a new specification for that period. The key should be mixed-case alphanumeric (i.e., no whitespace, no punctuation or other special characters). The components of each period specification are:
	
	first_week:		The academic week number of the first week of the period.
		
	last_week:		The academic week number of the last week of the period.
		
	break_weeks:	A list of breaks that occur during the teaching period.
					Each is specified by the start (break_start) and end
					(break_end) week. If a break is only one week long, then
					break_start and break_end should be equal. If there are no
					breaks in the teaching period, include a single break
					specification with both break_start and break_end set to zero.
					
					The list should ideally be in ascending order, but the
					script doesn't assume this and sorts the list anyway. Weeks
					are numbered by academic week number rather than week within
					the teaching period.
*/
$periods = array(
	'SS' => array(
        'first_week'  => 2,
        'last_week'   => 7,
        'break_weeks' => array(
            array(
                'break_starts' => 0,
                'break_ends'  => 0,
            ),
        ),
    ),
	'S1' => array(
        'first_week'  => 9,
        'last_week'   => 22,
        'break_weeks' => array(
            array(
                'break_starts' => 17,
                'break_ends'  => 17,
            ),
        ),
    ),
	'S2' => array(
        'first_week'  => 28,
        'last_week'   => 41,
        'break_weeks' => array(
            array(
                'break_starts' => 35,
                'break_ends'  => 35,
            ),
        ),
    ),
	'FY' => array(
        'first_week'  => 9,
        'last_week'   => 41,
        'break_weeks' => array(
            array(
                'break_starts' => 17,
                'break_ends'  => 17,
            ),
            array(
                'break_starts' => 23,
                'break_ends'  => 27,
            ),
            array(
                'break_starts' => 35,
                'break_ends'  => 35,
            ),
        ),
    ),
    # This represents the whole year from start to finish.
    'YY' => array(
        'first_week'  => 1,
        'last_week'   => 52,
        'break_weeks' => array(),
    ),
);


// We need a condition to validate the period code in the templates.
$period_condition = sprintf( "( @period = '%s' )", implode( "' ) or ( @period = '", array_keys( $periods ) ) );

// We also a list of valid period code values for the error string.
$period_list = sprintf( '"%s"', implode( '", "', array_keys( $periods ) ) );

// The period and week variables are defined identically in both templates, so
// let's define them just once here to ensure consistency.
$shared_parameters = <<<EOT
				<xsl:with-param name="period">
					<xsl:choose>
						<xsl:when test="{$period_condition}">
							<xsl:value-of select="@period" />
						</xsl:when>
						<!-- This also covers the case of @period being undefined. -->
						<xsl:otherwise>
							<xsl:message terminate="yes">
								<xsl:text>Attribute "period" must be one of the values {$period_list}.</xsl:text>
							</xsl:message>
						</xsl:otherwise>
					</xsl:choose>
				</xsl:with-param>
	
				<xsl:with-param name="week">
					<xsl:value-of select="@week" />
					<xsl:if test="not( @week )">
						<xsl:message terminate="yes">
							<xsl:text>The "week" attribute is required.</xsl:text>
						</xsl:message>
					</xsl:if>
				</xsl:with-param>
EOT;


// Generate the file header and the wrapper templates.
print<<<EOT
<?xml version="1.0" encoding="utf-8"?>


<!--
	DO NOT EDIT! Automatically generated by ../generate_calendar_dates.php!
	
	Elements and templates for generating teaching period dates. Apart from the wrapper templates, this essentially boils down to a giant parameterised lookup table, which is generated by a script.
-->


<stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

	
	<!--
		Generate a date for a given teaching week in a teaching period, in the specified format. Return the date of the Monday of the week, plus an optional signed offset.
		
		@period: The teaching period for which to generate the date. [required]
		
		@week: The number of the week in the specified teaching period. [required]
		
		@format: How to format the date.
			'day+long-name' => [FNn] [D] [MNn] (e.g., Friday 10 August)
			'day+short-name' => [FNn,*-3] [D] [MNn] (e.g., Fri 10 August)
			'day' => [D] [MNn] (e.g., 10 August)
			'day-short' => [D] [MNn,*-3] (e.g., 10 Aug)
			'day+year' => [D] [MNn], [Y] (e.g., 10 August, 2013)
			'day-short+year' => [D] [MNn,*-3], [Y] (e.g., 10 Aug, 2013)
			'ISO' => [Y0001]-[M01]-[D01] (e.g., 2012-08-10)
			date picture string => Any valid XSLT date picture specification (see http://www.w3.org/TR/xslt20/#date-picture-string).
		
		@offset: A signed offset specified as an XSLT duration, e.g., "P1D" for plus one day, "-P4D" for minus four days.
	-->
	<template name="TeachingPeriodDate" match="TeachingPeriodDate">
		<common>
			<xsl:call-template name="format-teaching-date">
{$shared_parameters}

				<xsl:with-param name="format">
					<xsl:choose>
						<!-- Named date formats. -->
						<xsl:when test="@format = 'day+long-name'">
							<xsl:text>[FNn] [D] [MNn]</xsl:text>
						</xsl:when>
						<xsl:when test="@format = 'day+short-name'">
							<xsl:text>[FNn,*-3] [D] [MNn]</xsl:text>
						</xsl:when>
						<xsl:when test="@format = 'day'">
							<xsl:text>[D] [MNn]</xsl:text>
						</xsl:when>
						<xsl:when test="@format = 'day-short'">
							<xsl:text>[D] [MNn,*-3]</xsl:text>
						</xsl:when>
						<xsl:when test="@format = 'day+year'">
							<xsl:text>[D] [MNn], [Y]</xsl:text>
						</xsl:when>
						<xsl:when test="@format = 'day-short+year'">
							<xsl:text>[D] [MNn,*-3], [Y]</xsl:text>
						</xsl:when>
						<xsl:when test="@format = 'ISO'">
							<xsl:text>[Y0001]-[M01]-[D01]</xsl:text>
						</xsl:when>
						<xsl:otherwise>
							<xsl:value-of select="@format" />
						</xsl:otherwise>
					</xsl:choose>
					<xsl:if test="not( @format )">
						<xsl:text>[Y0001]-[M01]-[D01]</xsl:text>
					</xsl:if>
				</xsl:with-param>
	
				<xsl:with-param name="offset">
					<xsl:value-of select="@offset" />
					<xsl:if test="not( @offset )">
						<xsl:text>P0D</xsl:text>
					</xsl:if>
				</xsl:with-param>
			</xsl:call-template>
		</common>
	</template>
	
	
	<!--
		Generate a date range corresponding to a given teaching week in a teaching period (i.e., Monday to Friday).
		
		@period: The teaching period for which to generate the date. [required]
		
		@week: The number of the week in the specified teaching period. [required]
		
		@format: How to format the month name in the date range.
			'long' => Output the full month name (e.g., August)
			'short' => Output only the first three characters of the month name (e.g., Aug)
		
		@wrap: Whether to wrap the date range across two lines (usually for insertion into a narrow cell in a calendar table).
			'true' [default]
			'false'
	-->
	<template name="TeachingPeriodDateRange" match="TeachingPeriodDateRange">
		<common>
			<xsl:call-template name="format-teaching-date-range">
{$shared_parameters}

				<xsl:with-param name="month-format">
					<xsl:choose>
						<xsl:when test="@format = 'long'">
							<xsl:text>[MNn]</xsl:text>
						</xsl:when>
						<xsl:when test="@format = 'short'">
							<xsl:text>[MNn,*-3]</xsl:text>
						</xsl:when>
						<xsl:otherwise>
							<xsl:message terminate="yes">
								<xsl:text>Attribute "format" must be either "long" or "short", not "</xsl:text>
								<xsl:value-of select="@format" />
								<xsl:text>".</xsl:text>
							</xsl:message>
						</xsl:otherwise>
					</xsl:choose>
				</xsl:with-param>
				
				<!-- Convert @wrap into a boolean value. -->
				<xsl:with-param name="wrap">
					<xsl:value-of select="@wrap = 'yes'" />
				</xsl:with-param>
			</xsl:call-template>
		</common>
	</template>
	
	

EOT;

// Generate the XSLT templates that do all the work. These essentially end up being huge parameterised lookup tables.
generate_template( $first_monday, $periods, 'format-teaching-date' );

generate_template( $first_monday, $periods, 'format-teaching-date-range' );


// Footer boilerplate.
print( "</stylesheet>\n" );

exit;


////////////////////////////////////////////////////////////////////////////////


function generate_template( $first_monday, $periods, $template_name )
{
	// A couple of handy date intervals: four days to the end of the current week,
	// and seven days to the start of next week.
	$plus_four_days = new DateInterval( 'P4D' );
	$plus_seven_days = new DateInterval( 'P7D' );


	// Initial boilerplate for the template.
	switch ( $template_name )
	{
		case 'format-teaching-date':
			print<<<EOT
	<!--
		Generate a date (default Monday) for the specified teaching period and week (or break), using the specified date format, with an optional offset from the Monday of the week. Most of the body of this template is automatically generated by the script ../generate_calendar_dates.php.
		
		See the attributes of the TeachingPeriodDate template above for descriptions of the parameters.
	-->
	<template name="format-teaching-date">
		<common>
			<xsl:param name="period" as="xs:string" />
			<xsl:param name="week" as="xs:string" />
			<xsl:param name="format" as="xs:string" />
			<xsl:param name="offset" as="xs:dayTimeDuration" />
			
			<xsl:choose>

EOT;
			break;
		
		case 'format-teaching-date-range':
			print<<<EOT
	<!--
		Generate a date range for the specified teaching period and week (or break), using the specified month format, with optional wrapping. Most of the body of this template is automatically generated by the script ../generate_calendar_dates.php.
		
		See the attributes of the TeachingPeriodDateRange template above for descriptions of the parameters. \$month-format is derived from @format.
	-->
	<template name="format-teaching-date-range">
		<common>
			<xsl:param name="period" as="xs:string" />
			<xsl:param name="week" as="xs:string" />
			<xsl:param name="month-format" as="xs:string" />
			<xsl:param name="wrap" as="xs:boolean" />
			
			<xsl:choose>

EOT;
			break;
			
		default: // WTF?!?
			print "Unrecognised template name \"$template_name\", terminating.\n";
			exit;
			break;
	} // switch template name

	// Generate XSLT code for each teaching period.
	foreach ( $periods as $period_name => $period_data )
	{
		print<<<EOT
				<xsl:when test="\$period = '{$period_name}'">
					<xsl:choose>

EOT;
		
		$week_start = clone( $first_monday );
		// Jump forward the correct number of weeks to the start of the teaching period.
		$week_start->add( new DateInterval( sprintf( "P%dD", ( $period_data['first_week'] - 1 ) * 7 ) ) );
		
		$week_number = 0;
		$num_breaks = 0;
		
		// Grab the first break week off the front of the list.
		sort( $period_data['break_weeks'] );
		$break_week = array_shift( $period_data['break_weeks'] );
		
		// Generate XSLT code for each teaching week and breaks within the period.
		for ( $week = $period_data['first_week']; $week <= $period_data['last_week']; $week++ )
		{
			$week_end = clone( $week_start );
			$week_end->add( $plus_four_days );
			
			// Handle breaks.
			if ( ( $week >= $break_week['break_starts'] ) && ( $week <= $break_week['break_ends'] ) )
			{
				if ( $week == $break_week['break_starts'] )
				{
					$num_breaks++;
					
					// Work out the end date of the break.
					$break_end = clone( $week_start );
					// Note: +4 days to get to Friday.
					$break_end->add(
						new DateInterval(
							sprintf( "P%dD",  ( ( $break_week['break_ends'] - $break_week['break_starts'] ) * 7 ) + 4 )
						)
					);
					
					switch ( $template_name )
					{
						case 'format-teaching-date':
							generate_date( "B{$num_breaks}", $week_start );
							break;
							
						case 'format-teaching-date-range':
							if ( $week_start->format( 'n' ) == $break_end->format( 'n' ) )
							{
								generate_same_month_date_range( "B{$num_breaks}", $week_start, $break_end );
							} // if break start and break end are in the same month
							else
							{
								generate_different_month_date_range( "B{$num_breaks}", $week_start, $break_end );
							} // else break start and break end are in different months
							break;
							
						default: // WTF?!?
							print "Unrecognised template name \"$template_name\", terminating.\n";
							exit;
							break;
					} // switch template name
				} // if current week == first week of break
				
				if ( $week == $break_week['break_ends'] )
				{
					// Grab the next break week off the front of the list.
					$break_week = array_shift( $period_data['break_weeks'] );
				} // if current week == last week of break
			} // if current week is a break week
			else
			{
				$week_number++;
				
				switch ( $template_name )
				{
					case 'format-teaching-date':
						generate_date( $week_number, $week_start );
						break;
						
					case 'format-teaching-date-range':
						if ( $week_start->format( 'n' ) == $week_end->format( 'n' ) )
						{
							generate_same_month_date_range( $week_number, $week_start, $week_end );
						} // if break start and break end are in the same month
						else
						{
							generate_different_month_date_range( $week_number, $week_start, $week_end );
						} // else break start and break end are in different months
						break;
						
					default: // WTF?!?
						print "Unrecognised template name \"$template_name\", terminating.\n";
						exit;
						break;
				} // switch template name
			} // else normal teaching week
			
			$week_start->add( $plus_seven_days );
		} // for each week
	
		// Terminating boilerplate for this teaching period.
		print<<<EOT
						<xsl:otherwise>
							<xsl:message terminate="yes">
								<xsl:text>Invalid {$period_name} week specification "</xsl:text>
								<xsl:value-of select="\$week" />
								<xsl:text>".</xsl:text>
							</xsl:message>
						</xsl:otherwise>
					</xsl:choose>
				</xsl:when>

EOT;
	} // foreach teaching period

	// Terminating boilerplate for the template.
	print<<<EOT
			</xsl:choose>
		</common>
	</template>

	

EOT;
} // generate_template


////////////////////////////////////////////////////////////////////////////////


function generate_date( $week_spec, $date )
{
	print<<<EOT
						<xsl:when test="\$week = '{$week_spec}'">
							<xsl:value-of select="format-date( xs:date( '{$date->format( 'Y-m-d' )}' ) + \$offset, \$format )" />
						</xsl:when>

EOT;
} // generate_same_month_date_range


////////////////////////////////////////////////////////////////////////////////


function generate_same_month_date_range( $week_spec, $start_date, $end_date )
{
	print<<<EOT
						<xsl:when test="\$week = '{$week_spec}'">
							<xsl:value-of select="format-date( xs:date( '{$start_date->format( 'Y-m-d' )}' ), '[D]' )" />
							<xsl:call-template name="endash" />
							<xsl:value-of select="format-date( xs:date( '{$end_date->format( 'Y-m-d' )}' ), '[D] ' )" />
							<xsl:if test="\$wrap">
								<xsl:call-template name="newline" />
							</xsl:if>
							<xsl:value-of select="format-date( xs:date( '{$end_date->format( 'Y-m-d' )}' ), \$month-format )" />
						</xsl:when>

EOT;
} // generate_same_month_date_range


function generate_different_month_date_range( $week_spec, $start_date, $end_date )
{
	print<<<EOT
						<xsl:when test="\$week = '{$week_spec}'">
							<xsl:value-of select="format-date( xs:date( '{$start_date->format( 'Y-m-d' )}' ), concat( '[D] ', \$month-format ) )" />
							<xsl:if test="\$wrap">
								<xsl:call-template name="newline" />
							</xsl:if>
							<xsl:call-template name="endash" />
							<xsl:value-of select="format-date( xs:date( '{$end_date->format( 'Y-m-d' )}' ), concat( '[D] ', \$month-format ) )" />
						</xsl:when>

EOT;
} // generate_different_month_date_range

?>
 */
 /*
+	Date of the Monday of the first academic week of the year. Teaching weeks start on Monday, so this is a convenient base point to start from. This will need to be updated annually.
+	Date of the Monday of the first academic week of the year (ISO 8601). Teaching weeks start on Monday, so this is a convenient base point to start from. Note that this is always for the *current* year!
 */
+$first_monday = new DateTime( "2018-12-31" );
+$first_monday = new DateTime();
+$first_monday->setISODate(date("Y"), 1);
 /*
 	Teaching period configuration. This will need to be updated annually. It's easily extensible to a new teaching period simply by adding a new specification for that period. The key should be mixed-case alphanumeric (i.e., no whitespace, no punctuation or other special characters). The components of each period specification are:

Show line notes below