<?php
/*
Plugin Name: Date Pagination
Version: 0.2
Plugin URI: http://keesiemeijer.wordpress.com/date-pagination
Description: This plugin lets WordPress theme developers paginate posts by year, month or day in theme template files.
Author: keesiemijer
Author URI:
License: GPL v2
*/

// load functions on the front end.
if ( !is_admin() ) {

	add_filter( 'query_vars', 'km_dp_date_pagination_query_var' );

	/**
	 * Adds query var 'date_pagination_type' to the public query vars
	 *
	 * @since 0.1
	 *
	 * @param array   $query_vars
	 * @return array
	 */
	function km_dp_date_pagination_query_var( $query_vars ) {

		$query_vars[] = 'date_pagination_type';

		return $query_vars;
	}


	add_action( 'pre_get_posts', 'km_dp_date_pagination_pre_get_posts', 99 );

	/**
	 * Resets date query vars if 'date_pagination_type' query var is used.
	 *
	 * @since 0.1
	 *
	 * @param object  $query Query object.
	 * @return void
	 */
	function km_dp_date_pagination_pre_get_posts( $query ) {

		if ( is_date() )
			return;

		if ( isset( $query->query_vars['date_pagination_type'] ) ) {

			$type = $query->query_vars['date_pagination_type'];

			if ( km_dp_date_pagination_is_valid_type( $type ) ) {

				$reset_query_vars =  array(
					'second' , 'minute', 'hour',
					'day', 'monthnum', 'year',
					'w', 'm',
				);

				// reset date query vars
				foreach ( $reset_query_vars as $var ) {
					$query->set( $var, '' );
				}

				// disable paging just for good measure
				$query->set( 'nopaging', true );
			}
		}
	}


	add_filter( 'posts_clauses', 'km_dp_date_pagination_posts_clauses', 99, 2 );

	/**
	 * Sets the sql clauses if query var 'date_pagination_type' is used.
	 *
	 * @since 0.1
	 *
	 * @param array   $clauses Post clauses.
	 * @param object  $query   Query Object.
	 * @return array Post clauses
	 */
	function km_dp_date_pagination_posts_clauses( $clauses, $query ) {
		global $wpdb;

		if ( is_date() )
			return $clauses;

		// check if query var 'date_pagination_type' is used for query
		if ( !isset( $query->query_vars['date_pagination_type'] ) )
			return $clauses;

		$type = $query->query_vars['date_pagination_type'];

		if ( km_dp_date_pagination_is_valid_type( $type ) ) {

			$select = 'YEAR(post_date) AS `year`';
			$groupby = 'YEAR(post_date)';

			if ( $type == 'monthly' || $type == 'daily' ) {
				$select .= ', MONTH(post_date) AS `month`';
				$groupby .= ', MONTH(post_date)';
			}

			if ( $type == 'daily' ) {
				$select .= ', DAYOFMONTH(post_date) AS `dayofmonth`';
				$groupby .= ', DAYOFMONTH(post_date)';
			}

			$date_query = "SELECT $select, count(ID) as posts FROM $wpdb->posts " . $clauses['join'] . " WHERE 1=1". $clauses['where'] ." GROUP BY $groupby ORDER BY " . $clauses['orderby'];

			// todo: should this query be cached? Normally used once per page (main or custom paginated query)?

			// get all (paginated) date pages for this query
			$dates = $wpdb->get_results( $date_query );

			$dates_2 = array();

			foreach ( $dates as $key => $_date ) {


				if ( ( ( $key + 1 ) % 2 ) == 0 ) {
					echo $_date->month . '|';

					$dates_2[$key-1]->month = array( $dates_2[$key-1]->month, $_date->month );
					$dates_2[$key-1]->posts = $dates_2[$key-1]->posts + $_date->posts;
					if ( $dates_2[$key-1]->year !== $_date->year ) {
						$dates_2[$key-1]->year = array( $dates_2[$key-1]->year, $_date->year );
					}
				} else {
					$dates_2[$key] = $_date;
				}
				$temp_date = $_date;
			}

			$dates = array_values( $dates_2 );

			if ( $dates ) {
				// count of dates gets set as max_num_pages for the query
				$page_count = count( $dates );

				// add new max_num_pages to the query object
				$query->set( 'date_pagination_max_num_pages', $page_count );

				// set max_num_pages to date pagination max_num_pages
				add_filter( 'the_posts', 'km_dp_date_pagination_max_num_pages', 99, 2 );

				// current page
				if ( get_query_var( 'paged' ) ) { $paged = get_query_var( 'paged' ); }
				elseif ( get_query_var( 'page' ) ) { $paged = get_query_var( 'page' ); }
				else { $paged = 1; }

				// don't return posts if a paginated page is over the max_num_pages
				if ( $paged > $page_count )
					$clauses['where'] .= " AND 1=0";

				// get the date for the current (paginated) page.
				$start = (int) $paged-1;
				$date = array_slice( (array) $dates, $start, 1 );

				// add current object to query
				$query->set( 'date_pagination_current', $date );

				// add next object to query
				$next = array_slice( (array) $dates, $start+1, 1 );
				$query->set( 'date_pagination_next', $next );

				// add previous object to query
				if ( $start > 0 ) {
					$prev = array_slice( (array) $dates, $start-1, 1 );
					$query->set( 'date_pagination_prev', $prev );
				} else {
					$query->set( 'date_pagination_prev', array() );
				}

				if ( $date ) {

					// no pagination needed for this query
					$clauses['limits'] = '';

					// year sql
					if ( isset( $date[0]->year ) ) {
						if ( !is_array( $date[0]->year ) ) {
							$clauses['where'] .= " AND YEAR($wpdb->posts.post_date)='" . $date[0]->year . "'";
						}else {
							foreach ( $date[0]->year as $key => $year ) {
								$operator = !$key ? ' AND' : ' OR';
								$clauses['where'] .= $operator . " (YEAR($wpdb->posts.post_date)='" . $date[0]->year[$key] . "' AND MONTH($wpdb->posts.post_date)='" . $date[0]->month[$key] . "')";
							}
						}
					}

					// month sql
					if ( isset( $date[0]->month ) ) {
						if ( !is_array( $date[0]->month ) ) {
							$clauses['where'] .= " AND MONTH($wpdb->posts.post_date)='" . $date[0]->month . "'";
						} else {
							if ( !is_array( $date[0]->year ) ) {
								// month already queried by year and month
								$clauses['where'] .= " AND ( MONTH($wpdb->posts.post_date)='" . $date[0]->month[0] . "' OR MONTH($wpdb->posts.post_date)='" . $date[0]->month[1] . "')";
							}
						}

					}

					// day sql
					if ( isset( $date[0]->dayofmonth ) )
						$clauses['where'] .= " AND DAYOFMONTH($wpdb->posts.post_date)='" . $date[0]->dayofmonth . "'";
				}
			}
		}

		return $clauses;
	}


	/**
	 * Sets the max_num_pages.
	 *
	 * @since 0.1
	 *
	 * @param object  $query Query Object.
	 * @return array Array with post objects
	 */
	function km_dp_date_pagination_max_num_pages( $posts, $query ) {
		$max_num_pages = $query->get( 'date_pagination_max_num_pages' );

		if ( !empty( $max_num_pages ) )
			$query->max_num_pages = $max_num_pages;

		return $posts;
	}


	/**
	 * Validates date types
	 *
	 * @since 0.1
	 *
	 * @param string  $type
	 * @return bool True if type is valid.
	 */
	function km_dp_date_pagination_is_valid_type( $type ) {

		if ( is_string( $type ) ) {
			if ( in_array( $type, array( 'yearly', 'monthly', 'daily' ) ) )
				return true;
		}

		return false;
	}


	/**
	 * Returns next date label from query.
	 *
	 * @since 0.1
	 *
	 * @param object  $query  WP_Query Object.
	 * @param string  $format Date format.
	 * @return string Formatted date or empty string.
	 */
	function km_dp_get_next_date_label( $format = '', $query = 0  ) {
		return km_dp_date_pagination_get_date( $format, $query );
	}


	/**
	 * Returns previous date label from query.
	 *
	 * @since 0.1
	 *
	 * @param object  $query  WP_Query Object.
	 * @param string  $format Date format.
	 * @return string Formatted date or empty string.
	 */
	function km_dp_get_previous_date_label( $format = '', $query = 0 ) {
		return km_dp_date_pagination_get_date( $format, $query, true );
	}


	/**
	 * Returns current date label from query.
	 *
	 * @since 0.1
	 *
	 * @param object  $query  WP_Query Object.
	 * @param string  $format Date format.
	 * @return string Formatted date or empty string.
	 */
	function km_dp_get_current_date_label( $format = '', $query = 0 ) {
		return km_dp_date_pagination_get_date( $format, $query, 'current' );
	}


	/**
	 * Returns a formatted date from a query.
	 *
	 * @since 0.1
	 *
	 * @param object  $query     WP_Query Object.
	 * @param string  $format    Date format.
	 * @param string  $previous. Previous or next date.
	 * @return string Formatted date or empty string.
	 */
	function km_dp_date_pagination_get_date( $format = '', $query = 0, $previous = 0 ) {

		$date = '';

		if ( is_date() )
			return $date;

		if ( !$query ) {
			global $wp_query;
			$query = $wp_query;
		}

		if ( !is_a( (object) $query, 'WP_Query' ) )
			return $date;

		$type = $query->get( 'date_pagination_type' );

		if ( !empty( $type ) && km_dp_date_pagination_is_valid_type( $type ) ) {

			$next_prev = 'date_pagination_next';

			if ( $previous ) {
				$next_prev = 'date_pagination_prev';

				if ( $previous === 'current' ) {
					$next_prev = 'date_pagination_current';
				}
			}

			$date_obj = $query->get( $next_prev );

			if ( !empty( $date_obj ) ) {

				$year = ( isset( $date_obj[0]->year ) ) ? absint( $date_obj[0]->year ): 0;
				$month = ( isset( $date_obj[0]->month ) ) ? absint( $date_obj[0]->month ): 0;
				$day = ( isset( $date_obj[0]->dayofmonth ) ) ? absint( $date_obj[0]->dayofmonth ): 0;

				if ( ( $type == 'yearly' ) && $year ) {
					$date = $year . '-01-01';
					$format = ( '' != $format ) ? (string) $format : 'Y';
				}

				if ( ( $type == 'monthly' ) && $year && $month ) {
					$date = $year . '-' . zeroise( $month, 2 ) . '-01';
					$format = ( '' != $format ) ? (string) $format : 'F Y';
				}

				if ( ( $type == 'daily' )  && $year && $month && $day ) {
					$date = $year . '-' . zeroise( $month, 2 ) . zeroise( $day, 2 );
					$format = ( '' != $format ) ? (string) $format : ' F j, Y';
				}

			}
		}

		return ( '' != $date ) ? mysql2date( $format, $date . ' 00:00:00' ) : '';
	}


} // if( !is_admin() )