<?php
/**
 * Winner drawing admin page: draw a random winner per day (optionally only
 * among fully-correct entries), toggle/clear winner flags, list winners and
 * export them as CSV.
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

class ADVK_Winners {

	public function hooks() {
		add_action( 'admin_menu', array( $this, 'add_menu' ) );
		add_action( 'admin_post_advk_draw_winner', array( $this, 'handle_draw' ) );
		add_action( 'admin_post_advk_toggle_winner', array( $this, 'handle_toggle' ) );
		add_action( 'admin_post_advk_clear_winners', array( $this, 'handle_clear' ) );
		add_action( 'admin_post_advk_export_winners', array( $this, 'export_csv' ) );
		add_action( 'admin_post_advk_notify_winners', array( $this, 'handle_notify' ) );
	}

	/** @return array Notified winners: [ entry_id => 'Y-m-d H:i' ]. */
	private static function get_notified() {
		$m = get_option( 'advk_notified', array() );
		return is_array( $m ) ? $m : array();
	}

	/** @param array $map Notified map to persist. */
	private static function save_notified( $map ) {
		update_option( 'advk_notified', $map, false );
	}

	/**
	 * Timestamp a winner was notified, or '' when not yet.
	 *
	 * @param int $id Entry id.
	 * @return string
	 */
	public static function notified_at( $id ) {
		$m = self::get_notified();
		return isset( $m[ (int) $id ] ) ? (string) $m[ (int) $id ] : '';
	}

	/**
	 * Send the winner e-mail to all winners (optionally a single day) that have
	 * not been notified yet, and record the notification.
	 */
	public function handle_notify() {
		if ( ! current_user_can( 'manage_options' ) ) {
			wp_die( esc_html__( 'Keine Berechtigung.', 'adventura-interactive-advent-calendar' ) );
		}
		check_admin_referer( 'advk_notify_winners' );

		$day  = isset( $_POST['day'] ) ? (int) $_POST['day'] : 0;
		$opts = ADVK_Settings::get_options();

		$winners = ADVK_Entries::query(
			array(
				'per_page'     => 100000,
				'offset'       => 0,
				'day'          => ( $day >= 1 && $day <= ADVK_Data::door_count() ) ? $day : 0,
				'winners_only' => true,
			)
		);

		$sitename    = wp_specialchars_decode( get_bloginfo( 'name' ), ENT_QUOTES );
		$subject_tpl = (string) $opts['winner_email_subject'];
		$body_tpl    = (string) $opts['winner_email_body'];
		$headers     = ADVK_Emails::mail_headers( $opts, true );

		$notified = self::get_notified();
		$sent     = 0;
		foreach ( $winners as $w ) {
			if ( isset( $notified[ (int) $w->id ] ) || ! is_email( $w->email ) ) {
				continue; // already notified or no valid address
			}
			$prize   = self::prize_for_winner( (int) $w->day, (int) $w->id );
			$replace = array(
				'{first}'    => $w->first_name,
				'{last}'     => $w->last_name,
				'{day}'      => (int) $w->day,
				'{prize}'    => '' !== $prize ? $prize : $this->prize_titles_for_day( (int) $w->day ),
				'{losnr}'    => $w->losnr,
				'{sitename}' => $sitename,
			);
			$subject = strtr( $subject_tpl, $replace );
			$body    = strtr( $body_tpl, $replace );
			$html    = ADVK_Emails::html_wrap( $subject, $body, $opts );

			if ( wp_mail( $w->email, $subject, $html, $headers ) ) {
				$notified[ (int) $w->id ] = wp_date( 'Y-m-d H:i' );
				++$sent;
			}
		}
		self::save_notified( $notified );

		$this->redirect_back(
			sprintf(
				/* translators: %d: number of winner e-mails sent. */
				_n( '%d Gewinner benachrichtigt.', '%d Gewinner benachrichtigt.', $sent, 'adventura-interactive-advent-calendar' ),
				$sent
			)
		);
	}

	/**
	 * Fallback prize label for a day (all prize titles) when no specific prize
	 * was assigned to the winner (e.g. manually flagged winners).
	 *
	 * @param int $day Door day.
	 * @return string
	 */
	private function prize_titles_for_day( $day ) {
		$door = $this->door_by_day( $day );
		if ( ! $door || empty( $door['prizes'] ) ) {
			return '';
		}
		$titles = array();
		foreach ( $door['prizes'] as $p ) {
			$t = isset( $p['title'] ) ? trim( (string) $p['title'] ) : '';
			if ( '' !== $t ) {
				$titles[] = $t;
			}
		}
		return implode( ', ', $titles );
	}

	public function add_menu() {
		add_submenu_page(
			ADVK_Dashboard::SLUG,
			__( 'Auslosung', 'adventura-interactive-advent-calendar' ),
			__( 'Auslosung', 'adventura-interactive-advent-calendar' ),
			'manage_options',
			'advk-winners',
			array( $this, 'render_page' )
		);
	}

	private function redirect_back( $notice = '' ) {
		$url = admin_url( 'admin.php?page=advk-winners' );
		if ( $notice ) {
			$url = add_query_arg( 'advk_notice', rawurlencode( $notice ), $url );
		}
		wp_safe_redirect( $url );
		exit;
	}

	public function handle_draw() {
		if ( ! current_user_can( 'manage_options' ) ) {
			wp_die( esc_html__( 'Keine Berechtigung.', 'adventura-interactive-advent-calendar' ) );
		}
		check_admin_referer( 'advk_draw_winner' );

		$day          = isset( $_POST['day'] ) ? (int) $_POST['day'] : 0;
		$correct_only = ! empty( $_POST['correct_only'] );

		if ( $day < 1 || $day > ADVK_Data::door_count() ) {
			$this->redirect_back( __( 'Bitte ein Türchen wählen.', 'adventura-interactive-advent-calendar' ) );
		}

		$door         = $this->door_by_day( $day );
		$prizes       = ( $door && isset( $door['prizes'] ) && is_array( $door['prizes'] ) ) ? $door['prizes'] : array();
		$winner_count = ( $door && isset( $door['winnerCount'] ) ) ? (int) $door['winnerCount'] : 1;
		if ( $winner_count < 1 ) {
			$winner_count = 1;
		}

		$opts         = ADVK_Settings::get_options();
		$direct_min   = (int) $opts['donation_direct_min'];
		$direct_prize = (string) $opts['donation_direct_prize'];

		$eligible  = ADVK_Entries::eligible_ids( $day, $correct_only );
		$donations = ADVK_Entries::get_donations();
		if ( empty( $eligible ) ) {
			/* translators: %d: door day number (1–24). */
			$this->redirect_back( sprintf( __( 'Keine passenden Teilnahmen für Tag %d.', 'adventura-interactive-advent-calendar' ), $day ) );
		}

		$map         = self::get_prize_map();
		$map[ $day ] = isset( $map[ $day ] ) && is_array( $map[ $day ] ) ? $map[ $day ] : array();

		// 1) Direct wins: any donation of at least the threshold guarantees the
		//    configured direct-win prize (independent of the random draw).
		$direct = array();
		$rest   = array();
		foreach ( $eligible as $id ) {
			$amt = isset( $donations[ $id ] ) ? (float) $donations[ $id ] : 0.0;
			if ( $direct_min > 0 && $amt >= $direct_min ) {
				$direct[] = $id;
			} else {
				$rest[] = $id;
			}
		}
		foreach ( $direct as $id ) {
			ADVK_Entries::set_winner( $id, 1 );
			$map[ $day ][ $id ] = $direct_prize;
		}

		// 2) Regular draw from the remaining pool. A donation (> 0) adds a second
		//    lot, so donors are twice as likely to be drawn (without replacement).
		$pool = array();
		foreach ( $rest as $id ) {
			$pool[] = $id;
			if ( isset( $donations[ $id ] ) && (float) $donations[ $id ] > 0 ) {
				$pool[] = $id; // extra lot
			}
		}
		$picked = array();
		while ( count( $picked ) < $winner_count && ! empty( $pool ) ) {
			$k  = wp_rand( 0, count( $pool ) - 1 );
			$id = (int) $pool[ $k ];
			$picked[] = $id;
			$pool     = array_values(
				array_filter( $pool, function ( $x ) use ( $id ) { return (int) $x !== $id; } )
			);
		}

		// Distribute the door's prizes over the drawn winners (round-robin).
		$titles = array();
		foreach ( $prizes as $p ) {
			$title = isset( $p['title'] ) ? trim( (string) $p['title'] ) : '';
			if ( '' !== $title ) {
				$titles[] = $title;
			}
		}
		$wc = max( 1, count( $picked ) );
		$byWinner = array();
		for ( $j = 0; $j < count( $titles ); $j++ ) {
			$byWinner[ $j % $wc ][] = $titles[ $j ];
		}
		foreach ( $picked as $wi => $id ) {
			ADVK_Entries::set_winner( $id, 1 );
			$map[ $day ][ $id ] = isset( $byWinner[ $wi ] ) ? implode( ', ', $byWinner[ $wi ] ) : '';
		}

		self::save_prize_map( $map );

		$this->redirect_back(
			sprintf(
				/* translators: 1: total winners, 2: door day, 3: number of direct wins. */
				__( '%1$d Gewinner für Tag %2$d gezogen (davon %3$d Direktgewinne).', 'adventura-interactive-advent-calendar' ),
				count( $picked ) + count( $direct ),
				$day,
				count( $direct )
			)
		);
	}

	/**
	 * Full door data for a day (from the authoritative calendar), or null.
	 *
	 * @param int $day Door day.
	 * @return array|null
	 */
	private function door_by_day( $day ) {
		foreach ( ADVK_Data::get_calendar() as $d ) {
			if ( (int) $d['day'] === (int) $day ) {
				return $d;
			}
		}
		return null;
	}

	/** @return array Winner→prize map: [ day => [ entry_id => prize label ] ]. */
	private static function get_prize_map() {
		$m = get_option( 'advk_prize_map', array() );
		return is_array( $m ) ? $m : array();
	}

	/** @param array $map Winner→prize map to persist. */
	private static function save_prize_map( $map ) {
		update_option( 'advk_prize_map', $map, false );
	}

	/**
	 * Prize label assigned to a winner entry (empty when none stored).
	 *
	 * @param int $day      Door day.
	 * @param int $entry_id Entry id.
	 * @return string
	 */
	public static function prize_for_winner( $day, $entry_id ) {
		$m = self::get_prize_map();
		return isset( $m[ (int) $day ][ (int) $entry_id ] ) ? (string) $m[ (int) $day ][ (int) $entry_id ] : '';
	}

	/**
	 * Assign (or, with an empty label, clear) the prize for a winner entry.
	 * Used when a winner is picked/edited by hand from the entries list.
	 *
	 * @param int    $day      Door day.
	 * @param int    $entry_id Entry id.
	 * @param string $label    Prize label ('' clears the assignment).
	 */
	public static function set_prize_for_winner( $day, $entry_id, $label ) {
		$day      = (int) $day;
		$entry_id = (int) $entry_id;
		$label    = (string) $label;

		$m = self::get_prize_map();
		if ( ! isset( $m[ $day ] ) || ! is_array( $m[ $day ] ) ) {
			$m[ $day ] = array();
		}
		if ( '' === $label ) {
			unset( $m[ $day ][ $entry_id ] );
		} else {
			$m[ $day ][ $entry_id ] = $label;
		}
		if ( empty( $m[ $day ] ) ) {
			unset( $m[ $day ] );
		}
		self::save_prize_map( $m );
	}

	/**
	 * Remove any stored prize assignment for a winner entry.
	 *
	 * @param int $day      Door day.
	 * @param int $entry_id Entry id.
	 */
	public static function clear_prize_for_winner( $day, $entry_id ) {
		self::set_prize_for_winner( $day, $entry_id, '' );
	}

	public function handle_toggle() {
		if ( ! current_user_can( 'manage_options' ) ) {
			wp_die( esc_html__( 'Keine Berechtigung.', 'adventura-interactive-advent-calendar' ) );
		}
		check_admin_referer( 'advk_toggle_winner' );

		$id   = isset( $_POST['id'] ) ? (int) $_POST['id'] : 0;
		$flag = ! empty( $_POST['flag'] ) ? 1 : 0;
		if ( $id ) {
			ADVK_Entries::set_winner( $id, $flag );
		}
		$this->redirect_back( $flag ? __( 'Als Gewinner markiert.', 'adventura-interactive-advent-calendar' ) : __( 'Gewinner-Markierung entfernt.', 'adventura-interactive-advent-calendar' ) );
	}

	public function handle_clear() {
		if ( ! current_user_can( 'manage_options' ) ) {
			wp_die( esc_html__( 'Keine Berechtigung.', 'adventura-interactive-advent-calendar' ) );
		}
		check_admin_referer( 'advk_clear_winners' );

		$day = isset( $_POST['day'] ) ? (int) $_POST['day'] : 0;
		ADVK_Entries::clear_winners( $day );

		$map      = self::get_prize_map();
		$notified = self::get_notified();
		if ( $day >= 1 && $day <= ADVK_Data::door_count() ) {
			// Drop notified flags for this day's entries too.
			$ids = ADVK_Entries::query( array( 'per_page' => 100000, 'offset' => 0, 'day' => $day ) );
			foreach ( $ids as $row ) {
				unset( $notified[ (int) $row->id ] );
			}
			unset( $map[ $day ] );
		} else {
			$map      = array();
			$notified = array();
		}
		self::save_prize_map( $map );
		self::save_notified( $notified );
		$this->redirect_back(
			$day
				/* translators: %d: door day number (1–24). */
				? sprintf( __( 'Gewinner für Tag %d zurückgesetzt.', 'adventura-interactive-advent-calendar' ), $day )
				: __( 'Alle Gewinner zurückgesetzt.', 'adventura-interactive-advent-calendar' )
		);
	}

	public function render_page() {
		if ( ! current_user_can( 'manage_options' ) ) {
			return;
		}

		$opts         = ADVK_Settings::get_options();
		$correct_only = (int) $opts['winner_correct_only'];
		// phpcs:ignore WordPress.Security.NonceVerification.Recommended -- Read-only list filter via bookmarkable GET link; page is capability-guarded above.
		$day_filter   = isset( $_GET['advk_day'] ) ? (int) $_GET['advk_day'] : 0;

		$winners = ADVK_Entries::query(
			array(
				'per_page'     => 1000,
				'offset'       => 0,
				'day'          => $day_filter,
				'winners_only' => true,
				'orderby'      => 'day',
				'order'        => 'ASC',
			)
		);

		// phpcs:ignore WordPress.Security.NonceVerification.Recommended -- Read-only admin notice flag set by our own post-redirect; page is capability-guarded above.
		$notice = isset( $_GET['advk_notice'] ) ? sanitize_text_field( wp_unslash( $_GET['advk_notice'] ) ) : '';

		$export_url = wp_nonce_url(
			admin_url( 'admin-post.php?action=advk_export_winners' ),
			'advk_export_winners'
		);
		?>
		<div class="wrap advk-wrap advk-wrap--wide">
			<h1><span class="dashicons dashicons-awards"></span> <?php esc_html_e( 'Gewinner-Auslosung', 'adventura-interactive-advent-calendar' ); ?></h1>

			<?php if ( $notice ) : ?>
				<div class="notice notice-success is-dismissible"><p><?php echo esc_html( $notice ); ?></p></div>
			<?php endif; ?>

			<div class="advk-card">
				<h2><?php esc_html_e( 'Gewinner ziehen', 'adventura-interactive-advent-calendar' ); ?></h2>
				<form method="post" action="<?php echo esc_url( admin_url( 'admin-post.php' ) ); ?>">
					<?php wp_nonce_field( 'advk_draw_winner' ); ?>
					<input type="hidden" name="action" value="advk_draw_winner" />
					<div class="advk-winner-row">
						<label for="advk_draw_day"><?php esc_html_e( 'Türchen:', 'adventura-interactive-advent-calendar' ); ?></label>
						<select id="advk_draw_day" name="day">
							<?php for ( $i = 1; $i <= ADVK_Data::door_count(); $i++ ) : ?>
								<?php /* translators: %d: door day number (1–24). */ ?>
								<option value="<?php echo esc_attr( $i ); ?>"><?php echo esc_html( sprintf( __( 'Tag %d', 'adventura-interactive-advent-calendar' ), $i ) ); ?></option>
							<?php endfor; ?>
						</select>
						<label><input type="checkbox" name="correct_only" value="1" <?php checked( $correct_only, 1 ); ?> /> <?php esc_html_e( 'Nur Teilnehmer mit allen richtigen Antworten', 'adventura-interactive-advent-calendar' ); ?></label>
						<?php submit_button( __( 'Zufällig ziehen', 'adventura-interactive-advent-calendar' ), 'primary', '', false ); ?>
					</div>
				</form>
			</div>

			<div class="advk-card">
				<h2><?php esc_html_e( 'Gewinnerliste', 'adventura-interactive-advent-calendar' ); ?></h2>

				<form method="get" style="margin:0 0 14px;">
					<input type="hidden" name="page" value="advk-winners" />
					<label for="advk_day_filter"><?php esc_html_e( 'Türchen filtern:', 'adventura-interactive-advent-calendar' ); ?></label>
					<select id="advk_day_filter" name="advk_day" onchange="this.form.submit()">
						<option value="0"><?php esc_html_e( 'Alle', 'adventura-interactive-advent-calendar' ); ?></option>
						<?php for ( $i = 1; $i <= ADVK_Data::door_count(); $i++ ) : ?>
							<?php /* translators: %d: door day number (1–24). */ ?>
							<option value="<?php echo esc_attr( $i ); ?>" <?php selected( $day_filter, $i ); ?>><?php echo esc_html( sprintf( __( 'Tag %d', 'adventura-interactive-advent-calendar' ), $i ) ); ?></option>
						<?php endfor; ?>
					</select>
					<a href="<?php echo esc_url( $export_url ); ?>" class="button" style="margin-left:8px;"><?php esc_html_e( 'CSV-Export', 'adventura-interactive-advent-calendar' ); ?></a>
				</form>

				<form method="post" action="<?php echo esc_url( admin_url( 'admin-post.php' ) ); ?>" style="margin:0 0 14px;" onsubmit="return confirm('<?php echo esc_js( __( 'E-Mails an alle noch nicht benachrichtigten Gewinner senden?', 'adventura-interactive-advent-calendar' ) ); ?>');">
					<?php wp_nonce_field( 'advk_notify_winners' ); ?>
					<input type="hidden" name="action" value="advk_notify_winners" />
					<input type="hidden" name="day" value="<?php echo (int) $day_filter; ?>" />
					<button type="submit" class="button button-primary">
						<?php
						echo $day_filter
							/* translators: %d: door day number (1–24). */
							? esc_html( sprintf( __( 'Gewinner für Tag %d benachrichtigen', 'adventura-interactive-advent-calendar' ), $day_filter ) )
							: esc_html__( 'Alle Gewinner benachrichtigen', 'adventura-interactive-advent-calendar' );
						?>
					</button>
					<span class="description" style="margin-left:8px;"><?php esc_html_e( 'Sendet die Gewinner-Mail nur an noch nicht benachrichtigte Gewinner.', 'adventura-interactive-advent-calendar' ); ?></span>
				</form>

				<table class="wp-list-table widefat fixed striped">
					<thead>
						<tr>
							<th><?php esc_html_e( 'Tag', 'adventura-interactive-advent-calendar' ); ?></th>
							<th><?php esc_html_e( 'Name', 'adventura-interactive-advent-calendar' ); ?></th>
							<th><?php esc_html_e( 'E-Mail', 'adventura-interactive-advent-calendar' ); ?></th>
							<th><?php esc_html_e( 'Preis', 'adventura-interactive-advent-calendar' ); ?></th>
							<th><?php esc_html_e( 'Ergebnis', 'adventura-interactive-advent-calendar' ); ?></th>
							<th><?php esc_html_e( 'Los-Nr.', 'adventura-interactive-advent-calendar' ); ?></th>
							<th><?php esc_html_e( 'Benachrichtigt', 'adventura-interactive-advent-calendar' ); ?></th>
							<th><?php esc_html_e( 'Aktion', 'adventura-interactive-advent-calendar' ); ?></th>
						</tr>
					</thead>
					<tbody>
					<?php if ( empty( $winners ) ) : ?>
						<tr><td colspan="8"><?php esc_html_e( 'Noch keine Gewinner gezogen.', 'adventura-interactive-advent-calendar' ); ?></td></tr>
					<?php else : ?>
						<?php foreach ( $winners as $w ) : ?>
							<tr>
								<td><?php echo (int) $w->day; ?></td>
								<td><?php echo esc_html( trim( $w->first_name . ' ' . $w->last_name ) ); ?></td>
								<td><a href="mailto:<?php echo esc_attr( $w->email ); ?>"><?php echo esc_html( $w->email ); ?></a></td>
								<td><?php echo esc_html( self::prize_for_winner( $w->day, $w->id ) ); ?></td>
								<td><?php echo (int) $w->correct_count; ?>/<?php echo (int) $w->total_questions; ?></td>
								<td><code><?php echo esc_html( $w->losnr ); ?></code></td>
								<td>
									<?php $notified_at = self::notified_at( (int) $w->id ); ?>
									<?php if ( '' !== $notified_at ) : ?>
										<span class="advk-badge is-winner" title="<?php echo esc_attr( $notified_at ); ?>">✓ <?php echo esc_html( $notified_at ); ?></span>
									<?php else : ?>
										<span style="color:#9aa0a6;">—</span>
									<?php endif; ?>
								</td>
								<td>
									<form method="post" action="<?php echo esc_url( admin_url( 'admin-post.php' ) ); ?>" style="display:inline;">
										<?php wp_nonce_field( 'advk_toggle_winner' ); ?>
										<input type="hidden" name="action" value="advk_toggle_winner" />
										<input type="hidden" name="id" value="<?php echo (int) $w->id; ?>" />
										<input type="hidden" name="flag" value="0" />
										<button type="submit" class="button-link delete"><?php esc_html_e( 'Entfernen', 'adventura-interactive-advent-calendar' ); ?></button>
									</form>
								</td>
							</tr>
						<?php endforeach; ?>
					<?php endif; ?>
					</tbody>
				</table>

				<form method="post" action="<?php echo esc_url( admin_url( 'admin-post.php' ) ); ?>" style="margin-top:14px;" onsubmit="return confirm('<?php echo esc_js( __( 'Wirklich alle Gewinner-Markierungen zurücksetzen?', 'adventura-interactive-advent-calendar' ) ); ?>');">
					<?php wp_nonce_field( 'advk_clear_winners' ); ?>
					<input type="hidden" name="action" value="advk_clear_winners" />
					<input type="hidden" name="day" value="<?php echo (int) $day_filter; ?>" />
					<button type="submit" class="button button-secondary">
						<?php
						echo $day_filter
							/* translators: %d: door day number (1–24). */
							? esc_html( sprintf( __( 'Gewinner für Tag %d zurücksetzen', 'adventura-interactive-advent-calendar' ), $day_filter ) )
							: esc_html__( 'Alle Gewinner zurücksetzen', 'adventura-interactive-advent-calendar' );
						?>
					</button>
				</form>
			</div>
		</div>
		<?php
	}

	public function export_csv() {
		if ( ! current_user_can( 'manage_options' ) ) {
			wp_die( esc_html__( 'Keine Berechtigung.', 'adventura-interactive-advent-calendar' ) );
		}
		check_admin_referer( 'advk_export_winners' );

		$winners = ADVK_Entries::query(
			array(
				'per_page'     => 100000,
				'offset'       => 0,
				'winners_only' => true,
				'orderby'      => 'day',
				'order'        => 'ASC',
			)
		);

		$filename = 'adventura-gewinner-' . wp_date( 'Y-m-d' ) . '.csv';

		nocache_headers();
		header( 'Content-Type: text/csv; charset=utf-8' );
		header( 'Content-Disposition: attachment; filename="' . $filename . '"' );

		// Build the CSV in memory (no direct filesystem handles) and stream it.
		$csv  = chr( 0xEF ) . chr( 0xBB ) . chr( 0xBF );
		$csv .= $this->csv_row( array( 'Tag', 'Vorname', 'Nachname', 'E-Mail', 'Preis', 'Los-Nr.', 'Richtig', 'Fragen gesamt', 'Datum' ) );

		foreach ( $winners as $w ) {
			$csv .= $this->csv_row(
				array(
					(int) $w->day,
					$w->first_name,
					$w->last_name,
					$w->email,
					self::prize_for_winner( $w->day, $w->id ),
					$w->losnr,
					(int) $w->correct_count,
					(int) $w->total_questions,
					mysql2date( 'd.m.Y H:i', $w->created_at ),
				)
			);
		}

		echo $csv; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- CSV file download, not HTML; values are quote-escaped in csv_row().
		exit;
	}

	/**
	 * Build a single RFC-4180 CSV line (fields quoted, inner quotes doubled).
	 *
	 * @param array $fields Field values.
	 * @return string
	 */
	private function csv_row( $fields ) {
		$escaped = array();
		foreach ( $fields as $f ) {
			$escaped[] = '"' . str_replace( '"', '""', (string) $f ) . '"';
		}
		return implode( ',', $escaped ) . "\r\n";
	}
}