<?php

namespace RoosterLMS\Community;

use RoosterLMS\Content\ObjectState;
use RoosterLMS\Content\ObjectType;
use RoosterLMS\Core\Clock;
use RoosterLMS\Data\Db;
use RoosterLMS\Data\Transaction;
use RoosterLMS\Domain\DomainError;
use RoosterLMS\Domain\ErrorCode;
use RoosterLMS\Domain\Services;
use RoosterLMS\Events\FeedRate;
use RoosterLMS\I18n\Language;
use RoosterLMS\I18n\Switcher;
use RoosterLMS\Invitations\RsvpPage;
use RoosterLMS\Jobs\Runs;

defined( 'ABSPATH' ) || exit;

final class Waitlist {

	public const ARG = 'rl_wl';

	public const LAUNCH_HOOK = 'rooster_lms_waitlist_launch';

	public const BATCH = 100;

	public const CONFIRM_HOURS = 48;

	public const RETAIN_DAYS = 90;

	public const ADDRESS_LIMIT = 3;

	public static function register(): void {
		add_action( 'template_redirect', array( self::class, 'route' ), 0 );
		add_action( self::LAUNCH_HOOK, array( self::class, 'run_action' ) );
		if ( did_action( 'action_scheduler_init' ) ) {
			self::install();
		} else {
			add_action( 'action_scheduler_init', array( self::class, 'install' ) );
		}
	}

	public static function install(): void {
		if ( ! function_exists( 'as_has_scheduled_action' ) || ! function_exists( 'as_schedule_recurring_action' ) ) {
			return;
		}
		if ( ! as_has_scheduled_action( self::LAUNCH_HOOK, array(), Runs::GROUP ) ) {
			as_schedule_recurring_action( time() + 5 * MINUTE_IN_SECONDS, HOUR_IN_SECONDS, self::LAUNCH_HOOK, array(), Runs::GROUP, true );
		}
	}

	public static function run_action(): void {
		$out = Services::waitlist()->launch( self::BATCH );
		Services::waitlist()->sweep();
		$grants      = \RoosterLMS\Enrolment\LaunchGrants::run_due();
		$out['more'] = $out['more'] || $grants['more'];
		if ( $out['more'] && function_exists( 'as_enqueue_async_action' ) ) {
			as_enqueue_async_action( self::LAUNCH_HOOK, array(), Runs::GROUP, false );
		}
	}

	public function join_user( int $user_id, int $course_id, string $lang = '' ): bool {
		if ( $user_id <= 0 ) {
			DomainError::raise( ErrorCode::FORBIDDEN );
		}
		$this->require_open( $course_id );
		$lang = Language::normalize( '' !== $lang ? $lang : Switcher::current() );
		Transaction::run(
			static function () use ( $user_id, $course_id, $lang ): void {
			$now = Transaction::now();
				Db::query( 'INSERT IGNORE INTO %i (course_id, user_id, email, lang, token, confirmed_at, created_at, notified_at) VALUES (%d, %d, NULL, %s, NULL, %s, %s, NULL)', Db::table( 'course_waitlist' ), $course_id, $user_id, $lang, $now, $now );
			}
		);
		return true;
	}

	public function leave_user( int $user_id, int $course_id ): int {
		return $user_id > 0 ? Db::query( 'DELETE FROM %i WHERE course_id = %d AND user_id = %d', Db::table( 'course_waitlist' ), $course_id, $user_id ) : 0;
	}

	public function join_guest( string $email, int $course_id, string $lang = '' ): bool {
		if ( true !== CommunitySettings::get( 'waitlist_guests' ) ) {
			DomainError::raise( ErrorCode::FORBIDDEN, array( 'reason' => 'guests_off' ) );
		}
		$email = strtolower( trim( sanitize_email( $email ) ) );
		if ( '' === $email || ! is_email( $email ) || strlen( $email ) > 190 ) {
			DomainError::raise( ErrorCode::INVALID, array( 'reason' => 'email' ) );
		}
		$this->require_open( $course_id );
		if ( ! FeedRate::count( 'waitlist', 10 ) || ! self::address_rate( $email ) ) {
			return false;
		}
		$lang  = Language::normalize( '' !== $lang ? $lang : Switcher::current() );
		$token = (string) Transaction::run(
			static function () use ( $email, $course_id, $lang ): string {
			$table = Db::table( 'course_waitlist' );
				$row   = Db::row( 'SELECT id, confirmed_at FROM %i WHERE course_id = %d AND email = %s FOR UPDATE', $table, $course_id, $email );
				if ( null !== $row && null !== $row['confirmed_at'] ) {
					return '';
				}
				$token = bin2hex( random_bytes( 16 ) );
				$now   = Transaction::now();
				if ( null === $row ) {
					Db::query( 'INSERT INTO %i (course_id, user_id, email, lang, token, confirmed_at, created_at, notified_at) VALUES (%d, NULL, %s, %s, %s, NULL, %s, NULL)', $table, $course_id, $email, $lang, $token, $now );
				} else {
					Db::query( 'UPDATE %i SET token = %s, lang = %s, created_at = %s WHERE id = %d', $table, $token, $lang, $now, (int) $row['id'] );
				}
				return $token;
			}
		);
		if ( '' !== $token ) {
			$this->send_confirmation( $email, $course_id, $token, $lang );
		}
		return true;
	}

	public static function address_rate( string $email ): bool {
		$key  = 'rooster_lms_wl_' . substr( wp_hash( 'waitlist_email|' . $email ), 0, 24 );
		$now  = Clock::timestamp();
		$slot = get_transient( $key );
		$slot = is_array( $slot ) && (int) ( $slot[1] ?? 0 ) > $now ? $slot : array( 0, $now + HOUR_IN_SECONDS );
		if ( (int) $slot[0] >= self::ADDRESS_LIMIT ) {
			return false;
		}
		set_transient( $key, array( (int) $slot[0] + 1, (int) $slot[1] ), max( 1, (int) $slot[1] - $now ) );
		return true;
	}

	public static function url( string $token ): string {
		return add_query_arg( self::ARG, rawurlencode( $token ), home_url( '/' ) );
	}

	public static function secret( string $token ): string {
		return substr( hash_hmac( 'sha256', 'rooster-lms-waitlist|' . $token, wp_salt( 'nonce' ) ), 0, 32 );
	}

	public static function nonce_action( string $token ): string {
		return 'rooster_lms_waitlist_' . $token;
	}

	public static function route(): void {
		$raw = \RoosterLMS\UI\TableRequest::get( self::ARG );
		if ( ! is_string( $raw ) || '' === $raw ) {
			return;
		}
		$token  = substr( preg_replace( '/[^a-f0-9]/', '', strtolower( $raw ) ) ?? '', 0, 32 );
		$method = isset( $_SERVER['REQUEST_METHOD'] ) ? strtoupper( sanitize_key( wp_unslash( $_SERVER['REQUEST_METHOD'] ) ) ) : 'GET';
		$post   = 'POST' === $method && \RoosterLMS\Admin\Request::posted_nonce_valid( RsvpPage::NONCE_FIELD, self::nonce_action( $token ) );
		$secret = \RoosterLMS\Admin\Request::posted_key( 'rl_secret' );
		$action = \RoosterLMS\Admin\Request::posted_key( 'rl_do' );
		$page   = Services::waitlist()->page( $token, $post, $secret, $action );
		status_header( 200 );
		foreach ( RsvpPage::HEADERS as $name => $value ) {
			header( $name . ': ' . $value );
		}
		header( 'Content-Type: text/html; charset=utf-8' );
		RsvpPage::output( $page );
		exit;
	}

	public function page( string $token, bool $post, string $secret, string $action = 'confirm' ): string {
		$row = $this->by_token( $token );
		if ( null === $row || ( null === $row['confirmed_at'] && strtotime( (string) $row['created_at'] . ' UTC' ) < Clock::timestamp() - self::CONFIRM_HOURS * HOUR_IN_SECONDS ) ) {
			return '<h1>' . esc_html__( 'This link does not work', 'rooster-lms' ) . '</h1><p>' . esc_html__( 'The link may have expired or be incomplete. Ask again from the course\'s page.', 'rooster-lms' ) . '</p>';
		}
		return (string) Switcher::with(
			(string) $row['lang'],
			function () use ( $row, $token, $post, $secret, $action ): string {
				$title  = self::course_title( (int) $row['course_id'] );
				$head   = '<h1>' . esc_html( $title ) . '</h1>';
				$ok     = $post && hash_equals( self::secret( $token ), $secret );
				$button = static fn( string $do, string $label ): string => '<form method="post" action="' . esc_url( self::url( $token ) ) . '"><input type="hidden" name="rl_secret" value="' . esc_attr( self::secret( $token ) ) . '" />' . RsvpPage::nonce_input( self::nonce_action( $token ) ) . '<input type="hidden" name="rl_do" value="' . esc_attr( $do ) . '" /><button type="submit" class="rl-rsvp__btn">' . esc_html( $label ) . '</button></form>';
				if ( $ok && 'leave' === $action && null !== $row['confirmed_at'] ) {
					$this->leave_token( $token );
					return $head . '<p class="rl-rsvp__msg" role="status">' . esc_html__( 'You are off the waiting list. We will not e-mail you about this course.', 'rooster-lms' ) . '</p>';
				}
				if ( $ok && null === $row['confirmed_at'] ) {
					$this->confirm( $token );
					$row['confirmed_at'] = Clock::now();
				}
				if ( null === $row['confirmed_at'] ) {
					return $head . '<p>' . esc_html__( 'Confirm your e-mail address to get one e-mail when this course opens.', 'rooster-lms' ) . '</p>' . $button( 'confirm', __( 'Confirm', 'rooster-lms' ) );
				}
				return $head . '<p class="rl-rsvp__msg" role="status">' . esc_html__( 'You are on the waiting list. We will e-mail you once when this course opens.', 'rooster-lms' ) . '</p>'
					. '<p class="rl-rsvp__hint">' . esc_html__( 'Changed your mind?', 'rooster-lms' ) . '</p>' . $button( 'leave', __( 'Leave the waiting list', 'rooster-lms' ) );
			}
		);
	}

	public function confirm( string $token ): int {
		return (int) Transaction::run(
			function () use ( $token ): int {
			$table = Db::table( 'course_waitlist' );
				$row   = Db::row( 'SELECT id, course_id, email, confirmed_at FROM %i WHERE token = %s FOR UPDATE', $table, $token );
				if ( null === $row || '' === $token ) {
					return 0;
				}
				if ( null === $row['confirmed_at'] ) {
					$user = get_user_by( 'email', (string) $row['email'] );
					$uid  = $user instanceof \WP_User ? (int) $user->ID : 0;
					if ( $uid > 0 && null !== Db::value( 'SELECT 1 FROM %i WHERE course_id = %d AND user_id = %d', $table, (int) $row['course_id'], $uid ) ) {
						$uid = 0;
					}
					if ( $uid > 0 ) {
						Db::query( 'UPDATE %i SET confirmed_at = %s, user_id = %d WHERE id = %d', $table, Transaction::now(), $uid, (int) $row['id'] );
					} else {
						Db::query( 'UPDATE %i SET confirmed_at = %s WHERE id = %d', $table, Transaction::now(), (int) $row['id'] );
					}
				}
				return (int) $row['course_id'];
			}
		);
	}

	public function leave_token( string $token ): int {
		return '' === $token ? 0 : Db::query( 'DELETE FROM %i WHERE token = %s', Db::table( 'course_waitlist' ), $token );
	}

	public function by_token( string $token ): ?array {
		return 32 === strlen( $token ) ? Db::row( 'SELECT * FROM %i WHERE token = %s', Db::table( 'course_waitlist' ), $token ) : null;
	}

	public function has( int $user_id, int $course_id ): bool {
		return $user_id > 0 && null !== Db::value( 'SELECT 1 FROM %i WHERE course_id = %d AND user_id = %d AND confirmed_at IS NOT NULL', Db::table( 'course_waitlist' ), $course_id, $user_id );
	}

	public function counts( int $course_id ): array {
		$row = Db::row( 'SELECT SUM( confirmed_at IS NOT NULL ) AS c, SUM( confirmed_at IS NULL ) AS p, SUM( notified_at IS NOT NULL ) AS n FROM %i WHERE course_id = %d', Db::table( 'course_waitlist' ), $course_id );
		return array(
			'confirmed' => (int) ( $row['c'] ?? 0 ),
			'pending'   => (int) ( $row['p'] ?? 0 ),
			'notified'  => (int) ( $row['n'] ?? 0 ),
		);
	}

	public function launch( int $limit = self::BATCH ): array {
		global $wpdb;
		$limit = max( 1, $limit );
		$none  = array(
			'claimed' => 0,
			'sent'    => 0,
			'more'    => false,
		);
		$lock = 'rlwl:' . substr( md5( ( defined( 'DB_NAME' ) ? DB_NAME : '' ) . '|' . $wpdb->prefix ), 0, 16 );
		if ( '1' !== (string) Db::value( 'SELECT GET_LOCK(%s, 0)', $lock ) ) {
			return $none;
		}
		try {
			$picked = $this->claim( $limit );
		} finally {
			Db::value( 'SELECT RELEASE_LOCK(%s)', $lock );
		}
		list( $rows, $claimed, $more ) = $picked;
		if ( array() === $rows ) {
			return $none;
		}
		$t    = Notices::course_open_row();
		$sent = 0;
		if ( null !== $t ) {
			foreach ( $rows as $r ) {
				$sent += Notices::course_open( $t, (int) $r['course_id'], (int) ( $r['user_id'] ?? 0 ), (string) ( $r['email'] ?? '' ), (string) $r['lang'], (string) ( $r['token'] ?? '' ) ) ? 1 : 0;
			}
		}
		return array(
			'claimed' => $claimed,
			'sent'    => $sent,
			'more'    => $more,
		);
	}

	private function claim( int $limit ): array {
		global $wpdb;
		$now   = Clock::now();
		$rows  = Db::rows(

				'SELECT w.id, w.course_id, w.user_id, w.email, w.lang, w.token FROM %i w JOIN %i c ON c.id = w.course_id
				WHERE w.notified_at IS NULL AND w.confirmed_at IS NOT NULL AND ( c.coming_soon_flags & %d ) > 0 AND c.available_from IS NOT NULL AND c.available_from <= %s AND c.state = %d
				ORDER BY w.id LIMIT %d',
				Db::table( 'course_waitlist' ),
				Db::table( 'courses' ),
				CourseFacts::NOTIFY_WAITLIST,
				$now,
				ObjectState::ACTIVE->value,
				$limit + 1

		);
		$more = count( $rows ) > $limit;
		$rows = array_slice( $rows, 0, $limit );
		if ( array() === $rows ) {
			return array( array(), 0, false );
		}
		$ids     = array_map( static fn( array $r ): int => (int) $r['id'], $rows );
		$claimed = (int) Transaction::run(
			static function () use ( $ids, $wpdb ): int {
				return Db::query( 'UPDATE %i SET notified_at = %s WHERE notified_at IS NULL AND id IN (' . implode( ',', array_fill( 0, count( $ids ), '%d' ) ) . ')', array_merge( array( Db::table( 'course_waitlist' ), Transaction::now() ), $ids ) );
			}
		);
		if ( count( $rows ) !== $claimed ) {
			return array( array(), $claimed, $more );
		}
		return array( $rows, $claimed, $more );
	}

	public function sweep(): int {
		$table = Db::table( 'course_waitlist' );
		$n     = Db::query( 'DELETE FROM %i WHERE confirmed_at IS NULL AND created_at < %s LIMIT 5000', $table, gmdate( 'Y-m-d H:i:s', Clock::timestamp() - self::CONFIRM_HOURS * HOUR_IN_SECONDS ) );
		return $n + Db::query( 'DELETE FROM %i WHERE notified_at IS NOT NULL AND notified_at < %s LIMIT 5000', $table, gmdate( 'Y-m-d H:i:s', Clock::timestamp() - self::RETAIN_DAYS * DAY_IN_SECONDS ) );
	}

	public function delete_course( int $course_id ): int {
		return $course_id > 0 ? Db::query( 'DELETE FROM %i WHERE course_id = %d', Db::table( 'course_waitlist' ), $course_id ) : 0;
	}

	public function of_email( string $email ): array {
		$email = strtolower( trim( $email ) );
		return '' === $email ? array() : Db::rows( 'SELECT * FROM %i WHERE email = %s ORDER BY id LIMIT 500', Db::table( 'course_waitlist' ), $email );
	}

	public function erase_email( string $email ): int {
		$email = strtolower( trim( $email ) );
		return '' === $email ? 0 : Db::query( 'DELETE FROM %i WHERE email = %s', Db::table( 'course_waitlist' ), $email );
	}

	public static function course_title( int $course_id ): string {
		return (string) ( Services::posts()->titles( ObjectType::COURSE, array( $course_id ) )[ $course_id ]['title'] ?? '' );
	}

	private function require_open( int $course_id ): void {
		if ( ! CourseFacts::exists( $course_id ) ) {
			DomainError::raise( ErrorCode::NOT_FOUND );
		}
		if ( ! CourseFacts::coming_soon( $course_id ) ) {
			DomainError::raise( ErrorCode::NOT_OPEN, array( 'reason' => 'not_coming_soon' ) );
		}
	}

	private function send_confirmation( string $email, int $course_id, string $token, string $lang ): void {
		Switcher::with(
			$lang,
			static function () use ( $email, $course_id, $token, $lang ): void {
				$title = self::course_title( $course_id );
				$site  = wp_specialchars_decode( (string) get_bloginfo( 'name' ), ENT_QUOTES );
				/* translators: %s: site name. */
				$subject = sprintf( __( 'Confirm your e-mail for %s', 'rooster-lms' ), $site );
				$p       = static fn( string $text, string $style = 'margin:0 0 12px;' ): string => '<p style="' . $style . '">' . esc_html( $text ) . '</p>';
				$hours   = self::CONFIRM_HOURS;
				$body    = $p(
					/* translators: %s: course title. */
					sprintf( __( 'You asked us to e-mail you when the course "%s" opens. Confirm your address to join its waiting list:', 'rooster-lms' ), $title )
				)
					. '<p style="margin:16px 0 20px;"><a href="' . esc_url( self::url( $token ) ) . '" style="display:inline-block;padding:10px 18px;border-radius:6px;background:#2a69b8;color:#ffffff;text-decoration:none;font-weight:600;" data-rl-notrack="1">' . esc_html__( 'Confirm my e-mail', 'rooster-lms' ) . '</a></p>'
					/* translators: %d: hours. */
					. $p( sprintf( _n( 'The link works for %d hour.', 'The link works for %d hours.', $hours, 'rooster-lms' ), $hours ) )
					. $p( __( 'If you did not ask for this, ignore this message: nothing is kept and you will not get e-mails from us.', 'rooster-lms' ), 'margin:16px 0 0;font-size:12px;color:#646970;' );
				Services::notifier()->deliver( $email, $subject, $body, 0, $lang );
			}
		);
	}
}