<?php

namespace RoosterLMS\Invitations;

use RoosterLMS\Attendance\AttendanceStatus;
use RoosterLMS\Core\Clock;
use RoosterLMS\Data\Db;
use RoosterLMS\Data\SqlPart;
use RoosterLMS\Data\Transaction;
use RoosterLMS\Domain\Actor;
use RoosterLMS\Ledger\Event;
use RoosterLMS\Ledger\EventWriter;
use RoosterLMS\Ledger\Verb;

defined( 'ABSPATH' ) || exit;

final class Outcomes {

	public const NET_DAYS = 7;

	private const NET_LESSON_DAYS = 31;

	private const CHUNK = 1000;

	private static bool $registered = false;

	public static function register(): void {
		if ( self::$registered ) {
			return;
		}
		self::$registered = true;
		add_action( 'rooster_lms_attendance_marked', array( self::class, 'attendance' ), 20, 3 );
		add_action( 'rooster_lms_enrolled', array( self::class, 'enrolled' ), 20, 5 );
		add_action( 'rooster_lms_cohort_membership_changed', array( self::class, 'cohort' ), 20, 3 );
	}

	public static function attendance( $occurrence_id, $user_ids = array(), $status = 0 ): int {
		unset( $status );
		$users         = self::ids( (array) $user_ids );
		$occurrence_id = (int) $occurrence_id;
		if ( $occurrence_id <= 0 || array() === $users || ! InvitationService::used() ) {
			return 0;
		}
		global $wpdb;
		$here = SqlPart::of( '( COALESCE( ( SELECT a.status FROM %i a WHERE a.occurrence_id = %d AND a.user_id = i.user_id ), 0 ) IN (%d, %d) )', Db::table( 'attendance' ), $occurrence_id, AttendanceStatus::PRESENT->value, AttendanceStatus::LATE->value );
		$course  = SqlPart::of( '( SELECT s.course_id FROM %i o JOIN %i s ON s.id = o.session_id WHERE o.id = %d )', Db::table( 'live_occurrences' ), Db::table( 'live_sessions' ), $occurrence_id );
		$changed = 0;
		foreach ( array_chunk( $users, self::CHUNK ) as $chunk ) {
			$where    = SqlPart::of( 'FROM %i i JOIN %i v ON v.id = i.invitation_id WHERE v.occurrence_id = %d AND v.course_id > 0 AND v.course_id = ', Db::table( 'invitees' ), Db::table( 'invitations' ), $occurrence_id )->add( $course )->add( self::sent_sql() )->add( SqlPart::and_in( 'i.user_id', $chunk ) )->add( SqlPart::of( ' AND ( ( i.outcome = %d AND ', InviteeOutcome::NONE->value ) )->add( $here )->add( SqlPart::of( ' ) OR ( i.outcome = %d AND NOT ', InviteeOutcome::ATTENDED->value ) )->add( $here )->add( ' ) )' );
			$changed += self::write( $where, $where, SqlPart::of( '( CASE WHEN ' )->add( $here )->add( ' THEN ' . InviteeOutcome::ATTENDED->value . ' ELSE ' . InviteeOutcome::NONE->value . ' END )' ) );
		}
		return $changed;
	}

	public static function enrolled( $enrolment_id, $user_id = 0, $course_id = 0, $org_id = 0, $source = 0 ): int {
		unset( $enrolment_id, $org_id, $source );
		if ( (int) $user_id <= 0 || (int) $course_id <= 0 || ! InvitationService::used() ) {
			return 0;
		}
		global $wpdb;
		$where = SqlPart::of( 'FROM %i i JOIN %i v ON v.id = i.invitation_id WHERE i.user_id = %d AND i.answer = %d AND i.outcome IN (%d, %d) AND v.course_id = %d AND v.yes_action <> %d', Db::table( 'invitees' ), Db::table( 'invitations' ), (int) $user_id, RsvpAnswer::YES->value, InviteeOutcome::NONE->value, InviteeOutcome::ATTENDED->value, (int) $course_id, YesAction::JOIN_COHORT->value )->add( self::sent_sql() );
		return self::write( $where, $where, SqlPart::of( (string) InviteeOutcome::ENROLLED->value ) );
	}

	public static function cohort( $cohort_id, $user_ids = array(), $joined = true ): int {
		$users = self::ids( (array) $user_ids );
		if ( true !== (bool) $joined || (int) $cohort_id <= 0 || array() === $users || ! InvitationService::used() ) {
			return 0;
		}
		global $wpdb;
		$changed = 0;
		foreach ( array_chunk( $users, self::CHUNK ) as $chunk ) {
			$where    = SqlPart::of( 'FROM %i v JOIN %i i ON i.invitation_id = v.id WHERE v.target_cohort_id = %d AND i.answer = %d AND i.outcome IN (%d, %d)', Db::table( 'invitations' ), Db::table( 'invitees' ), (int) $cohort_id, RsvpAnswer::YES->value, InviteeOutcome::NONE->value, InviteeOutcome::ATTENDED->value )->add( self::sent_sql() )->add( SqlPart::and_in( 'i.user_id', $chunk ) );
			$changed += self::write( $where, $where, SqlPart::of( (string) InviteeOutcome::JOINED->value ) );
		}
		return $changed;
	}

	public static function daily(): int {
		if ( ! InvitationService::used() ) {
			return 0;
		}
		global $wpdb;
		$now   = Clock::now();
		$since = gmdate( 'Y-m-d H:i:s', Clock::timestamp() - self::NET_DAYS * DAY_IN_SECONDS );
		$start = gmdate( 'Y-m-d H:i:s', Clock::timestamp() - ( self::NET_DAYS + self::NET_LESSON_DAYS ) * DAY_IN_SECONDS );
		$read  = SqlPart::of(
			'FROM %i o JOIN %i s ON s.id = o.session_id JOIN %i v ON v.course_id = s.course_id AND v.occurrence_id = o.id JOIN %i i ON i.invitation_id = v.id JOIN %i a ON a.occurrence_id = o.id AND a.user_id = i.user_id WHERE o.state = 1 AND o.starts_at >= %s AND o.starts_at <= %s AND o.ends_at >= %s AND o.ends_at <= %s AND s.course_id > 0 AND i.outcome = %d AND a.status IN (%d, %d)',
			Db::table( 'live_occurrences' ),
			Db::table( 'live_sessions' ),
			Db::table( 'invitations' ),
			Db::table( 'invitees' ),
			Db::table( 'attendance' ),
			$start,
			$now,
			$since,
			$now,
			InviteeOutcome::NONE->value,
			AttendanceStatus::PRESENT->value,
			AttendanceStatus::LATE->value
		)->add( self::sent_sql() );
		$lock = SqlPart::of( 'FROM %i i JOIN %i v ON v.id = i.invitation_id WHERE i.outcome = %d AND EXISTS ( SELECT 1 FROM %i a WHERE a.occurrence_id = v.occurrence_id AND a.user_id = i.user_id AND a.status IN (%d, %d) )', Db::table( 'invitees' ), Db::table( 'invitations' ), InviteeOutcome::NONE->value, Db::table( 'attendance' ), AttendanceStatus::PRESENT->value, AttendanceStatus::LATE->value )->add( self::sent_sql() );
		return self::write( $read, $lock, SqlPart::of( (string) InviteeOutcome::ATTENDED->value ) );
	}

	private static function sent_sql(): SqlPart {
		global $wpdb;
		return SqlPart::of( ' AND v.kind = %d AND v.state <> %d AND i.user_id > 0 AND i.sent_version > 0', InvitationKind::RSVP->value, InvitationState::CANCELLED->value );
	}

	private static function write( SqlPart $read, SqlPart $lock, SqlPart $outcome ): int {
		$ids     = array_map( 'intval', Db::col( SqlPart::of( 'SELECT /* outside-tx */ i.id ' )->add( $read )->add( ' ORDER BY i.id' ) ) );
		$changed = 0;
		foreach ( array_chunk( $ids, self::CHUNK ) as $chunk ) {
			$changed += self::write_chunk( $lock, $outcome, $chunk );
		}
		return $changed;
	}

	private static function write_chunk( SqlPart $lock, SqlPart $outcome, array $ids ): int {
		$rows = Transaction::run(
			static function () use ( $lock, $outcome, $ids ): array {
				global $wpdb;
				$rows = Db::rows( SqlPart::of( 'SELECT i.id, i.invitation_id, i.user_id, i.email_hash, i.lang, v.course_id, v.unit_id, v.occurrence_id, v.target_cohort_id, ' )->add( $outcome )->add( ' AS rl_new ' )->add( $lock )->add( SqlPart::of( ' AND i.id IN (' . implode( ',', array_fill( 0, count( $ids ), '%d' ) ) . ') ORDER BY i.id', array_map( 'intval', $ids ) ) )->add( ' FOR UPDATE' ) );
				if ( array() === $rows ) {
					return array();
				}
				$now  = Transaction::now();
				$case = SqlPart::of( '' );
				$at   = SqlPart::of( '' );
				foreach ( $rows as $r ) {
					$case = $case->add( SqlPart::of( ' WHEN %d THEN %d', (int) $r['id'], (int) $r['rl_new'] ) );
					$at = $at->add( InviteeOutcome::NONE->value === (int) $r['rl_new'] ? SqlPart::of( ' WHEN %d THEN NULL', (int) $r['id'] ) : SqlPart::of( ' WHEN %d THEN %s', (int) $r['id'], $now ) );
				}
				$in = implode( ',', array_map( static fn( array $r ): int => (int) $r['id'], $rows ) );
				Db::query( SqlPart::of( 'UPDATE %i SET ', Db::table( 'invitees' ) )->add( SqlPart::of( 'outcome = CASE id' )->add( $case )->add( ' ELSE outcome END, outcome_at = CASE id' )->add( $at )->add( ' ELSE outcome_at END WHERE id IN (' )->add( $in )->add( ')' ) ) );
				$events = array();
				foreach ( $rows as $r ) {
					$events[] = new Event( Verb::INVITATION_OUTCOME, Actor::system(), (int) $r['user_id'], (int) $r['course_id'], (int) $r['unit_id'], 0, 0, (float) (int) $r['rl_new'], (int) $r['id'] );
				}
				( new EventWriter() )->record( ...$events );
				return $rows;
			}
		);
		foreach ( $rows as $r ) {
			$set = InviteeOutcome::tryFrom( (int) $r['rl_new'] ) ?? InviteeOutcome::NONE;
			if ( InviteeOutcome::NONE === $set ) {
				continue;
			}
			Events::fire(
				'invitation_' . $set->slug(),
				array(
					'user_id'       => (int) $r['user_id'],
					'email_hash'    => (string) $r['email_hash'],
					'lang'          => (string) $r['lang'],
					'course_id'     => (int) $r['course_id'],
					'unit_id'       => (int) $r['unit_id'],
					'occurrence_id' => (int) $r['occurrence_id'],
					'invitation_id' => (int) $r['invitation_id'],
					'invitee_id'    => (int) $r['id'],
					'cohort_id'     => (int) $r['target_cohort_id'],
					'outcome'       => $set->slug(),
				)
			);
		}
		if ( array() !== $rows ) {
			InvitationRepository::forget();
		}
		return count( $rows );
	}

	private static function ids( array $ids ): array {
		$out = array();
		foreach ( $ids as $id ) {
			$id = (int) $id;
			if ( $id > 0 ) {
				$out[ $id ] = $id;
			}
		}
		return array_values( $out );
	}
}