<?php

use Reservair\Database\Db;
use Reservair\Logger\Logger;

class RsvReservationService {
    private RsvReservationRepository $repo;

    public function __construct() {
        $this->repo = new RsvReservationRepository();
    }

    public function get_all(?int $limit = null, int $skip = 0) {
        return $this->repo->get_all($limit, $skip);
    }

    public function count_all(): int {
        return $this->repo->count_all();
    }

    public function get(int $id) {
        return $this->repo->get($id);
    }

    public function get_detail(int $id): ?array {
        return $this->repo->get_detail($id);
    }

    public function create(RsvReservation $reservation) {
        $reservation->timetable_reservations =
            $this->merge_adjacent($reservation->timetable_reservations);

        // Serialise the availability-check + insert per timetable so two
        // concurrent bookings for the last free slot can't both pass the
        // capacity check and oversell. Locks are taken in a stable order to
        // avoid lock-ordering deadlocks and released only after the commit.
        $timetable_ids = array_values(array_unique(array_map(
            fn($tr) => $tr->timetable_id,
            $reservation->timetable_reservations
        )));
        sort($timetable_ids);

        foreach ($timetable_ids as $tid) {
            if (!Db::acquire_lock($this->booking_lock_name($tid))) {
                throw new \RuntimeException('Could not acquire booking lock for timetable ' . $tid);
            }
        }

        $timetable_reservation_service = new RsvTimetableReservationService();

        try {
            Db::begin_transaction();

            try {
                $reservation_id = $this->repo->insert($reservation->to_array());

                foreach ($reservation->timetable_reservations as $timetable_reservation) {
                    $timetable_reservation_service->create($reservation_id, $timetable_reservation);
                }

                Db::commit();
            } catch (Exception $e) {
                Db::rollback();
                Logger::error($e);
                throw new \Exception($e);
            }

            // Only now that the rows are durably committed do we let listeners
            // (maintainer emails, calendar sync) observe the new reservation.
            $timetable_reservation_service->flush_deferred_events();

            $this->confirmation_state_changed($reservation_id);

            return $reservation_id;
        } finally {
            foreach (array_reverse($timetable_ids) as $tid) {
                Db::release_lock($this->booking_lock_name($tid));
            }
        }
    }

    private function booking_lock_name(int $timetable_id): string {
        return Db::prefix() . 'rsv_booking_' . $timetable_id;
    }

    /**
     * Collapse runs of touching reservations into single spans, so a sequence
     * of back-to-back blocks is stored and notified as one booking.
     *
     * @param  list<RsvTimetableReservation> $timetable_reservations
     * @return list<RsvTimetableReservation>
     */
    private function merge_adjacent(array $timetable_reservations): array {
        $by_timetable = [];
        foreach ($timetable_reservations as $tr) {
            $by_timetable[$tr->timetable_id][] = $tr;
        }

        $merged = [];
        foreach ($by_timetable as $group) {
            usort($group, fn($a, $b) => $a->start_utc <=> $b->start_utc);

            $current = null;
            foreach ($group as $tr) {
                if ($current !== null && $tr->start_utc <= $current->end_utc) {
                    if ($tr->end_utc > $current->end_utc) {
                        $current->end_utc = $tr->end_utc;
                    }
                    continue;
                }

                if ($current !== null) {
                    $merged[] = $current;
                }
                $current = new RsvTimetableReservation(
                    null, $tr->timetable_id, $tr->start_utc, $tr->end_utc
                );
            }

            if ($current !== null) {
                $merged[] = $current;
            }
        }

        return $merged;
    }

    /** Delete a reservation and its dependent timetable reservations and confirmations. */
    public function delete(int $id): void {
        $this->repo->delete($id);
    }

    public function confirmation_state_changed(int $reservation_id): void {
        // Terminal state is persisted, so this is idempotent: once a reservation
        // is confirmed or refused, repeat calls (e.g. a Google Calendar re-sync)
        // short-circuit and never re-dispatch the closing events.
        if ($this->repo->is_resolved($reservation_id)) {
            Logger::info('Reservation already resolved: ' . $reservation_id);
            return;
        }

        // A reservation with no timetable items has nothing to confirm or refuse;
        // bailing out avoids mislabelling it as refused.
        if ($this->repo->count_subitems($reservation_id) === 0) {
            Logger::info('Reservation has not subitems: ' . $reservation_id);
            return;
        }

        $timetable_service = new RsvTimetableReservationService();
        $all_confirmed     = $this->repo->are_subitems_confirmed($reservation_id);
        $any_pending       = $timetable_service->has_pending_confirmation($reservation_id);

        if ($all_confirmed) {
            $this->repo->set_resolved_state($reservation_id, true);
            RsvEventDispatcher::dispatch(new RsvReservationConfirmedEvent($reservation_id));
            $form_submit_id = $this->repo->get_form_submit_id($reservation_id);
            if ($form_submit_id !== null) {
                RsvEventDispatcher::dispatch(new RsvFormSubmitClosedEvent($form_submit_id, $reservation_id, true));
            }
            return;
        }

        if (!$any_pending) {
            // All items resolved but not all confirmed — at least one refused.
            $this->repo->set_resolved_state($reservation_id, false);
            RsvEventDispatcher::dispatch(new RsvReservationRefusedEvent($reservation_id));
            $form_submit_id = $this->repo->get_form_submit_id($reservation_id);
            if ($form_submit_id !== null) {
                RsvEventDispatcher::dispatch(new RsvFormSubmitClosedEvent($form_submit_id, $reservation_id, false));
            }
            return;
        }

        Logger::info('Waiting for pending confirmations on reservation: ' . $reservation_id);
    }
}