<?php
declare(strict_types=1);

namespace Unsupervised\Schedular\Booking;

use Unsupervised\Schedular\Auth\RoleManager;
use Unsupervised\Schedular\Auth\UserName;
use Unsupervised\Schedular\Availability\AvailabilityRepository;
use Unsupervised\Schedular\Availability\AvailabilitySlot;
use Unsupervised\Schedular\Offering\Offering;
use Unsupervised\Schedular\Offering\OfferingRepository;
use Unsupervised\Schedular\Val;

/**
 * Booking a private lesson **for** a student, from wp-admin — the studio's
 * counterpart to the group class's "Add students directly". The front desk takes
 * a phone call, an instructor slots in a make-up lesson; neither of them can log
 * in as the student, and only a guardian may book through the student-facing
 * flow.
 *
 * It reuses `LessonBooker` — the same offering rules, the same atomic slot claim,
 * the same billing — and differs from a student's own booking in exactly four
 * ways, each deliberate:
 *
 * 1. **No intake questions or policy acceptances are recorded.** They are the
 *    student's to answer and agree to; a staff member ticking boxes on their
 *    behalf would be an audit trail that says something untrue. The lesson's
 *    detail page simply shows none.
 * 2. **It is not bounded by what the student could book themselves.** Any open
 *    slot of the instructor's, including one only reachable past a deadline.
 * 3. **It can be booked at no charge**, for a make-up or goodwill lesson, which
 *    skips the payment entirely and confirms the lesson at once.
 * 4. **It can book for a student who cannot book at all** — a guardian's child,
 *    or someone still awaiting approval. Both hold the student role but have
 *    `book_lesson` withheld so that neither can book in their own name; that is
 *    a limit on them, never on the studio acting for them.
 */
class AdminBooking {

	/**
	 * How far ahead the form's list of open times reaches. Long enough to book a
	 * term ahead, short enough that the select stays a select.
	 */
	private const HORIZON_DAYS = 56;

	public function __construct(
		private AvailabilityRepository $availability,
		private OfferingRepository $offerings,
		private LessonBooker $booker,
	) {}

	/**
	 * Book a lesson on a student's behalf, returning the notice to show. When
	 * `$onlyInstructorId` is non-zero the slot must belong to that instructor —
	 * how an instructor's own **My Lessons** page is kept to their own schedule,
	 * where the studio **Scheduler** passes 0 and may book any instructor's time.
	 *
	 * @return string|\WP_Error Success notice, or why nothing was booked.
	 */
	public function book( int $studentId, int $slotId, int $offeringId, string $recurrence, bool $noCharge, string $notes, int $onlyInstructorId = 0 ): string|\WP_Error {
		// The student role, not the `book_lesson` capability — see
		// {@see RoleManager::isStudent()} for why a child and an unapproved signup
		// must both be bookable for.
		if ( ! RoleManager::isStudent( $studentId ) ) {
			return new \WP_Error( 'invalid_student', __( 'Choose a student to book for.', 'unsupervised-schedular' ) );
		}

		$slot = $slotId > 0 ? $this->availability->findById( $slotId ) : null;

		if ( null === $slot || ( $onlyInstructorId > 0 && $slot->instructorId !== $onlyInstructorId ) ) {
			return new \WP_Error( 'invalid_slot', __( 'Choose a time to book.', 'unsupervised-schedular' ) );
		}

		if ( $slot->isBooked ) {
			return new \WP_Error( 'slot_taken', __( 'That time has already been booked.', 'unsupervised-schedular' ) );
		}

		$offering = $this->booker->resolveOffering( $slot, $offeringId );
		if ( $offering instanceof \WP_Error ) {
			return $offering;
		}

		// A weekly reservation needs a weekly time to reserve. The student-facing
		// flow quietly books a single lesson when the slot does not repeat; here the
		// staff member asked for a term and must be told they are not getting one,
		// rather than discovering it later on the roster.
		$weekly = Lesson::RECURRENCE_WEEKLY === $recurrence;
		if ( $weekly && null === $slot->recurrenceGroup ) {
			return new \WP_Error( 'not_weekly', __( 'That time does not repeat weekly, so it cannot be reserved for the term.', 'unsupervised-schedular' ) );
		}

		$reservation = $this->booker->reserve(
			$slot,
			$offering,
			$studentId,
			$weekly ? Lesson::RECURRENCE_WEEKLY : Lesson::RECURRENCE_SINGLE,
			$notes,
			// Stamped on the lesson so it can be told apart later: only a lesson the
			// studio booked may have its intake recorded after the fact.
			get_current_user_id()
		);

		if ( $reservation instanceof \WP_Error ) {
			return $reservation;
		}

		$settlement = $this->booker->settle(
			$reservation['ids'],
			$reservation['anchor_id'],
			$slot,
			$offering,
			$studentId,
			$noCharge
		);

		return $this->notice( $studentId, $offering, $slot, count( $reservation['ids'] ), $settlement['status'] );
	}

	/**
	 * What was booked and what it left owing, so the notice answers the two things
	 * the person who booked it needs to know.
	 */
	private function notice( int $studentId, Offering $offering, AvailabilitySlot $slot, int $count, string $status ): string {
		$who = $this->studentName( $studentId );

		$what = $count > 1
			? sprintf(
				/* translators: 1: student name, 2: lesson type, 3: number of weekly occurrences, 4: first lesson date and time. */
				__( 'Booked %1$s into %2$s — %3$d weekly lessons from %4$s.', 'unsupervised-schedular' ),
				$who,
				$offering->title,
				$count,
				Val::string( mysql2date( 'M j, Y g:i A', $slot->startDt ) )
			)
			: sprintf(
				/* translators: 1: student name, 2: lesson type, 3: lesson date and time. */
				__( 'Booked %1$s into %2$s on %3$s.', 'unsupervised-schedular' ),
				$who,
				$offering->title,
				Val::string( mysql2date( 'M j, Y g:i A', $slot->startDt ) )
			);

		$owing = Lesson::STATUS_CONFIRMED === $status
			? __( 'Nothing is owed, so it is confirmed.', 'unsupervised-schedular' )
			: __( 'A pending payment has been raised; the lesson is confirmed once it settles.', 'unsupervised-schedular' );

		return $what . ' ' . $owing;
	}

	/**
	 * Everything the form's three selects need. `$onlyInstructorId` scopes both the
	 * open times and the lesson types to one instructor's, the same way `book()`
	 * scopes what may be booked.
	 *
	 * @return array{students: list<array{id: int, name: string}>, offerings: list<array{id: int, label: string}>, slots: list<array{id: int, label: string, weekly: bool}>}
	 */
	public function formData( int $onlyInstructorId = 0 ): array {
		$slots     = $this->openSlots( $onlyInstructorId );
		$offerings = array_values(
			array_filter(
				$this->offerings->findAll( $onlyInstructorId, Offering::KIND_PRIVATE_LESSON, true ),
				static fn( Offering $o ): bool => null !== $o->id
			)
		);

		// Whose lesson type / whose time only needs saying when the page spans more
		// than one instructor — on an instructor's own page it is noise.
		$named = 0 === $onlyInstructorId;

		return [
			'students'  => $this->studentOptions(),
			'offerings' => array_map(
				fn( Offering $o ): array => [
					'id'    => (int) $o->id,
					'label' => $this->offeringLabel( $o, $named ),
				],
				$offerings
			),
			'slots'     => array_map(
				fn( AvailabilitySlot $s ): array => [
					'id'     => (int) $s->id,
					'label'  => $this->slotLabel( $s, $named ),
					'weekly' => null !== $s->recurrenceGroup,
				],
				$slots
			),
		];
	}

	/**
	 * Open slots inside the booking horizon, newest last.
	 *
	 * @return list<AvailabilitySlot>
	 */
	private function openSlots( int $instructorId ): array {
		$until = ( new \DateTimeImmutable( Val::string( current_time( 'mysql' ) ) ) )
			->modify( '+' . self::HORIZON_DAYS . ' days' )
			->format( 'Y-m-d H:i:s' );

		return array_values(
			array_filter(
				$this->availability->findAvailable( $instructorId, 0, 0, '', $until ),
				static fn( AvailabilitySlot $s ): bool => null !== $s->id
			)
		);
	}

	/**
	 * A lesson type as "60 min piano (60 min) — Jane Doe", the instructor named
	 * only when the list spans several.
	 */
	private function offeringLabel( Offering $offering, bool $withInstructor ): string {
		$label = $offering->title;

		if ( null !== $offering->durationMinutes ) {
			/* translators: %d: lesson length in minutes. */
			$label .= ' (' . sprintf( __( '%d min', 'unsupervised-schedular' ), $offering->durationMinutes ) . ')';
		}

		return $withInstructor ? $label . ' — ' . $this->instructorName( $offering->instructorId ) : $label;
	}

	/**
	 * An open time as "Mon Sep 2, 4:00 PM (30 min) — Jane Doe — 30 min piano —
	 * repeats weekly": when it is, how long, whose, and what it is already tied to,
	 * since all four decide whether a given student can be booked into it.
	 */
	private function slotLabel( AvailabilitySlot $slot, bool $withInstructor ): string {
		/* translators: %d: lesson length in minutes. */
		$label = Val::string( mysql2date( 'D M j, Y g:i A', $slot->startDt ) ) . ' (' . sprintf( __( '%d min', 'unsupervised-schedular' ), $slot->durationMinutes ) . ')';

		if ( $withInstructor ) {
			$label .= ' — ' . $this->instructorName( $slot->instructorId );
		}

		$tied = null !== $slot->offeringId ? $this->offerings->findById( $slot->offeringId ) : null;
		if ( null !== $tied ) {
			$label .= ' — ' . $tied->title;
		}

		if ( null !== $slot->recurrenceGroup ) {
			$label .= ' — ' . __( 'repeats weekly', 'unsupervised-schedular' );
		}

		return $label;
	}

	private function instructorName( int $instructorId ): string {
		return $this->studentName( $instructorId );
	}

	/** A person's display name, however little the account has on file. */
	private function studentName( int $userId ): string {
		$user = get_userdata( $userId );

		return UserName::format( $user instanceof \WP_User ? $user : null, $userId );
	}

	/**
	 * Everyone who can be booked for, by name — every holder of the student role,
	 * which is exactly the set {@see book()} accepts. That deliberately includes
	 * the children a guardian books for and students still awaiting approval:
	 * neither may book in their own name, both may be booked for.
	 *
	 * @return list<array{id: int, name: string}>
	 */
	private function studentOptions(): array {
		$users = array_filter(
			get_users(
				[
					'role'    => RoleManager::STUDENT,
					'orderby' => 'display_name',
					'order'   => 'ASC',
				]
			),
			static fn( mixed $u ): bool => $u instanceof \WP_User
		);

		return array_values(
			array_map(
				static fn( \WP_User $u ): array => [
					'id'   => (int) $u->ID,
					'name' => UserName::format( $u, (int) $u->ID ),
				],
				$users
			)
		);
	}
}