<?php
/**
 * Business+ financial report over a booking window.
 *
 * @package Bookline
 */

declare( strict_types=1 );

namespace Bookline\Application\Reporting;

use Bookline\Application\Auth\AccessScope;
use Bookline\Application\Booking\ListBookingsHandler;
use Bookline\Domain\Booking\BookingStatus;
use Bookline\Domain\Edition\NamedFeature;
use Bookline\Domain\Edition\NamedFeatureGate;
use Bookline\Domain\Edition\OpenNamedFeatureGate;
use Bookline\Domain\Shared\DomainException;
use DateInterval;
use DateTimeImmutable;
use DateTimeZone;

/**
 * Aggregates calendar-window bookings. Cancelled and rescheduled rows
 * are already absent from find_for_admin_calendar.
 *
 * @since 0.35.0
 */
final class FinancialReportsService {

	/**
	 * Inclusive calendar-day ceiling for a report window.
	 */
	public const MAX_RANGE_DAYS = 366;

	/**
	 * Constructor.
	 *
	 * @param ListBookingsHandler   $windows Booking window.
	 * @param NamedFeatureGate|null $named   Paid-plan features; open when omitted.
	 */
	public function __construct(
		private readonly ListBookingsHandler $windows,
		private readonly ?NamedFeatureGate $named = null,
	) {}

	/**
	 * Totals, status mix, and per-day series.
	 *
	 * @param AccessScope       $scope     Access scope.
	 * @param DateTimeImmutable $from_utc  Inclusive start (UTC).
	 * @param DateTimeImmutable $to_utc    Exclusive end (UTC).
	 * @param string            $timezone  IANA zone for day buckets.
	 * @return array<string, mixed>
	 *
	 * @throws DomainException When the range is invalid.
	 */
	public function summarise(
		AccessScope $scope,
		DateTimeImmutable $from_utc,
		DateTimeImmutable $to_utc,
		string $timezone
	): array {
		$this->named_features()->assert_allows( NamedFeature::Reports );
		$zone     = $this->zone( $timezone );
		$from_utc = $from_utc->setTimezone( new DateTimeZone( 'UTC' ) );
		$to_utc   = $to_utc->setTimezone( new DateTimeZone( 'UTC' ) );
		$this->assert_range( $from_utc, $to_utc );
		$bookings = $this->windows->handle( $scope, $from_utc, $to_utc );

		$by_status = [];
		$by_day    = [];
		$revenue   = [];
		$no_show   = 0;
		foreach ( $bookings as $booking ) {
			$status = $booking->status()->value;
			$by_status[ $status ] = ( $by_status[ $status ] ?? 0 ) + 1;
			if ( BookingStatus::NoShow === $booking->status() ) {
				++$no_show;
			}
			$day = $booking->start_utc()->setTimezone( $zone )->format( 'Y-m-d' );
			if ( ! isset( $by_day[ $day ] ) ) {
				$by_day[ $day ] = [
					'date'     => $day,
					'bookings' => 0,
					'revenue'  => [],
				];
			}
			++$by_day[ $day ]['bookings'];
			$currency = $booking->price()->currency();
			$minor    = $booking->price()->amount_minor();
			$revenue[ $currency ] = ( $revenue[ $currency ] ?? 0 ) + $minor;
			$day_rev              = $by_day[ $day ]['revenue'];
			$day_rev[ $currency ] = ( $day_rev[ $currency ] ?? 0 ) + $minor;
			$by_day[ $day ]['revenue'] = $day_rev;
		}

		ksort( $by_day );
		$total = count( $bookings );
		$rev_list = [];
		foreach ( $revenue as $code => $amount ) {
			$rev_list[] = [
				'currency'     => $code,
				'amount_minor' => $amount,
			];
		}

		return [
			'from'          => $from_utc->format( 'c' ),
			'to'            => $to_utc->format( 'c' ),
			'timezone'      => $zone->getName(),
			'booking_count' => $total,
			'no_show_count' => $no_show,
			'no_show_rate'  => 0 === $total ? 0 : (int) round( ( $no_show / $total ) * 10000 ),
			'revenue'       => $rev_list,
			'by_status'     => $this->status_rows( $by_status ),
			'by_day'        => array_values( $by_day ),
		];
	}

	/**
	 * CSV extract of the same window (one row per booking).
	 *
	 * @param AccessScope       $scope     Access scope.
	 * @param DateTimeImmutable $from_utc  Inclusive start (UTC).
	 * @param DateTimeImmutable $to_utc    Exclusive end (UTC).
	 * @param string            $timezone  IANA zone for the date column.
	 * @return array{filename: string, csv: string}
	 *
	 * @throws DomainException When the range is invalid.
	 */
	public function csv(
		AccessScope $scope,
		DateTimeImmutable $from_utc,
		DateTimeImmutable $to_utc,
		string $timezone
	): array {
		$this->named_features()->assert_allows( NamedFeature::Reports );
		$zone     = $this->zone( $timezone );
		$from_utc = $from_utc->setTimezone( new DateTimeZone( 'UTC' ) );
		$to_utc   = $to_utc->setTimezone( new DateTimeZone( 'UTC' ) );
		$this->assert_range( $from_utc, $to_utc );
		$bookings = $this->windows->handle( $scope, $from_utc, $to_utc );

		$lines   = [ 'date,booking_id,status,amount_minor,currency' ];
		foreach ( $bookings as $booking ) {
			$lines[] = implode(
				',',
				[
					self::csv_field( $booking->start_utc()->setTimezone( $zone )->format( 'Y-m-d' ) ),
					self::csv_field( (string) ( $booking->id() ?? 0 ) ),
					self::csv_field( $booking->status()->value ),
					self::csv_field( (string) $booking->price()->amount_minor() ),
					self::csv_field( $booking->price()->currency() ),
				]
			);
		}

		$from_day = $from_utc->setTimezone( $zone )->format( 'Y-m-d' );
		$to_day   = $to_utc->sub( new DateInterval( 'PT1S' ) )->setTimezone( $zone )->format( 'Y-m-d' );

		return [
			'filename' => 'buildler-report-' . $from_day . '-to-' . $to_day . '.csv',
			'csv'      => implode( "\n", $lines ) . "\n",
		];
	}

	/**
	 * Plan map, or the open directory gate.
	 */
	private function named_features(): NamedFeatureGate {
		return $this->named ?? new OpenNamedFeatureGate();
	}

	/**
	 * Refuse inverted or over-long windows.
	 *
	 * @param DateTimeImmutable $from Start.
	 * @param DateTimeImmutable $to   End.
	 *
	 * @throws DomainException When inverted or longer than a year.
	 */
	private function assert_range( DateTimeImmutable $from, DateTimeImmutable $to ): void {
		if ( $to <= $from ) {
			throw new DomainException( 'reports.range', 'Report end must be after start.' );
		}
		$days = (int) $from->diff( $to )->days;
		if ( $days > self::MAX_RANGE_DAYS ) {
			throw new DomainException( 'reports.range_too_long', 'Report range must be 366 days or fewer.' );
		}
	}

	/**
	 * Parse an IANA timezone, defaulting to UTC.
	 *
	 * @param string $timezone IANA id.
	 *
	 * @throws DomainException When the zone is unknown.
	 */
	private function zone( string $timezone ): DateTimeZone {
		$tz = '' !== trim( $timezone ) ? trim( $timezone ) : 'UTC';
		try {
			return new DateTimeZone( $tz );
		} catch ( \Exception ) {
			throw new DomainException( 'reports.timezone', 'Unknown timezone.' );
		}
	}

	/**
	 * Status mix rows.
	 *
	 * @param array<string, int> $counts Status tallies.
	 * @return list<array{status: string, count: int}>
	 */
	private function status_rows( array $counts ): array {
		$rows = [];
		foreach ( $counts as $status => $count ) {
			$rows[] = [
				'status' => $status,
				'count'  => $count,
			];
		}
		return $rows;
	}

	/**
	 * RFC 4180 field.
	 *
	 * @param string $value Value.
	 */
	private static function csv_field( string $value ): string {
		if ( ! str_contains( $value, ',' ) && ! str_contains( $value, '"' ) && ! str_contains( $value, "\n" ) ) {
			return $value;
		}
		return '"' . str_replace( '"', '""', $value ) . '"';
	}
}