<?php

declare(strict_types=1);

namespace WebCalendar\WP\Holiday;

defined( 'ABSPATH' ) || exit;

/**
 * Holiday provider using the Nager.Date public API.
 *
 * @see https://date.nager.at/
 */
class NagerDateProvider implements HolidayProviderInterface {

	private const API_BASE      = 'https://date.nager.at/api/v3';
	private const TRANSIENT_KEY = 'webcal_nager_countries';
	private const TRANSIENT_TTL = 604800; // 1 week in seconds

	public function get_id(): string {
		return 'nager';
	}

	public function get_label(): string {
		return __( 'Nager.Date (Official Public Holidays)', 'agenticdaisy-calendar' );
	}

	/**
	 * @return array<string, string>
	 */
	public function get_countries(): array {
		$cached = get_transient( self::TRANSIENT_KEY );
		if ( is_array( $cached ) && count( $cached ) > 0 ) {
			/** @var array<string, string> $cached */
			return $cached;
		}

		$response = wp_remote_get(
			self::API_BASE . '/AvailableCountries',
			[
				'timeout' => 15,
			]
		);

		if ( is_wp_error( $response ) ) {
			throw new \RuntimeException( esc_html( $response->get_error_message() ) );
		}

		$code = wp_remote_retrieve_response_code( $response );
		if ( 200 !== $code ) {
			throw new \RuntimeException(
				// translators: %d is the HTTP status code.
				sprintf( esc_html__( 'Nager.Date API returned HTTP %d', 'agenticdaisy-calendar' ), (int) $code )
			);
		}

		$body = wp_remote_retrieve_body( $response );
		/** @var list<array<string, mixed>>|null $data */
		$data = json_decode( $body, true );

		if ( ! is_array( $data ) ) {
			throw new \RuntimeException( esc_html__( 'Invalid response from Nager.Date API', 'agenticdaisy-calendar' ) );
		}

		$countries = [];
		foreach ( $data as $entry ) {
			if ( isset( $entry['countryCode'], $entry['name'] )
				&& is_string( $entry['countryCode'] )
				&& is_string( $entry['name'] )
			) {
				$countries[ $entry['countryCode'] ] = $entry['name'];
			}
		}

		asort( $countries );
		set_transient( self::TRANSIENT_KEY, $countries, self::TRANSIENT_TTL );

		return $countries;
	}

	public function fetch_holidays( string $country_code, int $year ): string {
		$url = sprintf( '%s/PublicHolidays/%d/%s', self::API_BASE, $year, rawurlencode( $country_code ) );

		$response = wp_remote_get(
			$url,
			[
				'timeout' => 15,
			]
		);

		if ( is_wp_error( $response ) ) {
			throw new \RuntimeException( esc_html( $response->get_error_message() ) );
		}

		$code = wp_remote_retrieve_response_code( $response );
		if ( 200 !== $code ) {
			throw new \RuntimeException(
				// translators: 1: HTTP status code, 2: country code, 3: year.
				sprintf( esc_html__( 'Nager.Date API returned HTTP %1$d for %2$s/%3$d', 'agenticdaisy-calendar' ), (int) $code, esc_html( $country_code ), (int) $year )
			);
		}

		$body = wp_remote_retrieve_body( $response );
		/** @var list<array<string, mixed>>|null $holidays */
		$holidays = json_decode( $body, true );

		if ( ! is_array( $holidays ) ) {
			throw new \RuntimeException( esc_html__( 'Invalid holiday data from Nager.Date API', 'agenticdaisy-calendar' ) );
		}

		return $this->to_ics( $holidays, $country_code, $year );
	}

	/**
	 * Convert Nager.Date JSON holiday array to ICS string.
	 *
	 * @param list<array<string, mixed>> $holidays Holiday data.
	 * @param string                                                      $country  Country code.
	 * @param int                                                         $year     Year.
	 * @return string ICS content.
	 */
	private function to_ics( array $holidays, string $country, int $year ): string {
		$lines = [
			'BEGIN:VCALENDAR',
			'VERSION:2.0',
			'PRODID:-//WebCalendar//Nager.Date//EN',
		];

		foreach ( $holidays as $holiday ) {
			if ( ! isset( $holiday['date'], $holiday['name'] )
				|| ! is_string( $holiday['date'] )
				|| ! is_string( $holiday['name'] )
			) {
				continue;
			}
			$local_name = isset( $holiday['localName'] ) && is_string( $holiday['localName'] )
				? $holiday['localName']
				: $holiday['name'];
			$date       = str_replace( '-', '', $holiday['date'] );
			$name       = $local_name;
			$uid        = sprintf( '%d-%s-%s@webcalendar', $year, $country, md5( $holiday['name'] ) );
			$end_dt     = new \DateTimeImmutable( $holiday['date'] );
			$end        = $end_dt->modify( '+1 day' )->format( 'Ymd' );

			$lines[] = 'BEGIN:VEVENT';
			$lines[] = 'DTSTART;VALUE=DATE:' . $date;
			$lines[] = 'DTEND;VALUE=DATE:' . $end;
			$lines[] = 'SUMMARY:' . $this->escape_ics_text( $name );
			$lines[] = 'UID:' . $uid;
			$lines[] = 'END:VEVENT';
		}

		$lines[] = 'END:VCALENDAR';

		return implode( "\r\n", $lines );
	}

	/**
	 * Escape text for ICS property values.
	 *
	 * @param string $text Raw text.
	 * @return string Escaped text.
	 */
	private function escape_ics_text( string $text ): string {
		$text = str_replace( '\\', '\\\\', $text );
		$text = str_replace( ',', '\\,', $text );
		$text = str_replace( ';', '\\;', $text );
		$text = str_replace( "\n", '\\n', $text );
		return $text;
	}
}