<?php
/**
 * Copies another plugin's SMTP connection into Adminkeep's.
 *
 * @package Adminkeep
 */

namespace Adminkeep\Service;

use Adminkeep\Service\SmtpImport\Source;
use Adminkeep\Service\SmtpImport\WpMailSmtpSource;

defined( 'ABSPATH' ) || exit;

/**
 * Writes a source's SMTP connection through SmtpConfig::sanitize(), the same door the screen and
 * `wp adminkeep smtp set` use: a field wp-config.php holds keeps its stored value, and the
 * password is sealed by SecretBox.
 *
 * The report names fields and outcomes, never values: nothing here logs, prints or returns a
 * password, and the caller never needs one to say what happened.
 */
class SmtpImporter {

	/** The source's password was copied. */
	const PASSWORD_COPIED = 'copied';

	/** The source has no password, so Adminkeep's own stays. */
	const PASSWORD_KEPT = 'kept';

	/** The source's password could not be opened, so Adminkeep's own stays. */
	const PASSWORD_UNREADABLE = 'unreadable';

	/** ADMINKEEP_SMTP_PASS holds the password, so nothing is copied over it. */
	const PASSWORD_LOCKED = 'locked';

	/**
	 * The ADMINKEEP_SMTP_* constants in force, by field.
	 *
	 * @var array
	 */
	private $constants;

	/**
	 * Build an importer.
	 *
	 * @param array|null $constants Field => value for the ADMINKEEP_SMTP_* constants in force; null
	 *                              reads the real ones. A parameter so a test can supply some.
	 */
	public function __construct( $constants = null ) {
		$this->constants = null === $constants ? SmtpConfig::defined_constants() : array_intersect_key( (array) $constants, SmtpConfig::CONSTANTS );
	}

	/**
	 * The sources the command and the screen know, by the name the command takes.
	 *
	 * @return array<string, Source>
	 */
	public static function sources() {
		return array(
			'wp-mail-smtp' => WpMailSmtpSource::from_environment(),
		);
	}

	/**
	 * What run() would do, without writing anything.
	 *
	 * @param Source $source Where from.
	 * @return array{source: string, written: string[], kept: string[], password: string}|\WP_Error
	 */
	public function preview( Source $source ) {
		$read = $this->readable( $source );

		return is_wp_error( $read ) ? $read : $this->report( $source, $read );
	}

	/**
	 * Copy the source's connection, replacing Adminkeep's own.
	 *
	 * @param Source $source Where from.
	 * @return array|\WP_Error The same report preview() gives.
	 */
	public function run( Source $source ) {
		$read = $this->readable( $source );

		if ( is_wp_error( $read ) ) {
			return $read;
		}

		$report = $this->report( $source, $read );
		$input  = $read['settings'];

		// Left out of the input, the password is kept by sanitize(): that is what should happen
		// when the source has none, or has one that could not be opened.
		if ( self::PASSWORD_COPIED === $report['password'] ) {
			$input['password'] = $read['password'];
		}

		update_option( SmtpConfig::OPTION, SmtpConfig::sanitize( $input, SmtpConfig::stored(), $this->constants, SecretBox::from_salts() ), false );

		return $report;
	}

	/**
	 * The source's connection, or why it cannot be copied.
	 *
	 * @param Source $source Where from.
	 * @return array|\WP_Error
	 */
	private function readable( Source $source ) {
		if ( ! $source->available() ) {
			return new \WP_Error( 'adminkeep_smtp_import_unavailable', sprintf( 'No %s settings on this site (option %s).', $source->label(), $source->location() ) );
		}

		$mailer = $source->mailer();

		if ( '' === $mailer ) {
			return new \WP_Error( 'adminkeep_smtp_import_mailer', sprintf( '%s has no mailer chosen, so there is nothing to copy.', $source->label() ) );
		}

		if ( 'smtp' !== $mailer ) {
			return new \WP_Error( 'adminkeep_smtp_import_mailer', sprintf( '%1$s is set to send through %2$s, which is not an SMTP connection, so there is nothing to copy. Only a host, port and username setup can be copied.', $source->label(), $mailer ) );
		}

		$read = $source->read();

		if ( '' === trim( (string) $read['settings']['host'] ) ) {
			return new \WP_Error( 'adminkeep_smtp_import_no_host', sprintf( '%s has no SMTP host set, so there is nothing to copy.', $source->label() ) );
		}

		return $read;
	}

	/**
	 * Which fields are written, which wp-config.php keeps, and what becomes of the password.
	 *
	 * @param Source $source Where from.
	 * @param array  $read   What the source read.
	 * @return array{source: string, written: string[], kept: string[], password: string}
	 */
	private function report( Source $source, array $read ) {
		$written = array();
		$kept    = array();

		foreach ( array_keys( $read['settings'] ) as $field ) {
			if ( array_key_exists( $field, $this->constants ) ) {
				$kept[] = $field;
			} else {
				$written[] = $field;
			}
		}

		if ( array_key_exists( 'password', $this->constants ) ) {
			$kept[]   = 'password';
			$password = self::PASSWORD_LOCKED;
		} elseif ( ! $read['password_readable'] ) {
			$password = self::PASSWORD_UNREADABLE;
		} elseif ( '' === $read['password'] ) {
			$password = self::PASSWORD_KEPT;
		} else {
			$written[] = 'password';
			$password  = self::PASSWORD_COPIED;
		}

		return array(
			'source'   => $source->label(),
			'written'  => $written,
			'kept'     => $kept,
			'password' => $password,
		);
	}
}