<?php
/**
 * Version tracking across updates.
 *
 * @package AIBlackout
 */

namespace AIBlackout\Core;

use AIBlackout\Declarations\History;

defined( 'ABSPATH' ) || exit;

/**
 * Records which version is installed, and what it replaced.
 *
 * @since 2.0.0
 */
class Upgrade {

	/**
	 * Option holding the installed version.
	 *
	 * @var string
	 */
	const VERSION_OPTION = 'aiblackout_version';

	/**
	 * Option holding the version the last upgrade replaced.
	 *
	 * @var string
	 */
	const PREVIOUS_OPTION = 'aiblackout_previous_version';

	/**
	 * Stand-in for a version that predates this tracking.
	 *
	 * @var string
	 */
	const UNKNOWN_PREVIOUS = '0';

	/**
	 * Registers hooks.
	 *
	 * @return void
	 */
	public function register(): void {
		// Before admin_menu, which builds the menu the unread badge hangs on.
		add_action( 'init', array( $this, 'sync' ), 1 );
	}

	/**
	 * Brings the recorded version into line with the one that is running.
	 *
	 * @return void
	 */
	public function sync(): void {
		$current = AIBLACKOUT_VERSION;
		$stored  = $this->get_installed_version();

		if ( $stored === $current ) {
			return;
		}

		$previous = '' === $stored
			? ( $this->has_earlier_footprint() ? self::UNKNOWN_PREVIOUS : '' )
			: $stored;

		update_option( self::PREVIOUS_OPTION, $previous, true );
		update_option( self::VERSION_OPTION, $current, true );

		/**
		 * Fires once, on the first admin request after the installed version
		 * changed.
		 *
		 * @since 2.0.0
		 *
		 * @param string $current  The version now installed.
		 * @param string $previous The version it replaced, '' or UNKNOWN_PREVIOUS.
		 */
		do_action( 'aiblackout_version_changed', $current, $previous );
	}

	/**
	 * Returns the recorded installed version.
	 *
	 * @return string Version string, or '' when nothing has been recorded.
	 */
	public function get_installed_version(): string {
		return (string) get_option( self::VERSION_OPTION, '' );
	}

	/**
	 * Returns the version the last upgrade replaced.
	 *
	 * @return string Version string, '' on a first install, or UNKNOWN_PREVIOUS.
	 */
	public function get_previous_version(): string {
		return (string) get_option( self::PREVIOUS_OPTION, '' );
	}

	/**
	 * Whether this install has ever run an earlier version of the plugin.
	 *
	 * @return bool True when an earlier version left something behind.
	 */
	private function has_earlier_footprint(): bool {
		return false !== get_option( History::OPTION, false )
			|| false !== get_option( Settings::OPTION, false );
	}
}