<?php
/**
 * What a migration's outcome actually was.
 *
 * @package Shiftora
 */

declare(strict_types=1);

namespace Shiftora\Migration;

// Prevent direct file access.
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Turns a stored status into a statement about the data, so every screen uses one
 * wording.
 *
 * Distinctions kept, since collapsing any produces a false claim:
 * - Only the database is rolled back. A snapshot is SQL; replaced uploads stay replaced.
 * - On a pull the local snapshot is the safety net. On a push this site has no
 *   snapshot, so a recovered push means the remote was put back.
 * - `recovered` means recovery worked; `failed` means the restore point is only an option.
 */
final class MigrationOutcome {

		/**
		 * The data state, as opposed to the run state.
		 *
		 * - `clean`: nothing to undo.
		 * - `database_restored`: database is back to before the run; files may not be.
		 * - `remote_restored`: the other site is back to before the run.
		 * - `partial`: the run stopped part-way and nothing was rolled back.
		 */
	private const STATE_CLEAN              = 'clean';
	private const STATE_DATABASE_RESTORED  = 'database_restored';
	private const STATE_REMOTE_RESTORED   = 'remote_restored';
	private const STATE_PARTIAL            = 'partial';

		/**
		 * @param array{id:int,direction:string,status:string,recovery_status?:string|null} $migration A migrations table row.
		 *
		 * @return array{
		 *     state:string,
		 *     rolled_back:bool,
		 *     files_restored:bool,
		 *     headline:string,
		 *     detail:string,
		 *     snapshot_available:bool,
		 *     snapshot_reachable:bool,
		 *     destination: string
		 * }
		 */
	public static function describe( array $migration ): array {
		$status    = (string) ( $migration['status'] ?? '' );
		$direction = strtolower( (string) ( $migration['direction'] ?? 'pull' ) );
		$is_pull   = 'pull' === $direction;

		// Only a pull writes a local restore point, so a row from the push days has none.
		$snapshot_written = $is_pull;

		$recovered = MigrationStatus::Recovered->value === $status;
		$failed    = MigrationStatus::Failed->value === $status;
		$completed = MigrationStatus::Completed->value === $status;

		if ( $completed || $recovered ) {
			$state  = $recovered
				? ( $is_pull ? self::STATE_DATABASE_RESTORED : self::STATE_REMOTE_RESTORED )
				: self::STATE_CLEAN;
			$rolled = $recovered;
		} elseif ( $failed ) {
			$state  = self::STATE_PARTIAL;
			$rolled = false;
		} else {
			// Pending, running, paused, cancelling. Nothing to report yet.
			$state  = self::STATE_CLEAN;
			$rolled = false;
		}

		return [
			'state'               => $state,
			'rolled_back'         => $rolled,
			// Always false. Nothing in this plugin restores files.
			'files_restored'      => false,
			'snapshot_available'  => $snapshot_written,
			// The Backups page lists every restore point, so a written one is reachable.
			'snapshot_reachable'  => $snapshot_written,
			'destination'         => $is_pull ? 'this site' : 'the connected site',
			'headline'            => self::headline( $state, $is_pull ),
			'detail'              => self::detail( $state, $is_pull, $snapshot_written ),
		];
	}

	private static function headline( string $state, bool $is_pull ): string {
		switch ( $state ) {
			case self::STATE_DATABASE_RESTORED:
				return __( 'Migration failed. Your previous database was restored.', 'shiftora' );

			case self::STATE_REMOTE_RESTORED:
				return __( 'Migration failed. The connected site was restored.', 'shiftora' );

			case self::STATE_PARTIAL:
				return __( 'Migration failed. Review the details before retrying.', 'shiftora' );

			case self::STATE_CLEAN:
			default:
				return __( 'The migration completed.', 'shiftora' );
		}
	}

	private static function detail( string $state, bool $is_pull, bool $snapshot_written ): string {
		switch ( $state ) {
			case self::STATE_DATABASE_RESTORED:
				/*
				 * A restore point is SQL. Uploads already copied stay copied, so the
				 * message must not say the site was fully put back.
				 */
				return __( 'The database is the state it was before the run. Files that had already been copied were not restored.', 'shiftora' );

			case self::STATE_REMOTE_RESTORED:
				return __( 'Nothing on this site changed as a result of the run.', 'shiftora' );

			case self::STATE_PARTIAL:
				return $snapshot_written && $is_pull
					? __( 'Your database may be partway through the migration. A restore point from before it started is available.', 'shiftora' )
					: __( 'The destination may be partway through the migration.', 'shiftora' );

			case self::STATE_CLEAN:
			default:
				return '';
		}
	}
}