<?php
/**
 * RepeaterKit - Loop Manager
 *
 * Manages the loop stack for template functions.
 *
 * @package RepeaterKit
 * @since   1.0.0
 */

declare(strict_types=1);

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Internal Loop Manager state holder.
 */
class RepeaterKit_Loop_Manager {

	/**
	 * Active loop stack.
	 *
	 * @var array
	 */
	private static $stack = array();

	/**
	 * Get the currently active loop from the top of the stack.
	 *
	 * @return array|null
	 */
	public static function get_active_loop(): ?array {
		if ( empty( self::$stack ) ) {
			return null;
		}
		return self::$stack[ count( self::$stack ) - 1 ];
	}

	/**
	 * Check if a loop matching selector and post_id is currently active.
	 *
	 * @param string $field_name Field name.
	 * @param mixed  $post_id    Post ID.
	 * @return bool
	 */
	public static function is_loop_active( string $field_name, $post_id ): bool {
		$active = self::get_active_loop();
		if ( ! $active ) {
			return false;
		}
		return ( $active['field'] === $field_name && (int) $active['post_id'] === (int) $post_id );
	}

	/**
	 * Setup a new loop for a given field and post.
	 *
	 * @param string $field_name Field name.
	 * @param mixed  $post_id    Post ID.
	 * @return bool True if rows exist and loop was initialized.
	 */
	public static function init_loop( string $field_name, $post_id ): bool {
		$rows = repeaterkit_get_rows( $field_name, $post_id );

		if ( empty( $rows ) || ! is_array( $rows ) ) {
			return false;
		}

		self::$stack[] = array(
			'field'   => $field_name,
			'post_id' => $post_id,
			'rows'    => array_values( $rows ),
			'total'   => count( $rows ),
			'index'   => -1,
			'current' => null,
		);

		return true;
	}

	/**
	 * Advance to the next row.
	 *
	 * @return array|null Current row data.
	 */
	public static function advance(): ?array {
		if ( empty( self::$stack ) ) {
			return null;
		}

		$idx = count( self::$stack ) - 1;
		++self::$stack[ $idx ]['index'];
		$current_idx = self::$stack[ $idx ]['index'];

		if ( isset( self::$stack[ $idx ]['rows'][ $current_idx ] ) ) {
			self::$stack[ $idx ]['current'] = self::$stack[ $idx ]['rows'][ $current_idx ];
			return self::$stack[ $idx ]['current'];
		}

		return null;
	}

	/**
	 * Check whether the active loop has another row available.
	 * Pops the loop if no more rows exist.
	 *
	 * @return bool
	 */
	public static function step_active(): bool {
		if ( empty( self::$stack ) ) {
			return false;
		}

		$idx        = count( self::$stack ) - 1;
		$next_index = self::$stack[ $idx ]['index'] + 1;

		if ( isset( self::$stack[ $idx ]['rows'][ $next_index ] ) ) {
			return true;
		}

		// Loop finished: pop from stack.
		array_pop( self::$stack );
		return false;
	}

	/**
	 * Get the current active row data.
	 *
	 * @return array|null
	 */
	public static function get_current(): ?array {
		if ( empty( self::$stack ) ) {
			return null;
		}
		return self::$stack[ count( self::$stack ) - 1 ]['current'];
	}

	/**
	 * Get current 1-based row index.
	 *
	 * @return int
	 */
	public static function get_index(): int {
		if ( empty( self::$stack ) ) {
			return 0;
		}
		return max( 0, self::$stack[ count( self::$stack ) - 1 ]['index'] + 1 );
	}

	/**
	 * Reset all active loops.
	 *
	 * @return void
	 */
	public static function reset(): void {
		self::$stack = array();
	}
}