<?php
/**
 * Automatic regeneration (since 1.8.2).
 *
 * Changes that are visible in llms.txt mark the file as outdated. One regeneration runs
 * 10 minutes after the last change (at the latest 60 minutes after the first one), so
 * bulk edits cause one run instead of hundreds. In Pro mode automatic runs are at least
 * 2 hours apart, keeping well within the daily API quota. A nightly run picks up changes
 * no save event reports, such as the revenue ranking shifting through new orders.
 *
 * @package LLMs_Txt_Generator
 */

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

/**
 * Debounced, quota-aware automatic regeneration.
 */
class LLMSTXT_Auto_Update {

	const HOOK        = 'llmstxt_auto_regen';
	const NIGHTLY     = 'llmstxt_nightly_regen';
	const OPTION      = 'llmstxt_auto_state';
	const DEBOUNCE    = 600;   // seconds after the last change.
	const MAX_WAIT    = 3600;  // latest run after the first change.
	const PRO_MIN_GAP = 7200;  // minimum gap between automatic Pro runs.

	/** Product properties that change what llms.txt shows. Stock quantity alone does not. */
	const RELEVANT = array( 'name', 'slug', 'status', 'catalog_visibility', 'regular_price', 'sale_price', 'price', 'date_on_sale_from', 'date_on_sale_to', 'stock_status', 'short_description', 'description', 'category_ids', 'sku', 'attributes' );

	/**
	 * Register hooks.
	 *
	 * @param array<string,mixed> $opts Plugin settings.
	 */
	public static function init( array $opts ): void {
		add_action( self::HOOK, array( __CLASS__, 'run' ) );
		add_action( self::NIGHTLY, array( __CLASS__, 'nightly' ) );

		if ( empty( $opts['auto_update'] ) ) {
			add_action( 'init', array( __CLASS__, 'unschedule_all' ), 30 );
			return;
		}
		add_action( 'woocommerce_before_product_object_save', array( __CLASS__, 'on_product_save' ), 10, 1 );
		add_action( 'transition_post_status', array( __CLASS__, 'on_status' ), 10, 3 );
		add_action( 'init', array( __CLASS__, 'ensure_nightly' ), 30 );
	}

	/**
	 * WooCommerce product or variation is about to be saved: mark only if a visible property changes.
	 *
	 * @param WC_Product $product Product being saved.
	 */
	public static function on_product_save( $product ): void {
		if ( ! $product instanceof WC_Product ) {
			return;
		}
		$changes = $product->get_changes();
		if ( ! $product->get_id() ) {
			if ( 'publish' === $product->get_status() ) {
				self::mark( 'product' );
			}
			return;
		}
		if ( array_intersect( array_keys( $changes ), self::RELEVANT ) ) {
			self::mark( isset( $changes['stock_status'] ) ? 'stock' : 'product' );
		}
	}

	/**
	 * Pages and posts: published, updated while published, unpublished or trashed.
	 * Products only when their publication status changes (edits come through on_product_save).
	 *
	 * @param string  $new  New status.
	 * @param string  $old  Old status.
	 * @param WP_Post $post Post.
	 */
	public static function on_status( $new, $old, $post ): void {
		if ( ! $post instanceof WP_Post || ( 'publish' !== $new && 'publish' !== $old ) ) {
			return;
		}
		if ( in_array( $post->post_type, array( 'page', 'post' ), true ) ) {
			self::mark( 'trash' === $new ? 'trash' : 'content' );
		} elseif ( 'product' === $post->post_type && $new !== $old ) {
			self::mark( 'trash' === $new ? 'trash' : 'product' );
		}
	}

	/**
	 * Mark the files as outdated and (re)schedule the bundled run.
	 *
	 * @param string $reason product | stock | content | trash.
	 */
	public static function mark( string $reason ): void {
		$now   = time();
		$state = self::state();
		if ( empty( $state['dirty_since'] ) ) {
			$state['dirty_since'] = $now;
		}
		$state['reason']      = $reason;
		$state['last_change'] = $now;
		$due                  = min( $now + self::DEBOUNCE, (int) $state['dirty_since'] + self::MAX_WAIT );
		if ( self::is_pro() ) {
			$due = max( $due, (int) ( $state['last_run'] ?? 0 ) + self::PRO_MIN_GAP );
		}
		$state['due'] = $due;
		update_option( self::OPTION, $state, false );

		$next = wp_next_scheduled( self::HOOK );
		if ( $next && abs( $next - $due ) > 30 ) {
			wp_unschedule_event( $next, self::HOOK );
			$next = false;
		}
		if ( ! $next ) {
			wp_schedule_single_event( $due, self::HOOK );
		}
	}

	/**
	 * Bundled run (WP-Cron).
	 */
	public static function run(): void {
		$state = self::state();
		if ( empty( $state['dirty_since'] ) ) {
			return;
		}
		if ( self::is_pro() && time() < (int) ( $state['last_run'] ?? 0 ) + self::PRO_MIN_GAP ) {
			wp_schedule_single_event( (int) $state['last_run'] + self::PRO_MIN_GAP, self::HOOK );
			return;
		}
		self::generate( (string) ( $state['reason'] ?? 'product' ) );
	}

	/**
	 * Nightly run: catches ranking shifts from new orders and anything no save event reports.
	 */
	public static function nightly(): void {
		$state = self::state();
		if ( self::is_pro() && time() < (int) ( $state['last_run'] ?? 0 ) + self::PRO_MIN_GAP ) {
			return;
		}
		self::generate( 'nightly' );
	}

	/**
	 * Generate and record the outcome.
	 *
	 * @param string $reason Why this run happened.
	 */
	private static function generate( string $reason ): void {
		$state                = self::state();
		$state['dirty_since'] = 0;   // Changes during the run mark the files again.
		$state['due']         = 0;
		$state['last_run']    = time();
		$state['last_reason'] = $reason;
		update_option( self::OPTION, $state, false );

		$ok = ( new LLMSTXT_Generator() )->generate_and_save();

		$state               = self::state();
		$state['last_ok']    = $ok;
		$state['last_error'] = $ok ? '' : (string) get_option( 'llmstxt_last_error', '' );
		update_option( self::OPTION, $state, false );
	}

	/**
	 * Schedule the nightly run at a fixed time between 01:00 and 04:00 site time, spread per site
	 * so that not every shop contacts the generator at the same minute.
	 */
	public static function ensure_nightly(): void {
		if ( wp_next_scheduled( self::NIGHTLY ) ) {
			return;
		}
		$minute = 60 + ( absint( crc32( (string) home_url() ) ) % 180 );
		$start  = new DateTime( 'tomorrow', wp_timezone() );
		$start->modify( '+' . $minute . ' minutes' );
		wp_schedule_event( $start->getTimestamp(), 'daily', self::NIGHTLY );
	}

	/**
	 * Remove all scheduled automatic runs (auto-update switched off, deactivation).
	 */
	public static function unschedule_all(): void {
		if ( wp_next_scheduled( self::NIGHTLY ) ) {
			wp_clear_scheduled_hook( self::NIGHTLY );
		}
		if ( wp_next_scheduled( self::HOOK ) ) {
			wp_clear_scheduled_hook( self::HOOK );
		}
	}

	/**
	 * Status for the settings page.
	 *
	 * @return array{last_run:int,last_reason:string,last_ok:bool,last_error:string,next:int,nightly:int}
	 */
	public static function status(): array {
		$s = self::state();
		return array(
			'last_run'    => (int) ( $s['last_run'] ?? 0 ),
			'last_reason' => (string) ( $s['last_reason'] ?? '' ),
			'last_ok'     => ! empty( $s['last_ok'] ),
			'last_error'  => (string) ( $s['last_error'] ?? '' ),
			'next'        => (int) wp_next_scheduled( self::HOOK ),
			'nightly'     => (int) wp_next_scheduled( self::NIGHTLY ),
		);
	}

	/**
	 * Stored state.
	 *
	 * @return array<string,mixed>
	 */
	private static function state(): array {
		$s = get_option( self::OPTION, array() );
		return is_array( $s ) ? $s : array();
	}

	/**
	 * Pro mode active?
	 */
	private static function is_pro(): bool {
		$opts = get_option( 'llmstxt_settings', array() );
		return 'pro' === ( $opts['mode'] ?? 'free' ) && ! empty( $opts['pro_key'] );
	}
}