<?php
/**
 * Server capability detection and limits (§8.3, §16).
 *
 * @package DatabaseExportGenie
 */

namespace DatabaseExportGenie;

defined( 'ABSPATH' ) || exit;

/**
 * Static helpers describing what this server can do.
 */
class Environment {

	const CACHE_OPTION = 'dbmg_env_cache';
	const CACHE_TTL    = 43200; // 12 h.

	/**
	 * True when a PHP function exists and isn't listed in disable_functions.
	 *
	 * @param string $name Function name.
	 * @return bool
	 */
	public static function can_call( $name ) {
		if ( ! function_exists( $name ) ) {
			return false;
		}
		$disabled = array_map( 'trim', explode( ',', strtolower( (string) ini_get( 'disable_functions' ) ) ) );
		return ! in_array( strtolower( $name ), $disabled, true );
	}

	/**
	 * Seconds a tick may work (§8.3). $short caps it for heartbeat/poll nudges.
	 *
	 * @param bool $short Nudge tick (≤ 10 s).
	 * @return int
	 */
	public static function budget_seconds( $short = false ) {
		static $base = null;
		if ( null === $base ) {
			// Read before raise_limits() so an unlimited set_time_limit(0) doesn't hide the host's real limit.
			$max  = (int) ini_get( 'max_execution_time' );
			$base = ( $max > 0 ) ? max( 5, min( 20, (int) floor( $max * 0.4 ) ) ) : 20;
		}
		$budget = (int) apply_filters( 'dbmg_tick_budget', $base );
		$budget = max( 1, $budget );
		return $short ? min( $budget, 10 ) : $budget;
	}

	/**
	 * Lift limits where the host allows it.
	 */
	public static function raise_limits() {
		self::budget_seconds(); // Prime the cached base budget first.
		if ( self::can_call( 'set_time_limit' ) ) {
			@set_time_limit( 0 ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged, Squiz.PHP.DiscouragedFunctions.Discouraged -- long downloads/ticks; guarded by can_call() and the tick budget.
		}
		if ( function_exists( 'wp_raise_memory_limit' ) ) {
			wp_raise_memory_limit( 'admin' );
		}
	}

	/**
	 * @return int Bytes, or 0 for unlimited.
	 */
	public static function memory_limit() {
		$raw = (string) ini_get( 'memory_limit' );
		if ( '' === $raw || '-1' === trim( $raw ) ) {
			return 0;
		}
		return (int) wp_convert_hr_to_bytes( $raw );
	}

	/**
	 * Memory guard at 70 % of memory_limit (§8.3).
	 *
	 * @return bool
	 */
	public static function memory_near_limit() {
		$limit = self::memory_limit();
		if ( $limit <= 0 ) {
			return false;
		}
		return memory_get_usage( true ) > 0.7 * $limit;
	}

	/**
	 * Bytes we can still allocate before the 70 % guard (used to size read buffers).
	 *
	 * @return int
	 */
	public static function memory_headroom() {
		$limit = self::memory_limit();
		if ( $limit <= 0 ) {
			return 256 * MB_IN_BYTES;
		}
		return max( 0, (int) ( 0.7 * $limit ) - memory_get_usage( true ) );
	}

	/**
	 * Close the HTTP response early so the caller doesn't wait (loopback ticks, create).
	 */
	public static function finish_request() {
		if ( function_exists( 'fastcgi_finish_request' ) ) {
			fastcgi_finish_request();
			return true;
		}
		if ( function_exists( 'litespeed_finish_request' ) ) {
			litespeed_finish_request();
			return true;
		}
		return false;
	}

	/**
	 * Which database family runs this site: mysql | sqlite | multidb | unsupported.
	 *
	 * @return string
	 */
	public static function db_engine() {
		global $wpdb;
		if ( ( defined( 'DB_ENGINE' ) && 'sqlite' === DB_ENGINE ) || ( is_object( $wpdb ) && 'WP_SQLite_DB' === get_class( $wpdb ) ) ) {
			return 'sqlite';
		}
		if ( ! is_object( $wpdb ) ) {
			return 'unsupported';
		}
		if ( ! empty( $wpdb->hyper_servers ) || ! empty( $wpdb->ludicrous_servers ) ) {
			return 'multidb';
		}
		if ( $wpdb instanceof \wpdb ) {
			// PG4WP and similar drop-ins keep the wpdb class but talk to another server.
			if ( defined( 'DB_DRIVER' ) && in_array( strtolower( (string) DB_DRIVER ), array( 'pgsql', 'postgres', 'postgresql', 'sqlsrv', 'mssql' ), true ) ) {
				return 'unsupported';
			}
			return 'mysql';
		}
		return 'unsupported';
	}

	/**
	 * Name of the web server software (for Nginx/IIS guidance).
	 *
	 * @return string apache|nginx|litespeed|iis|caddy|other
	 */
	public static function web_server() {
		$soft = isset( $_SERVER['SERVER_SOFTWARE'] ) ? strtolower( sanitize_text_field( wp_unslash( $_SERVER['SERVER_SOFTWARE'] ) ) ) : '';
		foreach ( array( 'nginx', 'litespeed', 'apache', 'caddy' ) as $name ) {
			if ( false !== strpos( $soft, $name ) ) {
				return $name;
			}
		}
		if ( false !== strpos( $soft, 'iis' ) ) {
			return 'iis';
		}
		return 'other';
	}

	/**
	 * zlib incremental deflate available (else store-only zips).
	 *
	 * @return bool
	 */
	public static function has_deflate() {
		return function_exists( 'deflate_init' ) && function_exists( 'inflate_init' ) && (bool) apply_filters( 'dbmg_use_deflate', true );
	}

	/**
	 * @return bool WP-Cron can run by itself.
	 */
	public static function cron_enabled() {
		return ! ( defined( 'DISABLE_WP_CRON' ) && DISABLE_WP_CRON );
	}

	/**
	 * Cached environment probes (12 h).
	 *
	 * @return array
	 */
	public static function cache() {
		$cache = Options::get( self::CACHE_OPTION, array() );
		if ( ! is_array( $cache ) || empty( $cache['time'] ) || ( time() - (int) $cache['time'] ) > self::CACHE_TTL ) {
			return array();
		}
		return $cache;
	}

	/**
	 * @param array $data Merged into the cache.
	 */
	public static function cache_set( array $data ) {
		$cache         = self::cache();
		$cache         = array_merge( $cache, $data );
		$cache['time'] = isset( $cache['time'] ) ? $cache['time'] : time();
		Options::set( self::CACHE_OPTION, $cache );
	}

	/**
	 * Can this site call its own admin-ajax.php? Result cached for 12 h.
	 *
	 * @param bool $force Ignore the cache.
	 * @return bool
	 */
	public static function loopback_works( $force = false ) {
		if ( ! apply_filters( 'dbmg_use_loopback', true ) ) {
			return false;
		}
		$cache = self::cache();
		if ( ! $force && isset( $cache['loopback'] ) ) {
			return (bool) $cache['loopback'];
		}
		$token = wp_generate_password( 20, false );
		Options::set( 'dbmg_ping', $token );
		$response = wp_remote_post(
			admin_url( 'admin-ajax.php' ),
			array(
				'timeout'   => 5,
				'blocking'  => true,
				'sslverify' => apply_filters( 'https_local_ssl_verify', false ), // phpcs:ignore WordPress.NamingConventions.PrefixAllGlobals.NonPrefixedHooknameFound -- core filter, used as core's own loopback requests do.
				'body'      => array(
					'action' => 'dbmg_ping',
					'token'  => $token,
					'nonce'  => wp_create_nonce( Runner::LOOPBACK_NONCE ),
				),
				'cookies'   => Runner::loopback_cookies(),
			)
		);
		Options::delete( 'dbmg_ping' );
		$ok = ! is_wp_error( $response ) && 200 === (int) wp_remote_retrieve_response_code( $response ) && false !== strpos( (string) wp_remote_retrieve_body( $response ), 'dbmg-pong' );
		self::cache_set( array( 'loopback' => $ok ) );
		return $ok;
	}

	/**
	 * background (loopback or cron can drive it) | browser (only open admin pages can) (§8.2).
	 *
	 * @return string
	 */
	public static function run_mode() {
		$mode = ( self::loopback_works() || self::cron_enabled() ) ? 'background' : 'browser';
		return 'browser' === apply_filters( 'dbmg_run_mode', $mode ) ? 'browser' : 'background';
	}

	/**
	 * Summary for the details panel and the manifest.
	 *
	 * @return array
	 */
	public static function summary() {
		global $wp_version;
		return array(
			'wp'           => $wp_version,
			'php'          => PHP_VERSION,
			'site_url'     => home_url(),
			'charset'      => defined( 'DB_CHARSET' ) && DB_CHARSET ? DB_CHARSET : 'utf8mb4',
			'table_prefix' => $GLOBALS['wpdb']->base_prefix,
			'multisite'    => is_multisite(),
		);
	}
}