<?php
/**
 * Batch processing settings: per-tick work size, time budget, memory.
 *
 * @package SpinxQuickMigrate
 */

namespace SpinxQM;

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

/**
 * Resolves per-tick batch size, time budget and memory limits for background jobs.
 */
class Batch_Settings {

	/**
	 * Named presets → items processed per cron/heartbeat tick.
	 *
	 * @var array<string,int>
	 */
	const PRESETS = array(
		'small'  => 10,
		'medium' => 50,
		'fast'   => 100,
	);

	/**
	 * Default preset key.
	 */
	public static function default_preset(): string {
		return 'medium';
	}

	/**
	 * Resolve the number of work units to process per tick for an operation.
	 *
	 * @param string $operation Operation slug (export|backup|find_replace).
	 */
	public static function batch_size( string $operation = '' ): int {
		$settings = Helpers::get_settings();
		$preset   = (string) ( $settings['batch_preset'] ?? self::default_preset() );

		if ( 'custom' === $preset ) {
			$size = max( 1, absint( $settings['batch_size_custom'] ?? self::PRESETS['medium'] ) );
		} else {
			$size = self::PRESETS[ $preset ] ?? self::PRESETS['medium'];
		}

		/**
		 * Filter the per-tick batch size.
		 *
		 * @param int    $size      Items per tick.
		 * @param string $operation Operation slug.
		 */
		$size = (int) apply_filters( 'spinxqm_batch_size', $size, $operation );

		return max( 1, $size );
	}

	/**
	 * Bytes of output to accumulate per step request before yielding. This is the
	 * primary work limiter for the browser-driven step loop (a "max request
	 * size"): each step writes ~this many bytes of SQL, then returns
	 * so the browser can immediately fire the next request. Larger = fewer, beefier
	 * requests = faster on capable hosts; smaller = lower memory/peak.
	 *
	 * @param string $operation Operation slug.
	 */
	public static function chunk_bytes( string $operation = '' ): int {
		$settings = Helpers::get_settings();
		$bytes    = absint( $settings['max_chunk_bytes'] ?? 0 );
		if ( $bytes < 1 ) {
			$bytes = 6 * MB_IN_BYTES;
		}

		/**
		 * Filter the per-step output byte budget.
		 *
		 * @param int    $bytes     Bytes per step.
		 * @param string $operation Operation slug.
		 */
		$bytes = (int) apply_filters( 'spinxqm_chunk_bytes', $bytes, $operation );

		// Clamp to a sane window (256 KB – 128 MB).
		return max( 256 * KB_IN_BYTES, min( 128 * MB_IN_BYTES, $bytes ) );
	}

	/**
	 * Maximum bytes of row data per INSERT statement in a SQL dump. Keeps every
	 * statement comfortably under MySQL's max_allowed_packet on import (a single
	 * 2000-row extended INSERT of large rows can otherwise blow the packet limit and
	 * the importer's buffer). Default 1 MB; filterable.
	 */
	public static function max_insert_bytes(): int {
		$bytes = (int) apply_filters( 'spinxqm_max_insert_bytes', (int) MB_IN_BYTES );
		return max( 64 * KB_IN_BYTES, $bytes );
	}

	/**
	 * Gzip compression level for SQL output. Default 6 (the standard zlib balance);
	 * 1 = fastest/largest, 9 = slowest/smallest.
	 */
	public static function gzip_level(): int {
		$settings = Helpers::get_settings();
		$level    = (int) ( $settings['gzip_level'] ?? 6 );

		/**
		 * Filter the gzip compression level.
		 *
		 * @param int $level Compression level 1–9.
		 */
		$level = (int) apply_filters( 'spinxqm_gzip_level', $level );

		return max( 1, min( 9, $level ) );
	}

	/**
	 * Soft time budget (seconds) for a single step request. The batch loop yields
	 * once this elapses even if the byte budget has not been reached, so a slow
	 * chunk never blows past the request limit. No set_time_limit() is used.
	 *
	 * @param string $operation Operation slug.
	 */
	public static function time_budget( string $operation = '' ): int {
		/**
		 * Filter the per-tick soft time budget in seconds.
		 *
		 * @param int    $seconds   Default budget.
		 * @param string $operation Operation slug.
		 */
		$seconds = (int) apply_filters( 'spinxqm_process_timeout', 20, $operation );

		return max( 5, $seconds );
	}

	/**
	 * Raise the memory ceiling for a processing tick using the WordPress
	 * wrapper (never ini_set). Developers can override via the filter.
	 */
	public static function maybe_raise_memory(): void {
		$custom = (string) apply_filters( 'spinxqm_process_memory_limit', '' );
		if ( '' !== $custom ) {
			add_filter(
				'admin_memory_limit',
				static function () use ( $custom ) {
					return $custom;
				}
			);
		}
		wp_raise_memory_limit( 'admin' );
	}

	/**
	 * Whether a preset key is valid (named preset or "custom").
	 *
	 * @param string $preset Preset key to check.
	 * @return bool
	 */
	public static function is_valid_preset( string $preset ): bool {
		return 'custom' === $preset || isset( self::PRESETS[ $preset ] );
	}
}