<?php
/**
 * Clustering settings.
 *
 * @package CreatorAssistantCategories
 */

declare( strict_types=1 );

namespace CreatorAssistantCategories;

use WP_Error;

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

/**
 * The three similarity thresholds (one per category level) and the minimum
 * cluster size. Design decision: thresholds, not a number of clusters per
 * level, so posts are grouped only when they are actually similar; the
 * defaults are a starting point to calibrate on the site's own posts.
 */
final class Settings {

	public const DEFAULT_THRESHOLDS       = array( 0.45, 0.6, 0.75 );
	public const DEFAULT_MIN_CLUSTER_SIZE = 2;
	public const MAX_MIN_CLUSTER_SIZE     = 20;

	/**
	 * The saved settings, or the defaults when none (or broken ones) are saved.
	 *
	 * @return array{thresholds: float[], min_cluster_size: int}
	 */
	public static function get(): array {
		$saved = get_option( Config::SETTINGS_OPTION, array() );
		$valid = is_array( $saved ) ? self::sanitize( $saved ) : null;

		return is_array( $valid ) ? $valid : self::defaults();
	}

	/**
	 * The default settings.
	 *
	 * @return array{thresholds: float[], min_cluster_size: int}
	 */
	public static function defaults(): array {
		return array(
			'thresholds'       => self::DEFAULT_THRESHOLDS,
			'min_cluster_size' => self::DEFAULT_MIN_CLUSTER_SIZE,
		);
	}

	/**
	 * Validates settings coming from the form or the database.
	 *
	 * @param array $input Raw values: thresholds (3 numbers), min_cluster_size.
	 *
	 * @return array{thresholds: float[], min_cluster_size: int}|WP_Error
	 */
	public static function sanitize( array $input ) {
		$thresholds = $input['thresholds'] ?? null;

		if ( ! is_array( $thresholds ) || 3 !== count( $thresholds ) ) {
			return new WP_Error( 'invalid_thresholds', __( 'Enter three similarity thresholds.', 'creator-assistant-categories' ) );
		}

		$values = array();

		foreach ( array_values( $thresholds ) as $threshold ) {
			// Round first: the saved value is the rounded one, so 0.996 would
			// be stored as 1.0 and 0.004 as 0.0, both outside the open range.
			$rounded = is_numeric( $threshold ) ? round( (float) $threshold, 2 ) : 0.0;

			if ( $rounded <= 0 || $rounded >= 1 ) {
				return new WP_Error( 'invalid_thresholds', __( 'Every threshold must be a number between 0 and 1.', 'creator-assistant-categories' ) );
			}

			$values[] = $rounded;
		}

		if ( ! ( $values[0] < $values[1] && $values[1] < $values[2] ) ) {
			return new WP_Error( 'invalid_thresholds', __( 'Each level needs a higher threshold than the one above it.', 'creator-assistant-categories' ) );
		}

		// A whole number only: casting would silently turn 2.7 into 2.
		$size = filter_var(
			$input['min_cluster_size'] ?? null,
			FILTER_VALIDATE_INT,
			array(
				'options' => array(
					'min_range' => 1,
					'max_range' => self::MAX_MIN_CLUSTER_SIZE,
				),
			)
		);

		if ( false === $size ) {
			return new WP_Error(
				'invalid_min_cluster_size',
				/* translators: %d: the largest accepted value. */
				sprintf( __( 'The minimum number of articles per category must be between 1 and %d.', 'creator-assistant-categories' ), self::MAX_MIN_CLUSTER_SIZE )
			);
		}

		return array(
			'thresholds'       => $values,
			'min_cluster_size' => $size,
		);
	}

	/**
	 * Saves already sanitized settings. Not autoloaded: read only by the admin
	 * page and when an analysis starts.
	 *
	 * @param array{thresholds: float[], min_cluster_size: int} $settings Sanitized settings.
	 *
	 * @return void
	 */
	public static function save( array $settings ): void {
		update_option( Config::SETTINGS_OPTION, $settings, false );
	}
}