<?php
/**
 * Keyword density analysis for focus terms.
 */
class AIT_AIPSEO_Keyword_Density {

	public function __construct() {
		// reserved
	}

	public function analyze( string $content, array $keywords ): array {
		$content = wp_strip_all_tags( $content );
		$content = strtolower( $content );
		$length  = max( 1, strlen( $content ) );

		$stats = [];
		foreach ( $keywords as $kw ) {
			$kw = trim( strtolower( (string) $kw ) );
			if ( '' === $kw ) { continue; }
			$count = substr_count( $content, $kw ); // naive but fast
			$stats[ $kw ] = [
				'count'   => $count,
				'density' => round( ( $count * max( 1, strlen( $kw ) ) ) / $length * 100, 2 ),
			];
		}
		return $stats;
	}

	public static function get_target_keywords( int $post_id ): array {
		$raw = get_post_meta( $post_id, 'ait_aipseo_target_keywords', true );
		if ( is_array( $raw ) ) { return array_values( array_filter( array_map( 'sanitize_text_field', $raw ) ) ); }
		$line = sanitize_text_field( (string) $raw );
		$parts = array_map( 'trim', explode( ',', $line ) );
		return array_values( array_filter( $parts ) );
	}
}