<?php
/**
 * Answer Opening
 *
 * @package Aisentic\Voice
 */

declare( strict_types = 1 );

namespace Aisentic\Voice;

defined( 'ABSPATH' ) || exit;

/**
 * Makes a refusal start with an apology ("Sorry").
 *
 * If an answer says no, and it starts with a short friendly word such as
 * "No worries", that word is replaced with "Sorry".
 * Why: the prompt had a list of words not to use. The model used a word not
 * on the list ("No worries — I can't create a schedule"). A list of banned
 * words is never complete, so this code checks the shape, not the words.
 *
 * "Short opening" means: at most 5 words, before the first dash, comma or
 * full stop, in the first 40 characters, and not the refusal itself.
 */
class Answer_Opening {

	/**
	 * The opening must end within this many characters.
	 *
	 * "No worries — " is 13. A real first sentence part with the answer in
	 * it is usually longer than this.
	 *
	 * @var int
	 */
	private const HEAD_CHARS = 40;

	/**
	 * How many words an opening fragment may hold.
	 *
	 * @var int
	 */
	private const HEAD_WORDS = 5;

	/**
	 * Openers that are already right for bad news.
	 *
	 * @var string
	 */
	private const APOLOGY_START = '/^(sorry|i\'?m sorry|i am sorry|apologies|unfortunately|i\'?m afraid|i am afraid|afraid)\b/iu';

	/**
	 * Where an opening fragment ends.
	 *
	 * @var string
	 */
	private const BREAK = '/[—–\-,.!?:]/u';

	/**
	 * Put an apology at the front of a refusal.
	 *
	 * @param string $text The answer, or the first sentence of one.
	 * @param string $tone The tone for this answer, as read or guessed.
	 * @return string The answer, opened correctly. Unchanged when it is not a
	 *                refusal, when it already apologises, or when there is no
	 *                short pleasantry in front of the refusal.
	 */
	public static function fix( string $text, string $tone ): string {
		$tag  = '';
		$body = $text;

		if ( preg_match( Text_To_Speech::LEADING_TONE_TAG, $text, $m ) ) {
			$tag  = $m[1];
			$body = (string) substr( $text, strlen( $m[1] ) );
		}

		$trimmed = ltrim( $body );

		if ( '' === $trimmed ) {
			return $text;
		}

		// Not bad news, so the warm word belongs where it is.
		if ( 'sorry' !== $tone && ! preg_match( Text_To_Speech::REFUSAL, $trimmed ) ) {
			return $text;
		}

		// Already opens the right way.
		if ( preg_match( self::APOLOGY_START, $trimmed ) ) {
			return $text;
		}

		$head_zone = mb_substr( $trimmed, 0, self::HEAD_CHARS );

		if ( ! preg_match( self::BREAK, $head_zone, $b, PREG_OFFSET_CAPTURE ) ) {
			// No dash or comma near the start, so there is no short opening.
			// Leave the sentence alone.
			return $text;
		}

		$at   = $b[0][1];
		$head = substr( $trimmed, 0, $at );
		$rest = substr( $trimmed, $at );

		// Keep the space before the dash. Without it, "No worries — I"
		// becomes "Sorry— I".
		$words = rtrim( $head );
		$gap   = substr( $head, strlen( $words ) );

		if ( '' === trim( $words ) ) {
			return $text;
		}

		// Count words with a split, not str_word_count().
		// str_word_count() only works for English letters (ASCII).
		if ( count( preg_split( '/\s+/u', trim( $words ) ) ) > self::HEAD_WORDS ) {
			return $text;
		}

		// The opening is the refusal itself ("I can't — not on a call").
		// Nothing to replace.
		if ( preg_match( Text_To_Speech::REFUSAL, $words ) ) {
			return $text;
		}

		// Only replace the opening when a refusal comes after it.
		// Why: a "sorry" tone alone must not change a normal opening.
		if ( ! preg_match( Text_To_Speech::REFUSAL, $rest ) ) {
			return $text;
		}

		return $tag . __( 'Sorry', 'aisentic' ) . $gap . $rest;
	}
}