<?php
/**
 * Tone and style analysis of the posts this site has already published.
 *
 * @package ACS_Article_Generator
 */

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

/**
 * Reads published posts and asks the model to describe how this site writes.
 */
class ACSAGEN_Tone {

	const OPTION = 'acsagen_tone_guide';

	/**
	 * How much of each post is sent for analysis.
	 */
	const EXTRACT_CHARS = 1500;

	/**
	 * The stored style guide.
	 *
	 * @return string
	 */
	public static function get() {
		return (string) get_option( self::OPTION, '' );
	}

	/**
	 * Store a style guide.
	 *
	 * @param string $guide Style guide text.
	 */
	public static function save( $guide ) {
		update_option( self::OPTION, (string) $guide );
	}

	/**
	 * Remove the stored style guide.
	 */
	public static function clear() {
		delete_option( self::OPTION );
	}

	/**
	 * Analyse the most recent published posts.
	 *
	 * @return string|WP_Error The style guide, or an error.
	 */
	public static function analyse() {
		$posts = self::recent_posts( (int) ACSAGEN_Settings::get( 'sample_posts', 10 ) );

		if ( empty( $posts ) ) {
			return new WP_Error(
				'acsagen_no_posts',
				__( 'There are no published posts to learn from yet. Publish at least one post and try again.', 'acs-article-generator' )
			);
		}

		$result = ACSAGEN_Client::generate( self::build_prompt( $posts ) );

		if ( is_wp_error( $result ) ) {
			return $result;
		}

		self::save( $result );

		return $result;
	}

	/**
	 * How many published posts exist.
	 *
	 * @return int
	 */
	public static function published_count() {
		$counts = wp_count_posts( 'post' );
		return isset( $counts->publish ) ? (int) $counts->publish : 0;
	}

	/**
	 * Collect the most recent published posts.
	 *
	 * @param int $count How many posts to collect.
	 * @return array
	 */
	private static function recent_posts( $count ) {
		$count = max( 3, min( 30, (int) $count ) );

		$query = new WP_Query(
			array(
				'post_type'              => 'post',
				'post_status'            => 'publish',
				'posts_per_page'         => $count,
				'orderby'                => 'date',
				'order'                  => 'DESC',
				'ignore_sticky_posts'    => true,
				'no_found_rows'          => true,
				'update_post_meta_cache' => false,
				'update_post_term_cache' => false,
			)
		);

		$posts = array();

		foreach ( $query->posts as $post ) {
			// Password protected posts are not read: their text would end up in
			// the style guide, which every editor can open.
			if ( '' !== (string) $post->post_password ) {
				continue;
			}

			$body = wp_strip_all_tags( strip_shortcodes( (string) $post->post_content ) );
			$body = trim( (string) preg_replace( '/\s+/u', ' ', $body ) );

			if ( '' === $body ) {
				continue;
			}

			$posts[] = array(
				'title'   => (string) $post->post_title,
				'extract' => mb_substr( $body, 0, self::EXTRACT_CHARS ),
			);
		}

		wp_reset_postdata();

		return $posts;
	}

	/**
	 * Build the analysis prompt.
	 *
	 * @param array $posts Posts to analyse.
	 * @return string
	 */
	private static function build_prompt( $posts ) {
		$samples = '';
		$number  = 0;

		foreach ( $posts as $post ) {
			++$number;
			$samples .= "### Post {$number}: {$post['title']}\n{$post['extract']}\n\n";
		}

		$language = ACSAGEN_Settings::language_for_prompt();

		return "You are an editor writing a house style guide.\n"
			. "Below are extracts from posts that have already been published on one WordPress site.\n"
			. "Read them and describe, concretely, how this particular site writes.\n\n"
			. "{$samples}"
			. "---\n\n"
			. "Cover each of the following, and quote short real examples from the extracts wherever you can:\n\n"
			. "1. Sentence endings and register: how formal or casual the writing is, and which endings repeat.\n"
			. "2. Heading style: how h2 and h3 headings are phrased, and how long they are.\n"
			. "3. The usual shape of an article, as a list of sections in order.\n"
			. "4. Calls to action and the wording used to move the reader on.\n"
			. "5. Vocabulary level: how technical terms are handled and how close the writer stands to the reader.\n"
			. "6. Typical article length, and how lists, tables and images are used.\n"
			. "7. Phrases and turns of speech that clearly belong to this site.\n\n"
			. "Write the style guide in {$language}. Use Markdown. Describe only what is actually in the extracts; "
			. 'do not invent rules the posts do not show.';
	}
}