<?php
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Handles all AJAX endpoints used by the admin table: scan, generate, save.
 */
class AIATG_Ajax {

	private static $instance = null;

	const NONCE_ACTION = 'aiatg_nonce';

	public static function instance() {
		if ( null === self::$instance ) {
			self::$instance = new self();
		}
		return self::$instance;
	}

	private function __construct() {
		add_action( 'wp_ajax_aiatg_scan', array( $this, 'handle_scan' ) );
		add_action( 'wp_ajax_aiatg_generate', array( $this, 'handle_generate' ) );
		add_action( 'wp_ajax_aiatg_save', array( $this, 'handle_save' ) );
	}

	private function check_request() {
		if ( ! current_user_can( 'upload_files' ) ) {
			wp_send_json_error( array( 'message' => __( 'You do not have permission to do this.', 'fix-experts-ai-image-alt-tag-generator' ) ), 403 );
		}
		check_ajax_referer( self::NONCE_ACTION, 'nonce' );
	}

	public function handle_scan() {
		$this->check_request();

		$items = AIATG_Scanner::scan();

		wp_send_json_success(
			array(
				'items' => $items,
				'count' => count( $items ),
			)
		);
	}

	public function handle_generate() {
		$this->check_request();

		$type  = isset( $_POST['type'] ) ? sanitize_text_field( wp_unslash( $_POST['type'] ) ) : '';
		$id    = isset( $_POST['id'] ) ? absint( $_POST['id'] ) : 0;
		$post_id = isset( $_POST['post_id'] ) ? absint( $_POST['post_id'] ) : 0;
		$src   = isset( $_POST['src'] ) ? esc_url_raw( wp_unslash( $_POST['src'] ) ) : '';

		if ( ! in_array( $type, array( 'attachment', 'content' ), true ) || empty( $src ) ) {
			wp_send_json_error( array( 'message' => __( 'Invalid image reference.', 'fix-experts-ai-image-alt-tag-generator' ) ) );
		}

		$image_data = $this->fetch_image_bytes( $type, $id, $src );
		if ( is_wp_error( $image_data ) ) {
			wp_send_json_error( array( 'message' => $image_data->get_error_message() ) );
		}

		$context = $this->build_context( $type, $id, $post_id );

		$config   = AIATG_Settings::get_active_provider_config();
		$provider = AIATG_AI_Provider::get_provider( $config['provider'], $config['api_key'], $config['model'] );

		if ( is_wp_error( $provider ) ) {
			wp_send_json_error( array( 'message' => $provider->get_error_message() ) );
		}

		$alt_text = $provider->generate( $image_data['bytes'], $image_data['mime'], $context );

		if ( is_wp_error( $alt_text ) ) {
			wp_send_json_error( array( 'message' => $alt_text->get_error_message() ) );
		}

		wp_send_json_success( array( 'alt_text' => $alt_text ) );
	}

	public function handle_save() {
		$this->check_request();

		$type     = isset( $_POST['type'] ) ? sanitize_text_field( wp_unslash( $_POST['type'] ) ) : '';
		$id       = isset( $_POST['id'] ) ? absint( $_POST['id'] ) : 0;
		$post_id  = isset( $_POST['post_id'] ) ? absint( $_POST['post_id'] ) : 0;
		$index    = isset( $_POST['index'] ) ? absint( $_POST['index'] ) : 0;
		$src      = isset( $_POST['src'] ) ? esc_url_raw( wp_unslash( $_POST['src'] ) ) : '';
		$alt_text = isset( $_POST['alt_text'] ) ? sanitize_text_field( wp_unslash( $_POST['alt_text'] ) ) : '';

		if ( '' === trim( $alt_text ) ) {
			wp_send_json_error( array( 'message' => __( 'Alt text cannot be empty.', 'fix-experts-ai-image-alt-tag-generator' ) ) );
		}

		if ( 'attachment' === $type ) {
			if ( ! $id || 'attachment' !== get_post_type( $id ) ) {
				wp_send_json_error( array( 'message' => __( 'Attachment not found.', 'fix-experts-ai-image-alt-tag-generator' ) ) );
			}
			update_post_meta( $id, '_wp_attachment_image_alt', $alt_text );
			wp_send_json_success( array( 'saved' => true ) );
		}

		if ( 'content' === $type ) {
			$post = get_post( $post_id );
			if ( ! $post ) {
				wp_send_json_error( array( 'message' => __( 'Post not found.', 'fix-experts-ai-image-alt-tag-generator' ) ) );
			}
			if ( ! current_user_can( 'edit_post', $post_id ) ) {
				wp_send_json_error( array( 'message' => __( 'You cannot edit this post.', 'fix-experts-ai-image-alt-tag-generator' ) ), 403 );
			}

			$updated_content = AIATG_Scanner::set_content_image_alt( $post->post_content, $index, $alt_text, $src );

			if ( is_wp_error( $updated_content ) ) {
				wp_send_json_error( array( 'message' => $updated_content->get_error_message() ) );
			}

			$result = wp_update_post(
				array(
					'ID'           => $post_id,
					'post_content' => $updated_content,
				),
				true
			);

			if ( is_wp_error( $result ) ) {
				wp_send_json_error( array( 'message' => $result->get_error_message() ) );
			}

			wp_send_json_success( array( 'saved' => true ) );
		}

		wp_send_json_error( array( 'message' => __( 'Invalid save request.', 'fix-experts-ai-image-alt-tag-generator' ) ) );
	}

	/**
	 * Retrieves raw image bytes + mime type, either from local disk
	 * (Media Library attachments) or via HTTP (content images, which may
	 * be external or otherwise not registered as attachments).
	 */
	private function fetch_image_bytes( $type, $id, $src ) {
		if ( 'attachment' === $type && $id ) {
			$path = get_attached_file( $id );
			if ( $path && file_exists( $path ) ) {
				$bytes = file_get_contents( $path );
				$mime  = get_post_mime_type( $id );
				if ( false !== $bytes && $mime ) {
					return array( 'bytes' => $bytes, 'mime' => $mime );
				}
			}
		}

		$response = wp_remote_get(
			$src,
			array(
				'timeout' => 30,
			)
		);

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

		$code = wp_remote_retrieve_response_code( $response );
		if ( $code < 200 || $code >= 300 ) {
			return new WP_Error( 'aiatg_fetch_failed', sprintf( __( 'Could not download image (HTTP %d).', 'fix-experts-ai-image-alt-tag-generator' ), $code ) );
		}

		$bytes = wp_remote_retrieve_body( $response );
		$mime  = wp_remote_retrieve_header( $response, 'content-type' );
		$mime  = $mime ? explode( ';', $mime )[0] : 'image/jpeg';

		if ( empty( $bytes ) ) {
			return new WP_Error( 'aiatg_fetch_empty', __( 'Downloaded image was empty.', 'fix-experts-ai-image-alt-tag-generator' ) );
		}

		return array( 'bytes' => $bytes, 'mime' => trim( $mime ) );
	}

	/**
	 * Builds the site/page context passed to the AI prompt.
	 */
	private function build_context( $type, $id, $post_id ) {
		$context = array(
			'site_name'        => get_bloginfo( 'name' ),
			'site_description' => get_bloginfo( 'description' ),
			'site_context'     => AIATG_Context::get_site_context(),
			'max_length'       => (int) AIATG_Settings::get( 'alt_max_length' ),
		);

		if ( 'attachment' === $type && $id ) {
			$product = AIATG_Context::get_product_context( $id );

			if ( $product ) {
				$context['product_name']        = $product['title'];
				$context['product_categories']  = $product['categories'];
				$context['product_description'] = $product['excerpt'];
				$context['page_title']          = $product['title'];
			} else {
				$parent_id = wp_get_post_parent_id( $id );
				$title     = get_the_title( $parent_id ? $parent_id : $id );
				$caption   = wp_get_attachment_caption( $id );
				$context['page_title'] = $title;
				$context['excerpt']    = $caption ? $caption : '';
			}
		} elseif ( 'content' === $type && $post_id ) {
			$post = get_post( $post_id );
			if ( $post ) {
				$context['page_title'] = get_the_title( $post_id );
				$excerpt               = has_excerpt( $post_id )
					? get_the_excerpt( $post_id )
					: wp_trim_words( wp_strip_all_tags( $post->post_content ), 40 );
				$context['excerpt']    = $excerpt;
			}
		}

		return $context;
	}
}