<?php
/**
 * Fixlight's free alt text service: 50 images per site per month, no account.
 *
 * The site registers once (sending only its address and Fixlight version) and
 * gets a token. Each request sends one resized image and the page context; the
 * service passes them to Google Gemini and keeps nothing but usage counters.
 *
 * @package Fixlight
 */

namespace Fixlight;

defined( 'ABSPATH' ) || exit;

/**
 * Hosted provider.
 */
class Ai_Hosted {

	const OPTION = 'fixlight_hosted';

	/**
	 * Base URL of the service.
	 *
	 * @return string
	 */
	public static function base_url() {
		$base = defined( 'FIXLIGHT_API_BASE' ) ? (string) FIXLIGHT_API_BASE : 'https://fixlight.fernwaylabs.com/api';
		/**
		 * Filters the address of Fixlight's alt text service.
		 *
		 * @param string $base Base URL without a trailing slash.
		 */
		return untrailingslashit( (string) apply_filters( 'fixlight_api_base', $base ) );
	}

	/**
	 * Stored registration and quota.
	 *
	 * @return array{token:string,limit:int,remaining:int|null,resets_at:string}
	 */
	public static function state() {
		$state = get_option( self::OPTION, array() );
		$state = is_array( $state ) ? $state : array();
		return array_merge(
			array(
				'token'     => '',
				'limit'     => 50,
				'remaining' => null,
				'resets_at' => '',
				'pro'       => false,
			),
			$state
		);
	}

	/**
	 * Saves registration and quota.
	 *
	 * @param array $state State.
	 */
	private static function save_state( array $state ) {
		update_option( self::OPTION, $state, false );
	}

	/**
	 * Registers this site with the service.
	 *
	 * @return string|\WP_Error Token.
	 */
	public static function register() {
		$response = wp_remote_post(
			self::base_url() . '/v1/sites',
			array(
				'timeout' => 20,
				'headers' => array( 'Content-Type' => 'application/json' ),
				'body'    => wp_json_encode(
					array(
						'site_url' => home_url( '/' ),
						'version'  => FIXLIGHT_VERSION,
					)
				),
			)
		);
		$error    = Ai::http_error( $response, 'Fixlight' );
		if ( $error ) {
			return $error;
		}
		$data = json_decode( wp_remote_retrieve_body( $response ), true );
		if ( empty( $data['token'] ) ) {
			return new \WP_Error( 'fixlight_hosted_register', __( 'The Fixlight service did not register this site. Try again later.', 'fixlight' ), array( 'status' => 502 ) );
		}
		self::save_state(
			array(
				'token'     => (string) $data['token'],
				'limit'     => isset( $data['limit'] ) ? (int) $data['limit'] : 50,
				'remaining' => isset( $data['remaining'] ) ? (int) $data['remaining'] : null,
				'resets_at' => isset( $data['resets_at'] ) ? sanitize_text_field( (string) $data['resets_at'] ) : '',
			)
		);
		return (string) $data['token'];
	}

	/**
	 * Asks the service for alt text.
	 *
	 * @param array  $image   mime, data (base64).
	 * @param array  $context language, text.
	 * @param string $model   Unused; the service picks the model.
	 * @param bool   $retry   Whether a stale token may be replaced once.
	 * @return array|\WP_Error alt, decorative, model, quota.
	 */
	public static function describe( array $image, array $context, $model = '', $retry = true ) {
		$state = self::state();
		$token = $state['token'];
		if ( '' === $token ) {
			$token = self::register();
			if ( is_wp_error( $token ) ) {
				return $token;
			}
		}
		$response = wp_remote_post(
			self::base_url() . '/v1/alt',
			array(
				'timeout' => 45,
				/**
				 * Filters the headers sent to the Fixlight alt text service.
				 * Fixlight Pro adds its site token here, so its plan's allowance applies.
				 *
				 * @param array $headers Request headers.
				 */
				'headers' => (array) apply_filters(
					'fixlight_ai_hosted_headers',
					array(
						'Content-Type'  => 'application/json',
						'Authorization' => 'Bearer ' . $token,
					)
				),
				'body'    => wp_json_encode(
					array(
						'image'    => $image['data'],
						'mime'     => $image['mime'],
						'context'  => $context['text'],
						'language' => $context['language'],
					)
				),
			)
		);
		$code     = is_wp_error( $response ) ? 0 : (int) wp_remote_retrieve_response_code( $response );
		$data     = is_wp_error( $response ) ? array() : json_decode( wp_remote_retrieve_body( $response ), true );
		$data     = is_array( $data ) ? $data : array();

		if ( 401 === $code && $retry ) {
			// The token is unknown (for example after the site moved): register again once.
			self::save_state( array_merge( $state, array( 'token' => '' ) ) );
			return self::describe( $image, $context, $model, false );
		}
		if ( isset( $data['remaining'] ) ) {
			$state = array_merge(
				self::state(),
				array(
					'remaining' => (int) $data['remaining'],
					'limit'     => isset( $data['limit'] ) ? (int) $data['limit'] : 50,
					'resets_at' => isset( $data['resets_at'] ) ? sanitize_text_field( (string) $data['resets_at'] ) : '',
					'pro'       => ! empty( $data['pro'] ),
				)
			);
			self::save_state( $state );
		}
		if ( 429 === $code && isset( $data['error'] ) && 'quota' === $data['error'] ) {
			$date = '' !== $state['resets_at'] ? date_i18n( get_option( 'date_format' ), strtotime( $state['resets_at'] ) ) : '';
			if ( ! empty( $data['pro'] ) ) {
				return new \WP_Error(
					'fixlight_hosted_quota',
					sprintf(
						/* translators: 1: number of images, 2: date. */
						__( 'Your Fixlight Pro plan\'s %1$d AI descriptions for this month are used. They reset on %2$s. You can still write alt text yourself.', 'fixlight' ),
						(int) $state['limit'],
						$date
					) . self::connectors_hint(),
					array( 'status' => 429 )
				);
			}
			return new \WP_Error(
				'fixlight_hosted_quota',
				sprintf(
					/* translators: 1: number of images, 2: date. */
					__( 'This site has used its %1$d free AI descriptions for this month. They reset on %2$s. You can still write alt text yourself.', 'fixlight' ),
					(int) $state['limit'],
					$date
				) . self::connectors_hint(),
				array( 'status' => 429 )
			);
		}
		$error = Ai::http_error( $response, 'Fixlight' );
		if ( $error ) {
			return $error;
		}
		if ( ! array_key_exists( 'alt', $data ) ) {
			return new \WP_Error( 'fixlight_ai_parse', __( 'The Fixlight service returned an answer Fixlight could not read. Try again.', 'fixlight' ), array( 'status' => 502 ) );
		}
		return array(
			'alt'        => (string) $data['alt'],
			'decorative' => ! empty( $data['decorative'] ),
			'model'      => isset( $data['model'] ) ? sanitize_text_field( (string) $data['model'] ) : 'fixlight',
			'quota'      => array(
				'remaining' => $state['remaining'],
				'limit'     => $state['limit'],
				'resets_at' => $state['resets_at'],
			),
		);
	}

	/**
	 * A pointer to the AI connected to WordPress, where this WordPress has it.
	 *
	 * @return string
	 */
	private static function connectors_hint() {
		return Ai_WordPress::available() ? ' ' . __( 'Or choose the AI connected to WordPress in Fixlight → Settings for unlimited descriptions.', 'fixlight' ) : '';
	}
}