<?php

namespace AchlaAI;

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

final class Lifecycle_Manager {
	const LOCK_TTL                     = 15;
	const PROVISIONING_STATUS_INTERVAL = 10;
	const STATUS_LOCK_OPTION           = 'achlaai_status_refresh_lock';
	const HEARTBEAT_LOCK_OPTION        = 'achlaai_heartbeat_lock';

	/** @var Storage */
	private $storage;

	/** @var Api_Client_Interface */
	private $client;

	/** @var callable */
	private $clock;

	public function __construct( Storage $storage, Api_Client_Interface $client, $clock = null ) {
		$this->storage = $storage;
		$this->client  = $client;
		$this->clock   = null === $clock ? 'time' : $clock;
	}

	/**
	 * GET authoritative status only when due. This does not extend liveness.
	 *
	 * @return array<string,mixed>|\WP_Error
	 */
	public function maybe_status( $reason = 'request', $force = false ) {
		$settings = $this->storage->get();
		$now      = call_user_func( $this->clock );
		if ( ! $this->storage->has_management_binding( $settings ) ) {
			return new \WP_Error( 'status_requires_binding', __( 'Reconnect this site to read its Achla status.', 'achlaai' ), array( 'status' => 409 ) );
		}
		if ( ! $force && (int) $settings['lifecycle']['next_status_check_at'] > $now ) {
			return $settings['lifecycle'];
		}
		if ( ! $this->acquire_lock( self::STATUS_LOCK_OPTION, $now ) ) {
			return $settings['lifecycle'];
		}
		try {
			$result = $this->client->status( $settings['connection'], $this->timeout_for( $reason ) );
			if ( is_wp_error( $result ) ) {
				$this->handle_error( $result, 'status', $now );
				return $result;
			}
			$this->persist_management_status( $settings, $result, false, $now );
			return $result;
		} finally {
			$this->release_lock( self::STATUS_LOCK_OPTION );
		}
	}

	/** @return array<string,mixed>|\WP_Error */
	public function maybe_heartbeat( $reason = 'request', $force = false ) {
		$settings = $this->storage->get();
		$now      = call_user_func( $this->clock );
		if ( ! $this->storage->has_management_binding( $settings ) ) {
			return new \WP_Error( 'heartbeat_requires_binding', __( 'Reconnect this site before sending a heartbeat.', 'achlaai' ), array( 'status' => 409 ) );
		}
		if ( ! $force && (int) $settings['lifecycle']['next_heartbeat_at'] > $now ) {
			return $settings['lifecycle'];
		}
		if ( ! $this->acquire_lock( self::HEARTBEAT_LOCK_OPTION, $now ) ) {
			return $settings['lifecycle'];
		}
		try {
			return $this->heartbeat( $now );
		} finally {
			$this->release_lock( self::HEARTBEAT_LOCK_OPTION );
		}
	}

	/** Run bounded status and liveness maintenance from real requests. */
	public function request_maintenance( $reason = 'request' ) {
		$status = $this->maybe_status( $reason, false );
		if ( is_wp_error( $status ) ) {
			return $status;
		}
		return $this->maybe_heartbeat( $reason, false );
	}

	/** @return array<string,mixed>|\WP_Error */
	public function heartbeat( $now = null ) {
		$now        = null === $now ? call_user_func( $this->clock ) : (int) $now;
		$settings   = $this->storage->get();
		$connection = $settings['connection'];
		if ( ! $this->storage->has_management_binding( $settings ) ) {
			return new \WP_Error( 'heartbeat_requires_binding', __( 'Reconnect this site before sending a heartbeat.', 'achlaai' ), array( 'status' => 409 ) );
		}
		$origin_status = $this->storage->reconcile_origin();
		if ( 'verified' !== $origin_status || in_array( $settings['release']['status'], array( 'blocked', 'killed' ), true )
			|| in_array( $settings['lifecycle']['project_status'], array( 'suspended', 'canceled' ), true )
			|| 'failed' === $settings['lifecycle']['index_status'] ) {
			$connection_status = 'error';
		} elseif ( 'active' !== $settings['lifecycle']['project_status'] || 'ready' !== $settings['lifecycle']['index_status']
			|| 'ready' !== $settings['release']['status'] ) {
			$connection_status = 'degraded';
		} else {
			$connection_status = 'connected';
		}
		$index_status = in_array( $settings['lifecycle']['index_status'], array( 'pending', 'indexing', 'ready', 'failed' ), true )
			? $settings['lifecycle']['index_status']
			: 'unknown';
		$result       = $this->client->heartbeat(
			$connection,
			array(
				'protocol'          => 'aip-management-v1',
				'plugin_version'    => ACHLAAI_VERSION,
				'cms'               => 'wordpress',
				'cms_version'       => get_bloginfo( 'version' ),
				'runtime'           => 'php',
				'runtime_version'   => Protocol::php_runtime_version(),
				'connection_status' => $connection_status,
				'index_status'      => $index_status,
			)
		);
		if ( is_wp_error( $result ) ) {
			$this->handle_error( $result, 'heartbeat', $now );
			return $result;
		}
		$this->persist_management_status( $settings, $result, true, $now );
		return $result;
	}

	private function handle_error( $error, $kind, $now ) {
		$data = $error->get_error_data();
		if ( is_array( $data ) && isset( $data['status'] ) && in_array( (int) $data['status'], array( 401, 403 ), true ) ) {
			$this->storage->revoke_management( 'management_revoked' );
			return;
		}
		$settings                           = $this->storage->get();
		$key                                = 'status' === $kind ? 'status_failures' : 'heartbeat_failures';
		$next_key                           = 'status' === $kind ? 'next_status_check_at' : 'next_heartbeat_at';
		$failures                           = min( 6, (int) $settings['lifecycle'][ $key ] + 1 );
		$delay                              = min( 900, 30 * ( 2 ** ( $failures - 1 ) ) );
		$settings['lifecycle'][ $key ]      = $failures;
		$settings['lifecycle'][ $next_key ] = $now + $delay;
		$this->storage->save( $settings );
	}

	/** @return float */
	private function timeout_for( $reason ) {
		return in_array( $reason, array( 'manual', 'admin' ), true ) ? 4.0 : 2.0;
	}

	/** @return bool */
	private function uses_provisioning_cadence( $settings, $status ) {
		return 'verified' === $settings['connection']['status']
			&& in_array( $status['project']['status'], array( 'registered', 'active' ), true )
			&& in_array( $status['project']['index_status'], array( 'pending', 'indexing' ), true );
	}

	private function persist_management_status( $settings, $status, $heartbeat, $now ) {
		$this->storage->apply_management_status( $status, $heartbeat, $now );
		if ( ! $this->uses_provisioning_cadence( $settings, $status ) ) {
			return;
		}
		$settings                                      = $this->storage->get();
		$settings['lifecycle']['next_status_check_at'] = $now + self::PROVISIONING_STATUS_INTERVAL;
		$this->storage->save( $settings );
	}

	/** @return bool */
	private function acquire_lock( $name, $now ) {
		$expires = get_option( $name, 0 );
		if ( is_numeric( $expires ) && (int) $expires <= $now ) {
			delete_option( $name );
		}
		return add_option( $name, $now + self::LOCK_TTL, '', 'no' );
	}

	private function release_lock( $name ) {
		delete_option( $name );
	}
}