import { Status } from '../const/status.ts'
import { Collection } from '../collection/Collection.ts'
import {container} from '../../../di/src/global.ts'
import {isInstantiable} from '../../../di/src/type/Instantiable.ts'
import AppClass from './AppClass.ts'

/**
 * Returns true if the given item is a lifecycle unit.
 * @param something
 * @return boolean
 */
const isLifecycleUnit = (something: any): something is (typeof LifecycleUnit) => {
    return isInstantiable(something) && something.prototype instanceof LifecycleUnit
}

/**
 * Base class representing a single unit of the application lifecycle, responsible
 * for booting and stopping some piece of the application.
 * @extends AppClass
 */
export default abstract class LifecycleUnit extends AppClass {
    /**
     * The current status of the unit.
     * @type Status
     */
    private _status = Status.Stopped

    /**
     * Get the current status of the unit.
     * @type Status
     */
    public get status() {
        return this._status
    }

    /**
     * Set the current status of the unit.
     * @param {Status} status
     */
    public set status(status) {
        this._status = status
    }

    /**
     * Method called to boot and start the unit when the application is starting.
     * @return Promise<void>
     */
    public async up(): Promise<void> {};

    /**
     * Method called to stop the unit when the application is stopping.
     * @return Promise<void>
     */
    public async down(): Promise<void> {};

    /**
     * Returns a collection of lifecycle units that this lifecycle unit depends on.
     * @return Collection<typeof LifecycleUnit>
     */
    public static get_dependencies(): Collection<typeof LifecycleUnit> {
        if ( isInstantiable(this) ) {
            const deps = new Collection<typeof LifecycleUnit>()
            for ( const dependency of container.get_dependencies(this) ) {
                if ( isLifecycleUnit(dependency) )
                    deps.push(dependency)
            }

            return deps
        }
        return new Collection<typeof LifecycleUnit>()
    }
}