import {Service} from '../../../di/src/decorator/Service.ts'
import {Logging} from '../service/logging/Logging.ts'
import LifecycleUnit from './Unit.ts'
import {container, make} from '../../../di/src/global.ts'
import {DependencyKey} from '../../../di/src/type/DependencyKey.ts'
import RunLevelErrorHandler from '../error/RunLevelErrorHandler.ts'
import {Status} from '../const/status.ts'
import Instantiable from '../../../di/src/type/Instantiable.ts'
import {Collection} from '../collection/Collection.ts'
import {path} from '../external/std.ts'

/**
 * Central class for Daton applications.
 */
@Service()
export default class Application {
    /**
     * Collection of LifecycleUnits instantiated by this application.
     * @type Collection<LifecycleUnit>
     */
    protected instantiated_units: Collection<LifecycleUnit> = new Collection<LifecycleUnit>()

    constructor(
        protected logger: Logging,
        protected rleh: RunLevelErrorHandler,
        /**
         * Array of unit classes to run for this application.
         * @type Array<Instantiable<LifecycleUnit>>
         */
        protected units: (Instantiable<LifecycleUnit>)[],
    ) {}

    /**
     * Use the IoC container to instantiate the given dependency key.
     * @param {DependencyKey} token
     */
    make(token: DependencyKey) {
        return make(token)
    }

    /**
     * Get the IoC container.
     * @return Container
     */
    container() {
        return container
    }

    /**
     * Launch the application.
     * @return Promise<void>
     */
    async up() {
        this.logger.info('Starting Daton...', true)
        for ( const unit_class of this.units ) {
            const unit = this.make(unit_class)
            this.instantiated_units.push(unit)
            await this.start_unit(unit)
        }
    }

    /**
     * Stop the application.
     * @return Promise<void>
     */
    async down() {

    }

    /**
     * Run the application.
     * @return Promise<void>
     */
    async run() {
        try {
            await this.up()
            await this.down()
        } catch (e) {
            await this.app_error(e)
        }
    }

    /**
     * Pass an error to the top-level error handler.
     * @param {Error} e
     */
    async app_error(e: Error) {
        this.rleh.handle(e)
    }

    /**
     * Launch the given lifecycle unit.
     * @param {LifecycleUnit} unit
     */
    protected async start_unit(unit: LifecycleUnit) {
        try {
            unit.status = Status.Starting
            this.logger.info(`Starting ${unit.constructor.name}...`)
            await unit.up()
            this.logger.verbose(`Successfully started ${unit.constructor.name}`)
            unit.status = Status.Running
        } catch (e) {
            unit.status = Status.Error
            this.logger.error(`Error encountered while starting ${unit.constructor.name}. Will attempt to proceed.`)
            this.logger.debug(e.message)
            this.logger.verbose(e)
        }
    }

    /**
     * Get the root directory of the application.
     * @type string
     */
    get root() {
        return path.resolve('.')
    }

    /**
     * Get the root directory of application class definitions.
     * @type string
     */
    get app_root() {
        return path.resolve('./app')
    }

    /**
     * Resolve the given path within the application's root.
     * @param {...string} parts
     * @return string
     */
    path(...parts: string[]) {
        return path.resolve(this.root, ...parts)
    }

    /**
     * Resolve the given path within the application's class definition root.
     * @param {...string} parts
     * @return string
     */
    app_path(...parts: string[]) {
        return path.resolve(this.app_root, ...parts)
    }
}