lib/src/lifecycle/Application.ts

import {Container} from '@extollo/di';
import {
    ErrorWithContext,
    globalRegistry,
    infer,
    isLoggingLevel,
    PathLike,
    StandardLogger,
    universalPath,
    UniversalPath
} from '@extollo/util';

import {Logging} from '../service/Logging';
import {RunLevelErrorHandler} from "./RunLevelErrorHandler";
import {Unit, UnitStatus} from "./Unit";
import * as dotenv from 'dotenv';

export function env(key: string, defaultValue?: any): any {
    return Application.getApplication().env(key, defaultValue)
}

export class Application extends Container {
    public static getContainer(): Container {
        const existing = <Container | undefined> globalRegistry.getGlobal('extollo/injector')
        if ( !existing ) {
            const container = new Application()
            globalRegistry.setGlobal('extollo/injector', container)
            return container
        }

        return existing as Container
    }

    public static getApplication(): Application {
        const existing = <Container | undefined> globalRegistry.getGlobal('extollo/injector')
        if ( existing && !(existing instanceof Application) ) {
            const app = new Application()
            existing.cloneTo(app)

            globalRegistry.setGlobal('extollo/injector', app)
            return app
        } else if ( !existing ) {
            const app = new Application()
            globalRegistry.setGlobal('extollo/injector', app)
            return app
        }

        return existing
    }

    protected baseDir!: string
    protected basePath!: UniversalPath
    protected applicationUnits: (typeof Unit)[] = []
    protected instantiatedUnits: Unit[] = []

    constructor() {
        super()

        if ( !this.hasKey(Application) ) {
            this.register(Application)
            this.instances.push({
                key: Application,
                value: this,
            })
        }

        if ( !this.hasKey('app') ) {
            this.registerSingleton('app', this)
        }
    }

    get root() {
        return this.basePath.concat()
    }

    get appRoot() {
        return this.basePath.concat('app')
    }

    path(...parts: PathLike[]) {
        return this.basePath.concat(...parts)
    }

    appPath(...parts: PathLike[]) {
        return this.basePath.concat('app', ...parts)
    }

    get errorHandler() {
        const rleh: RunLevelErrorHandler = this.make<RunLevelErrorHandler>(RunLevelErrorHandler)
        return rleh.handle
    }

    errorWrapContext(e: Error, context: {[key: string]: any}): ErrorWithContext {
        const rleh: RunLevelErrorHandler = this.make<RunLevelErrorHandler>(RunLevelErrorHandler)
        return rleh.wrapContext(e, context)
    }

    scaffold(absolutePathToApplicationRoot: string, applicationUnits: (typeof Unit)[]) {
        this.baseDir = absolutePathToApplicationRoot
        this.basePath = universalPath(absolutePathToApplicationRoot)
        this.applicationUnits = applicationUnits

        this.bootstrapEnvironment()
        this.setupLogging()

        this.make<Logging>(Logging).debug(`Application root: ${this.baseDir}`)
    }

    protected setupLogging() {
        const standard: StandardLogger = this.make<StandardLogger>(StandardLogger)
        const logging: Logging = this.make<Logging>(Logging)

        logging.registerLogger(standard)

        try {
            logging.verbose('Attempting to load logging level from the environment...')
            const envLevel = this.env('EXTOLLO_LOGGING_LEVEL')
            logging.verbose(`Read logging level: ${envLevel}`)

            if ( isLoggingLevel(envLevel) ) {
                logging.verbose('Logging level is valid.')
                logging.level = envLevel
                logging.debug(`Set logging level from environment: ${envLevel}`)
            }
        } catch(e) {}
    }

    protected bootstrapEnvironment() {
        dotenv.config({
            path: this.basePath.concat('.env').toLocal
        })
    }

    public env(key: string, defaultValue?: any): any {
        return infer(process.env[key] ?? '') ?? defaultValue
    }

    async run() {
        try {
            await this.up()
            await this.down()
        } catch (e) {
            this.errorHandler(e)
        }
    }

    async up() {
        const logging: Logging = this.make<Logging>(Logging)

        logging.info('Starting Extollo...', true)
        for ( const unitClass of this.applicationUnits ) {
            const unit: Unit = this.make<Unit>(unitClass)
            this.instantiatedUnits.push(unit)
            await this.startUnit(unit)
        }
    }

    async down() {
        const logging: Logging = this.make<Logging>(Logging)

        logging.info('Stopping Extollo...', true)
        for ( const unit of this.instantiatedUnits ) {
            if ( !unit ) continue
            await this.stopUnit(unit)
        }
    }

    protected async startUnit(unit: Unit) {
        const logging: Logging = this.make<Logging>(Logging)

        try {
            logging.debug(`Starting ${unit.constructor.name}...`)
            unit.status = UnitStatus.Starting
            await unit.up()
            unit.status = UnitStatus.Started
            logging.info(`Started ${unit.constructor.name}.`)
        } catch (e) {
            unit.status = UnitStatus.Error
            console.log(e)
            throw this.errorWrapContext(e, {unit_name: unit.constructor.name})
        }
    }

    protected async stopUnit(unit: Unit) {
        const logging: Logging = this.make<Logging>(Logging)

        try {
            logging.debug(`Stopping ${unit.constructor.name}...`)
            unit.status = UnitStatus.Stopping
            await unit.down()
            unit.status = UnitStatus.Stopped
            logging.info(`Stopped ${unit.constructor.name}.`)
        } catch (e) {
            unit.status = UnitStatus.Error
            throw this.errorWrapContext(e, {unit_name: unit.constructor.name})
        }
    }
}