import {Inject, Injectable} from '../di'
import {EventBus} from '../event/EventBus'
import {Awaitable, Maybe} from '../util'
import {Authenticatable, AuthenticatableCredentials, AuthenticatableRepository} from './types'
import {UserAuthenticatedEvent} from './event/UserAuthenticatedEvent'
import {UserFlushedEvent} from './event/UserFlushedEvent'
import {UserAuthenticationResumedEvent} from './event/UserAuthenticationResumedEvent'
import {Logging} from '../service/Logging'

/**
 * Base-class for a context that authenticates users and manages security.
 */
@Injectable()
export abstract class SecurityContext {
    @Inject()
    protected readonly bus!: EventBus

    @Inject()
    protected readonly logging!: Logging

    /** The currently authenticated user, if one exists. */
    private authenticatedUser?: Authenticatable

    constructor(
        /** The repository from which to draw users. */
        public readonly repository: AuthenticatableRepository,

        /** The name of this context. */
        public readonly name: string,
    ) { }

    /**
     * Called when the context is created. Can be used by child-classes to do setup work.
     */
    initialize(): Awaitable<void> {}  // eslint-disable-line @typescript-eslint/no-empty-function

    /**
     * Authenticate the given user, without persisting the authentication.
     * That is, when the lifecycle ends, the user will be unauthenticated implicitly.
     * @param user
     */
    async authenticateOnce(user: Authenticatable): Promise<void> {
        this.authenticatedUser = user
        await this.bus.dispatch(new UserAuthenticatedEvent(user, this))
    }

    /**
     * Authenticate the given user and persist the authentication.
     * @param user
     */
    async authenticate(user: Authenticatable): Promise<void> {
        this.authenticatedUser = user
        await this.persist()
        await this.bus.dispatch(new UserAuthenticatedEvent(user, this))
    }

    /**
     * Attempt to authenticate a user based on their credentials.
     * If the credentials are valid, the user will be authenticated, but the authentication
     * will not be persisted. That is, when the lifecycle ends, the user will be
     * unauthenticated implicitly.
     * @param credentials
     */
    async attemptOnce(credentials: AuthenticatableCredentials): Promise<Maybe<Authenticatable>> {
        const user = await this.repository.getByCredentials(credentials)
        if ( user ) {
            await this.authenticateOnce(user)
            return user
        }
    }

    /**
     * Attempt to authenticate a user based on their credentials.
     * If the credentials are valid, the user will be authenticated and the
     * authentication will be persisted.
     * @param credentials
     */
    async attempt(credentials: AuthenticatableCredentials): Promise<Maybe<Authenticatable>> {
        const user = await this.repository.getByCredentials(credentials)
        if ( user ) {
            await this.authenticate(user)
            return user
        }
    }

    /**
     * Unauthenticate the current user, if one exists, but do not persist the change.
     */
    async flushOnce(): Promise<void> {
        const user = this.authenticatedUser
        if ( user ) {
            this.authenticatedUser = undefined
            await this.bus.dispatch(new UserFlushedEvent(user, this))
        }
    }

    /**
     * Unauthenticate the current user, if one exists, and persist the change.
     */
    async flush(): Promise<void> {
        const user = this.authenticatedUser
        if ( user ) {
            this.authenticatedUser = undefined
            await this.persist()
            await this.bus.dispatch(new UserFlushedEvent(user, this))
        }
    }

    /**
     * Assuming a user is still authenticated in the context,
     * try to look up and fill in the user.
     */
    async resume(): Promise<void> {
        const credentials = await this.getCredentials()
        this.logging.debug('resume:')
        this.logging.debug(credentials)
        const user = await this.repository.getByCredentials(credentials)
        if ( user ) {
            this.authenticatedUser = user
            await this.bus.dispatch(new UserAuthenticationResumedEvent(user, this))
        }
    }

    /**
     * Write the current state of the security context to whatever storage
     * medium the context's host provides.
     */
    abstract persist(): Awaitable<void>

    /**
     * Get the credentials for the current user from whatever storage medium
     * the context's host provides.
     */
    abstract getCredentials(): Awaitable<AuthenticatableCredentials>

    /**
     * Get the currently authenticated user, if one exists.
     */
    getUser(): Maybe<Authenticatable> {
        return this.authenticatedUser
    }

    /**
     * Returns true if there is a currently authenticated user.
     */
    hasUser(): boolean {
        this.logging.debug('hasUser?')
        this.logging.debug(this.authenticatedUser)
        return Boolean(this.authenticatedUser)
    }
}