import {Injectable, Inject} from '../../di'
import {ErrorWithContext, Safe} from '../../util'
import {Request} from '../lifecycle/Request'

/**
 * Type alias describing some inflated session data.
 */
export type SessionData = {[key: string]: any}

/**
 * Error thrown when a session is requested for a key that does not exist.
 */
export class NoSessionKeyError extends ErrorWithContext {
    constructor() {
        super('No session ID has been set.')
    }
}

/**
 * Error thrown when a session operation is performed before the session has been loaded.
 */
export class SessionNotLoadedError extends ErrorWithContext {
    constructor() {
        super('Cannot access session data; data is not loaded.')
    }
}

/**
 * An abstract class representing a session driver.
 * Some implementation of this is injected into the request.
 */
@Injectable()
export abstract class Session {
    @Inject()
    protected readonly request!: Request

    /** Get the unique key of this session. */
    public abstract getKey(): string

    /** Set a unique key of this session. */
    public abstract setKey(key: string): void

    /** Load the session data from the respective backend. */
    public abstract load(): void | Promise<void>

    /** Save the session data into the respective backend. */
    public abstract persist(): void | Promise<void>

    /** Get the loaded session data as an object. */
    public abstract getData(): SessionData

    /** Bulk set an object as the session data. */
    public abstract setData(data: SessionData): void

    /** Get a value from the session by key. */
    public abstract get(key: string, fallback?: unknown): any

    /** Set a value in the session by key. */
    public abstract set(key: string, value: unknown): void

    /** Remove a key from the session data. */
    public abstract forget(key: string): void

    /** Load a key from the session as a Safe value. */
    public safe(key: string): Safe {
        return new Safe(this.get(key))
    }
}