import {NoSessionKeyError, Session, SessionData, SessionNotLoadedError} from './Session'
import {Inject, Injectable} from '../../di'
import {Cache, Maybe} from '../../util'
import {Config} from '../../service/Config'

/**
 * A Session implementation that uses the configured Cache driver for persistence.
 */
@Injectable()
export class CacheSession extends Session {
    @Inject()
    protected readonly cache!: Cache

    @Inject()
    protected readonly config!: Config

    protected key?: string

    protected data?: SessionData

    protected dirty = false

    forget(key: string): void {
        if ( !this.data ) {
            throw new SessionNotLoadedError()
        }

        delete this.data[key]
        this.dirty = true
    }

    get(key: string, fallback?: unknown): any {
        if ( !this.data ) {
            throw new SessionNotLoadedError()
        }

        return this.data[key] ?? fallback
    }

    getData(): SessionData {
        if ( !this.data ) {
            throw new SessionNotLoadedError()
        }

        return {...this.data}
    }

    getKey(): string {
        if ( !this.key ) {
            throw new NoSessionKeyError()
        }

        return this.key
    }

    async load(): Promise<void> {
        const json = await this.cache.fetch(this.formatKey())
        if ( json ) {
            this.data = JSON.parse(json)
        } else {
            this.data = {}
        }

        this.dirty = false
    }

    async persist(): Promise<void> {
        if ( !this.dirty ) {
            return
        }

        const json = JSON.stringify(this.data)
        await this.cache.put(this.formatKey(), json, this.getExpiration())
        this.dirty = false
    }

    private getExpiration(): Maybe<Date> {
        // Get the session expiration. By default, this is 4 hours.
        const durationMins = this.config.safe('server.session.durationMins')
            .or(4 * 60)
            .integer()

        if ( durationMins !== 0 ) {
            const date = new Date()
            date.setMinutes(date.getMinutes() + durationMins)
            return date
        }
    }

    private formatKey(): string {
        if ( !this.key ) {
            throw new NoSessionKeyError()
        }

        const prefix = this.config.safe('app.name')
            .or('Extollo')
            .string()

        return `${prefix}_session_${this.key}`
    }

    set(key: string, value: unknown): void {
        if ( !this.data ) {
            throw new SessionNotLoadedError()
        }

        this.data[key] = value
        this.dirty = true
    }

    setData(data: SessionData): void {
        this.data = {...data}
        this.dirty = true
    }

    setKey(key: string): void {
        this.key = key
    }
}