import { MapOf } from "@implab/core-amd/interfaces";
import { isPromise, mixin } from "@implab/core-amd/safe";
import { locale as sysLocale } from "dojo/_base/kernel";
import { id as mid } from "module";
import { TraceSource } from "@implab/core-amd/log/TraceSource";

const trace = TraceSource.get(mid);

type PromiseOrValue<T> = PromiseLike<T> | T;
type ResolveCallback<T> = () => PromiseOrValue<T>;

trace.debug("Current sysLocale: {0}", sysLocale);

function when<T, T2>(value: PromiseOrValue<T>, cb: (v: T) => PromiseOrValue<T2>): PromiseOrValue<T2> {
    return isPromise(value) ?
        value.then(cb) :
        cb(value);
}

function isCallback<T>(v: ResolveCallback<T> | PromiseOrValue<T>): v is ResolveCallback<T> {
    return typeof v === "function";
}

function chainObjects<T extends object>(o1: T, o2: T) {
    if (!o1)
        return o2;
    if (!o2)
        return o1;

    return mixin(Object.create(o1) as T, o2);
}

export class NlsBundle<T extends object> {
    _locales: MapOf<ResolveCallback<T> | PromiseOrValue<T>>;
    default: T;

    _cache: MapOf<PromiseOrValue<T>>;

    constructor(defNls: T, locales: MapOf<any>) {
        this.default = defNls;
        this._locales = locales || {};
        this._cache = {};
    }

    getLocale(locale: string) {
        const _loc = locale || sysLocale;

        const locales = new Array<string>();

        _loc.split("-").reduce((a, x) => {
            a.push(x);
            locales.unshift(a.join("-"));
            return a;
        }, []);

        return this._resolveLocale(locales);
    }

    _resolveLocale(locales: string[]): PromiseOrValue<T> {
        if (!locales.length)
            return;

        const locale = locales.shift();

        if (this._cache[locale])
            return this._cache[locale];

        let data = this._locales[locale];
        if (isCallback(data))
            data = data();

        const parent = locales.length ? this._resolveLocale(locales) : this.default;

        return this._cache[locale] = when(data, x => {
            return when(parent, y => this._cache[locale] = chainObjects(y, x));
        });
    }
}