import { Deserializable } from '../client/util/SerializationHelper';
import { Field, FieldWaiting, Opt } from './Doc';
import { primitive, serializable } from 'serializr';
import { observable, action, runInAction, computed } from 'mobx';
import { DocServer } from '../client/DocServer';
import { RefField } from './RefField';
import { ObjectField } from './ObjectField';
import { Id, Copy, ToScriptString, ToString, ToValue } from './FieldSymbols';
import { scriptingGlobal } from '../client/util/ScriptingGlobals';

function deserializeProxy(field: any) {
    if (!field.cache.field) {
        field.cache = { field: DocServer.GetCachedRefField(field.fieldId) as any, p: undefined };
    }
}
@Deserializable('proxy', deserializeProxy)
export class ProxyField<T extends RefField> extends ObjectField {
    constructor();
    constructor(value: T);
    constructor(fieldId: string);
    constructor(value?: T | string) {
        super();
        if (typeof value === 'string') {
            //this.cache = DocServer.GetCachedRefField(value) as any;
            this.fieldId = value;
        } else if (value) {
            this.cache = { field: value, p: undefined };
            this.fieldId = value[Id];
        }
    }

    [ToValue](doc: any) {
        return ProxyField.toValue(this);
    }

    [Copy]() {
        if (this.cache.field) return new ProxyField<T>(this.cache.field);
        return new ProxyField<T>(this.fieldId);
    }

    [ToScriptString]() {
        return Field.toScriptString(this[ToValue](undefined)?.value); // not sure this is quite right since it doesn't recreate a proxy field, but better than 'invalid' ?
    }
    [ToString]() {
        return 'ProxyField';
    }

    @serializable(primitive())
    readonly fieldId: string = '';

    // This getter/setter and nested object thing is
    // because mobx doesn't play well with observable proxies
    @observable.ref
    private _cache: { readonly field: T | undefined; p: FieldWaiting<T> | undefined } = { field: undefined, p: undefined };
    private get cache(): { field: T | undefined; p: FieldWaiting<T> | undefined } {
        return this._cache;
    }
    private set cache(val: { field: T | undefined; p: FieldWaiting<T> | undefined }) {
        runInAction(() => (this._cache = { ...val }));
    }

    private failed = false;

    @computed get value(): T | undefined | FieldWaiting<T> {
        if (this.cache.field) return this.cache.field;
        if (this.failed) return undefined;

        this.cache.field = DocServer.GetCachedRefField(this.fieldId) as T;
        if (!this.cache.field && !this.cache.p) {
            this.cache = {
                field: undefined,
                p: DocServer.GetRefField(this.fieldId).then(val => this.setValue(val as T)) as FieldWaiting<T>,
            };
        }
        return this.cache.field ?? this.cache.p;
    }
    @computed get needsRequesting(): boolean {
        return !this.cache.field && !this.failed && !this._cache.p && !DocServer.GetCachedRefField(this.fieldId) ? true : false;
    }

    setExternalValuePromise(externalValuePromise: Promise<any>) {
        this.cache.p = externalValuePromise.then(() => this.value) as FieldWaiting<T>;
    }
    @action
    setValue(field: Opt<T>) {
        this.cache = { field, p: undefined };
        this.failed = field === undefined;
        return field;
    }
}

export namespace ProxyField {
    let useProxy = true;
    export function DisableProxyFields() {
        useProxy = false;
    }

    export function EnableProxyFields() {
        useProxy = true;
    }

    export function WithoutProxy<T>(fn: () => T) {
        DisableProxyFields();
        try {
            return fn();
        } finally {
            EnableProxyFields();
        }
    }

    export function toValue(value: any) {
        if (useProxy) {
            return { value: value.value };
        }
    }
}

function prefetchValue(proxy: PrefetchProxy<RefField>) {
    return proxy.value as any;
}

@scriptingGlobal
@Deserializable('prefetch_proxy', prefetchValue)
export class PrefetchProxy<T extends RefField> extends ProxyField<T> {}