import { observable } from 'mobx';
import { getRemoteDataGroupStatus } from 'cbioportal-utils';

export type MobxView = {
    isComplete: boolean;
    isError: boolean;
    isPending: boolean;
} & (
    | {
          status: 'pending' | 'error';
          component: ValidRender;
      }
    | {
          status: 'complete';
          component: ValidRender;
      }
);

type MobxView_await = () => { status: 'complete' | 'error' | 'pending' }[];
type MobxView_render = () => ValidRender;
export type MobxViewAlwaysComponent = MobxView & { component: ValidRender };
type ValidRender = JSX.Element[] | JSX.Element | undefined | null;

export function MakeMobxView(params: {
    await: MobxView_await;
    render: MobxView_render;
    renderError: MobxView_render;
    renderPending: MobxView_render;
    showLastRenderWhenPending?: boolean;
}): MobxViewAlwaysComponent;

export function MakeMobxView(params: {
    await: MobxView_await;
    render: MobxView_render;
    renderError?: MobxView_render;
    renderPending?: MobxView_render;
    showLastRenderWhenPending?: boolean;
}): MobxView;

export function MakeMobxView(params: {
    await: MobxView_await;
    render: MobxView_render;
    renderError?: MobxView_render;
    renderPending?: MobxView_render;
    showLastRenderWhenPending?: boolean;
}): MobxView {
    let hasRendered = false;
    let lastRender: ValidRender;

    return observable({
        get status() {
            const awaitElements = params.await();
            const promiseStatus = getRemoteDataGroupStatus(
                ...awaitElements
            ) as any;
            return promiseStatus;
        },
        get isComplete() {
            return this.status === 'complete';
        },
        get isError() {
            return this.status === 'error';
        },
        get isPending() {
            return this.status === 'pending';
        },
        get component() {
            let ret = null;
            switch (this.status) {
                case 'complete':
                    ret = params.render();
                    hasRendered = true;
                    lastRender = ret;
                    break;
                case 'pending':
                    if (params.showLastRenderWhenPending && hasRendered) {
                        ret = lastRender;
                    } else if (params.renderPending) {
                        ret = params.renderPending();
                    }
                    break;
                case 'error':
                    if (params.renderError) {
                        ret = params.renderError();
                    }
                    break;
            }
            return ret;
        },
    });
}