import { defer, Observable, of } from 'rxjs';
import { catchError, map, mergeMap } from 'rxjs/operators';

import { ResolvedPage, ResolvedPath } from './PageRouter';

import { AppContext, PageModule, PluginFn, PluginParams } from './index';

export function componentLoader(resolved: ResolvedPath, ctx: AppContext): Observable<ResolvedPage> {
    const deferred$ = defer(() => ctx.componentLoader(resolved));
    const mod$: Observable<PageModule> = deferred$;
    return mod$.pipe(
        mergeMap((mod) => {
            if (mod.loadComponent) {
                return mod.loadComponent(resolved, ctx);
            }
            // eslint-disable-next-line @typescript-eslint/consistent-type-assertions
            return of(<ResolvedPage>{ mod, resolved });
        }),
        catchError((e) => {
            console.error('error from component loader', e);
            return (
                deferred$
                    // eslint-disable-next-line @typescript-eslint/consistent-type-assertions
                    .pipe(map((mod) => <ResolvedPage>{ mod, resolved }))
            );
        }),
    );
}

export function componentLoaderPlugin(loaderFn: (resolved: ResolvedPath) => Promise<PageModule>): PluginFn {
    return function (params: PluginParams, appCtx: AppContext): AppContext {
        return {
            ...appCtx,
            componentLoader: loaderFn,
        };
    };
}