import Router from "@koa/router";
import { Context } from "koa";

import { FlatTemplatable, tempstream } from "tempstream";
import type { FormDataValue } from "../forms/form-types.js";
import {
	Fields,
	MountableWithFields,
	PageErrorMessage,
} from "./mountable-with-fields.js";
import { AllQueryParams, PagePropsParser } from "./props-parser.js";

export abstract class Page<
	F extends Fields = Record<string, never>,
> extends MountableWithFields<F> {
	propsParser: PagePropsParser<Record<keyof Fields, unknown>> =
		new AllQueryParams();
	getControls = () => [];

	mount(router: Router, path: string): void {
		router.get(path, async (ctx) => {
			ctx.body = await this.render(ctx);
		});
	}

	async canAccess(_: Context) {
		return { canAccess: true, message: "" };
	}

	async renderError(
		_: Context,
		error: PageErrorMessage
	): Promise<FlatTemplatable> {
		return tempstream /* HTML */ `<div>${error.message}</div>`;
	}

	public abstract render(ctx: Context): Promise<FlatTemplatable>;

	async extractRawValues(
		ctx: Context
	): Promise<Record<string, FormDataValue>> {
		return this.propsParser.decode(ctx) || {};
	}
}