import { makeParameterModifier } from "../Router.ts";
import { FindCursor } from "https://deno.land/x/mongo@v0.31.2/src/collection/commands/find.ts";

export class Page {
    public size?: number;
    public index?: number;

    public apply<T>(cursor: FindCursor<T>) {
        let res = cursor;

        if (this.size !== undefined) {
            if (this.index !== undefined) res = res.skip(this.index * this.size);
            res = res.limit(this.size);
        }

        return res;
    }

    public constructor(size?: number);
    public constructor(size: number, index?: number);
    public constructor(size?: number, index?: number) {
        this.size = size;
        this.index = index;
    }
}

export default function page() {
    return makeParameterModifier(req => {
        let n: number | undefined = Number.parseInt(req.params.n);
        let i: number | undefined = Number.parseInt(req.params.i);

        if (isNaN(n) || n < 1) n = undefined;
        if (isNaN(i) || i < 0) i = undefined;

        if (n === undefined) return new Page();
        else if (i === undefined) return new Page(n);
        else return new Page(n, i);
    });
}