import { NextResponse } from "next/server";
import { unstable_cache as cache } from "next/cache";
import redis from "../../../lib/redis";

// cache response from the db
const getData = cache(
  async (): Promise<{
    total: {
      hits: number;
    };
    pages: Array<{
      slug: string;
      hits: number;
    }>;
  }> => {
    // get all keys (aka slugs)
    const slugs = await redis.scan(0, {
      match: "hits:*",
      type: "string",
      // set an arbitrary yet generous upper limit, just in case...
      count: 99,
    });

    // get the value (number of hits) for each key (the slug of the page)
    const values = await redis.mget<string[]>(...slugs[1]);

    // pair the slugs with their hit values
    const pages = slugs[1].map((slug, index) => ({
      slug: slug.split(":").pop() as string, // remove the "hits:" prefix
      hits: parseInt(values[index], 10),
    }));

    // sort descending by hits
    pages.sort((a, b) => b.hits - a.hits);

    // calculate total hits
    const total = { hits: 0 };
    pages.forEach((page) => {
      // add these hits to running tally
      total.hits += page.hits;
    });

    return { total, pages };
  },
  undefined,
  {
    revalidate: 900, // 15 minutes
    tags: ["hits"],
  }
);

export const GET = async (): Promise<NextResponse<Awaited<ReturnType<typeof getData>>>> =>
  NextResponse.json(await getData());