const path = "./csv";
const data = {};
const column = {};
let files = [];

const fs = require("fs");
const papa = require("papaparse");
const chokidar = require("chokidar");

chokidar.watch(path).on("all", () => {
    console.log("File changed. Reloading ...");
    files = fs.readdirSync(`${path}`).filter((file) => file.endsWith(".csv"));
    for (const file of files) {
        const csv = fs.readFileSync(`${path}/${file}`, {
            encoding: "utf8",
        });
        const parsed = papa.parse(csv, {
            skipEmptyLines: true,
        }).data;

        const header = parsed[0];
        column[file] = [];
        for (const h of header) {
            column[file].push({
                key: h,
                text: h,
                sorting: "",
            });
        }

        const converted = [];
        for (let j = 1; j < parsed.length; ++j) {
            const d = parsed[j];
            const e = {};
            for (let i = 0; i < d.length; ++i) {
                e[header[i]] = d[i];
            }
            converted.push(e);
        }
        data[file] = converted;
    }
});

const express = require("express");

const app = express();

const cors = require("cors");

app.use(cors());

const port = 3000;

app.get("/files", (_, res) => {
    res.send(files);
});

function compare(a, b) {
    const m = a - b;
    if (isNaN(m)) {
        if (a > b) {
            return 1;
        }
        if (a < b) {
            return -1;
        }
        return 0;
    }
    return m;
}

app.get("/csv/:file", (req, res) => {
    const {
        file
    } = req.params;
    const raw = data[file];
    const col = column[file];
    let processed = raw;
    let query_key = "";
    let key = "";

    const c = col.find((ele) => {
        key = ele.key;
        query_key = `sort_${key}`;
        return query_key in req.query;
    });
    if (!(c === "undefined")) {
        processed = [...raw];
        if (req.query[query_key] == "ASC") {
            processed.sort((a, b) => compare(a[key], b[key]));
        } else {
            processed.sort((a, b) => compare(b[key], a[key]));
        }
    }

    if ("pSize" in req.query && "cPage" in req.query) {
        const size = req.query.pSize;
        const page = req.query.cPage;
        processed = processed.slice((page - 1) * size, page * size);
    }

    res.send({
        totals: raw.length,
        data: processed,
    });
});

app.use(express.static("public"));

app.get("/column/:file", (req, res) => {
    const {
        file
    } = req.params;
    res.send(column[file]);
});

app.listen(port, () => {
    console.log(`Listening at http://localhost:${port}`);
});