csv-database/csv-editor/index.js

lightweight CSV database

const fastcsv = require("fast-csv");
const fs = require("fs");
const lockfile = require("proper-lockfile");
const tempy = require("tempy");
// Map SIGINT & SIGTERM to process exit
// so that lockfile removes the lockfile automatically
process
    .once("SIGINT", () => process.exit(1))
    .once("SIGTERM", () => process.exit(1));
// lock middleware to ensure async/thread safety
const lock = async (file, next) => new Promise((resolve, reject) => {
    lockfile.lock(file, {
        retries: {
            retries: 500,
            factor: 3,
            minTimeout: 1 * 10,
            maxTimeout: 60 * 1000,
            randomize: true
        }
    }, async (err, release) => {
        if (err) {
            reject(err);
        }
        try {
            await next();
        }
        catch (err) {
            reject(err);
        }
        release();
        resolve();
    });
});
/** file i/o helpers */
const getCsvStream = (file, delimiter) => {
    // append flag : we only work with empty files or adding data
    const fileStream = fs.createWriteStream(file, { flags: "a" });
    const csvStream = fastcsv.createWriteStream({
        headers: true,
        delimiter
    });
    csvStream.pipe(fileStream);
    return csvStream;
};
const copyCsv = (from, to) => new Promise((resolve, reject) => {
    const fromStream = fs.createReadStream(from);
    fromStream.on("error", reject);
    const toStream = fs.createWriteStream(to);
    toStream.on("error", reject).on("close", resolve);
    fromStream.pipe(toStream);
});
/**  */
const read = async (filename, delimiter, events) => new Promise((resolve, reject) => {
    fastcsv
        .fromPath(filename, { delimiter, headers: true })
        .on("data", events.onData)
        .on("error", reject)
        .on("end", resolve);
});
const edit = (filename, delimiter, events) => new Promise((resolve, reject) => {
    const copy = tempy.file();
    const tempStream = getCsvStream(copy, delimiter);
    fastcsv
        .fromPath(filename, { delimiter, headers: true })
        .on("data", data => {
        const newData = events.onEdit(data);
        // handling deletion case when editing returns nothing
        if (newData) {
            tempStream.write(newData);
        }
    })
        .on("error", reject)
        .on("end", () => {
        tempStream.end();
    });
    tempStream.on("end", () => {
        // copy data from tempfile to original file
        copyCsv(copy, filename)
            .then(resolve)
            .catch(reject);
    });
});
const add = (filename, delimiter, data) => new Promise((resolve, reject) => {
    const copy = tempy.file();
    const tempStream = getCsvStream(copy, delimiter);
    fastcsv
        .fromPath(filename, { delimiter, headers: true })
        .on("error", reject)
        .on("end", () => {
        // appending data at end of file
        for (const row of data) {
            tempStream.write(row);
        }
        tempStream.end();
    })
        .pipe(tempStream);
    tempStream.on("end", () => {
        // copy data from tempfile to original file
        copyCsv(copy, filename)
            .then(resolve)
            .catch(reject);
    });
});
const lockedEdit = async (filename, delimiter, events) => {
    const func = async () => edit(filename, delimiter, events);
    return lock(filename, func);
};
const lockedAdd = async (filename, delimiter, data) => {
    const func = async () => add(filename, delimiter, data);
    return lock(filename, func);
};
const csvEditor = (filename, delimiter) => ({
    read: events => read(filename, delimiter, events),
    add: data => lockedAdd(filename, delimiter, data),
    edit: events => lockedEdit(filename, delimiter, events)
});
module.exports = csvEditor;