Source: fileReader.js

const assert = require("assert");
const readline = require("readline");
const fs = require("fs");


/**
 * This function would read file from a path line by line and populate the filecontent
 * object for further processing
 * @param {string} filePath 
 * @param {Readable} testStream : sole purpose of this stream is for testing
 * @returns {Promise} this would resolve when all of the content is read from the file
 */

function fileReader(filePath, testStream) {

    return new Promise((resolve, reject) => {
        try {
            if (!testStream) {
                assert(filePath, "input file path is empty");
            }
            const fileContent = {
                "ships": []
            };
            let lineCount = 0;

            const lineReader = readline.createInterface({
                "input": testStream || fs.createReadStream(filePath)
            });

            lineReader.on("line", function (line) {
                lineCount++;

                switch (true) {
                    case (lineCount === 1):
                        fileContent.AreaDimensions = line.trim();
                        break;
                    case (lineCount === 2):
                        fileContent.shipCount = parseInt(line.trim(), 10);
                        break;
                    case (lineCount > 2 && lineCount <= (fileContent.shipCount + 2)):
                        fileContent.ships.push(line.trim());
                        break;
                    case (lineCount === (fileContent.shipCount + 3)):
                        fileContent.player1Targets = line.trim();
                        break;
                    case (lineCount === (fileContent.shipCount + 4)):
                        fileContent.player2Targets = line.trim();
                        break;
                    default:
                        break;
                }

            });

            lineReader.on("close", function () {
                return resolve(fileContent);
            });
        } catch (error) {
            console.log("Error reading file, Please check the file path", error);
            reject(error);
        }
    });
}

module.exports = fileReader;