index.js

const fs = require("fs");

/**
 * Translation system class
 * @class Translate
 */
module.exports = class Translate {

	/**
     * Initialize the class
     *
     * @param {string} files - Files name
     * @param {string} Directory - File path
     * @throws Will throw an error if file does not exist
	 * @constructor
     */
	constructor(files, Directory = "./locales/") {
		this.error = true;
		this.location = Directory;
		this.loc = `${this.location + files}.json`;

		try {
			this.data = JSON.parse(fs.readFileSync(this.loc));
			this.error = false;
		} catch (err) {
			throw new Error("[ERROR] : The translation of the '" + files + "' file is not found !");
		}
	}

	/**
     * Select the line defined by the key
     *
     * @param {string} Lines - Key name
     * @param {null} replace - Replace string in value
     * @throws Will throw an error if key does not exist
     * @returns {string}
     * @constructor
     */
	GetLine(Lines, replace = null) {
		if(!this.error && this.resolve(Lines)) {
			if (replace !== null) {
				return this.resolve(Lines).replace("%s", replace);
			} else {
				return this.resolve(Lines);
			}
		}
		else {
			throw new Error("[ERROR] : This key doesn't exist");
		}

	}

	/**
     * Select block defined by the key
     *
     * @param {string} Lines - Key name
     * @param {null} replaces - Replace string in value
     * @throws Will throw an error if block does not exist
     * @returns {string}
     * @constructor
     */
	GetBlock(Lines, replaces = null) {

		if (!this.error && this.resolve(Lines)) {
			if (replaces) {
				return this.resolve(Lines).replace("%s", replaces);
			}
			return this.resolve(Lines);
		}
		else {
			throw new Error("[ERROR] : This block doesn't exist");
		}
	}

	/**
     * Add a key to the json file
     *
     * @param {string} key - Set key
     * @param {string} value - Set value
     * @throws Will throw an error if key already exists
     * @returns {boolean}
     * @constructor
     */
	SetLine(key, value) {
		if (!this.error && this.resolve(key) !== false) {
			this.data[key] = value;
			fs.writeFileSync(this.loc, JSON.stringify(this.data, null, 2));
			return true;
		}
		else {
			throw new Error("[ERROR] : This key already exists");
		}
	}

	/**
     * Update a key in the json file
     *
     * @param {string} key - Key name
     * @param {string} value - New value
     * @throws Will throw an error if key does not exist
     * @returns {boolean}
     * @constructor
     * @todos Redesign of the function to allow to change the key
     */
	Update(key, value) {
		if (!this.error && this.resolve(key)) {
        	let res = this.resolve(key);
			res = value;
			fs.writeFileSync(this.loc, JSON.stringify(res, null, 2));
			return true;
		}
		else {
			throw new Error("[ERROR] : This key does not exist");
		}

	}

	/**
     * Deletes a key in the json file
     *
     * @param {string} key - Key name
     * @throws Will throw an error if key does not exist
     * @returns {boolean}
     * @constructor
     */
	Del(key) {
		if (!this.error && this.resolve(key)) {
			delete this.resolve(key);
			fs.writeFileSync(this.loc, JSON.stringify(this.data, null, 2));
			return true;
		} else {
			throw new Error("[ERROR] : This key does not exist");
		}

	}

	/**
     * finds a key in the json file
     * @param {string} key - Key name
     * @returns {(string|boolean)} return bool if the key does not exist
	 * @constructor
     */
	resolve(key) {
		if (key.indexOf(".") > -1) {
			return key.split(".").reduce(function (prev, curr) {
				return prev ? prev[curr] : false;
			}, this.data);
		}
		else {
			if (typeof this.data[key] !== "undefined") {
				return this.data[key];
			} else {
				return false;
			}
		}
	}
};