add code for the chapter 04.5

Author: ishtms

code/chapter_04.5/.gitignore

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+node_modules/*/**
+test.js

code/chapter_04.5/.vscode/settings.json

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+{
+    "deno.enable": true,
+    "deno.lint": true,
+    "deno.unstable": true
+}

code/chapter_04.5/README.md

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+# A fast, flexible and configurable Logging framework for NodeJS
+
+Master the art of backend development and servers with the free open source book on [github](https://github.com/ishtms/learn-nodejs-hard-way)
+
+> Note: This should not be used in production yet. This is not a complete project.
+![](https://uddrapi.com/api/img?page=logtar%20homepage)

code/chapter_04.5/config.json

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+{
+    "level": 0,
+    "log_prefix": "LogTar_",
+    "rolling_config": {
+        "size_threshold": 10240,
+        "time_threshold": 60
+    }
+}

code/chapter_04.5/index.js

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+module.exports = require('./lib/logtar')

code/chapter_04.5/lib/config/log-config.js

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+const fs = require("node:fs");
+
+const { LogLevel } = require("../utils/log-level");
+const { RollingConfig } = require("./rolling-config");
+
+class LogConfig {
+    /**
+     * @type {LogLevel}
+     * @private
+     * @description The log level to be used.
+     */
+    #level = LogLevel.Info;
+
+    /**
+     * @type {RollingConfig}
+     * @private
+     */
+    #rolling_config;
+
+    /**
+     * @type {string}
+     * @private
+     * @description The prefix to be used for the log file name.
+     *
+     * If the file prefix is `MyFilePrefix_` the log files created will have the name
+     * `MyFilePrefix_2021-09-01.log`, `MyFilePrefix_2021-09-02.log` and so on.
+     */
+    #file_prefix = "Logtar_";
+
+    constructor() {
+        this.#rolling_config = RollingConfig.with_defaults();
+    }
+
+    /**
+     * @returns {LogConfig} A new instance of LogConfig with default values.
+     */
+    static with_defaults() {
+        return new LogConfig();
+    }
+
+    /**
+     * @param {string} file_path The path to the config file.
+     * @returns {LogConfig} A new instance of LogConfig with values from the config file.
+     * @throws {Error} If the file_path is not a string.
+     */
+    static from_file(file_path) {
+        const file_contents = fs.readFileSync(file_path);
+        return LogConfig.from_json(JSON.parse(file_contents));
+    }
+
+    /**
+     * @param {Object} json The json object to be parsed into {LogConfig}.
+     * @returns {LogConfig} A new instance of LogConfig with values from the json object.
+     */
+    static from_json(json) {
+        let log_config = new LogConfig();
+        Object.keys(json).forEach((key) => {
+            switch (key) {
+                case "level":
+                    log_config = log_config.with_log_level(json[key]);
+                    break;
+                case "rolling_config":
+                    log_config = log_config.with_rolling_config(json[key]);
+                    break;
+                case "file_prefix":
+                    log_config = log_config.with_file_prefix(json[key]);
+                    break;
+            }
+        });
+        return log_config;
+    }
+
+    /**
+     * @param {LogConfig} log_config The log config to be validated.
+     * @throws {Error} If the log_config is not an instance of LogConfig.
+     */
+    static assert(log_config) {
+        if (arguments.length > 0 && !(log_config instanceof LogConfig)) {
+            throw new Error(
+                `log_config must be an instance of LogConfig. Unsupported param ${JSON.stringify(log_config)}`
+            );
+        }
+    }
+
+    /**
+     * @returns {LogLevel} The current log level.
+     */
+    get level() {
+        return this.#level;
+    }
+
+    /**
+     * @param {LogLevel} log_level The log level to be set.
+     * @returns {LogConfig} The current instance of LogConfig.
+     * @throws {Error} If the log_level is not an instance of LogLevel.
+     */
+    with_log_level(log_level) {
+        LogLevel.assert(log_level);
+        this.#level = log_level;
+        return this;
+    }
+
+    /**
+     * @returns {RollingConfig} The current rolling config.
+     */
+    get rolling_config() {
+        return this.#rolling_config;
+    }
+
+    /**
+     * @param {RollingConfig} config The rolling config to be set.
+     * @returns {LogConfig} The current instance of LogConfig.
+     * @throws {Error} If the config is not an instance of RollingConfig.
+     */
+    with_rolling_config(config) {
+        this.#rolling_config = RollingConfig.from_json(config);
+        return this;
+    }
+
+    /**
+     * @returns {String} The current max file size.
+     */
+    get file_prefix() {
+        return this.#file_prefix;
+    }
+
+    /**
+     * @param {string} file_prefix The file prefix to be set.
+     * @returns {LogConfig} The current instance of LogConfig.
+     * @throws {Error} If the file_prefix is not a string.
+     */
+    with_file_prefix(file_prefix) {
+        if (typeof file_prefix !== "string") {
+            throw new Error(`file_prefix must be a string. Unsupported param ${JSON.stringify(file_prefix)}`);
+        }
+
+        this.#file_prefix = file_prefix;
+        return this;
+    }
+}
+
+module.exports = { LogConfig };

code/chapter_04.5/lib/config/rolling-config.js

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+const { RollingTimeOptions, RollingSizeOptions } = require("../utils/rolling-options");
+
+class RollingConfig {
+    /**
+     * Roll/Create new file every time the current file size exceeds this threshold in `seconds`.
+     *
+     * @type {RollingTimeOptions}
+     * @private
+     *
+     */
+    #time_threshold = RollingTimeOptions.Hourly;
+
+    /**
+     * @type {RollingSizeOptions}
+     * @private
+     */
+    #size_threshold = RollingSizeOptions.FiveMB;
+
+    /**
+     * @returns {RollingConfig} A new instance of RollingConfig with default values.
+     */
+    static with_defaults() {
+        return new RollingConfig();
+    }
+
+    /**
+     * @param {number} size_threshold Roll/Create new file every time the current file size exceeds this threshold.
+     * @returns {RollingConfig} The current instance of RollingConfig.
+     */
+    with_size_threshold(size_threshold) {
+        RollingSizeOptions.assert(size_threshold);
+        this.#size_threshold = size_threshold;
+        return this;
+    }
+
+    /**
+     * @param {time_threshold} time_threshold Roll/Create new file every time the current file size exceeds this threshold.
+     * @returns {RollingConfig} The current instance of RollingConfig.
+     * @throws {Error} If the time_threshold is not an instance of RollingTimeOptions.
+     */
+    with_time_threshold(time_threshold) {
+        RollingTimeOptions.assert(time_threshold);
+        this.#time_threshold = time_threshold;
+        return this;
+    }
+
+    /**
+     * @param {Object} json The json object to be parsed into {RollingConfig}.
+     * @returns {RollingConfig} A new instance of RollingConfig with values from the json object.
+     * @throws {Error} If the json is not an object.
+     */
+    static from_json(json) {
+        let rolling_config = new RollingConfig();
+
+        Object.keys(json).forEach((key) => {
+            switch (key) {
+                case "size_threshold":
+                    rolling_config = rolling_config.with_size_threshold(json[key]);
+                    break;
+                case "time_threshold":
+                    rolling_config = rolling_config.with_time_threshold(json[key]);
+                    break;
+            }
+        });
+
+        return rolling_config;
+    }
+
+    /**
+     * @returns {RollingTimeOptions} The current time threshold.
+     */
+    get time_threshold() {
+        return this.#time_threshold;
+    }
+
+    /**
+     * @returns {RollingSizeOptions} The current size threshold.
+     */
+    get size_threshold() {
+        return this.#size_threshold;
+    }
+}
+
+module.exports = { RollingConfig };