Logger.ts

/*
 * Filename:
 *      Logger.ts
 * Author:
 *      Pramod Kotipalli (p13i@stanford.edu)
 * Description:
 *      A custom logging service for react-native/expo apps
 *      that provides more verbose options, including printing
 *      the device's name/brand to the console, useful when
 *      debugging multiple devices from the same console output.
 *      More importantly, this library adds time stamps to each
 *      log.
 * Usage:
 *      // At the top of a file, say File.ts
 *      const logger = new Logger('File.ts');
 *
 *      // Inside a function:
 *      function apple(arg1, arg2) {
 *          logger.fn(apple, arg1, arg2);
 *      }
 *
 *      // Anywhere:
 *      const someVar = 'banana';
 *      logger.debug(`I am here with a ${someVar}`, `I can do multiple args`);
 *      // Or:
 *      logger.warn(...);
 *      logger.error(...);
 *      logger.info(...);
 *
 */
import {Platform} from "react-native";
import {stringify} from "./stringify";
import {padStringToLength} from "./padStringToLength";
import * as Device from 'expo-device';

const TIMESTAMP_LENGTH = 20;

const PHONE_DETAILS_LENGTH = 32;

const CONTEXT_LENGTH = 16;

export default class Logger {
    public static instance: Logger = new Logger(`undefined`);
    private readonly _deviceName: string;
    private readonly _brand: string;
    private readonly _context: string;

    constructor(context: string | Function) {
        this._deviceName = Device.deviceName;
        this._brand = Device.brand;
        this._context = typeof(context) === 'function' ? context.name : String(context);
    }

    public fn(functionName: string | Function, ...args: any[]) {
        if (typeof functionName === 'function') {
            functionName = functionName.name;
        }

        console.debug(this._formatFn(functionName, ...args));
    }

    public debug(...args: any[]) {
        console.debug(this._format(...args));
    }

    public info(...args: any[]) {
        console.info(this._format(...args));
    }

    public warn(...args: any[]) {
        console.warn(this._format(...args));
    }

    public error(...args: any[]) {
        console.warn(this._format(...args));
        console.error(...args);
    }

    private _format(...args: any[]) {
        let {timestampString, phoneDetailsStr, contextStr} = this._getCommonStrings();
        let argsString = this._formatObjectArgs(...args);
        return `${timestampString} ${phoneDetailsStr} ${contextStr} ${argsString}`;
    }

    private _getCommonStrings = () => {
        let now = new Date();
        let timestampString = padStringToLength(`[${now.toISOString()}]`, TIMESTAMP_LENGTH);
        let phoneDetailsStr = padStringToLength(`[${this._brand} ${Platform.OS} ${Platform.Version} ${this._deviceName}]`, PHONE_DETAILS_LENGTH);
        let contextStr = padStringToLength(`[${this._context}]`, CONTEXT_LENGTH);
        return {timestampString, phoneDetailsStr, contextStr};
    }

    private _formatFn(functionName: string, ...args: any[]) {
        let {timestampString, phoneDetailsStr, contextStr} = this._getCommonStrings();
        return `${timestampString} ${phoneDetailsStr} ${contextStr} ${functionName}(${args.length > 0 ? this._formatObjectArgs(...args) : ''})`;
    }

    private _formatObjectArgs(...args: any[]) {
        return args.map((arg, index) => Logger._formatObjectArg(arg)).join(', ');
    }

    private static _formatObjectArg(arg: any): string {
        if (typeof arg === 'object') {
            return stringify(arg, /* depth: */ 1);
        }
        return String(arg);
    }
}