LateLog - Simple storage-based Log Library

Simple library to log to the storage, granting the possibility of viewing the log after the URL changes
Dette scriptet burde ikke installeres direkte. Det er et bibliotek for andre script å inkludere med det nye metadirektivet // @require https://update.greasyfork.org/scripts/461057/1156386/LateLog%20-%20Simple%20storage-based%20Log%20Library.js
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// ==UserScript==
// @name         LateLog - Simple storage-based Log Library
// @namespace    satology.latelog
// @version      0.2
// @description  Simple library to log to the storage, granting the possibility of viewing the log after the URL changes
// @author       satology
// @grant        GM_getValue
// @grant        GM_setValue
// @grant        GM_registerMenuCommand
// ==/UserScript==

var LateLog = (function() {
    'use strict';
    const latelog_getDateTimeString = (date = new Date()) => `${('' + date.getUTCFullYear()).slice(-2)}-${('0' + date.getUTCMonth()).slice(-2)}-${('0' + date.getUTCDate()).slice(-2)} ${('0' + date.getUTCHours()).slice(-2)}:${('0' + date.getUTCMinutes()).slice(-2)}:${('0' + date.getUTCSeconds()).slice(-2)}`;

    class Storage {
        constructor(prefix = '', config = {}) {
            this.prefix = prefix;
            this.config = config;
        }

        write(key, value, parseIt = false) {
            GM_setValue(this.prefix + key, parseIt ? JSON.stringify(value) : value);
        }

        read(key, parseIt = false) {
            let value = GM_getValue(this.prefix + key);
            if(value && parseIt) {
                value = JSON.parse(value);
            }
            return value;
        }
    }

    class LateLog {
        constructor(options = {}) {
            if(!this._isValidSetup(options)) return;
            this.storage = new Storage();
            this.options = {
                level: 5,
                maxLines: 200,
                addTimestamp: true,
                printWhileLogging: false,
                // showDisplayButton: true,
                ...options
            };
            this._init();
        }

        _isValidSetup(options) {
            if(! (typeof GM_getValue === "function" &&
                  typeof GM_setValue === "function" &&
                  typeof GM_registerMenuCommand === "function") ) {
                console.warn(
                    `LateLog cannot be initialized - At least one off the following @grant is missing in your script:
@grant        GM_getValue
@grant        GM_setValue
@grant        GM_registerMenuCommand`);
                return false;
            }
            // TODO: validate options
            return true;
        }

        _init() {
            let that = this;
            GM_registerMenuCommand('View log', function(evt) {
                console.log('Printing LateLog');
                that.display();
            });
            return true;
        }

        _write(msg, msgLevel = 1) {
            if (this.options.level < msgLevel) {
                return;
            }

            let log = this.storage.read('log', true);
            log = log ? log : [];

            if (msg === null) {
                msg = 'null';
            }
            if (msg === undefined) {
                msg = 'undefined';
            }

            let savable = {
                lvl: msgLevel
            };
            if (this.options.addTimestamp) {
                savable.ts = `${latelog_getDateTimeString()}`;
            }
            if (msg instanceof Error) {
                savable.msg = msg.toString();
            } else if (typeof(msg) == 'object') {
                savable.msg = JSON.stringify(msg);
                savable.parse = true;
            } else {
                savable.msg = msg;
            }
            log.push(savable);

            if(log.length > this.options.maxLines) {
                log.splice(0, log.length - this.options.maxLines);
            }

            this.storage.write('log', log, true);
            this._formatPrint(savable);
        }

        _getPrintFn(level) {
            switch(level) {
                case 1:
                    return console.log;
                case 2:
                    return console.info;
                case 3:
                    return console.debug;
                case 4:
                    return console.warn;
                case 5:
                    return console.error;
                default:
                    return console.log;
            }
        }

        _formatPrint(x) {
            if (x.parse) {
                try {
                    x.msg = JSON.parse(x.msg);
                } catch (err) {}
                if (this.options.addTimestamp) {
                    this._getPrintFn(x.lvl)(`${x.ts}:`);
                }
                this._getPrintFn(x.lvl)(x.msg);
            } else {
                this._getPrintFn(x.lvl)(`${this.options.addTimestamp ? x.ts + ' ' : ''} ${x.msg}`);
            }
        }

        clear() { this.storage.write('log', [], true); }

        display() {
            let log = this.storage.read('log', true);
            if(!log) {
                console.log('LateLog - Nothing to show')
                return;
            }

            log.forEach(x => {
                this._formatPrint(x);
            });
        }

        log(msg) { this._write(msg, 1); }

        info(msg) { this._write(msg, 2); }

        debug(msg) { this._write(msg, 3); }

        warn(msg) { this._write(msg, 4); }

        error(msg) { this._write(msg, 5); }
    }
    return LateLog;
})();