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 import {BehaviorSubject, Observable} from 'rxjs';
 
 
 /**
  * Storage general interface for storing ConfigProperty-ies.
  * ConfigProperty uses the storage to save and load values.
  *
  * Time-based Configuration System:
  * - Each configuration value is stored with an associated timestamp
  * - Timestamps are stored in parallel variables with ".time" suffix (e.g., "myConfig" value has "myConfig.time" timestamp)
  * - When setting a value with a specific timestamp, it only updates if the stored timestamp is older
  * - If no timestamp is provided when setting a value, the current time ("now") is used
  * - This allows for conflict resolution when multiple sources might update the same configuration
  */
 interface PersistentPropertyStorage {
   getItem(key: string): string | null;
   setItem(key: string, value: string): void;
 }
 
 /**
  * Use local storage to save load ConfigProperty
  */
 class PersistentPropertyLocalStorage implements PersistentPropertyStorage {
   getItem(key: string): string | null {
     return localStorage.getItem(key);
   }
 
   setItem(key: string, value: string): void {
     localStorage.setItem(key, value);
   }
 }
 
 /**
  * Manages an individual configuration property. Provides reactive updates to subscribers,
  * persistence to localStorage, and optional value validation.
  *
  * Includes time-based update logic to handle concurrent modifications:
  * - Each value is stored with a timestamp
  * - Updates can specify a timestamp to enable conflict resolution
  * - Only updates with newer timestamps will overwrite existing values
  *
  * @template T The type of the configuration value.
  */
 export class PersistentProperty<T> {
   public subject: BehaviorSubject<T>;
 
   /** Observable for subscribers to react to changes in the property value. */
   public changes$: Observable<T>;
   
   /** Track last automatic timestamp to ensure uniqueness */
   private lastAutoTimestamp: number = 0;
 
   /**
    * Creates an instance of ConfigProperty.
    *
    * @param {string} key The localStorage key under which the property value is stored.
    * @param {T} defaultValue The default value of the property if not previously stored.
    * @param storage
    * @param {() => void} saveCallback The callback to execute after setting a new value.
    * @param {(value: T) => boolean} [validator] Optional validator function to validate the property value.
    */
   constructor(
     private key: string,
     private defaultValue: T,
     private saveCallback?: () => void,
     private validator?: (value: T) => boolean,
     private storage: PersistentPropertyStorage = new PersistentPropertyLocalStorage(),
     ) {
     const value = this.loadValue();
     this.subject = new BehaviorSubject<T>(value);
     this.changes$ = this.subject.asObservable();
 
   }
 
 
   /**
    * Loads the property value from localStorage or returns the default value if not found or invalid.
    *
    * @returns {T} The loaded or default value of the property.
    */
   private loadValue(): T {
     let storedValue: string|null = null;
     let parsedValue: any = undefined;
     try {
       storedValue = this.storage.getItem(this.key);
 
       if (storedValue !== null) {
         parsedValue = (typeof this.defaultValue) !== 'string' ? JSON.parse(storedValue) : storedValue;
       } else {
         parsedValue = this.defaultValue;
       }
       return this.validator && !this.validator(parsedValue) ? this.defaultValue : parsedValue;
     } catch (error) {
       console.error(`Error at ConfigProperty.loadValue, key='${this.key}'`);
       console.log('   storedValue', storedValue);
       console.log('   parsedValue', parsedValue);
       console.log('   Default value will be used: ', this.defaultValue);
       console.log(error);
 
       return this.defaultValue;
     }
   }
 
   /**
    * Gets the timestamp of when the current value was stored.
    *
    * @returns {number | null} The timestamp in milliseconds, or null if not found or invalid.
    */
   private getStoredTime(): number | null {
     try {
       const timeKey = `${this.key}.time`;
       const storedTime = this.storage.getItem(timeKey);
       if (!storedTime) {
         return null;
       }
       const parsedTime = parseInt(storedTime, 10);
       // Return null if the timestamp is invalid (NaN)
       return isNaN(parsedTime) ? null : parsedTime;
     } catch (error) {
       console.error(`Error loading timestamp for key='${this.key}'`, error);
       return null;
     }
   }
 
   /**
    * Saves the timestamp for when the value was stored.
    *
    * @param {number} timestamp The timestamp in milliseconds.
    */
   private saveTime(timestamp: number): void {
     const timeKey = `${this.key}.time`;
     this.storage.setItem(timeKey, timestamp.toString());
   }
 
   /**
    * Sets the property value with optional timestamp-based conflict resolution.
    * If a timestamp is provided, the value is only updated if the stored timestamp is older.
    * If no timestamp is provided, the current time is used.
    *
    * @param {T} value The new value to set for the property.
    * @param {number} [time] Optional timestamp in milliseconds. If not provided, Date.now() is used.
    */
   setValue(value: T, time?: number): void {
     if (this.validator && !this.validator(value)) {
       console.error('Validation failed for:', value);
       return;
     }
 
     // If no explicit time provided, use Date.now() but ensure it's unique
     let updateTime: number;
     if (time !== undefined) {
       updateTime = time;
     } else {
       updateTime = Date.now();
       // Ensure timestamp is always increasing for automatic timestamps
       if (updateTime <= this.lastAutoTimestamp) {
         updateTime = this.lastAutoTimestamp + 1;
       }
       this.lastAutoTimestamp = updateTime;
     }
     
     const storedTime = this.getStoredTime();
 
     // Only update if no stored time exists or if the update time is newer
     if (storedTime === null || updateTime > storedTime) {
       this.storage.setItem(this.key, typeof value !== 'string' ? JSON.stringify(value) : value);
       this.saveTime(updateTime);
 
       if(this.saveCallback) {
         this.saveCallback();
       }
 
       this.subject.next(value);
     } else {
       console.log(`Skipping update for key='${this.key}': stored time (${storedTime}) is newer than update time (${updateTime})`);
     }
   }
 
   /**
    * Sets the property value after validation. If the value is valid, it updates the property and calls the save callback.
    * Uses the current timestamp for the update.
    *
    * @param {T} value The new value to set for the property.
    */
   set value(value: T) {
     this.setValue(value);
   }
 
   /**
    * Gets the current value of the property.
    *
    * @returns {T} The current value of the property.
    */
   get value(): T {
     return this.subject.value;
   }
 
 
   /**
    * Resets value to its default given at Config construction
    */
   public setDefault() {
     this.subject.next(this.defaultValue);
   }
 }

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