Add basic method for passedState

static/js/passedState.js

@@ -1,23 +1,25 @@
 
 
 class PassedState {
+
+    _key = 'passedState';
+    state = null;
+
     constructor(initialState = {}) {
-        const currentState = localStorage.getItem('passedState');
+        const currentState = localStorage.getItem(this._key);
         // initialize the state when there is no state in the local storage.
-        if (!currentState) {
-            if (!initialState) {
-                throw new Error('initial state is required when there is no state in the local storage.');
-            }
-
-            const state = this._prepareState(initialState);
-            localStorage.setItem('passedState', JSON.stringify(state));
-            this.state = state;
-            return;
+        if (!currentState && !initialState) {
+            throw new Error('initial state is required when there is no state in the local storage.');
         }
 
-        if (currentState) {
-            this.state = JSON.parse(currentState);
-        }
+        // add passed property to the challenges in the initial state.
+        const rawState = this._prepareState(initialState);
+
+        // check new state and old state whether is undefined or not. and merge the new state to the old state.
+        const state = this._checkAndMerge(rawState, currentState);
+        this._save(state);
+        this.state = state;
+        return
     }
 
     /**
@@ -26,6 +28,10 @@ class PassedState {
      * @returns state - the state contains the challenge name and whether the challenge is passed.
      */
     _prepareState(rawState) {
+        if (!rawState) {
+            return {};
+        }
+
         const state = {};
         for (const level in rawState) {
             const challenges = [];
@@ -40,4 +46,47 @@ class PassedState {
 
         return state;
     }
+
+    get() {
+        return this.state;
+    }
+
+    _save(state) {
+        localStorage.setItem(this._key, JSON.stringify(state));
+    }
+
+    /**
+     * Set the challenge as passed in the state.
+     * @param {'basic' | 'intermediate' | 'advanced' | 'extreme'} level - the level of the challenge.
+     * @param {string} challengeName - the name of the challenge.
+     * @returns void
+     */
+    setPassed(level, challengeName) {
+        const challenges = this.state[level];
+        for (const challenge of challenges) {
+            if (challenge.name === challengeName) {
+                challenge.passed = true;
+                break;
+            }
+        }
+
+        this._save(this.state);
+    }
+
+    /**
+     * Merge the new state to the current state. this function will compare the new state with the current state and finally overwrite the current state based on the new state: 
+     * - If the old key in the current state is not in the new state, the old key will be removed from the current state. 
+     * - If the new key in the new state is not in the current state, the new key will be added to the current state.
+     * @param {object} newState 
+     */
+    _checkAndMerge(newState, oldState) {
+        if (!newState && !oldState) {
+            throw new Error('one of the new state and the old state is required.');
+        }
+
+        if (!newState) {
+            return oldState;
+        }
+        // TODO: compare the new state with the old state and merge the new state to the old state.
+    }
 }