1// PAI Response Streaming System
 2class StreamingPAIEngine {
 3  constructor(apiEndpoint) {
 4    this.apiEndpoint = apiEndpoint;
 5    this.activeStreams = new Map();
 6    this.responseCache = new Map();
 7  }
 8  
 9  // TODO: Implement streaming response with proper async handling
10  async *streamResponse(userInput, options = {}) {
11    const streamId = this.generateStreamId();
12    
13    try {
14      // TODO: Initialize the stream with loading indicator
15      yield { type: 'start', streamId, timestamp: Date.now() };
16      
17      // TODO: Simulate API call with chunks of response
18      const response = await this.fetchPAIResponse(userInput, options);
19      
20      // TODO: Stream the response word by word
21      const words = response.split(' ');
22      
23      for (let i = 0; i < words.length; i++) {
24        // TODO: Yield each word with appropriate delay
25        await this.simulateTypingDelay();
26        
27        yield {
28          type: 'chunk',
29          streamId,
30          content: words[i] + ' ',
31          progress: (i + 1) / words.length,
32          timestamp: Date.now()
33        };
34      }
35      
36      // TODO: Signal completion
37      yield { 
38        type: 'complete', 
39        streamId, 
40        fullResponse: response,
41        timestamp: Date.now() 
42      };
43      
44    } catch (error) {
45      // TODO: Handle streaming errors gracefully
46      yield { 
47        type: 'error', 
48        streamId, 
49        error: error.message,
50        timestamp: Date.now() 
51      };
52    } finally {
53      // TODO: Cleanup stream resources
54      this.activeStreams.delete(streamId);
55    }
56  }
57  
58  // TODO: Implement concurrent PAI processing
59  async processMultipleInputs(inputs) {
60    console.log(`Processing ${inputs.length} inputs concurrently...`);
61    
62    // TODO: Use Promise.allSettled for resilient processing
63    const promises = inputs.map(async (input, index) => {
64      try {
65        // TODO: Add jitter to prevent thundering herd
66        const delay = Math.random() * 1000;
67        await this.delay(delay);
68        
69        const response = await this.fetchPAIResponse(input.text, input.options);
70        
71        return {
72          index,
73          status: 'success',
74          input: input.text,
75          response,
76          processingTime: Date.now() - input.timestamp
77        };
78      } catch (error) {
79        return {
80          index,
81          status: 'error',
82          input: input.text,
83          error: error.message,
84          processingTime: Date.now() - input.timestamp
85        };
86      }
87    });
88    
89    // TODO: Wait for all processing to complete
90    const results = await Promise.allSettled(promises);
91    
92    // TODO: Separate successful and failed results
93    const successful = results.filter(r => r.status === 'fulfilled');
94    const failed = results.filter(r => r.status === 'rejected');
95    
96    console.log(`✅ ${successful.length} successful, ❌ ${failed.length} failed`);
97    
98    return { successful, failed, total: inputs.length };
99  }
100  
101  // TODO: Implement smart response caching
102  async getCachedOrFetchResponse(userInput, options = {}) {
103    const cacheKey = this.generateCacheKey(userInput, options);
104    
105    // TODO: Check cache first
106    if (this.responseCache.has(cacheKey)) {
107      console.log('💾 Cache hit for:', userInput.substring(0, 30) + '...');
108      return {
109        response: this.responseCache.get(cacheKey),
110        fromCache: true,
111        timestamp: Date.now()
112      };
113    }
114    
115    // TODO: Fetch fresh response
116    console.log('🌐 Fetching fresh response for:', userInput.substring(0, 30) + '...');
117    
118    try {
119      const response = await this.fetchPAIResponse(userInput, options);
120      
121      // TODO: Cache the response with TTL
122      this.responseCache.set(cacheKey, response);
123      
124      // TODO: Implement cache eviction after 5 minutes
125      setTimeout(() => {
126        this.responseCache.delete(cacheKey);
127        console.log('🗑️ Evicted cache for:', cacheKey);
128      }, 5 * 60 * 1000);
129      
130      return {
131        response,
132        fromCache: false,
133        timestamp: Date.now()
134      };
135      
136    } catch (error) {
137      // TODO: Handle fetch errors
138      throw new Error(`PAI fetch failed: ${error.message}`);
139    }
140  }
141  
142  // Helper methods (TODO: Implement these)
143  generateStreamId() {
144    return 'stream_' + Math.random().toString(36).substr(2, 9);
145  }
146  
147  generateCacheKey(input, options) {
148    return btoa(JSON.stringify({ input, options }));
149  }
150  
151  async simulateTypingDelay() {
152    // TODO: Simulate realistic typing speed (30-60 WPM)
153    const baseDelay = 100; // milliseconds
154    const randomJitter = Math.random() * 50;
155    await this.delay(baseDelay + randomJitter);
156  }
157  
158  async delay(ms) {
159    return new Promise(resolve => setTimeout(resolve, ms));
160  }
161  
162  async fetchPAIResponse(userInput, options) {
163    // TODO: Simulate API call with realistic delay
164    const processingTime = Math.random() * 2000 + 500; // 500-2500ms
165    await this.delay(processingTime);
166    
167    // TODO: Simulate occasional failures
168    if (Math.random() < 0.1) { // 10% failure rate
169      throw new Error('PAI service temporarily unavailable');
170    }
171    
172    // TODO: Generate contextual response
173    const responses = [
174      `Based on your input "${userInput}", I understand you're looking for assistance with PAI development.`,
175      `That's an interesting question about "${userInput}". Let me provide a comprehensive response.`,
176      `I can help you with "${userInput}". Here's what I think would be most valuable.`,
177      `Great question about "${userInput}"! This touches on several important PAI concepts.`
178    ];
179    
180    return responses[Math.floor(Math.random() * responses.length)];
181  }
182}
183
184// TODO: Implement the User Interface Controller
185class PAIStreamingUI {
186  constructor(paiEngine) {
187    this.paiEngine = paiEngine;
188    this.activeStreams = new Set();
189    this.setupEventListeners();
190  }
191  
192  setupEventListeners() {
193    // TODO: Set up input handlers
194    const inputElement = document.getElementById('user-input');
195    const sendButton = document.getElementById('send-button');
196    
197    sendButton?.addEventListener('click', () => this.handleUserInput());
198    inputElement?.addEventListener('keypress', (e) => {
199      if (e.key === 'Enter' && !e.shiftKey) {
200        e.preventDefault();
201        this.handleUserInput();
202      }
203    });
204  }
205  
206  async handleUserInput() {
207    const inputElement = document.getElementById('user-input');
208    const userInput = inputElement?.value.trim();
209    
210    if (!userInput) return;
211    
212    // TODO: Clear input and show typing indicator
213    inputElement.value = '';
214    this.showTypingIndicator();
215    
216    try {
217      // TODO: Create response container
218      const responseContainer = this.createResponseContainer();
219      
220      // TODO: Stream the response
221      const responseStream = this.paiEngine.streamResponse(userInput);
222      
223      for await (const chunk of responseStream) {
224        this.handleStreamChunk(chunk, responseContainer);
225      }
226      
227    } catch (error) {
228      this.showError(error.message);
229    } finally {
230      this.hideTypingIndicator();
231    }
232  }
233  
234  handleStreamChunk(chunk, container) {
235    switch (chunk.type) {
236      case 'start':
237        // TODO: Initialize response display
238        container.innerHTML = '<span class="cursor">▊</span>';
239        break;
240        
241      case 'chunk':
242        // TODO: Append new content
243        const existingText = container.textContent.replace('▊', '');
244        container.innerHTML = existingText + chunk.content + '<span class="cursor">▊</span>';
245        
246        // TODO: Auto-scroll to bottom
247        container.scrollIntoView({ behavior: 'smooth', block: 'end' });
248        break;
249        
250      case 'complete':
251        // TODO: Remove cursor and finalize
252        container.innerHTML = chunk.fullResponse;
253        container.classList.add('complete');
254        break;
255        
256      case 'error':
257        // TODO: Show error state
258        container.innerHTML = `<span class="error">❌ ${chunk.error}</span>`;
259        break;
260    }
261  }
262  
263  // TODO: Implement UI helper methods
264  createResponseContainer() {
265    const container = document.createElement('div');
266    container.className = 'pai-response streaming';
267    document.getElementById('chat-container')?.appendChild(container);
268    return container;
269  }
270  
271  showTypingIndicator() {
272    // TODO: Show "PAI is thinking..." indicator
273    const indicator = document.getElementById('typing-indicator');
274    if (indicator) {
275      indicator.style.display = 'block';
276      indicator.innerHTML = '🤔 PAI is thinking...';
277    }
278  }
279  
280  hideTypingIndicator() {
281    const indicator = document.getElementById('typing-indicator');
282    if (indicator) {
283      indicator.style.display = 'none';
284    }
285  }
286  
287  showError(message) {
288    const errorContainer = document.createElement('div');
289    errorContainer.className = 'error-message';
290    errorContainer.innerHTML = `❌ Error: ${message}`;
291    document.getElementById('chat-container')?.appendChild(errorContainer);
292  }
293}
294
295// TODO: Test your implementation
296async function testStreamingPAI() {
297  const paiEngine = new StreamingPAIEngine('https://api.example.com/pai');
298  const ui = new PAIStreamingUI(paiEngine);
299  
300  // Test 1: Single streaming response
301  console.log('🧪 Test 1: Single streaming response');
302  const singleStream = paiEngine.streamResponse('How does async JavaScript work?');
303  
304  for await (const chunk of singleStream) {
305    console.log('Chunk:', chunk);
306  }
307  
308  // Test 2: Multiple concurrent inputs
309  console.log('\n🧪 Test 2: Multiple concurrent inputs');
310  const multipleInputs = [
311    { text: 'Explain duck typing', options: {}, timestamp: Date.now() },
312    { text: 'What is async/await?', options: {}, timestamp: Date.now() },
313    { text: 'How do promises work?', options: {}, timestamp: Date.now() }
314  ];
315  
316  const results = await paiEngine.processMultipleInputs(multipleInputs);
317  console.log('Batch results:', results);
318  
319  // Test 3: Caching behavior
320  console.log('\n🧪 Test 3: Caching behavior');
321  const input = 'What is PAI development?';
322  
323  const first = await paiEngine.getCachedOrFetchResponse(input);
324  console.log('First call:', first);
325  
326  const second = await paiEngine.getCachedOrFetchResponse(input);
327  console.log('Second call (should be cached):', second);
328}
329
330// Run tests if in Node.js environment
331if (typeof window === 'undefined') {
332  testStreamingPAI().catch(console.error);
333}

 1// Multi-Modal PAI Input Processor
 2class MultiModalPAIProcessor {
 3  constructor() {
 4    this.inputProcessors = {
 5      voice: new VoiceInputProcessor(),
 6      text: new TextInputProcessor(), 
 7      gesture: new GestureInputProcessor(),
 8      neural: new NeuralInputProcessor()
 9    };
10    
11    this.eventEmitter = new EventTarget();
12    this.processingQueue = [];
13    this.isProcessing = false;
14  }
15  
16  // TODO: Implement concurrent input processing
17  async processInput(inputData, modality) {
18    console.log(`📥 Processing ${modality} input:`, inputData.preview);
19    
20    try {
21      // TODO: Get the appropriate processor
22      const processor = this.inputProcessors[modality];
23      
24      if (!processor) {
25        throw new Error(`No processor found for modality: ${modality}`);
26      }
27      
28      // TODO: Process input with timeout protection
29      const timeoutPromise = new Promise((_, reject) => {
30        setTimeout(() => reject(new Error('Input processing timeout')), 10000);
31      });
32      
33      const processingPromise = processor.processInput(inputData);
34      
35      // TODO: Race between processing and timeout
36      const result = await Promise.race([processingPromise, timeoutPromise]);
37      
38      // TODO: Emit success event
39      this.eventEmitter.dispatchEvent(new CustomEvent('inputProcessed', {
40        detail: {
41          modality,
42          inputData,
43          result,
44          timestamp: Date.now()
45        }
46      }));
47      
48      return result;
49      
50    } catch (error) {
51      // TODO: Emit error event
52      this.eventEmitter.dispatchEvent(new CustomEvent('inputError', {
53        detail: {
54          modality,
55          inputData,
56          error: error.message,
57          timestamp: Date.now()
58        }
59      }));
60      
61      throw error;
62    }
63  }
64  
65  // TODO: Implement smart input fusion
66  async fuseMultiModalInputs(inputs) {
67    console.log(`🔄 Fusing ${inputs.length} multi-modal inputs`);
68    
69    // TODO: Process all inputs concurrently
70    const processingPromises = inputs.map(async (input) => {
71      try {
72        const result = await this.processInput(input.data, input.modality);
73        return {
74          modality: input.modality,
75          success: true,
76          result,
77          confidence: result.confidence || 0.5,
78          timestamp: Date.now()
79        };
80      } catch (error) {
81        return {
82          modality: input.modality,
83          success: false,
84          error: error.message,
85          confidence: 0,
86          timestamp: Date.now()
87        };
88      }
89    });
90    
91    // TODO: Wait for all to complete (don't fail fast)
92    const results = await Promise.allSettled(processingPromises);
93    
94    // TODO: Implement fusion algorithm
95    const successfulResults = results
96      .filter(r => r.status === 'fulfilled' && r.value.success)
97      .map(r => r.value);
98    
99    if (successfulResults.length === 0) {
100      throw new Error('All input modalities failed to process');
101    }
102    
103    // TODO: Weighted fusion based on confidence scores
104    const fusedResult = this.weightedFusion(successfulResults);
105    
106    return {
107      fusedResult,
108      individualResults: results,
109      processingTime: Date.now() - inputs[0].timestamp
110    };
111  }
112  
113  // TODO: Implement weighted fusion algorithm
114  weightedFusion(results) {
115    // TODO: Calculate total confidence
116    const totalConfidence = results.reduce((sum, r) => sum + r.confidence, 0);
117    
118    if (totalConfidence === 0) {
119      // TODO: Fallback to simple average
120      return {
121        intent: 'unclear',
122        confidence: 0,
123        text: 'Could not determine user intent',
124        modalities: results.map(r => r.modality)
125      };
126    }
127    
128    // TODO: Weighted average of results
129    let fusedText = '';
130    let fusedIntent = '';
131    let maxConfidence = 0;
132    
133    results.forEach(result => {
134      const weight = result.confidence / totalConfidence;
135      
136      // TODO: Choose highest confidence intent
137      if (result.confidence > maxConfidence) {
138        maxConfidence = result.confidence;
139        fusedIntent = result.result.intent;
140      }
141      
142      // TODO: Concatenate text with weights
143      if (result.result.text) {
144        fusedText += `[${result.modality}:${(weight * 100).toFixed(1)}%] ${result.result.text} `;
145      }
146    });
147    
148    return {
149      intent: fusedIntent,
150      confidence: maxConfidence,
151      text: fusedText.trim(),
152      modalities: results.map(r => r.modality),
153      fusionWeights: results.map(r => ({
154        modality: r.modality,
155        weight: r.confidence / totalConfidence
156      }))
157    };
158  }
159}
160
161// TODO: Implement individual input processors
162class VoiceInputProcessor {
163  async processInput(audioData) {
164    // TODO: Simulate voice recognition processing
165    await this.delay(Math.random() * 1500 + 500); // 500-2000ms
166    
167    // TODO: Simulate occasional recognition failures
168    if (Math.random() < 0.15) { // 15% failure rate
169      throw new Error('Voice recognition failed - unclear audio');
170    }
171    
172    // TODO: Return processed voice data
173    return {
174      text: audioData.transcript || 'Simulated voice transcription',
175      intent: this.detectIntent(audioData.transcript),
176      confidence: Math.random() * 0.4 + 0.6, // 0.6-1.0
177      language: audioData.language || 'en',
178      processingTime: Date.now() - audioData.timestamp
179    };
180  }
181  
182  detectIntent(text) {
183    // TODO: Simple intent detection
184    const intents = {
185      'hello': 'greeting',
186      'help': 'assistance',
187      'what': 'question',
188      'how': 'tutorial',
189      'show': 'demonstration',
190      'explain': 'explanation'
191    };
192    
193    for (const [keyword, intent] of Object.entries(intents)) {
194      if (text?.toLowerCase().includes(keyword)) {
195        return intent;
196      }
197    }
198    
199    return 'general';
200  }
201  
202  delay(ms) {
203    return new Promise(resolve => setTimeout(resolve, ms));
204  }
205}
206
207class TextInputProcessor {
208  async processInput(textData) {
209    // TODO: Simulate text processing (faster than voice)
210    await this.delay(Math.random() * 300 + 100); // 100-400ms
211    
212    return {
213      text: textData.content,
214      intent: this.detectIntent(textData.content),
215      confidence: 0.9, // Text is generally more reliable
216      sentiment: this.analyzeSentiment(textData.content),
217      processingTime: Date.now() - textData.timestamp
218    };
219  }
220  
221  detectIntent(text) {
222    // TODO: More sophisticated text intent detection
223    if (text.includes('?')) return 'question';
224    if (text.includes('please') || text.includes('can you')) return 'request';
225    if (text.includes('thank')) return 'gratitude';
226    if (text.includes('hello') || text.includes('hi')) return 'greeting';
227    return 'statement';
228  }
229  
230  analyzeSentiment(text) {
231    // TODO: Simple sentiment analysis
232    const positiveWords = ['good', 'great', 'awesome', 'excellent', 'amazing'];
233    const negativeWords = ['bad', 'terrible', 'awful', 'horrible', 'disappointing'];
234    
235    const positive = positiveWords.some(word => text.toLowerCase().includes(word));
236    const negative = negativeWords.some(word => text.toLowerCase().includes(word));
237    
238    if (positive && !negative) return 'positive';
239    if (negative && !positive) return 'negative';
240    return 'neutral';
241  }
242  
243  delay(ms) {
244    return new Promise(resolve => setTimeout(resolve, ms));
245  }
246}
247
248class GestureInputProcessor {
249  async processInput(gestureData) {
250    // TODO: Simulate gesture recognition processing  
251    await this.delay(Math.random() * 1000 + 800); // 800-1800ms
252    
253    // TODO: Higher failure rate for gestures
254    if (Math.random() < 0.25) { // 25% failure rate
255      throw new Error('Gesture not recognized');
256    }
257    
258    return {
259      text: `Gesture: ${gestureData.type}`,
260      intent: this.mapGestureToIntent(gestureData.type),
261      confidence: Math.random() * 0.3 + 0.4, // 0.4-0.7
262      gestureType: gestureData.type,
263      processingTime: Date.now() - gestureData.timestamp
264    };
265  }
266  
267  mapGestureToIntent(gestureType) {
268    const gestureMap = {
269      'wave': 'greeting',
270      'point': 'selection',
271      'thumbs_up': 'approval',
272      'thumbs_down': 'disapproval',
273      'swipe_left': 'navigation',
274      'swipe_right': 'navigation',
275      'tap': 'interaction'
276    };
277    
278    return gestureMap[gestureType] || 'unknown_gesture';
279  }
280  
281  delay(ms) {
282    return new Promise(resolve => setTimeout(resolve, ms));
283  }
284}
285
286// TODO: Implement the main test function
287async function testMultiModalProcessing() {
288  const processor = new MultiModalPAIProcessor();
289  
290  // TODO: Set up event listeners
291  processor.eventEmitter.addEventListener('inputProcessed', (event) => {
292    console.log('✅ Input processed:', event.detail);
293  });
294  
295  processor.eventEmitter.addEventListener('inputError', (event) => {
296    console.log('❌ Input error:', event.detail);
297  });
298  
299  // Test 1: Single modality processing
300  console.log('🧪 Test 1: Single modality processing');
301  
302  try {
303    const voiceResult = await processor.processInput({
304      transcript: 'Hello, can you help me?',
305      timestamp: Date.now(),
306      preview: 'Hello, can you help me?'
307    }, 'voice');
308    
309    console.log('Voice result:', voiceResult);
310  } catch (error) {
311    console.log('Voice processing failed:', error.message);
312  }
313  
314  // Test 2: Multi-modal fusion
315  console.log('\n🧪 Test 2: Multi-modal fusion');
316  
317  const multiModalInputs = [
318    {
319      modality: 'voice',
320      data: {
321        transcript: 'Show me the weather',
322        timestamp: Date.now(),
323        preview: 'Show me the weather'
324      }
325    },
326    {
327      modality: 'text',
328      data: {
329        content: 'What is the weather like today?',
330        timestamp: Date.now(),
331        preview: 'What is the weather like today?'
332      }
333    },
334    {
335      modality: 'gesture',
336      data: {
337        type: 'point',
338        timestamp: Date.now(),
339        preview: 'pointing gesture'
340      }
341    }
342  ];
343  
344  try {
345    const fusionResult = await processor.fuseMultiModalInputs(multiModalInputs);
346    console.log('Fusion result:', fusionResult);
347  } catch (error) {
348    console.log('Multi-modal fusion failed:', error.message);
349  }
350}
351
352// Run test
353testMultiModalProcessing().catch(console.error);

 1// Performance Testing Suite
 2class AsyncPerformanceTester {
 3  constructor() {
 4    this.testResults = [];
 5  }
 6  
 7  async benchmarkApproach(name, testFunction, iterations = 100) {
 8    console.log(`🏃‍♂️ Benchmarking: ${name}`);
 9    
10    const startTime = performance.now();
11    const promises = [];
12    
13    for (let i = 0; i < iterations; i++) {
14      promises.push(testFunction());
15    }
16    
17    // TODO: Choose the right Promise method for your test
18    const results = await Promise.all(promises);
19    
20    const endTime = performance.now();
21    const duration = endTime - startTime;
22    
23    const result = {
24      name,
25      duration: duration.toFixed(2),
26      throughput: (iterations / (duration / 1000)).toFixed(2),
27      successRate: this.calculateSuccessRate(results),
28      timestamp: Date.now()
29    };
30    
31    this.testResults.push(result);
32    console.log(`✅ ${name}: ${result.duration}ms, ${result.throughput} ops/sec`);
33    
34    return result;
35  }
36  
37  // TODO: Test different concurrency patterns
38  async runPerformanceTests() {
39    // Test 1: Promise.all (fail-fast)
40    await this.benchmarkApproach('Promise.all', async () => {
41      const promises = [
42        this.simulateAPICall(100),
43        this.simulateAPICall(150),
44        this.simulateAPICall(200)
45      ];
46      return Promise.all(promises);
47    });
48    
49    // Test 2: Promise.allSettled (resilient)  
50    await this.benchmarkApproach('Promise.allSettled', async () => {
51      const promises = [
52        this.simulateAPICall(100),
53        this.simulateAPICall(150), 
54        this.simulateAPICall(200)
55      ];
56      return Promise.allSettled(promises);
57    });
58    
59    // Test 3: Sequential processing
60    await this.benchmarkApproach('Sequential', async () => {
61      await this.simulateAPICall(100);
62      await this.simulateAPICall(150);
63      await this.simulateAPICall(200);
64    });
65    
66    // TODO: Analyze and display results
67    this.displayResults();
68  }
69  
70  async simulateAPICall(delay) {
71    await new Promise(resolve => setTimeout(resolve, delay));
72    
73    // TODO: Simulate random failures
74    if (Math.random() < 0.1) {
75      throw new Error('Simulated API failure');
76    }
77    
78    return { success: true, delay };
79  }
80  
81  calculateSuccessRate(results) {
82    if (!Array.isArray(results)) return 100;
83    
84    const successful = results.filter(r => 
85      r.status === 'fulfilled' || (r.status !== 'rejected' && !r.error)
86    ).length;
87    
88    return ((successful / results.length) * 100).toFixed(1);
89  }
90  
91  displayResults() {
92    console.log('\n📊 Performance Test Results:');
93    console.table(this.testResults);
94    
95    // TODO: Find the fastest approach
96    const fastest = this.testResults.reduce((prev, current) => 
97      parseFloat(prev.duration) < parseFloat(current.duration) ? prev : current
98    );
99    
100    console.log(`🏆 Fastest approach: ${fastest.name} (${fastest.duration}ms)`);
101  }
102}
103
104// TODO: Run performance tests
105const tester = new AsyncPerformanceTester();
106tester.runPerformanceTests().catch(console.error);

 1class ResilientPAINetwork {
 2  constructor(endpoints) {
 3    this.endpoints = endpoints;
 4    this.circuitBreakers = new Map();
 5    this.retryStrategies = new Map();
 6    this.healthStatus = new Map();
 7    
 8    // TODO: Initialize circuit breakers for each endpoint
 9    endpoints.forEach(endpoint => {
10      this.circuitBreakers.set(endpoint, new CircuitBreaker(endpoint));
11      this.healthStatus.set(endpoint, 'unknown');
12    });
13    
14    // TODO: Start health monitoring
15    this.startHealthMonitoring();
16  }
17  
18  // TODO: Implement circuit breaker pattern
19  async callWithCircuitBreaker(endpoint, operation) {
20    const circuitBreaker = this.circuitBreakers.get(endpoint);
21    
22    if (circuitBreaker.isOpen()) {
23      throw new Error(`Circuit breaker OPEN for ${endpoint}`);
24    }
25    
26    try {
27      const result = await operation();
28      circuitBreaker.recordSuccess();
29      return result;
30    } catch (error) {
31      circuitBreaker.recordFailure();
32      throw error;
33    }
34  }
35  
36  // TODO: Implement smart retry with exponential backoff
37  async retryWithBackoff(operation, maxRetries = 3) {
38    for (let attempt = 1; attempt <= maxRetries; attempt++) {
39      try {
40        return await operation();
41      } catch (error) {
42        if (attempt === maxRetries) {
43          throw error;
44        }
45        
46        // TODO: Exponential backoff with jitter
47        const baseDelay = Math.pow(2, attempt) * 1000; // 2s, 4s, 8s
48        const jitter = Math.random() * 1000; // 0-1s jitter
49        const delay = baseDelay + jitter;
50        
51        console.log(`⏳ Retry attempt ${attempt}/${maxRetries} in ${delay}ms`);
52        await new Promise(resolve => setTimeout(resolve, delay));
53      }
54    }
55  }
56  
57  // TODO: Implement health monitoring
58  startHealthMonitoring() {
59    setInterval(async () => {
60      for (const endpoint of this.endpoints) {
61        try {
62          const startTime = Date.now();
63          await this.healthCheck(endpoint);
64          const responseTime = Date.now() - startTime;
65          
66          this.healthStatus.set(endpoint, {
67            status: 'healthy',
68            responseTime,
69            lastCheck: Date.now()
70          });
71          
72        } catch (error) {
73          this.healthStatus.set(endpoint, {
74            status: 'unhealthy',
75            error: error.message,
76            lastCheck: Date.now()
77          });
78        }
79      }
80    }, 30000); // Check every 30 seconds
81  }
82  
83  async healthCheck(endpoint) {
84    // TODO: Implement health check
85    const timeout = new Promise((_, reject) => 
86      setTimeout(() => reject(new Error('Health check timeout')), 5000)
87    );
88    
89    const healthRequest = fetch(`${endpoint}/health`);
90    
91    return Promise.race([healthRequest, timeout]);
92  }
93  
94  // TODO: Get healthy endpoints for load balancing
95  getHealthyEndpoints() {
96    return this.endpoints.filter(endpoint => {
97      const health = this.healthStatus.get(endpoint);
98      return health?.status === 'healthy';
99    });
100  }
101}
102
103// TODO: Circuit Breaker Implementation  
104class CircuitBreaker {
105  constructor(endpoint, threshold = 5, timeout = 60000) {
106    this.endpoint = endpoint;
107    this.threshold = threshold;
108    this.timeout = timeout;
109    this.failureCount = 0;
110    this.lastFailureTime = null;
111    this.state = 'CLOSED'; // CLOSED, OPEN, HALF_OPEN
112  }
113  
114  isOpen() {
115    if (this.state === 'OPEN') {
116      // TODO: Check if timeout period has passed
117      if (Date.now() - this.lastFailureTime > this.timeout) {
118        this.state = 'HALF_OPEN';
119        return false;
120      }
121      return true;
122    }
123    return false;
124  }
125  
126  recordSuccess() {
127    this.failureCount = 0;
128    this.state = 'CLOSED';
129  }
130  
131  recordFailure() {
132    this.failureCount++;
133    this.lastFailureTime = Date.now();
134    
135    if (this.failureCount >= this.threshold) {
136      this.state = 'OPEN';
137      console.log(`🔴 Circuit breaker OPEN for ${this.endpoint}`);
138    }
139  }
140}