Closes #ISSUE-009 - Implement DEV_MODE Offline-First Protection Shield

app/api/scanner/route.ts

@@ -347,6 +347,7 @@ export async function GET(request: Request) {
   const mode = searchParams.get('mode') || 'day_crash';
   const region = searchParams.get('region') || 'us';
   const fmpApiKey = process.env.FMP_API_KEY || 'U6lOXaOFPye7oc1D235kyAqJeQaiTAWc';
+  const isDevMode = process.env.DEV_MODE === 'true';
 
   let tickersPool: string[] = [];
 
@@ -358,38 +359,49 @@ export async function GET(request: Request) {
     // US region: Large/Mid pool + Small Cap pool
     tickersPool = [...US_MEGA_MID];
 
-    // Try to load FMP Small Caps or use static Small-Caps fallback list
-    let fmpSmallCaps: string[] = [];
-    try {
-      fmpSmallCaps = await fetchFmpScreener(fmpApiKey);
-    } catch (_) {}
-
-    if (fmpSmallCaps.length > 0) {
-      tickersPool.push(...fmpSmallCaps);
-    } else {
+    if (isDevMode) {
       tickersPool.push(...US_SMALL_CAPS);
+    } else {
+      // Try to load FMP Small Caps or use static Small-Caps fallback list
+      let fmpSmallCaps: string[] = [];
+      try {
+        fmpSmallCaps = await fetchFmpScreener(fmpApiKey);
+      } catch (_) {}
+
+      if (fmpSmallCaps.length > 0) {
+        tickersPool.push(...fmpSmallCaps);
+      } else {
+        tickersPool.push(...US_SMALL_CAPS);
+      }
     }
   }
 
   // De-duplicate tickers pool
   tickersPool = Array.from(new Set(tickersPool));
 
-  // Fetch chart details for all tickers in parallel
-  const rawCharts = await Promise.allSettled(
-    tickersPool.map(t => fetchYahooChart(t))
-  );
-
   const parsedResults: TickerDetails[] = [];
 
-  tickersPool.forEach((ticker, idx) => {
-    const res = rawCharts[idx];
-    if (res.status === 'fulfilled' && res.value) {
-      parsedResults.push(res.value);
-    } else {
-      // Fetch failed, use high-fidelity simulation
+  if (isDevMode) {
+    // Bypass Yahoo fetches completely, generate simulated charts directly!
+    tickersPool.forEach((ticker) => {
       parsedResults.push(generateSimulatedChart(ticker, mode));
-    }
-  });
+    });
+  } else {
+    // Fetch chart details for all tickers in parallel
+    const rawCharts = await Promise.allSettled(
+      tickersPool.map(t => fetchYahooChart(t))
+    );
+
+    tickersPool.forEach((ticker, idx) => {
+      const res = rawCharts[idx];
+      if (res.status === 'fulfilled' && res.value) {
+        parsedResults.push(res.value);
+      } else {
+        // Fetch failed, use high-fidelity simulation
+        parsedResults.push(generateSimulatedChart(ticker, mode));
+      }
+    });
+  }
 
   // Fetch fundamentals for top 15 candidates to reduce payload weight
   // Sort candidates first based on mode to isolate top 15
@@ -409,19 +421,26 @@ export async function GET(request: Request) {
   // Overlay fundamentals
   const finalResults = await Promise.all(
     sortedCandidates.map(async (item) => {
-      const fund = top15Symbols.has(item.ticker)
-        ? await fetchFMPFundamentalData(item.ticker, fmpApiKey)
-        : getMockFundamentals(item.ticker);
+      const useMock = isDevMode || !top15Symbols.has(item.ticker);
+      const fund = useMock
+        ? getMockFundamentals(item.ticker)
+        : await fetchFMPFundamentalData(item.ticker, fmpApiKey);
       
       return {
         ...item,
         ...fund,
-        dividendYield: fund.dividendYield ? Number((fund.dividendYield * (top15Symbols.has(item.ticker) ? 1 : 100)).toFixed(2)) : 0
+        dividendYield: fund.dividendYield ? Number((fund.dividendYield * (useMock ? 100 : 1)).toFixed(2)) : 0
       };
     })
   );
 
-  const response = NextResponse.json({ results: finalResults });
+  const response = NextResponse.json({ 
+    results: finalResults,
+    isShieldActive: isDevMode
+  });
   response.headers.set('Cache-Control', 'no-store, max-age=0, must-revalidate');
+  if (isDevMode) {
+    response.headers.set('X-Shield-Active', 'true');
+  }
   return response;
 }