feat: add stock indicators route and Alpaca account info

- New /stocks route with StockViewer component
- New /api/indicators endpoint with SMA, EMA, RSI, MACD
- New /api/alpaca/account endpoint
- AlpacaAccountInfo component on home page
- Indicator calculation utilities
- Tests for utilities and components
- Vite proxy config for /api

app/utils/__tests__/indicators.test.ts

@@ -0,0 +1,54 @@
+import { describe, it, expect } from "vitest";
+import {
+  calculateSMA,
+  calculateEMA,
+  calculateRSI,
+  calculateMACD,
+} from "../../utils/indicators";
+
+describe("calculateSMA", () => {
+  it("returns 0 when prices length < period", () => {
+    expect(calculateSMA([1, 2], 5)).toBe(0);
+  });
+
+  it("calculates simple moving average correctly", () => {
+    expect(calculateSMA([1, 2, 3, 4, 5], 5)).toBe(3);
+  });
+});
+
+describe("calculateEMA", () => {
+  it("returns 0 when prices length < period", () => {
+    expect(calculateEMA([1, 2], 5)).toBe(0);
+  });
+
+  it("calculates exponential moving average", () => {
+    const prices = [10, 11, 12, 13, 14, 15];
+    const result = calculateEMA(prices, 3);
+    expect(result).toBeCloseTo(14.125, 2);
+  });
+});
+
+describe("calculateRSI", () => {
+  it("returns 0 when prices length < period + 1", () => {
+    expect(calculateRSI([1, 2, 3], 5)).toBe(0);
+  });
+
+  it("calculates relative strength index", () => {
+    const prices = [100, 102, 101, 105, 107, 110, 108, 115, 120, 119, 121];
+    const result = calculateRSI(prices, 5);
+    expect(result).toBeGreaterThan(50);
+    expect(result).toBeLessThan(100);
+  });
+});
+
+describe("calculateMACD", () => {
+  it("returns 0 when prices length < slowPeriod", () => {
+    expect(calculateMACD([1, 2, 3], 12, 26, 9)).toBe(0);
+  });
+
+  it("calculates MACD line", () => {
+    const prices = Array.from({ length: 30 }, (_, i) => 100 + i * 0.5);
+    const result = calculateMACD(prices);
+    expect(result).toBeCloseTo(-0.96, 2);
+  });
+});

app/utils/indicators.ts

@@ -0,0 +1,45 @@
+export function calculateSMA(prices: number[], period: number = 20): number {
+  if (prices.length < period) return 0;
+  const sum = prices.slice(0, period).reduce((a, b) => a + b, 0);
+  return sum / period;
+}
+
+export function calculateEMA(prices: number[], period: number = 20): number {
+  if (prices.length < period) return 0;
+  const multiplier = 2 / (period + 1);
+  let ema = prices[period - 1];
+  for (let i = period; i < prices.length; i++) {
+    ema = prices[i] * multiplier + ema * (1 - multiplier);
+  }
+  return ema;
+}
+
+export function calculateRSI(prices: number[], period: number = 14): number {
+  if (prices.length < period + 1) return 0;
+  let gains = 0;
+  let losses = 0;
+  for (let i = 1; i <= period; i++) {
+    const diff = prices[i] - prices[i - 1];
+    if (diff > 0) gains += diff;
+    else losses -= diff;
+  }
+  const avgGain = gains / period;
+  const avgLoss = losses / period;
+  if (avgLoss === 0) return 100;
+  const rs = avgGain / avgLoss;
+  return 100 - (100 / (1 + rs));
+}
+
+export function calculateMACD(
+  prices: number[],
+  fastPeriod: number = 12,
+  slowPeriod: number = 26,
+  signalPeriod: number = 9
+): number {
+  if (prices.length < slowPeriod) return 0;
+  const emaFast = calculateEMA(prices, fastPeriod);
+  const emaSlow = calculateEMA(prices, slowPeriod);
+  const macdLine = emaFast - emaSlow;
+  const signal = calculateEMA([macdLine], signalPeriod);
+  return macdLine - signal;
+}