added function aggregating multiple ticker data

src/corporate/fx.rs

@@ -0,0 +1,51 @@
+// src/corporate/fx.rs
+use std::collections::HashMap;
+use reqwest;
+use serde_json::Value;
+use tokio::fs;
+use std::path::Path;
+
+static FX_CACHE_PATH: &str = "fx_rates.json";
+
+pub async fn get_usd_rate(currency: &str) -> anyhow::Result<f64> {
+    if currency == "USD" {
+        return Ok(1.0);
+    }
+
+    let mut cache: HashMap<String, (f64, String)> = if Path::new(FX_CACHE_PATH).exists() {
+        let content = fs::read_to_string(FX_CACHE_PATH).await?;
+        serde_json::from_str(&content).unwrap_or_default()
+    } else {
+        HashMap::new()
+    };
+
+    let today = chrono::Local::now().format("%Y-%m-%d").to_string();
+    if let Some((rate, date)) = cache.get(currency) {
+        if date == &today {
+            return Ok(*rate);
+        }
+    }
+
+    let symbol = format!("{}USD=X", currency);
+    let url = format!("https://query1.finance.yahoo.com/v8/finance/chart/{}?range=1d&interval=1d", symbol);
+
+    let json: Value = reqwest::Client::new()
+        .get(&url)
+        .header("User-Agent", "Mozilla/5.0")
+        .send()
+        .await?
+        .json()
+        .await?;
+
+    let close = json["chart"]["result"][0]["meta"]["regularMarketPrice"]
+        .as_f64()
+        .or_else(|| json["chart"]["result"][0]["indicators"]["quote"][0]["close"][0].as_f64())
+        .unwrap_or(1.0);
+
+    let rate = if currency == "JPY" || currency == "KRW" { close } else { 1.0 / close }; // inverse pairs
+
+    cache.insert(currency.to_string(), (rate, today.clone()));
+    let _ = fs::write(FX_CACHE_PATH, serde_json::to_string_pretty(&cache)?).await;
+
+    Ok(rate)
+}