Fix cache bug

Fix bug where a potentially incorrect resolution would be assumed.

src/cache/cache_line.rs

@@ -0,0 +1,30 @@
+use chrono::serde::ts_seconds;
+use chrono::{DateTime, Local, Utc};
+use serde::{Deserialize, Serialize};
+
+use crate::models::ExchangeRateResult;
+
+#[derive(Serialize, Deserialize, Debug)]
+pub struct CacheLine {
+    #[serde(with = "ts_seconds")]
+    date: DateTime<Utc>,
+
+    #[serde(rename = "camelCase")]
+    pub exchange_rate_results: Vec<ExchangeRateResult>,
+}
+
+impl CacheLine {
+    pub fn validate(&self) -> bool {
+        let today = Local::now().naive_local().date();
+        let saved = self.date.naive_local().date();
+        saved == today
+    }
+
+    pub fn new(exchange_rate_results: Vec<ExchangeRateResult>) -> Self {
+        let date = Local::now().to_utc();
+        Self {
+            exchange_rate_results,
+            date,
+        }
+    }
+}