feat: added get uears (#123)

* feat: added get uears

* feat: changed a structure

* chore: format

crates/aws_clients/src/dynamodb/mod.rs

@@ -31,7 +31,7 @@ pub mod client {
 
     impl GetFileListTrait for DynamoDbClient {
         async fn get_years() -> Result<Vec<String>, String> {
-            Ok(vec![])
+            get_date_list("root").await
         }
 
         async fn get_month(_years: usize) -> Result<Vec<String>, String> {
@@ -110,6 +110,39 @@ pub mod client {
         }
     }
 
+    async fn get_date_list(key: &str) -> Result<Vec<String>, String> {
+        let request = dynamodb_client()
+            .await
+            .get_item()
+            .table_name(table_name())
+            .key("PK", AttributeValue::S(key.to_string()))
+            .key("SK", AttributeValue::N("0".to_string()));
+
+        let saved_date = match request.send().await {
+            Ok(result) => match result.item {
+                None => return Ok(Vec::new()),
+                Some(item) => match item.get_key_value("SavedDate") {
+                    None => return Err("Saved date is not found".to_string()),
+                    Some(val) => match val.1.as_l() {
+                        Ok(attribute) => attribute.to_owned(),
+                        Err(_) => return Err("Casting to list is failed.".to_string()),
+                    },
+                },
+            },
+            Err(e) => return Err(e.to_string()),
+        };
+
+        let mut date = Vec::new();
+
+        for attribute in saved_date {
+            match attribute.as_s() {
+                Ok(s) => date.push(s.to_owned()),
+                Err(_) => return Err("Invalid date is stored".to_string()),
+            }
+        }
+        Ok(date)
+    }
+
     /// this is a helper function.
     /// if there is argument, this function returns it.
     /// If not, this function gets system time.