Add tryfrom for Lookups

src/main.rs

@@ -85,21 +85,8 @@ fn main() -> Result<(), Box<dyn Error>> {
         } => {
             inputs = inp;
 
-            let output_plan = if let Some(plan) = plan {
-                Ok(ynab::Lookup::Name(plan))
-            } else if let Some(plan_id) = plan_id {
-                Ok(ynab::Lookup::Id(plan_id))
-            } else {
-                Err("no plan name or id".to_string())
-            }?;
-
-            let output_account = if let Some(account) = account {
-                Ok(ynab::Lookup::Name(account))
-            } else if let Some(account_id) = account_id {
-                Ok(ynab::Lookup::Id(account_id))
-            } else {
-                Err("no account name or id".to_string())
-            }?;
+            let output_plan = ynab::Lookup::try_from((plan, plan_id))?;
+            let output_account = ynab::Lookup::try_from((account, account_id))?;
 
             Output::Ynab {
                 token,

src/ynab.rs

@@ -138,6 +138,18 @@ pub enum Lookup {
     Id(String),
 }
 
+impl TryFrom<(Option<String>, Option<String>)> for Lookup {
+    type Error = String;
+
+    fn try_from((name, id): (Option<String>, Option<String>)) -> Result<Self, Self::Error> {
+        match (name, id) {
+            (Some(name), _) => Ok(Lookup::Name(name)),
+            (_, Some(id)) => Ok(Lookup::Id(id)),
+            _ => Err("must provide name or id".to_owned()),
+        }
+    }
+}
+
 pub struct Ynab {
     client: YnabClient,
     plan_id: String,