Implement the http variant of the bank server.

During that process, many shortcomings with the socket server and the
bank lib were fixed.

I am aware a massive commit like this is not ideal.

bank/src/bank.rs

@@ -1,38 +1,61 @@
 use std::collections::{HashMap, HashSet};
-use std::sync::RwLock;
+use std::sync::{RwLock, RwLockReadGuard};
 
 #[cfg(test)]
 use anyhow::Result;
 
-use crate::account::Account;
+use crate::account::{Account, AccountError};
 
+#[derive(Default)]
 pub struct Bank {
     pub accounts: HashMap<String, RwLock<Account>>,
 }
 
 impl Bank {
     pub fn new() -> Self {
-        Self { accounts: HashMap::new() }
+        Default::default()
+    }
+
+    pub fn account_action<F: Fn(&mut Account) -> Result<f64, AccountError>>(
+        bank: RwLockReadGuard<'_, Bank>,
+        nr: &str,
+        action: F,
+    ) -> Result<f64, AccountError> {
+        match bank.accounts.get(nr) {
+            None => Err(AccountError::NotFound),
+            Some(account) => {
+                let mut account = account.write().unwrap();
+                action(&mut account)
+            }
+        }
     }
 
     pub fn account_numbers(&self) -> HashSet<String> {
-        self.accounts.iter()
+        self.accounts
+            .iter()
             .filter(|(_, acc)| acc.read().unwrap().is_active)
             .map(|(_, acc)| acc.read().unwrap().number.clone())
             .collect()
     }
 
     pub fn create_account(&mut self, owner: String) -> String {
-        let acc = Account { owner, ..Default::default() };
-        let number = acc.number.clone();
+        let acc = Account {
+            owner,
+            ..Default::default()
+        };
+        let nr = acc.number.clone();
 
         self.accounts.insert(acc.number.clone(), RwLock::new(acc));
 
-        number
+        nr
     }
 
-    #[cfg(test)]
-    pub fn transfer(&self, from: &mut Account, to: &mut Account, amount: f64) -> Result<()> {
+    pub fn transfer(
+        &self,
+        from: &mut Account,
+        to: &mut Account,
+        amount: f64,
+    ) -> Result<(), AccountError> {
         from.withdraw(amount)?;
         to.deposit(amount)?;
 
@@ -83,4 +106,4 @@ mod tests {
 
         assert_eq!(1, bank.account_numbers().len());
     }
-}
+}