input.csv

@@ -1,6 +1,7 @@
 type,client,tx,amount
 deposit,1,1,1.0
 deposit,2,2,2.0
-deposit,1,3,2.0
+deposit,1,3,2.742
 withdrawal,1,4,1.5
 withdrawal,2,5,3.0
+dispute,2,2,

input2.csv

@@ -0,0 +1,8 @@
+type,client,tx,amount
+deposit,1,1,1.0
+deposit,2,2,2.0
+deposit,1,3,2.742
+withdrawal,1,4,1.5
+withdrawal,2,5,3.0
+dispute,2,2,
+resolve,2,2,

input3.csv

@@ -0,0 +1,8 @@
+type,client,tx,amount
+deposit,1,1,1.0
+deposit,2,2,2.0
+deposit,1,3,2.742
+withdrawal,1,4,1.5
+withdrawal,2,5,3.0
+dispute,2,2,
+chargeback,2,2,

src/bin/act.rs

@@ -1,29 +1,43 @@
-use clap::{App, Arg};
+use act::parse::parse;
-use std::io::{BufReader, BufRead, stdin};
+use act::process::process;
-use std::fs;
-use act::parse;
-use act::stores::ActStore;
 use act::stores::MemActStore;
+use act::types::Transaction;
+use clap::{App, Arg};
+use std::collections::HashMap;
+use std::fs;
+use std::io::{stdin, BufRead, BufReader};
 use tokio_stream::StreamExt;
 
 #[tokio::main]
 async fn main() {
     let matches = App::new("act")
         .version("0.1")
-        .about("Merges transactions into account state")
+        .about("Merges transactions into final account state")
         .author("Lewis Diamond")
-        .arg(Arg::with_name("input").required(false).index(1).help("Input file, stdin if omitted or -"))
+        .arg(
+            Arg::with_name("input")
+                .required(false)
+                .index(1)
+                .help("Input file, stdin if omitted or -"),
+        )
         .get_matches();
 
     let input: Box<dyn BufRead> = match matches.value_of("input") {
-        Some("-")|Some("")|None => Box::new(BufReader::new(stdin())),
+        Some("-") | Some("") | None => Box::new(BufReader::new(stdin())),
         Some(f) => Box::new(BufReader::new(fs::File::open(f).unwrap())),
     };
 
-
+    let mut act_store = MemActStore::new();
+    let mut tx_store: HashMap<u32, Transaction> = HashMap::new();
     let s = parse(input);
     tokio::pin!(s);
     while let Some(v) = s.next().await {
-        println!("{:?}", v);
+        process(v, &mut act_store, &mut tx_store);
+    }
+
+    let mut writer = csv::WriterBuilder::new().from_writer(std::io::stdout());
+
+    for act in act_store.into_iter() {
+        writer.serialize(act.1).unwrap();
     }
 }

src/lib.rs

@@ -1,125 +1,4 @@
-pub mod types;
+pub mod parse;
+pub mod process;
 pub mod stores;
-use async_stream::stream;
+pub mod types;
-use std::io::Read;
-use tokio_stream::Stream;
-use types::Transaction;
-
-pub fn parse<R: Read>(input: R) -> impl Stream<Item = Transaction> {
-    let mut reader = csv::ReaderBuilder::new()
-        .trim(csv::Trim::All)
-        .has_headers(true)
-        .from_reader(input);
-
-    stream! {
-        for tx in reader.deserialize() {
-            match tx {
-                Ok(tx) => yield tx,
-                //Depending on the infrastructure, a specific output format
-                //might be used to add monitoring/alerting
-                Err(e) => eprintln!("Error reading CSV: {}", e),
-            }
-        }
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use tokio_stream::StreamExt;
-    use tokio_test::block_on;
-    use types::Transaction;
-    use types::TransactionType;
-
-    #[test]
-    fn valid_csv_is_parsed() {
-        block_on(async {
-            let data = "\
-type,client,tx,amount
-deposit,1,1,1.0
-deposit,2,2,2.0
-deposit,1,3,2.0
-withdrawal,1,4,1.5
-withdrawal,2,5,3.0";
-
-            let expected = vec![
-            Transaction {tx_type: TransactionType::Deposit, amount: 10000, client: 1, tx: 1},
-            Transaction {tx_type: TransactionType::Deposit, amount: 20000, client: 2, tx: 2},
-            Transaction {tx_type: TransactionType::Deposit, amount: 20000, client: 1, tx: 3},
-            Transaction {tx_type: TransactionType::Withdrawal, amount: 15000, client: 1, tx: 4},
-            Transaction {tx_type: TransactionType::Withdrawal, amount: 30000, client: 2, tx: 5},
-            ];
-            let txs = parse(data.as_bytes()).collect::<Vec<Transaction>>().await;
-            assert_eq!(expected, txs);
-        });
-    }
-
-    #[test]
-    fn valid_csv_with_whitespaces_is_parsed() {
-        block_on(async {
-            let data = "\
-type,       client,  tx, amount
-deposit,         1,   1,    1.0
-deposit,         2,   2,    2.0
-deposit,         1,   3,    2.0
-withdrawal,      1,   4,    1.5
-withdrawal,      2,   5,    3.0";
-
-            let expected = vec![
-            Transaction {tx_type: TransactionType::Deposit, amount: 10000, client: 1, tx: 1},
-            Transaction {tx_type: TransactionType::Deposit, amount: 20000, client: 2, tx: 2},
-            Transaction {tx_type: TransactionType::Deposit, amount: 20000, client: 1, tx: 3},
-            Transaction {tx_type: TransactionType::Withdrawal, amount: 15000, client: 1, tx: 4},
-            Transaction {tx_type: TransactionType::Withdrawal, amount: 30000, client: 2, tx: 5},
-            ];
-            let txs = parse(data.as_bytes()).collect::<Vec<Transaction>>().await;
-            assert_eq!(expected, txs);
-        });
-    }
-
-    #[test]
-    fn amounts_are_parsed_correctly() {
-        block_on(async {
-            let data = "\
-type,client,tx,amount
-deposit,1,1,1.0001
-deposit,2,2,2.0010
-deposit,1,3,10.01
-withdrawal,1,4,01.10
-withdrawal,2,5,10.0110101";
-
-            let expected = vec![
-            Transaction {tx_type: TransactionType::Deposit, amount: 10001, client: 1, tx: 1},
-            Transaction {tx_type: TransactionType::Deposit, amount: 20010, client: 2, tx: 2},
-            Transaction {tx_type: TransactionType::Deposit, amount: 100100, client: 1, tx: 3},
-            Transaction {tx_type: TransactionType::Withdrawal, amount: 11000, client: 1, tx: 4},
-            Transaction {tx_type: TransactionType::Withdrawal, amount: 100110, client: 2, tx: 5},
-            ];
-            let txs = parse(data.as_bytes()).collect::<Vec<Transaction>>().await;
-            assert_eq!(expected, txs);
-        });
-    }
-
-    #[test]
-    fn invalid_amounts_are_filtered() {
-        block_on(async {
-            let data = "\
-type,client,tx,amount
-deposit,1,1,99999999999999999
-deposit,2,2,18446744073709551615
-deposit,1,3,18446744073709551616
-withdrawal,1,4,0
-withdrawal,2,5,-1
-withdrawal,1,6,-99999999999999999
-withdrawal,1,6,-18446744073709551615
-withdrawal,1,7,-18446744073709551616";
-
-            let expected = vec![
-            Transaction {tx_type: TransactionType::Withdrawal, amount: 0, client: 1, tx: 4},
-            ];
-            let txs = parse(data.as_bytes()).collect::<Vec<Transaction>>().await;
-
-            assert_eq!(expected, txs);
-        });
-    }
-}

src/parse.rs

@@ -0,0 +1,240 @@
+use crate::types::Transaction;
+use async_stream::stream;
+use std::io::Read;
+use tokio_stream::Stream;
+
+pub fn parse<R: Read>(input: R) -> impl Stream<Item = Transaction> {
+    let mut reader = csv::ReaderBuilder::new()
+        .trim(csv::Trim::All)
+        .flexible(true)
+        .has_headers(true)
+        .from_reader(input);
+
+    stream! {
+        for tx in reader.deserialize() {
+            match tx {
+                Ok(tx) => yield tx,
+                //Depending on the infrastructure, a specific output format
+                //might be used to add monitoring/alerting
+                Err(e) => eprintln!("Error reading CSV: {}", e),
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::types::Transaction;
+    use crate::types::TransactionType;
+    use tokio_stream::StreamExt;
+    use tokio_test::block_on;
+
+    #[test]
+    fn valid_csv_is_parsed() {
+        block_on(async {
+            let data = "\
+type,client,tx,amount
+deposit,1,1,1.0
+deposit,2,2,2.0
+deposit,1,3,2.0
+withdrawal,1,4,1.5
+withdrawal,2,5,3.0";
+
+            let expected = vec![
+                Transaction {
+                    tx_type: TransactionType::Deposit,
+                    amount: 10000,
+                    client: 1,
+                    tx: 1,
+                },
+                Transaction {
+                    tx_type: TransactionType::Deposit,
+                    amount: 20000,
+                    client: 2,
+                    tx: 2,
+                },
+                Transaction {
+                    tx_type: TransactionType::Deposit,
+                    amount: 20000,
+                    client: 1,
+                    tx: 3,
+                },
+                Transaction {
+                    tx_type: TransactionType::Withdrawal,
+                    amount: 15000,
+                    client: 1,
+                    tx: 4,
+                },
+                Transaction {
+                    tx_type: TransactionType::Withdrawal,
+                    amount: 30000,
+                    client: 2,
+                    tx: 5,
+                },
+            ];
+            let txs = parse(data.as_bytes()).collect::<Vec<Transaction>>().await;
+            assert_eq!(expected, txs);
+        });
+    }
+
+    #[test]
+    fn valid_csv_with_whitespaces_is_parsed() {
+        block_on(async {
+            let data = "\
+type,       client,  tx, amount
+deposit,         1,   1,    1.0
+deposit,         2,   2,    2.0
+deposit,         1,   3,    2.0
+withdrawal,      1,   4,    1.5
+withdrawal,      2,   5,    3.0";
+
+            let expected = vec![
+                Transaction {
+                    tx_type: TransactionType::Deposit,
+                    amount: 10000,
+                    client: 1,
+                    tx: 1,
+                },
+                Transaction {
+                    tx_type: TransactionType::Deposit,
+                    amount: 20000,
+                    client: 2,
+                    tx: 2,
+                },
+                Transaction {
+                    tx_type: TransactionType::Deposit,
+                    amount: 20000,
+                    client: 1,
+                    tx: 3,
+                },
+                Transaction {
+                    tx_type: TransactionType::Withdrawal,
+                    amount: 15000,
+                    client: 1,
+                    tx: 4,
+                },
+                Transaction {
+                    tx_type: TransactionType::Withdrawal,
+                    amount: 30000,
+                    client: 2,
+                    tx: 5,
+                },
+            ];
+            let txs = parse(data.as_bytes()).collect::<Vec<Transaction>>().await;
+            assert_eq!(expected, txs);
+        });
+    }
+
+    #[test]
+    fn amounts_are_parsed_correctly() {
+        block_on(async {
+            let data = "\
+type,client,tx,amount
+deposit,1,1,1.0001
+deposit,2,2,2.0010
+deposit,1,3,10.01
+withdrawal,1,4,01.10
+withdrawal,2,5,10.0110101";
+
+            let expected = vec![
+                Transaction {
+                    tx_type: TransactionType::Deposit,
+                    amount: 10001,
+                    client: 1,
+                    tx: 1,
+                },
+                Transaction {
+                    tx_type: TransactionType::Deposit,
+                    amount: 20010,
+                    client: 2,
+                    tx: 2,
+                },
+                Transaction {
+                    tx_type: TransactionType::Deposit,
+                    amount: 100100,
+                    client: 1,
+                    tx: 3,
+                },
+                Transaction {
+                    tx_type: TransactionType::Withdrawal,
+                    amount: 11000,
+                    client: 1,
+                    tx: 4,
+                },
+                Transaction {
+                    tx_type: TransactionType::Withdrawal,
+                    amount: 100110,
+                    client: 2,
+                    tx: 5,
+                },
+            ];
+            let txs = parse(data.as_bytes()).collect::<Vec<Transaction>>().await;
+            assert_eq!(expected, txs);
+        });
+    }
+
+    #[test]
+    fn invalid_amounts_are_filtered() {
+        block_on(async {
+            let data = "\
+type,client,tx,amount
+deposit,1,1,99999999999999999
+deposit,2,2,18446744073709551615
+deposit,1,3,18446744073709551616
+withdrawal,1,4,0
+withdrawal,1,4,
+withdrawal,1,4,a
+withdrawal,2,5,-1
+withdrawal,1,6,-99999999999999999
+withdrawal,1,6,-18446744073709551615
+withdrawal,1,7,-18446744073709551616";
+
+            let expected = vec![
+                Transaction {
+                    tx_type: TransactionType::Withdrawal,
+                    amount: 0,
+                    client: 1,
+                    tx: 4,
+                },
+                Transaction {
+                    tx_type: TransactionType::Withdrawal,
+                    amount: 0,
+                    client: 1,
+                    tx: 4,
+                },
+            ];
+            let txs = parse(data.as_bytes()).collect::<Vec<Transaction>>().await;
+
+            assert_eq!(expected, txs);
+        });
+    }
+
+    #[test]
+    fn disputes_are_parsed_correctly() {
+        block_on(async {
+            let data = "\
+type,client,tx,amount
+dispute,1,1,
+dispute,1,2,";
+
+            let expected = vec![
+                Transaction {
+                    tx_type: TransactionType::Dispute,
+                    amount: 0,
+                    client: 1,
+                    tx: 1,
+                },
+                Transaction {
+                    tx_type: TransactionType::Dispute,
+                    amount: 0,
+                    client: 1,
+                    tx: 2,
+                },
+            ];
+            let txs = parse(data.as_bytes()).collect::<Vec<Transaction>>().await;
+
+            assert_eq!(expected, txs);
+        });
+    }
+}

src/process.rs

@@ -0,0 +1,150 @@
+use crate::{
+    stores::ActStore,
+    types::{Transaction, TransactionType},
+};
+use std::collections::HashMap;
+
+pub fn process(
+    t: Transaction,
+    act_store: &mut dyn ActStore,
+    tx_store: &mut HashMap<u32, Transaction>,
+) {
+    match t.tx_type {
+        TransactionType::Deposit => {
+            act_store.deposit(t.client, t.amount);
+            tx_store.insert(t.tx, t);
+        }
+        TransactionType::Withdrawal => {
+            act_store.withdraw(t.client, t.amount);
+        }
+        TransactionType::Dispute => {
+            if let Some(orig) = tx_store.get(&t.tx) {
+                act_store.hold(t.client, orig.amount);
+            }
+        }
+        TransactionType::Resolve => {
+            if let Some(orig) = tx_store.get(&t.tx) {
+                act_store.unhold(t.client, orig.amount);
+            }
+        }
+        TransactionType::Chargeback => {
+            if let Some(orig) = tx_store.get(&t.tx) {
+                act_store.unhold(t.client, orig.amount);
+                act_store.withdraw(t.client, orig.amount);
+                act_store.lock_account(t.client);
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::stores::MemActStore;
+    use crate::types::Transaction;
+    use crate::types::TransactionType;
+
+    #[test]
+    fn valid_tx_and_over_limit_withdraw() {
+        let mut act_store: Box<dyn ActStore> = Box::new(MemActStore::new());
+        let mut tx_store: HashMap<u32, Transaction> = HashMap::new();
+        let txs = vec![
+            Transaction {
+                tx_type: TransactionType::Deposit,
+                amount: 10000,
+                client: 1,
+                tx: 1,
+            },
+            Transaction {
+                tx_type: TransactionType::Deposit,
+                amount: 20000,
+                client: 2,
+                tx: 2,
+            },
+            Transaction {
+                tx_type: TransactionType::Deposit,
+                amount: 20000,
+                client: 1,
+                tx: 3,
+            },
+            Transaction {
+                tx_type: TransactionType::Withdrawal,
+                amount: 15000,
+                client: 1,
+                tx: 4,
+            },
+            Transaction {
+                tx_type: TransactionType::Withdrawal,
+                amount: 30000,
+                client: 2,
+                tx: 5,
+            },
+        ];
+        for tx in txs {
+            process(tx, act_store.as_mut(), &mut tx_store);
+        }
+
+        let act = act_store.get_account(1).unwrap();
+        assert_eq!(0, act.held());
+        assert_eq!(15000, act.available());
+
+        let act = act_store.get_account(2).unwrap();
+        assert_eq!(0, act.held());
+        assert_eq!(20000, act.available());
+    }
+
+    #[test]
+    fn held_funds() {
+        let mut act_store: Box<dyn ActStore> = Box::new(MemActStore::new());
+        let mut tx_store: HashMap<u32, Transaction> = HashMap::new();
+        process(
+            Transaction {
+                tx_type: TransactionType::Deposit,
+                amount: 10000,
+                client: 1,
+                tx: 1,
+            },
+            act_store.as_mut(),
+            &mut tx_store,
+        );
+        process(
+            Transaction {
+                tx_type: TransactionType::Dispute,
+                amount: 0,
+                client: 1,
+                tx: 1,
+            },
+            act_store.as_mut(),
+            &mut tx_store,
+        );
+        let act = act_store.get_account(1).unwrap();
+        assert_eq!(10000, act.held());
+        assert_eq!(0, act.available());
+        process(
+            Transaction {
+                tx_type: TransactionType::Withdrawal,
+                amount: 10000,
+                client: 1,
+                tx: 2,
+            },
+            act_store.as_mut(),
+            &mut tx_store,
+        );
+        let act = act_store.get_account(1).unwrap();
+        assert_eq!(10000, act.held());
+        assert_eq!(0, act.available());
+        process(
+            Transaction {
+                tx_type: TransactionType::Resolve,
+                amount: 0,
+                client: 1,
+                tx: 1,
+            },
+            act_store.as_mut(),
+            &mut tx_store,
+        );
+        let act = act_store.get_account(1).unwrap();
+        assert_eq!(0, act.held());
+        assert_eq!(10000, act.available());
+    }
+}

src/stores/mem.rs

@@ -1,51 +1,84 @@
 use super::ActStore;
 use crate::types::Account;
+use std::collections::hash_map::IntoIter;
 use std::collections::HashMap;
 
 pub struct MemActStore(HashMap<u16, Account>);
 
+enum Action {
+    Withdraw(u64),
+    Deposit(u64),
+    Hold(u64),
+    Unhold(u64),
+}
+
 impl MemActStore {
-    pub fn new() -> MemActStore {
+    pub fn new() -> Self {
         MemActStore(HashMap::new())
     }
 
-    fn add_or_sub_balance(&mut self, client: &u16, amnt: isize, sub: bool) -> isize {
+    fn action_act(&mut self, client: u16, action: Action) -> u64 {
-        let act = self
+        let act = self.0.entry(client).or_insert_with(|| Account::new(client));
-            .0
+        match action {
-            .entry(*client)
+            Action::Withdraw(amnt) => act.withdraw(amnt),
-            .or_insert_with(|| Account::new(*client));
+            Action::Deposit(amnt) => act.deposit(amnt),
-        if sub {
+            Action::Hold(amnt) => act.hold(amnt),
-            act.balance -= amnt
+            Action::Unhold(amnt) => act.unhold(amnt),
-        } else {
+        }
-            act.balance += amnt
+    }
-        };
+}
-        act.balance
+
+impl Default for MemActStore {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl IntoIterator for MemActStore {
+    type Item = (u16, Account);
+
+    type IntoIter = IntoIter<u16, Account>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.0.into_iter()
     }
 }
 
 impl ActStore for MemActStore {
-    fn add_to_balance(&mut self, client: &u16, amnt: isize) -> isize {
+    fn deposit(&mut self, client: u16, amnt: u64) -> u64 {
-        self.add_or_sub_balance(client, amnt, false)
+        self.action_act(client, Action::Deposit(amnt))
     }
 
-    fn sub_from_balance(&mut self, client: &u16, amnt: isize) -> isize {
+    fn withdraw(&mut self, client: u16, amnt: u64) -> u64 {
-        self.add_or_sub_balance(client, amnt, true)
+        self.action_act(client, Action::Withdraw(amnt))
     }
 
-    fn hold_amount(&mut self, client: u16, amnt: isize) {
+    fn hold(&mut self, client: u16, amnt: u64) -> u64 {
-        todo!()
+        self.action_act(client, Action::Hold(amnt))
     }
 
-    fn lock_account(&mut self, client: u16) {
+    fn unhold(&mut self, client: u16, amnt: u64) -> u64 {
-        todo!()
+        self.action_act(client, Action::Unhold(amnt))
     }
 
-    fn unlock_account(&mut self, client: u16) {
+    fn lock_account(&mut self, client: u16) -> bool {
-        todo!()
+        if let Some(act) = self.0.get_mut(&client) {
+            act.lock()
+        } else {
+            false
+        }
     }
 
-    fn get_account(&self, client: &u16) -> Option<&Account> {
+    fn unlock_account(&mut self, client: u16) -> bool {
-        self.0.get(client)
+        if let Some(act) = self.0.get_mut(&client) {
+            act.unlock()
+        } else {
+            false
+        }
+    }
+
+    fn get_account(&self, client: u16) -> Option<&Account> {
+        self.0.get(&client)
     }
 }
 
@@ -57,18 +90,18 @@ mod tests {
     fn test_add_balance() {
         let mut store = MemActStore::new();
         let client_id = 200;
-        store.add_to_balance(&client_id, 200);
+        store.deposit(client_id, 200);
 
-        if let Some(act) = store.get_account(&client_id) {
+        if let Some(act) = store.get_account(client_id) {
-            assert_eq!(200, act.id);
+            assert_eq!(200, act.id());
-            assert_eq!(200, act.balance);
+            assert_eq!(200, act.available());
         } else {
             panic!("Could not get account from store");
         }
-        let balance = store.add_to_balance(&client_id, 50);
+        let balance = store.deposit(client_id, 50);
-        if let Some(act) = store.get_account(&client_id) {
+        if let Some(act) = store.get_account(client_id) {
-            assert_eq!(200, act.id);
+            assert_eq!(200, act.id());
-            assert_eq!(250, act.balance);
+            assert_eq!(250, act.available());
             assert_eq!(250, balance);
         } else {
             panic!("Could not get account from store");
@@ -79,18 +112,18 @@ mod tests {
     fn test_sub_balance() {
         let mut store = MemActStore::new();
         let client_id = 1;
-        store.add_to_balance(&client_id, 200);
+        store.deposit(client_id, 200);
 
-        if let Some(act) = store.get_account(&client_id) {
+        if let Some(act) = store.get_account(client_id) {
-            assert_eq!(1, act.id);
+            assert_eq!(1, act.id());
-            assert_eq!(200, act.balance);
+            assert_eq!(200, act.available());
         } else {
             panic!("Could not get account from store");
         }
-        let balance = store.sub_from_balance(&client_id, 50);
+        let balance = store.withdraw(client_id, 50);
-        if let Some(act) = store.get_account(&client_id) {
+        if let Some(act) = store.get_account(client_id) {
-            assert_eq!(1, act.id);
+            assert_eq!(1, act.id());
-            assert_eq!(150, act.balance);
+            assert_eq!(150, act.available());
             assert_eq!(150, balance);
         } else {
             panic!("Could not get account from store");
@@ -98,22 +131,50 @@ mod tests {
     }
 
     #[test]
-    fn test_lock_negative_balance() {
+    fn test_negative_balance() {
         let mut store = MemActStore::new();
         let client_id = 1;
-        store.sub_from_balance(&client_id, 1);
+        store.withdraw(client_id, 1);
 
-        if let Some(act) = store.get_account(&client_id) {
+        if let Some(act) = store.get_account(client_id) {
-            assert_eq!(1, act.id);
+            assert_eq!(1, act.id());
-            assert_eq!(-1, act.balance);
+            assert_eq!(0, act.available());
         } else {
             panic!("Could not get account from store");
         }
-        let balance = store.sub_from_balance(&client_id, 50);
+    }
-        if let Some(act) = store.get_account(&client_id) {
+
-            assert_eq!(1, act.id);
+    #[test]
-            assert_eq!(150, act.balance);
+    fn test_hold() {
-            assert_eq!(150, balance);
+        let mut store = MemActStore::new();
+        let client_id = 1;
+        store.deposit(client_id, 100);
+
+        let avail = store.hold(client_id, 10);
+        assert_eq!(90, avail);
+
+        if let Some(act) = store.get_account(client_id) {
+            assert_eq!(1, act.id());
+            assert_eq!(90, act.available());
+        } else {
+            panic!("Could not get account from store");
+        }
+
+        assert_eq!(0, store.hold(client_id, 100));
+        assert_eq!(10, store.unhold(client_id, 20));
+    }
+
+    #[test]
+    fn test_lock() {
+        let mut store = MemActStore::new();
+        let client_id = 1;
+        store.deposit(client_id, 100);
+        let locked = store.lock_account(client_id);
+        assert!(locked);
+
+        if let Some(act) = store.get_account(client_id) {
+            assert_eq!(1, act.id());
+            assert!(act.is_locked());
         } else {
             panic!("Could not get account from store");
         }

src/stores/mod.rs

@@ -4,12 +4,11 @@ pub use mem::MemActStore;
 use crate::types::Account;
 
 pub trait ActStore {
-
+    fn get_account(&self, client: u16) -> Option<&Account>;
-    fn get_account(&self, client: &u16) -> Option<&Account>;
+    fn deposit(&mut self, client: u16, amnt: u64) -> u64;
-    fn add_to_balance(&mut self, client: &u16, amnt: isize) -> isize;
+    fn withdraw(&mut self, client: u16, amnt: u64) -> u64;
-    fn sub_from_balance(&mut self, client: &u16, amnt: isize) -> isize;
+    fn hold(&mut self, client: u16, amnt: u64) -> u64;
-    fn hold_amount(&mut self, client:u16, amnt: isize);
+    fn unhold(&mut self, client: u16, amnt: u64) -> u64;
-    fn lock_account(&mut self, client: u16);
+    fn lock_account(&mut self, client: u16) -> bool;
-    fn unlock_account(&mut self, client: u16);
+    fn unlock_account(&mut self, client: u16) -> bool;
-    
 }

src/types/account.rs

@@ -1,29 +1,113 @@
-use serde::Serialize;
+use serde::{Serialize, Serializer};
+const PRECISION: u32 = 4;
 
-#[derive(Debug, Serialize, PartialEq)]
+#[derive(Debug, PartialEq)]
 pub struct Account {
-    pub id: u16,
+    id: u16,
-    pub balance: isize,
+    total: u64,
-    pub held: usize,
+    held: u64,
-    pub locked: bool,
+    locked: bool,
 }
 
 impl Account {
     pub fn new(client_id: u16) -> Account {
         Account {
             id: client_id,
-            balance: 0,
+            total: 0,
             held: 0,
             locked: false,
         }
     }
 
-    pub fn with_balance(client_id: u16, seed_balance: isize) -> Account {
+    pub fn with_balance(client_id: u16, seed_balance: u64) -> Account {
         Account {
             id: client_id,
-            balance: seed_balance,
+            total: seed_balance,
             held: 0,
             locked: false,
         }
     }
+
+    pub fn id(&self) -> u16 {
+        self.id
+    }
+    pub fn available(&self) -> u64 {
+        self.total.saturating_sub(self.held)
+    }
+    pub fn held(&self) -> u64 {
+        self.held
+    }
+    pub fn hold(&mut self, amnt: u64) -> u64 {
+        if let Some(new_held) = self.held.checked_add(amnt) {
+            self.held = new_held;
+        }
+        self.available()
+    }
+
+    pub fn unhold(&mut self, amnt: u64) -> u64 {
+        if let Some(new_held) = self.held.checked_sub(amnt) {
+            self.held = new_held;
+        }
+        self.available()
+    }
+    pub fn deposit(&mut self, amnt: u64) -> u64 {
+        if let Some(new_bal) = self.total.checked_add(amnt) {
+            self.total = new_bal;
+        };
+        self.available()
+    }
+    pub fn withdraw(&mut self, amnt: u64) -> u64 {
+        if self.available().checked_sub(amnt).is_some() {
+            self.total -= amnt;
+        };
+        self.available()
+    }
+
+    pub fn lock(&mut self) -> bool {
+        self.locked = true;
+        self.locked
+    }
+
+    pub fn unlock(&mut self) -> bool {
+        self.locked = false;
+        self.locked
+    }
+
+    pub fn is_locked(&self) -> bool {
+        self.locked
+    }
+}
+
+#[derive(Debug, Serialize, PartialEq)]
+pub struct AccountSer {
+    id: u16,
+    total: String,
+    held: String,
+    available: String,
+    locked: bool,
+}
+
+impl serde::Serialize for Account {
+    fn serialize<S>(&self, s: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let total = format!(
+            "{0:.4}",
+            (self.total as f64) / (10u64.pow(PRECISION) as f64)
+        );
+        let held = format!("{0:.4}", (self.held as f64) / (10u64.pow(PRECISION) as f64));
+        let available = format!(
+            "{0:.4}",
+            (self.available() as f64) / (10u64.pow(PRECISION) as f64)
+        );
+        let ser = AccountSer {
+            id: self.id,
+            total,
+            held,
+            available,
+            locked: self.locked,
+        };
+        ser.serialize(s)
+    }
 }

src/types/transaction.rs

@@ -7,6 +7,9 @@ const PRECISION: u32 = 4;
 pub enum TransactionType {
     Deposit,
     Withdrawal,
+    Dispute,
+    Resolve,
+    Chargeback,
 }
 
 #[derive(Debug, Deserialize, PartialEq)]
@@ -14,33 +17,33 @@ pub struct Transaction {
     #[serde(rename = "type")]
     pub tx_type: TransactionType,
     pub client: u16,
-    pub tx: usize,
+    pub tx: u32,
     /// Amount of the smallest unit, e.g. 0.0001 as per the specification
     #[serde(deserialize_with = "de_amount")]
-    pub amount: usize,
+    pub amount: u64,
 }
 
-fn de_amount<'de, D>(deserializer: D) -> Result<usize, D::Error>
+fn de_amount<'de, D>(deserializer: D) -> Result<u64, D::Error>
 where
     D: Deserializer<'de>,
 {
-    //TODO validate for input such as `.100` so it doesn't give 100
+    //TODO use something like num_bigint instead
     let deserialized = String::deserialize(deserializer)?;
     let mut splitted = deserialized.split('.');
     let units = splitted
         .next()
-        .map_or(Ok(0usize), |v| v.parse::<usize>())
+        .map_or(Ok(0), |v| match v {
+            "" => Ok(0),
+            _ => v.parse::<u64>(),
+        })
         .map_err(de::Error::custom)?
-        .checked_mul(10usize.pow(PRECISION))
+        .checked_mul(10u64.pow(PRECISION))
         .ok_or_else(|| de::Error::custom("Value too large"))?;
-    //TODO improve this to avoid `format!`
+    //TODO format! here isn't great!
     let dec = splitted
         .next()
-        .map_or(Ok(0usize), |v| format!("{:0<4.4}", v).parse::<usize>())
+        .map_or(Ok(0u64), |v| format!("{:0<4.4}", v).parse::<u64>())
         .map_err(de::Error::custom)?;
 
     Ok(units + dec)
 }
-
-
-