#![allow(dead_code)]
use std::collections::HashMap;

struct KVDB {
    entries: HashMap<String, String>,
}

impl KVDB {
    /// Creates a new instance of the key-value store.
    pub fn new() -> KVDB {
        KVDB {
            entries: HashMap::new(),
        }
    }

    /// Retrieves a value given a key.
    pub fn get(&self, key: &str) -> Option<String> {
        self.entries
            .get(&key.to_string()).cloned()
    }

    /// Stores a value into its given key.
    pub fn put(&mut self, key: &str, value: &str) -> Result<String, String> {
        let action = self.entries.insert(key.to_string(), value.to_string());
        {
            match action {
                None => Ok("added".to_string()),
                _ => Ok("modified".to_string()),
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_basics() {
        let mut kvdb = KVDB::new();
        assert_eq!(kvdb.put("a", "b"), Ok("added".to_string()));
        assert_eq!(kvdb.get("a"), Some("b".to_string()));
        assert_eq!(kvdb.put("a", "c"), Ok("modified".to_string()));
        assert_eq!(kvdb.get("b"), None);
    }

    #[test]
    fn test_inserting_types() {
        let mut kvdb = KVDB::new();
        assert_eq!(kvdb.put("a", "b"), Ok("added".to_string()));
        assert_eq!(kvdb.put(&"b".to_string(), "b"), Ok("added".to_string()));
    }
}

fn main() {}