init

04-typestate/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "typestate"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

04-typestate/src/main.rs

@@ -0,0 +1,54 @@
+#![allow(unused)]
+
+use std::collections::HashMap;
+
+struct Locked;
+struct Unlocked;
+
+struct CredentialManager<State = Locked> {
+    entries: HashMap<String, String>,
+    state: std::marker::PhantomData<State>,
+}
+
+impl CredentialManager {
+    pub fn new() -> CredentialManager<Locked> {
+        CredentialManager {
+            entries: HashMap::new(),
+            state: std::marker::PhantomData,
+        }
+    }
+}
+
+impl CredentialManager<Locked> {
+    pub fn unlock(self, master_secret: &str) -> CredentialManager<Unlocked> {
+        CredentialManager {
+            entries: self.entries,
+            state: std::marker::PhantomData,
+        }
+    }
+}
+
+impl CredentialManager<Unlocked> {
+    pub fn set(&mut self, key: &str, secret: &str) {
+        todo!()
+    }
+
+    pub fn get(&mut self, key: &str) -> Option<&str> {
+        todo!()
+    }
+
+    pub fn lock(self) -> CredentialManager<Locked> {
+        CredentialManager {
+            entries: self.entries,
+            state: std::marker::PhantomData,
+        }
+    }
+}
+
+fn main() {
+    let pw = CredentialManager::new();
+    let mut pw = pw.unlock("pssst");
+    pw.set("foo", "bar");
+    let val = pw.get("foo");
+    pw.lock();
+}