refactor(users/glittershark): Rename to grfn

Rename my //users directory and all places that refer to glittershark to
grfn, including nix references and documentation.

This may require some extra attention inside of gerrit's database after
it lands to allow me to actually push things.

Change-Id: I4728b7ec2c60024392c1c1fa6e0d4a59b3e266fa
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2933
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>
Reviewed-by: lukegb <lukegb@tvl.fyi>
Reviewed-by: glittershark <grfn@gws.fyi>

users/grfn/achilles/src/common/namer.rs

@@ -0,0 +1,122 @@
+use std::fmt::Display;
+use std::marker::PhantomData;
+
+pub struct Namer<T, F> {
+    make_name: F,
+    counter: u64,
+    _phantom: PhantomData<T>,
+}
+
+impl<T, F> Namer<T, F> {
+    pub fn new(make_name: F) -> Self {
+        Namer {
+            make_name,
+            counter: 0,
+            _phantom: PhantomData,
+        }
+    }
+}
+
+impl Namer<String, Box<dyn Fn(u64) -> String>> {
+    pub fn with_prefix<T>(prefix: T) -> Self
+    where
+        T: Display + 'static,
+    {
+        Namer::new(move |i| format!("{}{}", prefix, i)).boxed()
+    }
+
+    pub fn with_suffix<T>(suffix: T) -> Self
+    where
+        T: Display + 'static,
+    {
+        Namer::new(move |i| format!("{}{}", i, suffix)).boxed()
+    }
+
+    pub fn alphabetic() -> Self {
+        Namer::new(|i| {
+            if i <= 26 {
+                std::char::from_u32((i + 96) as u32).unwrap().to_string()
+            } else {
+                format!(
+                    "{}{}",
+                    std::char::from_u32(((i % 26) + 96) as u32).unwrap(),
+                    i - 26
+                )
+            }
+        })
+        .boxed()
+    }
+}
+
+impl<T, F> Namer<T, F>
+where
+    F: Fn(u64) -> T,
+{
+    pub fn make_name(&mut self) -> T {
+        self.counter += 1;
+        (self.make_name)(self.counter)
+    }
+
+    pub fn boxed(self) -> NamerOf<T>
+    where
+        F: 'static,
+    {
+        Namer {
+            make_name: Box::new(self.make_name),
+            counter: self.counter,
+            _phantom: self._phantom,
+        }
+    }
+
+    pub fn map<G, U>(self, f: G) -> NamerOf<U>
+    where
+        G: Fn(T) -> U + 'static,
+        T: 'static,
+        F: 'static,
+    {
+        Namer {
+            counter: self.counter,
+            make_name: Box::new(move |x| f((self.make_name)(x))),
+            _phantom: PhantomData,
+        }
+    }
+}
+
+pub type NamerOf<T> = Namer<T, Box<dyn Fn(u64) -> T>>;
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn prefix() {
+        let mut namer = Namer::with_prefix("t");
+        assert_eq!(namer.make_name(), "t1");
+        assert_eq!(namer.make_name(), "t2");
+    }
+
+    #[test]
+    fn suffix() {
+        let mut namer = Namer::with_suffix("t");
+        assert_eq!(namer.make_name(), "1t");
+        assert_eq!(namer.make_name(), "2t");
+    }
+
+    #[test]
+    fn alphabetic() {
+        let mut namer = Namer::alphabetic();
+        assert_eq!(namer.make_name(), "a");
+        assert_eq!(namer.make_name(), "b");
+        (0..25).for_each(|_| {
+            namer.make_name();
+        });
+        assert_eq!(namer.make_name(), "b2");
+    }
+
+    #[test]
+    fn custom_callback() {
+        let mut namer = Namer::new(|n| n + 1);
+        assert_eq!(namer.make_name(), 2);
+        assert_eq!(namer.make_name(), 3);
+    }
+}