* Features
** TODO Add experiment in experiment.rs to support running same experiment over
   and over for getting precise confidence interval
* Performance
** TODO Parallelize experiment running.
* Crate cleanup
** TODO Cleanup and/or separate binary from library
** TODO Fully-integrate plotters feature into library
** TODO Move Agent creaton helpers into impl proper
* Architecture / Interface
** IDEA Consider replacing halt_check with a fn that returns SimulationState enum
** IDEA Consider adding Experiment structure for better interface
** IDEA Re-evaluate targeting system architecture for messages
Should agents be passed as a graph?
Should agents be in charge of which tickets they receive?
** TODO Remove the "stringly-typed" feel of agents currently.
Change the API so that agent names are statically determined?
** TODO Implement a sort of "next-event" optimization to skip ticks that don't produce events
* Testing
** TODO Add doctests throughout
** TODO Integrate with criterion
* Code Cleanup
** TODO Gracefully degrade Simulations into Failed state in cases of errors
** TODO If possible, move =log= dependency to feature or remove
What's the best practice in Rust? Do people have debug! stmts in libs?
** TODO Consistently use =Self {}= over concrete struct names
* Interface Ergonomics - Low Hanging
** IDEA Check for other places to consider implementing Default.
** WAIT Add =ObjectiveFunction= type definition (once type impl Trait is supported in Stable)
#+BEGIN_SRC rust
/// An ObjectiveFunction is used in simulated annealing and it is the function
/// that we try to maximize when running many simulations.
///
/// For more information on simulated annealing and objective functions, you can refer to the following resources:
/// - Simulated annealing: https://en.wikipedia.org/wiki/Simulated_annealing
/// - Objective function: https://en.wikipedia.org/wiki/Objective_function
///
/// Here is an example usage, in this case findinng the fastest simulation without wasting
/// cycles on too fast of a consuming agent:
/// ```
/// let objective_fn: ObjectiveFunction = |s: &Simulation| {
///    -(s.time as i64)
///        + s.agents
///            .iter()
///            .find(|a| a.name == "consumer")
///            .as_ref()
///            .unwrap()
///            .common_traits
///            .as_ref()
///            .unwrap()
///            .period
///            .unwrap() as i64
/// }
/// ```
pub type ObjectiveFunction = impl Fn(&Simulation) -> i64;
#+END_SRC
** IDEA Fix Poisson<f64> business -- f64 is the wrong type, feels weird/leaky
* Message improvements
** TODO Add Generic data field for Messages
** IDEA Consider allowing Messages w/ no target -- fanout / global broadcast
** TODO Model different types of Messages -- e.g. NewMessage, ConsumedMessage,
  ProducedMessage to dodge the unwraps and solve w/ type system
** TODO Rename various time stamp fields to align on semantics
** IDEA Should Messages be an algebraic type, in fact?
* Bug
* Killed
** KILL Add Default implementation for Message?
Default doesn't make sense for message in its current form.  e.g. String source,
String destination, u64 queued_time have no reasonable default value.
Data structure needs to improve.
** KILL Consider adding params struct for construction of Agents too.