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extern crate rayon;
extern crate thiserror;

pub use add::*;
pub use ard::*;
pub use bias::*;
pub use convolutional::*;
pub use exponential::*;
pub use instant::*;
pub use linear::*;
pub use mul::*;
pub use periodic::*;
pub use rbf::*;
use std::fmt::Debug;

pub mod add;
pub mod ard;
pub mod bias;
pub mod convolutional;
pub mod exponential;
pub mod instant;
pub mod linear;
pub mod mul;
pub mod periodic;
pub mod rbf;

pub trait Value: Clone + Debug + PartialEq + Send + Sync {}
impl<T> Value for T where T: Clone + Debug + PartialEq + Send + Sync {}

pub trait Kernel<T>: Clone + Debug + Send + Sync
where
  T: Value,
{
  fn params_len(&self) -> usize;

  fn value(&self, params: &[f64], x: &T, xprime: &T) -> Result<f64, KernelError>;

  fn value_with_grad(
    &self,
    params: &[f64],
    x: &T,
    xprime: &T,
  ) -> Result<(f64, Vec<f64>), KernelError>;
}

#[derive(thiserror::Error, Debug)]
pub enum KernelError {
  #[error("parameters length mismatch")]
  ParametersLengthMismatch,
  #[error("invalid parameter")]
  InvalidParameter,
  #[error("invalid argument")]
  InvalidArgument,
}

#[cfg(test)]
mod tests {
  use crate::*;
  #[test]
  fn it_works() {
    let kernel = RBF + Bias * Linear + Bias * Periodic + Bias * ARD(3);
    let (func, grad) = kernel
      .value_with_grad(
        &vec![1.0; kernel.params_len()],
        &vec![1.0, 2.0, 3.0],
        &vec![10.0, 20.0, 30.0],
      )
      .unwrap();

    println!("{}", func);
    println!("{:#?}", grad);
  }
}