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extern crate rayon;
extern crate thiserror;

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

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

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

    fn value(
        &self,
        params: &[f64],
        x: &T,
        xprime: &T,
        with_grad: bool,
    ) -> Result<(f64, Vec<f64>), Box<dyn Error>>;
}

#[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(
                &vec![1.0; kernel.params_len()],
                &vec![1.0, 2.0, 3.0],
                &vec![10.0, 20.0, 30.0],
                true,
            )
            .unwrap();

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