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use ndarray::Array2;
use ndarray_rand::{rand_distr::Normal, RandomExt};

use super::activation_function::ActivationFunction;

pub struct Layer<'a> {
    pub weights: Array2<f64>,
    pub biases: Array2<f64>,
    pub activation: &'a ActivationFunction,
}

impl Layer<'_> {
    pub fn new(input_size: usize, output_size: usize, activation: &ActivationFunction) -> Layer {
        let weights = Array2::random((input_size, output_size), Normal::new(0.0, 1.0).unwrap())
            / (input_size as f64).sqrt();
        let biases = Array2::random((1, output_size), Normal::new(0.0, 0.1).unwrap());

        Layer {
            weights,
            biases,
            activation,
        }
    }

    // Predicts the output of the layer given an input
    pub fn predict(&self, input: &Array2<f64>) -> Array2<f64> {
        self.activation.function(&self.forward(input))
    }

    // Calculates the weighted sum of the input
    pub fn forward(&self, input: &Array2<f64>) -> Array2<f64> {
        input.dot(&self.weights) + &self.biases
    }
}