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use ark_ff::PrimeField;

mod external;
mod internal;

use crate::{alpha, input::InputParameters, round_constants, rounds};
use poseidon_parameters::v2::{PoseidonParameters, SquareMatrix};

/// For generating parameters at build time.
pub mod poseidon_build {
    pub use crate::poseidon_build::v2_compile as compile;
}

/// Generate a Poseidon2 instance mapped over Fp given a choice of:
///
/// * M, the desired security level (in bits),
/// * t, the width of the desired hash function, e.g. $t=3$ corresponds to 2-to-1 hash.
/// * p, the prime modulus,
/// * `allow_inverse`, whether or not to allow an inverse alpha.
pub fn generate<F: PrimeField>(
    M: usize,
    t: usize,
    p: F::BigInt,
    allow_inverse: bool,
) -> PoseidonParameters<F> {
    let input = InputParameters::generate(M, t, p, allow_inverse);
    let alpha = alpha::generate::<F>(p, allow_inverse);
    let rounds = rounds::v2_generate(&input, &alpha);
    let arc = round_constants::v2_generate(&input, rounds, alpha);
    let m_i: SquareMatrix<F> = internal::generate(t);

    // We use the internal matrix also for the external rounds if t < 4.
    if t < 4 {
        PoseidonParameters::<F> {
            M: input.M,
            t: input.t,
            alpha,
            rounds,
            arc,
            m_i: m_i.clone(),
            m_e: m_i,
        }
    } else {
        let m_e = external::generate(t);
        PoseidonParameters::<F> {
            M: input.M,
            t: input.t,
            alpha,
            rounds,
            arc,
            m_e,
            m_i,
        }
    }
}