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// mods

// [[file:~/Workspace/Programming/gchemol-rs/gchemol-geometry/gchemol-geometry.note::*mods][mods:1]]
mod qcprot;
// mod quaternion;
// mods:1 ends here

// imports

// [[file:~/Workspace/Programming/gchemol-rs/gchemol-geometry/gchemol-geometry.note::*imports][imports:1]]
use gchemol_gut::prelude::*;

use vecfx::Matrix3f;
use vecfx::Vector3f;
// imports:1 ends here

// superpose

// [[file:~/Workspace/Programming/gchemol-rs/gchemol-geometry/gchemol-geometry.note::*superpose][superpose:1]]
#[derive(Clone, Copy, Debug)]
pub enum SuperpositionAlgo {
    QCP,
    Quaternion,
}

impl Default for SuperpositionAlgo {
    fn default() -> Self {
        SuperpositionAlgo::QCP
        // SuperpositionAlgo::Quaternion
    }
}

/// The result of alignment defining how to superimpose.
#[derive(Clone, Debug)]
pub struct Superposition {
    /// superpostion rmsd
    pub rmsd: f64,

    /// translation vector
    pub translation: Vector3f,

    /// rotation matrix
    pub rotation_matrix: Matrix3f,
}

impl Superposition {
    /// Apply superposition to other structure
    pub fn apply(&self, conf: &[[f64; 3]]) -> Vec<[f64; 3]> {
        let mut res = Vec::with_capacity(conf.len());
        for &v in conf {
            let v = Vector3f::from(v);
            let v = self.rotation_matrix * v + self.translation;
            res.push(v.into());
        }

        res
    }
}

/// Alignment of candidate structure onto the reference
#[derive(Clone, Debug)]
pub struct Alignment<'a> {
    /// The positions of the candidate structure
    positions: &'a [[f64; 3]],

    /// Select algo
    pub algorithm: SuperpositionAlgo,
}

impl<'a> Alignment<'a> {
    /// Construct from positions of the candidate to be aligned
    pub fn new(positions: &'a [[f64; 3]]) -> Self {
        Alignment {
            positions,
            algorithm: SuperpositionAlgo::default(),
        }
    }

    /// Calculate Root-mean-square deviation of self with the reference coordinates
    ///
    /// Parameters
    /// ----------
    /// * reference: reference coordinates
    /// * weights  : weight of each point
    pub fn rmsd(&self, reference: &[[f64; 3]], weights: Option<&[f64]>) -> Result<f64> {
        // sanity check
        let npts = self.positions.len();
        if reference.len() != npts {
            bail!("points size mismatch!");
        }
        if weights.is_some() && weights.unwrap().len() != npts {
            bail!("weights size mismatch!");
        }

        // calculate rmsd
        let mut ws = 0.0f64;
        for i in 0..npts {
            // take the weight if any, or set it to 1.0
            let wi = weights.map_or_else(|| 1.0, |w| w[i]);
            let dx = wi * (self.positions[i][0] - reference[i][0]);
            let dy = wi * (self.positions[i][1] - reference[i][1]);
            let dz = wi * (self.positions[i][2] - reference[i][2]);

            ws += dx.powi(2) + dy.powi(2) + dz.powi(2);
        }
        let ws = ws.sqrt();

        Ok(ws)
    }

    /// Superpose candidate structure onto reference structure which will be held fixed
    /// Return superposition struct
    ///
    /// Parameters
    /// ----------
    /// * reference: reference coordinates
    /// * weights  : weight of each point
    pub fn superpose(&mut self, reference: &[[f64; 3]], weights: Option<&[f64]>) -> Result<Superposition> {
        // calculate the RMSD & rotational matrix
        let (rmsd, trans, rot) = match self.algorithm {
            SuperpositionAlgo::QCP => self::qcprot::calc_rmsd_rotational_matrix(&reference, &self.positions, weights),
            SuperpositionAlgo::Quaternion => {
                // self::quaternion::calc_rmsd_rotational_matrix(&reference, &self.positions, weights)
                todo!()
            }
        };

        // return unit matrix if two structures are already close enough
        let rotation_matrix = if let Some(rot) = rot {
            Matrix3f::from_row_slice(&rot)
        } else {
            Matrix3f::identity()
        };

        // return superimposition result
        let sp = Superposition {
            rmsd,
            translation: trans.into(),
            rotation_matrix,
        };

        Ok(sp)
    }
}
// superpose:1 ends here

// test

// [[file:~/Workspace/Programming/gchemol-rs/gchemol-geometry/gchemol-geometry.note::*test][test:1]]
#[test]
fn test_alignment() {
    use approx::*;

    // fragment a
    let (reference, candidate, weights) = qcprot::prepare_test_data();

    // construct alignment for superimposition
    let mut align = Alignment::new(&candidate);

    // alignment result
    let sp = align.superpose(&reference, Some(&weights)).unwrap();
    let rot = sp.rotation_matrix;

    // validation
    let rot_expected = Matrix3f::from_row_slice(&[
        0.77227551,
        0.63510272,
        -0.01533190,
        -0.44544846,
        0.52413614,
        -0.72584914,
        -0.45295276,
        0.56738509,
        0.68768304,
    ]);
    assert_relative_eq!(rot_expected, rot, epsilon = 1e-4);
}
// test:1 ends here