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#[cfg(test)]
extern crate tempfile;
#[macro_use]
extern crate failure;
extern crate lazy_init;
 
pub mod trajectory;
pub mod xdr;

use std::fmt;
use failure::Fail;

/// Error class used for different problems with handling trajectories
#[derive(Debug, Fail, Clone)]
#[fail(display="Trajectory Error while {}: {}", operation, code)]
pub struct TrajectoryError {
    /// A hint on what file operation failed
    pub operation: String,

    /// Error code passed from the C library (see xrdfile)
    pub code: u32, 
}

/// Representation of a single frame of an MD trajectory
#[derive(Clone)]
pub struct Frame {
    /// Number of atoms in the frame
    pub num_atoms: u32,

    /// Trajectory step
    pub step: u32,

    /// Time step
    pub time: f32,

    /// 3x3 box vector 
    pub box_vector: [[f32; 3usize]; 3usize],
    
    /// 3D coordinates for N atoms where N is num_atoms 
    pub coords: Vec<[f32; 3usize]>,
}

impl Default for Frame {
    fn default() -> Frame {
        return Frame { 
            num_atoms: 0,
            step: 0,
            time: 0.0,
            box_vector: [[0.0; 3]; 3],
            coords: Vec::with_capacity(0)
        };
    }
}

impl fmt::Debug for Frame {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "Frame {{ atoms: {}, step: {}, time: {}, \
            box: {:?}, coords: {:?} }}", self.num_atoms, self.step, self.time,
            self.box_vector, self.coords)
    }
}

impl Frame {
    pub fn new() -> Frame {
        return Frame{ ..Default::default() };
    }

    pub fn with_capacity(num_atoms: u32) -> Frame {
        return Frame {
            num_atoms: num_atoms,
            coords: vec![[0.0, 0.0, 0.0]; num_atoms as usize],
            ..Default::default()
        };

    }

    pub fn filter_coords(self: &mut Frame, indeces: &[usize]) {
        self.coords = self.coords.iter()  // TODO faster implementation? 
            .map(|elem| elem.clone())
            .enumerate()
            .filter(|&(i, _)| indeces.contains(&i))
            .map(|(_, elem)| elem)
            .collect();
        self.num_atoms = self.coords.len() as u32;
    }    
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_frame_with_capacity() {
        let frame = Frame::with_capacity(10);
        println!("{:?}", frame.coords);
        assert_eq!(frame.coords.len(), 10);
    }

    #[test]
    fn test_frame_default_capacity() {
        let frame = Frame::new();
        assert_eq!(frame.coords.len(), 0);
    }

    #[test]
    fn test_frame_filter_atoms() {
        let mut frame = Frame::with_capacity(3);
        frame.coords[0] = [1.0, 2.0, 3.0];
        frame.coords[1] = [4.0, 5.0, 6.0];
        frame.coords[2] = [7.0, 8.0, 9.0];
        let filter: Vec<usize> = vec![1,2];
        let mut frame_new = frame.clone();
        frame_new.filter_coords(&filter);
        assert!(frame_new.num_atoms as usize == filter.len());
        assert!(frame_new.coords[0] == frame.coords[1]);
        assert!(frame_new.coords[1] == frame.coords[2]);           
    }
}