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use nalgebra::Point3;

use crate::ArraySequence;

pub type Point = Point3<f32>;
pub type Points = Vec<Point>;
pub type Streamlines = ArraySequence<Point>;

pub type TractogramItem = (Points, ArraySequence<f32>, Vec<f32>);
pub type RefTractogramItem<'data> = (&'data [Point], &'data [f32], &'data [f32]);

#[derive(Clone, PartialEq)]
pub struct Tractogram {
    pub streamlines: Streamlines,
    pub scalars: ArraySequence<f32>,
    pub properties: ArraySequence<f32>,
}

impl Tractogram {
    pub fn new(
        streamlines: Streamlines,
        scalars: ArraySequence<f32>,
        properties: ArraySequence<f32>,
    ) -> Tractogram {
        Tractogram { streamlines, scalars, properties }
    }

    pub fn item(&self, idx: usize) -> RefTractogramItem {
        // Do not use .get(idx).unwrap_or(). The empty slice is valid only if the ArraySequence are
        // empty. It should crash if the index is invalid.
        let scalars = if self.scalars.is_empty() { &[] } else { &self.scalars[idx] };
        let properties = if self.properties.is_empty() { &[] } else { &self.properties[idx] };
        (&self.streamlines[idx], scalars, properties)
    }
}

impl<'data> IntoIterator for &'data Tractogram {
    type Item = RefTractogramItem<'data>;
    type IntoIter = TractogramIterator<'data>;

    fn into_iter(self) -> Self::IntoIter {
        TractogramIterator { tractogram: self, index: 0..self.streamlines.len() }
    }
}

pub struct TractogramIterator<'data> {
    tractogram: &'data Tractogram,
    index: std::ops::Range<usize>,
}

impl<'data> Iterator for TractogramIterator<'data> {
    type Item = RefTractogramItem<'data>;

    fn next(&mut self) -> Option<Self::Item> {
        let idx = self.index.next()?;
        Some(self.tractogram.item(idx))
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        (0, Some(self.tractogram.streamlines.len()))
    }
}

impl<'data> ExactSizeIterator for TractogramIterator<'data> {}

impl<'data> DoubleEndedIterator for TractogramIterator<'data> {
    fn next_back(&mut self) -> Option<Self::Item> {
        let idx = self.index.next_back()?;
        Some(self.tractogram.item(idx))
    }
}