qudit-expr 0.3.4

use std::ops::{Deref, DerefMut};

use crate::{
    GenerationShape, TensorExpression,
    expressions::JittableExpression,
    index::{IndexDirection, TensorIndex},
};

use super::NamedExpression;
use qudit_core::QuditSystem;
use qudit_core::Radices;

#[derive(PartialEq, Eq, Debug, Clone)]
pub struct KetSystemExpression {
    inner: NamedExpression,
    radices: Radices,
    num_states: usize,
}

impl JittableExpression for KetSystemExpression {
    fn generation_shape(&self) -> GenerationShape {
        GenerationShape::Tensor3D(self.num_states, self.radices.dimension(), 1)
    }
}

impl AsRef<NamedExpression> for KetSystemExpression {
    fn as_ref(&self) -> &NamedExpression {
        &self.inner
    }
}

impl From<KetSystemExpression> for NamedExpression {
    fn from(value: KetSystemExpression) -> Self {
        value.inner
    }
}

impl Deref for KetSystemExpression {
    type Target = NamedExpression;

    fn deref(&self) -> &Self::Target {
        &self.inner
    }
}

impl DerefMut for KetSystemExpression {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.inner
    }
}

impl From<KetSystemExpression> for TensorExpression {
    fn from(value: KetSystemExpression) -> Self {
        let KetSystemExpression {
            inner,
            radices,
            num_states,
        } = value;
        // TODO: add a proper implementation of into_iter for QuditRadices
        let indices = [num_states]
            .into_iter()
            .map(|r| (IndexDirection::Batch, r))
            .chain(
                radices
                    .iter()
                    .map(|r| (IndexDirection::Output, usize::from(*r))),
            )
            .enumerate()
            .map(|(i, (d, r))| TensorIndex::new(d, i, r))
            .collect();
        TensorExpression::from_raw(indices, inner)
    }
}

impl TryFrom<TensorExpression> for KetSystemExpression {
    // TODO: Come up with proper error handling
    type Error = String;

    fn try_from(value: TensorExpression) -> Result<Self, Self::Error> {
        let mut num_states = None;
        let mut radices = vec![];
        for idx in value.indices() {
            match idx.direction() {
                IndexDirection::Batch => match num_states {
                    Some(n) => num_states = Some(n * idx.index_size()),
                    None => num_states = Some(idx.index_size()),
                },
                IndexDirection::Output => {
                    radices.push(idx.index_size());
                }
                _ => {
                    return Err(String::from(
                        "Cannot convert a tensor with non-output or batch indices to a ket system.",
                    ));
                }
            }
        }

        Ok(KetSystemExpression {
            inner: value.into(),
            radices: radices.into(),
            num_states: num_states.unwrap_or(1),
        })
    }
}