use std::ops::{Index, IndexMut};

use savvy_ffi::{REAL, REALSXP, SEXP};

use super::{impl_common_sexp_ops, impl_common_sexp_ops_owned, Sexp};
use crate::protect;

/// An external SEXP of a real vector.
pub struct RealSexp(pub SEXP);

/// A newly-created SEXP of a real vector.
pub struct OwnedRealSexp {
    inner: SEXP,
    token: SEXP,
    len: usize,
    raw: *mut f64,
}

// implement inner(), len(), empty(), and name()
impl_common_sexp_ops!(RealSexp);
impl_common_sexp_ops_owned!(OwnedRealSexp);

impl RealSexp {
    pub fn as_slice(&self) -> &[f64] {
        unsafe { std::slice::from_raw_parts(REAL(self.0), self.len()) }
    }

    pub fn iter(&self) -> std::slice::Iter<f64> {
        self.as_slice().iter()
    }

    pub fn to_vec(&self) -> Vec<f64> {
        self.as_slice().to_vec()
    }
}

impl OwnedRealSexp {
    pub fn as_read_only(&self) -> RealSexp {
        RealSexp(self.inner)
    }

    pub fn as_slice(&self) -> &[f64] {
        unsafe { std::slice::from_raw_parts(self.raw, self.len) }
    }

    pub fn as_mut_slice(&mut self) -> &mut [f64] {
        unsafe { std::slice::from_raw_parts_mut(self.raw, self.len) }
    }

    pub fn iter(&self) -> std::slice::Iter<f64> {
        self.as_slice().iter()
    }

    pub fn iter_mut(&mut self) -> std::slice::IterMut<f64> {
        self.as_mut_slice().iter_mut()
    }

    pub fn to_vec(&self) -> Vec<f64> {
        self.as_slice().to_vec()
    }

    pub fn set_elt(&mut self, i: usize, v: f64) -> crate::error::Result<()> {
        if i >= self.len {
            return Err(crate::error::Error::new(&format!(
                "index out of bounds: the length is {} but the index is {}",
                self.len, i
            )));
        }

        unsafe {
            *(self.raw.add(i)) = v;
        }

        Ok(())
    }

    fn new_inner(len: usize, init: bool) -> crate::error::Result<Self> {
        let inner = crate::alloc_vector(REALSXP, len as _)?;

        // Fill the vector with default values
        if init {
            unsafe {
                std::ptr::write_bytes(REAL(inner), 0, len);
            }
        }

        Self::new_from_raw_sexp(inner, len)
    }

    /// Constructs a new, initialized real vector.
    pub fn new(len: usize) -> crate::error::Result<Self> {
        Self::new_inner(len, true)
    }

    /// Constructs a new, **uninitialized** real vector.
    ///
    /// This is an expert-only version of `new()`, which can be found useful
    /// when you want to skip initialization and you are confident that the
    /// vector will be filled with values later.
    ///
    /// For example, you can use this in `TryFrom` implementation.
    ///
    /// ``` no_run
    /// struct Pair {
    ///     x: f64,
    ///     y: f64
    /// }
    ///
    /// impl TryFrom<Pair> for Sexp {
    ///     type Error = savvy::Error;
    ///
    ///     fn try_from(value: Pair) -> savvy::Result<Self> {
    ///         let mut out = unsafe { OwnedRealSexp::new_without_init(2)? };
    ///         out[0] = value.x;
    ///         out[1] = value.y;
    ///         
    ///         out.into()
    ///     }
    /// }
    /// ````
    ///
    /// # Safety
    ///
    /// As the memory is uninitialized, all elements must be filled values
    /// before return.
    pub unsafe fn new_without_init(len: usize) -> crate::error::Result<Self> {
        Self::new_inner(len, true)
    }

    fn new_from_raw_sexp(inner: SEXP, len: usize) -> crate::error::Result<Self> {
        let token = protect::insert_to_preserved_list(inner);
        let raw = unsafe { REAL(inner) };

        Ok(Self {
            inner,
            token,
            len,
            raw,
        })
    }
}

impl Drop for OwnedRealSexp {
    fn drop(&mut self) {
        protect::release_from_preserved_list(self.token);
    }
}

// conversions from/to RealSexp ***************

impl TryFrom<Sexp> for RealSexp {
    type Error = crate::error::Error;

    fn try_from(value: Sexp) -> crate::error::Result<Self> {
        if !value.is_real() {
            let type_name = value.get_human_readable_type_name();
            let msg = format!("Expected reals, got {type_name}s");
            return Err(crate::error::Error::UnexpectedType(msg));
        }
        Ok(Self(value.0))
    }
}

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

impl From<RealSexp> for crate::error::Result<Sexp> {
    fn from(value: RealSexp) -> Self {
        Ok(<Sexp>::from(value))
    }
}

// conversions from/to OwnedRealSexp ***************

impl TryFrom<&[f64]> for OwnedRealSexp {
    type Error = crate::error::Error;

    fn try_from(value: &[f64]) -> crate::error::Result<Self> {
        let mut out = unsafe { Self::new_without_init(value.len())? };
        out.as_mut_slice().copy_from_slice(value);
        Ok(out)
    }
}

impl TryFrom<Vec<f64>> for OwnedRealSexp {
    type Error = crate::error::Error;

    fn try_from(value: Vec<f64>) -> crate::error::Result<Self> {
        <Self>::try_from(value.as_slice())
    }
}

impl TryFrom<f64> for OwnedRealSexp {
    type Error = crate::error::Error;

    fn try_from(value: f64) -> crate::error::Result<Self> {
        let sexp = unsafe { crate::unwind_protect(|| savvy_ffi::Rf_ScalarReal(value))? };
        Self::new_from_raw_sexp(sexp, 1)
    }
}

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

impl From<OwnedRealSexp> for crate::error::Result<Sexp> {
    fn from(value: OwnedRealSexp) -> Self {
        Ok(<Sexp>::from(value))
    }
}

macro_rules! impl_try_from_rust_reals {
    ($ty: ty) => {
        impl TryFrom<$ty> for Sexp {
            type Error = crate::error::Error;

            fn try_from(value: $ty) -> crate::error::Result<Self> {
                <OwnedRealSexp>::try_from(value).map(|x| x.into())
            }
        }
    };
}

impl_try_from_rust_reals!(&[f64]);
impl_try_from_rust_reals!(Vec<f64>);
impl_try_from_rust_reals!(f64);

// Index for OwnedRealSexp ***************

impl Index<usize> for OwnedRealSexp {
    type Output = f64;

    fn index(&self, index: usize) -> &Self::Output {
        if index >= self.len {
            panic!(
                "index out of bounds: the length is {} but the index is {}",
                self.len, index
            );
        }
        unsafe { &*(self.raw.add(index)) }
    }
}

impl IndexMut<usize> for OwnedRealSexp {
    fn index_mut(&mut self, index: usize) -> &mut Self::Output {
        if index >= self.len {
            panic!(
                "index out of bounds: the length is {} but the index is {}",
                self.len, index
            );
        }
        unsafe { &mut *(self.raw.add(index)) }
    }
}