//! There are various ways an [`Robj`] may be converted into different types `T`.
//!
//! This module defines these conversions on `&Robj`. Due to internal reference
//! counting measure of [`ownership`]-module, it is cheaper to copy `&Robj`,
//! than copying `Robj`, as the latter will incur an increase in reference counting.
//!
//!
//! [`ownership`]: crate::ownership
use crate::conversions::try_into_int::FloatToInt;

use super::*;

macro_rules! impl_try_from_scalar_integer {
    ($t:ty) => {
        impl TryFrom<&Robj> for $t {
            type Error = Error;

            /// Convert a numeric object to an integer value.
            fn try_from(robj: &Robj) -> Result<Self> {
                // Check if the value is a scalar
                match robj.len() {
                    0 => return Err(Error::ExpectedNonZeroLength(robj.clone())),
                    1 => {}
                    _ => return Err(Error::ExpectedScalar(robj.clone())),
                };

                // Check if the value is not a missing value
                if robj.is_na() {
                    return Err(Error::MustNotBeNA(robj.clone()));
                }

                // If the conversion is int-to-int, check the limits. This
                // needs to be done by `TryFrom` because the conversion by `as`
                // is problematic when converting a negative value to unsigned
                // integer types (e.g. `-1i32 as u8` becomes 255).
                if let Some(v) = robj.as_integer() {
                    if let Ok(v) = Self::try_from(v) {
                        return Ok(v);
                    } else {
                        return Err(Error::OutOfLimits(robj.clone()));
                    }
                }

                // If the conversion is float-to-int, check if the value is
                // integer-like (i.e., an integer, or a float representing a
                // whole number).
                if let Some(v) = robj.as_real() {
                    return v
                        .try_into_int()
                        .map_err(|conv_err| Error::ExpectedWholeNumber(robj.clone(), conv_err));
                }

                Err(Error::ExpectedNumeric(robj.clone()))
            }
        }
    };
}

macro_rules! impl_try_from_scalar_real {
    ($t:ty) => {
        impl TryFrom<&Robj> for $t {
            type Error = Error;

            /// Convert a numeric object to a real value.
            fn try_from(robj: &Robj) -> Result<Self> {
                // Check if the value is a scalar
                match robj.len() {
                    0 => return Err(Error::ExpectedNonZeroLength(robj.clone())),
                    1 => {}
                    _ => return Err(Error::ExpectedScalar(robj.clone())),
                };

                // Check if the value is not a missing value
                if robj.is_na() {
                    return Err(Error::MustNotBeNA(robj.clone()));
                }

                // `<Robj>::as_xxx()` methods can work only when the underlying
                // `SEXP` is the corresponding type, so we cannot use `as_real()`
                // directly on `INTSXP`.
                if let Some(v) = robj.as_real() {
                    // f64 to f32 and f64 to f64 is always safe.
                    return Ok(v as Self);
                }
                if let Some(v) = robj.as_integer() {
                    // An i32 R integer can be represented exactly by f64, but might be truncated in f32.
                    return Ok(v as Self);
                }

                Err(Error::ExpectedNumeric(robj.clone()))
            }
        }
    };
}

impl_try_from_scalar_integer!(u8);
impl_try_from_scalar_integer!(u16);
impl_try_from_scalar_integer!(u32);
impl_try_from_scalar_integer!(u64);
impl_try_from_scalar_integer!(usize);
impl_try_from_scalar_integer!(i8);
impl_try_from_scalar_integer!(i16);
impl_try_from_scalar_integer!(i32);
impl_try_from_scalar_integer!(i64);
impl_try_from_scalar_integer!(isize);
impl_try_from_scalar_real!(f32);
impl_try_from_scalar_real!(f64);

impl TryFrom<&Robj> for bool {
    type Error = Error;

    /// Convert an LGLSXP object into a boolean.
    /// NAs are not allowed.
    fn try_from(robj: &Robj) -> Result<Self> {
        if robj.is_na() {
            Err(Error::MustNotBeNA(robj.clone()))
        } else {
            Ok(<Rbool>::try_from(robj)?.is_true())
        }
    }
}

impl TryFrom<&Robj> for &str {
    type Error = Error;

    /// Convert a scalar STRSXP object into a string slice.
    /// NAs are not allowed.
    fn try_from(robj: &Robj) -> Result<Self> {
        if robj.is_na() {
            return Err(Error::MustNotBeNA(robj.clone()));
        }
        match robj.len() {
            0 => Err(Error::ExpectedNonZeroLength(robj.clone())),
            1 => {
                if let Some(s) = robj.as_str() {
                    Ok(s)
                } else {
                    Err(Error::ExpectedString(robj.clone()))
                }
            }
            _ => Err(Error::ExpectedScalar(robj.clone())),
        }
    }
}

impl TryFrom<&Robj> for String {
    type Error = Error;

    /// Convert an scalar STRSXP object into a String.
    /// Note: Unless you plan to store the result, use a string slice instead.
    /// NAs are not allowed.
    fn try_from(robj: &Robj) -> Result<Self> {
        <&str>::try_from(robj).map(|s| s.to_string())
    }
}

impl TryFrom<&Robj> for Vec<i32> {
    type Error = Error;

    /// Convert an INTSXP object into a vector of i32 (integer).
    /// Note: Unless you plan to store the result, use a slice instead.
    /// Use `value.is_na()` to detect NA values.
    fn try_from(robj: &Robj) -> Result<Self> {
        if let Some(v) = robj.as_typed_slice() {
            // TODO: check NAs
            Ok(Vec::from(v))
        } else {
            Err(Error::ExpectedInteger(robj.clone()))
        }
    }
}

impl TryFrom<&Robj> for Vec<f64> {
    type Error = Error;

    /// Convert a REALSXP object into a vector of f64 (double precision floating point).
    /// Note: Unless you plan to store the result, use a slice instead.
    /// Use `value.is_na()` to detect NA values.
    fn try_from(robj: &Robj) -> Result<Self> {
        if let Some(v) = robj.as_typed_slice() {
            // TODO: check NAs
            Ok(Vec::from(v))
        } else {
            Err(Error::ExpectedReal(robj.clone()))
        }
    }
}

impl TryFrom<&Robj> for Vec<u8> {
    type Error = Error;

    /// Convert a RAWSXP object into a vector of bytes.
    /// Note: Unless you plan to store the result, use a slice instead.
    fn try_from(robj: &Robj) -> Result<Self> {
        if let Some(v) = robj.as_typed_slice() {
            Ok(Vec::from(v))
        } else {
            Err(Error::ExpectedRaw(robj.clone()))
        }
    }
}

impl TryFrom<&Robj> for Vec<Rint> {
    type Error = Error;

    /// Convert an INTSXP object into a vector of i32 (integer).
    /// Note: Unless you plan to store the result, use a slice instead.
    /// Use `value.is_na()` to detect NA values.
    fn try_from(robj: &Robj) -> Result<Self> {
        if let Some(v) = robj.as_typed_slice() {
            Ok(Vec::from(v))
        } else {
            Err(Error::ExpectedInteger(robj.clone()))
        }
    }
}

impl TryFrom<&Robj> for Vec<Rfloat> {
    type Error = Error;

    /// Convert a REALSXP object into a vector of f64 (double precision floating point).
    /// Note: Unless you plan to store the result, use a slice instead.
    /// Use `value.is_na()` to detect NA values.
    fn try_from(robj: &Robj) -> Result<Self> {
        if let Some(v) = robj.as_typed_slice() {
            Ok(Vec::from(v))
        } else {
            Err(Error::ExpectedReal(robj.clone()))
        }
    }
}

impl TryFrom<&Robj> for Vec<Rbool> {
    type Error = Error;

    /// Convert a LGLSXP object into a vector of Rbool (tri-state booleans).
    /// Note: Unless you plan to store the result, use a slice instead.
    /// Use `value.is_na()` to detect NA values.
    fn try_from(robj: &Robj) -> Result<Self> {
        if let Some(v) = robj.as_typed_slice() {
            Ok(Vec::from(v))
        } else {
            Err(Error::ExpectedInteger(robj.clone()))
        }
    }
}

impl TryFrom<&Robj> for Vec<Rcplx> {
    type Error = Error;

    /// Convert a complex object into a vector of Rcplx.
    fn try_from(robj: &Robj) -> Result<Self> {
        if let Some(v) = robj.as_typed_slice() {
            Ok(Vec::from(v))
        } else {
            Err(Error::ExpectedComplex(robj.clone()))
        }
    }
}

impl TryFrom<&Robj> for Vec<String> {
    type Error = Error;

    /// Convert a STRSXP object into a vector of `String`s.
    /// Note: Unless you plan to store the result, use a slice instead.
    fn try_from(robj: &Robj) -> Result<Self> {
        if let Some(iter) = robj.as_str_iter() {
            // check for NA's in the string vector
            if iter.clone().any(|s| s.is_na()) {
                Err(Error::MustNotBeNA(robj.clone()))
            } else {
                Ok(iter.map(|s| s.to_string()).collect::<Vec<String>>())
            }
        } else {
            Err(Error::ExpectedString(robj.clone()))
        }
    }
}

impl TryFrom<&Robj> for &[i32] {
    type Error = Error;

    /// Convert an INTSXP object into a slice of i32 (integer).
    /// Use `value.is_na()` to detect NA values.
    fn try_from(robj: &Robj) -> Result<Self> {
        robj.as_typed_slice()
            .ok_or_else(|| Error::ExpectedInteger(robj.clone()))
    }
}

impl TryFrom<&Robj> for &[Rint] {
    type Error = Error;

    /// Convert an integer object into a slice of Rint (tri-state booleans).
    /// Use `value.is_na()` to detect NA values.
    fn try_from(robj: &Robj) -> Result<Self> {
        robj.as_typed_slice()
            .ok_or_else(|| Error::ExpectedInteger(robj.clone()))
    }
}

impl TryFrom<&Robj> for &[Rfloat] {
    type Error = Error;

    /// Convert a doubles object into a slice of Rfloat (tri-state booleans).
    /// Use `value.is_na()` to detect NA values.
    fn try_from(robj: &Robj) -> Result<Self> {
        robj.as_typed_slice()
            .ok_or_else(|| Error::ExpectedReal(robj.clone()))
    }
}

impl TryFrom<&Robj> for &[Rbool] {
    type Error = Error;

    /// Convert a logical object into a slice of Rbool (tri-state booleans).
    /// Use `value.is_na()` to detect NA values.
    fn try_from(robj: &Robj) -> Result<Self> {
        robj.as_typed_slice()
            .ok_or_else(|| Error::ExpectedLogical(robj.clone()))
    }
}

impl TryFrom<&Robj> for &[Rcplx] {
    type Error = Error;

    /// Convert a complex object into a slice of Rcplx
    /// Use `value.is_na()` to detect NA values.
    fn try_from(robj: &Robj) -> Result<Self> {
        robj.as_typed_slice()
            .ok_or_else(|| Error::ExpectedComplex(robj.clone()))
    }
}

impl TryFrom<&Robj> for &[u8] {
    type Error = Error;

    /// Convert a RAWSXP object into a slice of bytes.
    fn try_from(robj: &Robj) -> Result<Self> {
        robj.as_typed_slice()
            .ok_or_else(|| Error::ExpectedRaw(robj.clone()))
    }
}

impl TryFrom<&Robj> for &[f64] {
    type Error = Error;

    /// Convert a REALSXP object into a slice of f64 (double precision floating point).
    /// Use `value.is_na()` to detect NA values.
    fn try_from(robj: &Robj) -> Result<Self> {
        robj.as_typed_slice()
            .ok_or_else(|| Error::ExpectedReal(robj.clone()))
    }
}

impl TryFrom<&mut Robj> for &mut [i32] {
    type Error = Error;

    /// Convert an INTSXP object into a mutable slice of i32 (integer).
    /// Use `value.is_na()` to detect NA values.
    fn try_from(robj: &mut Robj) -> Result<Self> {
        robj.as_typed_slice_mut()
            .ok_or_else(|| Error::ExpectedInteger(robj.clone()))
    }
}

impl TryFrom<&mut Robj> for &mut [Rint] {
    type Error = Error;

    /// Convert an integer object into a mutable slice of Rint (tri-state booleans).
    /// Use `value.is_na()` to detect NA values.
    fn try_from(robj: &mut Robj) -> Result<Self> {
        robj.as_typed_slice_mut()
            .ok_or_else(|| Error::ExpectedInteger(robj.clone()))
    }
}

impl TryFrom<&mut Robj> for &mut [Rfloat] {
    type Error = Error;

    /// Convert a doubles object into a mutable slice of Rfloat (tri-state booleans).
    /// Use `value.is_na()` to detect NA values.
    fn try_from(robj: &mut Robj) -> Result<Self> {
        robj.as_typed_slice_mut()
            .ok_or_else(|| Error::ExpectedReal(robj.clone()))
    }
}

impl TryFrom<&mut Robj> for &mut [Rbool] {
    type Error = Error;

    /// Convert a logical object into a mutable slice of Rbool (tri-state booleans).
    /// Use `value.is_na()` to detect NA values.
    fn try_from(robj: &mut Robj) -> Result<Self> {
        robj.as_typed_slice_mut()
            .ok_or_else(|| Error::ExpectedLogical(robj.clone()))
    }
}

impl TryFrom<&mut Robj> for &mut [Rcplx] {
    type Error = Error;

    /// Convert a complex object into a mutable slice of Rcplx
    /// Use `value.is_na()` to detect NA values.
    fn try_from(robj: &mut Robj) -> Result<Self> {
        robj.as_typed_slice_mut()
            .ok_or_else(|| Error::ExpectedComplex(robj.clone()))
    }
}

impl TryFrom<&mut Robj> for &mut [u8] {
    type Error = Error;

    /// Convert a RAWSXP object into a mutable slice of bytes.
    fn try_from(robj: &mut Robj) -> Result<Self> {
        robj.as_typed_slice_mut()
            .ok_or_else(|| Error::ExpectedRaw(robj.clone()))
    }
}

impl TryFrom<&mut Robj> for &mut [f64] {
    type Error = Error;

    /// Convert a REALSXP object into a mutable slice of f64 (double precision floating point).
    /// Use `value.is_na()` to detect NA values.
    fn try_from(robj: &mut Robj) -> Result<Self> {
        robj.as_typed_slice_mut()
            .ok_or_else(|| Error::ExpectedReal(robj.clone()))
    }
}

impl TryFrom<&Robj> for Rcplx {
    type Error = Error;

    fn try_from(robj: &Robj) -> Result<Self> {
        // Check if the value is a scalar
        match robj.len() {
            0 => return Err(Error::ExpectedNonZeroLength(robj.clone())),
            1 => {}
            _ => return Err(Error::ExpectedScalar(robj.clone())),
        };

        // Check if the value is not a missing value.
        if robj.is_na() {
            return Ok(Rcplx::na());
        }

        // This should always work, NA is handled above.
        if let Some(v) = robj.as_real() {
            return Ok(Rcplx::from(v));
        }

        // Any integer (32 bit) can be represented as f64,
        // this always works.
        if let Some(v) = robj.as_integer() {
            return Ok(Rcplx::from(v as f64));
        }

        // Complex slices return their first element.
        if let Some(s) = robj.as_typed_slice() {
            return Ok(s[0]);
        }

        Err(Error::ExpectedComplex(robj.clone()))
    }
}

// Convert TryFrom<&Robj> into TryFrom<Robj>. Sadly, we are unable to make a blanket
// conversion using GetSexp with the current version of Rust.
macro_rules! impl_try_from_robj {
    () => {};
    (&mut [$type:ty], $($rest:tt)*) => {
        impl_try_from_robj!(&mut [$type]);
        impl_try_from_robj!($($rest)*);
    };
    ($type:ty, $($rest:tt)*) => {
        impl_try_from_robj!($type);
        impl_try_from_robj!($($rest)*);
    };
    (&mut [$type:ty]) => {
        impl TryFrom<Robj> for &mut [$type] {
            type Error = Error;

            fn try_from(mut robj: Robj) -> Result<Self> {
                Self::try_from(&mut robj)
            }
        }

        impl TryFrom<&mut Robj> for Option<&mut [$type]> {
            type Error = Error;

            fn try_from(robj: &mut Robj) -> Result<Self> {
                if robj.is_null() || robj.is_na() {
                    Ok(None)
                } else {
                    Ok(Some(<&mut [$type]>::try_from(robj)?))
                }
            }
        }

        impl TryFrom<Robj> for Option<&mut [$type]> {
            type Error = Error;

            fn try_from(mut robj: Robj) -> Result<Self> {
                Self::try_from(&mut robj)
            }
        }
    };

    ($type:ty) => {
        impl TryFrom<Robj> for $type {
            type Error = Error;

            fn try_from(robj: Robj) -> Result<Self> {
                Self::try_from(&robj)
            }
        }

        impl TryFrom<&Robj> for Option<$type> {
            type Error = Error;

            fn try_from(robj: &Robj) -> Result<Self> {
                if robj.is_null() || robj.is_na() {
                    Ok(None)
                } else {
                    Ok(Some(<$type>::try_from(robj)?))
                }
            }
        }

        impl TryFrom<Robj> for Option<$type> {
            type Error = Error;

            fn try_from(robj: Robj) -> Result<Self> {
                Self::try_from(&robj)
            }
        }
    };
}

#[rustfmt::skip]
impl_try_from_robj!(
    u8, u16, u32, u64, usize,
    i8, i16, i32, i64, isize,
    bool,
    Rint, Rfloat, Rbool, Rcplx,
    f32, f64,
    Vec::<String>,
    HashMap::<String, Robj>, HashMap::<&str, Robj>,
    Vec::<Rint>, Vec::<Rfloat>, Vec::<Rbool>, Vec::<Rcplx>, Vec::<u8>, Vec::<i32>, Vec::<f64>,
    &[Rint], &[Rfloat], &[Rbool], &[Rcplx], &[u8], &[i32], &[f64],
    &mut [Rint], &mut [Rfloat], &mut [Rbool], &mut [Rcplx], &mut [u8], &mut [i32], &mut [f64],
    &str, String,
);

// NOTE: this is included for compatibility with previously defined `FromRobj`
// One should prefer `List::from_hashmap` instead,
// and this `impl` should be deprecated next.

impl TryFrom<&Robj> for HashMap<String, Robj> {
    type Error = Error;
    fn try_from(robj: &Robj) -> Result<Self> {
        Ok(robj
            .as_list()
            .map(|l| l.iter())
            .ok_or_else(|| Error::ExpectedList(robj.clone()))?
            .map(|(k, v)| (k.to_string(), v))
            .collect::<HashMap<String, Robj>>())
    }
}

impl TryFrom<&Robj> for HashMap<&str, Robj> {
    type Error = Error;
    fn try_from(robj: &Robj) -> Result<Self> {
        Ok(robj
            .as_list()
            .map(|l| l.iter())
            .ok_or_else(|| Error::ExpectedList(robj.clone()))?
            .collect::<HashMap<&str, Robj>>())
    }
}