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use widestring::U16Str;

use crate::{
    fixed_sized::Pod,
    parameter::{InputParameter, VarBinaryBox, VarBinarySlice, VarCharBox, VarCharSlice, VarWCharSlice},
    Nullable, buffers::Indicator,
};

/// An instance can be consumed and to create a parameter which can be bound to a statement during
/// execution.
///
/// Due to specific layout requirements and the necessity to provide pointers to length and
/// indicator values, as opposed to taking the actual values it is often necessary starting from
/// idiomatic Rust types, to convert, enrich and marshal them into values which can be bound to
/// ODBC. This also provides a safe extension point for all kinds of parameters, as only the
/// implementation of `Parameters` is unsafe.
pub trait IntoParameter {
    type Parameter: InputParameter;

    fn into_parameter(self) -> Self::Parameter;
}

impl<T> IntoParameter for T
where
    T: InputParameter,
{
    type Parameter = Self;

    fn into_parameter(self) -> Self::Parameter {
        self
    }
}

impl<'a> IntoParameter for &'a str {
    type Parameter = VarCharSlice<'a>;

    fn into_parameter(self) -> Self::Parameter {
        VarCharSlice::new(self.as_bytes())
    }
}

impl<'a> IntoParameter for Option<&'a str> {
    type Parameter = VarCharSlice<'a>;

    fn into_parameter(self) -> Self::Parameter {
        match self {
            Some(str) => str.into_parameter(),
            None => VarCharSlice::NULL,
        }
    }
}

impl IntoParameter for String {
    type Parameter = VarCharBox;

    fn into_parameter(self) -> Self::Parameter {
        VarCharBox::from_string(self)
    }
}

impl IntoParameter for Option<String> {
    type Parameter = VarCharBox;

    fn into_parameter(self) -> Self::Parameter {
        match self {
            Some(str) => str.into_parameter(),
            None => VarCharBox::null(),
        }
    }
}

impl<'a> IntoParameter for &'a [u8] {
    type Parameter = VarBinarySlice<'a>;

    fn into_parameter(self) -> Self::Parameter {
        VarBinarySlice::new(self)
    }
}

impl<'a> IntoParameter for Option<&'a [u8]> {
    type Parameter = VarBinarySlice<'a>;

    fn into_parameter(self) -> Self::Parameter {
        match self {
            Some(str) => str.into_parameter(),
            None => VarBinarySlice::NULL,
        }
    }
}

impl IntoParameter for Vec<u8> {
    type Parameter = VarBinaryBox;

    fn into_parameter(self) -> Self::Parameter {
        VarBinaryBox::from_vec(self)
    }
}

impl IntoParameter for Option<Vec<u8>> {
    type Parameter = VarBinaryBox;

    fn into_parameter(self) -> Self::Parameter {
        match self {
            Some(str) => str.into_parameter(),
            None => VarBinaryBox::null(),
        }
    }
}

impl<'a> IntoParameter for &'a U16Str {
    type Parameter = VarWCharSlice<'a>;

    fn into_parameter(self) -> Self::Parameter {
        let slice = self.as_slice();
        let (_, bytes, _) = unsafe { slice.align_to::<u8>() };
        VarWCharSlice::from_buffer(bytes, Indicator::Length(bytes.len()))
    }
}

impl<'a> IntoParameter for Option<&'a U16Str> {
    type Parameter = VarWCharSlice<'a>;

    fn into_parameter(self) -> Self::Parameter {
        match self {
            Some(str) => str.into_parameter(),
            None => VarWCharSlice::NULL,
        }
    }
}

impl<T> IntoParameter for Option<T>
where
    T: Pod + InputParameter,
{
    type Parameter = Nullable<T>;

    fn into_parameter(self) -> Self::Parameter {
        match self {
            Some(value) => Nullable::new(value),
            None => Nullable::null(),
        }
    }
}