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use super::{Null, Value, ValueRef};
use std::borrow::Cow;
#[cfg(feature = "array")]
use vtab::array::Array;
use Result;

/// `ToSqlOutput` represents the possible output types for implementors of the
/// `ToSql` trait.
#[derive(Clone, Debug, PartialEq)]
pub enum ToSqlOutput<'a> {
    /// A borrowed SQLite-representable value.
    Borrowed(ValueRef<'a>),

    /// An owned SQLite-representable value.
    Owned(Value),

    /// A BLOB of the given length that is filled with zeroes.
    #[cfg(feature = "blob")]
    ZeroBlob(i32),

    #[cfg(feature = "array")]
    Array(Array),
}

// Generically allow any type that can be converted into a ValueRef
// to be converted into a ToSqlOutput as well.
impl<'a, T: ?Sized> From<&'a T> for ToSqlOutput<'a>
where
    &'a T: Into<ValueRef<'a>>,
{
    fn from(t: &'a T) -> Self {
        ToSqlOutput::Borrowed(t.into())
    }
}

// We cannot also generically allow any type that can be converted
// into a Value to be converted into a ToSqlOutput because of
// coherence rules (https://github.com/rust-lang/rust/pull/46192),
// so we'll manually implement it for all the types we know can
// be converted into Values.
macro_rules! from_value(
    ($t:ty) => (
        impl<'a> From<$t> for ToSqlOutput<'a> {
            fn from(t: $t) -> Self { ToSqlOutput::Owned(t.into())}
        }
    )
);
from_value!(String);
from_value!(Null);
from_value!(bool);
from_value!(i8);
from_value!(i16);
from_value!(i32);
from_value!(i64);
from_value!(isize);
from_value!(u8);
from_value!(u16);
from_value!(u32);
from_value!(f64);
from_value!(Vec<u8>);

impl<'a> ToSql for ToSqlOutput<'a> {
    fn to_sql(&self) -> Result<ToSqlOutput> {
        Ok(match *self {
            ToSqlOutput::Borrowed(v) => ToSqlOutput::Borrowed(v),
            ToSqlOutput::Owned(ref v) => ToSqlOutput::Borrowed(ValueRef::from(v)),

            #[cfg(feature = "blob")]
            ToSqlOutput::ZeroBlob(i) => ToSqlOutput::ZeroBlob(i),
            #[cfg(feature = "array")]
            ToSqlOutput::Array(ref a) => ToSqlOutput::Array(a.clone()),
        })
    }
}

/// A trait for types that can be converted into SQLite values.
pub trait ToSql {
    fn to_sql(&self) -> Result<ToSqlOutput>;
}

// We should be able to use a generic impl like this:
//
// impl<T: Copy> ToSql for T where T: Into<Value> {
//     fn to_sql(&self) -> Result<ToSqlOutput> {
//         Ok(ToSqlOutput::from((*self).into()))
//     }
// }
//
// instead of the following macro, but this runs afoul of
// https://github.com/rust-lang/rust/issues/30191 and reports conflicting
// implementations even when there aren't any.

macro_rules! to_sql_self(
    ($t:ty) => (
        impl ToSql for $t {
            fn to_sql(&self) -> Result<ToSqlOutput> {
                Ok(ToSqlOutput::from(*self))
            }
        }
    )
);

to_sql_self!(Null);
to_sql_self!(bool);
to_sql_self!(i8);
to_sql_self!(i16);
to_sql_self!(i32);
to_sql_self!(i64);
to_sql_self!(isize);
to_sql_self!(u8);
to_sql_self!(u16);
to_sql_self!(u32);
to_sql_self!(f64);

impl<'a, T: ?Sized> ToSql for &'a T
where
    &'a T: Into<ToSqlOutput<'a>>,
{
    fn to_sql(&self) -> Result<ToSqlOutput> {
        Ok((*self).into())
    }
}

impl ToSql for String {
    fn to_sql(&self) -> Result<ToSqlOutput> {
        Ok(ToSqlOutput::from(self.as_str()))
    }
}

impl ToSql for str {
    fn to_sql(&self) -> Result<ToSqlOutput> {
        Ok(ToSqlOutput::from(self))
    }
}

impl ToSql for Vec<u8> {
    fn to_sql(&self) -> Result<ToSqlOutput> {
        Ok(ToSqlOutput::from(self.as_slice()))
    }
}

impl ToSql for [u8] {
    fn to_sql(&self) -> Result<ToSqlOutput> {
        Ok(ToSqlOutput::from(self))
    }
}

impl ToSql for Value {
    fn to_sql(&self) -> Result<ToSqlOutput> {
        Ok(ToSqlOutput::from(self))
    }
}

impl<T: ToSql> ToSql for Option<T> {
    fn to_sql(&self) -> Result<ToSqlOutput> {
        match *self {
            None => Ok(ToSqlOutput::from(Null)),
            Some(ref t) => t.to_sql(),
        }
    }
}

impl<'a> ToSql for Cow<'a, str> {
    fn to_sql(&self) -> Result<ToSqlOutput> {
        Ok(ToSqlOutput::from(self.as_ref()))
    }
}

#[cfg(test)]
mod test {
    use super::ToSql;

    fn is_to_sql<T: ToSql>() {}

    #[test]
    fn test_integral_types() {
        is_to_sql::<i8>();
        is_to_sql::<i16>();
        is_to_sql::<i32>();
        is_to_sql::<i64>();
        is_to_sql::<u8>();
        is_to_sql::<u16>();
        is_to_sql::<u32>();
    }

    #[test]
    fn test_cow_str() {
        use std::borrow::Cow;
        let s = "str";
        let cow = Cow::Borrowed(s);
        let r = cow.to_sql();
        assert!(r.is_ok());
        let cow = Cow::Owned::<str>(String::from(s));
        let r = cow.to_sql();
        assert!(r.is_ok());
    }
}