use crate::de::rs_deserializer::RsDeserializer;
use crate::de::{DeserializableRow, DeserializationError, DeserializationResult};
use std::marker::Sized;
/// Interface for a database resultset to support deserialization.
pub trait DeserializableResultset: Sized {
/// Error type of the database driver.
type E: From<DeserializationError> + Sized;
/// Concrete type for the DB row, which must implement `DeserializabeRow`.
type ROW: DeserializableRow;
/// Returns true if more than one row is contained, including eventually not yet fetched rows.
///
/// # Errors
///
/// E.g. fetching can fail.
fn has_multiple_rows(&mut self) -> DeserializationResult<bool>;
/// Removes the next row and returns it, or None if the result set is empty, or an error.
///
/// # Errors
///
/// E.g. fetching can fail.
fn next(&mut self) -> DeserializationResult<Option<Self::ROW>>;
/// Returns the number of fields in each (complete) row.
fn number_of_fields(&self) -> usize;
/// Returns the name of the column at the specified index.
fn fieldname(&self, field_idx: usize) -> Option<&str>;
/// A _provided method_ that translates a resultset into a given rust type
/// that implements `serde::Deserialize`.
///
/// The type of the target variable needs to be specified explicitly, so that
/// `try_into()` can derive the type it needs to serialize into:
///
/// ```ignore
/// #[derive(Deserialize)]
/// struct MyStruct {
/// ...
/// }
/// let typed_result: Vec<MyStruct> = resultset.try_into()?;
/// ```
///
/// # Errors
///
/// An error is produced if deserialization into the target type is not possible,
/// or if fetching fails.
fn try_into<'de, T>(self) -> Result<T, Self::E>
where
T: serde::Deserialize<'de>,
{
#[cfg(feature = "trace")]
log::trace!("DeserializableResultset::try_into()");
Ok(serde::Deserialize::deserialize(
&mut RsDeserializer::try_new(self)?,
)?)
}
}