/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at
http://mozilla.org/MPL/2.0/. */
use std::{
fmt::Display,
ops::{Bound, RangeBounds},
};
use rusqlite::ToSql;
/// Formats a pair of range bounds as an SQL expression that
/// constrains the range of a projected column.
///
/// Depending on whether the range is bounded or unbounded in
/// either direction, the fragment can bind zero, one, or two
/// SQL parameters.
pub struct RangeFragment<'a, T> {
column: &'a str,
start: Bound<&'a T>,
end: Bound<&'a T>,
}
impl<'a, T> RangeFragment<'a, T>
where
T: ToSql,
{
/// If the range has a lower bound, returns the name and value of the
/// SQL parameter to add to the `[rusqlite::Params]` slice for the
/// statement containing this fragment.
pub fn start_param(&self) -> Option<(&'static str, &dyn ToSql)> {
match &self.start {
Bound::Included(key) | Bound::Excluded(key) => Some((":start", key)),
Bound::Unbounded => None,
}
}
/// If the range has an upper bound, returns the name and value of the
/// SQL parameter to add to the `[rusqlite::Params]` slice for the
/// statement containing this fragment.
pub fn end_param(&self) -> Option<(&'static str, &dyn ToSql)> {
match &self.end {
Bound::Included(key) | Bound::Excluded(key) => Some((":end", key)),
Bound::Unbounded => None,
}
}
}
impl<'a, T> RangeFragment<'a, T> {
pub fn new<R>(column: &'a str, range: &'a R) -> Self
where
R: RangeBounds<T>,
{
RangeFragment {
column,
start: range.start_bound(),
end: range.end_bound(),
}
}
}
impl<'a, T> Display for RangeFragment<'a, T> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match (&self.start, &self.end) {
(Bound::Unbounded, Bound::Unbounded) => {
// `1` is a no-op that's always true.
f.write_str("1")
}
(Bound::Unbounded, Bound::Included(_)) => write!(f, "({0} <= :end)", self.column),
(Bound::Unbounded, Bound::Excluded(_)) => write!(f, "({0} < :end)", self.column),
(Bound::Included(_), Bound::Unbounded) => write!(f, "({0} >= :start)", self.column),
(Bound::Included(_), Bound::Included(_)) => {
// `BETWEEN` is inclusive in SQL.
write!(f, "({0} BETWEEN :start AND :end)", self.column)
}
(Bound::Included(_), Bound::Excluded(_)) => {
write!(f, "({0} >= :start AND {0} < :end)", self.column)
}
(Bound::Excluded(_), Bound::Unbounded) => write!(f, "({0} > :start)", self.column),
(Bound::Excluded(_), Bound::Included(_)) => {
write!(f, "({0} > :start AND {0} <= :end)", self.column)
}
(Bound::Excluded(_), Bound::Excluded(_)) => {
write!(f, "({0} > :start AND {0} < :end)", self.column)
}
}
}
}
