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// src/core/builder/join.rs
// Phase 5F: JOIN operations — inner_join, left_join, cross_join
use super::{QueryBuilder, QueryData};
use crate::core::state::Filtered;
use std::collections::HashMap;
use std::hash::Hash;
use std::marker::PhantomData;
impl<T: Clone + 'static, State> QueryBuilder<T, State> {
/// Join this sequence with `right` by matching keys, producing all
/// `(left, right)` pairs where `left_key(left) == right_key(right)`.
///
/// The right-hand side is **eagerly collected** into a `HashMap` before
/// iteration begins — O(M) space where M is the size of `right`.
/// The overall complexity is O(N + M).
///
/// ⚠ Right side is eagerly collected.
///
/// # Examples
///
/// ```rust
/// use rinq::QueryBuilder;
///
/// #[derive(Clone, Debug, PartialEq)]
/// struct User { id: u32, name: &'static str }
/// #[derive(Clone, Debug, PartialEq)]
/// struct Order { user_id: u32, amount: u32 }
///
/// let users = vec![User { id: 1, name: "Alice" }, User { id: 2, name: "Bob" }];
/// let orders = vec![Order { user_id: 1, amount: 100 }, Order { user_id: 1, amount: 200 }];
///
/// let mut result: Vec<(&str, u32)> = QueryBuilder::from(users)
/// .inner_join(orders, |u| u.id, |o| o.user_id)
/// .select(|(u, o)| (u.name, o.amount))
/// .collect();
/// result.sort_by_key(|&(_, a)| a);
/// assert_eq!(result, vec![("Alice", 100), ("Alice", 200)]);
/// ```
pub fn inner_join<U, K, FK, FU>(
self,
right: impl IntoIterator<Item = U> + 'static,
left_key: FK,
right_key: FU,
) -> QueryBuilder<(T, U), Filtered>
where
FK: Fn(&T) -> K + 'static,
FU: Fn(&U) -> K + 'static,
K: Hash + Eq + 'static,
U: Clone + 'static,
{
// Eagerly build the right-side lookup map.
let mut right_map: HashMap<K, Vec<U>> = HashMap::new();
for item in right {
let key = right_key(&item);
right_map.entry(key).or_default().push(item);
}
let left_iter: Box<dyn Iterator<Item = T>> = match self.data {
QueryData::Iterator(it) => it,
QueryData::SortedVec { items, .. } => Box::new(items.into_iter()),
};
let result = left_iter.flat_map(move |left| {
let key = left_key(&left);
match right_map.get(&key) {
Some(rights) => rights
.iter()
.map(|r| (left.clone(), r.clone()))
.collect::<Vec<_>>(),
None => vec![],
}
});
QueryBuilder {
data: QueryData::Iterator(Box::new(result)),
_state: PhantomData,
}
}
/// Left join: for each left element, emit `(left, Some(right))` for every
/// match, or `(left, None)` if no right element matched.
///
/// ⚠ Right side is eagerly collected.
///
/// # Examples
///
/// ```rust
/// use rinq::QueryBuilder;
///
/// #[derive(Clone, Debug)]
/// struct User { id: u32, name: &'static str }
/// #[derive(Clone, Debug)]
/// struct Order { user_id: u32, amount: u32 }
///
/// let users = vec![User { id: 1, name: "Alice" }, User { id: 2, name: "Bob" }];
/// let orders = vec![Order { user_id: 1, amount: 50 }];
///
/// let result: Vec<(&str, Option<u32>)> = QueryBuilder::from(users)
/// .left_join(orders, |u| u.id, |o| o.user_id)
/// .select(|(u, o)| (u.name, o.map(|x| x.amount)))
/// .collect();
///
/// assert_eq!(result[0], ("Alice", Some(50)));
/// assert_eq!(result[1], ("Bob", None));
/// ```
pub fn left_join<U, K, FK, FU>(
self,
right: impl IntoIterator<Item = U> + 'static,
left_key: FK,
right_key: FU,
) -> QueryBuilder<(T, Option<U>), Filtered>
where
FK: Fn(&T) -> K + 'static,
FU: Fn(&U) -> K + 'static,
K: Hash + Eq + 'static,
U: Clone + 'static,
{
let mut right_map: HashMap<K, Vec<U>> = HashMap::new();
for item in right {
let key = right_key(&item);
right_map.entry(key).or_default().push(item);
}
let left_iter: Box<dyn Iterator<Item = T>> = match self.data {
QueryData::Iterator(it) => it,
QueryData::SortedVec { items, .. } => Box::new(items.into_iter()),
};
let result = left_iter.flat_map(move |left| {
let key = left_key(&left);
match right_map.get(&key) {
Some(rights) => rights
.iter()
.map(|r| (left.clone(), Some(r.clone())))
.collect::<Vec<_>>(),
None => vec![(left, None)],
}
});
QueryBuilder {
data: QueryData::Iterator(Box::new(result)),
_state: PhantomData,
}
}
/// Cross join (Cartesian product): emit every `(left, right)` combination.
///
/// ⚠ O(N×M) — use with caution on large collections.
/// Right side is eagerly collected into a `Vec`.
///
/// # Examples
///
/// ```rust
/// use rinq::QueryBuilder;
///
/// let mut result: Vec<(i32, i32)> = QueryBuilder::from(vec![1, 2])
/// .cross_join(vec![10, 20, 30])
/// .collect();
/// assert_eq!(result.len(), 6);
/// assert_eq!(result[0], (1, 10));
/// assert_eq!(result[5], (2, 30));
/// ```
pub fn cross_join<U>(
self,
right: impl IntoIterator<Item = U> + 'static,
) -> QueryBuilder<(T, U), Filtered>
where
U: Clone + 'static,
{
let right_vec: Vec<U> = right.into_iter().collect();
let left_iter: Box<dyn Iterator<Item = T>> = match self.data {
QueryData::Iterator(it) => it,
QueryData::SortedVec { items, .. } => Box::new(items.into_iter()),
};
let result = left_iter.flat_map(move |left| {
right_vec
.iter()
.map(|r| (left.clone(), r.clone()))
.collect::<Vec<_>>()
});
QueryBuilder {
data: QueryData::Iterator(Box::new(result)),
_state: PhantomData,
}
}
}