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//! Cypher scalar functions — collection category. Split out of the monolithic
//! `evaluate_scalar_function` dispatcher; arms are verbatim. Routed from
//! `super::evaluate_scalar_function`; returns `Ok(None)` when `name` is not
//! one of this category's functions so the dispatcher tries the next.
use super::super::helpers::*;
use super::super::*;
use crate::datatypes::values::Value;
impl<'a> CypherExecutor<'a> {
pub(super) fn eval_collection_fn(
&self,
name: &str,
args: &[Expression],
row: &ResultRow,
) -> Result<Option<Value>, String> {
let result: Result<Value, String> = match name {
"size" => {
// Phase A.1 / C2 — native Value::List fast path;
// string fallback stays for legacy collect-as-JSON
// and parameter-passed lists.
let val = self.evaluate_expression(&args[0], row)?;
match val {
Value::List(items) => Ok(Value::Int64(items.len() as i64)),
Value::Map(m) => Ok(Value::Int64(m.len() as i64)),
Value::String(s) => {
if s.starts_with('[') && s.ends_with(']') {
let items = parse_list_value(&Value::String(s));
Ok(Value::Int64(items.len() as i64))
} else {
Ok(Value::Int64(s.len() as i64))
}
}
_ => Ok(Value::Null),
}
}
"length" => {
// length(p) for paths, length(s) for strings, length(list) for lists
if let Some(Expression::Variable(var)) = args.first() {
if let Some(path) = row.path_bindings.get(var) {
return Ok(Some(Value::Int64(path.hops as i64)));
}
}
let val = self.evaluate_expression(&args[0], row)?;
match val {
// Phase A.1 / C2 — native Value::List/Path/Map paths.
Value::List(items) => Ok(Value::Int64(items.len() as i64)),
Value::Map(m) => Ok(Value::Int64(m.len() as i64)),
Value::Path(p) => Ok(Value::Int64(p.rels.len() as i64)),
Value::String(s) => {
if s.starts_with('[') && s.ends_with(']') {
let items = parse_list_value(&Value::String(s));
Ok(Value::Int64(items.len() as i64))
} else {
Ok(Value::Int64(s.len() as i64))
}
}
_ => Ok(Value::Null),
}
}
"coalesce" => {
// coalesce(expr1, expr2, ...) returns first non-null
for arg in args {
let val = self.evaluate_expression(arg, row)?;
if !matches!(val, Value::Null) {
return Ok(Some(val));
}
}
Ok(Value::Null)
}
"reverse" => {
if args.len() != 1 {
return Err("reverse() requires 1 argument".into());
}
match self.evaluate_expression(&args[0], row)? {
// Cypher reverse() on a list reverses its elements.
Value::List(mut items) => {
items.reverse();
Ok(Value::List(items))
}
Value::Null => Ok(Value::Null),
other => {
let s = match coerce_to_string(other) {
Value::String(s) => s,
_ => return Ok(Some(Value::Null)),
};
let trimmed = s.trim();
if trimmed.starts_with('[') && trimmed.ends_with(']') {
// A bracketed string is a list, consistent with
// head/last/size (parse_list_value) — reverse elements.
let mut items = parse_list_value(&Value::String(s));
items.reverse();
Ok(Value::List(items))
} else {
// Otherwise reverse characters.
Ok(Value::String(s.chars().rev().collect()))
}
}
}
}
// ── List functions ────────────────────────────────────
"head" => {
if args.len() != 1 {
return Err("head() requires 1 argument".into());
}
let val = self.evaluate_expression(&args[0], row)?;
let items = parse_list_value(&val);
Ok(items.into_iter().next().unwrap_or(Value::Null))
}
"last" => {
if args.len() != 1 {
return Err("last() requires 1 argument".into());
}
let val = self.evaluate_expression(&args[0], row)?;
let items = parse_list_value(&val);
Ok(items.into_iter().last().unwrap_or(Value::Null))
}
// ── Spatial functions ─────────────────────────────────
"range" => {
if args.len() < 2 || args.len() > 3 {
return Err(
"range() requires 2 or 3 arguments: range(start, end[, step])".into(),
);
}
let start = as_i64(&self.evaluate_expression(&args[0], row)?)?;
let end = as_i64(&self.evaluate_expression(&args[1], row)?)?;
let step = if args.len() == 3 {
let s = as_i64(&self.evaluate_expression(&args[2], row)?)?;
if s == 0 {
return Err("range() step must not be zero".into());
}
s
} else {
1
};
// Preflight the inclusive cardinality in i128 so extrema and
// a negative step never overflow before allocation.
let len_i128 = if (step > 0 && start <= end) || (step < 0 && start >= end) {
let distance = if step > 0 {
i128::from(end) - i128::from(start)
} else {
i128::from(start) - i128::from(end)
};
let stride = i128::from(step).abs();
distance / stride + 1
} else {
0
};
let len = usize::try_from(len_i128)
.map_err(|_| "range() cardinality exceeds this platform's limits")?;
self.budget.check_work(len, "range()")?;
self.budget.consume_collection(len, "range()")?;
self.check_deadline()?;
const MAX_RANGE_ALLOCATION_BYTES: usize = 256 * 1024 * 1024;
let allocation_bytes = len
.checked_mul(std::mem::size_of::<Value>())
.ok_or("range() allocation size overflow")?;
if allocation_bytes > MAX_RANGE_ALLOCATION_BYTES {
return Err(format!(
"range() would materialize {len} items ({allocation_bytes} bytes), \
exceeding the 256 MiB collection safety limit"
));
}
// Phase A.1 / C4 — native Value::List of Value::Int64.
// `try_reserve_exact` turns impossible theoretical ranges into
// a query error instead of an aborting allocator request.
let mut vals: Vec<Value> = Vec::new();
vals.try_reserve_exact(len)
.map_err(|_| format!("range() cannot allocate {len} items"))?;
let mut cur = start;
for i in 0..len {
self.check_interrupt_periodic(i)?;
vals.push(Value::Int64(cur));
if i + 1 < len {
cur = cur
.checked_add(step)
.ok_or_else(|| "range() value overflow".to_string())?;
}
}
Ok(Value::List(vals))
}
// ── Numeric math functions ──────────────────────────
_ => return Ok(None),
};
result.map(Some)
}
}