use std::cell::Cell;

use std::collections::BTreeMap;

/// Tracks fresh identifier generation during a single tree-building operation.

/// All occurrences of the same `$name` within one build share the same generated value.

pub struct FreshScope {

counter: Cell<u32>,

resolved: std::cell::RefCell<BTreeMap<String, String>>,

}

impl Default for FreshScope {

fn default() -> Self {

Self::new()

}

}

impl FreshScope {

pub fn new() -> Self {

Self {

counter: Cell::new(0),

resolved: std::cell::RefCell::new(BTreeMap::new()),

}

}

pub fn resolve(&self, name: &str) -> String {

self.resolved

.borrow_mut()

.entry(name.to_string())

.or_insert_with(|| {

let id = self.counter.get();

self.counter.set(id + 1);

format!("${name}-{id}")

})

.clone()

}

/// Clear resolved names but keep the counter. Called between rule

/// applications so that `$tmp` in different rules gets different values

/// while the counter increases monotonically.

pub fn next_scope(&self) {

self.resolved.borrow_mut().clear();

}

}