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use super::{Evaluator, FlowControl, Scope, ScopeKind};
use crate::{
ast::Value,
ast::source::*,
error::{NbclError, Result},
};
impl Evaluator {
pub(crate) fn execute_stmt(&mut self, stmt: &Stmt) -> Result<Value> {
if let FlowControl::Return(val) = &self.flow {
return Ok(val.clone());
}
let result = match stmt {
Stmt::Expr(expr) => {
// Standalone expressions are evaluated and discarded
self.eval_expr(&expr)?
}
Stmt::Return(maybe_expr, span) => {
// Ensure that we cant return at:
// TopLevel or a Block child of TopLevel
let is_at_root = match self.scopes.as_slice() {
[root] if root.kind == ScopeKind::TopLevel => true,
[root, current]
if root.kind == ScopeKind::TopLevel && current.kind == ScopeKind::Block =>
{
true
}
_ => false,
};
if is_at_root {
return Err(NbclError::Runtime {
message: "cannot return from the top level".to_string(),
hint: Some("Move this logic into a function or component if you need early returns.".to_string()),
span: Some(span.clone()),
});
}
let val = match maybe_expr {
Some(e) => self.eval_expr(&e)?,
None => Value::Null,
};
self.flow = FlowControl::Return(val.clone());
val
}
// TODO: Use typehint in global and local
Stmt::Global(name, _type_hint, expr) => {
let val = self.eval_expr(&expr)?;
// A 'global' always goes into the very first scope (index 0),
// regardless of how many components or blocks deep we are.
if let Some(global_scope) = self.scopes.first_mut() {
global_scope.variables.insert(name.to_string(), val);
} else {
// Fallback: if somehow scopes is empty (shouldn't happen),
// create a new one.
let mut map = Scope::new(ScopeKind::TopLevel);
map.variables.insert(name.to_string(), val);
self.scopes.push(map);
}
Value::Null
}
Stmt::Local(name, _type_hint, expr) => {
let val = self.eval_expr(&expr)?;
if let Some(current_scope) = self.scopes.last_mut() {
current_scope.variables.insert(name.to_string(), val);
}
Value::Null
}
Stmt::Assign(lhs, rhs_expr, span) => {
let new_val = self.eval_expr(&rhs_expr)?;
match &lhs.kind {
ExprKind::Variable(name) => {
let mut found = false;
for scope in self.scopes.iter_mut().rev() {
if scope.variables.contains_key(name) {
scope.variables.insert(name.clone(), new_val);
found = true;
break;
}
}
if !found {
let candidates = self.scopes.iter().flat_map(|s| s.variables.keys());
let suggestion = crate::utils::find_best_match(&name, candidates);
let hint = suggestion.map(|s| format!("Did you mean \"{}\"?", s));
return Err(NbclError::Runtime {
message: format!("variable '{}' doesn't exist", name),
hint,
span: Some(span.clone()),
});
}
}
ExprKind::Field(base, field_name, _is_safe) => {
let mut target_map = self.eval_expr(&base)?;
if let Value::Map(ref mut entries) = target_map {
if let Some(pos) = entries.iter().position(|(k, _)| k == field_name) {
entries[pos].1 = new_val;
} else {
entries.push((field_name.clone(), new_val));
}
self.reassign_to_lhs(*base.clone(), target_map)?;
} else {
return Err(NbclError::Runtime {
message: "cannot set field on non-map".into(),
span: Some(span.clone()),
hint: None,
});
}
}
ExprKind::Index(base, index_expr) => {
let mut target_coll = self.eval_expr(&base)?;
let index_val = self.eval_expr(&index_expr)?;
match (&mut target_coll, index_val) {
(Value::List(items), Value::Int(i)) => {
let idx = i as usize;
if idx < items.len() {
items[idx] = new_val;
self.reassign_to_lhs(*base.clone(), target_coll)?;
} else {
return Err(NbclError::Runtime {
message: format!("index {} out of bounds", i),
span: Some(span.clone()),
hint: None,
});
}
}
_ => return Err(NbclError::Runtime {
message: "invalid index operation".into(),
span: Some(span.clone()),
hint: None,
}),
}
}
_ => return Err(NbclError::Runtime {
message: "invalid assignment target".into(),
span: Some(span.clone()),
hint: None,
}),
}
Value::Null
}
Stmt::For(patterns, iter_expr, body) => {
let iter_val = self.eval_expr(&iter_expr)?;
match iter_val {
Value::Range(start, end) => {
for i in start..end {
if let FlowControl::Return(_) = self.flow {
break;
}
let mut loop_scope = Scope::new(ScopeKind::Block);
let val_i = Value::Int(i);
if patterns.len() == 1 {
loop_scope.variables.insert(patterns[0].clone(), val_i);
} else if patterns.len() == 2 {
loop_scope.variables.insert(patterns[0].clone(), val_i.clone());
loop_scope.variables.insert(patterns[1].clone(), val_i);
}
self.scopes.push(loop_scope);
self.execute_block_internal(&body)?;
self.scopes.pop();
if let FlowControl::Return(_) = self.flow {
break;
}
}
}
Value::List(items) => {
for (i, item) in items.into_iter().enumerate() {
if let FlowControl::Return(_) = self.flow {
break;
}
let mut loop_scope = Scope::new(ScopeKind::Block);
// Handle pattern matching (len 1 or len 2)
if patterns.len() == 1 {
loop_scope.variables.insert(patterns[0].clone(), item);
} else if patterns.len() == 2 {
loop_scope.variables.insert(patterns[0].clone(), Value::Int(i as i64));
loop_scope.variables.insert(patterns[1].clone(), item);
}
self.scopes.push(loop_scope);
// Execute the block logic
self.execute_block_internal(&body)?;
self.scopes.pop();
if let FlowControl::Return(_) = self.flow {
break;
}
}
}
// unreachable
_ => {}
}
Value::Null
}
Stmt::While(condition_expr, body) => {
// Keep looping as long as the condition evaluates to truthy
// and we haven't hit a Return statement.
while self.eval_expr(&condition_expr)?.is_truthy() {
if let FlowControl::Return(_) = self.flow {
break;
}
self.scopes.push(Scope::new(ScopeKind::Block));
// Execute the block logic
self.execute_block_internal(&body)?;
self.scopes.pop();
if let FlowControl::Return(_) = self.flow {
break;
}
}
Value::Null
}
};
Ok(result)
}
/// Executes the statements in a block and evaluates the terminator if present.
fn execute_block_internal(&mut self, block: &Block) -> Result<Value> {
// Run all statements
for s in &block.stmts {
self.execute_stmt(s)?;
if let FlowControl::Return(_) = self.flow {
return Ok(Value::Null);
}
}
// Evaluate the implicit return (terminator) if it exists
if let Some(expr) = &block.terminator {
let val = self.eval_expr(expr)?;
return Ok(val);
}
Ok(Value::Null)
}
fn reassign_to_lhs(&mut self, lhs: Expr, value: Value) -> Result<()> {
match lhs.kind {
ExprKind::Variable(name) => {
for scope in self.scopes.iter_mut().rev() {
if scope.variables.contains_key(&name) {
scope.variables.insert(name, value);
return Ok(());
}
}
Err(NbclError::Runtime {
message: "Variable lost during assignment".into(),
hint: None,
span: None,
})
}
ExprKind::Field(base, field, _) => {
let mut parent = self.eval_expr(&base)?;
if let Value::Map(ref mut entries) = parent {
if let Some(pos) = entries.iter().position(|(k, _)| k == &field) {
entries[pos].1 = value;
} else {
entries.push((field, value));
}
self.reassign_to_lhs(*base, parent)
} else { Ok(()) }
}
ExprKind::Index(base, index_expr) => {
let mut parent = self.eval_expr(&base)?;
let idx_val = self.eval_expr(&index_expr)?;
if let (Value::List(items), Value::Int(i)) = (&mut parent, idx_val) {
let idx = i as usize;
if idx < items.len() {
items[idx] = value;
self.reassign_to_lhs(*base, parent)?;
}
}
Ok(())
}
_ => Ok(()),
}
}
}