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use crate::ast::{BinaryOpKind as Op, Expr, Statement};
use crate::std as vexity_std;
use std::{collections::HashMap, fmt, sync::Arc};
/// A runtime value in the vex interpreter.
///
/// These variants are produced by evaluating expressions
/// and are used for storing variables, passing arguments,
/// and computation on the Rust side.
#[derive(Debug, Clone)]
pub enum VarValue {
/// A boolean value (true or false)
Bool(bool),
/// A UTF-8 string value.
///
/// # Example
/// ```ignore
/// "hello 🌍"
/// ```
String(String),
/// A 32-bit signed integer value.
///
/// # Examples
/// ```ignore
/// 1
/// 0
/// -1
/// ```
Int(i32),
/// A 64-bit floating-point number value.
///
/// # Examples
/// ```ignore
/// 3.14
/// 0.00
/// -3.14
/// ```
Float(f64),
/// A heterogeneous list of runtime values.
///
/// # Example
/// ```ignore
/// [1, 2.0, "foo", true]
/// ```
Array(Vec<VarValue>),
/// A mapping from string keys to runtime values.
///
/// # Example
/// ```ignore
/// { "x": 1, "y": 2.0, "label": "point" }
/// ```
HashMap(HashMap<String, VarValue>),
/// A one-argument anonymous function (lambda).
///
/// Lambdas capture a single parameter name and a block of statements.
/// They can be passed around and invoked via methods like `.map(...)`.
///
/// # Example
/// ```ignore
/// |x| x * 2
/// ```
Lambda { param: String, body: Vec<Statement> },
}
impl fmt::Display for VarValue {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
VarValue::Bool(b) => write!(f, "{}", b),
VarValue::String(s) => write!(f, "{}", s),
VarValue::Int(v) => write!(f, "{}", v),
VarValue::Float(v) => write!(f, "{}", v),
VarValue::Array(arr) => write!(f, "{:?}", arr),
VarValue::HashMap(map) => {
write!(f, "{{")?;
for (i, (k, v)) in map.iter().enumerate() {
write!(f, "{}: {}", k, v)?;
if i + 1 < map.len() {
write!(f, ", ")?;
}
}
write!(f, "}}")
}
VarValue::Lambda { param, body } => write!(f, "|{}| {:?}", param, body),
}
}
}
/// Represents a function
pub enum Func {
/// A native or "built in" vex function
Builtin(Arc<dyn Fn(Vec<VarValue>) -> VarValue + Send + Sync>),
/// A user defined "custom" function written in vex
Script {
params: Vec<String>,
body: Vec<Statement>,
},
}
impl Clone for Func {
fn clone(&self) -> Self {
match self {
Func::Builtin(f) => Func::Builtin(f.clone()),
Func::Script { params, body } => Func::Script {
params: params.clone(),
body: body.clone(),
},
}
}
}
/// The core interpreter state and scope.
///
/// Holds global variable bindings and registered functions
/// (both built-in and user-defined) used to evaluate and
/// execute parsed statements.
pub struct Interpreter {
/// A mapping of variable names to their current runtime values.
vars: HashMap<String, VarValue>,
/// A mapping of function names to their definitions.
funcs: HashMap<String, Func>,
}
impl Default for Interpreter {
/// Initialize a default Interpreter instance
fn default() -> Self {
Self::new()
}
}
impl Interpreter {
/// Create a new Interpreter instance
pub fn new() -> Self {
// Intialize the interpreter state with these built
// in functions from the Vexity standard library.
let funcs = HashMap::from([
("sma".into(), vexity_std::sma()),
("ema".into(), vexity_std::ema()),
("vwma".into(), vexity_std::vwma()),
("lsma".into(), vexity_std::lsma()),
]);
Interpreter {
vars: HashMap::new(),
funcs,
}
}
/// Execute a sequence of top level vex statements in order.
///
/// This serves as the main entry point for interpreting parsed programs.
/// It supports variable bindings, function calls, lambda definitions,
/// print statements, and user defined function registration.
pub fn run(&mut self, stmts: Vec<Statement>) {
for stmt in stmts {
match stmt {
Statement::LetExpression { name, value } => {
let val = self.eval_expr(value);
self.vars.insert(name, val);
}
Statement::Expression { value } => {
self.eval_expr(value);
}
Statement::Print { name } => {
let v = self
.vars
.get(&name)
.unwrap_or_else(|| panic!("Variable `{}` not found", name));
println!("{}", v);
}
Statement::Call { function, args } => {
let evaluated = args.into_iter().map(|e| self.eval_expr(e)).collect();
self.call_func(&function, evaluated);
}
Statement::FunctionDef { name, params, body } => {
self.funcs.insert(name, Func::Script { params, body });
}
}
}
}
/// Evaluate an expression in the global scope.
///
/// This method is used to evaluate all forms of expressions
/// supported by Vex, including literals, variables, arrays,
/// hash maps, field access, function calls, lambdas, method
/// calls, and binary operations.
fn eval_expr(&mut self, expr: Expr) -> VarValue {
match expr {
Expr::Boolean(b) => VarValue::Bool(b),
Expr::String(s) => VarValue::String(s),
Expr::Integer(i) => VarValue::Int(i),
Expr::Float(f) => VarValue::Float(f),
Expr::Array(items) => {
VarValue::Array(items.into_iter().map(|e| self.eval_expr(e)).collect())
}
Expr::HashMap(map) => VarValue::HashMap(
map.into_iter()
.map(|(k, v)| (k, self.eval_expr(v)))
.collect(),
),
Expr::Identifier(n) => self
.vars
.get(&n)
.cloned()
.unwrap_or_else(|| panic!("Variable `{}` not found", n)),
Expr::Field { target, name } => {
if let VarValue::HashMap(mut m) = self.eval_expr(*target) {
m.remove(&name)
.unwrap_or_else(|| panic!("key `{}` not found", name))
} else {
panic!("field access on non-hashmap")
}
}
Expr::BinaryOp { lhs, op, rhs } => {
let l = self.eval_expr(*lhs);
let r = self.eval_expr(*rhs);
self.eval_binary(l, op, r)
}
Expr::Lambda { param, body } => VarValue::Lambda { param, body },
Expr::Call { function, args } => {
let evaluated = args.into_iter().map(|e| self.eval_expr(e)).collect();
self.call_func(&function, evaluated)
}
Expr::MethodCall {
target,
method,
arg,
} => {
let tgt = self.eval_expr(*target);
self.eval_method_call(tgt, &method, *arg)
}
}
}
/// Evaluate binary numeric operations.
fn eval_binary(&self, l: VarValue, op: Op, r: VarValue) -> VarValue {
let (a, b) = match (l, r) {
(VarValue::Int(a), VarValue::Int(b)) => (a as f64, b as f64),
(VarValue::Int(a), VarValue::Float(b)) => (a as f64, b),
(VarValue::Float(a), VarValue::Int(b)) => (a, b as f64),
(VarValue::Float(a), VarValue::Float(b)) => (a, b),
(x, y) => panic!("Cannot apply {:?} to {:?} and {:?}", op, x, y),
};
let res = match op {
Op::Add => a + b,
Op::Sub => a - b,
Op::Mul => a * b,
Op::Div => a / b,
};
if res.fract() == 0.0 {
VarValue::Int(res as i32)
} else {
VarValue::Float(res)
}
}
/// Call a function by name.
fn call_func(&mut self, name: &str, args: Vec<VarValue>) -> VarValue {
let func = self
.funcs
.get(name)
.unwrap_or_else(|| panic!("unknown function `{}`", name))
.clone();
match func {
Func::Builtin(f) => f(args),
Func::Script { params, body } => {
if params.len() != args.len() {
panic!("{} expects {} args, got {}", name, params.len(), args.len());
}
let mut scope = self.vars.clone();
for (p, v) in params.into_iter().zip(args) {
scope.insert(p, v);
}
self.eval_statements_in_scope(&body, &mut scope)
}
}
}
/// Evaluate a sequence of statements in a lambda-local scope.
fn eval_statements_in_scope(
&mut self,
stmts: &[Statement],
scope: &mut HashMap<String, VarValue>,
) -> VarValue {
let mut last = VarValue::Float(0.0);
for stmt in stmts {
match stmt {
Statement::LetExpression { name, value } => {
let val = self.eval_expr_in_scope(value, scope);
scope.insert(name.clone(), val.clone());
last = val;
}
Statement::Expression { value } => {
last = self.eval_expr_in_scope(value, scope);
}
Statement::Call { function, args } => {
let evaluated = args
.iter()
.map(|e| self.eval_expr_in_scope(e, scope))
.collect();
last = self.call_func(function, evaluated);
}
Statement::Print { name } => {
let v = scope
.get(name)
.unwrap_or_else(|| panic!("Variable `{}` not in scope", name));
println!("{}", v);
}
Statement::FunctionDef { name, params, body } => {
self.funcs.insert(
name.clone(),
Func::Script {
params: params.clone(),
body: body.clone(),
},
);
last = VarValue::Float(0.0);
}
}
}
last
}
/// Helper to evaluate an expression with a given local scope.
fn eval_expr_in_scope(&mut self, expr: &Expr, scope: &HashMap<String, VarValue>) -> VarValue {
match expr {
Expr::Boolean(b) => VarValue::Bool(*b),
Expr::String(s) => VarValue::String(s.clone()),
Expr::Integer(i) => VarValue::Int(*i),
Expr::Float(f) => VarValue::Float(*f),
Expr::Array(items) => VarValue::Array(
items
.iter()
.map(|e| self.eval_expr_in_scope(e, scope))
.collect(),
),
Expr::HashMap(m) => VarValue::HashMap(
m.iter()
.map(|(k, v)| (k.clone(), self.eval_expr_in_scope(v, scope)))
.collect(),
),
Expr::Identifier(n) => scope
.get(n)
.cloned()
.or_else(|| self.vars.get(n).cloned())
.unwrap_or_else(|| panic!("unknown identifier `{}`", n)),
Expr::Field { target, name } => {
if let VarValue::HashMap(mut m) = self.eval_expr_in_scope(target, scope) {
m.remove(name)
.unwrap_or_else(|| panic!("key `{}` not found", name))
} else {
panic!("invalid field target");
}
}
Expr::BinaryOp { lhs, op, rhs } => {
let l = self.eval_expr_in_scope(lhs, scope);
let r = self.eval_expr_in_scope(rhs, scope);
self.eval_binary(l, op.clone(), r)
}
Expr::Lambda { param, body } => VarValue::Lambda {
param: param.clone(),
body: body.clone(),
},
Expr::Call { function, args } => {
let evaluated = args
.iter()
.map(|e| self.eval_expr_in_scope(e, scope))
.collect();
self.call_func(function, evaluated)
}
Expr::MethodCall {
target,
method,
arg,
} => {
let tgt = self.eval_expr_in_scope(target, scope);
self.eval_method_call(tgt, method, *arg.clone())
}
}
}
/// Handle array methods like `map` and `for_each`.
fn eval_method_call(&mut self, target: VarValue, method: &str, arg: Expr) -> VarValue {
match (target, method) {
(VarValue::Array(arr), "map") => {
let mapped = arr
.into_iter()
.map(|v| self.eval_lambda_callable(&arg, v))
.collect();
VarValue::Array(mapped)
}
(VarValue::Array(arr), "for_each") => {
for v in &arr {
let _ = self.eval_lambda_callable(&arg, v.clone());
}
// leave the array unchanged
VarValue::Array(arr)
}
(other, m) => panic!("Unsupported method '{}' on {:?}", m, other),
}
}
/// Evaluates a callable expression in the context of a lambda operation.
fn eval_lambda_callable(&mut self, callable: &Expr, input: VarValue) -> VarValue {
match callable {
Expr::Identifier(name) => self.call_func(name, vec![input]),
Expr::Lambda { param, body } => {
let mut temp = self.vars.clone();
temp.insert(param.clone(), input);
self.eval_statements_in_scope(body, &mut temp)
}
other => panic!("map expects a function name or lambda, got {:?}", other),
}
}
}