use crate::ast::*;
use crate::lexer::{Token, TokenKind};
use crate::error::RuntimeError;

pub struct Parser {
    tokens: Vec<Token>,
    current: usize,
}

impl Parser {
    pub fn new(tokens: Vec<Token>) -> Self {
        Self { tokens, current: 0 }
    }

    pub fn parse(&mut self) -> (Vec<Stmt>, Vec<RuntimeError>) {
        let mut statements = Vec::new();
        let mut errors = Vec::new();

        while !self.is_at_end() {
            match self.declaration() {
                Ok(stmt) => statements.push(stmt),
                Err(err) => {
                    errors.push(err);
                    self.synchronize();
                }
            }
        }

        (statements, errors)
    }

    fn declaration(&mut self) -> Result<Stmt, RuntimeError> {
        if self.match_kind(&[TokenKind::Let]) {
            self.let_declaration(true)
        } else if self.match_kind(&[TokenKind::Const]) {
            self.let_declaration(false)
        } else if self.match_kind(&[TokenKind::Fn]) {
            self.fn_declaration()
        } else {
            self.statement()
        }
    }

    fn statement(&mut self) -> Result<Stmt, RuntimeError> {
        if self.match_kind(&[TokenKind::If]) {
            self.if_statement()
        } else if self.match_kind(&[TokenKind::While]) {
            self.while_statement()
        } else if self.match_kind(&[TokenKind::For]) {
            self.for_statement()
        } else if self.match_kind(&[TokenKind::Break]) {
            self.break_statement()
        } else if self.match_kind(&[TokenKind::Continue]) {
            self.continue_statement()
        } else if self.match_kind(&[TokenKind::Return]) {
            self.return_statement()
        } else if self.match_kind(&[TokenKind::LeftBrace]) {
            Ok(Stmt::Block(self.block()?))
        } else {
            self.expression_statement()
        }
    }

    fn let_declaration(&mut self, mutable: bool) -> Result<Stmt, RuntimeError> {
        let name = self.consume_ident("Expected variable name.")?;
        self.consume(TokenKind::Equal, "Expected '=' after variable name.")?;
        let initializer = self.expression()?;
        self.match_kind(&[TokenKind::Semicolon]); // 分号可选

        Ok(Stmt::Let { name, initializer, mutable })
    }

    fn fn_declaration(&mut self) -> Result<Stmt, RuntimeError> {
        let name = self.consume_ident("Expected function name.")?;
        self.consume(TokenKind::LeftParen, "Expected '(' after function name.")?;

        let mut params = Vec::new();
        if !self.check(&TokenKind::RightParen) {
            loop {
                params.push(self.consume_ident("Expected parameter name.")?);
                if !self.match_kind(&[TokenKind::Comma]) {
                    break;
                }
            }
        }

        self.consume(TokenKind::RightParen, "Expected ')' after parameters.")?;
        self.consume(TokenKind::LeftBrace, "Expected '{' before function body.")?;
        let body = self.block()?;

        Ok(Stmt::Function { name, params, body })
    }

    fn lambda_expr(&mut self) -> Result<Expr, RuntimeError> {
        self.consume(TokenKind::LeftParen, "Expected '(' after 'fn'.")?;
        let mut params = Vec::new();
        if !self.check(&TokenKind::RightParen) {
            loop {
                params.push(self.consume_ident("Expected parameter name.")?);
                if !self.match_kind(&[TokenKind::Comma]) {
                    break;
                }
            }
        }
        self.consume(TokenKind::RightParen, "Expected ')' after parameters.")?;
        self.consume(TokenKind::LeftBrace, "Expected '{' before function body.")?;
        let body = self.block()?;
        Ok(Expr::Lambda { params, body })
    }

    fn if_statement(&mut self) -> Result<Stmt, RuntimeError> {
        self.consume(TokenKind::LeftParen, "Expected '(' after 'if'.")?;
        let condition = self.expression()?;
        self.consume(TokenKind::RightParen, "Expected ')' after condition.")?;

        let then_branch = Box::new(self.statement()?);
        let else_branch = if self.match_kind(&[TokenKind::Else]) {
            Some(Box::new(self.statement()?))
        } else {
            None
        };

        Ok(Stmt::If { condition, then_branch, else_branch })
    }

    fn while_statement(&mut self) -> Result<Stmt, RuntimeError> {
        self.consume(TokenKind::LeftParen, "Expected '(' after 'while'.")?;
        let condition = self.expression()?;
        self.consume(TokenKind::RightParen, "Expected ')' after condition.")?;

        let body = Box::new(self.statement()?);
        Ok(Stmt::While { condition, body })
    }

    fn for_statement(&mut self) -> Result<Stmt, RuntimeError> {
        self.consume(TokenKind::LeftParen, "Expected '(' after 'for'.")?;

        // Detect for-in: for (Identifier in expr) body
        if let TokenKind::Identifier(var_name) = &self.peek().kind {
            let var_name = var_name.clone();
            if matches!(self.peek_next().kind, TokenKind::In) {
                self.advance(); // consume identifier
                self.advance(); // consume 'in'
                let iterable = self.expression()?;
                self.consume(TokenKind::RightParen, "Expected ')' after for-in expression.")?;
                let body = Box::new(self.statement()?);
                return Ok(Stmt::ForIn { var_name, iterable, body });
            }
        }

        let initializer = if self.match_kind(&[TokenKind::Semicolon]) {
            None
        } else if self.match_kind(&[TokenKind::Let]) {
            Some(self.let_declaration(true)?)
        } else {
            Some(self.expression_statement()?)
        };

        let condition = if !self.check(&TokenKind::Semicolon) {
            Some(self.expression()?)
        } else {
            None
        };

        self.consume(TokenKind::Semicolon, "Expected ';' after loop condition.")?;
        let step = if !self.check(&TokenKind::RightParen) {
            Some(self.expression()?)
        } else {
            None
        };

        self.consume(TokenKind::RightParen, "Expected ')' after for clauses.")?;
        let body = Box::new(self.statement()?);

        Ok(Stmt::For {
            initializer: initializer.map(Box::new),
            condition,
            step,
            body
        })
    }

    fn break_statement(&mut self) -> Result<Stmt, RuntimeError> {
        self.match_kind(&[TokenKind::Semicolon]); // 分号可选
        Ok(Stmt::Break)
    }

    fn continue_statement(&mut self) -> Result<Stmt, RuntimeError> {
        self.match_kind(&[TokenKind::Semicolon]); // 分号可选
        Ok(Stmt::Continue)
    }

    fn return_statement(&mut self) -> Result<Stmt, RuntimeError> {
        let value = if !self.check(&TokenKind::Semicolon) && !self.check(&TokenKind::RightBrace) {
            Some(self.expression()?)
        } else {
            None
        };

        self.match_kind(&[TokenKind::Semicolon]); // 分号可选
        Ok(Stmt::Return(value))
    }

    fn block(&mut self) -> Result<Vec<Stmt>, RuntimeError> {
        let mut statements = Vec::new();

        while !self.check(&TokenKind::RightBrace) && !self.is_at_end() {
            statements.push(self.declaration()?);
        }

        self.consume(TokenKind::RightBrace, "Expected '}' after block.")?;
        Ok(statements)
    }

    fn expression_statement(&mut self) -> Result<Stmt, RuntimeError> {
        let expr = self.expression()?;
        self.match_kind(&[TokenKind::Semicolon]); // 分号可选
        Ok(Stmt::ExprStmt(expr))
    }

    fn expression(&mut self) -> Result<Expr, RuntimeError> {
        self.assignment()
    }

    fn ternary(&mut self) -> Result<Expr, RuntimeError> {
        let expr = self.logical_or()?;
        if self.match_kind(&[TokenKind::Question]) {
            let then_branch = self.assignment()?;
            self.consume(TokenKind::Colon, "Expected ':' after then branch of ternary.")?;
            let else_branch = self.assignment()?;
            Ok(Expr::Ternary {
                condition: Box::new(expr),
                then_branch: Box::new(then_branch),
                else_branch: Box::new(else_branch),
            })
        } else {
            Ok(expr)
        }
    }

    fn assignment(&mut self) -> Result<Expr, RuntimeError> {
        let expr = self.ternary()?;

        let op = if self.match_kind(&[TokenKind::Equal]) {
            Some(AssignOp::Equal)
        } else if self.match_kind(&[TokenKind::PlusEqual]) {
            Some(AssignOp::PlusEqual)
        } else if self.match_kind(&[TokenKind::MinusEqual]) {
            Some(AssignOp::MinusEqual)
        } else if self.match_kind(&[TokenKind::StarEqual]) {
            Some(AssignOp::StarEqual)
        } else if self.match_kind(&[TokenKind::SlashEqual]) {
            Some(AssignOp::SlashEqual)
        } else if self.match_kind(&[TokenKind::PercentEqual]) {
            Some(AssignOp::PercentEqual)
        } else {
            None
        };

        if let Some(op) = op {
            let value = self.assignment()?;
            return match expr {
                Expr::Variable(name) => Ok(Expr::Assign { name, op, value: Box::new(value) }),
                Expr::Get { object, name } => Ok(Expr::Set { object, name, op, value: Box::new(value) }),
                Expr::IndexGet { array, index } => Ok(Expr::IndexSet { array, index, op, value: Box::new(value) }),
                _ => Err(RuntimeError::parse("Invalid assignment target.", self.previous().clone())),
            };
        }

        Ok(expr)
    }

    fn logical_or(&mut self) -> Result<Expr, RuntimeError> {
        let mut expr = self.logical_and()?;

        while self.match_kind(&[TokenKind::OrOr]) {
            let right = self.logical_and()?;
            expr = Expr::Logical {
                left: Box::new(expr),
                op: LogicalOp::Or,
                right: Box::new(right),
            };
        }

        Ok(expr)
    }

    fn logical_and(&mut self) -> Result<Expr, RuntimeError> {
        let mut expr = self.equality()?;

        while self.match_kind(&[TokenKind::AndAnd]) {
            let right = self.equality()?;
            expr = Expr::Logical {
                left: Box::new(expr),
                op: LogicalOp::And,
                right: Box::new(right),
            };
        }

        Ok(expr)
    }

    fn equality(&mut self) -> Result<Expr, RuntimeError> {
        let mut expr = self.comparison()?;

        while self.match_kind(&[TokenKind::EqualEqual, TokenKind::BangEqual]) {
            let op = match self.previous().kind {
                TokenKind::EqualEqual => BinaryOp::Equal,
                TokenKind::BangEqual => BinaryOp::NotEqual,
                _ => unreachable!(),
            };
            let right = self.comparison()?;
            expr = Expr::Binary {
                left: Box::new(expr),
                op,
                right: Box::new(right),
            };
        }

        Ok(expr)
    }

    fn comparison(&mut self) -> Result<Expr, RuntimeError> {
        let mut expr = self.term()?;

        while self.match_kind(&[TokenKind::Greater, TokenKind::GreaterEqual, TokenKind::Less, TokenKind::LessEqual]) {
            let op = match self.previous().kind {
                TokenKind::Greater => BinaryOp::Greater,
                TokenKind::GreaterEqual => BinaryOp::GreaterEqual,
                TokenKind::Less => BinaryOp::Less,
                TokenKind::LessEqual => BinaryOp::LessEqual,
                _ => unreachable!(),
            };
            let right = self.term()?;
            expr = Expr::Binary {
                left: Box::new(expr),
                op,
                right: Box::new(right),
            };
        }

        Ok(expr)
    }

    fn term(&mut self) -> Result<Expr, RuntimeError> {
        let mut expr = self.factor()?;

        while self.match_kind(&[TokenKind::Plus, TokenKind::Minus]) {
            let op = match self.previous().kind {
                TokenKind::Plus => BinaryOp::Add,
                TokenKind::Minus => BinaryOp::Sub,
                _ => unreachable!(),
            };
            let right = self.factor()?;
            expr = Expr::Binary {
                left: Box::new(expr),
                op,
                right: Box::new(right),
            };
        }

        Ok(expr)
    }

    fn factor(&mut self) -> Result<Expr, RuntimeError> {
        let mut expr = self.unary()?;

        while self.match_kind(&[TokenKind::Star, TokenKind::Slash, TokenKind::Percent]) {
            let op = match self.previous().kind {
                TokenKind::Star => BinaryOp::Mul,
                TokenKind::Slash => BinaryOp::Div,
                TokenKind::Percent => BinaryOp::Mod,
                _ => unreachable!(),
            };
            let right = self.unary()?;
            expr = Expr::Binary {
                left: Box::new(expr),
                op,
                right: Box::new(right),
            };
        }

        Ok(expr)
    }

    fn unary(&mut self) -> Result<Expr, RuntimeError> {
        if self.match_kind(&[TokenKind::Bang, TokenKind::Minus]) {
            let op = match self.previous().kind {
                TokenKind::Bang => UnaryOp::Not,
                TokenKind::Minus => UnaryOp::Negate,
                _ => unreachable!(),
            };
            let right = self.unary()?;
            return Ok(Expr::Unary {
                op,
                right: Box::new(right),
            });
        }

        self.call()
    }

    fn call(&mut self) -> Result<Expr, RuntimeError> {
        let mut expr = self.primary()?;

        loop {
            if self.match_kind(&[TokenKind::LeftParen]) {
                let mut arguments = Vec::new();
                if !self.check(&TokenKind::RightParen) {
                    loop {
                        arguments.push(self.expression()?);
                        if !self.match_kind(&[TokenKind::Comma]) {
                            break;
                        }
                    }
                }
                self.consume(TokenKind::RightParen, "Expected ')' after arguments.")?;
                expr = Expr::Call {
                    callee: Box::new(expr),
                    arguments,
                };
            } else if self.match_kind(&[TokenKind::Dot]) {
                let name = self.consume_ident("Expected property name after '.'.")?;
                expr = Expr::Get {
                    object: Box::new(expr),
                    name,
                };
            } else if self.match_kind(&[TokenKind::LeftBracket]) {
                let index = self.expression()?;
                self.consume(TokenKind::RightBracket, "Expected ']' after index.")?;
                expr = Expr::IndexGet {
                    array: Box::new(expr),
                    index: Box::new(index),
                };
            } else {
                break;
            }
        }

        Ok(expr)
    }

    fn primary(&mut self) -> Result<Expr, RuntimeError> {
        // 布尔值
        if self.match_kind(&[TokenKind::True]) {
            return Ok(Expr::Literal(Literal::Bool(true)));
        }
        if self.match_kind(&[TokenKind::False]) {
            return Ok(Expr::Literal(Literal::Bool(false)));
        }
        if self.match_kind(&[TokenKind::Nil]) {
            return Ok(Expr::Literal(Literal::Nil));
        }

        // 数字
        if let TokenKind::Number(n) = self.peek().kind {
            self.advance();
            return Ok(Expr::Literal(Literal::Number(n)));
        }

        // 字符串
        if let TokenKind::String(s) = &self.peek().kind {
            let s = s.clone();
            self.advance();
            return Ok(Expr::Literal(Literal::String(s)));
        }

        // 标识符（变量）
        if let TokenKind::Identifier(name) = &self.peek().kind {
            let name = name.clone();
            self.advance();
            return Ok(Expr::Variable(name));
        }

        // 匿名函数（闭包）: fn(params) { body }
        if self.match_kind(&[TokenKind::Fn]) {
            return self.lambda_expr();
        }

        // 括号表达式
        if self.match_kind(&[TokenKind::LeftParen]) {
            let expr = self.expression()?;
            self.consume(TokenKind::RightParen, "Expected ')' after expression.")?;
            return Ok(expr);
        }

        if self.match_kind(&[TokenKind::LeftBrace]) {
            return self.object_literal();
        }

        if self.match_kind(&[TokenKind::LeftBracket]) {
            return self.array_literal();
        }

        Err(RuntimeError::parse("Expected expression.", self.peek().clone()))
    }

    fn match_kind(&mut self, kinds: &[TokenKind]) -> bool {
        for kind in kinds {
            if self.check(kind) {
                self.advance();
                return true;
            }
        }
        false
    }

    fn consume(&mut self, kind: TokenKind, msg: &str) -> Result<(), RuntimeError> {
        if self.check(&kind) {
            self.advance();
            Ok(())
        } else {
            Err(RuntimeError::parse(msg, self.peek().clone()))
        }
    }

    fn consume_ident(&mut self, msg: &str) -> Result<String, RuntimeError> {
        match &self.peek().kind {
            TokenKind::Identifier(name) => {
                let name = name.clone();
                self.advance();
                Ok(name)
            }
            _ => Err(RuntimeError::parse(msg, self.peek().clone())),
        }
    }

    fn check(&self, kind: &TokenKind) -> bool {
        if self.is_at_end() {
            return false;
        }
        std::mem::discriminant(&self.peek().kind)
            == std::mem::discriminant(kind)
    }

    fn advance(&mut self) -> &Token {
        if !self.is_at_end() {
            self.current += 1;
        }
        self.previous()
    }

    fn is_at_end(&self) -> bool {
        matches!(self.peek().kind, TokenKind::EOF)
    }

    fn peek(&self) -> &Token {
        &self.tokens[self.current]
    }

    fn peek_next(&self) -> &Token {
        &self.tokens[self.current + 1]
    }

    fn previous(&self) -> &Token {
        &self.tokens[self.current - 1]
    }

    fn object_literal(&mut self) -> Result<Expr, RuntimeError> {
        let mut properties = Vec::new();
        if !self.check(&TokenKind::RightBrace) {
            loop {
                let name = self.consume_ident("Expected property name in object literal")?;
                self.consume(TokenKind::Colon, "Expected ':' after property name in object literal")?;
                let value = self.expression()?;
                properties.push((name, value));
                if !self.match_kind(&[TokenKind::Comma]) {
                    break;
                }
            }
        }
        self.consume(TokenKind::RightBrace, "Expected '}' after object literal")?;
        Ok(Expr::ObjectLiteral { properties })
    }

    fn array_literal(&mut self) -> Result<Expr, RuntimeError> {
        let mut elements = Vec::new();
        if !self.check(&TokenKind::RightBracket) {
            loop {
                elements.push(self.expression()?);
                if !self.match_kind(&[TokenKind::Comma]) {
                    break;
                }
            }
        }
        self.consume(TokenKind::RightBracket, "Expected ']' after array literal")?;
        Ok(Expr::ArrayLiteral { elements })
    }

    fn synchronize(&mut self) {
        // Always consume at least one token to guarantee forward progress,
        // preventing infinite loops when previous() is already a semicolon.
        if !self.is_at_end() {
            self.advance();
        }

        while !self.is_at_end() {
            if self.current > 0 && matches!(self.previous().kind, TokenKind::Semicolon) {
                return;
            }

            match self.peek().kind {
                TokenKind::Let
                | TokenKind::Const
                | TokenKind::Fn
                | TokenKind::If
                | TokenKind::While
                | TokenKind::For
                | TokenKind::Return
                | TokenKind::Break
                | TokenKind::Continue => return,
                _ => {
                    self.advance();
                }
            }
        }
    }
}

// ========================================================================
// Tests
// ========================================================================

#[cfg(test)]
mod tests {
        use super::*;
        use crate::lexer::Lexer;

        /// Helper: lex + parse, return (stmts, errors).
        fn parse(input: &str) -> (Vec<Stmt>, Vec<RuntimeError>) {
            let (tokens, _) = Lexer::new(input).tokenize();
            Parser::new(tokens).parse()
        }

        /// Helper: lex + parse single expression (wraps in `let _ = <expr>;`).
        fn parse_expr(input: &str) -> Expr {
            let (stmts, errors) = parse(&format!("let __x = {};", input));
            assert!(errors.is_empty(), "Parse errors: {:?}", errors);
            match &stmts[0] {
                Stmt::Let { initializer, .. } => initializer.clone(),
                _ => panic!("Expected Let statement"),
            }
        }

        /// Helper: lex + parse single statement.
        fn parse_stmt(input: &str) -> Stmt {
            let (stmts, errors) = parse(input);
            assert!(errors.is_empty(), "Parse errors: {:?}", errors);
            assert_eq!(stmts.len(), 1);
            stmts[0].clone()
        }

        // ----- literals -----

        #[test]
        fn parse_number() {
            match parse_expr("42") {
                Expr::Literal(Literal::Number(42.0)) => {}
                e => panic!("Expected Number(42.0), got {:?}", e),
            }
        }

        #[test]
        fn parse_float() {
            match parse_expr("3.14") {
                Expr::Literal(Literal::Number(n)) => assert!((n - 3.14).abs() < 0.001),
                e => panic!("Expected Number, got {:?}", e),
            }
        }

        #[test]
        fn parse_string() {
            match parse_expr("\"hello\"") {
                Expr::Literal(Literal::String(s)) => assert_eq!(s, "hello"),
                e => panic!("Expected String, got {:?}", e),
            }
        }

        #[test]
        fn parse_bool_true() {
            match parse_expr("true") {
                Expr::Literal(Literal::Bool(true)) => {}
                e => panic!("Expected Bool(true), got {:?}", e),
            }
        }

        #[test]
        fn parse_bool_false() {
            match parse_expr("false") {
                Expr::Literal(Literal::Bool(false)) => {}
                e => panic!("Expected Bool(false), got {:?}", e),
            }
        }

        #[test]
        fn parse_nil() {
            match parse_expr("nil") {
                Expr::Literal(Literal::Nil) => {}
                e => panic!("Expected Nil, got {:?}", e),
            }
        }

        // ----- variables -----

        #[test]
        fn parse_variable() {
            match parse_expr("x") {
                Expr::Variable(name) => assert_eq!(name, "x"),
                e => panic!("Expected Variable, got {:?}", e),
            }
        }

        // ----- unary -----

        #[test]
        fn parse_negation() {
            match parse_expr("-5") {
                Expr::Unary { op: UnaryOp::Negate, right } => {
                    match *right {
                        Expr::Literal(Literal::Number(5.0)) => {}
                        e => panic!("Expected Number(5), got {:?}", e),
                    }
                }
                e => panic!("Expected Unary(Negate, Number), got {:?}", e),
            }
        }

        #[test]
        fn parse_not() {
            match parse_expr("!true") {
                Expr::Unary { op: UnaryOp::Not, right } => {
                    match *right {
                        Expr::Literal(Literal::Bool(true)) => {}
                        e => panic!("Expected Bool(true), got {:?}", e),
                    }
                }
                e => panic!("Expected Unary(Not, Bool), got {:?}", e),
            }
        }

        #[test]
        fn parse_double_negation() {
            match parse_expr("!!true") {
                Expr::Unary { op: UnaryOp::Not, right } => {
                    match *right {
                        Expr::Unary { op: UnaryOp::Not, .. } => {}
                        e => panic!("Expected nested Unary, got {:?}", e),
                    }
                }
                e => panic!("Expected Unary(Not, ...), got {:?}", e),
            }
        }

        // ----- binary precedence -----

        #[test]
        fn parse_addition() {
            match parse_expr("1 + 2") {
                Expr::Binary { op: BinaryOp::Add, left, right } => {
                    match (*left, *right) {
                        (Expr::Literal(Literal::Number(1.0)), Expr::Literal(Literal::Number(2.0))) => {}
                        e => panic!("Expected (1, 2), got {:?}", e),
                    }
                }
                e => panic!("Expected Binary(Add), got {:?}", e),
            }
        }

        #[test]
        fn parse_multiplication_precedence() {
            // 1 + 2 * 3  =>  1 + (2 * 3)
            match parse_expr("1 + 2 * 3") {
                Expr::Binary { op: BinaryOp::Add, left, right } => {
                    match *left {
                        Expr::Literal(Literal::Number(1.0)) => {}
                        e => panic!("Expected left=1, got {:?}", e),
                    }
                    match *right {
                        Expr::Binary { op: BinaryOp::Mul, .. } => {}
                        e => panic!("Expected right=Binary(Mul), got {:?}", e),
                    }
                }
                e => panic!("Expected Binary(Add), got {:?}", e),
            }
        }

        #[test]
        fn parse_modulo() {
            match parse_expr("7 % 3") {
                Expr::Binary { op: BinaryOp::Mod, .. } => {}
                e => panic!("Expected Binary(Mod), got {:?}", e),
            }
        }

        // ----- comparison -----

        #[test]
        fn parse_comparison_chain() {
            // a < b == c
            match parse_expr("a < b == c") {
                Expr::Binary { op: BinaryOp::Equal, left, right } => {
                    match *left {
                        Expr::Binary { op: BinaryOp::Less, .. } => {}
                        e => panic!("Expected left=Binary(Less), got {:?}", e),
                    }
                    match *right {
                        Expr::Variable(name) => assert_eq!(name, "c"),
                        e => panic!("Expected right=Variable(c), got {:?}", e),
                    }
                }
                e => panic!("Expected Binary(Equal), got {:?}", e),
            }
        }

        // ----- logical -----

        #[test]
        fn parse_logical_and() {
            match parse_expr("true && false") {
                Expr::Logical { op: LogicalOp::And, .. } => {}
                e => panic!("Expected Logical(And), got {:?}", e),
            }
        }

        #[test]
        fn parse_logical_or() {
            match parse_expr("true || false") {
                Expr::Logical { op: LogicalOp::Or, .. } => {}
                e => panic!("Expected Logical(Or), got {:?}", e),
            }
        }

        #[test]
        fn parse_logical_precedence() {
            // a || b && c  =>  a || (b && c)
            match parse_expr("a || b && c") {
                Expr::Logical { op: LogicalOp::Or, left, right } => {
                    match *left {
                        Expr::Variable(name) => assert_eq!(name, "a"),
                        e => panic!("Expected left=a, got {:?}", e),
                    }
                    match *right {
                        Expr::Logical { op: LogicalOp::And, .. } => {}
                        e => panic!("Expected right=Logical(And), got {:?}", e),
                    }
                }
                e => panic!("Expected Logical(Or), got {:?}", e),
            }
        }

        // ----- ternary -----

        #[test]
        fn parse_ternary_simple() {
            match parse_expr("a ? 1 : 2") {
                Expr::Ternary { condition, then_branch, else_branch } => {
                    assert!(matches!(*condition, Expr::Variable(_)));
                    assert!(matches!(*then_branch, Expr::Literal(Literal::Number(1.0))));
                    assert!(matches!(*else_branch, Expr::Literal(Literal::Number(2.0))));
                }
                e => panic!("Expected Ternary, got {:?}", e),
            }
        }

        #[test]
        fn parse_ternary_nested_right_assoc() {
            // a ? b : c ? d : e  →  a ? b : (c ? d : e)
            match parse_expr("a ? b : c ? d : e") {
                Expr::Ternary { condition, then_branch, else_branch } => {
                    assert!(matches!(*condition, Expr::Variable(_)));
                    assert!(matches!(*then_branch, Expr::Variable(_)));
                    assert!(matches!(*else_branch, Expr::Ternary { .. }));
                }
                e => panic!("Expected Ternary with nested Ternary else, got {:?}", e),
            }
        }

        #[test]
        fn parse_ternary_with_assignment_in_else() {
            // a ? b : c = d  →  a ? b : (c = d)
            match parse_expr("a ? b : c = 5") {
                Expr::Ternary { else_branch, .. } => {
                    assert!(matches!(*else_branch, Expr::Assign { .. }));
                }
                e => panic!("Expected Ternary with Assign else, got {:?}", e),
            }
        }

        // ----- assignment -----

        #[test]
        fn parse_simple_assignment() {
            match parse_expr("x = 5") {
                Expr::Assign { name, op: AssignOp::Equal, value } => {
                    assert_eq!(name, "x");
                    match *value {
                        Expr::Literal(Literal::Number(5.0)) => {}
                        e => panic!("Expected Number(5), got {:?}", e),
                    }
                }
                e => panic!("Expected Assign, got {:?}", e),
            }
        }

        #[test]
        fn parse_compound_assignment() {
            match parse_expr("x += 2") {
                Expr::Assign { name, op: AssignOp::PlusEqual, value } => {
                    assert_eq!(name, "x");
                    match *value {
                        Expr::Literal(Literal::Number(2.0)) => {}
                        e => panic!("Expected Number(2), got {:?}", e),
                    }
                }
                e => panic!("Expected Assign(PlusEqual), got {:?}", e),
            }
        }

        #[test]
        fn parse_all_compound_ops() {
            let ops = [
                ("+=", AssignOp::PlusEqual),
                ("-=", AssignOp::MinusEqual),
                ("*=", AssignOp::StarEqual),
                ("/=", AssignOp::SlashEqual),
                ("%=", AssignOp::PercentEqual),
            ];
            for (op_str, expected_op) in &ops {
                let expr = parse_expr(&format!("x {} 1", op_str));
                match expr {
                    Expr::Assign { op, .. } => {
                        assert_eq!(std::mem::discriminant(&op), std::mem::discriminant(expected_op));
                    }
                    e => panic!("Expected Assign for '{}', got {:?}", op_str, e),
                }
            }
        }

        // ----- property access -----

        #[test]
        fn parse_property_get() {
            match parse_expr("obj.name") {
                Expr::Get { object, name } => {
                    match *object {
                        Expr::Variable(n) => assert_eq!(n, "obj"),
                        e => panic!("Expected Variable(obj), got {:?}", e),
                    }
                    assert_eq!(name, "name");
                }
                e => panic!("Expected Get, got {:?}", e),
            }
        }

        #[test]
        fn parse_property_set() {
            match parse_expr("obj.name = 5") {
                Expr::Set { object, name, op: AssignOp::Equal, value } => {
                    match *object {
                        Expr::Variable(n) => assert_eq!(n, "obj"),
                        e => panic!("Expected Variable(obj), got {:?}", e),
                    }
                    assert_eq!(name, "name");
                    match *value {
                        Expr::Literal(Literal::Number(5.0)) => {}
                        e => panic!("Expected Number(5), got {:?}", e),
                    }
                }
                e => panic!("Expected Set, got {:?}", e),
            }
        }

        #[test]
        fn parse_chained_property_access() {
            match parse_expr("a.b.c") {
                Expr::Get { object, name } => {
                    assert_eq!(name, "c");
                    match *object {
                        Expr::Get { name: ref inner, .. } => assert_eq!(inner, "b"),
                        e => panic!("Expected chained Get, got {:?}", e),
                    }
                }
                e => panic!("Expected Get, got {:?}", e),
            }
        }

        // ----- index access -----

        #[test]
        fn parse_index_get() {
            match parse_expr("arr[0]") {
                Expr::IndexGet { array, index } => {
                    match *array {
                        Expr::Variable(n) => assert_eq!(n, "arr"),
                        e => panic!("Expected Variable(arr), got {:?}", e),
                    }
                    match *index {
                        Expr::Literal(Literal::Number(0.0)) => {}
                        e => panic!("Expected Number(0), got {:?}", e),
                    }
                }
                e => panic!("Expected IndexGet, got {:?}", e),
            }
        }

        #[test]
        fn parse_index_set() {
            match parse_expr("arr[i] = 42") {
                Expr::IndexSet { array, index, op: AssignOp::Equal, value } => {
                    match *array {
                        Expr::Variable(n) => assert_eq!(n, "arr"),
                        e => panic!("Expected Variable(arr), got {:?}", e),
                    }
                    match *index {
                        Expr::Variable(n) => assert_eq!(n, "i"),
                        e => panic!("Expected Variable(i), got {:?}", e),
                    }
                    match *value {
                        Expr::Literal(Literal::Number(42.0)) => {}
                        e => panic!("Expected Number(42), got {:?}", e),
                    }
                }
                e => panic!("Expected IndexSet, got {:?}", e),
            }
        }

        #[test]
        fn parse_nested_index() {
            match parse_expr("a[1][2]") {
                Expr::IndexGet { array, .. } => {
                    match *array {
                        Expr::IndexGet { .. } => {}
                        e => panic!("Expected nested IndexGet, got {:?}", e),
                    }
                }
                e => panic!("Expected IndexGet, got {:?}", e),
            }
        }

        // ----- function calls -----

        #[test]
        fn parse_call_no_args() {
            match parse_expr("f()") {
                Expr::Call { callee, arguments } => {
                    match *callee {
                        Expr::Variable(n) => assert_eq!(n, "f"),
                        e => panic!("Expected Variable(f), got {:?}", e),
                    }
                    assert!(arguments.is_empty());
                }
                e => panic!("Expected Call, got {:?}", e),
            }
        }

        #[test]
        fn parse_call_with_args() {
            match parse_expr("add(1, 2, 3)") {
                Expr::Call { callee, arguments } => {
                    match *callee {
                        Expr::Variable(n) => assert_eq!(n, "add"),
                        e => panic!("Expected Variable(add), got {:?}", e),
                    }
                    assert_eq!(arguments.len(), 3);
                }
                e => panic!("Expected Call, got {:?}", e),
            }
        }

        #[test]
        fn parse_chained_calls() {
            match parse_expr("f()()") {
                Expr::Call { callee, .. } => {
                    match *callee {
                        Expr::Call { callee, .. } => {
                            match *callee {
                                Expr::Variable(n) => assert_eq!(n, "f"),
                                e => panic!("Expected Variable(f), got {:?}", e),
                            }
                        }
                        e => panic!("Expected inner Call, got {:?}", e),
                    }
                }
                e => panic!("Expected Call, got {:?}", e),
            }
        }

        #[test]
        fn parse_method_style_call() {
            // obj.method()
            match parse_expr("obj.method()") {
                Expr::Call { callee, .. } => {
                    match *callee {
                        Expr::Get { .. } => {}
                        e => panic!("Expected Get, got {:?}", e),
                    }
                }
                e => panic!("Expected Call, got {:?}", e),
            }
        }

        // ----- lambda -----

        #[test]
        fn parse_simple_lambda() {
            match parse_expr("fn(x, y) { return x + y; }") {
                Expr::Lambda { params, body } => {
                    assert_eq!(params, vec!["x", "y"]);
                    assert_eq!(body.len(), 1);
                }
                e => panic!("Expected Lambda, got {:?}", e),
            }
        }

        #[test]
        fn parse_lambda_no_params() {
            match parse_expr("fn() { return 42; }") {
                Expr::Lambda { params, body } => {
                    assert!(params.is_empty());
                    assert_eq!(body.len(), 1);
                }
                e => panic!("Expected Lambda, got {:?}", e),
            }
        }

        // ----- object literal -----

        #[test]
        fn parse_empty_object() {
            match parse_expr("{}") {
                Expr::ObjectLiteral { properties } => assert!(properties.is_empty()),
                e => panic!("Expected ObjectLiteral, got {:?}", e),
            }
        }

        #[test]
        fn parse_object_with_properties() {
            match parse_expr("{ name: \"aster\", version: 1 }") {
                Expr::ObjectLiteral { properties } => {
                    assert_eq!(properties.len(), 2);
                    assert_eq!(properties[0].0, "name");
                    assert_eq!(properties[1].0, "version");
                }
                e => panic!("Expected ObjectLiteral, got {:?}", e),
            }
        }

        // ----- array literal -----

        #[test]
        fn parse_empty_array() {
            match parse_expr("[]") {
                Expr::ArrayLiteral { elements } => assert!(elements.is_empty()),
                e => panic!("Expected ArrayLiteral, got {:?}", e),
            }
        }

        #[test]
        fn parse_array_with_elements() {
            match parse_expr("[1, 2, 3]") {
                Expr::ArrayLiteral { elements } => assert_eq!(elements.len(), 3),
                e => panic!("Expected ArrayLiteral, got {:?}", e),
            }
        }

        #[test]
        fn parse_nested_arrays() {
            match parse_expr("[[1, 2], [3, 4]]") {
                Expr::ArrayLiteral { elements } => {
                    assert_eq!(elements.len(), 2);
                    for e in &elements {
                        assert!(matches!(e, Expr::ArrayLiteral { .. }));
                    }
                }
                e => panic!("Expected ArrayLiteral, got {:?}", e),
            }
        }

        // ----- statements -----

        #[test]
        fn parse_let_statement() {
            match parse_stmt("let x = 5;") {
                Stmt::Let { name, initializer, .. } => {
                    assert_eq!(name, "x");
                    assert!(matches!(initializer, Expr::Literal(Literal::Number(5.0))));
                }
                e => panic!("Expected Let, got {:?}", e),
            }
        }

        #[test]
        fn parse_let_without_semicolon() {
            // Semicolons are optional
            match parse_stmt("let x = 5") {
                Stmt::Let { name, .. } => assert_eq!(name, "x"),
                e => panic!("Expected Let, got {:?}", e),
            }
        }

        #[test]
        fn parse_const_statement() {
            match parse_stmt("const x = 5;") {
                Stmt::Let { name, mutable, .. } => {
                    assert_eq!(name, "x");
                    assert!(!mutable, "const should set mutable=false");
                }
                e => panic!("Expected Let (const), got {:?}", e),
            }
        }

        #[test]
        fn parse_expression_statement() {
            match parse_stmt("x;") {
                Stmt::ExprStmt(Expr::Variable(name)) => assert_eq!(name, "x"),
                e => panic!("Expected ExprStmt(Variable), got {:?}", e),
            }
        }

        #[test]
        fn parse_if_statement() {
            match parse_stmt("if (x) { 1; }") {
                Stmt::If { condition, then_branch, else_branch } => {
                    assert!(matches!(condition, Expr::Variable(_)));
                    assert!(matches!(*then_branch, Stmt::Block(_)));
                    assert!(else_branch.is_none());
                }
                e => panic!("Expected If, got {:?}", e),
            }
        }

        #[test]
        fn parse_if_else_statement() {
            match parse_stmt("if (x) { 1; } else { 2; }") {
                Stmt::If { else_branch, .. } => {
                    assert!(else_branch.is_some());
                }
                e => panic!("Expected If with else, got {:?}", e),
            }
        }

        #[test]
        fn parse_while_statement() {
            match parse_stmt("while (x < 10) { x = x + 1; }") {
                Stmt::While { condition, body } => {
                    assert!(matches!(condition, Expr::Binary { .. }));
                    assert!(matches!(*body, Stmt::Block(_)));
                }
                e => panic!("Expected While, got {:?}", e),
            }
        }

        #[test]
        fn parse_for_statement() {
            match parse_stmt("for (let i = 0; i < 10; i = i + 1) { }") {
                Stmt::For { initializer, condition, step, body } => {
                    assert!(initializer.is_some());
                    assert!(condition.is_some());
                    assert!(step.is_some());
                    assert!(matches!(*body, Stmt::Block(_)));
                }
                e => panic!("Expected For, got {:?}", e),
            }
        }

        #[test]
        fn parse_for_empty_clauses() {
            match parse_stmt("for (;;) { }") {
                Stmt::For { initializer, condition, step, .. } => {
                    assert!(initializer.is_none());
                    assert!(condition.is_none());
                    assert!(step.is_none());
                }
                e => panic!("Expected For, got {:?}", e),
            }
        }

        #[test]
        fn parse_for_in_array() {
            match parse_stmt("for (x in arr) { print(x); }") {
                Stmt::ForIn { var_name, iterable, body } => {
                    assert_eq!(var_name, "x");
                    assert!(matches!(iterable, Expr::Variable(_)));
                    assert!(matches!(*body, Stmt::Block(_)));
                }
                e => panic!("Expected ForIn, got {:?}", e),
            }
        }

        #[test]
        fn parse_for_in_with_object_literal() {
            match parse_stmt("for (k in {a:1,b:2}) { print(k); }") {
                Stmt::ForIn { var_name, iterable, .. } => {
                    assert_eq!(var_name, "k");
                    assert!(matches!(iterable, Expr::ObjectLiteral { .. }));
                }
                e => panic!("Expected ForIn, got {:?}", e),
            }
        }

        #[test]
        fn parse_for_in_with_expression() {
            match parse_stmt("for (v in get_list()) { }") {
                Stmt::ForIn { var_name, .. } => {
                    assert_eq!(var_name, "v");
                }
                e => panic!("Expected ForIn, got {:?}", e),
            }
        }

        #[test]
        fn parse_for_in_distinct_from_c_style() {
            // "for (x = 0; ...)" is C-style for, not for-in
            match parse_stmt("for (x = 0; x < 10; x = x + 1) { }") {
                Stmt::For { .. } => {}
                e => panic!("Expected C-style For, got {:?}", e),
            }
        }

        #[test]
        fn parse_block() {
            match parse_stmt("{ let x = 1; x; }") {
                Stmt::Block(stmts) => assert_eq!(stmts.len(), 2),
                e => panic!("Expected Block, got {:?}", e),
            }
        }

        #[test]
        fn parse_return_statement() {
            match parse_stmt("return 42;") {
                Stmt::Return(Some(expr)) => {
                    assert!(matches!(expr, Expr::Literal(Literal::Number(42.0))));
                }
                e => panic!("Expected Return(42), got {:?}", e),
            }
        }

        #[test]
        fn parse_return_nil() {
            match parse_stmt("return;") {
                Stmt::Return(None) => {}
                e => panic!("Expected Return(None), got {:?}", e),
            }
        }

        #[test]
        fn parse_break_statement() {
            match parse_stmt("break;") {
                Stmt::Break => {}
                e => panic!("Expected Break, got {:?}", e),
            }
        }

        #[test]
        fn parse_continue_statement() {
            match parse_stmt("continue;") {
                Stmt::Continue => {}
                e => panic!("Expected Continue, got {:?}", e),
            }
        }

        #[test]
        fn parse_function_declaration() {
            match parse_stmt("fn add(a, b) { return a + b; }") {
                Stmt::Function { name, params, body } => {
                    assert_eq!(name, "add");
                    assert_eq!(params, vec!["a", "b"]);
                    assert_eq!(body.len(), 1);
                }
                e => panic!("Expected Function, got {:?}", e),
            }
        }

        #[test]
        fn parse_function_no_params() {
            match parse_stmt("fn greet() { print(\"hi\"); }") {
                Stmt::Function { name, params, .. } => {
                    assert_eq!(name, "greet");
                    assert!(params.is_empty());
                }
                e => panic!("Expected Function, got {:?}", e),
            }
        }

        // ----- error recovery -----

        #[test]
        fn error_recovery_skips_past_semicolon() {
            // First statement is invalid, second should parse fine
            let (stmts, errors) = parse("let = 5; let y = 10;");
            assert!(!errors.is_empty(), "Should have parse errors");
            // Should have at least the second statement
            assert!(stmts.len() >= 1);
            // The second statement should be a valid Let for y
            match &stmts.last().unwrap() {
                Stmt::Let { name, .. } => assert_eq!(name, "y"),
                e => panic!("Expected Let(y), got {:?}", e),
            }
        }

        #[test]
        fn error_recovery_at_statement_boundary() {
            let (stmts, errors) = parse("let x = @@@; let y = 10;");
            assert!(!errors.is_empty());
            assert!(stmts.len() >= 1);
        }

        // ----- parse errors -----

        #[test]
        fn error_invalid_assignment_target() {
            let (_stmts, errors) = parse("5 = 10;");
            assert!(!errors.is_empty());
        }

        #[test]
        fn error_missing_closing_paren() {
            let (_stmts, errors) = parse("if (x { 1; }");
            assert!(!errors.is_empty());
        }

        #[test]
        fn error_missing_semicolon_after_for_condition() {
        // for(;;){} is valid — test something actually invalid
        let (_stmts, _errors) = parse("for (let i = 0 i < 10) { }");
        assert!(!_errors.is_empty());
    }

        // ----- parenthesized expression -----

        #[test]
        fn parse_parenthesized_expression() {
            match parse_expr("(1 + 2)") {
                Expr::Binary { op: BinaryOp::Add, .. } => {}
                e => panic!("Expected Binary(Add), got {:?}", e),
            }
        }

        #[test]
        fn parse_nested_parentheses() {
            match parse_expr("((42))") {
                Expr::Literal(Literal::Number(42.0)) => {}
                e => panic!("Expected Number(42), got {:?}", e),
            }
        }
    }