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use super::lexer::Token;
#[derive(Debug, Clone, PartialEq)]
pub enum Expr {
Path(Vec<String>),
StringLiteral(String),
NumberLiteral(f64),
BooleanLiteral(bool),
Comparison {
left: Box<Expr>,
op: String,
right: Box<Expr>,
},
Filter {
expr: Box<Expr>,
filter_name: String,
args: Vec<Expr>,
},
}
#[derive(Debug, Clone, PartialEq)]
pub enum Node {
Text(String),
Variable(Expr),
If {
condition: Expr,
then_branch: Vec<Node>,
else_branch: Option<Vec<Node>>,
},
For {
item: String,
iterator: Expr,
body: Vec<Node>,
},
}
pub struct Parser {
tokens: Vec<Token>,
pos: usize,
}
impl Parser {
pub fn new(tokens: Vec<Token>) -> Self {
Self { tokens, pos: 0 }
}
fn peek(&self) -> Option<Token> {
if self.pos < self.tokens.len() {
Some(self.tokens[self.pos].clone())
} else {
None
}
}
fn advance(&mut self) -> Option<Token> {
if self.pos < self.tokens.len() {
let t = &self.tokens[self.pos];
self.pos += 1;
Some(t.clone())
} else {
None
}
}
fn expect(&mut self, token: Token) -> Result<(), String> {
if let Some(t) = self.peek() {
if t == token {
self.advance();
Ok(())
} else {
Err(format!("Expected token {:?}, found {:?}", token, t))
}
} else {
Err(format!("Expected token {:?}, reached EOF", token))
}
}
pub fn parse(&mut self) -> Result<Vec<Node>, String> {
let mut nodes = Vec::new();
while self.pos < self.tokens.len() {
if let Some(token) = self.peek() {
match token {
Token::Text(text) => {
nodes.push(Node::Text(text));
self.advance();
}
Token::VariableStart => {
self.advance(); // consume {{
let expr = self.parse_expr()?;
self.expect(Token::VariableEnd)?;
nodes.push(Node::Variable(expr));
}
Token::BlockStart => {
self.advance(); // consume {%
let node = self.parse_block()?;
nodes.push(node);
}
_ => {
return Err(format!("Unexpected token in template body: {:?}", token));
}
}
}
}
Ok(nodes)
}
fn parse_block(&mut self) -> Result<Node, String> {
if let Some(Token::Identifier(keyword)) = self.peek() {
match keyword.as_str() {
"if" => {
self.advance(); // consume "if"
let condition = self.parse_expr()?;
self.expect(Token::BlockEnd)?;
let mut then_branch = Vec::new();
let mut else_branch = None;
while self.pos < self.tokens.len() {
if let Some(Token::BlockStart) = self.peek() {
if let Some(Token::Identifier(ident)) = self.tokens.get(self.pos + 1) {
if ident == "else" {
self.advance(); // consume BlockStart
self.advance(); // consume "else"
self.expect(Token::BlockEnd)?;
let mut else_nodes = Vec::new();
while self.pos < self.tokens.len() {
if let Some(Token::BlockStart) = self.peek() {
if let Some(Token::Identifier(inner_ident)) = self.tokens.get(self.pos + 1) {
if inner_ident == "endif" {
break;
}
}
}
if let Some(Token::Text(text)) = self.peek() {
else_nodes.push(Node::Text(text));
self.advance();
} else if let Some(Token::VariableStart) = self.peek() {
self.advance();
let expr = self.parse_expr()?;
self.expect(Token::VariableEnd)?;
else_nodes.push(Node::Variable(expr));
} else if let Some(Token::BlockStart) = self.peek() {
self.advance();
else_nodes.push(self.parse_block()?);
}
}
else_branch = Some(else_nodes);
continue;
} else if ident == "endif" {
self.advance(); // consume BlockStart
self.advance(); // consume "endif"
self.expect(Token::BlockEnd)?;
break;
}
}
}
if let Some(Token::Text(text)) = self.peek() {
then_branch.push(Node::Text(text));
self.advance();
} else if let Some(Token::VariableStart) = self.peek() {
self.advance();
let expr = self.parse_expr()?;
self.expect(Token::VariableEnd)?;
then_branch.push(Node::Variable(expr));
} else if let Some(Token::BlockStart) = self.peek() {
self.advance();
then_branch.push(self.parse_block()?);
}
}
Ok(Node::If {
condition,
then_branch,
else_branch,
})
}
"for" => {
self.advance(); // consume "for"
let item = if let Some(Token::Identifier(name)) = self.advance() {
name
} else {
return Err("Expected item identifier in for loop".to_string());
};
if let Some(Token::Identifier(keyword_in)) = self.advance() {
if keyword_in != "in" {
return Err(format!("Expected 'in', found '{}'", keyword_in));
}
} else {
return Err("Expected 'in' keyword in for loop".to_string());
}
let iterator = self.parse_expr()?;
self.expect(Token::BlockEnd)?;
let mut body = Vec::new();
while self.pos < self.tokens.len() {
if let Some(Token::BlockStart) = self.peek() {
if let Some(Token::Identifier(ident)) = self.tokens.get(self.pos + 1) {
if ident == "endfor" {
self.advance(); // consume BlockStart
self.advance(); // consume "endfor"
self.expect(Token::BlockEnd)?;
break;
}
}
}
if let Some(Token::Text(text)) = self.peek() {
body.push(Node::Text(text));
self.advance();
} else if let Some(Token::VariableStart) = self.peek() {
self.advance();
let expr = self.parse_expr()?;
self.expect(Token::VariableEnd)?;
body.push(Node::Variable(expr));
} else if let Some(Token::BlockStart) = self.peek() {
self.advance();
body.push(self.parse_block()?);
}
}
Ok(Node::For {
item,
iterator,
body,
})
}
other => Err(format!("Unknown block keyword: {}", other)),
}
} else {
Err("Expected keyword at start of block statement".to_string())
}
}
fn parse_expr(&mut self) -> Result<Expr, String> {
let mut left = self.parse_comparison_expr()?;
while let Some(Token::Operator(op)) = self.peek() {
if op == "|" {
self.advance(); // consume "|"
if let Some(Token::Identifier(filter_name)) = self.advance() {
let mut args = Vec::new();
if let Some(Token::Operator(paren)) = self.peek() {
if paren == "(" {
self.advance(); // consume "("
while self.pos < self.tokens.len() {
if let Some(Token::Operator(close_paren)) = self.peek() {
if close_paren == ")" {
self.advance(); // consume ")"
break;
}
}
args.push(self.parse_expr()?);
if let Some(Token::Comma) = self.peek() {
self.advance();
}
}
}
}
left = Expr::Filter {
expr: Box::new(left),
filter_name,
args,
};
} else {
return Err("Expected filter name after '|'".to_string());
}
} else {
break;
}
}
Ok(left)
}
fn parse_comparison_expr(&mut self) -> Result<Expr, String> {
let left = self.parse_primary_expr()?;
if let Some(Token::Operator(op)) = self.peek() {
if op == "==" || op == "!=" || op == "<" || op == ">" || op == "<=" || op == ">=" {
self.advance(); // consume operator
let right = self.parse_primary_expr()?;
return Ok(Expr::Comparison {
left: Box::new(left),
op,
right: Box::new(right),
});
}
}
Ok(left)
}
fn parse_primary_expr(&mut self) -> Result<Expr, String> {
if let Some(token) = self.peek() {
match token {
Token::StringLiteral(s) => {
self.advance();
Ok(Expr::StringLiteral(s))
}
Token::NumberLiteral(n) => {
self.advance();
Ok(Expr::NumberLiteral(n))
}
Token::Identifier(s) if s == "true" => {
self.advance();
Ok(Expr::BooleanLiteral(true))
}
Token::Identifier(s) if s == "false" => {
self.advance();
Ok(Expr::BooleanLiteral(false))
}
Token::Identifier(first_name) => {
self.advance();
let mut path = vec![first_name];
while let Some(Token::Dot) = self.peek() {
self.advance(); // consume "."
if let Some(Token::Identifier(field)) = self.advance() {
path.push(field);
} else {
return Err("Expected identifier after '.'".to_string());
}
}
Ok(Expr::Path(path))
}
other => Err(format!("Expected primary expression, found {:?}", other)),
}
} else {
Err("Expected primary expression, reached EOF".to_string())
}
}
}