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#[derive(Debug, Clone, PartialEq)]
pub enum Token {
Text(String),
BlockStart, // {% or {%-
BlockEnd, // %} or -%}
VarStart, // {{ or {{-
VarEnd, // }} or -}}
// Keywords
If,
Elif,
Else,
EndIf,
For,
In,
EndFor,
And,
Or,
Not,
True,
False,
Set,
Is,
// Symbols
EqEq, // ==
Ne, // !=
Assign, // = (single, for {% set %})
Plus, // +
Minus, // -
Percent, // %
Pipe, // |
Dot, // .
Colon, // :
Lt, // <
Gt, // >
Le, // <=
Ge, // >=
LBracket, // [
RBracket, // ]
LParen, // (
RParen, // )
Comma, // ,
// Data
Ident(String),
StringLit(String),
IntLit(i64),
}
#[derive(Clone)]
pub struct Tokenizer<'a> {
input: &'a str,
cursor: usize,
in_tag: bool,
trim_blocks: bool,
trim_next_start: bool, // set by -%} or -}} to strip whitespace from the next text
}
impl<'a> Tokenizer<'a> {
pub fn new(input: &'a str) -> Self {
Self {
input,
cursor: 0,
in_tag: false,
trim_blocks: true,
trim_next_start: false,
}
}
fn remaining(&self) -> &'a str {
&self.input[self.cursor..]
}
fn advance(&mut self, n: usize) {
self.cursor += n;
}
pub fn next_token(&mut self) -> Option<Token> {
let rest = self.remaining();
if rest.is_empty() {
return None;
}
if !self.in_tag {
// Jinja2 comments {# ... #} — consume entirely, emit nothing.
// Must be checked before the general {%/{{{ scan because {#
// shares the `{` prefix but is neither a block nor a var tag.
if rest.starts_with("{#") {
// Find the closing #} — if absent, consume the rest (malformed template)
let close = rest.find("#}").map(|i| i + 2).unwrap_or(rest.len());
self.advance(close);
// Respect trim_blocks: eat the newline that follows #} if present
if self.trim_blocks {
let after = self.remaining();
if after.starts_with("\r\n") { self.advance(2); }
else if after.starts_with('\n') { self.advance(1); }
}
// A comment with a leading `-` ({#-) strips preceding whitespace from
// the already-emitted text — we cannot retroactively trim a previous
// token, but we can mark trim_next_start so the *following* text is
// trimmed, which is the practical effect for generation-prompt blocks.
if rest.starts_with("{#-") {
self.trim_next_start = true;
}
return self.next_token(); // skip: recurse to get the next real token
}
// Find first {{ or {% (also matches {{- and {%-)
let pos_block = rest.find("{%");
let pos_var = rest.find("{{");
// Also skip past any {# that may appear before the next real tag
let pos_comment = rest.find("{#");
let next_tag = match (pos_block, pos_var, pos_comment) {
(Some(b), Some(v), Some(c)) => Some(b.min(v).min(c)),
(Some(b), Some(v), None) => Some(b.min(v)),
(Some(b), None, Some(c)) => Some(b.min(c)),
(None, Some(v), Some(c)) => Some(v.min(c)),
(Some(b), None, None) => Some(b),
(None, Some(v), None) => Some(v),
(None, None, Some(c)) => Some(c),
(None, None, None) => None,
};
match next_tag {
Some(0) => {
// We are sitting right at the tag opener — re-enter to handle {#
if rest.starts_with("{#") {
return self.next_token();
}
if rest.starts_with("{%-") {
self.advance(3);
self.in_tag = true;
Some(Token::BlockStart)
} else if rest.starts_with("{%") {
self.advance(2);
self.in_tag = true;
Some(Token::BlockStart)
} else if rest.starts_with("{{-") {
self.advance(3);
self.in_tag = true;
Some(Token::VarStart)
} else {
self.advance(2);
self.in_tag = true;
Some(Token::VarStart)
}
}
Some(idx) => {
// There is text before the tag
let raw_text = &rest[..idx];
let upcoming = &rest[idx..];
// {#- strips trailing whitespace from the preceding text too
let text = if upcoming.starts_with("{%-") || upcoming.starts_with("{{-") || upcoming.starts_with("{#-") {
raw_text.trim_end().to_string()
} else {
raw_text.to_string()
};
// -%} or -}} earlier set trim_next_start to strip leading whitespace
let text = if self.trim_next_start {
self.trim_next_start = false;
text.trim_start().to_string()
} else {
text
};
self.advance(idx);
if text.is_empty() {
// All whitespace consumed by trim — skip the empty token,
// and the next call will hit the {# or real tag at position 0
self.next_token()
} else {
Some(Token::Text(text))
}
}
None => {
// No more tags — rest is all text
let mut text = rest.to_string();
if self.trim_next_start {
self.trim_next_start = false;
text = text.trim_start().to_string();
}
self.advance(rest.len());
if text.is_empty() {
None
} else {
Some(Token::Text(text))
}
}
}
} else {
// In tag: skip leading whitespace
let rest_trimmed = rest.trim_start();
let skipped = rest.len() - rest_trimmed.len();
self.advance(skipped);
let rest = self.remaining();
if rest.is_empty() {
return None;
}
// Check tag ends — trim variants first
if rest.starts_with("-%}") {
self.advance(3);
self.in_tag = false;
self.trim_next_start = true; // strip all leading whitespace from next text
return Some(Token::BlockEnd);
}
if rest.starts_with("%}") {
self.advance(2);
self.in_tag = false;
if self.trim_blocks {
let after = self.remaining();
if after.starts_with("\r\n") {
self.advance(2);
} else if after.starts_with('\n') {
self.advance(1);
}
}
return Some(Token::BlockEnd);
}
if rest.starts_with("-}}") {
self.advance(3);
self.in_tag = false;
self.trim_next_start = true;
return Some(Token::VarEnd);
}
if rest.starts_with("}}") {
self.advance(2);
self.in_tag = false;
return Some(Token::VarEnd);
}
// Multi-char symbols (check before single-char variants)
if rest.starts_with("==") {
self.advance(2);
return Some(Token::EqEq);
}
if rest.starts_with("!=") {
self.advance(2);
return Some(Token::Ne);
}
if rest.starts_with('+') {
self.advance(1);
return Some(Token::Plus);
}
if rest.starts_with('-') {
self.advance(1);
return Some(Token::Minus);
}
if rest.starts_with('|') {
self.advance(1);
return Some(Token::Pipe);
}
if rest.starts_with('.') {
self.advance(1);
return Some(Token::Dot);
}
if rest.starts_with('[') {
self.advance(1);
return Some(Token::LBracket);
}
if rest.starts_with(']') {
self.advance(1);
return Some(Token::RBracket);
}
if rest.starts_with('(') {
self.advance(1);
return Some(Token::LParen);
}
if rest.starts_with(')') {
self.advance(1);
return Some(Token::RParen);
}
if rest.starts_with(',') {
self.advance(1);
return Some(Token::Comma);
}
if rest.starts_with('%') {
self.advance(1);
return Some(Token::Percent);
}
if rest.starts_with(':') {
self.advance(1);
return Some(Token::Colon);
}
// Comparison operators (check 2-char before 1-char)
if rest.starts_with("<=") {
self.advance(2);
return Some(Token::Le);
}
if rest.starts_with(">=") {
self.advance(2);
return Some(Token::Ge);
}
if rest.starts_with('<') {
self.advance(1);
return Some(Token::Lt);
}
if rest.starts_with('>') {
self.advance(1);
return Some(Token::Gt);
}
// Single = (must come after == check)
if rest.starts_with('=') {
self.advance(1);
return Some(Token::Assign);
}
let first = rest.chars().next().unwrap();
// Integer literals
if first.is_ascii_digit() {
let int_str: String = rest.chars().take_while(|c| c.is_ascii_digit()).collect();
self.advance(int_str.len());
let n: i64 = int_str.parse().unwrap_or(0);
return Some(Token::IntLit(n));
}
// String literals
if first == '\'' || first == '"' {
let quote = first;
let mut end_idx = 1usize;
let mut s = String::new();
let mut chars = rest[1..].chars();
loop {
match chars.next() {
None => return None, // unterminated string
Some(c) if c == quote => {
self.advance(end_idx + quote.len_utf8());
return Some(Token::StringLit(s));
}
Some('\\') => {
end_idx += 1;
match chars.next() {
None => return None,
Some(esc) => {
end_idx += esc.len_utf8();
match esc {
'n' => s.push('\n'),
't' => s.push('\t'),
'r' => s.push('\r'),
'\'' => s.push('\''),
'"' => s.push('"'),
'\\' => s.push('\\'),
_ => s.push(esc),
}
}
}
}
Some(c) => {
end_idx += c.len_utf8();
s.push(c);
}
}
}
}
// Identifiers and keywords
if first.is_alphabetic() || first == '_' {
let ident_str: String = rest
.chars()
.take_while(|c| c.is_alphanumeric() || *c == '_')
.collect();
self.advance(ident_str.len());
return match ident_str.as_str() {
"if" => Some(Token::If),
"elif" => Some(Token::Elif),
"else" => Some(Token::Else),
"endif" => Some(Token::EndIf),
"for" => Some(Token::For),
"in" => Some(Token::In),
"endfor" => Some(Token::EndFor),
"and" => Some(Token::And),
"or" => Some(Token::Or),
"not" => Some(Token::Not),
"true" => Some(Token::True),
"false" => Some(Token::False),
"set" => Some(Token::Set),
"is" => Some(Token::Is),
_ => Some(Token::Ident(ident_str)),
};
}
// Unknown character — skip and continue
self.advance(1);
self.next_token()
}
}
}