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//! Language statement, code which executes arbitrary instructions, like for loops or print to screen.
use super::{
super::Template,
super::{Context, Error, Token, TokenWithContext, Tokenize, Value},
Expression, Term,
};
use std::iter::{Iterator, Peekable};
use std::path::PathBuf;
macro_rules! expect {
($got:expr, $expected:expr) => {
if $got.token() != $expected {
// println!("{}:{}", file!(), line!());
return Err(Error::WrongToken($got, $expected));
}
};
}
macro_rules! block_end {
($iter:expr) => {
while let Some(token) = $iter.next() {
expect!(token, Token::BlockEnd);
break;
}
};
}
/// Program statement.
#[derive(Debug, Clone)]
pub enum Statement {
// e.g. `<%= variable %>`
Print(Expression),
PrintRaw(Expression),
// e.g. `<html><body></body></html>`
PrintText(String),
// e.g. `<% if variable == 5 %>right<% else %>wrong<% end %>`
If {
expression: Expression,
if_body: Vec<Statement>,
else_body: Vec<Statement>,
else_if: bool,
},
// `<% else %>`
Else,
// `<% end %>
End,
// `<% for var in [1, 2, 3] %> <%= var %> <% end %>`
For {
variable: Term,
list: Expression,
body: Vec<Statement>,
},
Render(PathBuf),
}
impl Statement {
/// Compile statement from text.
pub fn from_str(string: &str) -> Result<Self, Error> {
let tokens = string.tokenize()?;
Statement::parse(&mut tokens.into_iter().peekable())
}
/// Evaluate a statement given the context.
pub fn evaluate(&self, context: &Context) -> Result<String, Error> {
match self {
Statement::Render(path) => {
let template = Template::load(&path)?;
template.render(context)
}
Statement::PrintText(text) => Ok(text.clone()),
Statement::If {
expression,
if_body,
else_body,
..
} => {
let mut result = String::new();
let truthy = match expression.evaluate(&context) {
Ok(result) => result.truthy(),
Err(Error::UndefinedVariable(name)) => match expression {
Expression::Term { .. } => false,
_ => return Err(Error::UndefinedVariable(name)),
},
Err(err) => return Err(err),
};
if truthy {
for statement in if_body {
result.push_str(&statement.evaluate(&context)?);
}
} else {
for statement in else_body {
result.push_str(&statement.evaluate(&context)?);
}
}
Ok(result)
}
Statement::PrintRaw(expression) => Ok(expression.evaluate(context)?.to_string()),
Statement::Print(expression) => {
let value = expression.evaluate(context)?;
Ok(match value {
Value::SafeString(s) => s,
value => crate::safe_html(&value.to_string()),
})
}
Statement::For {
variable,
list,
body,
} => {
let mut result = String::new();
let list = list.evaluate(context)?;
let mut for_context = context.clone();
let values = match list {
Value::List(values) => values,
Value::Hash(hash) => hash
.keys()
.cloned()
.into_iter()
.zip(hash.values().cloned())
.map(|(k, v)| Value::List(vec![Value::String(k), v]))
.collect::<Vec<_>>(),
Value::String(s) => s
.chars()
.map(|c| Value::String(String::from(c)))
.collect::<Vec<_>>(),
value => return Err(Error::Runtime(format!("not an iterable: {}", value))),
};
for value in values {
match variable {
// Convert the variable to a value from the list.
Term::Variable(name) => {
for_context.set(&name, value)?;
}
Term::Constant(_) => (), // Looks like just a loop with no variables
_ => todo!(), // Function call is interesting
};
for statement in body {
result.push_str(&statement.evaluate(&for_context)?);
}
}
Ok(result)
}
statement => todo!("evaluating {:?}", statement),
}
}
/// Parse the statement from a stream of tokens. This consumes tokens from the stream.
pub fn parse(
iter: &mut Peekable<impl Iterator<Item = TokenWithContext>>,
) -> Result<Statement, Error> {
loop {
let next = iter.next().ok_or(Error::Eof("statement parse"))?;
match next.token() {
Token::End => {
block_end!(iter);
return Ok(Statement::End);
}
Token::Text(string) => return Ok(Statement::PrintText(string)),
Token::BlockStart | Token::BlockEnd => (),
Token::BlockStartPrint => {
let expression = Expression::parse(iter)?;
block_end!(iter);
return Ok(Statement::Print(expression));
}
Token::BlockStartPrintRaw => {
let expression = Expression::parse(iter)?;
block_end!(iter);
return Ok(Statement::PrintRaw(expression));
}
Token::BlockStartRender => {
let path = iter.next().ok_or(Error::Eof("block start render"))?;
block_end!(iter);
match path.token() {
Token::Value(Value::String(path)) => {
return Ok(Statement::Render(PathBuf::from(path)))
}
_ => return Err(Error::Syntax(path)),
}
}
Token::Else => {
block_end!(iter);
return Ok(Statement::Else);
}
Token::If | Token::ElseIf => {
let else_if = next.token() == Token::ElseIf;
let (mut if_body, mut else_body) = (vec![], vec![]);
let expression = Expression::parse(iter)?;
loop {
let statement = Statement::parse(iter)?;
match statement {
Statement::End => {
return Ok(Statement::If {
expression,
if_body,
else_body,
else_if,
})
}
Statement::If { else_if: true, .. } => {
else_body.push(statement);
break;
// if
// elsif
// elsif
// else
// end
//
// translates into this:
//
// if
// else
// if
// else
// if
// else
// end
// end
// end
}
Statement::Else => loop {
let statement = Statement::parse(iter)?;
match statement {
Statement::End => {
return Ok(Statement::If {
expression,
if_body,
else_body,
else_if,
})
}
statement => else_body.push(statement),
}
},
statement => if_body.push(statement),
}
}
return Ok(Statement::If {
expression,
if_body,
else_body,
else_if,
});
}
Token::For => {
let variable = Expression::parse(iter)?;
let term = match variable {
Expression::Term { term } => term,
_ => return Err(Error::Syntax(next)),
};
let in_ = iter.next().ok_or(Error::Eof("statement for"))?;
expect!(in_, Token::In);
let list = Expression::parse(iter)?;
block_end!(iter);
let mut body = vec![];
loop {
let statement = Statement::parse(iter)?;
match statement {
Statement::End => {
break;
}
statement => body.push(statement),
}
}
return Ok(Statement::For {
variable: term,
list,
body,
});
}
_ => return Err(Error::Syntax(next)),
}
}
}
}
#[cfg(test)]
mod test {
use super::*;
use crate::view::template::{
language::expression::Evaluate,
lexer::{Tokenize, Value},
};
#[test]
fn test_statements_basic() -> Result<(), Error> {
let t1 = r#"<% if variable == 5 %>right<% else %>wrong<% end %>"#.tokenize()?;
let ast = Statement::parse(&mut t1.into_iter().peekable())?;
let mut context = Context::default();
context.set("variable", Value::Integer(5))?;
let value = ast.evaluate(&context)?;
assert!(value == "right");
Ok(())
}
#[test]
fn test_statements_if_else() -> Result<(), Error> {
let t1 = "<% if variable == 5 %>
right
<% elsif variable == 6 %>
wrong
<% else %>
neither
<% end %>"
.tokenize()?;
let ast = Statement::parse(&mut t1.into_iter().peekable()).unwrap();
let mut context = Context::default();
context.set("variable", Value::Integer(7))?;
let result = ast.evaluate(&context)?;
assert_eq!(result.trim(), "neither");
Ok(())
}
#[test]
fn test_print_expression() -> Result<(), Error> {
let t1 = "<%= variable %>";
let mut context = Context::default();
context.set("variable", Value::Integer(7))?;
let ast = Statement::parse(&mut t1.tokenize()?.into_iter().peekable())?;
let result = ast.evaluate(&context)?;
assert_eq!(result, "7");
Ok(())
}
#[test]
fn test_for_loop() -> Result<(), Error> {
let t1 = r#"<% for a in [1, "hello", 3.45, variable] %><li><%= a %></li><% end %>"#
.tokenize()?;
let mut context = Context::default();
context.set("variable", Value::String("variable value".into()))?;
let ast = Statement::parse(&mut t1.into_iter().peekable())?;
let result = ast.evaluate(&context)?;
assert_eq!(
result,
"<li>1</li><li>hello</li><li>3.45</li><li>variable value</li>"
);
let result = Statement::from_str(
"
<% for v in [1, 2, 3].enumerate %>
<p><%= v.0 + 1 %>. <%= v.1 %></p>
<% end %>
"
.trim(),
)?
.evaluate(&Context::default())?;
assert_eq!(result, "\n<p>1. 1</p>\n\n<p>2. 2</p>\n\n<p>3. 3</p>\n");
Ok(())
}
#[test]
fn test_newline() {
// Make sure lexer doesn't interpret new lines as something.
let t1 = "<% 1 + 5 \n %>".evaluate_default().unwrap();
assert_eq!(t1, Value::Integer(6));
}
}