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use std::fmt;
use liquid_error::Result;
use liquid_value::Scalar;
use liquid_value::Value;
use super::Context;
use variable::Variable;
#[derive(Debug, Clone, PartialEq)]
pub enum Expression {
Variable(Variable),
Literal(Value),
}
impl Expression {
pub fn with_literal<S: Into<Scalar>>(literal: S) -> Self {
Expression::Literal(Value::scalar(literal))
}
pub fn into_literal(self) -> Option<Value> {
match self {
Expression::Literal(x) => Some(x),
Expression::Variable(_) => None,
}
}
pub fn into_variable(self) -> Option<Variable> {
match self {
Expression::Literal(_) => None,
Expression::Variable(x) => Some(x),
}
}
pub fn try_evaluate<'c>(&'c self, context: &'c Context) -> Option<&'c Value> {
let val = match *self {
Expression::Literal(ref x) => &x,
Expression::Variable(ref x) => {
let path = x.try_evaluate(context)?;
context.stack().try_get(&path)?
}
};
Some(val)
}
pub fn evaluate<'c>(&'c self, context: &'c Context) -> Result<&'c Value> {
let val = match *self {
Expression::Literal(ref x) => x,
Expression::Variable(ref x) => {
let path = x.evaluate(context)?;
context.stack().get(&path)?
}
};
Ok(val)
}
}
impl fmt::Display for Expression {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match *self {
Expression::Literal(ref x) => write!(f, "{}", x.source()),
Expression::Variable(ref x) => write!(f, "{}", x),
}
}
}