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use crate::nodes::{BinaryOperator, Block, Expression};
use crate::process::{DefaultVisitor, Evaluator, NodeProcessor, NodeVisitor};
use crate::rules::{
Context, FlawlessRule, RuleConfiguration, RuleConfigurationError, RuleProperties,
};
use super::verify_no_rule_properties;
#[derive(Debug, Clone, Default)]
struct Computer {
evaluator: Evaluator,
}
impl Computer {
fn replace_with(&mut self, expression: &Expression) -> Option<Expression> {
match expression {
Expression::Unary(_) => {
if !self.evaluator.has_side_effects(expression) {
self.evaluator.evaluate(expression).to_expression()
} else {
None
}
}
Expression::Binary(binary) => {
if !self.evaluator.has_side_effects(expression) {
self.evaluator
.evaluate(expression)
.to_expression()
.or_else(|| {
match binary.operator() {
BinaryOperator::And => {
self.evaluator.evaluate(binary.left()).is_truthy().map(
|is_truthy| {
if is_truthy {
binary.right().clone()
} else {
binary.left().clone()
}
},
)
}
BinaryOperator::Or => {
self.evaluator.evaluate(binary.left()).is_truthy().map(
|is_truthy| {
if is_truthy {
binary.left().clone()
} else {
binary.right().clone()
}
},
)
}
_ => None,
}
.map(|mut expression| {
self.process_expression(&mut expression);
expression
})
})
} else {
match binary.operator() {
BinaryOperator::And => {
if !self.evaluator.has_side_effects(binary.left()) {
self.evaluator.evaluate(binary.left()).is_truthy().map(
|is_truthy| {
if is_truthy {
binary.right().clone()
} else {
binary.left().clone()
}
},
)
} else {
None
}
}
BinaryOperator::Or => {
if !self.evaluator.has_side_effects(binary.left()) {
self.evaluator.evaluate(binary.left()).is_truthy().map(
|is_truthy| {
if is_truthy {
binary.left().clone()
} else {
binary.right().clone()
}
},
)
} else {
None
}
}
_ => None,
}
}
}
Expression::If(_) => {
if !self.evaluator.has_side_effects(expression) {
self.evaluator.evaluate(expression).to_expression()
} else {
None
}
}
_ => None,
}
}
}
impl NodeProcessor for Computer {
fn process_expression(&mut self, expression: &mut Expression) {
if let Some(replace_with) = self.replace_with(expression) {
*expression = replace_with;
}
}
}
pub const COMPUTE_EXPRESSIONS_RULE_NAME: &str = "compute_expression";
/// A rule that compute expressions that do not have any side-effects.
#[derive(Debug, Default, PartialEq, Eq)]
pub struct ComputeExpression {}
impl FlawlessRule for ComputeExpression {
fn flawless_process(&self, block: &mut Block, _: &Context) {
let mut processor = Computer::default();
DefaultVisitor::visit_block(block, &mut processor);
}
}
impl RuleConfiguration for ComputeExpression {
fn configure(&mut self, properties: RuleProperties) -> Result<(), RuleConfigurationError> {
verify_no_rule_properties(&properties)?;
Ok(())
}
fn get_name(&self) -> &'static str {
COMPUTE_EXPRESSIONS_RULE_NAME
}
fn serialize_to_properties(&self) -> RuleProperties {
RuleProperties::new()
}
}
#[cfg(test)]
mod test {
use super::*;
use crate::rules::Rule;
use insta::assert_json_snapshot;
fn new_rule() -> ComputeExpression {
ComputeExpression::default()
}
#[test]
fn serialize_default_rule() {
let rule: Box<dyn Rule> = Box::new(new_rule());
assert_json_snapshot!("default_compute_expression", rule);
}
}