reval 0.2.0

Simple Rust expression evaluator
Documentation 
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//! Manage and evaluate a set of rules or expressions using RuleSets

use crate::{
    error::Result,
    expr::Expr,
    function::{UserFunction, UserFunctions},
    value::{ser::ValueSerializer, Value},
};
use serde::Serialize;

/// The RuleSet type can
pub struct RuleSet {
    rules: Vec<Rule>,
    functions: UserFunctions,
}

impl RuleSet {
    pub fn add_rule(&mut self, rule: Rule) {
        self.rules.push(rule)
    }

    pub fn add_function(
        &mut self,
        name: &str,
        function: impl UserFunction + Send + Sync + 'static,
    ) {
        self.functions.add(name, function)
    }

    pub async fn evaluate(&self, facts: &impl Serialize) -> Result<Vec<Value>> {
        self.evaluate_value(&facts.serialize(ValueSerializer)?)
            .await
    }

    pub async fn evaluate_value(&self, facts: &Value) -> Result<Vec<Value>> {
        let mut context = (&self.functions).into();

        let mut results = Vec::new();

        for rule in self.rules.iter() {
            results.push(rule.expr.evaluate(&mut context, facts).await?);
        }

        Ok(results)
    }
}

pub fn ruleset() -> Builder {
    Builder {
        rules: Vec::new(),
        functions: UserFunctions::default(),
    }
}

pub struct Builder {
    rules: Vec<Rule>,
    functions: UserFunctions,
}

impl Builder {
    pub fn with_rule(mut self, rule: Rule) -> Builder {
        self.rules.push(rule);
        self
    }

    pub fn with_function(
        mut self,
        name: &str,
        function: impl UserFunction + Send + Sync + 'static,
    ) -> Builder {
        self.functions.add(name, function);
        self
    }

    pub fn build(self) -> RuleSet {
        RuleSet {
            rules: self.rules,
            functions: self.functions,
        }
    }
}

/// A rule is an expression with a name
#[derive(Debug, Clone, PartialEq)]
pub struct Rule {
    name: String,
    expr: Expr,
}

impl Rule {
    pub fn new(name: impl Into<String>, expr: Expr) -> Self {
        Self {
            name: name.into(),
            expr,
        }
    }
}