cel-rust-wasm/src/lib.rs

use cel::{Context, Program, Value};
use js_sys;
use std::collections::HashMap;
use wasm_bindgen::prelude::*;

// When the `wee_alloc` feature is enabled, use `wee_alloc` as the global
// allocator.
#[cfg(feature = "wee_alloc")]
#[global_allocator]
static ALLOC: wee_alloc::WeeAlloc = wee_alloc::WeeAlloc::INIT;

#[wasm_bindgen]
extern "C" {
    #[wasm_bindgen(js_namespace = console)]
    fn log(s: &str);
}

macro_rules! console_log {
    ($($t:tt)*) => (log(&format_args!($($t)*).to_string()))
}

#[wasm_bindgen]
pub struct CelResult {
    success: bool,
    result: String,
    error: Option<String>,
}

#[wasm_bindgen]
impl CelResult {
    #[wasm_bindgen(getter)]
    pub fn success(&self) -> bool {
        self.success
    }

    #[wasm_bindgen(getter)]
    pub fn result(&self) -> String {
        self.result.clone()
    }

    #[wasm_bindgen(getter)]
    pub fn error(&self) -> Option<String> {
        self.error.clone()
    }
}

/// Convert a JavaScript value to a CEL Value recursively
fn js_value_to_cel_value(js_val: &JsValue) -> Result<Value, String> {
    if js_val.is_null() || js_val.is_undefined() {
        Ok(Value::Null)
    } else if let Some(b) = js_val.as_bool() {
        Ok(Value::Bool(b))
    } else if let Some(n) = js_val.as_f64() {
        // Check if it's an integer
        if n.fract() == 0.0 && n >= i64::MIN as f64 && n <= i64::MAX as f64 {
            Ok(Value::Int(n as i64))
        } else {
            Ok(Value::Float(n))
        }
    } else if let Some(s) = js_val.as_string() {
        Ok(Value::String(s.into()))
    } else if js_val.is_array() {
        // Handle arrays
        let array = js_sys::Array::from(js_val);
        let mut cel_vec = Vec::new();

        for i in 0..array.length() {
            let item = array.get(i);
            let cel_item = js_value_to_cel_value(&item)?;
            cel_vec.push(cel_item);
        }

        Ok(Value::List(cel_vec.into()))
    } else if js_val.is_object() {
        // Handle objects
        let obj = js_sys::Object::from(js_val.clone());
        let entries = js_sys::Object::entries(&obj);
        let mut cel_map = HashMap::new();

        for i in 0..entries.length() {
            let entry = js_sys::Array::from(&entries.get(i));
            let key = entry
                .get(0)
                .as_string()
                .ok_or_else(|| "Object key must be a string".to_string())?;
            let value = entry.get(1);
            let cel_value = js_value_to_cel_value(&value)?;
            cel_map.insert(key, cel_value);
        }

        Ok(Value::Map(cel_map.into()))
    } else {
        Err(format!("Unsupported JavaScript type"))
    }
}

/// Evaluate a CEL expression with the given context
#[wasm_bindgen]
pub fn evaluate_cel(expression: &str, context: &JsValue) -> CelResult {
    let result = evaluate_cel_internal(expression, context);

    match result {
        Ok(value) => CelResult {
            success: true,
            result: format!("{:?}", value),
            error: None,
        },
        Err(error) => CelResult {
            success: false,
            result: String::new(),
            error: Some(error),
        },
    }
}

/// Evaluate a CEL expression and return the result as a string
#[wasm_bindgen]
pub fn evaluate_cel_string(expression: &str, context: &JsValue) -> Result<String, JsValue> {
    match evaluate_cel_internal(expression, context) {
        Ok(cel_value) => {
            // Convert the result to a reasonable string representation
            let result_string = match &cel_value {
                Value::String(s) => s.clone(),
                _ => format!("{:?}", cel_value).into(),
            };
            Ok(result_string.to_string())
        }
        Err(e) => Err(JsValue::from_str(&e)),
    }
}

fn evaluate_cel_internal(expression: &str, context: &JsValue) -> Result<Value, String> {
    // Compile the CEL expression
    let program = Program::compile(expression).map_err(|e| format!("Compilation error: {}", e))?;

    // Create context
    let mut cel_context = Context::default();

    // Add context variables if provided
    if !context.is_undefined() && !context.is_null() {
        if context.is_object() {
            let obj = js_sys::Object::from(context.clone());
            let entries = js_sys::Object::entries(&obj);

            for i in 0..entries.length() {
                let entry = js_sys::Array::from(&entries.get(i));
                let key = entry
                    .get(0)
                    .as_string()
                    .ok_or_else(|| "Context key must be a string".to_string())?;
                let value = entry.get(1);

                let cel_value = js_value_to_cel_value(&value)
                    .map_err(|e| format!("Failed to convert context value '{}': {}", key, e))?;

                cel_context
                    .add_variable(&key, cel_value)
                    .map_err(|e| format!("Failed to add context variable '{}': {}", key, e))?;
            }
        } else {
            return Err("Context must be an object".to_string());
        }
    }

    // Execute the program
    program
        .execute(&cel_context)
        .map_err(|e| format!("Execution error: {}", e))
}

/// Initialize the WASM module (optional, for debugging)
#[wasm_bindgen(start)]
pub fn main() {
    #[cfg(feature = "console_error_panic_hook")]
    console_error_panic_hook::set_once();

    console_log!("CEL-Rust WASM module initialized!");
}