use crate::dataframe;

#[derive(Debug)]
pub struct Engine<'a> {
    engine: rhai::Engine,
    scope: rhai::Scope<'a>,
}

impl<'a> Default for Engine<'a> {
    fn default() -> Self {
        let mut engine = rhai::Engine::new();
        engine.set_fast_operators(false);
        dataframe::setup_engine(&mut engine);

        Self {
            engine,
            scope: rhai::Scope::new(),
        }
    }
}

impl<'a> Engine<'a> {
    pub fn process_script(&mut self, script: &str) -> Output {
        match self
            .engine
            .eval_with_scope::<rhai::Dynamic>(&mut self.scope, script)
        {
            Ok(res) if res.is::<dataframe::DataFrame>() => {
                let frame = rhai::Dynamic::cast::<dataframe::DataFrame>(res);
                Output::DataFrame(frame)
            }
            Ok(res) if res.is::<()>() => Output::None,
            Ok(res) if res.is::<dataframe::Series>() => {
                let series = rhai::Dynamic::cast::<dataframe::Series>(res);
                Output::Series(series)
            }
            Ok(res) => Output::Scalar(res),
            Err(e) => Output::Error(e.to_string()),
        }
    }
}

#[derive(Debug, Clone)]
pub enum Output {
    None,
    Scalar(rhai::Dynamic),
    DataFrame(dataframe::DataFrame),
    Series(dataframe::Series),
    Error(String),
}

impl Default for Output {
    fn default() -> Self {
        Output::None
    }
}

impl PartialEq for Output {
    fn eq(&self, other: &Self) -> bool {
        match (self, other) {
            (Self::Scalar(l0), Self::Scalar(r0)) => l0.to_string() == r0.to_string(),
            (Self::DataFrame(l0), Self::DataFrame(r0)) => l0 == r0,
            (Self::Series(l0), Self::Series(r0)) => l0 == r0,
            (Self::Error(l0), Self::Error(r0)) => l0 == r0,
            _ => core::mem::discriminant(self) == core::mem::discriminant(other),
        }
    }
}

impl Output {
    pub fn into_frame(self) -> dataframe::DataFrame {
        if let Self::DataFrame(v) = self {
            return v;
        }
        panic!("Not a dataframe");
    }
    pub fn into_series(self) -> dataframe::Series {
        if let Self::Series(v) = self {
            return v;
        }
        panic!("Not a series");
    }
    pub fn into_scalar(self) -> rhai::Dynamic {
        if let Self::Scalar(v) = self {
            return v;
        }
        panic!("Not a scalar");
    }
}

#[cfg(test)]
pub mod tests {
    use super::*;

    pub fn process(script: &str) -> Output {
        let mut engine = Engine::default();
        engine.process_script(script)
    }
}