use std::fmt;

use crate::types::{Namespace, ObjectRef};

use super::result::Params;

// Function Trait ------------------------------------------------------

pub trait FuncTrait {

fn ns(&self) -> &Namespace;

fn module_name(&self) -> &String;

fn module(&self) -> ObjectRef;

fn name(&self) -> &String;

fn params(&self) -> &Params;

fn get_doc(&self) -> ObjectRef {

self.ns().get("$doc").unwrap().clone()

}

/// Returns the required number of args.

fn arity(&self) -> usize {

let params = self.params();

if let Some(name) = params.last() {

if name.is_empty() {

// Has var args; return number of required args

params.len() - 1

} else {

// Does not have var args; all args required

params.len()

}

} else {

0

}

}

/// If the function has var args, this returns the index of the var

/// args in the args list (which is also equal to the required

/// number of args).

fn var_args_index(&self) -> Option<usize> {

let params = self.params();

if let Some(name) = params.last() {

if name.is_empty() {

return Some(params.len() - 1);

}

}

None

}

fn has_var_args(&self) -> bool {

self.var_args_index().is_some()

}

fn format_string(&self, id: Option<usize>) -> String {

let name = &self.name();

let arity = self.arity();

let suffix = if self.var_args_index().is_some() { "+" } else { "" };

let id = id.map_or_else(|| "".to_string(), |id| format!(" @ {id}"));

format!("function {name}/{arity}{suffix}{id}")

}

}

// Display -------------------------------------------------------------

impl fmt::Display for dyn FuncTrait {

fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

write!(f, "{}", self.format_string(None))

}

}

impl fmt::Debug for dyn FuncTrait {

fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

write!(f, "{self}")

}

}