use super::expression::Expression;
use super::{complex::Complex, context::Context};

enum FunctionArgumentType {
    ExpressionArgument(Vec<Expression>),
    ValueArgument(Vec<Complex>),
}

pub struct FunctionArgument {
    args: FunctionArgumentType,
    len: usize,
}

impl FunctionArgument {
    pub fn from_expressions(args: Vec<Expression>) -> Self {
        Self {
            len: args.len(),
            args: FunctionArgumentType::ExpressionArgument(args),
        }
    }

    pub fn from_values(args: Vec<Complex>) -> Self {
        Self {
            len: args.len(),
            args: FunctionArgumentType::ValueArgument(args),
        }
    }

    pub fn len(&self) -> usize {
        self.len
    }

    pub fn is_empty(&self) -> bool {
        self.len == 0
    }

    pub fn eval_args(&self, ctx: &Context) -> Result<Vec<Complex>, String> {
        match &self.args {
            FunctionArgumentType::ExpressionArgument(args) => {
                args.iter().map(|a| a.evaluate(ctx)).collect()
            }
            FunctionArgumentType::ValueArgument(args) => Ok(args.to_vec()),
        }
    }
}

pub trait Function {
    fn eval(&self, args: &FunctionArgument, ctx: &Context) -> Result<Complex, String>;
}

#[macro_export]
macro_rules! functions {
    {$($x:expr => $y:expr), *} => {
        {
            let mut h : HashMap<String, Arc<dyn Function>> = HashMap::new();
            $(
                h.insert($x.to_string(), Arc::new($y));
            )*
            h
        }
    };
}

// Some default implementations
impl<T> Function for T
where
    T: Fn(Complex) -> Complex,
{
    fn eval(&self, args: &FunctionArgument, ctx: &Context) -> Result<Complex, String> {
        if args.len() == 1 {
            match args.eval_args(ctx) {
                Ok(args) => Ok(self(args[0])),
                Err(e) => Err(e),
            }
        } else {
            Err("too many arguments".to_string())
        }
    }
}

pub struct EmptyFunction {}

impl Function for EmptyFunction {
    fn eval(&self, _args: &FunctionArgument, _ctx: &Context) -> Result<Complex, String> {
        Err("function not implemented in this scope".to_string())
    }
}