use crate::{
    obj::{prelude::*, reserved::*},
    vm::error::*,
};
use once_cell::sync::Lazy;
use shredder::Scan;
use std::fmt::{self, Debug, Formatter};

pub type BoolRef = ObjRef<Bool>;

#[derive(Scan)]
pub struct Bool {
    value: bool,
    vtable: Vtable,
    attrs: Attrs,
}

impl Bool {
    /// Gets the value of this boolean.
    pub fn value(&self) -> bool {
        self.value
    }
}

impl From<bool> for BoolRef {
    fn from(value: bool) -> Self {
        if value {
            BOOL_TRUE.clone()
        } else {
            BOOL_FALSE.clone()
        }
    }
}

impl_obj_readonly!(Bool);

impl Debug for Bool {
    fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
        fmt.debug_struct("Bool").field("value", &self.value).finish()
    }
}

/// A true boolean value.
///
/// This value should be the only instance of a "true" boolean.
pub static BOOL_TRUE: Lazy<BoolRef> = Lazy::new(||
    self_referring_obj! {
        Bool {
            value: true,
            vtable: Default::default(),
            attrs: Default::default(),
        },
        vtable: |obj_ref: ObjRef| vtable! {
            BOOL_MEMBER_NAME.sym => Method::new_obj(obj_ref.clone(), BOOL_BOOL_FUN.clone()),
        }
    }
);

/// A false boolean value.
///
/// This value should be the only instance of a "false" boolean.
pub static BOOL_FALSE: Lazy<BoolRef> = Lazy::new(||
    self_referring_obj! {
        Bool {
            value: false,
            vtable: Default::default(),
            attrs: Default::default(),
        },
        vtable: |obj_ref: ObjRef| vtable! {
            BOOL_MEMBER_NAME.sym => Method::new_obj(obj_ref.clone(), BOOL_BOOL_FUN.clone()),
        }
    }
);

////////////////////////////////////////////////////////////////////////////////
// Builtin Bool functions
////////////////////////////////////////////////////////////////////////////////

/// Bool.__bool__(self) impl
static BOOL_BOOL_FUN: Lazy<NativeFunRef> = Lazy::new(|| {
    NativeFun::new_obj(1, |_callee, vm, args| {
        {
            read_obj_downcast!(let value: Option<&Bool> = &args[0]);
            value.ok_or_else(|| Error::ValueError {
                error: "expected Bool value".to_string(),
            })?;
        }
        // just push a copy of the "self" value
        vm.push(args[0].clone());
        Ok(crate::vm::signal::Signal::Return)
    })
});