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//! A Rust API wrapper for Boa's `Function` Builtin ECMAScript Object
use crate::{
    builtins::function::ConstructorKind,
    native_function::NativeFunctionObject,
    object::{JsObject, JsObjectType},
    value::TryFromJs,
    Context, JsNativeError, JsResult, JsValue, NativeFunction,
};
use boa_gc::{Finalize, Trace};
use std::ops::Deref;

/// JavaScript `Function` rust object.
#[derive(Debug, Clone, Trace, Finalize)]
pub struct JsFunction {
    inner: JsObject,
}

impl JsFunction {
    /// Creates a new `JsFunction` from an object, without checking if the object is callable.
    pub(crate) fn from_object_unchecked(object: JsObject) -> Self {
        Self { inner: object }
    }

    /// Creates a new, empty intrinsic function object with only its function internal methods set.
    ///
    /// Mainly used to initialize objects before a [`Context`] is available to do so.
    ///
    /// [`Context`]: crate::Context
    pub(crate) fn empty_intrinsic_function(constructor: bool) -> Self {
        Self {
            inner: JsObject::from_proto_and_data(
                None,
                NativeFunctionObject {
                    f: NativeFunction::from_fn_ptr(|_, _, _| Ok(JsValue::undefined())),
                    constructor: constructor.then_some(ConstructorKind::Base),
                    realm: None,
                },
            ),
        }
    }

    /// Creates a [`JsFunction`] from a [`JsObject`], or returns `None` if the object is not a function.
    ///
    /// This does not clone the fields of the function, it only does a shallow clone of the object.
    #[inline]
    #[must_use]
    pub fn from_object(object: JsObject) -> Option<Self> {
        object
            .is_callable()
            .then(|| Self::from_object_unchecked(object))
    }
}

impl From<JsFunction> for JsObject {
    #[inline]
    fn from(o: JsFunction) -> Self {
        o.inner.clone()
    }
}

impl From<JsFunction> for JsValue {
    #[inline]
    fn from(o: JsFunction) -> Self {
        o.inner.clone().into()
    }
}

impl Deref for JsFunction {
    type Target = JsObject;

    #[inline]
    fn deref(&self) -> &Self::Target {
        &self.inner
    }
}

impl JsObjectType for JsFunction {}

impl TryFromJs for JsFunction {
    fn try_from_js(value: &JsValue, _context: &mut Context) -> JsResult<Self> {
        match value {
            JsValue::Object(o) => Self::from_object(o.clone()).ok_or_else(|| {
                JsNativeError::typ()
                    .with_message("object is not a function")
                    .into()
            }),
            _ => Err(JsNativeError::typ()
                .with_message("value is not a Function object")
                .into()),
        }
    }
}