use std::marker::PhantomData;
use std::mem::MaybeUninit;

use crate::support::{int, Opaque};
use crate::Context;
use crate::InIsolate;
use crate::Isolate;
use crate::Local;
use crate::ToLocal;
use crate::Value;

extern "C" {
  fn v8__Function__New(
    context: *mut Context,
    callback: extern "C" fn(&FunctionCallbackInfo),
  ) -> *mut Function;
  fn v8__Function__Call(
    function: *mut Function,
    context: *mut Context,
    recv: *mut Value,
    argc: int,
    argv: *mut *mut Value,
  ) -> *mut Value;

  fn v8__FunctionTemplate__New(
    isolate: &Isolate,
    callback: extern "C" fn(&FunctionCallbackInfo),
  ) -> *mut FunctionTemplate;
  fn v8__FunctionTemplate__GetFunction(
    fn_template: *mut FunctionTemplate,
    context: *mut Context,
  ) -> *mut Function;

  fn v8__FunctionCallbackInfo__GetIsolate(
    info: &FunctionCallbackInfo,
  ) -> &mut Isolate;
  fn v8__FunctionCallbackInfo__Length(info: &FunctionCallbackInfo) -> int;
  fn v8__FunctionCallbackInfo__GetReturnValue(
    info: &FunctionCallbackInfo,
    out: *mut ReturnValue,
  );

  fn v8__ReturnValue__Set(rv: &mut ReturnValue, value: *mut Value);
  fn v8__ReturnValue__Get(rv: &ReturnValue) -> *mut Value;
  fn v8__ReturnValue__GetIsolate(rv: &ReturnValue) -> *mut Isolate;
}

// Npte: the 'cb lifetime is required because the ReturnValue object must not
// outlive the FunctionCallbackInfo/PropertyCallbackInfo object from which it
// is derived.
#[repr(C)]
pub struct ReturnValue<'cb>(*mut Opaque, PhantomData<&'cb ()>);

/// In V8 ReturnValue<> has a type parameter, but
/// it turns out that in most of the APIs it's ReturnValue<Value>
/// and for our purposes we currently don't need
/// other types. So for now it's a simplified version.
impl<'cb> ReturnValue<'cb> {
  // NOTE: simplest setter, possibly we'll need to add
  // more setters specialized per type
  pub fn set(&mut self, mut value: Local<Value>) {
    unsafe { v8__ReturnValue__Set(&mut *self, &mut *value) }
  }

  /// Convenience getter for Isolate
  pub fn get_isolate(&mut self) -> &mut Isolate {
    unsafe { &mut *v8__ReturnValue__GetIsolate(self) }
  }

  /// Getter. Creates a new Local<> so it comes with a certain performance
  /// hit. If the ReturnValue was not yet set, this will return the undefined
  /// value.
  pub fn get<'sc>(
    &mut self,
    scope: &mut impl ToLocal<'sc>,
  ) -> Local<'sc, Value> {
    unsafe { scope.to_local(v8__ReturnValue__Get(self)) }.unwrap()
  }
}

/// The argument information given to function call callbacks.  This
/// class provides access to information about the context of the call,
/// including the receiver, the number and values of arguments, and
/// the holder of the function.
#[repr(C)]
pub struct FunctionCallbackInfo(Opaque);

impl InIsolate for FunctionCallbackInfo {
  #[allow(clippy::cast_ref_to_mut)]
  fn isolate(&mut self) -> &mut Isolate {
    self.get_isolate()
  }
}

impl<'s> ToLocal<'s> for FunctionCallbackInfo {}

impl FunctionCallbackInfo {
  /// The ReturnValue for the call.
  pub fn get_return_value(&self) -> ReturnValue {
    let mut rv = MaybeUninit::<ReturnValue>::uninit();
    unsafe {
      v8__FunctionCallbackInfo__GetReturnValue(self, rv.as_mut_ptr());
      rv.assume_init()
    }
  }

  /// The current Isolate.
  #[allow(clippy::mut_from_ref)]
  pub fn get_isolate(&mut self) -> &mut Isolate {
    unsafe { v8__FunctionCallbackInfo__GetIsolate(self) }
  }

  /// The number of available arguments.
  pub fn length(&self) -> int {
    unsafe { v8__FunctionCallbackInfo__Length(self) }
  }
}

/// A FunctionTemplate is used to create functions at runtime. There
/// can only be one function created from a FunctionTemplate in a
/// context.  The lifetime of the created function is equal to the
/// lifetime of the context.  So in case the embedder needs to create
/// temporary functions that can be collected using Scripts is
/// preferred.
///
/// Any modification of a FunctionTemplate after first instantiation will trigger
/// a crash.
///
/// A FunctionTemplate can have properties, these properties are added to the
/// function object when it is created.
///
/// A FunctionTemplate has a corresponding instance template which is
/// used to create object instances when the function is used as a
/// constructor. Properties added to the instance template are added to
/// each object instance.
///
/// A FunctionTemplate can have a prototype template. The prototype template
/// is used to create the prototype object of the function.
#[repr(C)]
pub struct FunctionTemplate(Opaque);

impl FunctionTemplate {
  /// Creates a function template.
  pub fn new<'sc>(
    scope: &mut impl ToLocal<'sc>,
    callback: extern "C" fn(&FunctionCallbackInfo),
  ) -> Local<'sc, FunctionTemplate> {
    let ptr = unsafe { v8__FunctionTemplate__New(scope.isolate(), callback) };
    unsafe { scope.to_local(ptr) }.unwrap()
  }

  /// Returns the unique function instance in the current execution context.
  pub fn get_function<'sc>(
    &mut self,
    scope: &mut impl ToLocal<'sc>,
    mut context: Local<Context>,
  ) -> Option<Local<'sc, Function>> {
    unsafe {
      scope
        .to_local(v8__FunctionTemplate__GetFunction(&mut *self, &mut *context))
    }
  }
}

/// A JavaScript function object (ECMA-262, 15.3).
#[repr(C)]
pub struct Function(Opaque);

impl Function {
  // TODO: add remaining arguments from C++
  /// Create a function in the current execution context
  /// for a given FunctionCallback.
  pub fn new<'sc>(
    scope: &mut impl ToLocal<'sc>,
    mut context: Local<Context>,
    callback: extern "C" fn(&FunctionCallbackInfo),
  ) -> Option<Local<'sc, Function>> {
    unsafe { scope.to_local(v8__Function__New(&mut *context, callback)) }
  }

  pub fn call<'sc>(
    &mut self,
    scope: &mut impl ToLocal<'sc>,
    mut context: Local<Context>,
    mut recv: Local<Value>,
    arc: i32,
    argv: Vec<Local<Value>>,
  ) -> Option<Local<'sc, Value>> {
    let mut argv_: Vec<*mut Value> = vec![];
    for mut arg in argv {
      argv_.push(&mut *arg);
    }
    unsafe {
      scope.to_local(v8__Function__Call(
        &mut *self,
        &mut *context,
        &mut *recv,
        arc,
        argv_.as_mut_ptr(),
      ))
    }
  }
}