//! This module contains all browser related handles and stuff.


use browser_window_ffi::*;
use futures_channel::oneshot;
use std::{
	error::Error,
	ffi::CStr,
	fmt,
	future::Future,
	marker::PhantomData,
	ops::Deref,
	os::raw::*,
	rc::Rc
};

use crate::application::*;
use crate::common::*;

pub mod builder;

pub use builder::{BrowserWindowBuilder, Source};


//type BrowserJsCallbackData<'a> = Box<dyn FnOnce(Browser, Result<String, JsEvaluationError>) + 'a>;

//type BrowserJsThreadedCallbackData<'a> = SendBoxFnOnce<'a,(BrowserHandle, Result<String, JsEvaluationError>),()>;


/// The future that dispatches a closure on the GUI thread.

pub type BrowserDelegateFuture<'a,R> = DelegateFuture<'a, BrowserWindowHandle, R>;



/// An owned browser window handle.

/// When this handle goes out of scope, its resource get scheduled for cleanup.

// If the user closes the window, this handle remains valid.

// Also, if you lose this handle, window destruction and cleanup is only done when the user actually closes it.

// So you don't have to worry about lifetimes and/or propper destruction of the window either.

pub struct BrowserWindow {
	pub(in super) handle: BrowserWindowHandle,
	_not_send: PhantomData<Rc<()>>
}

/// A thread-safe handle to a browser window.

/// It allows you to dispatch code to the GUI thread.

// It provides the same functionality as `BrowserWindow`.

// However, each function is async: it runs on the GUI thread, and returns when it is done.

pub struct BrowserWindowThreaded {
	pub(in super) handle: BrowserWindowHandle
}
unsafe impl Sync for BrowserWindowThreaded {}

/// This is a handle to an existing browser window.

#[derive(Clone, Copy)]
pub struct BrowserWindowHandle {
	pub(in super) ffi_handle: *mut bw_BrowserWindow
}
unsafe impl Send for BrowserWindowHandle {}

/// An error that may occur when evaluating or executing JavaScript code.

#[derive(Debug)]
pub struct JsEvaluationError {
	message: String
	// TODO: Add line and column number files, and perhaps even more info about the JS error

}

pub trait OwnedBrowserWindow {
	fn handle( &self ) -> BrowserWindowHandle;
}



impl BrowserWindow {

	/*fn from_ffi_handle( ptr: *mut bw_BrowserWindow ) -> Self {
		Self {
			handle: BrowserWindowHandle::new( ptr ),
			_not_send: PhantomData
		}
	}*/

	fn new( handle: BrowserWindowHandle ) -> Self {
		Self {
			handle: handle,
			_not_send: PhantomData
		}
	}
}

impl Deref for BrowserWindow {
	type Target = BrowserWindowHandle;

	fn deref( &self ) -> &Self::Target {
		&self.handle
	}
}

impl Drop for BrowserWindow {
	fn drop( &mut self ) {
		unsafe { bw_BrowserWindow_drop( self.handle.ffi_handle ) }
	}
}

impl HasAppHandle for BrowserWindow {

	fn app_handle( &self ) -> ApplicationHandle {
		self.handle.app_handle()
	}
}

impl OwnedBrowserWindow for BrowserWindow {
	fn handle( &self ) -> BrowserWindowHandle {
		self.handle.clone()
	}
}



impl BrowserWindowHandle {

	/// Returns the application handle associated with this browser window.

	pub fn app( &self ) -> ApplicationHandle {
		ApplicationHandle::new( unsafe { bw_BrowserWindow_getApp( self.ffi_handle ) } )
	}

	/// Closes the browser.

	// The browser will be freed from memory when the last handle to it gets dropped.

	pub fn close( self ) {
		unsafe { bw_BrowserWindow_close( self.ffi_handle ); }
	}

	/// Executes the given javascript code and returns the output as a string.

	/// If you don't need the result, see `exec_js`.

	pub async fn eval_js( &self, js: &str ) -> Result<String, JsEvaluationError> {
		//

		let (tx, rx) = oneshot::channel::<Result<String, JsEvaluationError>>();

		self._eval_js( js, |_, result| {

			// The callback of `_eval_js` is not necessarily called from our GUI thread, so this is a quickfix to make that safe.

			// Otherwise, the `panic` may not be propegated correctly!

			// FIXME: Call this result callback closure form the GUI thread from within the CEF implementation.

			if let Err(_) = tx.send( result ) {
				panic!("Unable to send JavaScript result back")
			}
		} );

		rx.await.unwrap()
	}

	/// Executes the given JavaScript code, and provides the output via a callback.

	///

	/// # Arguments

	/// * `on_complete` - The closure that will be called when the output is ready.

	fn _eval_js<'a,H>( &self, js: &str, on_complete: H ) where
		H: FnOnce( BrowserWindowHandle, Result<String, JsEvaluationError> ) + 'a
	{
		let data_ptr: *mut H = Box::into_raw(
			Box::new( on_complete )
		);

		unsafe { bw_BrowserWindow_evalJs(
			self.ffi_handle,
			js.into(),
			ffi_eval_js_callback::<H>,
			data_ptr as _
		) };
	}

	/// Executes the given javascript code without waiting on it to finish.

	pub fn exec_js( &self, js: &str ) {
		self._eval_js( js, |_,_|{} );
	}

	/// Causes the browser to navigate to the given url.

	pub fn navigate( &self, url: &str ) {
		unsafe { bw_BrowserWindow_navigate( self.ffi_handle, url.into() ) };
	}
}



impl BrowserWindowThreaded {

	/// The thread-safe application handle associated with this browser window.

	pub fn app( &self ) -> ApplicationHandleThreaded {
		ApplicationHandleThreaded::from_ffi_handle( unsafe { bw_BrowserWindow_getApp( self.handle.ffi_handle ) } )
	}

	/// Closes the browser.

	pub fn close( self ) -> bool {
		self.dispatch(|bw| {
			bw.close()
		})
	}

	/// Executes the given closure within the GUI thread, and return the value that the closure returned.

	/// Also see `ApplicationThreaded::delegate`.

	///

	/// The function signature is practically the same as:

	/// ```rust

	/// pub async fn delegate<'a,F,R>( &self, func: F ) -> Result<R, DelegateError> where

	/// 	F: FnOnce( BrowserWindowHandle ) -> R + Send + 'a,

	/// 	R: Send { //...

	/// ```

	pub fn delegate<'a,F,R>( &self, func: F ) -> BrowserDelegateFuture<'a,R> where
		F: FnOnce( BrowserWindowHandle ) -> R + Send + 'a,
		R: Send
	{
		BrowserDelegateFuture::new( self.handle.clone(), func )
	}

	/// Executes the given async closure `func` on the GUI thread, and gives back the result when done.

	/// Also see `ApplicationThreaded::delegate_async`.

	pub fn delegate_async<'a,C,F,R>( &self, func: C ) -> DelegateFutureFuture<'a,R> where
		C: FnOnce( BrowserWindowHandle ) -> F + Send + 'a,
		F: Future<Output=R>,
		R: Send + 'static
	{
		let handle = self.handle.clone();
		DelegateFutureFuture::new( self.app().handle.clone(), async move {
			func( handle.into() ).await
		})
	}

	/// Executes the given close on the GUI thread.

	/// See also `Application::dispatch`.

	pub fn dispatch<'a,F>( &self, func: F ) -> bool where
		F:  FnOnce( BrowserWindowHandle ) + Send + 'a
	{
		let handle = self.handle;

		self.app().dispatch(move |_| {
			func( handle );
		})
	}

	/*fn _eval_js<'a,H>( &self, js: &str, on_complete: H ) where
		H: FnOnce( BrowserWindowHandle, Result<String, JsEvaluationError> ) + Send + 'a
	{
		let data_ptr: *mut H = Box::into_raw(
			Box::new( on_complete )
		);

		unsafe { bw_BrowserWindow_evalJsThreaded(
			self.handle.ffi_handle,
			js.into(),
			ffi_eval_js_threaded_callback::<H>,
			data_ptr as _
		) };
	}*/

	fn new( handle: BrowserWindowHandle ) -> Self {
		Self {
			handle
		}
	}
}

impl Drop for BrowserWindowThreaded {
	fn drop( &mut self ) {
		unsafe { bw_Application_dispatch( self.app().handle.ffi_handle, ffi_free_browser_window, self.handle.ffi_handle as _ ); }
	}
}

impl HasAppHandle for BrowserWindowThreaded {

	fn app_handle( &self ) -> ApplicationHandle {
		self.handle.app_handle()
	}
}

impl OwnedBrowserWindow for BrowserWindowThreaded {
	fn handle( &self ) -> BrowserWindowHandle {
		self.handle.clone()
	}
}



impl BrowserWindowHandle {
	fn new( ffi_handle: *mut bw_BrowserWindow ) -> Self {
		Self {
			ffi_handle: ffi_handle
		}
	}
}

impl HasAppHandle for BrowserWindowHandle {

	fn app_handle( &self ) -> ApplicationHandle {
		ApplicationHandle::new(
			unsafe { bw_BrowserWindow_getApp( self.ffi_handle ) }
		)
	}
}



impl JsEvaluationError {
	pub(in super) unsafe fn new( err: *const bw_Err ) -> Self {

		let msg_ptr = ((*err).alloc_message)( (*err).code, (*err).data );
		let cstr = CStr::from_ptr( msg_ptr );
		let message: String = cstr.to_string_lossy().into();

		Self {
			message: message
		}
	}
}

impl Error for JsEvaluationError {
	fn source(&self) -> Option<&(dyn Error + 'static)> { None }
}

impl fmt::Display for JsEvaluationError {

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

		write!(f, "{}", self.message.as_str())
	}
}



/// Callback for dropping a browser window.

/// This gets dispatch to the GUI thread when a `BrowserWindowThreaded` handle gets dropped.

unsafe extern "C" fn ffi_free_browser_window( _app: *mut bw_Application, data: *mut c_void ) {
	bw_BrowserWindow_drop( data as *mut bw_BrowserWindow );
}

unsafe extern "C" fn ffi_eval_js_callback<H>( bw: *mut bw_BrowserWindow, cb_data: *mut c_void, _result: *const c_char, error: *const bw_Err ) where
	H: FnOnce(BrowserWindowHandle, Result<String, JsEvaluationError>)
{
	let data_ptr = cb_data as *mut H;
	let data = Box::from_raw( data_ptr );

	let (handle, result) = ffi_eval_js_callback_result( bw, _result, error );

	(*data)( handle, result );
}

unsafe fn ffi_eval_js_callback_result(
	bw: *mut bw_BrowserWindow,
	result: *const c_char,
	error: *const bw_Err
) -> ( BrowserWindowHandle, Result<String, JsEvaluationError> ) {


	// Construct a result value depending on whether the result or error parameters are set

	let result_val: Result<String, JsEvaluationError> = if error.is_null() {
		let result_str = CStr::from_ptr( result ).to_string_lossy().to_owned().to_string();
		Ok( result_str )
	}
	else {
		Err( JsEvaluationError::new( error ) )
	};

	let handle = BrowserWindowHandle::new( bw );

	// return

	( handle, result_val )
}

// Callback for catching JavaScript results.

//

// # Warning

// This may get invoked from another thread than the GUI thread, depending on the implementation of the browser engine.

/*unsafe extern "C" fn ffi_eval_js_threaded_callback<H>( bw: *mut bw_BrowserWindow, cb_data: *mut c_void, _result: *const c_char, error: *const bw_Err ) where
	H: FnOnce(BrowserHandle, Result<String, JsEvaluationError>) + Send
{
	let data_ptr = cb_data as *mut H;
	let data = Box::from_raw( data_ptr );

	let (handle, result) = ffi_eval_js_callback_result( bw, _result, error );

	(*data)( handle, result );
}*/