/* Copyright (C) 2018 LiveCode Ltd.
 
 This file is part of LiveCode.
 
 LiveCode is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License v3 as published by the Free
 Software Foundation.
 
 LiveCode is distributed in the hope that it will be useful, but WITHOUT ANY
 WARRANTY; without even the implied warranty of MERCHANTABILITY or
 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 for more details.
 
 You should have received a copy of the GNU General Public License
 along with LiveCode.  If not see <http://www.gnu.org/licenses/>.  */

/**
This module provides utility handlers for converting to and from Emscripten types.

Description:

*/

module com.livecode.emscripten

use com.livecode.foreign

public foreign type JSObject binds to "MCJSObjectTypeInfo"

foreign handler MCEmscriptenPointerFromJSObject(in pObj as JSObject, out rPtr as Pointer) returns nothing binds to "<builtin>"
foreign handler MCEmscriptenPointerToJSObject(in pPtr as Pointer, out rObj as JSObject) returns nothing binds to "<builtin>"

__safe foreign handler MCEmscriptenEvaluateJavaScriptWithArguments(in pScript as String, in pArgs as List, out rResult as any) returns bool binds to "<builtin>"

public handler type JSEventHandler(in pEvent as JSObject) returns nothing
__safe foreign handler MCEmscriptenWrapJSEventHandler(in pHandler as JSEventHandler, out rRef as JSObject) returns bool binds to "<builtin>"

/**
Summary:    Convert a JavaScript object value to a pointer

Parameters:
pObj: The object to convert

Example:

public handler InitNativeButton()
	variable tButton as JSObject
	put EvalJavaScript("document.createElement('button')") into tButton

	variable tPointer as Pointer
	put PointerFromJSObject(tButton) into tPointer

	set my native layer to tPointer
end handler


Description:
Use <PointerFromJSObject> to convert a JavaScript object to a variable of type Pointer.

*/
public handler PointerFromJSObject(in pObj as JSObject) returns Pointer
	variable tPointer as Pointer
    unsafe
		MCEmscriptenPointerFromJSObject(pObj, tPointer)
    end unsafe
	return tPointer
end handler

/**
Summary:    Convert a Pointer into a JavaScript object

Parameters:
pPointer: The Pointer to convert

Returns:
An value of type JSObject

Example:
variable mButtonPointer as Pointer

public handler SetButtonText(in pText as String)
	variable tJSButton as JSObject
	put PointerToJSObject(mButtonPointer) into tJSButton
	
	EvalJavaScriptWithArguments("arguments[0].innerHTML = arguments[1]", [tJSButton, pText])
end handler
	 
Description:
Use <PointerToJSObject> to convert a variable of type Pointer to a JavaScript object.
*/
public handler PointerToJSObject(in pPointer as Pointer) returns JSObject
	variable tObject as JSObject
    unsafe
		MCEmscriptenPointerToJSObject(pPointer, tObject)
    end unsafe
	return tObject
end handler

/**
Summary:    Evaluate JavaScript code within the browser

Parameters:
pScript: The script to evaluate

Returns:
A value of any type

Example:
public handler GetInputText() returns String
	return EvalJavaScript("document.getElementById('myText').value")
end handler

Description:
Use <EvalJavaScript> to get the result of running a block of JavaScript code
*/
public handler EvalJavaScript(in pScript as String) returns optional any
	variable tResult as any
	if MCEmscriptenEvaluateJavaScriptWithArguments(pScript, [], tResult) then
		return tResult
	end if
	
	return nothing
end handler

/**
Summary:    Evaluate JavaScript code within the browser with arguments

Parameters:
pScript: The script to evaluate
pArgs: The list of arguments to pass to the script

Returns:
A value of any type

Example:
variable mButton as JSObject

public handler SetButtonText(in pText as String)
	EvalJavaScriptWithArguments("arguments[0].innerHTML = arguments[1]", [mButton, pText])
end handler
	 
Description:
Use <EvalJavaScriptWithArguments> to get the result of running a block of JavaScript code, where you need to pass values to the script.
*/
public handler EvalJavaScriptWithArguments(in pScript as String, in pArgs as List) returns optional any
	variable tResult as optional any
	if MCEmscriptenEvaluateJavaScriptWithArguments(pScript, pArgs, tResult) then
		return tResult
	end if
	
	return nothing
end handler

/**
Summary:    Wrap a LiveCode Builder handler within a JavaScript function, suitable for passing as an event handler.

Parameters:
pHandler: The handler to wrap

Returns:
A JavaScript function object, wrapping the handler

Example:
variable mButton as JSObject
variable mOnClickHandler as JSObject

private handler OnJSClick(pEvent as JSObject) returns nothing
	SetLabel("Clicked!")
end handler

private handler SetJSEventHandler(in pElement as JSObject, in pEvent as String, in pHandler as JSObject)
	EvalJavaScriptWithArguments("arguments[0].addEventListener(arguments[1], arguments[2]);", [pElement, pEvent, pHandler])
end handler

private handler SetupEventHandler()
	put HandlerAsJSFunction(OnJSClick) into mOnClickHandler
	SetJSEventHandler(mButton, "click", mOnClickHandler)
end handler
	 
Description:
Use <HandlerAsJSFunction> to convert a handler reference to a JavaScript function object reference.
*/
public handler HandlerAsJSFunction(in pHandler as JSEventHandler) returns JSObject
	variable tJSHandler as JSObject
	MCEmscriptenWrapJSEventHandler(pHandler, tJSHandler)
	return tJSHandler
end handler

end module