-- SecureHandlers.lua (Part of the Secure Handlers implementation)
--
-- Lua code to support the various handlers and templates which can execute
-- code in a secure, but restricted, environment.
--
-- Daniel Stephens
-- Nevin Flanagan
---------------------------------------------------------------------------

-- Local references to things so that they can't be subverted
local error = error;
local forceinsecure = forceinsecure;
local geterrorhandler = geterrorhandler;
local issecure = issecure;
local newproxy = newproxy;
local pcall = pcall;
local securecall = securecall;
local select = select;
local tostring = tostring;
local type = type;
local wipe = wipe;

local GetCursorInfo = GetCursorInfo;
local InCombatLockdown = InCombatLockdown;

local CallRestrictedClosure = CallRestrictedClosure;
local GetFrameHandle = GetFrameHandle;
local GetManagedEnvironment = GetManagedEnvironment;

-- SoftError(message)
-- Report an error message without stopping execution
local function SoftError_inner(message)
	local func = geterrorhandler();
	func(message);
end

local function SoftError(message)
	securecall(pcall, SoftError_inner, message);
end

---------------------------------------------------------------------------
-- Standard invocation for header executions and child executions


local function SecureHandler_Self_Execute(self, signature, body, ...)
	if (type(body) ~= "string") then return; end

	local selfHandle = GetFrameHandle(self, true);
	if (not selfHandle) then
		error("Invalid 'self' frame handle");
		return;
	end

	local environment = GetManagedEnvironment(self, true);

	return CallRestrictedClosure(signature, environment, selfHandle,
								 body, selfHandle, ...);
end

local function SecureHandler_Other_Execute(header, self, signature, body, ...)
	if (type(body) ~= "string") then return; end

	local controlHandle = GetFrameHandle(header, true);
	if (not controlHandle) then
		return( error("Invalid 'header' frame handle") );
	end

	local selfHandle = GetFrameHandle(self, true);
	if (not selfHandle) then return; end

	local environment = GetManagedEnvironment(header, true);
	return CallRestrictedClosure(signature, environment, controlHandle,
								 body, selfHandle, ...);
end

---------------------------------------------------------------------------
-- Script handlers for various header templates

function SecureHandler_OnSimpleEvent(self, snippetAttr)
	local body = self:GetAttribute(snippetAttr);
	if (body) then
		SecureHandler_Self_Execute(self, "self", body);
	end
end

function SecureHandler_OnClick(self, snippetAttr, button, down)
	local body = self:GetAttribute(snippetAttr);
	if (body) then
		SecureHandler_Self_Execute(self, "self,button,down",
								   body, button, down);
	end
end

function SecureHandler_OnMouseUpDown(self, snippetAttr, button)
	local body = self:GetAttribute(snippetAttr);
	if (body) then
		SecureHandler_Self_Execute(self, "self,button", body, button);
	end
end

function SecureHandler_OnMouseWheel(self, snippetAttr, delta)
	local body = self:GetAttribute(snippetAttr);
	if (body) then
		SecureHandler_Self_Execute(self, "self,delta", body, delta);
	end
end

function SecureHandler_StateOnAttributeChanged(self, name, value)
	local stateid = name:match("^state%-(.+)");
	if (stateid) then
		local body = self:GetAttribute("_onstate-" .. stateid);
		if (body) then
			SecureHandler_Self_Execute(self, "self,stateid,newstate",
									   body, stateid, value);
		end
	end
end

function SecureHandler_AttributeOnAttributeChanged(self, name, value)
	if (name:match("^_")) then
		return;
	end;

	local body = self:GetAttribute("_onattributechanged");
	if (body) then
		SecureHandler_Self_Execute(self, "self,name,value",
								   body, name, value);
	end
end

local function PickupAny(kind, target, detail, ...)
	if (kind == "clear") then
		ClearCursor();
		kind, target, detail = target, detail, ...;
	end

	if kind == 'action' then
		PickupAction(target);
	elseif kind == 'bag' then
		PickupBagFromSlot(target)
	elseif kind == 'bagslot' then
		PickupContainerItem(target, detail)
	elseif kind == 'inventory' then
		PickupInventoryItem(target)
	elseif kind == 'item' then
		PickupItem(target)
	elseif kind == 'macro' then
		PickupMacro(target)
	elseif kind == 'merchant' then
		PickupMerchantItem(target)
	elseif kind == 'petaction' then
		PickupPetAction(target)
	elseif kind == 'money' then
		PickupPlayerMoney(target)
	elseif kind == 'spell' then
		PickupSpell(target)
	elseif kind == 'companion' then
		PickupCompanion(target, detail)
	elseif kind == 'equipmentset' then
		PickupEquipmentSet(target);
	end
end

function SecureHandler_OnDragEvent(self, snippetAttr, button)
	local body = self:GetAttribute(snippetAttr);
	if (body) then
		PickupAny( SecureHandler_Self_Execute(self,
											  "self,button,kind,value,...",
											  body, button, GetCursorInfo()) );
	end
end

---------------------------------------------------------------------------
-- "Wrap" handlers for alternate dispatch on various conditions
-- such as OnClick, used for child handlers
--
-- All wrappers use ... to make sure the original handler gets all of
-- its arguments even if WoW is updated and this file is missed.

-- 'Marker object' used to trigger unwrap of wrap closure
local MAGIC_UNWRAP = newproxy();

local LOCAL_Wrapped_Handlers = {};
setmetatable(LOCAL_Wrapped_Handlers, { __mode = "k"; });

-- Create a closure to hold the data for a specific wrap
local function CreateWrapClosure(handler, header, preBody, postBody)
	local wrap;
	if (postBody) then
		wrap = function(self, ...)
					if (self == MAGIC_UNWRAP) then
						return header, preBody, postBody;
					end
					return handler(self, header, preBody, postBody, wrap, ...);
				end
	else
		wrap = function(self, ...)
				   if (self == MAGIC_UNWRAP) then
					   return header, preBody, nil;
				   end
				   return handler(self, header, preBody, nil, wrap, ...);
			   end
	end
	return wrap;
end

-- Save a hander against a specific wrap (securecall'ed for protection)
local function SaveWrapHandler(frame, script, wrap)
	LOCAL_Wrapped_Handlers[wrap] = frame:GetScript(script) or false;
end

-- Restore a hander from a specific wrap (securecall'ed for protection)
local function RestoreWrapHandler(frame, script, wrap)
	local old = LOCAL_Wrapped_Handlers[wrap];
	if (old == nil) then return; end
	if (old == false) then old = nil; end
	frame:SetScript(script, old);
	return true;
end

-- Create a new handler wrapper and configure it
--
-- frame   - the frame that has the script
-- script  - the script name (such as OnClick)
-- header  - the secure header that owns the 'wrap'
-- handler - the handler function that will process the event
-- preBody - the snippet to execute before the wrapped handler
-- postBody (optional) - the snippet to execute after the wrapped handler
--
-- The resulting closure is called as (self, ...)
--
-- The handler is invoked with (self, header, preBody, postBody, wrap, ...)
-- where 'wrap' is the wrap closure itself (also the key to the wrapped
-- handlers table)
local function CreateWrapper(frame, script, header, handler, preBody, postBody)
	local wrap = CreateWrapClosure(handler, header, preBody, postBody);
	securecall(SaveWrapHandler, frame, script, wrap);
	return wrap;
end

-- Reverse the wrap process, restoring the wrapped handler (does nothing
-- if the current handler is not wrapped)
local function RemoveWrapper(frame, script)
	local wrap = frame:GetScript(script);

	if (not issecure()) then
		-- not valid
		return;
	end

	if (not securecall(RestoreWrapHandler, frame, script, wrap)) then
		-- not valid
		return;
	end

	-- Extract header, preBody, postBody
	return wrap(MAGIC_UNWRAP);
end

-- Invoke the wrapped handler for a wrapper, passing in all arguments
local function SafeCallWrappedHandler(frame, wrap, ...)
	local handler = LOCAL_Wrapped_Handlers[wrap];
	if (type(handler) == "function") then
		local ok, err = pcall(handler, frame, ...);
		if (not ok) then
			SoftError(err);
		end
	end
end

-- Check that a given frame is eligible for wrapped execution
local function IsWrapEligible(frame)
	return (not InCombatLockdown()) or frame:IsProtected();
end

-- Wrapper handler for clicks
local function Wrapped_Click(self, header, preBody, postBody, wrap,
							 button, down, ...)
	local message, newbutton;

	if ( IsWrapEligible(self) ) then
		newbutton, message =
			SecureHandler_Other_Execute(header, self,
										"self,button,down", preBody,
										button, down);
		if (newbutton == false) then
			return;
		end
		if (newbutton) then
			button = tostring(newbutton);
		end
	end

	securecall(SafeCallWrappedHandler, self, wrap, button, down, ...);

	if (postBody and message ~= nil) then
		SecureHandler_Other_Execute(header, self,
									"self,message,button,down",
									postBody,
									message, button, down);
	end;
end

local function Wrapped_OnEnter(self, header, preBody, postBody, wrap,
							   motion, ...)
	local allow, message;
	if ( motion ) then
		self:SetAttribute("_wrapentered", true);
		if ( IsWrapEligible(self) ) then
			allow, message =
				SecureHandler_Other_Execute(header, self, "self",
											preBody);
		end

		if (allow == false) then
			return;
		end
	end

	securecall(SafeCallWrappedHandler, self, wrap, motion, ...);

	if (postBody and message ~= nil) then
		SecureHandler_Other_Execute(header, self, "self,message",
									postBody, message);
	end
end

local function Wrapped_OnLeave(self, header, preBody, postBody, wrap,
							   motion, ...)
	local allow, message;
	if ( motion and self:GetAttribute("_wrapentered")) then
		self:SetAttribute("_wrapentered", nil);
		if ( IsWrapEligible(self) ) then
			allow, message =
				SecureHandler_Other_Execute(header, self, "self",
											preBody);
			if (allow == false) then
				return;
			end
		end
	end

	securecall(SafeCallWrappedHandler, self, wrap, motion, ...);

	if (postBody and message ~= nil) then
		SecureHandler_Other_Execute(header, self, "self,message",
									postBody, message);
	end
end

local function CreateSimpleWrapper(beforeSignature, afterSignature)
	return function(self, header, preBody, postBody, wrap,
					...)
			   local allow, message;
			   if ( IsWrapEligible(self) ) then
				   allow, message =
					   SecureHandler_Other_Execute(header,
												   self, beforeSignature,
												   preBody, ...);
				   if (allow == false) then
					   return;
				   end
			   end

			   securecall(SafeCallWrappedHandler, self, wrap, ...);

			   if ( postBody and message ~= nil ) then
				   SecureHandler_Other_Execute(header,
											   self, afterSignature,
											   postBody, message, ...);
			   end
		   end;
end

local Wrapped_ShowHide = CreateSimpleWrapper("self", "self,message");

local Wrapped_MouseWheel = CreateSimpleWrapper("self,offset",
											   "self,message,offset");

local function Wrapped_Drag(self, header, preBody, postBody, wrap, ...)
	local message;
	if ( IsWrapEligible(self) ) then
		local selfHandle = GetFrameHandle(self, true);
		if (selfHandle) then
			local environment = GetManagedEnvironment(header, true);
			local controlHandle = GetFrameHandle(header, true, true);
			local button = ...;
			local pickupType, target, x1, x2, x3 =
				CallRestrictedClosure("self,button,kind,value,...",
									  environment,
									  controlHandle, preBody,
									  selfHandle, button,
									  GetCursorInfo());
			if (pickupType == false) then
				return;
			elseif (pickupType == "message") then
				message = target;
			elseif (pickupType) then
				PickupAny(pickupType, target, x1, x2, x3);
				return;
			end
		end
	end

	securecall(SafeCallWrappedHandler, self, wrap, ...);

	if ( postBody and message ~= nil ) then
		SecureHandler_Other_Execute(header, self,
									"self,message,button",
									postBody, message, ...);
	end
end

local function Wrapped_Attribute(self, header, preBody, postBody, wrap,
								 name, value, ...)
	local allow, message;
	if ( (not name:match("^_")) and IsWrapEligible(self) ) then
		allow, message =
			SecureHandler_Other_Execute(header, self,
										"self,name,value", preBody,
										name, value);
		if (allow == false) then
			return;
		end
	end

	securecall(SafeCallWrappedHandler, self, wrap, name, value, ...);

	if ( postBody and message ~= nil ) then
		SecureHandler_Other_Execute(header, self,
									"self,message,name,value",
									postBody, message, name, value);
	end
end

local LOCAL_Wrap_Handlers = {
	OnClick = Wrapped_Click;
	OnDoubleClick = Wrapped_Click;
	PreClick = Wrapped_Click;
	PostClick = Wrapped_Click;

	OnEnter = Wrapped_OnEnter;
	OnLeave = Wrapped_OnLeave;

	OnShow = Wrapped_ShowHide;
	OnHide = Wrapped_ShowHide;

	OnDragStart = Wrapped_Drag;
	OnReceiveDrag = Wrapped_Drag;

	OnMouseWheel = Wrapped_MouseWheel;

	OnAttributeChanged = Wrapped_Attribute;
};

---------------------------------------------------------------------------
-- External API helpers, all are driven off a single control frame
-- using OnAttributeChanged.

-- Quick sanity check that a frame looks like a frame
local function IsValidFrame(frame)
	return (type(frame) == "table") and (type(frame[0]) == "userdata");
end

-- 'Action' handler for most of the API methods, invoked somewhat indirectly
-- via attribute sets so as to allow secure execution (doesn't work from
-- combat for user code (or indeed for any code))
local function API_OnAttributeChanged(self, name, value)
	if (value == nil) then
		return;
	end

	if (InCombatLockdown()) then
		-- This shouldn't ever happen because API frame is protected,
		-- but just in case someone does something silly...
		error("Cannot use SecureHandlers API during combat");
		return;
	end


	-- _execute runs code in the context of a header
	if (name == "_execute") then
		local frame =  self:GetAttribute("_apiframe");
		self:SetAttribute("_execute", nil);
		if (type(value) ~= "string") then
			error("Invalid execute body");
			return;
		end
		-- Most validation is performed by SecureHandler_Self_Execute
		SecureHandler_Self_Execute(frame, "self", value);
		return;
	end

	-- _wrap wraps a script handler in a secure wrapper
	if (name == "_wrap") then
		local frame = self:GetAttribute("_apiframe");
		local header = self:GetAttribute("_apiheader");
		local preBody = self:GetAttribute("_apiprebody");
		local postBody = self:GetAttribute("_apipostbody");
		self:SetAttribute("_wrap", nil);
		if (type(value) ~= "string") then
			error("Invalid wrap script id");
		end
		if (not IsValidFrame(frame)) then
			error("Invalid wrap frame");
		end
		if (not IsValidFrame(header)) then
			error("Invalid header frame");
		end
		if (type(preBody) ~= "string") then
			error("Invalid pre-handler body");
		end
		if (postBody ~= nil and type(postBody) ~= "string") then
			error("Invalid post-handler body");
		end
		if (not select(2, header:IsProtected())) then
			error("Header frame must be explicitly protected");
		end
		local script = value;
		if (not frame:HasScript(script)) then
			error("Frame does not support script '" .. script .. "'");
		end
		if (not issecure()) then
			error("Wrap frame cannot be used");
		end
		local handler = LOCAL_Wrap_Handlers[value];
		if (not handler) then
			error("Unsupported script type '" .. value .. "'");
		end
		local wrapper = CreateWrapper(frame, value, header,
									  handler, preBody, postBody);
		frame:SetScript(script, wrapper);
		return;
	end

	-- _unwrap restores a previously wrapped handler
	if (name == "_unwrap") then
		local frame =  self:GetAttribute("_apiframe");
		local data =  self:GetAttribute("_apidata");
		if (data) then
			self:SetAttribute("_apidata", nil);
		end
		self:SetAttribute("_unwrap", nil);
		if (type(value) ~= "string") then
			error("Invalid unwrap script id");
		end
		if (not IsValidFrame(frame)) then
			error("Invalid unwrap frame");
		end
		local script = value;
		if (not frame:HasScript(script)) then
			error("Frame does not support script '" .. script .. "'");
		end
		local header, preBody, postBody = RemoveWrapper(frame, script);
		if (type(data) == "table") then
			forceinsecure();
			wipe(data);
			data[1] = frame;
			data[2] = script;
			data[3] = header;
			data[4] = preBody;
			data[5] = postBody;
		end
		return;
	end

	-- _frame-<label> creates a frame reference
	local frameid = name:match("^_frame%-(.+)");
	if (frameid) then
		local frame =  self:GetAttribute("_apiframe");
		self:SetAttribute(name, nil);
		if (not IsValidFrame(frame)) then
			error("Invalid destination frame");
			return;
		end
		if (not IsValidFrame(value)) then
			error("Invalid referenced frame");
			return;
		end

		local refid = "frameref-" .. frameid;
		local handle = GetFrameHandle(value);
		frame:SetAttribute(refid, handle);
		return;
	end
end

-- Frame used as both an attribute repository for API functions as well
-- as the OnUpdate timer source for timer and OnUpdate dispatch
local LOCAL_API_Frame = CreateFrame("Frame", "SecureHandlersUpdateFrame",
								nil, "SecureFrameTemplate");

LOCAL_API_Frame:SetScript("OnAttributeChanged", API_OnAttributeChanged);

-- Wrap the script on a frame to invoke snippets against a header
function SecureHandlerWrapScript(frame, script, header, preBody, postBody)
	if (not IsValidFrame(frame)) then
		error("Invalid frame");
		return;
	end
	if (type(script) ~= "string") then
		error("Invalid script id");
		return;
	end
	if (header and not IsValidFrame(header)) then
		error("Invalid header frame");
		return;
	end
	if (not select(2, header:IsProtected())) then
		error("Header frame must be explicitly protected");
		return;
	end
	if (type(preBody) ~= "string") then
		error("Invalid pre-handler body");
		return;
	end
	if (postBody ~= nil and type(postBody) ~= "string") then
		error("Invalid post-handler body");
		return;
	end
	LOCAL_API_Frame:SetAttribute("_apiframe", frame);
	LOCAL_API_Frame:SetAttribute("_apiheader", header);
	LOCAL_API_Frame:SetAttribute("_apiprebody", preBody);
	LOCAL_API_Frame:SetAttribute("_apipostbody", postBody);
	LOCAL_API_Frame:SetAttribute("_wrap", script);
end

local UNWRAP_TEMP_TABLE = {};

-- Remove previously applied wrapping, returning its details
function SecureHandlerUnwrapScript(frame, script)
	if (not IsValidFrame(frame)) then
		error("Invalid frame");
	end
	if (type(script) ~= "string") then
		error("Invalid script id");
	end
	wipe(UNWRAP_TEMP_TABLE);
	UNWRAP_TEMP_TABLE[1] = false;
	LOCAL_API_Frame:SetAttribute("_apiframe", frame);
	LOCAL_API_Frame:SetAttribute("_apidata", UNWRAP_TEMP_TABLE);
	LOCAL_API_Frame:SetAttribute("_unwrap", script);

	local chkFrame = UNWRAP_TEMP_TABLE[1];
	local chkScript = UNWRAP_TEMP_TABLE[2];
	local header = UNWRAP_TEMP_TABLE[3];
	local preBody = UNWRAP_TEMP_TABLE[4];
	local postBody = UNWRAP_TEMP_TABLE[5];

	if ((chkFrame ~= frame) or (chkScript ~= script)) then
		error("Unable to retrieve unwrap results");
		return;
	end
	wipe(UNWRAP_TEMP_TABLE);
	return header, preBody, postBody;
end

-- Execute a snippet against a header frame
function SecureHandlerExecute(frame, body)
	if (not IsValidFrame(frame)) then
		error("Invalid header frame");
		return;
	end
	if (not select(2, frame:IsProtected())) then
		error("Header frame must be explicitly protected");
		return;
	end
	if (type(body) ~= "string") then
		error("Invalid body");
		return;
	end
	LOCAL_API_Frame:SetAttribute("_apiframe", frame);
	LOCAL_API_Frame:SetAttribute("_execute", body);
end

-- Create a frame handle reference and store it against a frame
function SecureHandlerSetFrameRef(frame, label, refFrame)
	if (not IsValidFrame(frame)) then
		error("Invalid frame");
		return;
	end
	if (type(label) ~= "string") then
		error("Invalid body");
		return;
	end
	if (not IsValidFrame(refFrame)) then
		error("Invalid reference frame");
		return;
	end
	LOCAL_API_Frame:SetAttribute("_apiframe", frame);
	LOCAL_API_Frame:SetAttribute("_frame-" .. label, refFrame);
end

---------------------------------------------------------------------------
-- Helper Methods, these are just friendly wrappers for the
-- global functions.


local function SecureHandlerMethod_Execute(self, body)
	-- Kept as a wrapper for consistency
	return SecureHandlerExecute(self, body);
end

local function SecureHandlerMethod_WrapScript(self, frame, script,
											  preBody, postBody)
	-- Wrapped since args are in different order
	return SecureHandlerWrapScript(frame, script, self, preBody, postBody);
end

local function SecureHandlerMethod_UnwrapScript(self, frame, script)
	-- Wrapped since args are in different order
	return SecureHandlerUnwrapScript(frame, script);
end

local function SecureHandlerMethod_SetFrameRef(self, id, frame)
	-- Kept as a wrapper for consistency
	return SecureHandlerSetFrameRef(self, id, frame);
end

function SecureHandler_OnLoad(self)
	self.Execute = SecureHandlerMethod_Execute;
	self.WrapScript = SecureHandlerMethod_WrapScript;
	self.UnwrapScript = SecureHandlerMethod_UnwrapScript;
	self.SetFrameRef = SecureHandlerMethod_SetFrameRef;
end