//********************************** Banshee Engine (www.banshee3d.com) **************************************************//
//**************** Copyright (c) 2016 Marko Pintera (marko.pintera@gmail.com). All rights reserved. **********************//
#include "String/BsUnicode.h"
#include "Platform/BsPlatform.h"
#include "RenderAPI/BsRenderWindow.h"
#include "BsLinuxDragAndDrop.h"
#include "BsLinuxWindow.h"
#include "BsLinuxPlatform.h"
#include <X11/Xatom.h>
#include <X11/Xlib.h>

namespace bs
{
	::Display* LinuxDragAndDrop::sXDisplay = nullptr;
	bool LinuxDragAndDrop::sDragActive = false;
	Vector<OSDropTarget*> LinuxDragAndDrop::sTargets;
	Mutex LinuxDragAndDrop::sMutex;
	INT32 LinuxDragAndDrop::sDNDVersion = 0;
	::Window LinuxDragAndDrop::sDNDSource = None;
	Vector2I LinuxDragAndDrop::sDragPosition;
	Vector<LinuxDragAndDrop::DragAndDropOp> LinuxDragAndDrop::sQueuedOperations;
	Vector<OSDropTarget*> LinuxDragAndDrop::sTargetsToRegister;
	Vector<OSDropTarget*> LinuxDragAndDrop::sTargetsToUnregister;

	Atom LinuxDragAndDrop::sXdndAware;
	Atom LinuxDragAndDrop::sXdndSelection;
	Atom LinuxDragAndDrop::sXdndEnter;
	Atom LinuxDragAndDrop::sXdndLeave;
	Atom LinuxDragAndDrop::sXdndPosition;
	Atom LinuxDragAndDrop::sXdndStatus;
	Atom LinuxDragAndDrop::sXdndDrop;
	Atom LinuxDragAndDrop::sXdndFinished;
	Atom LinuxDragAndDrop::sXdndActionCopy;
	Atom LinuxDragAndDrop::sXdndTypeList;

	struct X11Property
	{
		UINT8* data;
		INT32 format;
		UINT32 count;
		Atom type;
	};

	// Results must be freed using XFree
	X11Property readX11Property(::Display *display, ::Window window, Atom type)
	{
		X11Property output;

		unsigned long bytesLeft;
		int bytesToFetch = 0;

		do
		{
			if(output.data != nullptr)
				XFree(output.data);

			XGetWindowProperty(display, window, type, 0, bytesToFetch, False, AnyPropertyType,
					&output.type, &output.format, (unsigned long*)&output.count, &bytesLeft, &output.data);
			bytesToFetch += bytesLeft;

		} while(bytesLeft != 0);

		return output;
	}

	/**
	 * Decodes percent (%) encoded characters in an URI to actual characters. Characters are decoded into the input string.
	 */
	void decodeURI(char* uri)
	{
		if(uri == nullptr)
			return;

		UINT32 length = (UINT32)strlen(uri);
		UINT8 decodedChar = '\0';
		UINT32 writeIdx = 0;
		UINT32 decodeState = 0; // 0 - Not decoding, 1 - found a % char, 2- found a % and following char

		for(UINT32 i = 0; i < length; i++)
		{
			// Not currently decoding, check for % or write as-is
			if(decodeState == 0)
			{
				// Potentially an encoded char, start decode
				if(uri[i] == '%')
				{
					decodedChar = '\0';
					decodeState = 1;
				}
				else // Normal char, write as-is
				{
					uri[writeIdx] = uri[i];
					writeIdx++;
				}
			}
			else // Currently decoding, check if following chars are valid
			{
				char isa = uri[i] >= 'a' && uri[i] <= 'f';
				char isA = uri[i] >= 'A' && uri[i] <= 'F';
				char isn = uri[i] >= '0' && uri[i] <= '9';

				bool isHex = isa || isA || isn;
				if(!isHex)
				{
					// If not a hex, this can't be an encoded character. Write the last "decodeState" characters as normal
					for(UINT32 j = decodeState; j > 0; j--)
					{
						uri[writeIdx] = uri[i - j];
						writeIdx++;
					}

					decodeState = 0;
				}
				else
				{
					// Decode the hex character into a number
					char offset = '\0';
					if(isn)
						offset = 0 - '0';
					else if(isa)
						offset = 10 - 'a';
					else if(isA)
						offset = 10 - 'A';

					decodedChar |= (uri[i] + offset) << ((2 - decodeState) * 4);

					// Check if done decoding and write
					if(decodeState == 2)
					{
						uri[writeIdx] = decodedChar;
						writeIdx++;
						decodeState = 0;
					}
					else // decodeState == 1
						decodeState = 2;
				}
			}
		}

		uri[writeIdx] = '\0';
	}

	char* convertURIToLocalPath(char* uri)
	{
		if (memcmp(uri, "file:/", 6) == 0)
			uri += 6;
		else if (strstr(uri, ":/") != nullptr)
			return nullptr;

		bool isLocal = uri[0] != '/' || (uri[0] != '\0' && uri[1] == '/');

		// Ignore hostname
		if (!isLocal && uri[0] == '/' && uri[2] != '/')
		{
			char* hostnameEnd = strchr(uri+1, '/');
			if (hostnameEnd != nullptr)
			{
				char hostname[257];
				if (gethostname(hostname, 255) == 0)
				{
					hostname[256] = '\0';
					if (memcmp(uri+1, hostname, hostnameEnd - (uri+1)) == 0)
					{
						uri = hostnameEnd + 1;
						isLocal = true;
					}
				}
			}
		}

		if (isLocal)
		{
			decodeURI(uri);
			if (uri[1] == '/')
				uri++;
			else
				uri--;

			return uri;
		}

		return nullptr;
	}

	void LinuxDragAndDrop::startUp(::Display* xDisplay)
	{
#define INIT_ATOM(name)		s##name = XInternAtom(xDisplay, #name, False);

		INIT_ATOM(XdndAware)
		INIT_ATOM(XdndSelection)
		INIT_ATOM(XdndEnter)
		INIT_ATOM(XdndLeave)
		INIT_ATOM(XdndPosition)
		INIT_ATOM(XdndStatus)
		INIT_ATOM(XdndDrop)
		INIT_ATOM(XdndFinished)
		INIT_ATOM(XdndActionCopy)
		INIT_ATOM(XdndTypeList)
		INIT_ATOM(PRIMARY)

#undef INIT_ATOM
	}

	void LinuxDragAndDrop::shutDown()
	{
		// Do nothing
	}

	void LinuxDragAndDrop::makeDNDAware(::Window xWindow)
	{
		UINT32 dndVersion = 5;
		XChangeProperty(sXDisplay, xWindow, sXdndAware, XA_ATOM, 32, PropModeReplace, (unsigned char*)&dndVersion, 1);
	}

	OSDropTarget& LinuxDragAndDrop::createDropTarget(const RenderWindow* window, INT32 x, INT32 y, UINT32 width,
		UINT32 height)
	{
		Lock lock(sMutex);
		OSDropTarget* newDropTarget = bs_new<OSDropTarget>(window, x, y, width, height);
		sTargetsToRegister.push_back(newDropTarget);

		return *newDropTarget;
	}

	void LinuxDragAndDrop::destroyDropTarget(OSDropTarget& target)
	{
		Lock lock(sMutex);
		sTargetsToUnregister.push_back(&target);
	}

	bool LinuxDragAndDrop::handleClientMessage(XClientMessageEvent& event)
	{
		// First handle any queued registration/unregistration
		{
			Lock lock(sMutex);

			for(auto& target : sTargetsToRegister)
				sTargets.push_back(target);

			for(auto& target : sTargetsToUnregister)
			{
				// Remove any operations queued for this target
				for(auto iter = sQueuedOperations.begin(); iter !=sQueuedOperations.end();)
				{
					if(iter->target == target)
						iter = sQueuedOperations.erase(iter);
					else
						++iter;
				}

				auto iterFind = std::find(sTargets.begin(), sTargets.end(), target);
				if (iterFind != sTargets.end())
					sTargets.erase(iterFind);

				bs_delete(target);
			}
		}

		// Source window notifies us a drag has just entered our window area
		if(event.message_type == sXdndEnter)
		{
			sDNDSource = (::Window)event.data.l[0];
			bool isList = (event.data.l[1] & 1) != 0;
			sDNDVersion = (INT32)(event.data.l[1] >> 24);

			// Get a list of properties are determine if there are any relevant ones
			Atom* propertyList = nullptr;
			UINT32 numProperties = 0;

			// If more than 3 properties we need to read the list property to get them all
			if(isList)
			{
				X11Property property = readX11Property(sXDisplay, sDNDSource, sXdndTypeList);

				propertyList = (Atom*)property.data;
				numProperties = property.count;
			}
			else
			{
				propertyList = bs_stack_alloc<Atom>(3);

				for(int i = 0; i < 3; i++)
				{
					if(event.data.l[2 + i])
					{
						propertyList[i] = (Atom)event.data.l[2 + i];
						numProperties++;
					}
				}
			}

			// Scan the list for URI list (file list), which is the only one we support (currently)
			bool foundSupportedType = false;
			for (UINT32 i = 0; i < numProperties; ++i)
			{
				char* name = XGetAtomName(sXDisplay, propertyList[i]);
				if(strcmp(name, "text/uri-list") == 0)
				{
					sDNDType = propertyList[i];

					XFree(name);
					foundSupportedType = true;
					break;
				}

				XFree(name);
			}

			// Free the property list
			if(isList)
				XFree(propertyList);
			else
				bs_stack_free(propertyList);

			sDragActive = foundSupportedType;
		}
		// Cursor moved while drag is active (also includes the initial cursor activity when drag entered)
		else if(event.message_type == sXdndPosition)
		{
			::Window source = (::Window)event.data.l[0];

			sDragPosition.x = (INT32)((event.data.l[2] >> 16) & 0xFFFF);
			sDragPosition.y = (INT32)((event.data.l[2]) & 0xFFFF);

			// Respond with a status message, we either accept or reject the dnd
			XClientMessageEvent response;
			bs_zero_out(response);

			response.type = ClientMessage;
			response.display = event.display;
			response.window = source;
			response.message_type = sXdndStatus;
			response.format = 32;
			response.data.l[0] = event.window;
			response.data.l[1] = 0; // Reject drop by default
			response.data.l[2] = 0; // Empty rectangle
			response.data.l[3] = 0; // Empty rectangle
			response.data.l[4] = sXdndActionCopy;

			if(sDragActive)
			{
				for(auto& dropTarget : sTargets)
				{
					LinuxWindow* linuxWindow;
					dropTarget->_getOwnerWindow()->getCustomAttribute("WINDOW", &linuxWindow);
					::Window xWindow = linuxWindow->_getXWindow();

					if(xWindow == event.window)
					{
						Vector2I windowPos = linuxWindow->screenToWindowPos(sDragPosition);
						if(dropTarget->_isInside(windowPos))
						{
							// Accept drop
							response.data.l[1] = 1;

							if(dropTarget->_isActive())
							{
								Lock lock(sMutex);
								sQueuedOperations.push_back(DragAndDropOp(DragAndDropOpType::DragOver, dropTarget,
									windowPos));
							}
							else
							{
								Lock lock(sMutex);
								sQueuedOperations.push_back(DragAndDropOp(DragAndDropOpType::Enter, dropTarget,
										windowPos));
							}

							dropTarget->_setActive(true);
						}
						else
						{
							// Cursor left previously active target's area
							if(dropTarget->_isActive())
							{
								{
									Lock lock(sMutex);
									sQueuedOperations.push_back(DragAndDropOp(DragAndDropOpType::Leave, dropTarget));
								}

								dropTarget->_setActive(false);
							}
						}
					}
				}
			}

			XSendEvent(sXDisplay, source, False, NoEventMask, (XEvent*)&response);
			XFlush(sXDisplay);
		}
		// Cursor left the target window, or the drop was rejected
		else if(event.message_type == sXdndLeave)
		{
			for(auto& dropTarget : sTargets)
			{
				if(dropTarget->_isActive())
				{
					{
						Lock lock(sMutex);
						sQueuedOperations.push_back(DragAndDropOp(DragAndDropOpType::Leave, dropTarget));
					}

					dropTarget->_setActive(false);
				}
			}

			sDragActive = false;
		}
		else if(event.message_type == sXdndDrop)
		{
			::Window source = (::Window)event.data.l[0];
			bool dropAccepted = false;

			if(sDragActive)
			{
				for (auto& dropTarget : sTargets)
				{
					if (dropTarget->_isActive())
						dropAccepted = true;
				}
			}

			if(dropAccepted)
			{
				Time timestamp;
				if(sDNDVersion >= 1)
					timestamp = (Time)event.data.l[2];
				else
					timestamp = CurrentTime;

				XConvertSelection(sXDisplay, sXdndSelection, sDNDType, sPRIMARY, LinuxPlatform::getMainXWindow(), timestamp);

				// Now we wait for SelectionNotify
			}
			else
			{
				// Respond with a status message that we reject the drop
				XClientMessageEvent response;
				bs_zero_out(response);

				response.type = ClientMessage;
				response.display = event.display;
				response.window = source;
				response.message_type = sXdndFinished;
				response.format = 32;
				response.data.l[0] = LinuxPlatform::getMainXWindow();
				response.data.l[1] = 0;
				response.data.l[2] = 0;
				response.data.l[3] = None;
				response.data.l[4] = None;

				XSendEvent(sXDisplay, source, False, NoEventMask, (XEvent*)&response);
				XFlush(sXDisplay);

				sDragActive = false;
			}
		}
		else
			return false;

		return true;
	}

	bool LinuxDragAndDrop::handleSelectionNotify(XSelectionEvent& event)
	{
		if(event.target != sDNDType)
			return false;

		if(!sDragActive)
			return true;

		// Read data
		X11Property property = readX11Property(sXDisplay, LinuxPlatform::getMainXWindow(), sXdndTypeList);
		if(property.format == 8)
		{
			// Assuming this is a file list, since we rejected any other drop type
			Vector<WString> filePaths;

			char* token = strtok((char*)property.data, "\r\n");
			while(token != nullptr)
			{
				char* filePath = convertURIToLocalPath(token);
				if(filePath != nullptr)
					filePaths.push_back(UTF8::toWide(filePath));

				token = strtok(nullptr, "\r\n");
			}

			for(auto& target : sTargets)
			{
				if(!target->_isActive())
					continue;

				LinuxWindow* linuxWindow;
				target->_getOwnerWindow()->getCustomAttribute("WINDOW", &linuxWindow);

				Vector2I windowPos = linuxWindow->screenToWindowPos(sDragPosition);

				Lock lock(sMutex);
				sQueuedOperations.push_back(DragAndDropOp(DragAndDropOpType::Drop, target, windowPos, filePaths));

				target->_setActive(false);
			}
		}

		XFree(property.data);

		// Respond with a status message that we accepted the drop
		XClientMessageEvent response;
		bs_zero_out(response);

		response.type = ClientMessage;
		response.display = event.display;
		response.window = sDNDSource;
		response.message_type = sXdndFinished;
		response.format = 32;
		response.data.l[0] = LinuxPlatform::getMainXWindow();
		response.data.l[1] = 1;
		response.data.l[2] = sXdndActionCopy;
		response.data.l[3] = None;
		response.data.l[4] = None;

		XSendEvent(sXDisplay, sDNDSource, False, NoEventMask, (XEvent*)&response);
		XFlush(sXDisplay);

		sDragActive = false;

		return true;
	}

	void LinuxDragAndDrop::update()
	{
		Vector<DragAndDropOp> operations;

		{
			Lock lock(sMutex);
			std::swap(operations, sQueuedOperations);
		}

		for(auto& op : operations)
		{
			switch(op.type)
			{
			case DragAndDropOpType::Enter:
				op.target->onEnter(op.position.x, op.position.y);
				break;
			case DragAndDropOpType::DragOver:
				op.target->onDragOver(op.position.x, op.position.y);
				break;
			case DragAndDropOpType::Drop:
				op.target->_setFileList(op.fileList);
				op.target->onDrop(op.position.x, op.position.y);
				break;
			case DragAndDropOpType::Leave:
				op.target->_clear();
				op.target->onLeave();
				break;
			}
		}
	}
}