/*
    Title:      Poly/ML Console Window.

    Copyright (c) 2000, 2015 David C. J. Matthews

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License version 2.1 as published by the Free Software Foundation.
    
    This library 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
    Lesser General Public License for more details.
    
    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

*/

#ifdef HAVE_CONFIG_H
#include "config.h"
#elif defined(_WIN32)
#include "winconfig.h"
#else
#error "No configuration file"
#endif

#ifdef HAVE_STDIO_H
#include <stdio.h>
#endif

#ifdef HAVE_WINDOWS_H
#include <windows.h>
#endif

#ifdef HAVE_TCHAR_H
#include <tchar.h>
#endif

#ifdef HAVE_IO_H
#include <io.h>
#endif

#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif

#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif

#ifdef HAVE_ASSERT_H
#include <assert.h>
#define ASSERT(x)   assert(x)
#else
#define ASSERT(x)
#endif

#include "../resource.h"
#include "mpoly.h"
#include "PolyControl.h"
#include "diagnostics.h"
#include "mpoly.h"
#include "run_time.h"
#include "sighandler.h"
#include "console.h"
#include "../polyexports.h"
#include "processes.h"
#include "polystring.h"

/*
This module takes the place of the Windows console which
has a number of problems, apart from not being a pleasant
user interface.  It creates a main window containing an edit
control, which it has to sub-class so that we can receive all
the characters as they are typed.
I've written this in C using the direct Windows calls to make
it fairly independent of the compiler.  It would definitely be
simpler and cleaner written in C++ using MFC.
DCJM 30/5/2000.
*/

#ifdef _MSC_VER
// Don't tell me about ISO C++ changes.
#pragma warning(disable:4996)
#endif

HWND hMainWindow = NULL; // Main window - exported.
HINSTANCE hApplicationInstance;     // Application instance (exported)
static HANDLE  hReadFromML; // Handles to pipe from ML thread
static WNDPROC  wpOrigEditProc; // Saved window proc.
static BOOL fAtEnd;         // True if we are at the end of the window
static HWND hEditWnd;       // Edit sub-window
static CHAR *pchInputBuffer; // Buffer to text read.
static int  nBuffLen;       // Length of input buffer.
static int  nNextPosn;      // Position to add input. (<= nBuffLen)
static int  nAvailable;     // Position of "committed" input (<= nNextPosn)
static int  nReadPosn;      // Position of last read (<= nAvailable)
static CRITICAL_SECTION csIOInterlock;
HANDLE hInputEvent;  // Signalled when input is available.
static HWND hDDEWindow;     // Window to handle DDE requests from ML thread.
HANDLE hOldStdin = INVALID_HANDLE_VALUE;

static LPTSTR*  lpArgs = 0; // Argument list.
static int      nArgs = 0;
static int initDDEControl(const TCHAR *lpszName);
static void uninitDDEControl(void);
static DWORD dwDDEInstance;

static int nInitialShow; // Value of nCmdShow passed in.
static bool isActive = false;

// Default DDE service name.
#define POLYMLSERVICE   _T("PolyML")

#ifdef UNICODE
#define DDECODEPAGE CP_WINUNICODE
#else
#define DDECODEPAGE CP_WINANSI
#endif


/* Messages interpreted by the main window thread. */
#define WM_ADDTEXT      WM_APP
#define WM_DDESTART     (WM_APP+1)
#define WM_DDESTOP      (WM_APP+2)
#define WM_DDEEXEC      (WM_APP+3)
#define WM_DDESERVINIT      (WM_APP+4)

/* These functions are called by the I/O routines to test for input and
   to read from the keyboard. */
bool isConsoleInput(void)
{
    if (! isActive) { ShowWindow(hMainWindow, nInitialShow); isActive = true; }
    EnterCriticalSection(&csIOInterlock);
    bool nRes = nAvailable != nReadPosn;
    LeaveCriticalSection(&csIOInterlock);
    return nRes;
}

/* Read characters from the input.  Only returns zero on EOF. */
unsigned getConsoleInput(char *buff, int nChars)
{
    unsigned nRes = 0;
    if (! isActive) { ShowWindow(hMainWindow, nInitialShow); isActive = true; }
    EnterCriticalSection(&csIOInterlock);
    while (nAvailable == nReadPosn)
    {
        ResetEvent(hInputEvent);
        /* Must block until there is input.
           This will only actually happen when called from HandleINT
           since normally we check that input is available first.
           We check for messages while blocking since we may have a
           DDE hidden window around.
        */
        LeaveCriticalSection(&csIOInterlock);
        while (MsgWaitForMultipleObjects(1, &hInputEvent,
                        FALSE, INFINITE, QS_ALLINPUT) == WAIT_OBJECT_0+1)
        {
            MSG Msg;
            while (PeekMessage(&Msg, NULL, 0, 0, PM_REMOVE))
            {
                TranslateMessage(&Msg);
                DispatchMessage(&Msg);
            }
        }
        EnterCriticalSection(&csIOInterlock);
    }
    // Copy the available characters into the buffer.
    while (nReadPosn != nAvailable && nChars-- > 0)
    {
        char ch;
        ch = pchInputBuffer[nReadPosn];
        if (ch == 4 || ch == 26)
        {
            // EOF character.  We have to return this as
            // a separate buffer of size zero so if we've
            // already returned some characters we leave it till
            // next time.
            if (nRes == 0) if (++nReadPosn == nBuffLen) nReadPosn = 0;
            break;
        }
        buff[nRes++] = ch;
        if (++nReadPosn == nBuffLen) nReadPosn = 0;
    }
    if (nAvailable == nReadPosn) ResetEvent(hInputEvent);
    LeaveCriticalSection(&csIOInterlock);
    return nRes;
}


/* All addition is made at the end of the text so this function is
   called to find out if we're there. */
static void MoveToEnd(void)
{
    if (! fAtEnd)
    {
        // Make sure any text we add goes at the end.
        LRESULT dwEnd = SendMessage(hEditWnd, WM_GETTEXTLENGTH, 0, 0);
        SendMessage(hEditWnd, EM_SETSEL, dwEnd, dwEnd);
        fAtEnd = TRUE;
    }
}

// Remove lines at the beginning until we have enough space.
// If nChars is bigger than the limit we'll delete everything and
// return.  Returns the space removed.
static DWORD CheckForScreenSpace(LRESULT nChars)
{
    DWORD dwRemoved = 0;
    // TODO: We could avoid these calls by remembering this information.
    LRESULT limit = SendMessage(hEditWnd, EM_GETLIMITTEXT, 0, 0);
    LRESULT size = SendMessage(hEditWnd, WM_GETTEXTLENGTH, 0, 0);
    while (nChars+size >= limit)
    {
        int i;
        if (size == 0) return dwRemoved;
        for (i = 0; i < size; i++)
        {
            if (SendMessage(hEditWnd, EM_LINEFROMCHAR, i, 0) != 0)
                break;
        }
        SendMessage(hEditWnd, EM_SETSEL, 0, i);
        SendMessage(hEditWnd, WM_CLEAR, 0, 0);
        fAtEnd = FALSE;
        MoveToEnd();
        size -= i;
        dwRemoved += i;
    }
    return dwRemoved;
}

// Expand the buffer if necessary to allow room for
// additional characters.
static void CheckForBufferSpace(int nChars)
{
    BOOL fOverflow;
    if (nNextPosn >= nReadPosn)
        fOverflow = nNextPosn+nChars >= nReadPosn+nBuffLen;
    else fOverflow = nNextPosn+nChars >= nReadPosn;
    if (fOverflow)
    {
        int nOldLen = nBuffLen;
        // Need more space.
        nBuffLen = nBuffLen + nChars + nBuffLen/2;
        pchInputBuffer = (char*)realloc(pchInputBuffer, nBuffLen);
        // Have to copy any data that has wrapped round to the
        // new area.
        if (nNextPosn < nReadPosn)
        {
            int nExtra = nBuffLen-nOldLen;
            if (nExtra >= nNextPosn)
            {
                // All the space before will fit in the new area.
                memcpy(pchInputBuffer+nOldLen, pchInputBuffer, nNextPosn);
            }
            else
            {
                // Some of the space before will fit but not all.
                memcpy(pchInputBuffer+nOldLen, pchInputBuffer, nExtra);
                memmove(pchInputBuffer, pchInputBuffer+nExtra,
                        nNextPosn-nExtra);
            }
            // Adjust these pointers modulo the old and new lengths.
            if (nAvailable < nNextPosn) nAvailable += nOldLen;
            if (nAvailable >= nBuffLen) nAvailable -= nBuffLen;
            nNextPosn += nOldLen;
            if (nNextPosn >= nBuffLen) nNextPosn -= nBuffLen;
        }
    }
    ASSERT(nBuffLen >= 0 && nAvailable >= 0 && nNextPosn >= 0 &&
           nReadPosn >= 0 &&
           nAvailable < nBuffLen && nReadPosn < nBuffLen &&
           nReadPosn < nBuffLen);
    if (nNextPosn > nReadPosn)
        ASSERT(nAvailable >= nReadPosn && nAvailable <= nNextPosn);
    else ASSERT((nNextPosn != nReadPosn &&
                 nAvailable <= nNextPosn) || nAvailable >= nReadPosn);
}

/* DDE requests.  DDE uses an internal window for communication and so all
   DDE operations on a particular instance handle have to be performed by
   the same thread.  That thread also has to check and process the message
   queue.  The previous version did this by having the ML thread make the
   DDE calls and processed the message list in an "interrupt" routine.
   That complicates the Windows interface so now the ML thread sends messages
   to the main window thread to do the work. */
HCONV StartDDEConversation(TCHAR *serviceName, TCHAR *topicName)
{
    return (HCONV)SendMessage(hDDEWindow, WM_DDESTART, (WPARAM)serviceName, (LPARAM)topicName);
}

void CloseDDEConversation(HCONV hConv)
{
    SendMessage(hDDEWindow, WM_DDESTOP, 0, (LPARAM)hConv);
}

LRESULT ExecuteDDE(char *command, HCONV hConv)
{
    return SendMessage(hDDEWindow, WM_DDEEXEC, (WPARAM)hConv, (LPARAM)command);
}

// This is called by the main Poly/ML thread after the arguments have been processed.
void SetupDDEHandler(const TCHAR *lpszServiceName)
{
    SendMessage(hDDEWindow, WM_DDESERVINIT, 0, (LPARAM)lpszServiceName);
}

LRESULT CALLBACK DDEWndProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch (uMsg) 
    {
    case WM_DDESERVINIT:
        return initDDEControl((const TCHAR*)lParam);

    case WM_DDESTART:
        {
            HCONV hcDDEConv;
            HSZ hszServiceName, hszTopicName;
            TCHAR *serviceName = (TCHAR*)wParam;
            TCHAR *topicName = (TCHAR*)lParam;
            hszServiceName =
                DdeCreateStringHandle(dwDDEInstance, serviceName, DDECODEPAGE);
            hszTopicName =
                DdeCreateStringHandle(dwDDEInstance, topicName, DDECODEPAGE);
            hcDDEConv =
                DdeConnect(dwDDEInstance, hszServiceName, hszTopicName, NULL);
            DdeFreeStringHandle(dwDDEInstance, hszServiceName);
            DdeFreeStringHandle(dwDDEInstance, hszTopicName);
            if (hcDDEConv == 0)
            {
                // UINT nErr = DdeGetLastError(dwDDEInstance);
                return 0;
            }
            return (LRESULT)hcDDEConv;
        }

    case WM_DDESTOP:
        DdeDisconnect((HCONV)lParam);
        return 0;

    case WM_DDEEXEC:
        {
            HDDEDATA res;
            LPSTR   command = (LPSTR)lParam;
            res = DdeClientTransaction((LPBYTE)command, (DWORD)(strlen(command)+1),
                    (HCONV)wParam, 0L, 0, XTYP_EXECUTE, TIMEOUT_ASYNC, NULL);
            if (res != 0)
            {
                DdeFreeDataHandle(res);
                // Succeeded - return true;
                return 1;
            }
            else if (DdeGetLastError(dwDDEInstance) == DMLERR_BUSY)
                // If it's busy return false.
                return 0;
            else return -1; // An error
        }

    default:
        return DefWindowProc(hwnd, uMsg, wParam, lParam);
    }
}

/* In order to be able to handle all the keys we need to
   sub-class the edit control.  */ 
static LRESULT APIENTRY EditSubclassProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) 
{
    switch (uMsg)
    {
    case WM_GETDLGCODE:
        return DLGC_WANTALLKEYS | DLGC_WANTCHARS;

    case WM_KEYDOWN:
        switch(wParam)
        {
        case VK_DELETE: // Ignore the delete key.  Beep perhaps?
            return 0;
        case VK_LEFT: // If we move the cursor we are probably not
        case VK_RIGHT: // at the end.
        case VK_UP:
        case VK_DOWN:
            fAtEnd = FALSE;
        default:
            return CallWindowProc(wpOrigEditProc, hwnd, uMsg,  wParam, lParam);
        }

    case WM_CHAR:
        {
            LPARAM nRpt = lParam & 0xffff;
            EnterCriticalSection(&csIOInterlock);
            if (wParam == '\b')
            {
                // Delete the previous character(s).
                if (nNextPosn != nAvailable)
                {
                    int nCanRemove = 0;
                    while (nRpt-- > 0 && nNextPosn != nAvailable)
                    {
                        nCanRemove++;
                        if (nNextPosn == 0) nNextPosn = nBuffLen;
                        nNextPosn--;
                    }
                    lParam = (lParam & 0xffff0000) | nCanRemove;
                    LeaveCriticalSection(&csIOInterlock);
                    return CallWindowProc(wpOrigEditProc, hwnd, uMsg,  wParam, lParam); 
                }
            }
            else if (wParam == 22) // Control-V
            {
                // Generate a Paste command.
                SendMessage(hMainWindow, WM_COMMAND, ID_EDIT_PASTE, 0);
            }
            else if (wParam == 3) // Control-C
            {
                // In Windows this has the effect of Copy but we also
                // want it to generate an interrupt.  I've chosen to
                // make it copy if there is any selection, otherwise to
                // generate an interrupt.  We'll have to see how this works.
                DWORD dwStart, dwEnd;
                SendMessage(hwnd, EM_GETSEL, (WPARAM)&dwStart, (LPARAM)&dwEnd);
                if (dwStart != dwEnd)
                {
                    SendMessage(hwnd, WM_COPY, 0, 0); 
                }
                else {
                    // Discard any type-ahead.
                    nNextPosn = nAvailable = nReadPosn = 0;
                    RequestConsoleInterrupt();
                }
            }
            else if (wParam >= ' ' || wParam == '\r' || wParam == '\t' ||
                     wParam == 4 /* ctrl-D */ || wParam == 26 /* ctrl-Z */)
            {
                CheckForBufferSpace((int)nRpt);
                CheckForScreenSpace(nRpt); // Make sure we have space on the screen.
                // Add the character(s) to the buffer.
                while (nRpt-- > 0)
                {
                    if (wParam == '\r')
                    {
                        pchInputBuffer[nNextPosn++] = '\n';
                        nAvailable = nNextPosn;
                        SetEvent(hInputEvent);
                    }
                    else if (wParam == 4 || wParam == 26)
                    {
                        // Treat either of these as EOF chars.
                        pchInputBuffer[nNextPosn++] = (CHAR)wParam;
                        nAvailable = nNextPosn;
                        SetEvent(hInputEvent);
                        wParam = 4;
                    }
                    else pchInputBuffer[nNextPosn++] = (CHAR)wParam;
                    if (nNextPosn == nBuffLen) nNextPosn = 0;
                    if (nAvailable == nBuffLen) nAvailable = 0;
                }
                MoveToEnd();
                LeaveCriticalSection(&csIOInterlock);
                // Add this to the window except if it's ctrl-Z or ctrl-D.
                if (wParam == 4 || wParam == 26) return 0;
                return CallWindowProc(wpOrigEditProc, hwnd, uMsg,  wParam, lParam); 
            }
            LeaveCriticalSection(&csIOInterlock);
            return 0;
        }

    case WM_DESTROY:
        {
            HFONT hFount;
            // Switch back to the old window proc just in case.
#ifdef _M_AMD64
            SetWindowLongPtr(hwnd, GWLP_WNDPROC, (INT_PTR)wpOrigEditProc);
            SetWindowLongPtr(hwnd, GWLP_USERDATA, 0);
#else
            SetWindowLong(hwnd, GWL_WNDPROC, (LONG)wpOrigEditProc);
            SetWindowLong(hwnd, GWL_USERDATA, 0);
#endif
            // Get the fount and delete it if it's not the default.
            hFount = (HFONT)SendMessage(hwnd, WM_GETFONT, 0, 0);
            if (hFount != NULL)
            {
                SendMessage(hwnd, WM_SETFONT, (WPARAM)NULL, FALSE);
                DeleteObject(hFount);
            }
            // Call the original to finish off.
            return CallWindowProc(wpOrigEditProc, hwnd, uMsg,  wParam, lParam); 
        }

    case WM_LBUTTONDOWN:
    case WM_RBUTTONDOWN:
    case WM_LBUTTONUP:
    case WM_RBUTTONUP:
    case EM_SETSEL:
        // Need to record that we may no longer be at the end of the text.
        fAtEnd = FALSE;
        // Drop through to default.

    default:
        return CallWindowProc(wpOrigEditProc, hwnd, uMsg,  wParam, lParam); 
    }
} 

/* This function is only used when the "About Poly/ML" dialogue box is
   being displayed. */
static BOOL CALLBACK AboutProc(HWND hwndDlg, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch (uMsg)
    {
    case WM_INITDIALOG: return 1;
    case WM_COMMAND:
        if (wParam == IDOK)
        {
            EndDialog(hwndDlg, IDOK);
            return 1;
        }
    case WM_CLOSE:
        EndDialog(hwndDlg, IDOK);
        return 1;
    default: return 0;
    }
}

#ifdef UNICODE
#define CF_TEXTFORMAT   CF_UNICODETEXT
#else
#define CF_TEXTFORMAT   CF_TEXT
#endif

/* This is the main window procedure. */
LRESULT CALLBACK WndProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch (uMsg) 
    { 
        case WM_CREATE:
            {
                hEditWnd = CreateWindow(_T("EDIT"), NULL,
                    WS_CHILD | WS_VISIBLE | WS_VSCROLL | WS_HSCROLL |
                    ES_LEFT | ES_MULTILINE | ES_AUTOVSCROLL | ES_AUTOHSCROLL, 
                    0, 0, 0, 0,
                    hwnd, 0, hApplicationInstance, NULL);
                if (hEditWnd == NULL) return -1; /* Failed */

                // Sub-class this so that we get the keys that are pressed.
                // Save the old window proc.
#ifdef _M_AMD64
                wpOrigEditProc =
                    (WNDPROC)GetWindowLongPtr(hEditWnd, GWLP_WNDPROC);
               // Set our new window proc.
                SetWindowLongPtr(hEditWnd, GWLP_WNDPROC, (INT_PTR)EditSubclassProc);
#else
                wpOrigEditProc =
                    (WNDPROC)GetWindowLong(hEditWnd, GWL_WNDPROC);
               // Set our new window proc.
                SetWindowLong(hEditWnd, GWL_WNDPROC, (LONG)EditSubclassProc);
#endif
                fAtEnd = TRUE;

                // Get a 10 point Courier fount.
                HDC hDC = GetDC(hEditWnd);
                int nHeight = -MulDiv(10, GetDeviceCaps(hDC, LOGPIXELSY), 72);
                ReleaseDC(hEditWnd, hDC);
                HFONT hFont = CreateFont(nHeight, 0, 0, 0, FW_DONTCARE,
                                    FALSE, FALSE, FALSE, ANSI_CHARSET,
                                    OUT_DEFAULT_PRECIS, CLIP_DEFAULT_PRECIS,
                                    DEFAULT_QUALITY, FIXED_PITCH | FF_MODERN,
                                    _T("Courier"));
                if (hFont) SendMessage(hEditWnd, WM_SETFONT, (WPARAM)hFont, 0);
 
                SetWindowText(hEditWnd, _T(""));
                return 0; /* Succeeded */
            }
 
        case WM_SETFOCUS:
            /* When the focus arrives at the parent set the focus on
               the edit window. */
            SetFocus(hEditWnd); 
            return 0; 

        case WM_SIZE:
            {
                LONG offset = 0;
                // Make the edit control the size of the window's client area.
                MoveWindow(hEditWnd, 0, offset, LOWORD(lParam), HIWORD(lParam)-offset, TRUE);
            }
            return 0;

        case WM_DESTROY:
            PostQuitMessage(0);
            return 0;

        case WM_COMMAND:
            switch(wParam)
            {
            case ID_EDIT_COPY:
                SendMessage(hEditWnd, WM_COPY, 0, 0); 
                return 0; 

            case ID_EDIT_PASTE:
                if (IsClipboardFormatAvailable(CF_TEXTFORMAT))
                {
                    // We need to check that we have enough space
                    // BEFORE we try pasting.
                    HANDLE hClip;
                    LPCTSTR lpszText;
                    OpenClipboard(hEditWnd);
                    hClip = GetClipboardData(CF_TEXTFORMAT);
                    lpszText = (LPCTSTR)GlobalLock(hClip);
                    CheckForScreenSpace(lstrlen(lpszText));
                    MoveToEnd();
                    // Add it to the screen.
                    SendMessage(hEditWnd, EM_REPLACESEL, FALSE, (LPARAM)lpszText);
                    // Add to the type-ahead.
                    EnterCriticalSection(&csIOInterlock);
                    // Check there's enough space.  This may be an
                    // over-estimate since we replace CRNL by NL.
                    CheckForBufferSpace(lstrlen(lpszText));
                    while (*lpszText)
                    {
                        // The data we're pasting contains CRNL as
                        // line separators.
                        if (lpszText[0] == '\r' && lpszText[1] == '\n')
                        {
                            pchInputBuffer[nNextPosn++] = '\n';
                            if (nNextPosn == nBuffLen) nNextPosn = 0;
                            nAvailable = nNextPosn;
                            lpszText += 2;
                        }
                        else {
                            pchInputBuffer[nNextPosn++] = (char)*lpszText++;
                            if (nNextPosn == nBuffLen) nNextPosn = 0;
                            if (lpszText[0] == 4 || lpszText[0] == 26)
                                nAvailable = nNextPosn; // EOF characters.
                        }
                    }
                    if (nAvailable != nReadPosn) SetEvent(hInputEvent);
                    LeaveCriticalSection(&csIOInterlock);
                    GlobalUnlock(hClip);
                    CloseClipboard();
                }
                return 0; 

            case ID_HELP_ABOUT: 
                DialogBox(hApplicationInstance, MAKEINTRESOURCE(IDD_ABOUT_POLYML),
                    hwnd, (DLGPROC)AboutProc); 
                return 0;

            case ID_FILE_QUIT:
                if (MessageBox(hwnd, _T("Are you sure you want to quit?"),
                                     _T("Confirm Quit"), MB_OKCANCEL) == IDOK)
                    processes->Exit(0);
                return 0;

            case ID_RUN_INTERRUPT:
                // Discard any type-ahead.
                nNextPosn = nAvailable = nReadPosn = 0;
                RequestConsoleInterrupt();
                return 0;

            default: return DefWindowProc(hwnd, uMsg, wParam, lParam);
            }

        case WM_CLOSE:
            if (MessageBox(hwnd, _T("Are you sure you want to quit?"),
                                 _T("Confirm Quit"), MB_OKCANCEL) == IDOK)
                processes->Exit(0);
            return 0;

        case WM_ADDTEXT:
            // Request from the input thread to add some text.
            {
                // Remember the old selection and the original length.
                LRESULT lrStart, lrEnd;
                SendMessage(hEditWnd, EM_GETSEL,
                            (WPARAM)&lrStart, (LPARAM)&lrEnd);
                LRESULT lrLength = SendMessage(hEditWnd, WM_GETTEXTLENGTH, 0, 0);
                LRESULT lrRemoved = CheckForScreenSpace(lrLength);
                MoveToEnd();
                SendMessage(hEditWnd, EM_REPLACESEL, 0, lParam);
                // If the old selection was at the end (i.e. the pointer
                // was at the end) we don't reinstate the old selection.
                if (lrStart != lrLength && lrEnd > lrRemoved)
                {
                    if (lrStart > lrRemoved) lrStart -= lrRemoved; else lrStart = 0;
                    fAtEnd = FALSE;
                    SendMessage(hEditWnd, EM_SETSEL, lrStart, lrEnd-lrRemoved);
                }
                return 0;
            }


        default:
            return DefWindowProc(hwnd, uMsg, wParam, lParam);
    } 
} 
 
static DWORD WINAPI InThrdProc(LPVOID lpParameter)
// This thread deals with input from the ML process.
{
    while (1)
    {
        CHAR buff[4096];
        DWORD dwRead;
        if (! ReadFile(hReadFromML, buff, sizeof(buff)-1, &dwRead, NULL))
            return 0;
        buff[dwRead] = 0;
        if (! isActive) { ShowWindow(hMainWindow, nInitialShow); isActive = true; }
#ifdef UNICODE
        // We need to write Unicode here.  Convert it using the current code-page.
        int wlen = MultiByteToWideChar(codePage, 0, buff, -1, NULL, 0);
        if (wlen == 0) continue;
        WCHAR *wBuff = new WCHAR[wlen];
        wlen = MultiByteToWideChar(codePage, 0, buff, -1, wBuff, wlen);
        SendMessage(hMainWindow, WM_ADDTEXT, 0, (LPARAM)wBuff);
        delete[] wBuff;
#else
        SendMessage(hMainWindow, WM_ADDTEXT, 0, (LPARAM)buff);
#endif
    }
}

static DWORD WINAPI MainThrdProc(LPVOID lpParameter)
// This thread simply continues with the rest of the ML
// initialistion.
{
    exportDescription *exports = (exportDescription *)lpParameter;
    return polymain(nArgs, lpArgs, exports);
}

// Called with various control events if the input stream is a console.
static BOOL WINAPI CtrlHandler(DWORD dwCtrlType)
{
    if (dwCtrlType == CTRL_C_EVENT)
    {
        RequestConsoleInterrupt();
        return TRUE;
    }
    return FALSE;
}

// Main entry point.  Called from WinMain with a pointer to the ML code.
int PolyWinMain(
  HINSTANCE hInstance,
  HINSTANCE hPrevInstance,
  LPSTR lpCmdLineUnused,
  int nCmdShow,
  exportDescription *exports
)
{
    HANDLE hWriteToScreen = INVALID_HANDLE_VALUE;
    DWORD dwInId, dwRes;

    SetErrorMode(0); // Force a proper error report

    InitializeCriticalSection(&csIOInterlock);
    hInputEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
    hApplicationInstance = hInstance;

    // If we already have standard input and standard output we
    // don't replace them, otherwise we create a window and pipes
    // to connect it.  We use _get_osfhandle here because that
    // checks for handles passed in in the STARTUPINFO as well as
    // those inherited as standard handles.
    HANDLE hStdInHandle = (HANDLE)_get_osfhandle(fileno(stdin));
    HANDLE hStdOutHandle = (HANDLE)_get_osfhandle(fileno(stdout));
    HANDLE hStdErrHandle = (HANDLE)_get_osfhandle(fileno(stderr));

    // Do we have stdin?  If we do we need to create a pipe to buffer
    // the input.
    if (hStdInHandle != INVALID_HANDLE_VALUE)
    {
        // We're using the stdin passed in by the caller.  This may well
        // be a pipe and in order to get reasonable performance we need
        // to interpose a thread.  This is the only way to be able to have
        // something we can pass to MsgWaitForMultipleObjects, in this case
        // hInputEvent, which will indicate the input is available.
        // Duplicate the handle because we're going to close this.
        if (! DuplicateHandle(GetCurrentProcess(), hStdInHandle,
                              GetCurrentProcess(), &hOldStdin, 0, TRUE, // inheritable
                              DUPLICATE_SAME_ACCESS ))
            return 1;

        HANDLE hNewStdin = CreateCopyPipe(hOldStdin, hInputEvent);
        if (hNewStdin == NULL) return 1;

        SetConsoleCtrlHandler(CtrlHandler, TRUE); // May fail if there's no console.

        // Replace the current stdin with the output from the pipe.
        fclose(stdin);
        int newstdin = _open_osfhandle ((INT_PTR)hNewStdin, _O_RDONLY | _O_TEXT);
        if (newstdin != 0) _dup2(newstdin, 0);
        fdopen(0, "rt");
    }
    else
    {
        // No stdin.  Open it on NUL.  If we actually create our own console
        // we won't actually use this and instead we'll read from the console.
        // In that case we won't use stdin but something else might.
        fclose(stdin);
        int newstdin = open("NUL", _O_RDONLY);
        _dup2(newstdin, 0);
        // Open it for stdio as well.  Because the entries in the FILE table
        // are opened in order we need to do this to ensure that stdout and
        // stderr point to the correct entries.
        _fdopen(0, "rt");
        hStdInHandle =  (HANDLE)_get_osfhandle(newstdin);
        SetStdHandle(STD_INPUT_HANDLE, hStdInHandle);

        // If we're not going to create a console because we have a stdout
        // we need to set this as the original stdin.
        if (hStdOutHandle != INVALID_HANDLE_VALUE)
            hOldStdin = hStdInHandle;
    }

    // If we don't have a standard output we use our own console.
    if (hStdOutHandle == INVALID_HANDLE_VALUE)
    {
        WNDCLASSEX wndClass;
        ATOM atClass;
        // Allocate initial buffer space to maintain the invariants.
        nBuffLen = 80;
        pchInputBuffer = (char*)malloc(nBuffLen);

        if (!CreatePipe(&hReadFromML, &hWriteToScreen, NULL, 0)) {
            return 1;
        }
        HANDLE hTemp;
        // The pipe handles we have are not inheritable.  We have to
        // make hWriteToScreen an inheritable handle so that
        // processes we fork using "system" can write to the screen.
        if (! DuplicateHandle(GetCurrentProcess(), hWriteToScreen,
                             GetCurrentProcess(), &hTemp, 0, TRUE, // inheritable
                             DUPLICATE_SAME_ACCESS )) {
            return 1;
        }
        CloseHandle(hWriteToScreen);
        hWriteToScreen = hTemp;

        // Replace the standard Windows handles.
        SetStdHandle(STD_OUTPUT_HANDLE, hWriteToScreen);
        // Close the stdio streams.  They may have been opened
        // on dummy handles.
        fclose(stdout);
        // Set up the new handles.
        int newstdout = _open_osfhandle ((INT_PTR)hWriteToScreen, _O_TEXT);
        // We need this to be stream 1.  basicio.cpp uses this for TextIO.stdOut
        if (newstdout != 1) _dup2(newstdout, 1);
        // A few RTS modules use stdio for output, primarily objsize and diagnostics.
        // Previously this next line was sufficient to reopen stdout but that no longer
        // works in VS 2015.  We have to use polyStdout now.
        extern FILE *polyStdout;
        polyStdout = _fdopen(1, "wt"); // == stdout

        if (hStdErrHandle == INVALID_HANDLE_VALUE)
        {
            // If we didn't have stderr write any stderr output to our console.
            SetStdHandle(STD_ERROR_HANDLE, hWriteToScreen);
            fclose(stderr);
            _dup2(newstdout, 2); // Stderr
            extern FILE *polyStderr;
            polyStderr = _fdopen(2, "wt"); // == stderr
            // Set stderr to unbuffered so that messages get written correctly.
            // (stdout is explicitly flushed).
            setvbuf(stderr, NULL, _IONBF, 0);
        }

        // Create a thread to manage the output from ML.
        HANDLE hInThread = CreateThread(NULL, 0, InThrdProc, 0, 0, &dwInId);
        if (hInThread == NULL) return 1;
        CloseHandle(hInThread);
        wndClass.cbSize = sizeof(wndClass);
        wndClass.style = 0;
        wndClass.lpfnWndProc = WndProc; 
        wndClass.cbClsExtra = 0;
        wndClass.cbWndExtra = 0; 
        wndClass.hInstance = hInstance; 
        wndClass.hIcon = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_ICON));
        wndClass.hCursor = NULL; // For the moment 
        wndClass.hbrBackground = NULL; // For the moment
        wndClass.lpszClassName = _T("PolyMLWindowClass");
        wndClass.lpszMenuName = MAKEINTRESOURCE(IDR_MENU); 
        wndClass.hIconSm = NULL; // For the moment
        DWORD dwStyle = WS_OVERLAPPEDWINDOW;

        if ((atClass = RegisterClassEx(&wndClass)) == 0)
        {
            return 1;
        }

        // Initially created invisible.
        hMainWindow = CreateWindow(
            (LPTSTR)(intptr_t)atClass,
            _T("Poly/ML"),
            dwStyle,
            CW_USEDEFAULT,
            CW_USEDEFAULT,
            CW_USEDEFAULT,
            CW_USEDEFAULT,
            NULL,
            NULL,   // handle to menu or child-window identifier
            hInstance,
            NULL     // pointer to window-creation data
            );

        if (hMainWindow == NULL)
        {
            return 1;
        }

        // Save this setting and only apply it when we actually
        // read from or write to the main window.  That way if we are
        // actually using another window this will never get displayed.
        nInitialShow = nCmdShow;
    }
    // We had a stdout but maybe not stderr.  We could choose to direct stderr output
    // to the provided stdout but maybe that's not what the user wants.  Instead
    // we open one on NUL.
    else if (hStdErrHandle == INVALID_HANDLE_VALUE)
    {
        fclose(stderr);
        int newstderr = open("NUL", _O_WRONLY);
        _dup2(newstderr, 2); // Stderr
        _fdopen(2, "wt"); // == stderr
        SetStdHandle(STD_ERROR_HANDLE, (HANDLE)_get_osfhandle(newstderr));
        // Set stderr to unbuffered so that messages get written correctly.
        // (stdout is explicitly flushed).
        setvbuf(stderr, NULL, _IONBF, 0);
    }

    // Set nArgs and lpArgs to the command line arguments.
    // Convert the command line into Unix-style arguments.  There isn't a
    // CommandLineToArgvA function so we have to use the Unicode version and
    // convert the results.
    {
        // Get the unicode args
        LPWSTR *uniArgs = CommandLineToArgvW(GetCommandLineW(), &nArgs);
#ifdef UNICODE
        lpArgs = uniArgs;
#else
        if (uniArgs != NULL)
        {
            lpArgs = (LPSTR*)calloc(nArgs, sizeof(LPSTR));
            if (lpArgs != 0)
            {
                for (int i = 0; i < nArgs; i++)
                {
                    // See how much space will be needed
                    int space =
                        WideCharToMultiByte(CP_ACP, 0, uniArgs[i], -1, NULL, 0, NULL, NULL);
                    if (space == 0) break; // Failed for some reason
                    // Allocate the space then do the conversion
                    LPSTR buff = (LPSTR)malloc(space);
                    if (buff == 0) break;
                    int result =
                        WideCharToMultiByte(CP_ACP, 0, uniArgs[i], -1, buff, space, NULL, NULL);
                    if (result == 0) { free(buff); break; }
                    lpArgs[i] = buff;
                }
            }
            LocalFree(uniArgs);
        }
#endif
    }

    // Create an internal hidden window to handle DDE requests from the ML thread.
    {
        WNDCLASSEX wndClass;
        ATOM atClass;
        memset(&wndClass, 0, sizeof(wndClass));
        wndClass.cbSize = sizeof(wndClass);
        wndClass.lpfnWndProc = DDEWndProc; 
        wndClass.hInstance = hInstance; 
        wndClass.lpszClassName = _T("PolyMLDDEWindowClass");

        if ((atClass = RegisterClassEx(&wndClass)) == 0) return 1;

        hDDEWindow = CreateWindow(
            (LPTSTR)(intptr_t)atClass,
            _T("Poly/ML-DDE"),
            WS_OVERLAPPEDWINDOW,
            CW_USEDEFAULT,
            CW_USEDEFAULT,
            CW_USEDEFAULT,
            CW_USEDEFAULT,
            NULL,
            NULL,   // handle to menu or child-window identifier
            hInstance,
            NULL     // pointer to window-creation data
            );
    }

    // Call the main program to do the rest of the initialisation.
    HANDLE hMainThread = CreateThread(NULL, 0, MainThrdProc, exports, 0, &dwInId);

    // Enter the main message loop.
    while (MsgWaitForMultipleObjects(1, &hMainThread,
                    FALSE, INFINITE, QS_ALLINPUT) == WAIT_OBJECT_0+1)
    {
        MSG Msg;
        while (PeekMessage(&Msg, NULL, 0, 0, PM_REMOVE))
        {
            TranslateMessage(&Msg);
            DispatchMessage(&Msg);
        }
    }

    // Closing this end of the pipe will cause the thread to go away.
    if (hWriteToScreen != INVALID_HANDLE_VALUE) CloseHandle(hWriteToScreen);

    if (! GetExitCodeThread(hMainThread, &dwRes)) dwRes = 0;

    uninitDDEControl();
    DestroyWindow(hDDEWindow);
    DeleteCriticalSection(&csIOInterlock);
    if (hInputEvent) CloseHandle(hInputEvent);
    return dwRes;
}

HDDEDATA CALLBACK DdeCallback(UINT uType, UINT uFmt, HCONV hconv,
                              HSZ hsz1, HSZ hsz2, HDDEDATA hdata,
                              ULONG_PTR dwData1, ULONG_PTR dwData2) 
{ 
    switch (uType) 
    { 
        case XTYP_CONNECT:
            // Client connecting.  For the moment we ignore
            // the topic.
            return (HDDEDATA) TRUE;

        case XTYP_EXECUTE:
            {
                // See what the message is.  The only ones we
                // handle are interrupt and terminate.
                TCHAR buff[256];
                buff[0] = 0;
                DdeGetData(hdata, (LPBYTE)buff, sizeof(buff), 0);
                if (lstrcmpi(buff, _T(POLYINTERRUPT)) == 0)
                {
                    RequestConsoleInterrupt();
                    return (HDDEDATA) DDE_FACK;
                }
                if (lstrcmpi(buff, _T(POLYTERMINATE)) == 0)
                {
                    processes->Exit(0);
                    return (HDDEDATA) DDE_FACK;
                }
                return (HDDEDATA) DDE_FNOTPROCESSED;
            }

        default: 
            return (HDDEDATA) NULL; 
    } 
} 

static int initDDEControl(const TCHAR *lpszName)
{
    // Start the DDE service.  This receives remote requests.
    if (DdeInitialize(&dwDDEInstance, DdeCallback,
        APPCLASS_STANDARD | CBF_FAIL_ADVISES | CBF_FAIL_POKES |
        CBF_FAIL_REQUESTS | CBF_SKIP_ALLNOTIFICATIONS, 0)
        != DMLERR_NO_ERROR)
    return 0;

    // If we were given a service name we register that,
    // otherwise we use the default name.
    if (lpszName == 0) lpszName = POLYMLSERVICE;
    HSZ hszServiceName = DdeCreateStringHandle(dwDDEInstance, lpszName, DDECODEPAGE);
    if (hszServiceName == 0) return 0;

    DdeNameService(dwDDEInstance, hszServiceName, 0L, DNS_REGISTER);

    DdeFreeStringHandle(dwDDEInstance, hszServiceName);
    return 1;
}

static void uninitDDEControl(void)
{
    // Unregister our name(s).
    DdeNameService(dwDDEInstance, 0L, 0L, DNS_UNREGISTER);
//  DdeAbandonTransaction(dwDDEInstance, 0L, 0L);
    // Unitialise DDE.
    DdeUninitialize(dwDDEInstance);
}

// We want copyThread to be static but also a friend of CopyPipe
// GCC requires it to be declared static first otherwise it creates it
// extern when it sees it as a friend then complains when it's static.
static DWORD WINAPI copyThread(LPVOID lpParameter);

class CopyPipe {
public:
    CopyPipe():
      hOriginal(NULL), hOutput(NULL), hEvent(NULL) {}

    HANDLE RunPipe(HANDLE hIn, HANDLE hEv);
private:
    ~CopyPipe();

    void threadFunction(void);

    HANDLE hOriginal;
    HANDLE hOutput;
    HANDLE hEvent;

    friend DWORD WINAPI copyThread(LPVOID lpParameter);
};

CopyPipe::~CopyPipe()
{
    if (hOutput) CloseHandle(hOutput);
    if (hOriginal) CloseHandle(hOriginal);
    if (hEvent) CloseHandle(hEvent);
}

static DWORD WINAPI copyThread(LPVOID lpParameter)
{
    CopyPipe *cp = (CopyPipe *)lpParameter;
    cp->threadFunction();
    delete cp;
    return 0;
}

// This thread is used when the caller has provided a standard input
// stream and we're using that and not our console.  It copies the
// standard input to a pipe and the ML code uses that as its input.
// This way we can set hInputEvent whenever input is available.
void CopyPipe::threadFunction()
{
    // Duplicate the event handle so that we can close it when we've finished
    char buffer[4096];

    while (true) {
        DWORD dwRead;
        if (! ReadFile(hOriginal, buffer, sizeof(buffer), &dwRead, NULL))
        {
            SetEvent(hEvent);
            return;
        }

        if (dwRead == 0) // End-of-stream
        {
            // If we are reading from the (Windows) console and the user presses ctrl-C we
            // may get a ERROR_OPERATION_ABORTED error.
            if (GetLastError() == ERROR_OPERATION_ABORTED)
            {
                SetLastError(0); // Reset this.  We may have a normal EOF next.
                continue;
            }
            // Normal exit.  Indicate EOF
            SetEvent(hEvent);
            return;
        }

        SetEvent(hEvent); // Signal input has arrived
        char *b = buffer;
        do {
            DWORD dwWritten;
            if (! WriteFile(hOutput, b, dwRead, &dwWritten, NULL))
            {
                SetEvent(hEvent);
                return;
            }
            b += dwWritten;
            dwRead -= dwWritten;
        } while (dwRead != 0);
    }
}

HANDLE CopyPipe::RunPipe(HANDLE hIn, HANDLE hEv)
{
    HANDLE hNewInput = NULL;
    hOriginal = hIn;

    if (!CreatePipe(&hNewInput, &hOutput, NULL, 0)) return NULL;

    if (! DuplicateHandle(GetCurrentProcess(), hEv, GetCurrentProcess(),
                    &hEvent, 0, FALSE, DUPLICATE_SAME_ACCESS))
        return NULL;

    DWORD dwInId;
    HANDLE hInThread = CreateThread(NULL, 0, copyThread, this, 0, &dwInId);
    if (hInThread == NULL) return NULL;
    CloseHandle(hInThread);

    return hNewInput;
}

// Create a pipe and a thread to read the input thread and signal the
// event when input is available.  Returns a handle to a pipe that
// supplies a copy of the original input.
HANDLE CreateCopyPipe(HANDLE hInput, HANDLE hEvent)
{
    CopyPipe *cp = new CopyPipe();
    return cp->RunPipe(hInput, hEvent);
}

