/* Readline interface for the tokenizer and [raw_]input() in bltinmodule.c.

   By default, or when stdin is not a tty device, we have a super

   simple my_readline function using fgets.

   Optionally, we can use the GNU readline library.

   my_readline() has a different return value from GNU readline():

   - NULL if an interrupt occurred or if an error occurred

   - a malloc'ed empty string if EOF was read

   - a malloc'ed string ending in \n normally

*/

#include "Python.h"

#include "pycore_fileutils.h"     // _Py_BEGIN_SUPPRESS_IPH

#include "pycore_interp.h"        // _PyInterpreterState_GetConfig()

#include "pycore_pystate.h"       // _PyThreadState_GET()

#include "pycore_signal.h"        // _PyOS_SigintEvent()

#ifdef MS_WINDOWS

#  ifndef WIN32_LEAN_AND_MEAN

#    define WIN32_LEAN_AND_MEAN

#  endif

#  include "windows.h"

#endif /* MS_WINDOWS */

#ifdef HAVE_UNISTD_H

#  include <unistd.h>             // isatty()

#endif

// Export the symbol since it's used by the readline shared extension

PyAPI_DATA(PyThreadState*) _PyOS_ReadlineTState;

PyThreadState *_PyOS_ReadlineTState = NULL;

static PyMutex _PyOS_ReadlineLock;

int (*PyOS_InputHook)(void) = NULL;

/* This function restarts a fgets() after an EINTR error occurred

   except if _PyOS_InterruptOccurred() returns true. */

static int

my_fgets(PyThreadState* tstate, char *buf, int len, FILE *fp)

{

#ifdef MS_WINDOWS

    HANDLE handle;

    _Py_BEGIN_SUPPRESS_IPH

    handle = (HANDLE)_get_osfhandle(fileno(fp));

    _Py_END_SUPPRESS_IPH

    /* bpo-40826: fgets(fp) does crash if fileno(fp) is closed */

    if (handle == INVALID_HANDLE_VALUE) {

        return -1; /* EOF */

    }

#endif

    while (1) {

        if (PyOS_InputHook != NULL &&

            // GH-104668: See PyOS_ReadlineFunctionPointer's comment below...

            _Py_IsMainInterpreter(tstate->interp))

        {

            (void)(PyOS_InputHook)();

        }

        errno = 0;

        clearerr(fp);

        char *p = fgets(buf, len, fp);

        if (p != NULL) {

            return 0; /* No error */

        }

        int err = errno;

#ifdef MS_WINDOWS

        /* Ctrl-C anywhere on the line or Ctrl-Z if the only character

           on a line will set ERROR_OPERATION_ABORTED. Under normal

           circumstances Ctrl-C will also have caused the SIGINT handler

           to fire which will have set the event object returned by

           _PyOS_SigintEvent. This signal fires in another thread and

           is not guaranteed to have occurred before this point in the

           code.

           Therefore: check whether the event is set with a small timeout.

           If it is, assume this is a Ctrl-C and reset the event. If it

           isn't set assume that this is a Ctrl-Z on its own and drop

           through to check for EOF.

        */

        if (GetLastError()==ERROR_OPERATION_ABORTED) {

            HANDLE hInterruptEvent = _PyOS_SigintEvent();

            switch (WaitForSingleObjectEx(hInterruptEvent, 10, FALSE)) {

            case WAIT_OBJECT_0:

                ResetEvent(hInterruptEvent);

                return 1; /* Interrupt */

            case WAIT_FAILED:

                return -2; /* Error */

            }

        }

#endif /* MS_WINDOWS */

        if (feof(fp)) {

            clearerr(fp);

            return -1; /* EOF */

        }

#ifdef EINTR

        if (err == EINTR) {

            PyEval_RestoreThread(tstate);

            int s = PyErr_CheckSignals();

            PyEval_SaveThread();

            if (s < 0) {

                return 1;

            }

            /* try again */

            continue;

        }

#endif

        if (_PyOS_InterruptOccurred(tstate)) {

            return 1; /* Interrupt */

        }

        return -2; /* Error */

    }

    /* NOTREACHED */

}

#ifdef HAVE_WINDOWS_CONSOLE_IO

/* Readline implementation using ReadConsoleW */

extern char _get_console_type(HANDLE handle);

char *

_PyOS_WindowsConsoleReadline(PyThreadState *tstate, HANDLE hStdIn)

{

    static wchar_t wbuf_local[1024 * 16];

    const DWORD chunk_size = 1024;

    DWORD n_read, total_read, wbuflen, u8len;

    wchar_t *wbuf;

    char *buf = NULL;

    int err = 0;

    n_read = (DWORD)-1;

    total_read = 0;

    wbuf = wbuf_local;

    wbuflen = sizeof(wbuf_local) / sizeof(wbuf_local[0]) - 1;

    while (1) {

        if (PyOS_InputHook != NULL &&

            // GH-104668: See PyOS_ReadlineFunctionPointer's comment below...

            _Py_IsMainInterpreter(tstate->interp))

        {

            (void)(PyOS_InputHook)();

        }

        if (!ReadConsoleW(hStdIn, &wbuf[total_read], wbuflen - total_read, &n_read, NULL)) {

            err = GetLastError();

            goto exit;

        }

        if (n_read == (DWORD)-1 && (err = GetLastError()) == ERROR_OPERATION_ABORTED) {

            break;

        }

        if (n_read == 0) {

            int s;

            err = GetLastError();

            if (err != ERROR_OPERATION_ABORTED)

                goto exit;

            err = 0;

            HANDLE hInterruptEvent = _PyOS_SigintEvent();

            if (WaitForSingleObjectEx(hInterruptEvent, 100, FALSE)

                    == WAIT_OBJECT_0) {

                ResetEvent(hInterruptEvent);

                PyEval_RestoreThread(tstate);

                s = PyErr_CheckSignals();

                PyEval_SaveThread();

                if (s < 0) {

                    goto exit;

                }

            }

            break;

        }

        total_read += n_read;

        if (total_read == 0 || wbuf[total_read - 1] == L'\n') {

            break;

        }

        wbuflen += chunk_size;

        if (wbuf == wbuf_local) {

            wbuf[total_read] = '\0';

            wbuf = (wchar_t*)PyMem_RawMalloc(wbuflen * sizeof(wchar_t));

            if (wbuf) {

                wcscpy_s(wbuf, wbuflen, wbuf_local);

            }

            else {

                PyEval_RestoreThread(tstate);

                PyErr_NoMemory();

                PyEval_SaveThread();

                goto exit;

            }

        }

        else {

            wchar_t *tmp = PyMem_RawRealloc(wbuf, wbuflen * sizeof(wchar_t));

            if (tmp == NULL) {

                PyEval_RestoreThread(tstate);

                PyErr_NoMemory();

                PyEval_SaveThread();

                goto exit;

            }

            wbuf = tmp;

        }

    }

    if (wbuf[0] == '\x1a') {

        buf = PyMem_RawMalloc(1);

        if (buf) {

            buf[0] = '\0';

        }

        else {

            PyEval_RestoreThread(tstate);

            PyErr_NoMemory();

            PyEval_SaveThread();

        }

        goto exit;

    }

    u8len = WideCharToMultiByte(CP_UTF8, 0,

                                wbuf, total_read,

                                NULL, 0,

                                NULL, NULL);

    buf = PyMem_RawMalloc(u8len + 1);

    if (buf == NULL) {

        PyEval_RestoreThread(tstate);

        PyErr_NoMemory();

        PyEval_SaveThread();

        goto exit;

    }

    u8len = WideCharToMultiByte(CP_UTF8, 0,

                                wbuf, total_read,

                                buf, u8len,

                                NULL, NULL);

    buf[u8len] = '\0';

exit:

    if (wbuf != wbuf_local) {

        PyMem_RawFree(wbuf);

    }

    if (err) {

        PyEval_RestoreThread(tstate);

        PyErr_SetFromWindowsErr(err);

        PyEval_SaveThread();

    }

    return buf;

}

#endif /* HAVE_WINDOWS_CONSOLE_IO */

/* Readline implementation using fgets() */

char *

PyOS_StdioReadline(FILE *sys_stdin, FILE *sys_stdout, const char *prompt)

{

    size_t n;

    char *p, *pr;

    PyThreadState *tstate = _PyOS_ReadlineTState;

    assert(tstate != NULL);

#ifdef HAVE_WINDOWS_CONSOLE_IO

    const PyConfig *config = _PyInterpreterState_GetConfig(tstate->interp);

    if (!config->legacy_windows_stdio && sys_stdin == stdin) {

        HANDLE hStdIn, hStdErr;

        hStdIn = _Py_get_osfhandle_noraise(fileno(sys_stdin));

        hStdErr = _Py_get_osfhandle_noraise(fileno(stderr));

        if (_get_console_type(hStdIn) == 'r') {

            fflush(sys_stdout);

            if (prompt) {

                if (_get_console_type(hStdErr) == 'w') {

                    wchar_t *wbuf;

                    int wlen;

                    wlen = MultiByteToWideChar(CP_UTF8, 0, prompt, -1,

                            NULL, 0);

                    if (wlen) {

                        wbuf = PyMem_RawMalloc(wlen * sizeof(wchar_t));

                        if (wbuf == NULL) {

                            PyEval_RestoreThread(tstate);

                            PyErr_NoMemory();

                            PyEval_SaveThread();

                            return NULL;

                        }

                        wlen = MultiByteToWideChar(CP_UTF8, 0, prompt, -1,

                                wbuf, wlen);

                        if (wlen) {

                            DWORD n;

                            fflush(stderr);

                            /* wlen includes null terminator, so subtract 1 */

                            WriteConsoleW(hStdErr, wbuf, wlen - 1, &n, NULL);

                        }

                        PyMem_RawFree(wbuf);

                    }

                } else {

                    fprintf(stderr, "%s", prompt);

                    fflush(stderr);

                }

            }

            clearerr(sys_stdin);

            return _PyOS_WindowsConsoleReadline(tstate, hStdIn);

        }

    }

#endif

    fflush(sys_stdout);

    if (prompt) {

        fprintf(stderr, "%s", prompt);

    }

    fflush(stderr);

    n = 0;

    p = NULL;

    do {

        size_t incr = (n > 0) ? n + 2 : 100;

        if (incr > INT_MAX) {

            PyMem_RawFree(p);

            PyEval_RestoreThread(tstate);

            PyErr_SetString(PyExc_OverflowError, "input line too long");

            PyEval_SaveThread();

            return NULL;

        }

        pr = (char *)PyMem_RawRealloc(p, n + incr);

        if (pr == NULL) {

            PyMem_RawFree(p);

            PyEval_RestoreThread(tstate);

            PyErr_NoMemory();

            PyEval_SaveThread();

            return NULL;

        }

        p = pr;

        int err = my_fgets(tstate, p + n, (int)incr, sys_stdin);

        if (err == 1) {

            // Interrupt

            PyMem_RawFree(p);

            return NULL;

        } else if (err != 0) {

            // EOF or error

            p[n] = '\0';

            break;

        }

        n += strlen(p + n);

    } while (p[n-1] != '\n');

    pr = (char *)PyMem_RawRealloc(p, n+1);

    if (pr == NULL) {

        PyMem_RawFree(p);

        PyEval_RestoreThread(tstate);

        PyErr_NoMemory();

        PyEval_SaveThread();

        return NULL;

    }

    return pr;

}

/* By initializing this function pointer, systems embedding Python can

   override the readline function.

   Note: Python expects in return a buffer allocated with PyMem_Malloc. */

char *(*PyOS_ReadlineFunctionPointer)(FILE *, FILE *, const char *) = NULL;

/* Interface used by file_tokenizer.c and bltinmodule.c */

char *

PyOS_Readline(FILE *sys_stdin, FILE *sys_stdout, const char *prompt)

{

    char *rv, *res;

    size_t len;

    PyThreadState *tstate = _PyThreadState_GET();

    if (_Py_atomic_load_ptr_relaxed(&_PyOS_ReadlineTState) == tstate) {

        PyErr_SetString(PyExc_RuntimeError,

                        "can't re-enter readline");

        return NULL;

    }

    // GH-123321: We need to acquire the lock before setting

    // _PyOS_ReadlineTState, otherwise the variable may be nullified by a

    // different thread.

    Py_BEGIN_ALLOW_THREADS

    PyMutex_Lock(&_PyOS_ReadlineLock);

    _Py_atomic_store_ptr_relaxed(&_PyOS_ReadlineTState, tstate);

    if (PyOS_ReadlineFunctionPointer == NULL) {

        PyOS_ReadlineFunctionPointer = PyOS_StdioReadline;

    }

    /* This is needed to handle the unlikely case that the

     * interpreter is in interactive mode *and* stdin/out are not

     * a tty.  This can happen, for example if python is run like

     * this: python -i < test1.py

     */

    if (!isatty(fileno(sys_stdin)) || !isatty(fileno(sys_stdout)) ||

        // GH-104668: Don't call global callbacks like PyOS_InputHook or

        // PyOS_ReadlineFunctionPointer from subinterpreters, since it seems

        // like there's no good way for users (like readline and tkinter) to

        // avoid using global state to manage them. Plus, we generally don't

        // want to cause trouble for libraries that don't know/care about

        // subinterpreter support. If libraries really need better APIs that

        // work per-interpreter and have ways to access module state, we can

        // certainly add them later (but for now we'll cross our fingers and

        // hope that nobody actually cares):

        !_Py_IsMainInterpreter(tstate->interp))

    {

        rv = PyOS_StdioReadline(sys_stdin, sys_stdout, prompt);

    }

    else {

        rv = (*PyOS_ReadlineFunctionPointer)(sys_stdin, sys_stdout, prompt);

    }

    // gh-123321: Must set the variable and then release the lock before

    // taking the GIL. Otherwise a deadlock or segfault may occur.

    _Py_atomic_store_ptr_relaxed(&_PyOS_ReadlineTState, NULL);

    PyMutex_Unlock(&_PyOS_ReadlineLock);

    Py_END_ALLOW_THREADS

    if (rv == NULL)

        return NULL;

    len = strlen(rv) + 1;

    res = PyMem_Malloc(len);

    if (res != NULL) {

        memcpy(res, rv, len);

    }

    else {

        PyErr_NoMemory();

    }

    PyMem_RawFree(rv);

    return res;

}