/* Readline interface for tokenizer.c 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"
#ifdef MS_WINDOWS
#define WIN32_LEAN_AND_MEAN
#include "windows.h"
#endif /* MS_WINDOWS */

#ifdef __VMS
extern char* vms__StdioReadline(FILE *sys_stdin, FILE *sys_stdout, char *prompt);
#endif


PyThreadState* _PyOS_ReadlineTState;

#ifdef WITH_THREAD
#include "pythread.h"
static PyThread_type_lock _PyOS_ReadlineLock = NULL;
#endif

int (*PyOS_InputHook)(void) = NULL;

#ifdef RISCOS
int Py_RISCOSWimpFlag;
#endif

/* This function restarts a fgets() after an EINTR error occurred
  except if PyOS_InterruptOccurred() returns true. */

static int
my_fgets(char *buf, int len, FILE *fp)
{
       char *p;
       for (;;) {
               if (PyOS_InputHook != NULL)
                       (void)(PyOS_InputHook)();
               errno = 0;
               p = fgets(buf, len, fp);
               if (p != NULL)
                       return 0; /* No error */
#ifdef MS_WINDOWS
               /* In the case of a Ctrl+C or some other external event
                  interrupting the operation:
                  Win2k/NT: ERROR_OPERATION_ABORTED is the most recent Win32
                  error code (and feof() returns TRUE).
                  Win9x: Ctrl+C seems to have no effect on fgets() returning
                  early - the signal handler is called, but the fgets()
                  only returns "normally" (ie, when Enter hit or feof())
               */
               if (GetLastError()==ERROR_OPERATION_ABORTED) {
                       /* Signals come asynchronously, so we sleep a brief
                          moment before checking if the handler has been
                          triggered (we cant just return 1 before the
                          signal handler has been called, as the later
                          signal may be treated as a separate interrupt).
                       */
                       Sleep(1);
                       if (PyOS_InterruptOccurred()) {
                               return 1; /* Interrupt */
                       }
                       /* Either the sleep wasn't long enough (need a
                          short loop retrying?) or not interrupted at all
                          (in which case we should revisit the whole thing!)
                          Logging some warning would be nice.  assert is not
                          viable as under the debugger, the various dialogs
                          mean the condition is not true.
                       */
               }
#endif /* MS_WINDOWS */
               if (feof(fp)) {
                       return -1; /* EOF */
               }
#ifdef EINTR
               if (errno == EINTR) {
                       int s;
#ifdef WITH_THREAD
                       PyEval_RestoreThread(_PyOS_ReadlineTState);
#endif
                       s = PyErr_CheckSignals();
#ifdef WITH_THREAD
                       PyEval_SaveThread();
#endif
                       if (s < 0) {
                               return 1;
                       }
               }
#endif
               if (PyOS_InterruptOccurred()) {
                       return 1; /* Interrupt */
               }
               return -2; /* Error */
       }
       /* NOTREACHED */
}


/* Readline implementation using fgets() */

char *
PyOS_StdioReadline(FILE *sys_stdin, FILE *sys_stdout, char *prompt)
{
       size_t n;
       char *p;
       n = 100;
       if ((p = (char *)PyMem_MALLOC(n)) == NULL)
               return NULL;
       fflush(sys_stdout);
#ifndef RISCOS
       if (prompt)
               fprintf(stderr, "%s", prompt);
#else
       if (prompt) {
               if(Py_RISCOSWimpFlag)
                       fprintf(stderr, "\x0cr%s\x0c", prompt);
               else
                       fprintf(stderr, "%s", prompt);
       }
#endif
       fflush(stderr);
       switch (my_fgets(p, (int)n, sys_stdin)) {
       case 0: /* Normal case */
               break;
       case 1: /* Interrupt */
               PyMem_FREE(p);
               return NULL;
       case -1: /* EOF */
       case -2: /* Error */
       default: /* Shouldn't happen */
               *p = '\0';
               break;
       }
       n = strlen(p);
       while (n > 0 && p[n-1] != '\n') {
               size_t incr = n+2;
               p = (char *)PyMem_REALLOC(p, n + incr);
               if (p == NULL)
                       return NULL;
               if (incr > INT_MAX) {
                       PyErr_SetString(PyExc_OverflowError, "input line too long");
               }
               if (my_fgets(p+n, (int)incr, sys_stdin) != 0)
                       break;
               n += strlen(p+n);
       }
       return (char *)PyMem_REALLOC(p, n+1);
}


/* 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 *, char *);


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

char *
PyOS_Readline(FILE *sys_stdin, FILE *sys_stdout, char *prompt)
{
       char *rv;

       if (_PyOS_ReadlineTState == PyThreadState_GET()) {
               PyErr_SetString(PyExc_RuntimeError,
                               "can't re-enter readline");
               return NULL;
       }


       if (PyOS_ReadlineFunctionPointer == NULL) {
#ifdef __VMS
               PyOS_ReadlineFunctionPointer = vms__StdioReadline;
#else
               PyOS_ReadlineFunctionPointer = PyOS_StdioReadline;
#endif
       }

#ifdef WITH_THREAD
       if (_PyOS_ReadlineLock == NULL) {
               _PyOS_ReadlineLock = PyThread_allocate_lock();
       }
#endif

       _PyOS_ReadlineTState = PyThreadState_GET();
       Py_BEGIN_ALLOW_THREADS
#ifdef WITH_THREAD
       PyThread_acquire_lock(_PyOS_ReadlineLock, 1);
#endif

       /* 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)))
               rv = PyOS_StdioReadline (sys_stdin, sys_stdout, prompt);
       else
               rv = (*PyOS_ReadlineFunctionPointer)(sys_stdin, sys_stdout,
                                                    prompt);
       Py_END_ALLOW_THREADS

#ifdef WITH_THREAD
       PyThread_release_lock(_PyOS_ReadlineLock);
#endif

       _PyOS_ReadlineTState = NULL;

       return rv;
}