/* $Id: split_mangled_mailbox.cc 2845 2007-12-02 13:43:57Z flaterco $ */
// g++ -Wall -Wextra -pedantic -O2 -s -o split_mangled_mailbox split_mangled_mailbox.cc -ldstr

// For reasons unknown, mail processing system does this to the
// envelope From:
//
//   >From dave@fubar.com Sun Dec 02 00:11:06 2007

// Causing getmail to do this:
//
//   From unknown Sat Dec  1 19:11:23 2007
//   Return-Path: <unknown>
//   Received: from mail.fubar.com by endpoint.nowhere.net
//     with IMAP4-SSL; 02 Dec 2007 00:11:23 -0000
//
//   >From dave@fubar.com Sun Dec 02 00:11:06 2007

// Mutt then makes it worse:
//
//   From unknown Sat Dec  1 19:06:33 2007
//   Return-Path: <unknown>
//   Status: O
//   Content-Length: 1720
//   Lines: 40
//
//   >From dave@fubar.com Sun Dec 02 00:01:18 2007

// This program recovers the original e-mail from a "standard" mbox
// mailbox that has been the victim of such mangling.

// Based on split_std_mailbox.cc 2442 2007-04-19 01:26:54Z flaterco


#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <Dstr>


FILE *newmsg (char *dest_dir) {
  static const unsigned bufsize = 1000;
  static unsigned long serialnum = 0;
  size_t l;
  char msgfilename[bufsize];
  FILE *fp;
  struct stat stat_struct;

  l = strlen(dest_dir);
  assert (l > 0);
  assert (l + 80 < bufsize);
  strcpy (msgfilename, dest_dir);
  if (msgfilename[l-1] != '/')
    msgfilename[l++] = '/';
  do
    sprintf (msgfilename+l, "msg%lu", serialnum++);
  while (stat (msgfilename, &stat_struct) == 0);
  if (!(fp = fopen (msgfilename, "w"))) {
    perror (msgfilename);
    fprintf (stderr, "Aborting run\n");
    exit (-1);
  }
  return fp;
}


int main (int argc, char **argv) {
  FILE *mbox, *msg=NULL;
  Dstr inbuf;

  if (argc != 3) {
    fprintf (stderr, "Usage:  split_mangled_mailbox mangled-mailbox-filename destination-directory\n");
    exit (-1);
  }
  if (!(mbox = fopen (argv[1], "r"))) {
    perror (argv[1]);
    exit (-1);
  }

  while (!inbuf.getline(mbox).isNull()) {
    if (!strncmp (inbuf.aschar(), "From unknown ", 13)) {
      if (msg)
        fclose (msg);
      msg = newmsg (argv[2]);
      do {
        inbuf.getline(mbox);
        if (inbuf.isNull()) {
          fprintf (stderr, "Error:  unexpected end of mbox file\n");
          exit (-1);
        }
      } while (strncmp (inbuf.aschar(), ">From ", 6));
      inbuf /= 1;
    }
    if (!msg) {
      fprintf (stderr, "Error:  mbox file does not begin as expected.\n");
      exit (-1);
    }
    fprintf (msg, "%s\n", inbuf.aschar());
  }

  fclose (mbox);
  if (msg)
    fclose (msg);
  return 0;
}