/*
 * Copyright (C) 1996-2000 Michael R. Elkins <me@mutt.org>
 * 
 *     This program is free software; you can redistribute it and/or modify
 *     it under the terms of the GNU General Public License as published by
 *     the Free Software Foundation; either version 2 of the License, or
 *     (at your option) any later version.
 * 
 *     This program 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 General Public License for more details.
 * 
 *     You should have received a copy of the GNU General Public License
 *     along with this program; if not, write to the Free Software
 *     Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */ 

#if HAVE_CONFIG_H
# include "config.h"
#endif

#include "mutt.h"
#include "history.h"

#include <stdint.h>

/* This history ring grows from 0..HistSize, with last marking the
 * where new entries go:
 *         0        the oldest entry in the ring
 *         1        entry
 *         ...
 *         x-1      most recently entered text
 *  last-> x        NULL  (this will be overwritten next)
 *         x+1      NULL
 *         ...
 *         HistSize NULL
 *
 * Once the array fills up, it is used as a ring.  last points where a new
 * entry will go.  Older entries are "up", and wrap around:
 *         0        entry
 *         1        entry
 *         ...
 *         y-1      most recently entered text
 *  last-> y        entry (this will be overwritten next)
 *         y+1      the oldest entry in the ring
 *         ...
 *         HistSize entry
 *
 * When $history_remove_dups is set, duplicate entries are scanned and removed
 * each time a new entry is added.  In order to preserve the history ring size,
 * entries 0..last are compacted up.  Entries last+1..HistSize are
 * compacted down:
 *         0        entry
 *         1        entry
 *         ...
 *         z-1      most recently entered text
 *  last-> z        entry (this will be overwritten next)
 *         z+1      NULL
 *         z+2      NULL
 *         ...
 *                  the oldest entry in the ring
 *                  next oldest entry
 *         HistSize entry
 */
struct history
{
  char **hist;
  short cur;
  short last;
}; 

/* global vars used for the string-history routines */

static struct history History[HC_LAST];
static int OldSize = 0;

#define GET_HISTORY(CLASS)	((CLASS >= HC_LAST) ? NULL : &History[CLASS])

static void init_history (struct history *h)
{
  int i;

  if(OldSize)
  {
    if (h->hist)
    {
      for (i = 0 ; i <= OldSize ; i ++)
	FREE (&h->hist[i]);
      FREE (&h->hist);
    }
  }
  
  if (HistSize)
    h->hist = safe_calloc (HistSize + 1, sizeof (char *));
  
  h->cur = 0;
  h->last = 0;
}

void mutt_read_histfile (void)
{
  FILE *f;
  int line = 0, hclass, read;
  char *linebuf = NULL, *p;
  size_t buflen;

  if ((f = fopen (HistFile, "r")) == NULL)
    return;

  while ((linebuf = mutt_read_line (linebuf, &buflen, f, &line, 0)) != NULL)
  {
    read = 0;
    if (sscanf (linebuf, "%d:%n", &hclass, &read) < 1 || read == 0 ||
        *(p = linebuf + strlen (linebuf) - 1) != '|' || hclass < 0)
    {
      mutt_error (_("Bad history file format (line %d)"), line);
      break;
    }
    /* silently ignore too high class (probably newer mutt) */
    if (hclass >= HC_LAST)
      continue;
    *p = '\0';
    p = safe_strdup (linebuf + read);
    if (p)
    {
      mutt_convert_string (&p, "utf-8", Charset, 0);
      mutt_history_add (hclass, p, 0);
      FREE (&p);
    }
  }

  safe_fclose (&f);
  FREE (&linebuf);
}

static int dup_hash_dec (HASH *dup_hash, char *s)
{
  struct hash_elem *elem;
  uintptr_t count;

  elem = hash_find_elem (dup_hash, s);
  if (!elem)
    return -1;

  count = (uintptr_t)elem->data;
  if (count <= 1)
  {
    hash_delete (dup_hash, s, NULL, NULL);
    return 0;
  }

  count--;
  elem->data = (void *)count;
  return count;
}

static int dup_hash_inc (HASH *dup_hash, char *s)
{
  struct hash_elem *elem;
  uintptr_t count;

  elem = hash_find_elem (dup_hash, s);
  if (!elem)
  {
    count = 1;
    hash_insert (dup_hash, s, (void *)count);
    return count;
  }

  count = (uintptr_t)elem->data;
  count++;
  elem->data = (void *)count;
  return count;
}

static void shrink_histfile (void)
{
  char tmpfname[_POSIX_PATH_MAX];
  FILE *f, *tmp = NULL;
  int n[HC_LAST] = { 0 };
  int line, hclass, read;
  char *linebuf = NULL, *p;
  size_t buflen;
  int regen_file = 0;
  HASH *dup_hashes[HC_LAST] = { 0 };

  if ((f = fopen (HistFile, "r")) == NULL)
    return;

  if (option (OPTHISTREMOVEDUPS))
    for (hclass = 0; hclass < HC_LAST; hclass++)
      dup_hashes[hclass] = hash_create (MAX (10, SaveHist * 2), MUTT_HASH_STRDUP_KEYS);

  line = 0;
  while ((linebuf = mutt_read_line (linebuf, &buflen, f, &line, 0)) != NULL)
  {
    if (sscanf (linebuf, "%d:%n", &hclass, &read) < 1 || read == 0 ||
        *(p = linebuf + strlen (linebuf) - 1) != '|' || hclass < 0)
    {
      mutt_error (_("Bad history file format (line %d)"), line);
      goto cleanup;
    }
    /* silently ignore too high class (probably newer mutt) */
    if (hclass >= HC_LAST)
      continue;
    *p = '\0';
    if (option (OPTHISTREMOVEDUPS) &&
        (dup_hash_inc (dup_hashes[hclass], linebuf + read) > 1))
    {
      regen_file = 1;
      continue;
    }
    n[hclass]++;
  }

  if (!regen_file)
    for(hclass = HC_FIRST; hclass < HC_LAST; hclass++)
      if (n[hclass] > SaveHist)
      {
        regen_file = 1;
        break;
      }

  if (regen_file)
  {
    mutt_mktemp (tmpfname, sizeof (tmpfname));
    if ((tmp = safe_fopen (tmpfname, "w+")) == NULL)
    {
      mutt_perror (tmpfname);
      goto cleanup;
    }
    rewind (f);
    line = 0;
    while ((linebuf = mutt_read_line (linebuf, &buflen, f, &line, 0)) != NULL)
    {
      if (sscanf (linebuf, "%d:%n", &hclass, &read) < 1 || read == 0 ||
          *(p = linebuf + strlen (linebuf) - 1) != '|' || hclass < 0)
      {
        mutt_error (_("Bad history file format (line %d)"), line);
        goto cleanup;
      }
      if (hclass >= HC_LAST)
	continue;
      *p = '\0';
      if (option (OPTHISTREMOVEDUPS) &&
          (dup_hash_dec (dup_hashes[hclass], linebuf + read) > 0))
        continue;
      *p = '|';
      if (n[hclass]-- <= SaveHist)
        fprintf (tmp, "%s\n", linebuf);
    }
  }

cleanup:
  safe_fclose (&f);
  FREE (&linebuf);
  if (tmp != NULL)
  {
    if (fflush (tmp) == 0 &&
        (f = fopen (HistFile, "w")) != NULL) /* __FOPEN_CHECKED__ */
    {
      rewind (tmp);
      mutt_copy_stream (tmp, f);
      safe_fclose (&f);
    }
    safe_fclose (&tmp);
    unlink (tmpfname);
  }
  if (option (OPTHISTREMOVEDUPS))
    for (hclass = 0; hclass < HC_LAST; hclass++)
      hash_destroy (&dup_hashes[hclass], NULL);
}

static void save_history (history_class_t hclass, const char *s)
{
  static int n = 0;
  FILE *f;
  char *tmp, *p;

  if (!s || !*s)  /* This shouldn't happen, but it's safer. */
    return;

  if ((f = fopen (HistFile, "a")) == NULL)
  {
    mutt_perror ("fopen");
    return;
  }

  tmp = safe_strdup (s);
  mutt_convert_string (&tmp, Charset, "utf-8", 0);

  /* Format of a history item (1 line): "<histclass>:<string>|".
     We add a '|' in order to avoid lines ending with '\'. */
  fprintf (f, "%d:", (int) hclass);
  for (p = tmp; *p; p++)
  {
    /* Don't copy \n as a history item must fit on one line. The string
       shouldn't contain such a character anyway, but as this can happen
       in practice, we must deal with that. */
    if (*p != '\n')
      putc ((unsigned char) *p, f);
  }
  fputs ("|\n", f);

  safe_fclose (&f);
  FREE (&tmp);

  if (--n < 0)
  {
    n = SaveHist;
    shrink_histfile();
  }
}

/* When removing dups, we want the created "blanks" to be right below the
 * resulting h->last position.  See the comment section above 'struct history'.
 */
static void remove_history_dups (history_class_t hclass, const char *s)
{
  int source, dest, old_last;
  struct history *h = GET_HISTORY(hclass);

  if (!HistSize || !h)
    return; /* disabled */

  /* Remove dups from 0..last-1 compacting up. */
  source = dest = 0;
  while (source < h->last)
  {
    if (!mutt_strcmp (h->hist[source], s))
      FREE (&h->hist[source++]);
    else
      h->hist[dest++] = h->hist[source++];
  }

  /* Move 'last' entry up. */
  h->hist[dest] = h->hist[source];
  old_last = h->last;
  h->last = dest;

  /* Fill in moved entries with NULL */
  while (source > h->last)
    h->hist[source--] = NULL;

  /* Remove dups from last+1 .. HistSize compacting down. */
  source = dest = HistSize;
  while (source > old_last)
  {
    if (!mutt_strcmp (h->hist[source], s))
      FREE (&h->hist[source--]);
    else
      h->hist[dest--] = h->hist[source--];
  }

  /* Fill in moved entries with NULL */
  while (dest > old_last)
    h->hist[dest--] = NULL;
}

void mutt_init_history(void)
{
  history_class_t hclass;
  
  if (HistSize == OldSize)
    return;
  
  for(hclass = HC_FIRST; hclass < HC_LAST; hclass++)
    init_history(&History[hclass]);

  OldSize = HistSize;
}
  
void mutt_history_add (history_class_t hclass, const char *s, int save)
{
  int prev;
  struct history *h = GET_HISTORY(hclass);

  if (!HistSize || !h)
    return; /* disabled */

  if (*s)
  {
    prev = h->last - 1;
    if (prev < 0) prev = HistSize;

    /* don't add to prompt history:
     *  - lines beginning by a space
     *  - repeated lines
     */
    if (*s != ' ' && (!h->hist[prev] || mutt_strcmp (h->hist[prev], s) != 0))
    {
      if (option (OPTHISTREMOVEDUPS))
        remove_history_dups (hclass, s);
      if (save && SaveHist)
        save_history (hclass, s);
      mutt_str_replace (&h->hist[h->last++], s);
      if (h->last > HistSize)
	h->last = 0;
    }
  }
  h->cur = h->last; /* reset to the last entry */
}

char *mutt_history_next (history_class_t hclass)
{
  int next;
  struct history *h = GET_HISTORY(hclass);

  if (!HistSize || !h)
    return (""); /* disabled */

  next = h->cur;
  do
  {
    next++;
    if (next > HistSize)
      next = 0;
    if (next == h->last)
      break;
  } while (h->hist[next] == NULL);

  h->cur = next;
  return (h->hist[h->cur] ? h->hist[h->cur] : "");
}

char *mutt_history_prev (history_class_t hclass)
{
  int prev;
  struct history *h = GET_HISTORY(hclass);

  if (!HistSize || !h)
    return (""); /* disabled */

  prev = h->cur;
  do
  {
    prev--;
    if (prev < 0)
      prev = HistSize;
    if (prev == h->last)
      break;
  } while (h->hist[prev] == NULL);

  h->cur = prev;
  return (h->hist[h->cur] ? h->hist[h->cur] : "");
}

void mutt_reset_history_state (history_class_t hclass)
{
  struct history *h = GET_HISTORY(hclass);

  if (!HistSize || !h)
    return; /* disabled */

  h->cur = h->last;
}

int mutt_history_at_scratch (history_class_t hclass)
{
  struct history *h = GET_HISTORY(hclass);

  if (!HistSize || !h)
    return 0; /* disabled */

  return h->cur == h->last;
}

void mutt_history_save_scratch (history_class_t hclass, const char *s)
{
  struct history *h = GET_HISTORY(hclass);

  if (!HistSize || !h)
    return; /* disabled */

  /* Don't check if s has a value because the scratch buffer may contain
   * an old garbage value that should be overwritten */
  mutt_str_replace (&h->hist[h->last], s);
}