/*
Serval DNA configuration
Copyright (C) 2012 Serval Project Inc.

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.
*/

#include <stdio.h>
#include <sys/stat.h>
#include <ctype.h>
#include <time.h>
#include <inttypes.h> // for PRIu64 on Android
#include "conf.h"
#include "instance.h"
#include "log.h"
#include "debug.h"
#include "str.h"
#include "mem.h"
#include "os.h"

#define CONFFILE_NAME		  "serval.conf"

struct cf_om_node *cf_om_root = NULL;
static __thread struct file_meta conffile_meta = FILE_META_UNKNOWN;

__thread int cf_initialised = 0;
__thread int cf_limbo = 1;
__thread struct config_main config;
static __thread struct file_meta config_meta = FILE_META_UNKNOWN;

static const char *conffile_path()
{
  static char path[1024] = "";
  if (!path[0] && !FORMF_SERVAL_ETC_PATH(path, CONFFILE_NAME))
    abort();
  return path;
}

static int reload(const char *path, int *resultp)
{
  DEBUGF(config, "    file path=%s", alloca_str_toprint(path));
  struct file_meta meta;
  if (get_file_meta(path, &meta) == -1)
    return -1;
  DEBUGF(config, "    file meta=%s", alloca_file_meta(&meta));
  DEBUGF(config, "conffile_meta=%s", alloca_file_meta(&conffile_meta));
  if (cmp_file_meta(&meta, &conffile_meta) == 0)
    return 0;
  if (conffile_meta.mtime.tv_sec != -1)
    INFOF("config file %s -- detected new version", path);
  char *buf = NULL;
  if (meta.mtime.tv_sec == -1) {
    WARNF("config file %s does not exist -- using all defaults", path);
  } else if (meta.size > CONFIG_FILE_MAX_SIZE) {
    WHYF("config file %s is too big (%ju bytes exceeds limit %d)", path, (uintmax_t)meta.size, CONFIG_FILE_MAX_SIZE);
    return -1;
  } else if (meta.size <= 0) {
    WARNF("config file %s is zero size -- using all defaults", path);
  } else {
    FILE *f = fopen(path, "r");
    if (f == NULL) {
      WHYF_perror("fopen(%s)", path);
      return -1;
    }
    if ((buf = emalloc(meta.size)) == NULL) {
      fclose(f);
      return -1;
    }
    if (fread(buf, meta.size, 1, f) != 1) {
      if (ferror(f))
	WHYF_perror("fread(%s, %"PRIu64")", path, (uint64_t) meta.size);
      else
	WHYF("fread(%s, %"PRIu64") hit EOF", path, (uint64_t) meta.size);
      free(buf);
      fclose(f);
      return -1;
    }
    if (fclose(f) == EOF) {
      WHYF_perror("fclose(%s)", path);
      free(buf);
      return -1;
    }
    DEBUGF(config, "config file %s successfully read %ld bytes", path, (long) meta.size);
  }
  conffile_meta = meta;
  DEBUGF(config, "set conffile_meta=%s", alloca_file_meta(&conffile_meta));
  struct cf_om_node *new_root = NULL;
  *resultp = cf_om_parse(path, buf, meta.size, &new_root);
  free(buf);
  if (*resultp == CFERROR)
    return -1;
  cf_om_free_node(&cf_om_root);
  cf_om_root = new_root;
  return 1;
}

int cf_om_reload()
{
  int result;
  return reload(conffile_path(), &result);
}

int cf_om_load()
{
  conffile_meta = FILE_META_UNKNOWN;
  return cf_om_reload();
}

int cf_om_save()
{
  if (cf_om_root) {
    const char *path = conffile_path();
    struct file_meta meta;
    if (get_file_meta(path, &meta) == -1)
      return -1;
    char tempfile[1024];
    FILE *outf = NULL;
    if (!FORMF_SERVAL_ETC_PATH(tempfile, CONFFILE_NAME ".temp"))
      return -1;
    if ((outf = fopen(tempfile, "w")) == NULL)
      return WHYF_perror("fopen(%s, \"w\")", tempfile);
    struct cf_om_iterator it;
    for (cf_om_iter_start(&it, cf_om_root); it.node; cf_om_iter_next(&it))
      if (it.node->text)
	fprintf(outf, "%s=%s\n", it.node->fullkey, it.node->text);
    if (fclose(outf) == EOF)
      return WHYF_perror("fclose(%s)", tempfile);
    // rename(2) is atomic, so no other process will read a half-written file.
    if (rename(tempfile, path)) {
      WHYF_perror("rename(%s, %s)", tempfile, path);
      unlink(tempfile);
      return -1;
    }
    struct file_meta newmeta;
    int r = alter_file_meta(path, &meta, &newmeta);
    if (r == -1)
      return -1;
    if (r)
      DEBUGF(config, "wrote %s; set mtime=%s", path, alloca_time_t(newmeta.mtime.tv_sec));
    else if (cmp_file_meta(&meta, &newmeta) == 0)
      WARNF("wrote %s; mtime not altered", path);
    else
      DEBUGF(config, "wrote %s", path);
    conffile_meta = newmeta;
    DEBUGF(config, "set conffile_meta=%s", alloca_file_meta(&conffile_meta));
  }
  return 0;
}

int cf_init()
{
  if (!cf_initialised) {
    memset(&config, 0, sizeof config);
    if (cf_dfl_config_main(&config) == CFERROR)
      return -1;
    conffile_meta = config_meta = FILE_META_UNKNOWN;
    cf_limbo = 1;
    cf_initialised = 1;
  }
  return 0;
}

/* (Re-)load and parse the configuration file.
 *
 * The 'strict' flag controls whether this function will load a defective config file.  If nonzero,
 * then it will not load a defective file, but will log an error and return -1.  If zero, then it
 * will load a defective file and use the 'permissive' flag to decide what to log and return.
 *
 * The 'permissive' flag only applies if 'strict' is zero, and determines how this function deals
 * with a loaded defective config file.  If 'permissive' is zero, then it logs an error and returns
 * -1.  If nonzero, then it logs a warning and returns 0.
 *
 * @author Andrew Bettison <andrew@servalproject.com>
 */
static int reload_and_parse(int permissive, int strict)
{
  int result = CFOK;
  int changed = 0;
  assert(cf_initialised);
  if (cf_limbo)
    result = cf_dfl_config_main(&config);
  if (result == CFOK || result == CFEMPTY) {
    if (reload(conffile_path(), &result) == -1)
      result = CFERROR;
    else if (!cf_limbo && cmp_file_meta(&conffile_meta, &config_meta) == 0)
      return 0;
    else {
      config_meta = conffile_meta;
      if (result == CFOK || result == CFEMPTY) {
	struct config_main new_config;
	int update = 0;
	memset(&new_config, 0, sizeof new_config);
	result = cf_dfl_config_main(&new_config);
	if (result == CFOK || result == CFEMPTY) {
	  result = cf_om_root ? cf_opt_config_main(&new_config, cf_om_root) : CFEMPTY;
	  if (result == CFOK || result == CFEMPTY) {
	    result = CFOK;
	    update = 1;
	  } else if (result != CFERROR && !strict) {
	    result &= ~CFEMPTY; // don't log "empty" as a problem
	    update = 1;
	  }
	}
	if (update && cf_cmp_config_main(&config, &new_config) != 0) {
	  config = new_config;
	  changed = 1;
	}
      }
    }
  }
  int ret = changed;
  if (result != CFOK) {
    strbuf b = strbuf_alloca(180);
    strbuf_cf_flag_reason(b, result);
    if (strict)
      ret = WHYF("defective config file %s not loaded -- %s", conffile_path(), strbuf_str(b));
    else {
      if (!permissive)
	ret = WHYF("config file %s loaded despite defects -- %s", conffile_path(), strbuf_str(b));
      else
	WARNF("config file %s loaded despite defects -- %s", conffile_path(), strbuf_str(b));
    }
  }
  cf_limbo = 0; // let log messages out
  logFlush();
  if (changed) {
    CALL_TRIGGER(conf_log);
    CALL_TRIGGER(conf_change);
  }
  return ret;
}

// Put a dummy no-op trigger callback into the "config_change" and "config_log" trigger sections,
// otherwise if no other object provides one, the link will fail with errors like:
// undefined reference to `__start_tr_config_change'
// undefined reference to `__stop_tr_config_change'

static void __dummy_on_config_log();
DEFINE_TRIGGER(conf_log, __dummy_on_config_log);
static void __dummy_on_config_log() {}

static void __dummy_on_config_change();
DEFINE_TRIGGER(conf_change, __dummy_on_config_change);
static void __dummy_on_config_change() {}

// The configuration API entry points.

int cf_load()
{
  conffile_meta = config_meta = FILE_META_UNKNOWN;
  return reload_and_parse(0, 0);
}

int cf_load_strict()
{
  conffile_meta = config_meta = FILE_META_UNKNOWN;
  return reload_and_parse(0, 1);
}

int cf_load_permissive()
{
  conffile_meta = config_meta = FILE_META_UNKNOWN;
  return reload_and_parse(1, 0);
}

int cf_reload()
{
  return reload_and_parse(0, 0);
}

int cf_reload_strict()
{
  return reload_and_parse(0, 1);
}

int cf_reload_permissive()
{
  return reload_and_parse(1, 0);
}