/* tinyproxy - A fast light-weight HTTP proxy
 * Copyright (C) 2003 Steven Young <sdyoung@miranda.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.
 */

/* This file contains source code for the handling and display of
 * HTML error pages with variable substitution.
 */

#include "tinyproxy.h"

#include "common.h"
#include "buffer.h"
#include "conns.h"
#include "heap.h"
#include "html-error.h"
#include "network.h"
#include "utils.h"

/*
 * Add an error number -> filename mapping to the errorpages list.
 */
#define ERRORNUM_BUFSIZE 8	/* this is more than required */
#define ERRPAGES_BUCKETCOUNT 16

int
add_new_errorpage (char *filepath, unsigned int errornum)
{
  char errornbuf[ERRORNUM_BUFSIZE];

  config.errorpages = hashmap_create (ERRPAGES_BUCKETCOUNT);
  if (!config.errorpages)
    return (-1);

  snprintf (errornbuf, ERRORNUM_BUFSIZE, "%u", errornum);

  if (hashmap_insert (config.errorpages, errornbuf,
		      filepath, strlen (filepath) + 1) < 0)
    return (-1);

  return (0);
}

/*
 * Get the file appropriate for a given error.
 */
static char *
get_html_file (unsigned int errornum)
{
  hashmap_iter result_iter;
  char errornbuf[ERRORNUM_BUFSIZE];
  char *key;
  static char *val;

  assert (errornum >= 100 && errornum < 1000);

  if (!config.errorpages)
    return (config.errorpage_undef);

  snprintf (errornbuf, ERRORNUM_BUFSIZE, "%u", errornum);

  result_iter = hashmap_find (config.errorpages, errornbuf);

  if (hashmap_is_end (config.errorpages, result_iter))
    return (config.errorpage_undef);

  if (hashmap_return_entry (config.errorpages, result_iter,
			    &key, (void **) &val) < 0)
    return (config.errorpage_undef);

  return (val);
}

/*
 * Look up the value for a variable.
 */
static char *
lookup_variable (struct conn_s *connptr, char *varname)
{
  hashmap_iter result_iter;
  char *key;
  static char *data;

  result_iter = hashmap_find (connptr->error_variables, varname);

  if (hashmap_is_end (connptr->error_variables, result_iter))
    return (NULL);

  if (hashmap_return_entry (connptr->error_variables, result_iter,
			    &key, (void **) &data) < 0)
    return (NULL);

  return (data);
}

#define HTML_BUFSIZE 4096

/*
 * Send an already-opened file to the client with variable substitution.
 */
int
send_html_file (FILE * infile, struct conn_s *connptr)
{
  char inbuf[HTML_BUFSIZE], *varstart = NULL, *p;
  char *varval;
  int in_variable = 0, writeret;

  while (fgets (inbuf, HTML_BUFSIZE, infile) != NULL)
    {
      for (p = inbuf; *p; p++)
	{
	  switch (*p)
	    {
	    case '}':
	      if (in_variable)
		{
		  *p = '\0';
		  if (!(varval = lookup_variable (connptr, varstart)))
		    varval = "(unknown)";
		  writeret = write_message (connptr->client_fd, "%s", varval);
		  if (writeret)
		    return (writeret);
		  in_variable = 0;
		}
	      else
		{
		  writeret = write_message (connptr->client_fd, "%c", *p);
		  if (writeret)
		    return (writeret);
		}
	      break;
	    case '{':
	      /* a {{ will print a single {.  If we are NOT
	       * already in a { variable, then proceed with
	       * setup.  If we ARE already in a { variable,
	       * this code will fallthrough to the code that
	       * just dumps a character to the client fd.
	       */
	      if (!in_variable)
		{
		  varstart = p + 1;
		  in_variable++;
		}
	      else
		in_variable = 0;
	    default:
	      if (!in_variable)
		{
		  writeret = write_message (connptr->client_fd, "%c", *p);
		  if (writeret)
		    return (writeret);
		}

	    }
	}
      in_variable = 0;
    }
  return (0);
}

int
send_http_headers (struct conn_s *connptr, int code, char *message)
{
  char *headers =
    "HTTP/1.0 %d %s\r\n"
    "Server: %s/%s\r\n"
    "Content-Type: text/html\r\n" "Connection: close\r\n" "\r\n";

  return (write_message (connptr->client_fd, headers,
			 code, message, PACKAGE, VERSION));
}

/*
 * Display an error to the client.
 */
int
send_http_error_message (struct conn_s *connptr)
{
  char *error_file;
  FILE *infile;
  int ret;
  char *fallback_error =
    "<?xml version=\"1.0\" encoding=\"UTF-8\" ?>\n"
    "<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.1//EN\" \"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd\">\n"
    "<html>\n"
    "<head><title>%d %s</title></head>\n"
    "<body>\n"
    "<h1>%s</h1>\n"
    "<p>%s</p>\n"
    "<hr />\n"
    "<p><em>Generated by %s version %s.</em></p>\n" "</body>\n" "</html>\n";

  send_http_headers (connptr, connptr->error_number, connptr->error_string);

  error_file = get_html_file (connptr->error_number);
  if (!(infile = fopen (error_file, "r")))
    {
      char *detail = lookup_variable (connptr, "detail");
      return (write_message (connptr->client_fd, fallback_error,
			     connptr->error_number,
			     connptr->error_string,
			     connptr->error_string,
			     detail, PACKAGE, VERSION));
    }

  ret = send_html_file (infile, connptr);
  fclose (infile);
  return (ret);
}

/*
 * Add a key -> value mapping for HTML file substitution.
 */

#define ERRVAR_BUCKETCOUNT 16

int
add_error_variable (struct conn_s *connptr, char *key, char *val)
{
  if (!connptr->error_variables)
    if (!(connptr->error_variables = hashmap_create (ERRVAR_BUCKETCOUNT)))
      return (-1);

  return hashmap_insert (connptr->error_variables, key, val,
			 strlen (val) + 1);
}

#define ADD_VAR_RET(x, y)				   \
	do {                                               \
                if (y == NULL)                             \
                        break;                             \
		if (add_error_variable(connptr, x, y) < 0) \
			return -1;			   \
	} while (0)

/*
 * Set some standard variables used by all HTML pages
 */
int
add_standard_vars (struct conn_s *connptr)
{
  char errnobuf[16];
  char timebuf[30];
  time_t global_time;

  snprintf (errnobuf, sizeof errnobuf, "%d", connptr->error_number);
  ADD_VAR_RET ("errno", errnobuf);

  ADD_VAR_RET ("cause", connptr->error_string);
  ADD_VAR_RET ("request", connptr->request_line);
  ADD_VAR_RET ("clientip", connptr->client_ip_addr);
  ADD_VAR_RET ("clienthost", connptr->client_string_addr);

  /* The following value parts are all non-NULL and will
   * trigger warnings in ADD_VAR_RET(), so we use
   * add_error_variable() directly.
   */

  global_time = time (NULL);
  strftime (timebuf, sizeof (timebuf), "%a, %d %b %Y %H:%M:%S GMT",
	    gmtime (&global_time));
  add_error_variable (connptr, "date", timebuf);

  add_error_variable (connptr, "website", "http://tinyproxy.banu.com/");
  add_error_variable (connptr, "version", VERSION);
  add_error_variable (connptr, "package", PACKAGE);

  return (0);
}

/*
 * Add the error information to the conn structure.
 */
int
indicate_http_error (struct conn_s *connptr, int number, char *message, ...)
{
  va_list ap;
  char *key, *val;

  va_start (ap, message);

  while ((key = va_arg (ap, char *)))
    {
      val = va_arg (ap, char *);

      if (add_error_variable (connptr, key, val) == -1)
	{
	  va_end (ap);
	  return (-1);
	}
    }

  connptr->error_number = number;
  connptr->error_string = safestrdup (message);

  va_end (ap);

  return (add_standard_vars (connptr));
}