/* -*- c -*- */
/**
 * libgamma — Display server abstraction layer for gamma ramp adjustments
 * Copyright © 2014  Mattias Andrée (maandree@member.fsf.org)
 * 
 * This library 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 3 of the License, or
 * (at your option) any later version.
 * 
 * This library 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 library.  If not, see <http://www.gnu.org/licenses/>.
 */
#include "libgamma-error.h"


#include <stddef.h>
#include <sys/types.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>



$>set -u
$>cd src/extract
$>export PATH=".:${PATH}"



/**
 * Group that the user needs to be a member of if
 * `LIBGAMMA_DEVICE_REQUIRE_GROUP` is returned.
 */
gid_t libgamma_group_gid = 0;

/**
 * Group that the user needs to be a member of if
 * `LIBGAMMA_DEVICE_REQUIRE_GROUP` is returned,
 * `NULL` if the name of the group `libgamma_group_gid`
 * cannot be determined.
 */
const char* libgamma_group_name = NULL;



/**
 * Prints an error to stderr in a `perror` fashion,
 * however this function will not translate the `libgamma`
 * errors into human-readable strings, it will simply
 * print the name of the error. If the value `error_code`
 * is the value of `LIBGAMMA_ERRNO_SET`, `perror` will be
 * used to print the current error stored in `errno`.
 * If `error_code` is non-negative (an `errno` value`), that
 * value will be stored in `errno` and `perror` will be
 * used to print it. Additionally, if the `error_code` is
 * the value of `LIBGAMMA_DEVICE_REQUIRE_GROUP` the
 * required group will be printed with its numerical value
 * and, if known, its name.
 * 
 * @param  name   The text to add at the beginning.
 * @param  value  The error code, may be an `errno` value.
 */
void libgamma_perror(const char* name, int error_code)
{
  if (error_code >= 0)
    {
      /* Print the stored errno value. */
      errno = error_code;
      perror(name);
    }
  else if (error_code == LIBGAMMA_ERRNO_SET)
    /* Print errno. */
    perror(name);
  else if (error_code == LIBGAMMA_DEVICE_REQUIRE_GROUP)
    {
      /* Print the error name and the required group membership. */
      const char* error = libgamma_name_of_error(error_code);
      long int gid = (long int)libgamma_group_gid;
      if (libgamma_group_name == NULL)
	/* Group name unknown. */
	fprintf(stderr, "%s: %s: %ld\n", name, error, gid);
      else
	/* Group name known, ID is second class. */
	fprintf(stderr, "%s: %s: %s (%ld)\n", name, error, libgamma_group_name, gid);
    }
  else if (error_code < LIBGAMMA_ERROR_MIN)
    /* If the error code does not exist, print "(?)" */
    fprintf(stderr, "%s: (?)\n", name);
  else
    /* Print the name of the error. */
    fprintf(stderr, "%s: %s\n", name, libgamma_name_of_error(error_code));
}


/**
 * Returns the name of the definition associated with a `libgamma` error code.
 * 
 * @param   value  The error code.
 * @return         The name of the definition associated with the error code,
 *                 `NULL` if the error code does not exist. The return string
 *                 should not be `free`:d.
 */
const char* libgamma_name_of_error(int value)
{
  /* Map from error codes to error names.
     The output of $(libgamma-error-extract --list)
     is sorted by error code in decreasing order. */
  static const char* error_names[] =
    {
$>for error in $(libgamma-error-extract --list); do
      "${error}",
$>done
    };
  
  /* Return `NULL` if the error code is invalid. */
  if ((value < LIBGAMMA_ERROR_MIN) || (value >= 0))
    return NULL;
  
  /* Convert error code from {-1, -2, -3, ...} to {0, 1, 2, ...}
     and look up the error's name and return it. */
  return error_names[-value - 1];
}


/**
 * Return the value of a `libgamma` error definition refered to by name.
 * 
 * @param   name  The name of the definition associated with the error code.
 * @return        The error code, zero if the name does is `NULL`
 *                or does not refer to a `libgamma` error.
 */
int libgamma_value_of_error(const char* name)
{
  /* Return 0 (not a valid error code) if the error name is `NULL`. */
  if (name == NULL)
    return 0;
  
  /* Test error names against `name` and return the value of the match error. */
$>for error in $(libgamma-error-extract --list); do
  if (!strcmp(name, "${error}"))  return ${error};
$>done
  
  /* Return 0 (not a valid error code) if the error name is unknown. */
  return 0;
}