Drupal 7 : Add translation programmatically

gistfile1.php

<?php

$report = array(
  'skips'=>0,
  'updates'=>0,
  'deletes'=>0,
  'additions'=>0
); // ??
$source = "Sometime drupal sucks";
$translation = "Drupal C DLA BALLE";
$textgroup = 'default'; // field , node, default, menu ...
$langcode = 'fr'; // 'en', 'de'
$mode = LOCALE_IMPORT_OVERWRITE; // LOCALE_IMPORT_KEEP
$location = ''; //  'menu:menu:management:title', '/node/3', ...

_locale_import_one_string_db($report, $langcode, $context, $source, $translation, $textgroup, $location, $mode);

// Clear locale cache.
cache_clear_all('locale:', 'cache', TRUE);

gistfile2.php

<?php
// From https://fosswiki.liip.ch/display/DRUPAL/Script+creation+of+languages+and+import+po+files
/**
 * Add translations from a PO file.
 * This will populate the locales_target table in the database
 * with the strings from the PO file.
 *
 * @param $langcode string (e.g. fr, de, it)
 * @param $poFile string full path to .po file
 * @param $mode const LOCALE_IMPORT_OVERWRITE (overwrite existing translations) or LOCALE_IMPORT_KEEP (only import new strings)
 * @param $group string Text group to import PO file into (eg. 'default' for interface translations)
 * @param $add_language_options array optional parameters for locale_add_language (name, native, direction, domain, prefix, enabled, default)
 * @return bool success
 */
function project_update_load_language($langcode, $poFile, $mode=LOCALE_IMPORT_OVERWRITE, $group='default', $add_language_options=array()) {
  $add_language_defaults = array(
    'name' => NULL,
    'native' => NULL,
    'direction' => LANGUAGE_LTR,
    'domain' => '',
    'prefix' => '',
    'enabled' => TRUE,
    'default' => FALSE,
  );
  $options = array_merge($add_language_defaults, $add_language_options);
  locale_add_language($langcode, $options['name'], $options['native'], $options['direction'],
    $options['domain'], $options['prefix'], $options['enabled'], $options['default']);
  // mimic a drupal uploaded file object, with the necessary info needed by _locale_import_po
  $file = new stdClass;
  $file->filepath = $poFile;
  $file->filename = basename($poFile);
  return _locale_import_po($file, $langcode, $mode, $group);
}
 
/**
 * Find all po files under a given path
 *
 * @param $path string
 * @param $recurse boolean
 * @return array of string paths to po files
 */
function project_find_po_files($path, $recurse=TRUE) {
  $path = rtrim($path, '/') . '/*';
  $pattern = '/\.po$/';
  $files = array();
  foreach (glob ($path) as $fullname) {
    if ($recurse && is_dir($fullname)) {
      $files = array_merge($files, project_find_po_files($fullname, $recurse));
    } else if (preg_match($pattern, $fullname)) {
      $files[] = $fullname;
    }
  }
  return $files;
}

Thanks ! Agreed that Drupal 7 sucks at string translation API ;) But Drupal 8 fixed it !