Bug 9735 - Let the language be selected through URL parameters

Passing language=<valid_language_code> as a parameter in any Koha's URL
can be used to set the desired language.
This patch touches
 - C4::Templates
 - C4::Auth

Adds a new method getlanguagecookie that does exactly that, for use in
get_template_and_user.
Also modifies getlanguage so it checks (a) if there's a 'language'
parameter in the CGI object and (b) checks if its valid and enabled for
the desired interface.

To test:
* Without the patch
  - access any koha page
  - add ?language=code to the end of the URL (change code for a valid language code
    it needs to be installed using perl translate install code, and enabled either for
    the staff or opac interface, depending where are you testing)
  - Nothing happens with the language parameter
* With the patch
  - access any koha page
  - add ?language=code (the same as before) and hit enter
  - the language should be changed to the one you chose
  - if you browse through some links, you will see
    koha 'remembers' the language you passed as a parameter
    (i.e. the language cookie has been updated).

Sponsored-by: Universidad Nacional de Córdoba
Signed-off-by: Brendan <brendan@bywatersolutions.com>
Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>

Comment: Works very well. No errors.
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Passes all tests and QA script.
More comments on last patch.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>

C4/Auth.pm

@@ -461,6 +461,16 @@ sub get_template_and_user {
 
         $template->param(OpacPublic => '1') if ($user || C4::Context->preference("OpacPublic"));
     }
+
+    # Check if we were asked using parameters to force a specific language
+    if ( defined $in->{'query'}->param('language') ) {
+        # Extract the language, let C4::Templates::getlanguage choose
+        # what to do
+        my $language = C4::Templates::getlanguage($in->{'query'},$in->{'type'});
+        my $languagecookie = C4::Templates::getlanguagecookie($in->{'query'},$language);
+        $cookie = [$cookie, $languagecookie];
+    }
+
     return ( $template, $borrowernumber, $cookie, $flags);
 }
 

C4/Templates.pm

@@ -316,17 +316,49 @@ sub setlanguagecookie {
     );
 }
 
+=head2 getlanguagecookie
+
+    my $cookie = getlanguagecookie($query,$language);
+
+Returns a cookie object containing the calculated language to be used.
+
+=cut
+
+sub getlanguagecookie {
+    my ( $query, $language ) = @_;
+    my $cookie = $query->cookie(
+        -name    => 'KohaOpacLanguage',
+        -value   => $language,
+        -HttpOnly => 1,
+        -expires => '+3y'
+    );
+
+    return $cookie;
+}
+
+=head2 getlanguage
+
+    Select a language based on the URL parameter 'language', a cookie,
+    syspref available languages & browser
+
+=cut
 
 sub getlanguage {
     my ($query, $interface) = @_;
 
-    # Select a language based on cookie, syspref available languages & browser
     my $preference_to_check =
       $interface eq 'intranet' ? 'language' : 'opaclanguages';
+    # Get the available/valid languages list
     my @languages = split /,/, C4::Context->preference($preference_to_check);
 
     my $lang;
 
+    # Chose language from the URL
+    $lang = $query->param( 'language' );
+    if ( defined $lang && any { $_ eq $lang } @languages) {
+        return $lang;
+    }
+
     # cookie
     if ( $query->cookie('KohaOpacLanguage') ) {
         $lang = $query->cookie('KohaOpacLanguage');