package Dancer::Session::Abstract;
use strict;
use warnings;
use Carp;

use base 'Dancer::Engine';

use Dancer::Config 'setting';
use Dancer::Cookies;
use File::Spec;

__PACKAGE__->attributes('id');

# args: ($class, $id)
# receives a session id and should return a session object if found, or undef
# otherwise.
sub retrieve {
    confess "retrieve not implemented";
}

# args: ($class)
# create a new empty session, flush it and return it.
sub create {
    confess "create not implemented";
}

# args: ($self)
# write the (serialized) current session to the session storage
sub flush {
    confess "flush not implemented";
}

# args: ($self)
# remove the session from the session storage
sub destroy {
    confess "destroy not implemented";
}

# does nothing in most cases (exception is YAML)
sub reset {
    return;
}

# This is the default constructor for the session object, the only mandatory
# attribute is 'id'. The whole object should be serialized by the session
# engine.
# If you override this constructor, remember to call $self->SUPER::init() so
# that the session ID is still generated.
sub init {
    my ($self) = @_;
    $self->id(build_id());
}

# this method can be overwritten in any Dancer::Session::* module
sub session_name {
    setting('session_name') || 'dancer.session';
}


# Methods below this this line should not be overloaded.

# we try to make the best random number
# with native Perl 5 code.
# to rebuild a session id, an attacker should know:
# - the running PID of the server
# - the current timestamp of the time it was built
# - the path of the installation directory
# - guess the correct number between 0 and 1000000000
# - should be able to reproduce that 3 times
sub build_id {
    my $session_id = "";
    foreach my $seed (rand(1000), rand(1000), rand(1000)) {
        my $c = 0;
        $c += ord($_) for (split //, File::Spec->rel2abs(File::Spec->curdir));
        my $current = int($seed * 1000000000) + time + $$ + $c;
        $session_id .= $current;
    }
    return $session_id;
}

sub read_session_id {
    my $name = session_name();
    my $c = Dancer::Cookies->cookies->{$name};
    return (defined $c) ? $c->value : undef;
}

sub write_session_id {
    my ($class, $id) = @_;

    my $name = session_name();
    my %cookie = (
        name   => $name,
        value  => $id,
        domain => setting('session_domain'),
        secure => setting('session_secure'),
        http_only => defined(setting("session_is_http_only")) ?
                     setting("session_is_http_only") : 1,
    );
    if (my $expires = setting('session_expires')) {
        # It's # of seconds from the current time
        # Otherwise just feed it through.
        $expires = Dancer::Cookie::_epoch_to_gmtstring(time + $expires) if $expires =~ /^\d+$/;
        $cookie{expires} = $expires;
    }

    my $c = Dancer::Cookie->new(%cookie);
    Dancer::Cookies->set_cookie_object($name => $c);
}

1;
__END__

=pod

=head1 NAME

Dancer::Session::Abstract - abstract class for session engine

=head1 SPEC

=over 4

=item B<role>

A Dancer::Session object represents a session engine and should provide anything
needed to manipulate a session, whatever its storing engine is.

=item B<id>

The session id will be written to a cookie, by default named C<dancer.session>, 
it is assumed that a client must accept cookies to be able to use a 
session-aware Dancer webapp. (The cookie name can be change using the
C<session_name> config setting.)

=item B<storage engine>

When the session engine is enabled, a I<before> filter takes care to initialize
the appropriate session engine (according to the setting C<session>).

Then, the filter looks for a cookie named C<dancer.session> (or whatever you've
set the C<session_name> setting to, if you've used it) in order to
I<retrieve> the current session object. If not found, a new session object is
I<created> and its id written to the cookie.

Whenever a session call is made within a route handler, the singleton
representing the current session object is modified.

After terminating the request, a I<flush> is made to the session object.

=back

=head1 DESCRIPTION

This virtual class describes how to build a session engine for Dancer. This is
done in order to allow multiple session storage backends with a common interface.

Any session engine must inherit from Dancer::Session::Abstract and implement
the following abstract methods.

=head2 Configuration

These settings control how a session acts.

=head3 session_name

The default session name is "dancer_session". This can be set in your config file:

    setting session_name: "mydancer_session"

=head3 session_domain

    Allows you to set the domain property on the cookie, which will
    override the default.  This is useful for setting the session cookie's
    domain to something like '.domain.com' so that the same cookie will
    be applicable and usable across subdomains of a base domain.

=head3 session_secure

The user's session id is stored in a cookie.  If true, this cookie
will be made "secure" meaning it will only be served over https.

=head3 session_expires

When the session should expire.  The format is either the number of
seconds in the future, or the human readable offset from
L<Dancer::Cookie/expires>.

By default, there is no expiration.

=head3 session_is_http_only

This setting defaults to 1 and instructs the session cookie to be
created with the C<HttpOnly> option active, meaning that JavaScript
will not be able to access to its value.

=head2 Abstract Methods

=over 4

=item B<retrieve($id)>

Look for a session with the given id, return the session object if found, undef
if not.

=item B<create()>

Create a new session, return the session object.

=item B<flush()>

Write the session object to the storage engine.

=item B<destroy()>

Remove the current session object from the storage engine.

=item B<session_name> (optional)

Returns a string with the name of cookie used for storing the session ID.

You should probably not override this; the user can control the cookie name
using the C<session_name> setting.

=back

=head2 Inherited Methods

The following methods are not supposed to be overloaded, they are generic and
should be OK for each session engine.

=over 4

=item B<build_id>

Build a new uniq id.

=item B<read_session_id>

Reads the C<dancer.session> cookie.

=item B<write_session_id>

Write the current session id to the C<dancer.session> cookie.

=back

=cut
