NAME
    Data::ICal::RDF - Turn iCal files into an RDF graph

VERSION
    Version 0.01

SYNOPSIS
        use Data::ICal::RDF;

        # Instantiate a processing context with the appropriate handlers:
        my $context = Data::ICal::RDF->new(
            resolve_uid    => sub {
                # returns an RDF node for the UID...
            },
            resolve_binary => sub {
                # stores a binary object and resolves any relations
                # between it and its supplied file name; returns either an
                # identifier for the content or an identifier for the
                # relation between the name and the content.
            },
        );

        # Process a Data::ICal object...
        $context->process($ical);

        # Successive calls to 'process' against different iCal objects
        # will accumulate statements in the context's internal model.

        # Now you can do whatever you like with the model.
        my $result = $context->model;

METHODS
  new
    resolve_uid
        Supply a callback function to resolve the "UID" property of an iCal
        object. This function *must* return a RDF::Trine::Node::Resource or
        RDF::Trine::Node::Blank. The function is handed:

        1.  The context object itself, meaning the function should be
            written as if it were a mixin of Data::ICal::RDF,

        2.  The "UID" of the iCal entry as a string literal.

        This function is used in "subject_for", which is used by
        "process_events", which is used by "process". If the function is not
        reliable for any reason, such as a failure to access hardware or
        network resources, those methods may "croak".

        Here is an example of a method in a fictitious class which generates
        a closure suitable to pass into the Data::ICal::RDF constructor:

            sub generate_resolve_uid {
                my $self = shift;
                return sub {
                    my ($data_ical_rdf, $uid) = @_;

                    # magically look up a resource node from some other
                    # data source
                    return $self->lookup_uid($uid);
                };
            }

        This parameter is *required*.

    resolve_binary
        Supply a callback function to handle inline "BINARY" attachments.
        This function *must* return a RDF::Trine::Node::Resource or
        RDF::Trine::Node::Blank. The function is handed:

        1.  The context object itself, meaning the function should be
            written as if it were a mixin of Data::ICal::RDF,

        2.  The binary data as a seekable IO object,

        3.  The *declared* Content-Type of the data (as in you might want to
            verify it using something like File::MMagic or
            File::MimeInfo::Magic),

        4.  The suggested file name, which will already be stripped of any
            erroneous path information. File names of zero length or
            containing only whitespace will not be passed into this
            function, so you need only check if it is "defined".

        This function is used in the "BINARY" type handler in
        "process_events", which is used by "process". Once again, if this
        function is not completely reliable, those methods may "croak".

        Here is an example of a method in a fictitious class which generates
        a closure suitable to pass into the Data::ICal::RDF constructor:

            sub generate_resolve_binary {
                my $self = shift;
                return sub {
                    my ($data_ical_rdf, $io, $type, $name) = @_;

                    # store the content somewhere and get back an identifier
                    my $content_id = $self->store($io, $type);

                    # return the content ID if there is no file name
                    return $content_id unless defined $name;

                    # turn the name into an RDF literal
                    $name = RDF::Trine::Node::Literal->new($name);

                    # now retrieve the subject node that binds the filename
                    # to the content identifier
                    my $subj = $self->get_subject_for($content_id, $name);

                    # now perhaps write the relevant statements back into
                    # the parser context's internal model
                    map { $data_ical_rdf->model->add_statement($_) }
                        for $self->statements_for($content_id, $name);

                    # now we want to return the retrieved *subject*, which
                    # will be passed into the upstream RDF statement
                    # generation function.
                    return $subj;
                };
            }

        This parameter is *required*.

    model
        Supply an RDF::Trine::Model object to use instead of an internal
        temporary model, for direct interface to some other RDF data store.
        Note that this is also accessible through the "model" accessor.

        This parameter is *optional*.

    tz  Supply a "HASH" reference whose keys are *known* iCal "TZID"
        identifiers, and the values are DateTime::TimeZone objects. By
        default, these values are gleaned from the supplied Data::ICal
        objects themselves and *will override* any supplied values.

        This parameter is *optional*.

  process $ICAL
    Process a Data::ICal object and put it into the object's internal model.
    Note that any "VTIMEZONE" objects found will *not* be inserted into the
    model, but rather integrated into the appropriate date/time-like
    property values.

    Note as well that *all* non-standard properties are *ignored*, as well
    as all non-standard property *parameters* with the exception of
    "X-FILENAME" and "X-APPLE-FILENAME" since there is no standard way to
    suggest a file name for attachments.

    This method calls "subject_for" and therefore may croak if the
    "resolve_uid" callback fails for any reason.

  process_events @EVENTS
    Process a list of Data::ICal::Entry::Event objects. This is called by
    "process" and therefore also may croak.

  subject_for $UID
    Take an iCal "UID" property and return a suitable RDF node which can be
    used as a subject. This may call the "resolve_uid" callback and
    therefore may croak if it receives a bad value.

  model
    Retrieve the RDF::Trine::Model object embedded in the processor.

CAVEATS
    A number of iCal datatype handlers are not implemented in this early
    version. These are:

    *   "CAL-ADDRESS"

    *   "DURATION"

    *   "PERIOD"

    *   "RECUR"

    *   "TIME"

    *   "UTC-OFFSET"

    As well, the "GEO", "RESOURCES", and "CLASS" properties are yet to be
    implemented. Patches are welcome, as are work orders.

AUTHOR
    Dorian Taylor, "<dorian at cpan.org>"

BUGS
    Please report any bugs or feature requests to "bug-data-ical-rdf at
    rt.cpan.org", or through the web interface at
    <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Data-ICal-RDF>. I will
    be notified, and then you'll automatically be notified of progress on
    your bug as I make changes.

SUPPORT
    You can find documentation for this module with the perldoc command.

        perldoc Data::ICal::RDF

    You can also look for information at:

    *   RT: CPAN's request tracker (report bugs here)

        <http://rt.cpan.org/NoAuth/Bugs.html?Dist=Data-ICal-RDF>

    *   AnnoCPAN: Annotated CPAN documentation

        <http://annocpan.org/dist/Data-ICal-RDF>

    *   CPAN Ratings

        <http://cpanratings.perl.org/d/Data-ICal-RDF>

    *   Search CPAN

        <http://search.cpan.org/dist/Data-ICal-RDF/>

SEE ALSO
    *   Data::ICal

    *   RDF::Trine

    *   DateTime::TimeZone::ICal

    *   RFC 5545 <http://tools.ietf.org/html/rfc5545>

LICENSE AND COPYRIGHT
    Copyright 2015 Dorian Taylor.

    Licensed under the Apache License, Version 2.0 (the "License"); you may
    not use this file except in compliance with the License. You may obtain
    a copy of the License at <http://www.apache.org/licenses/LICENSE-2.0>.

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.

