App::DocKnot::Spin::RSS(3pm)

NAME
App::DocKnot::Spin::RSS - Generate RSS and thread from a feed description file

SYNOPSIS
    use App::DocKnot::Spin::RSS;

    my $rss = App::DocKnot::Spin::RSS->new({ base => 'path/to/tree' });
    $rss->generate('path/to/tree/.rss');

REQUIREMENTS
Perl 5.24 or later and the modules Date::Language, Date::Parse (both part of the TimeDate distribution), List::SomeUtils, Path::Tiny, and Perl6::Slurp, both of which are available from CPAN.

DESCRIPTION
App::DocKnot::Spin::RSS reads as input a feed description file consisting of simple key/value pairs and writes out either thread (for input to App::DocKnot::Spin::Thread) or RSS. The feed description consists of a leading block of metadata and then one block per entry in the feed. Each block can either include the content of the entry or can reference an external thread file, in several formats, for the content. The feed description file defines one or more output files in the Output field of the metadata.

Output files are only regenerated if they are older than the input feed description file.

App::DocKnot::Spin::RSS is designed for use with App::DocKnot::Spin. It relies on App::DocKnot::Spin::Thread to convert thread to HTML, both for inclusion in RSS feeds and for post-processing of generated thread files. App::DocKnot::Spin::RSS is invoked automatically by App::DocKnot::Spin when it encounters an .rss file in a directory it is processing.

See "INPUT LANGUAGE" for the details of the language in which .rss files are written.

CLASS METHODS

new(ARGS)
    Create a new App::DocKnot::Spin::RSS object. ARGS should be a hash reference with one or more of the following keys, all of which are optional:

    base
        By default, App::DocKnot::Spin::RSS output files are relative to the current working directory. If the "base" argument is given, output files will be relative to the value of "base" instead. Output files specified as absolute paths will not be affected. "base" may be a string or a Path::Tiny object.

INSTANCE METHODS

generate(FILE[, BASE])
    Parse the input file FILE and generate the output files that it specifies. BASE, if given, specifies the root directory for output files specified with relative paths, and overrides any "base" argument given to new(). Both FILE and BASE may be strings or Path::Tiny objects.

INPUT LANGUAGE
The input for App::DocKnot::Spin::RSS is normally a .rss file in a tree being processed by App::DocKnot::Spin. The file consists of one or more blocks of RFC-2822-style fields with values, each separated by a blank line. Each field and value looks like an e-mail header field, including possible continuation lines:

    Field: value
     continuation of value

Any line beginning with whitespace is considered a continuation of the previous line. If a value should contain a blank line, indicate that blank line with a continuation line containing only a period. For example:

    Field: first paragraph
     .
     second paragraph

  Metadata
The first block of the file sets the metadata for this set of output. The following fields are supported:

Base
    The base URL for entries in this file. All links in subsequent blocks of the file, if not absolute URLs, are treated as relative to this URL and are made absolute by prepending this URL. Always specify this key unless all Link fields in the remainder of the file use absolute URLs.

    This field value is also used as the "<link>" element in the RSS feed, indicating the web site corresponding to this feed.

Description
    The description of the feed, used only in the RSS output. This should always be set if there are any RSS output files.

Index-Base
    The base URL for output files of type "index". This is used to canonicalize relative URLs and should be the URL to the directory containing the HTML file that will result from processing the thread output. This should be set if there are any output files of type "index"; if it isn't set, relative links may be rewritten incorrectly.

Index-Prefix
    When generating output files of type "index", use the value as the initial content of the generated thread. This field should almost always be set if any output files of type "index" are defined. It will contain such things as the "\heading" command, any prologue material, initial headings, and so forth.

Index-Suffix
    When generating output files of type "index", append the value to the end of the generated thread. The "\signature" command is always appended and should not be included here. Set this field only if there is other thread that needs to be appended (such as closing brackets for "\div" commands).

Language
    The language of the feed, used only in the RSS output. This should always be set if there are any RSS output files. Use "en-us" for US English.

Output
    Specifies the output files for this input file in the form of a whitespace-separated list of output specifiers. This field must always be set.

    An output specifier is of the form tags:type:file, where file is the output file (always a relative path), type is the type of output, and tags indicates which entries to include in this file. tags is a comma-separated list of tags or the special value "*", indicating all tags.

    There are three types of output:

    index
        Output thread containing all recent entries. This output file honors the Recent field similar to RSS output and is used to generate something akin to a journal or blog front page: an HTML version of all recent entries. It only supports external entries (entries with "Journal" or "Review" fields). The "Index-Base" and "Index-Prefix" (and possibly "Index-Suffix") fields should be set.

        For output for entries with simple descriptions included in the input file, see the "thread" output type.

    rss Output an RSS file. App::DocKnot::Spin::RSS only understands the RSS 2.0 output format. The "Description", "Language", "RSS-Base", and "Title" fields should be set to provide additional metadata for the output file.

    thread
        Output thread containing all entries in this input file. This should only be used for input files where all entries have their description text inline in the input file. Every entry will be included. The output will be divided into sections by month, and each entry will be in a description list, with the title prefixed by the date. The "Thread-Prefix" field should be set.

        For output that can handle entries from external files, see the "index" output type.

Recent
    Sets the number of recent entries to include in output files of type "rss" or "index" (but not "thread", which will include the full contents of the file). If this field is not present, the default is 15.

RSS-Base
    The base URL for RSS files generated by this file. Each generated RSS file should have a link back to itself, and that link will be formed by taking the output name and prepending this field.

Thread-Prefix
    When generating thread output from this file, use the value as the initial content of the generated thread. This field should almost always be set if any output files of type "thread" are defined. It will contain such things as the "\heading" command, any prologue material, initial headings, and so forth.

Title
    The title of the feed, used only in the RSS output. This should always be set if there are any RSS output files.

  Entries
After the first block, each subsequent block in the input file defines an entry. Entries take the following fields:

Date
    The date of this entry in ISO date format (YYYY-MM-DD HH:MM). This field is required.

Description
    The inline contents of this entry. One and only one of this field, "Journal", or "Review" should be present. "Description" fields can only be used with output types of "rss" or "thread".

Journal
    Specifies that the content of this entry should be read from an external thread file given by the value of this field. The contents of that file are expected to be in the thread format used by my journal entries: specifically, everything is ignored up to the first "\h1" and after the "\date" macro, and the "\date" line is stripped off (the date information from the "Date" field is used instead).

    One and only one of this field, "Description", or "Review" should be present.

Link
    The link to the page referenced by this entry. The link is relative to the "Base" field set in the input file metadata. This field is required.

Review
    Specifies that the content of this entry should be read from an external thread file given by the value of this field. The contents of that file are expected to be in the thread format used by my book reviews.

    Many transformations are applied to entries of this sort based on the format used by my book reviews and the URL layout they use, none of which is documented at present. For the time being, see the source code for what transformations are done. This support will require modification for use by anyone else.

    One and only one of this field, "Description", or "Review" should be present.

Tags
    Whitespace-separated tags for this entry, used to determine whether this entry will be included in a given output file given its output specification. In addition to any tags listed here, any entry with a "Review" field will automatically have the "review" tag.

    Entries may have no tags, in which case they're only included in output files with a tag specification of "*".

Title
    The title of the entry. This field is required.

NOTES
RSS 2.0 was chosen as the output format because it supports GUIDs for entries separate from the entry URLs and hence supports multiple entries for the same URL, something that I needed for an RSS feed of recent changes to my entire site.

AUTHOR
Russ Allbery <rra@cpan.org>

COPYRIGHT AND LICENSE
Copyright 2008, 2010-2012, 2021-2022 Russ Allbery <rra@cpan.org>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

SEE ALSO
docknot(1), App::DocKnot::Spin, App::DocKnot::Spin::Thread

This module is part of the App-DocKnot distribution. The current version of DocKnot is available from CPAN, or directly from its web site at <https://www.eyrie.org/~eagle/software/docknot/>.