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@c %**start of header
@setfilename haunt.info
@documentencoding UTF-8
@settitle Haunt Reference Manual
@c %**end of header

@include version.texi

@copying
Copyright @copyright{} 2015 David Thompson@*

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.  A
copy of the license is included in the section entitled ``GNU Free
Documentation License''.
@end copying

@dircategory Web development
@direntry
* Haunt: (haunt).       Haunt, the functional static site generator.
@end direntry

@titlepage
@title Haunt Reference Manual
@subtitle Using Haunt
@author The Haunt Developers

@page
@vskip 0pt plus 1filll
Edition @value{EDITION} @*
@value{UPDATED} @*

@insertcopying
@end titlepage

@contents

@node Top
@top Haunt

This document describes Haunt version @value{VERSION}, an extensible,
functional static site generator.

@menu
* Introduction::                About Haunt.
* Installation::                Installing Haunt.
* Tutorial::                    How to get started quickly.
* Command-line Interface::      Using Haunt from the command-line.
* Programming Interface::       Using the Haunt API in Scheme.
* Contributing::                How to contribute to Haunt.

* GNU Free Documentation License::  The license of this manual.
* Concept Index::               Concepts.
* Programming Index::           Data types, procedures, syntax, and variables.

@detailmenu
 --- The Detailed Node Listing ---

Installation

* Downloading::                 Downloading the source code.
* Requirements::                Software needed to build and run Haunt.
* Building::                    Building from source code.

@end detailmenu
@end menu

@node Introduction
@chapter Introduction

Haunt is a hackable static site generator written in Guile Scheme.  A
static site generator assists an author with generating the HTML pages
that they publish on the web.  Unlike ``content management systems''
such as Wordpress or Drupal, static site generators are not dynamic
web applications (complete with a relational database) that build
pages on-the-fly.  Instead, web pages are built in advance, on the
author's computer, and copied to a web server when it is time to
publish changes.  The consequence of this design is that the web
server no longer needs to run a complex, potentially insecure web
application that connects to a database to retrieve data.  Static
files can be served easily by any generic web server.  Since there is
no web application or database server to deal with, static websites
are easier to maintain, more secure, and resistant to high web traffic
(``slashdotting.'')  Furthermore, the entire website is stored in
plain text, which allows the files to be version-controlled rather
than kept in a relational database with no concept of history that
needs to be backed up regularly.

At the time that Haunt was conceived, there existed literally hundreds
of other static site generators.  Why add another one?  Haunt
differentiates itself from most other static site generators in that
it aspires to the Emacs philosophy of ``practical software freedom.''
Not only is the source code available under a Free Software license,
as most static site generators are, it is designed to be easily hacked
and extended without altering the core source code.  Haunt
purposefully blurs the line between document and program, author and
programmer, by embracing the notion of data as code.  A Haunt-based
website is not simply data, but a computer program.  This design
strategy encourages authors to automate repetitive tasks and empowers
them to extend the software with their own ideas.

To make such a system work well, a general-purpose, extensible
programming language is needed.  A traditional configuration file
format simply will not do.  The programming language that we feel is
best suited to this task is Scheme, a clean and elegant dialect of
Lisp.  We believe that by giving authors the full expressive power of
Scheme, they will be able to produce better websites and make better
use of their time than with less programmable systems and less capable
programming languages.  Authors should feel empowered to hack the
system to make it do what they want rather than what some programmer
decided they should want.  And perhaps most importantly, building
websites with Haunt should be @emph{fun}.

Websites written in Haunt are described as purely functional programs
that accept ``posts'', text documents containing arbitrary metadata,
as input and transform them into complete HTML pages using Scheme
procedures.  Haunt has no opinion about what markup language authors
should use to write their posts and will happily work with any format
for which a ``reader'' procedure exists.  Likewise, Haunt also has no
opinion about how authors should structure their sites, but has sane
defaults.  Currently, there exist helpful ``builder'' procedures that
do common tasks such as generating a blog or Atom feed.  While the
built-in features may be enough for some, they surely will not be
enough for all.  Haunt's Scheme API empowers authors to easily tweak
existing components, write replacements, or add entirely new features
that do things no else has thought to do yet.

Happy haunting!

@node Installation
@chapter Installation

@menu
* Downloading::                 Downloading the source code.
* Requirements::                Software needed to build and run Haunt.
* Building::                    Building from source code.
@end menu

@node Downloading
@section Downloading

Official Haunt source code release tarballs can be found on the
@url{http://haunt.dthompson.us/downloads.html, downloads page} of
Haunt's website, along with their associated checksums.

@node Requirements
@section Requirements

Haunt depends on the following packages:

@itemize
@item
@url{https://gnu.org/software/guile, GNU Guile} version 2.0.11 or
later
@end itemize

The following dependencies are optional:

@itemize
@item
@url{http://www.nongnu.org/guile-reader/, Guile-Reader} version 0.6 or
later (for Skribe support)
@end itemize

@node Building
@section Building

Haunt uses the standard GNU build system, so the basic installation
procedure looks like this:

@example
./configure
make
make install
@end example

@node Tutorial
@chapter Tutorial

The goal of this tutorial is to quickly create a barebones blog with
Haunt in order to demonstrate the basic workflow and key concepts.

First, create a directory for the new site:

@example
mkdir haunt-tutorial
cd haunt-tutorial
@end example

Next, create the site configuration file @file{haunt.scm}.  This is
where all of the code for building the website will go.

Here's what a simple Haunt configuration looks like:

@example
(use-modules (haunt asset)
             (haunt site)
             (haunt builder blog)
             (haunt builder atom)
             (haunt reader skribe))

(site #:title "My First Haunt Site"
      #:domain "example.com"
      #:default-metadata
      '((author . "Eva Luator")
        (email  . "eva@@example.com"))
      #:readers (list skribe-reader)
      #:builders (list (blog)
                       (atom-feed)
                       (atom-feeds-by-tag)))
@end example

Haunt represents the full configuration of the website using the
@code{site} procedure.  Site objects specify things like the site
title, the default metadata to use for posts, which markup formats are
supported, and which builders are used to generate web pages.

With the above code saved into the @file{haunt.scm} file, the next
step is to create a @file{posts} directory and populate it with
articles to publish.  Put the text below into a file named
@file{posts/hello.skr}:

@example
(post
 :title "Hello, World!"
 :date (make-date* 2015 10 15)
 :tags '("hello")

 (h1 [Hello, World!])

 (p [This is my very first Skribe document!]))
@end example

This is a
@url{http://www.nongnu.org/skribilo/doc/user-3.html#skribe-syntax,
Skribe} document.  Skribe is one of the built-in languages that Haunt
knows how to work with.  It's basically Scheme, but with support for
writing literal text without quoting it all by enclosing it in square
brackets.  The code above defines a post named ``Hello, World!'' with
a publishing date of 2015-10-15, whose contents are just a single
heading and a paragraph.

To build the site, run @command{haunt build} to compile all of the
HTML pages.  To view the results, run @command{haunt serve} and visit
@url{http://localhost:8080} in a web browser.  @command{haunt serve}
is a handy utility that serves the contents of the website using
Guile's built-in HTTP server.  Since the blog builder was specified in
@file{haunt.scm}, the default index page is a simple listing of all
posts, which for now is a single post.  Clicking on the post title
will display a page with only that post's contents.

In addition to the basic blog builder, the @file{haunt.scm} file
specifies two additional builders for Atom feeds.  The
@code{atom-feed} builder creates a feed of all posts located at
@url{http://localhost:8080/feed.xml}.  The @code{atom-feeds-by-tag}
builder creates one feed for each unique tag specified in the post
metadata.  There's only one tag right now, ``hello'', and its feed is
located at @url{http://localhost/feeds/tags/hello.xml}.

Tweaking a post, rebuilding the site, and viewing the results in a web
browser is the typical Haunt workflow.  However, having to run
@command{haunt build} every after each edit is tedious.  To address
this, run @command{haunt serve --watch}.  The Haunt web server, in
addition to serving web pages, will now watch for changes to important
files and automatically rebuild the site when they are edited.  This
streamlines the workflow into an edit, save, view loop.

Now that we've introduced the basic utilities and concepts, continue
reading this manual to learn more about Haunt's command-line and
programming interfaces.

@node Command-line Interface
@chapter Command-line Interface

@menu
* Invoking haunt build::        Build the website.
* Invoking haunt serve::        Serve the website over HTTP.
@end menu

The Haunt command-line interface is composed of many subcommands.  The
general syntax for all Haunt commands is:

@example
haunt @var{subcommand} @var{options}@dots{}
@end example

@node Invoking haunt build
@section Invoking @command{haunt build}

The @command{haunt build} command realizes a Haunt site configuration
file by compiling web pages and copying static assets to the output
directory.  For details on how to configure a Haunt site,
@pxref{Sites}.

Example:

@example
haunt build --config=haunt.scm
@end example

@table @code

@item --config=@var{configuration-file}
@itemx -c @var{configuration-file}
Load the Haunt site declaration from @var{configuration-file}.

@end table

@node Invoking haunt serve
@section Invoking @command{haunt serve}

The @command{haunt serve} command allows one to quickly view a local
preview of the generated website before publishing the finished
product to a remote web server.  When @command{haunt serve} runs, a
local HTTP server is spawned.  Visit the server using a web browser to
inspect the results of the build.  By default, the web server listens
on port 8080, so the URL to visit would be
@url{http://localhost:8080}.

While developing, it is common to rebuild the site frequently to view
the results of incremental changes.  Rather than manually running
@command{haunt build} (@ref{Invoking haunt build}) each time changes
are made, the @code{--watch} flag can be used to automatically rebuild
the site when a source file changes on disk.

@table @code

@item --config=@var{configuration-file}
@itemx -c @var{configuration-file}
Load the Haunt site declaration from @var{configuration-file}.

@item --port=@var{port}
@itemx -p @var{port}

Listen for HTTP requests on @var{port}.

@item --watch
@itemx -w

Automatically rebuild the site when source files change.

@end table

@node Programming Interface
@chapter Programming Interface

@menu
* Sites::                       Description of the site and how to build it.
* Posts::                       Articles, prose, blog posts, etc.
* Readers::                     Post interpreters.
* Pages::                       HTML/XML pages.
* Assets::                      Images, stylesheets, etc.
@end menu

Haunt is a fully-programmable system composed of several Guile Scheme
modules.  This section documents the public API.

@node Sites
@section Sites

@node Posts
@section Posts

@node Readers
@section Readers

@node Pages
@section Pages

@node Assets
@section Assets

@node Contributing
@chapter Contributing

@c *********************************************************************
@node GNU Free Documentation License
@appendix GNU Free Documentation License

@include fdl-1.3.texi

@c *********************************************************************
@node Concept Index
@unnumbered Concept Index
@printindex cp

@node Programming Index
@unnumbered Programming Index
@syncodeindex tp fn
@syncodeindex vr fn
@printindex fn

@bye

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