her.esy.fun/src/posts/0018-makefile-as-static-site-builder-follow-up/index.org

#+TITLE: Efficient Static Site Build with make
#+DESCRIPTION: A deeper view of my static site builder Makefile
#+KEYWORDS: blog static
#+AUTHOR: Yann Esposito
#+EMAIL: yann@esposito.host
#+DATE: [2021-05-09 Sun]
#+LANG: en
#+OPTIONS: auto-id:t
#+STARTUP: showeverything

This article will dig a bit deeper about how I generate my static website.
In a [[https://her.esy.fun/posts/0017-static-blog-builder/index.html][previous article]] I just gave the rationale and an overview to do it
yourself.

A few goal reached by my current build system are:

1. Source file format agnostic. You can use markdown, org-mode or even
   directly writing html.
2. Support gemini
3. Optimize size: minify HTML, CSS, images
4. Generate an index page listing the posts
5. Generate RSS/atom feed (for both gemini and http)

So make will just take care of handling the dependency graph to minimize
the amount of effort when a change occurs in the sources.
But for some features, I built specifics tools.
For example to be absolutely agnostic in the source format for my articles
I generate the RSS out of a tree of HTML files.
But taking advantage of Make, I generate an index cache to transform those
HTML into XML which will be faster to use to build different indexes.
To make those transformations I use very short a shell scripts.

* =Makefile= overview
:PROPERTIES:
:CUSTOM_ID: -makefile--overview
:END:

A Makefile is constitued of rules.
The first rule of your Makefile will be the default rule.
The first rule of my Makefile is called =all=.

A rule as the following format:

#+begin_src makefile
target: file1 file2
	cmd --input file1 file2 \
		--output target
#+end_src

if =target= does not exists, then =make= will look at its
dependencies.
If any of its dependency need to be updated, it will run all the rules in
the correct order to rebuild them, and finally run the script to build
=target=.
A file need to be updated if one of its dependency need to be updated or is
newer.

The ususal case of =make= is about building a single binary out of many
source files.
But for a static website, we need to generate a lot of files from a lot of
files.
So we construct the rules like this:

#+begin_src makefile
all: site

# build a list of files that will need to be build
DST_FILES := ....
# RULES TO GENERATE DST_FILES
ALL += $(DST_FILES)

# another list of files
DST_FILES_2 := ....
# RULES TO GENERATE DST_FILES_2
ALL += $(DST_FILES_2)

site: $(ALL)
#+end_src

In my =Makefile= I have many similar block with the same pattern.

1. I retrieve a list of source files
2. I construct the list of destination files (change the directory, the extension)
3. I declare a rule to construct these destination files
4. I add the destination files to the =ALL= variable.

I have a block for:
- raw assets I just want copied
- images I would like to compress for the web
- =html= I would like to generate from org mode files via pandoc
- =gmi= I would like to generate from org mode files
- =xml= files I use as cache to build different index files
- =index.html= file containing a list of my posts
- =rss.xml= file containing a list of my posts
- =gemini-atom.xml= file containing a list of my posts

** Assets
:PROPERTIES:
:CUSTOM_ID: assets
:END:

The rules to copy assets will be a good first example.

1. find all assets in =src/= directory
2. generate all assets from these file in =_site/= directory
3. make this rule a dependency on the =all= rule.


#+begin_src makefile
SRC_ASSETS := $(shell find src -type f)
DST_ASSETS := $(patsubst src/%,_site/%,$(SRC_ASSETS))
_site/% : src/%
	@mkdir -p "$(dir $@)"
	cp "$<" "$@"
.PHONY: assets
assets: $(DST_ASSETS)
ALL += assets
#+end_src

OK, this looks terrible.
But mainly:

- ~SRC_ASSETS~ will contains the result of the command ~find~.
- ~DST_ASSETS~ will contains the files of ~SRC_ASSETS~  but we replace the
 =src/= by =_site/=.
- We create a generic rule; for all files matching the following pattern
 =_site/%=, look for the file =src/%= and if it is newer (in our case)
  then execute the following commmands:
  - create the directory to put =_site/%= in
  - copy the file

About the line ~@mkdir -p "$(dir $@)"~:
- the =@= at the start of the command simply means that we make this execution silent.
- The =$@= is replaced by the target string.
- And =$(dir $@)= will generate the dirname of =$@=.

For the line with ~cp~ you just need to know that =$<= will represent the
first dependency.

So my Makefile is composed of similar blocks, where I replace the first
find command to match specific files and where I use different building rule.
An important point, is that the rule must be the most specific possible
because make will use the most specific rule in case of ambiguity.
So for example, the matching rule =_site/%: src/%= will match all files in
the =src/= dir.
But if we want to treat css file with another rule we could write:

#+begin_src makefile
_site/%.css: src/%.css
	minify "$<" "$@"
#+end_src

And if the selected file is a css file, this rule will be selected.

** Prelude
:PROPERTIES:
:CUSTOM_ID: prelude
:END:

So to start I have a few predefined useful variables.

#+begin_src makefile
all: site
# directory containing the source files
SRC_DIR ?= src
# directory that will contain the site files
DST_DIR ?= _site
# a directory that will contain a cache to speedup indexing
CACHE_DIR ?= .cache

# options to pass to find to prevent matching files in the src/drafts
# directory
NO_DRAFT := -not -path '$(SRC_DIR)/drafts/*'
# option to pass to find to not match  org files
NO_SRC_FILE := ! -name '*.org'
#+end_src

** CSS
:PROPERTIES:
:CUSTOM_ID: css
:END:

So here we go, the same simple pattern for CSS files.

#+begin_src makefile
# CSS
SRC_CSS_FILES := $(shell find $(SRC_DIR) -type f -name '*.css')
DST_CSS_FILES := $(patsubst $(SRC_DIR)/%,$(DST_DIR)/%,$(SRC_RAW_FILES))
$(DST_DIR)/%.css : $(SRC_DIR)/%.css
	@mkdir -p "$(dir $@)"
	minify "$<" > "$@"
.PHONY: css
css: $(DST_CSS_FILES)
ALL += css
#+end_src

This is very similar to the block for raw assets.
The difference is just that instead of using =cp= we use the =minify=
command.

** ORG → HTML
:PROPERTIES:
:CUSTOM_ID: org----html
:END:

Now this one is more complex but is still follow the same pattern.

#+begin_src makefile
# ORG -> HTML
EXT ?= .org
SRC_PANDOC_FILES ?= $(shell find $(SRC_DIR) -type f -name "*$(EXT)" $(NO_DRAFT))
DST_PANDOC_FILES ?= $(patsubst %$(EXT),%.html, \
                        $(patsubst $(SRC_DIR)/%,$(DST_DIR)/%, \
                            $(SRC_PANDOC_FILES)))
PANDOC_TEMPLATE ?= templates/post.html
MK_HTML := engine/mk-html.sh
PANDOC := $(MK_HTML) $(PANDOC_TEMPLATE)
$(DST_DIR)/%.html: $(SRC_DIR)/%.org $(PANDOC_TEMPLATE) $(MK_HTML)
	@mkdir -p "$(dir $@)"
	$(PANDOC) "$<" "$@.tmp"
	minify --mime text/html "$@.tmp" > "$@"
	@rm "$@.tmp"
.PHONY: html
html: $(DST_PANDOC_FILES)
ALL += html
#+end_src

So to construct =DST_PANDOC_FILES= this time we also need to change the
extension of the file from =org= to =html=.
We need to provide a template that will be passed to pandoc.

And of course, as if we change the template file we would like to
regenerate all HTML files we put the template as a dependency.
But importantly *not* at the first place. Because we use =$<= that will be
the first dependency.

I also have a short script instead of directly using =pandoc=.
It is easier to handle =toc= using the metadatas in the file.
And if someday I want to put the template in the metas, this will be the
right place to put that.

The =mk-html.sh= is quite straightforward:

#+begin_src bash
#!/usr/bin/env bash
set -eu

# put me at the top level of my project (like Makefile)
cd "$(git rev-parse --show-toplevel)" || exit 1
template="$1"
orgfile="$2"
htmlfile="$3"

# check if there is the #+OPTIONS: toc:t
tocoption=""
if grep -ie '^#+options:' "$orgfile" | grep 'toc:t'>/dev/null; then
    tocoption="--toc"
fi

set -x
pandoc $tocoption \
       --template="$template" \
       --mathml \
       --from org \
       --to html5 \
       --standalone \
       $orgfile \
       --output "$htmlfile"
#+end_src

Once generated I also minify the html file.
And, that's it.
But the important part is that now, if I change my script or the template
or the file, it will generate the dependencies.
** Indexes
:PROPERTIES:
:CUSTOM_ID: indexes
:END:

One of the goal I have is to be as agnostic as possible regarding format.
I know that the main destination format will be html.
So as much as possible, I would like to use this format.
So for every generated html file I will generate a clean XML file (via
hxclean) so I will be able to get specific node of my HTML files.
These XML files will constitute my "index".
Of course this is not the most optimized index (I could have used sqlite
for example) but it will already be quite helpful as the same index files
will be used to build the homepage with the list of articles, and the RSS
file.

#+begin_src makefile
# INDEXES
SRC_POSTS_DIR ?= $(SRC_DIR)/posts
DST_POSTS_DIR ?= $(DST_DIR)/posts
SRC_POSTS_FILES ?= $(shell find $(SRC_POSTS_DIR) -type f -name "*$(EXT)")
RSS_CACHE_DIR ?= $(CACHE_DIR)/rss
DST_XML_FILES ?= $(patsubst %.org,%.xml, \
                        $(patsubst $(SRC_POSTS_DIR)/%,$(RSS_CACHE_DIR)/%, \
                            $(SRC_POSTS_FILES)))
$(RSS_CACHE_DIR)/%.xml: $(DST_POSTS_DIR)/%.html
	@mkdir -p "$(dir $@)"
	hxclean "$<" > "$@"
.PHONY: indexcache
indexcache: $(DST_XML_FILES)
ALL += indexcache
#+end_src

So to resume this rule will generate for every file in =site/posts/*.html=
a corresponding =xml= file (=hxclean= takes an HTML an try its best to make
an XML out of it).
** HTML Index
:PROPERTIES:
:CUSTOM_ID: html-index
:END:

So now we just want to generate the main =index.html= page at the root of
the site.
This page should list all articles by date in reverse order.
To achieve this I wrote a short shell script but here is the corresponding
rule in the Makefile:

#+begin_src makefile
# HTML INDEX
HTML_INDEX := $(DST_DIR)/index.html
MKINDEX := engine/mk-index.sh
$(HTML_INDEX): $(DST_XML_FILES) $(MKINDEX) $(TEMPLATE)
	@mkdir -p $(DST_DIR)
	$(MKINDEX)
.PHONY: index
index: $(HTML_INDEX)
ALL += index
#+end_src

My =mk-index.sh= script takes advantage of the index files we constructed
before with =hxclean=.
Mainly I use =hxselect= to find the information I want to find, the
title, the date and the keywords.

#+begin_src bash
#!/usr/bin/env zsh

cd "$(git rev-parse --show-toplevel)" || exit 1
# Directory
webdir="_site"
postsdir="$webdir/posts"
indexfile="$webdir/index.html"
indexdir=".cache/rss"

# maximal number of articles to put in the index homepage
maxarticles=1000

# HTML Accessors (similar to CSS accessors)
dateaccessor='.yyydate'
# title and keyword shouldn't be changed
titleaccessor='title'
keywordsaccessor='meta[name=keywords]::attr(content)'

formatdate() {
    # format the date for RSS
    local d="$1"
    # echo "DEBUG DATE: $d" >&2
    LC_TIME=en_US date --date $d +'%a, %d %b %Y %H:%M:%S %z'
}
finddate(){ < $1 hxselect -c $dateaccessor | sed 's/\[//g;s/\]//g;s/ .*$//' }
findtitle(){ < $1 hxselect -c $titleaccessor }
findkeywords(){ < $1 hxselect -c $keywordsaccessor | sed 's/,/ /g' }
mktaglist(){
    for keyword in $*; do
        printf "\\n<span class=\"tag\">%s</span>" $keyword
    done
}

autoload -U colors && colors
tmpdir=$(mktemp -d)
typeset -a dates
dates=( )
for xfic in $indexdir/**/*.xml; do
    postfile="$(echo "$xfic"|sed 's#^'$postsdir'/##')"
    blogfile="$(echo "$xfic"|sed 's#.xml$#.html#;s#^'$indexdir'/#posts/#')"
    printf "%-30s" $postfile
    d=$(finddate $xfic)
    echo -n " [$d]"
    rssdate=$(formatdate $d)
    title=$(findtitle $xfic)
    keywords=( $(findkeywords $xfic) )
    printf ": %-55s" "$title ($keywords)"
    taglist=$(mktaglist $keywords)
    { printf "\\n<li>"
      printf "\\n<a href=\"%s\">%s</a>" "${blogfile}" "$title"
      printf "\\n<span class=\"pubDate\">%s</span>%s" "$d"
      printf "<span class=\"tags\">%s</span>" "$taglist"
      printf "\\n</li>\\n\\n"
    } >>  "$tmpdir/${d}-$(basename $xfic).index"
    dates=( $d $dates )
    echo " [${fg[green]}OK${reset_color}]"
done

echo "Publishing"

# building the body

cat templates/index-preamble.html  >> $tmpdir/index

previousyear=""
for fic in $(ls $tmpdir/*.index | sort -r | head -n $maxarticles ); do
    echo "${fic:t}"
    year=$( echo "${fic:t}" | perl -pe 's#(\d{4})-.*#$1#')
    if (( year != previousyear )); then
        echo $year
        if (( previousyear > 0 )); then
            echo "</ul>" >> $tmpdir/index
        fi
        previousyear=$year
        echo "<h3 name=\"${year}\" >${year}</h3><ul>" >> $tmpdir/index
    fi
    cat $fic >> $tmpdir/index
done
cat templates/index-postamble.html  >> $tmpdir/index

title="Yann Esposito's Posts"
description="The index of my most recent articles."
author="Yann Esposito"
body=$(< $tmpdir/index)
date=$(LC_TIME=en_US date +'%Y-%m-%d')

# A neat trick to use pandoc template within a shell script
# the pandoc templates use $x$ format, we replace it by just $x
# to be used with envsubst
template=$(< templates/post.html | \
    sed 's/\$\(header-includes\|table-of-content\)\$//' | \
    sed 's/\$if.*\$//' | \
    perl -pe 's#(\$[^\$]*)\$#$1#g' )
{
    export title
    export author
    export description
    export date
    export body
    echo ${template} | envsubst
} > "$indexfile"

rm -rf $tmpdir
echo "* HTML INDEX [done]"
#+end_src