pbb

#!/usr/bin/env bash

shopt -s extglob nullglob

# Globals
declare -r \
	conf='.pbbconfig' \
	calicon='assets/calendar.svg' \
	cssfile='assets/pbb.css' \
	favicon='includes/favicon.html' \
	headerlinks='includes/headerlinks.html' \
	feedpath='docs/feed.xml' \
	goatcounter='includes/goatcounter.html' \
	header='includes/header.html' \
	metadata='.metadata.yml'

declare -rA features=(
	['math']=1
	['bibliography']=1
)

# Print warning message and continue
warn() {
	printf '%s\n' "$*" >&2
}

# Print error message and exit
die() {
	warn "$*"
	exit 1
}

# Print usage hint
usage() {
	cat <<- EOF >&2
		usage:
		pbb help | init TITLE | set PROPERTY VALUE | build | serve | deploy
		pbb enable FEATURE | disable FEATURE

		   help     Display this message
		   init     Initialize new blog in empty Git repository
		   set      Set configuration property to value; valid properties are
		            title        New blog title
		            gccode       GoatCounter code to enable analytics 
		            baseurl      Base URL for use in Atom feed
		            authorname   Author name for Atom feed
		            authoremail  Author email for Atom feed
		   build    Generate HTML files and store them in docs directory
		   serve    Serve blog on localhost:8000
		   deploy   Commit changes in docs directory and push to remote
		   enable   Turn on feature
		   disable  Turn off feature
	EOF
}

# Get the language setting from the environment
getlang() {
	local lang=${LANGUAGE:-${LC_ALL:-${LC_MESSAGES:-$LANG}}}

	# Shorten and replace underscore with hyphen to get IETF tag
	lang=${lang%%[.:@]*}
	lang=${lang/_/-}

	if [[ -z $lang ]] || [[ $lang == @(C|POSIX) ]]; then
		lang='en-US'
	fi

	printf '%s' "$lang"
}

# Check if the current directory is the root directory of a git repository
checkgit() {
	local topdir
	if ! topdir=$(git rev-parse --show-toplevel 2> /dev/null); then
		warn "not in a git repo"
		echo 'run "git init" first'
		return 1
	fi

	if [[ $PWD != "$topdir" ]]; then
		warn "in git repo, but not in root directory"
		echo "run \"pbb init\" from the repository root, $topdir"
		return 1
	fi

	return 0
}

# Initialize new blog
init() {
	local blogtitle=$1
	local msg

	if ! msg=$(checkgit); then
		die "$msg"
	fi

	if [[ -e $conf ]]; then
		die "conf file exists already, aborting"
	fi

	mkdir --parents assets images includes

	# Store title to config file
	setblogtitle "$blogtitle"
	git add "$conf"

	# Symlink assets
	ln --symbolic "${XDG_DATA_HOME:-$HOME/.local/share}/pbb/pbb.css" "$cssfile"
	ln --symbolic "${XDG_DATA_HOME:-$HOME/.local/share}/pbb/calendar.svg" "$calicon"
	git add "$cssfile" "$calicon"

	# Header links for Google Font style sheet
	printf '%s\n%s%s%s\n' \
		'<link href="https://fonts.gstatic.com" rel="preconnect" crossorigin>' \
		'<link href="https://fonts.googleapis.com/css?family=' \
		'Source+Code+Pro:400,400i,700,700i|Source+Sans+Pro:400,400i,700,700i' \
		'&display=swap" rel="stylesheet">' \
		> "$headerlinks"

	# Atom feed link
	printf '%s %s\n' \
		'<link href="/feed.xml" type="application/atom+xml" rel="alternate"' \
		"title=\"$blogtitle Feed\">" >> "$headerlinks"

	# Favicon for header
	printf '%s\n' \
		'<link rel="icon" href="/favicon.png" sizes="32x32" type="image/png">' \
		> "$favicon"

	# Template for GoatCounter snippet
	printf '%s\n' \
		'<script data-goatcounter="https://{{code}}.goatcounter.com/count"' \
		'        async src="//gc.zgo.at/count.js"></script>' \
		> "$goatcounter"

	git add includes

	# Metadata file
	printf '%s\n' \
		'toc: false' \
		'toc-title: Table of contents' \
		> "$metadata"
	git add "$metadata"

	# Publishing source
	mkdir docs
	touch docs/.nojekyll
	git add docs

	git commit -m "Initialize blog with pbb"

	# Example post
	cat <<- EOF > "$(printf '%(%F)T' -1)-my-first-post.md"
		---
		summary: >-
		  A wild post appeared
		---

		# My first post

		Hello world!
	EOF
}

# Set a new blog title
setblogtitle() {
	local blogtitle=$1
	setconfvalue 'blogtitle' "$blogtitle"
	printf '<div id="blogtitle"><a href="./">%s</a></div>\n' \
		"$blogtitle" > "$header"
}

# Extract the title from a markdown file
extracttitle() {
	local file=$1
	sed -n '/^# /{s///p;q}' "$file"
}

# Convert a markdown file to HTML and store it in the docs directory
md2html() {
	local file=$1
	[[ $file == *.md ]] || die "not a markdown file: $file"

	echo "Building $file..." >&2

	local args=(
		"--css=/pbb.css"
		"--email-obfuscation=references"
		"--from=markdown+emoji"
		"--highlight-style=${XDG_DATA_HOME:-$HOME/.local/share}/pandoc/solarizeddark.theme"
		"--include-before-body=$header"
		"--include-in-header=$headerlinks"
		"--lua-filter=dotgraph.lua"
		"--metadata=document-css:true"
		"--metadata=lang:$(getlang)"
		"--metadata-file=.metadata.yml"
		"--output=docs/${file/%.md/.html}"
		"--shift-heading-level-by=-1"
		"--standalone"
		"--table-of-contents=true"
		"--to=html"
		"--toc-depth=4"
	)

	if [[ $(getconfvalue 'bibliography') == 'on' ]]; then
		args+=("--citeproc")
	fi

	if [[ -n $(getconfvalue 'goatcountercode') ]]; then
		args+=("--include-after-body=$goatcounter")
	fi

	if [[ -f docs/favicon.png ]]; then
		args+=("--include-in-header=$favicon")
	fi

	if [[ $(getconfvalue 'math') == 'on' ]]; then
		args+=("--mathjax")
	fi

	if [[ $file == ????-??-??-* ]]; then
		args+=("--metadata=date:${file:0:10}")
	fi

	if [[ $file == 'index.md' ]]; then
		args+=("--metadata=pagetitle:$(getconfvalue 'blogtitle')")
	fi

	pandoc "${args[@]}" "$file" || die "error while converting $file"
}

# Empty docs and copy images directory
clean() {
	rm --recursive --force docs/!(CNAME|.nojekyll)
	mkdir docs/diagrams
	cp --recursive images docs
}

# Get value from config file
getconfvalue() {
	local key=$1
	(
		# shellcheck source=/dev/null
		source "$conf"
		printf '%s' "${!key}"
	)
}

# Set value in config file
setconfvalue() {
	local key=$1
	local value=$2
	if [[ -f $conf ]]; then
		sed -i "/$key=/d" "$conf"
	fi
	printf '%s=%q\n' "$key" "$value" >> "$conf"
}

# Set the GoatCounter code
setgccode() {
	local code=$1
	setconfvalue 'goatcountercode' "$code"
	sed -E -i "s|(https://).*(\.goatcounter)|\1$code\2|" "$goatcounter"
}

# Toggle feature
setfeature() {
	local feature=$1
	local value=$2
	if [[ ! -v features["$feature"] ]]; then
		die "invalid feature: $feature"
	fi
	setconfvalue "$feature" "$value"
}

# Convert favicon image file to 32x32 PNG
favicon() {
	local infile=(assets/favicon.*)
	if ((${#infile[@]} > 1)); then
		warn "found more than one favicon image in assets"
		return 1
	elif ((${#infile[@]} == 0)); then
		warn "found no favicon image in assets"
		return 1
	fi

	# Make sure to only use first frame if animated GIF
	convert "${infile[0]}[0]" -resize 32x32^ -gravity center -background none \
		-extent 32x32 docs/favicon.png
}

# Build all pages
build() {
	clean

	if ! favicon; then
		warn "could not find or convert favicon; skipping"
	fi

	# Build index file and convert posts
	{
		printf '%s\n' '# All posts'
		local f
		for f in ????-??-??-*.md; do
			printf -- ':::\n[%s](%s)\n:::index-title\n\n:::\n%s\n:::index-date\n\n' \
				"$(extracttitle "$f")" "${f/%.md/.html}" "${f:0:10}"
			md2html "$f"
		done | tac
	} > index.md

	# Convert index file
	md2html index.md

	# Add Atom feed
	buildfeed > "$feedpath"

	rm index.md
	cp "$cssfile" docs
	cp "$calicon" docs/images
}

# Build Atom feed entry for the provided file, in YAML
buildentry() {
	local file=$1

	title=$(extracttitle "$file") \
	url=$(getconfvalue 'baseurl') \
	fname=${file/%md/html} \
	updated=$(git log --max-count=1 --format=format:%aI -- "$file") \
	summary=$(yq --front-matter=extract '.summary' "$file") \
	published=$(git log --format=format:%aI -- "$file" | tail --lines=1) \
		yq --null-input '
			[{
				"title": {
					"+@type": "html",
					"+content": strenv(title)
				},
				"id": strenv(url) + "/" + strenv(fname),
				"updated": strenv(updated),
				"content": {
					"+@src": strenv(url) + "/" + strenv(fname),
					"+@type": "text/html"
				},
				"link": {
					"+@href": strenv(url) + "/" + strenv(fname),
					"+@rel": "alternate",
					"+@type": "text/html",
					"+@title": strenv(title)
				},
				"summary": {
					"+@type": "html",
					"+content": strenv(summary)
				},
				"published": strenv(published)
			}]
		'
}

# Build feed entries, truncate to 10 most recent posts, reverse chronologically
buildentries() {
	local files=(????-??-??-*.md)
	if ((${#files[@]} > 10)); then
		files=("${files[@]: -10}")
	fi

	local i
	for ((i = 0; i < ${#files[@]}; ++i)); do
		buildentry "${files[-(1 + i)]}"
	done
}

# Build Atom feed, in XML
buildfeed() {
	echo "Buiding Atom feed..." >&2

	title=$(getconfvalue 'blogtitle') \
	url=$(getconfvalue 'baseurl') \
	name=$(getconfvalue 'authorname') \
	email=$(getconfvalue 'authoremail') \
	icon=$([[ -f docs/favicon.png ]] && echo "/favicon.png") \
	entries=$(buildentries) \
		yq --null-input --output-format=xml '
			.+p_xml = "version=\"1.0\" encoding=\"utf-8\""
			| .feed = {
				"+@xmlns": "http://www.w3.org/2005/Atom",
				"+@xmlns:webfeeds": "http://webfeeds.org/rss/1.0",
				"title": strenv(title),
				"id": strenv(url) + "/",
				"updated": now,
				"author": {
					"name": strenv(name),
					"email": strenv(email),
					"uri": strenv(url) + "/"
				},
				"link": [
					{
						"+@href": strenv(url) + "/feed.xml",
						"+@rel": "self",
						"+@type": "application/atom+xml"
					},
					{
						"+@href": strenv(url) + "/",
						"+@rel": "alternate",
						"+@type": "text/html"
					}
				],
				"generator": {
					"+@uri": "https://bewuethr/pandoc-bash-blog",
					"+content": "pandoc-bash-blog"
				},
				"icon": strenv(icon),
				"webfeeds:icon": strenv(icon),
				"webfeeds:cover": {
					"+@image": strenv(icon)
				},
				"entry": env(entries)
			}
		'
}

# Monitor directory for file modifications and print names of modified files
monitor() {
	# Use unbuffered uniq to suppress multiple events within the same second,
	# then throw away timestamp column
	inotifywait --monitor --quiet --recursive --event modify,moved_to \
		--exclude '\.sw.$' --timefmt '%s' --format $'%T\t%w%f' . \
		| stdbuf --output=L uniq \
		| stdbuf --output=L cut --field 2
}

# Serve blog from localhost
serve() {
	if [[ ! -e docs/index.html ]]; then
		die "can't find index file; try \"pbb build\""
	fi

	python -m http.server --directory docs &
	local pid=$!
	trap 'kill $pid' EXIT

	# Rebuild only changed files
	local fname
	while IFS= read -r fname; do
		case $fname in
			./*.md)
				echo "Rebuilding $fname..."
				md2html "${fname#./}"
				;;
			./images/*)
				echo "Copying $fname to images..."
				cp "$fname" docs/images
				;;
		esac
	done < <(monitor)
}

# Commit changes in publishing source and push them
deploy() {
	if [[ ! -e docs/index.html ]]; then
		die "can't find index file; try \"pbb build\""
	fi

	git add docs
	git commit --message='Publish blog'
	git push "${args[@]}"
}

main() {
	set -o errexit -o pipefail

	if (($# < 1)); then
		usage
		exit 1
	fi

	local subcmd=$1

	case $subcmd in
		help) usage ;;

		init)
			if (($# < 2)); then
				die "usage: pbb init TITLE"
			fi
			init "${*:2}"
			;;

		set)
			if (($# < 3)); then
				die "usage: pbb set PROPERTY VALUE"
			fi

			local property=$2
			case $property in
				title) setblogtitle "${*:3}" ;;
				gccode) setgccode "$3" ;;
				baseurl | authorname | authoremail) setconfvalue "$property" "$3" ;;
				*) die "invalid property \"$3\"" ;;
			esac
			;;

		enable)
			if (($# < 2)); then
				die "usage: pbb enable FEATURE"
			fi
			setfeature "$2" 'on'
			;;

		disable)
			if (($# < 2)); then
				die "usage: pbb disable FEATURE"
			fi
			setfeature "$2" 'off'
			;;

		build) build ;;

		serve) serve ;;

		deploy) deploy ;;

		*)
			usage
			exit 1
			;;
	esac
}

if [[ ${BASH_SOURCE[0]} == "$0" ]]; then
	main "$@"
fi