manicito/manicito

#!/bin/sh
#―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――
# Name: manicito (Manic-citation)
# Desc: A Mastodon/Pleroma bot which Quote-posts all posts of the given hashtag.
# Reqs: curl, shell, jq
# Date: 2024-04-10
#―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――

if test -z "$MANICITO_TEMPLATE"; then
	MANICITO_TEMPLATE='$USER (<a href="$USER_URL">$USERHOST</a>) <a href="$POST_URL">posted</a> about $HASHTAG: <blockquote>$(echo "$POST" | head -c 200)</blockquote>'
fi

# Prints a simple usage message.
usage() {
	echo "usage: $(basename $0) [-h] [-H HISTORY_FILE] HASHTAG SERVER_URL"
	echo 'Mastodon/Pleroma/etc script to quote-posts all posts of a given hashtag.'
	echo
	echo '  -h             print this message and exit'
	echo '  -H             file used to store/check quoted posts; to avoid duplicates'
	echo
	echo 'Posts tagged under HASHTAG will all be quote-posted to the'
	echo 'Mastodon-compatible server at SERVER_URL.'
	echo
	echo 'In order to make these posts, you must set the environment variable $FEDI_AUTH'
	echo 'to your authorization token. To find your authorization token, you can snoop '
	echo 'through request headers in your web-browser. In Firefox, you can do:'
	echo '    Developer Tools (F12) → Network → Headers'
	echo 'Look for your $FEDI_AUTH value in the Authorization header like so:'
	echo '    Authorization: Bearer $FEDI_AUTH'
	echo
	echo 'To avoid duplicate-posts, you should specify a “history” file with the -H'
	echo 'parameter. With this, all quoted post IDs will be saved in this file, and'
	echo 'on subsequent runs (so long as you don’t change the history-file), no post'
	echo 'will be quoted twice.'
	echo
	echo 'The environment variable $MANICITO_TEMPLATE is used create the body of your'
	echo 'quote-posts. It substitutes the following shell-variables in templates:'
	echo '   • $HASHTAG'
	echo '   • $POST'
	echo '   • $POST_URL'
	echo '   • $USER'
	echo '   • $USER_URL'
}


# Fetch a JSON array of posts of a hashtag. If a minimum post ID is provided,
# only posts older than that one will be returned.
#     fetch_hashtag_posts $server $hashtag $minimum_id
fetch_hashtag_posts() {
	local server="$1"
	local hashtag="$2"
	local minimum_id="$3"

	if test -n "$minimum_id"; then
		curl --fail "$server/api/v1/timelines/tag/$hashtag?min_id=$minimum_id"
	else
		curl --fail "$server/api/v1/timelines/tag/$hashtag"
	fi
}


# Given a post’s JSON, create and submit a quote-post for it.
#     quote_post $tagged_post_json
quote_post() {
	local tagged_post_json="$1"
	curl --fail \
		 --request POST \
		 --header "Authorization: Bearer $FEDI_AUTH" \
		 --header 'Content-Type: application/json' \
		 --header "Idempotency-Key: $(echo "$tagged_post_json" | jq -r .id)" \
		 --data "$(post_json "$tagged_post_json")" "$FEDI_SERVER/api/v1/statuses"
}


# Given a JSON-array of posts over stdin, create and submit a quote-post for each one.
#     $posts_json_array | quote_posts
quote_posts() {
	local IFS="
"
	while read -r tagged_post_line; do
		quote_post "$tagged_post_line"
		if test "$?" -ne 0; then
			echo "Failed to post about post $(echo "$tagged_post_line" | jq .id)!" 1>&2
			exit 1
		fi
		echo "$tagged_post_line"
	done
}


# Given a post’s JSON, return JSON of a quote-post quoting it.
#     post_json $tagged_post-json
post_json() {
	local tagged_post_json="$1"
	printf '{ "content_type": "text/html", "visibility": "unlisted",'
	printf '"quote_id": "%s",' "$(echo "$tagged_post_json" | jq  -r .id)"
	printf '"expires_in": %s,' 864000
	printf '"status": "%s" }\n' "$(post_body "$tagged_post_json")"
}


# Output the contents of our quote-post’s body about the given tagged-post’s JSON.
# This uses the global variable $MANICITO as our template, replacing the variables
# $POST, $POST_URL, $USER, $USER_URL, and $USERHOST.
#     post_body $tagged_post_json
post_body() {
	local tagged_post_json="$1"
	POST="$(echo "$tagged_post_json" | jq -r .content | tr -d "\"'\n")"
	POST_URL="$(echo "$tagged_post_json" | jq -r .uri)"
	USER="$(echo "$tagged_post_json" | jq -r .account.display_name)"
	USER_URL="$(echo "$tagged_post_json" | jq -r .account.url)"
	USERHOST="$(echo "$tagged_post_json" | jq -r .account.acct)"
	env_subst "$MANICITO_TEMPLATE"
}


# Receives posts in a JSON array over stdin. Given a newline-delimited list of
# post IDs ($ids_to_filter), all matching posts from the JSON array will be
# filted out.# sent over stdin that match one of these posts IDs will be filtered out.
#     echo $post_array_json | filter_posts $ids_to_filter
filter_posts() {
	local ids_to_filter="$1"
	# If the list has more than give characters, use it to filter… (sanity check)
	if test -n "$ids_to_filter"; then
		jq -cr .[] \
			| grep --invert-match $(echo "$ids_to_filter" | sed 's%^%-e %')
	else
		jq -cr .[]
	fi
}


history_post_ids() {
	local history_file="$1"
	if test -f "$history_file"; then
		awk -F '\t' '{print $2}' "$history_file" \
			| grep -v '^[[:space:]]*$'
	fi
}


# Pipe in fediverse posts in JSON format; these will all be echoed into the given
# “history file”, so that they can be filtered out and avoided on subsequent
# runs.
#     echo $newline_delimited_post_jsons | update_filter $history_file
update_filter() {
	local history_file="$1"
	if test -n "$history_file"; then
		jq -r '(.created_at + "\t" +  .id)' \
			| sort -n \
				   >> "$history_file"
	fi
}


# Sanitize a template-string.
# AKA, escape quotation-marks.
#     prep_template $template
prep_template() {
	local template="$1"
	echo "$template" \
		| sed 's%\"%\\\"%g'
}


# Rough replacement for gettext’s envsubst. Safe!
# This will evaluate a string’s shell variables (somewhat) safely
# Probably not good for general use — but for our purposes, it only subsitutes
# along the “first level.” So environment variables are replaced, but those
# variables’ contents (AKA, post contents) aren’t evaluated.
#     env_subst $template
#     env_subst "$SHELL"  →  "/bin/sh"
env_subst() {
	local template="$1"
	eval "echo \"$(prep_template "$template")\""
}


while getopts 'hH:' arg; do
	case $arg in
		h)
			usage
			exit 0
			;;
		H)
			HISTORY_FILE="$OPTARG"
			;;
	esac
done

shift $((OPTIND-1))
HASHTAG="$1"
FEDI_SERVER="$2"


if test -z "$HASHTAG"; then
	usage
	exit 1
fi

if test -z "$FEDI_AUTH"; then
	1>&2 echo 'You need to set the environment variable $FEDI_AUTH!'
	1>&2 echo 'You can find your auth key by examining the "Authorization: Bearer" header'
	1>&2 echo "used in requests by your server's web-client."
    1>&2 echo 'In Firefox, F12→Network.'
	1>&2 echo ""
	exit 2
fi

if test -z "$FEDI_SERVER"; then
	1>&2 echo 'No server specified!'
	1>&2 echo 'Make sure to provide a hashtag (like #esperanto) and a'
	1>&2 echo 'server URL (like https://fedi.server) as the last two arguments.'
	1>&2 echo
	1>&2 echo 'Run with -h for more information.'
	exit 3
fi


POST_IDS_TO_IGNORE="$(history_post_ids "$HISTORY_FILE")"
MOST_RECENT_POST="$(echo "$POST_IDS_TO_IGNORE" | tail -1)"

fetch_hashtag_posts "$FEDI_SERVER" "$HASHTAG" "$MOST_RECENT_POST" \
	| filter_posts "$POST_IDS_TO_IGNORE" \
	| quote_posts \
	| update_filter "$HISTORY_FILE"