#!/bin/sh
## twerk: a twtxt client
# by Case Duckworth

### Entry point

usage() {
	cat >&2 <<EOF
TWERK: a twtxt client
usage: twerk [options] [file]

twerk can be fed a list of URLs from standard input or from a FILE.
Each line is expected to contain a URL of a twtxt feed and (optionally) the
display name to use for that feed.

options (default):
 -h          Show this help and exit.
 -t          Include the time in each post date.
 -f          Force redownload of twt data.
 -n LIMIT    Only show LIMIT posts (25).  0 means no limit.
 -w WIDTH    Limit the output's width to WIDTH characters (72).
 -W WIDTH    Limit the username's width to WIDTH characters (12).
 -i INDENT   Use INDENT spaces as a hanging indent for too-long lines
             ([calculated]).
 -p COMMAND  Use COMMAND to post twts ([not set]).
             This command will be fed a twtxt-formatted string via stdin.
             Recommended: \`ssh <host> tee -a <file>\`.
 -u USER     The username to use when twting ([current user name]).

parameters:
 FILE        List of twtxt feeds to fetch, one feed per line.
             Optionally, a string after the feed URL will be its
             display name.
EOF
	exit "${1:-0}"
}

configure() {
	# defaults
	TWERK_WIDTH="${TWERK_WIDTH:-72}"
	TWERK_LIMIT="${TWERK_LIMIT:-25}"
	TWERK_INCLUDE_TIME="${TWERK_INCLUDE_TIME:-0}"
	TWERK_USER_WIDTH="${TWERK_USER_WIDTH:-12}"
	TWERK_HANG="${TWERK_HANG:-}" # empty to calculate off other variables
	TWERK_FORCE="${TWERK_FORCE:-false}"
	TWERK_POST_COMMAND="${TWERK_POST_COMMAND:-:}" # no-op
	TWERK_USER="$(whoami)"

	while getopts htfn:w:W:i:p:c:u: opt
	do
		case "$opt" in
			h) usage ;;
			t) TWERK_INCLUDE_TIME=1 ;;
			f) TWERK_FORCE=true ;;
			n) TWERK_LIMIT="$OPTARG" ;;
			w) TWERK_WIDTH="$OPTARG" ;;
			W) TWERK_USER_WIDTH="$OPTARG" ;;
			i) TWERK_HANG="$OPTARG" ;;
			p) TWERK_POST_COMMAND="$OPTARG" ;;
			c) TWERK_FEEDS="$OPTARG" ;;
			u) TWERK_USER="$OPTARG" ;;
			*) usage 1 ;;
		esac
	done

	if test -z "$TWERK_HANG"
	then
		TWERK_HANG=$((TWERK_USER_WIDTH+(TWERK_INCLUDE_TIME*6)+10+3))
	fi
}

main() {
	TWERK_CACHE="${XDG_CACHE_HOME:-$HOME/.cache}/twerk"
	mkdir -p "$TWERK_CACHE"
	TWERK_FILE="$TWERK_CACHE/:file:"

	TWERK_LESSKEY="$TWERK_CACHE/:lesskey:"
	lesskey_setup

	if "$_TWERK_INITIAL"
	then
		configure "$@"
		shift "$((OPTIND - 1))"
		TWERK_FEEDS="$1"
	fi

	cat "$TWERK_FEEDS" |
		fetch_posts |
		sort_posts |
		limit_posts "$TWERK_LIMIT" |
		format_posts > "$TWERK_FILE"

	read_posts "$TWERK_FILE"
	# cat "$TWERK_FILE"
}

remain() {
	_TWERK_INITIAL=false main "$TWERK_FEEDS"
}

### Library

fetch_posts() {
	while read -r url name
	do
		if test -z "$name"
		then
			file="$TWERK_CACHE/$(url_normalize "$name")"
		else
			file="$TWERK_CACHE/$name"
		fi

		if "$TWERK_FORCE" || test -z "$(find "$file" -prune -mtime -1 2>/dev/null)"
		then
			printf >&2 'Downloading %s...\n' "$url"
			curl -sf "$url" |
				filter_lines |
				while read -r date post
				do
					printf '%s\t%s\t%s\t%s\n' \
					       "$date" "$name" "$url" "$post"
				done |
				tee "$file"
		else
			cat "$file"
		fi
	done
}

url_normalize() {
	printf '%s\n' "$1" | tr -d ':/~'
}

filter_lines() {
	while read -r line
	do
		case "$line" in
			\#*) ;;
			'') ;;
			*) printf '%s\n' "$line" ;;
		esac
	done
}

limit_posts() {
	ln=0
	while read -r line
	do
		if test "$1" -ne 0 && test "$ln" -gt "$1"
		then
			break
		fi
		printf '%s\n' "$line"
		ln=$((ln+1))
	done
}

sort_posts() {
	sort -r
}

struncate() {
	printf '%s\n' "$1" |
		dd ibs=1 count="$2" 2>/dev/null
}

format_posts() {
	while IFS='	' read -r date name url post
	do
		if test 0 -eq "$TWERK_INCLUDE_TIME"
		then
			TWERK_DATE_WIDTH=10
			date="${date%T*}"
		else
			TWERK_DATE_WIDTH=16
		fi

		printf "%${TWERK_DATE_WIDTH}s | %${TWERK_USER_WIDTH}s | " \
		       "$(struncate "$date" "$TWERK_DATE_WIDTH")" \
		       "$(struncate "$name" "$TWERK_USER_WIDTH")"

		export url name date post TWERK_WIDTH TWERK_HANG
		export linewidth="$TWERK_HANG"

		printf '%s\n' "$post" |
			tr ' ' '\n' |
			while IFS= read -r word
			do
				pword=
				case "$word" in
					\@\<*\>)
						word="${word#@<}"
						word="${word%>}"
						pword="@${word}"
						word="@${word}"
						;;
					\@\<*)
						read nextword
						case "$nextword" in
							*\>)
								word="${word#@<}"
								pword="@${word}"
								word="@${word}"
								;;
							*)
								word="$word $nextword"
								;;
						esac
						;;
				esac

				if test $(( linewidth + ${#word} )) -ge "$TWERK_WIDTH"
				then
					echo
					linewidth=0
					printf "%${TWERK_HANG}s \` " ""
					linewidth=$((linewidth+TWERK_HANG+2))
				fi

				printf '%s ' "${pword:-$word}"
				linewidth=$((linewidth + ${#word}))
			done
		echo
	done
}


lesskey_setup() {
	# t will exit with code 48
	if ! test -r "$TWERK_LESSKEY"
	then
		lesskey -o "$TWERK_LESSKEY" - <<EOF
#command
t quit 0
g quit 1
#line-edit
#env
EOF
	fi
}

read_posts() {
	less \
		-k "$TWERK_LESSKEY" \
		-Pm'twerk! t\: twt, g\: refresh' -m \
		"$1"

	case "$?" in
		0) exit ;;
		48) post ;;
		49) refresh ;;
	esac
}

post() {
	printf 'Twt: ' >&2
	read -r post

	post="$(post_expand_ats "$post")"

	if printf '%s\n' "$post" | grep -qE '^[ \t\n]$'
	then
		remain
	fi

	post="$(printf '%s\t%s\n' "$(date +'%FT%T%z')" "$post")"

	eval "printf '%s\n' \"\$post\" | $TWERK_POST_COMMAND"
	rm "$TWERK_CACHE/$TWERK_USER"
	remain
}

post_expand_ats() {
	TWERK_POST="$TWERK_CACHE/:post:"
	printf '%s\n' "$@" |
		tr ' ' '\n' |
		while read -r word; do
			case "$word" in
				@*)
					url="$(grep "${word#@}" "$TWERK_FEEDS" | cut -d' ' -f1)"
					if test -n "$url"
					then
						printf '@<%s %s> ' \
						       "${word#@}" "$url"
					else
						printf '%s ' "$word"
					fi
					;;
				*) printf '%s ' "$word";;
			esac
		done > "$TWERK_POST"
	echo >> "$TWERK_POST"

	if grep -q @ "$TWERK_POST"
	then
		cat "$TWERK_POST" >&2
		printf '%s\n' "Correct? [Y/n] " >&2
		read -r yn
		case "$yn" in
			n*|N*)
				head -n1 "$TWERK_POST" >&2
				post
				;;
			y*|Y*|'') ;;
			*) return 3 ;;
		esac
	fi
	head -n1 "$TWERK_POST"
}

refresh() {
	TWERK_FORCE=true main "$TWERK_FEEDS"
}

###################################
_TWERK_INITIAL=true
test -z "$DEBUG" || set -x
test -z "$SOURCE" && main "$@"