#!/bin/dash

: ${_o_allnet:=no}
: ${_o_append:=no}
: ${_o_asksub:=yes}
: ${_o_askbcc:=no}
: ${_o_askcc:=no}
: ${_o_autoprint:=no}
: ${_o_bang:=no}
: ${_o_cmd:=no}
: ${_o_crt:=no}
: ${_o_debug:=no}
: ${_o_dot:=no}
: ${_o_escape:="~"}
: ${_o_folder:=no}
: ${_o_header:=yes}
: ${_o_ignore:=no}
: ${_o_ignoreeof:=no}
: ${_o_indentprefix:="	"}
: ${_o_keep:=no}
: ${_o_keepsave:=no}
: ${_o_metoo:=no}
: ${_o_onehop:=no}
: ${_o_outfolder:=no}
: ${_o_page:=no}
: ${_o_prompt:="? "}
: ${_o_quiet:=no}
: ${_o_record:=no}
: ${_o_save:=yes}
: ${_o_screen:=}
: ${_o_sendwait:=no}
: ${_o_showto:=no}
: ${_o_sign:=no}
: ${_o_Sign:=no}
: ${_o_toplines:=5}

: ${EDITOR:=vim}
: ${LISTER:=ls}
: ${PAGER:=less}
: ${VISUAL:=vi}

: ${edit=}

: ${MAILSEQ:=.edmailseq}
: ${RLWRAP:=$(command -v rlwrap)}

export MAILSEQ

[ -n "${RLWRAP}" ] && \
	readln() { printf '%s' "$(rlwrap ${1:+"-S$1"} -o cat)"; } || \
	readln() { printf '%s' "$(printf '%s' "${1}"; read -r line)"; }

usage() {
	cat <<EOF
EOF
}

usage_tildecmd() {
	cat <<EOF
Tilde commands:
${_o_escape}[bct] name...	Add names to BCC, CC or TO.
${_o_escape}d		Read dead.letter file into message.
${_o_escape}[ev]		Invoke EDITOR or VISUAL text editor.
${_o_escape}[FfMm] msg	Include messages. [Mm] indented. [FM] with headers.
${_o_escape}p		Print current headers and message.
${_o_escape}[r<] file	Read the file into the message.
${_o_escape}w file		Write message onto the named file.
${_o_escape}s subject	Set the subject.
${_o_escape}! command	Execute a shell command.
${_o_escape}| command	Pipe the message through command.
${_o_escape}[:_] mail cmd	Execute the given mail command.
${_o_escape}q		Abort and save message into dead.letter file.
${_o_escape}x		Abort without saving the message.
${_o_escape}${_o_escape} text		Insert text into message prefaced by a single ${_o_escape}.
${_o_escape}.		Simulate end of file on input.\n"
EOF
}

draft() {
	draft=$(mktemp "/tmp/draft.XXXXXX")
	{
		printf 'to: %s\n' "${1:-$(readln "To: ")}"
		isset "$_o_asksub" && \
			printf 'subject: %s\n' "$(readln "Subject: ")"
		isset "$_o_askcc" && \
			printf 'cc: %s\n' "$(readln "Cc: ")"
		isset "$_o_askbcc" && \
			printf 'bcc: %s\n' "$(readln "Bcc: ")"
		isset "$_o_from" && \
			printf 'from: %s\n' "$_o_from"
		printf '\n'
	} >"$draft"
}

tildecmd() {
	cmd="${1#~*}"; shift
	set -- "$cmd" "$@"
	case "${cmd%%*~}" in
		b|c|t)
			shift
			case "${cmd%%*~}" in
				b) h="bcc" ;;
				c) h="cc" ;;
				t) h="to" ;;
			esac
			hdrapp "$draft" "$h" "$@"
			;;
		d) cat dead.letter >"$draft" ;;
		e|v)
			[ "${cmd#~*}" = "e" ] && ed="${EDITOR}" || ed="${VISUAL}"
			"$ed" "$draft"
			;;
		F|f|M|m)
			mshow -R "$2" >>"$draft"
			;;
		p)
			printf "%s\nMessage contains:\n" '-------'
			mshow "$draft"
			;;
		r|"<") cat "$2" >>"$draft" ;;
		w) cp "$draft" "$2" ;;
		s) shift; hdrset "$draft" "subject" "$@" ;;
		!*) bang "$@" ;;
		"|") (cat "$draft" | "$@") >"$draft" ;;
		":"|_) mailcmd "$@" ;;
		.) eot ;;
		q) eot ;;
		x) eot 1 ;;
		a) isset "$_o_sign" && printf '%s\n' "$_o_sign" >>"$draft" ;;
		A) isset "$_o_Sign" && printf '%s\n' "$_o_Sign" >>"$draft" ;;
		i) shift; printf '%s\n' "$@" >>"$draft";;
		~) printf '%s\n' "$@" >>"$draft";;
		*) usage_tildecmd ;;
	esac
}

edit() {
	edit=1
	while [ -n "$edit" ] && line=$(readln); do
		case "$line" in
			.) isset "$_o_dot" && eot && continue ;;
			"$_o_escape"*) tildecmd $line; continue ;;
		esac
		printf '%s\n' "$line" >>"$draft"
	done
}

eot() {
	edit=
	[ -z "$draft" ] && return
	[ "$#" -eq 0 ] && cp "$draft" dead.letter
	rm "$draft"
}

setopt() {
	s="$@"; k=${s%=*}; v=${s#*=}
	[ -z "$k" ] && set | sed -n 's/^_o_//p' && return
	case "$k" in no*) k=${k#*no}; v="no" ;; esac
	[ "$k" = "ask" ] && k="asksub"
	[ "$k" = "$v" ] && v=""
	eval "_o_$k=\"$v\""
}

hdrset() {
	f=$1; shift
	h=$1; shift
	s=$@
	sed -i "/^$h:/c\\$h: $s" "$f"
}

hdrapp() {
	f=$1; shift
	h=$1; shift
	s=$@
	[ -n "$(mhdr -h "$h" "$f")" ] && s=", $s"
	sed -i "/^$h:/ s/$/${s}/" "$f"
}

isset() {
	[ -n "$1" -a "$1" != "no" ]
}

bang() {
	eval "$(printf '%s' "$@" | cut -c 2-)"
	printf '!\n'
}

mailcmd() {
	cmd=$1
	case "$cmd" in
		"#"*) ;;
		!*) bang "$@" ;;
		ex|x) exit 1 ;;
		file|"fi"|fold|folder) _o_folder=$2; mailcmd inc ;;
		inc) isset "$_o_folder" && mlist $_o_folder | mseq -S ;;
		m|mail) draft "$2"; edit ;;
		se|set) shift; setopt "$@" ;;
		q|quit) exit 1 ;;
		*)
			case "$cmd" in
				f) cmd="from" ;;
				h) cmd="headers" ;;
				to) cmd="top" ;;
			esac
			e=$(mhdr -h "$cmd" ./cmd-tab)
			[ -z "$e" ] && printf 'unknwon cmd\n' && return
			shift
			eval "$e"
			;;
	esac
}

interactive() {
	isset "$_o_header" && mailcmd "headers"
	while line=$(readln "$_o_prompt"); do
		[ -z "$line" ] && continue
		mailcmd $line
	done
}

while read -r line; do
	mailcmd $line
done <<EOF
set folder=/home/duncan/mail/personal
inc
EOF

interactive