#!/bin/sh

colorscan() {
awk '
function fg(c, s) { return sprintf("\033[38;5;%03dm%s\033[0m", c, s) }
function so(s) { return sprintf("\033[1m%s\033[0m", s) }
/^>/ { print so(fg(119, $0)); next }
/^ *\\_/ { print fg(242, $0); next }
{ print }'
}

clear_buf() {
	i=0
	while [ "$i" -le "$1" ]; do
		tput cup "$i" 0
		tput el
		: $(( i=i+1 ))
	done
}

hline=0
bline=1
bcol=1

body_buf=$(mktemp /tmp/.mcurse_body.XXXXX)
body_len=
body_max=

term_init() {
	cols=$(tput cols)
	rows=$(tput lines)
	start_headers=$(( rows / 3 ))
	start_body=$(( start_headers + 1 ))
	end_body=$(( rows - start_body - 2))
	term_clear_headers=$(clear_buf "$start_headers"; tput cup 0 0)
	term_clear_body=$(tput cup "$(( start_body ))" 0; tput ed)
	term_move_status=$(tput cup "$(( rows ))" $(( cols - 5 )); tput el)
	term_move_cmd=$(tput cup "$(( rows ))" 0)
	term_init_cmd=$(tput cnorm; tput el)
	term_done_cmd=$(tput civis)
}

statusline() {
	printf "%s%s" "$term_move_status" "$@"
}

cmdline() {
	printf "%s%s:" "$term_move_cmd" "$term_init_cmd"
	stty "$stty_default"
	tput cnorm
	read -r cmd
	case "$cmd" in
		"|"*) ;;
		"!"*) ;;
	esac
	printf "%s" "$term_done_cmd"
	stty -echo -icanon
	headers
	body
}

update() {
	bline=1
	[ "$bcol" -le 0 ] && bcol=1
	mshow 2>/dev/null | mcolor | cut -c "$(( bcol ))-$(( cols + bcol - 1 ))" | trunc_lines >"$body_buf"
	body_len=$(wc -l <"$body_buf")
	: $(( body_len = body_len + 1 ))
	: $(( body_max = body_len - end_body ))
	update_body=1
}

trunc_lines() {
	t=$(tput el)
	while read -r l; do
		printf "%s%s\n" "$l" "$t"
	done
}

headers() {
	printf "%s" "$term_clear_headers"

	: $(( x = hline - (start_headers / 2) ))
	: $(( y = hline + (start_headers / 2) ))

	[ "$x" -gt 0 ] && x="+$x"
	[ "$y" -gt 0 ] && y="+$y"

	COLUMNS=$cols mscan ".$x:.$y" 2>/dev/null | colorscan
}

body() {
	[ "$bline" -gt "$body_max" ] && bline=$body_max
	[ "$bline" -lt 1 ] && bline=1

	: $(( x = bline ))
	: $(( y = end_body + bline ))

	[ "${update_body}" = "${x},${y}p" ] && return

	printf "%s" "$term_clear_body"

	update_body="${x},${y}p"
	sed -n "$update_body" "$body_buf"

	[ "$body_len" -gt "$end_body" ] \
		&& statusline "$(( 100 * y / body_len ))%"
}

draw() {
	headers
	body
}

init() {
	tput smcup # save position
	tput civis # cursor invisible
	term_init

	stty_default=$(stty -g)
	stty -echo -icanon

	update
	draw
}

close() {
	tput sgr0 # reset char attributes
	tput cnorm # normal cursor
	tput rmcup # restore position
	stty "$stty_default" # restore stty settings
	[ -e "$body_buf" ] && rm "$body_buf"
	exit "${1-0}"
}

readchar() {
	c=$(dd bs=1 count=1 2>/dev/null)
	printf '%d' "'$c"
}


in_buf=
in_cnt1=1
in_cnt2=1
in_cur=

in_read() {
	set -- $in_buf
	[ "$#" -eq 0 ] && in_cur=$(readchar) && return
	in_cur=$1; shift; in_buf=$@
}

in_back() {
	set -- "$in_cur" $in_buf
	in_buf=$@
}

in_prefix() {
	n=
	while [ "$in_cur" -le 59 ] && [ "$in_cur" -ge 47 ]; do
		: $(( n = n * 10 + $(printf \\$(printf "%03o" "$in_cur")) ))
		in_read
	done
	[ "$1" -eq "1" ] && in_cnt1=${n:-1} || in_cnt2=${n:-1}
}

in_motion() {
	case "$in_cur" in
	# $
	36) mseq -C "$" ;;
	# ^
	94) mseq -C 1 ;;
	# j
	106) mseq -C ".+$in_cnt1" ;;
	# k
	107) mseq -C ".-$in_cnt1" ;;
	# P
	80) mseq -C "$(mseq ".-1=" | head -n1 | mscan -n)" ;;
	# N
	78) mseq -C "$(( $(mseq ".=" | tail -n1 | mscan -n) + 1 ))" ;;
	# p
	112) mseq -C "$(mseq "._" | head -n1 | mscan -n)" ;;
	# n
	110) mseq -C "$(mseq "._" | tail -n1 | mscan -n)" ;;
	# [
	91) mseq -C "$(mseq ".=" | head -n1 | mscan -n)" ;;
	# ]
	93) mseq -C "$(mseq ".=" | tail -n1 | mscan -n)" ;;
	*) return 1 ;;
	esac
}

in_motionln() {
	cnt=$(( in_cnt1 * in_cnt2 ))
	mv=
	case "$in_cur" in
	# return j +
	0|106|125) mv=".:$(mseq ".+$cnt" | mscan -n)" ;;
	# - k
	45|107) mv="$(mseq ".-$cnt" | mscan -n):." ;;
	# G
	71) mv=".:$" ;;
	*) return 1 ;;
	esac
}

in_action() {
	c=$in_cur
	in_read
	in_prefix 2
	in_motionln || [ "$in_cur" -eq "$c" ] && mv="."
	case "$c" in
	# d
	100)
		mseq "$mv" | mflag -v -S : >/dev/null
		mseq -f : | mseq -S
		headers
		;;
	# u
	117)
		mseq "$mv" | mflag -v -s : >/dev/null
		mseq -f : | mseq -S
		headers
		;;
	*) return 1 ;;
	esac
}

in_esc() {
	stty min 0 time 1
	c=$(readchar)
	rv=0
	echo "esc $c" >>./log
	case "$c" in
	91)
		c=$(readchar)
		# page up/down
		[ "$c" -eq 53 ] && : $(( bline-=end_body ))
		[ "$c" -eq 54 ] && : $(( bline+=end_body ))
		c=$(readchar)
		body
		;;
	*) c=$(readchar); c=$(readchar); rv=1 ;;
	esac
	stty min 1 time 0
	return $rv
}

trap 'close 130;' INT TERM

init

while :; do
	in_buf=
	in_cur=
	int_cnt1=1
	int_cnt2=1

	in_read
	[ "$in_cur" -eq 27 ] && in_esc && continue

	in_prefix 1
	in_motion && update && draw && continue

	case "$in_cur" in
	# d u
	100|117) in_action ;;
	# D
	68) in_cur="100"; in_back; in_action ;; # input buffer to dd
	# U
	85) in_cur="117"; in_back; in_action ;; # input buffer to uu
	# e
	101) ${EDITOR=ed} $(mseq .) && update && draw ;;
	# v
	118) ${VISUAL=vi} $(mseq .) && update && draw ;;
	# L | C-l
	76|12) tput clear && term_init && update && draw ;;
	# :
	58) cmdline ;;
	# q
	113) close ;;
	# c
	99) hline=0 && headers ;;
	# J
	74) : $(( bline+=in_cnt1 )) && body ;;
	# K
	75) : $(( bline-=in_cnt1 )) && body ;;
	*) ;;
	esac
	printf "%s" "$term_move_cmd"
done