#!/bin/bash
# Fast per-keystroke helper for tmux-switch (called by fzf; python startup is too slow here).
#   tmux-switch-action <kind> <metafile>     kind: digits | esc | next-group | prev-group
#   tmux-switch-action preview <session> <window-index>
# metafile: one line per list entry, "h <idx>" (project header) or "w <idx>" (window).
NORMAL_PROMPT="# "
SEARCH_PROMPT="/ "
NORMAL_KEYS="j,k,g,G,l,q,J,K,/"

kind=$1

if [ "$kind" = preview ]; then
	# visible pane content minus trailing blank lines, bottom part that fits
	tmux capture-pane -e -p -J -t "$2:$3" |
		awk '{ l[NR] = $0 } END { n = NR; while (n > 0) { s = l[n]; gsub(/\033\[[0-9;]*m|[ \t]/, "", s); if (s != "") break; n-- } for (i = 1; i <= n; i++) print l[i] }' |
		tail -n "${FZF_PREVIEW_LINES:-40}"
	exit 0
fi

meta=$2
pos=${FZF_POS:-1}

case "$kind" in
esc)
	if [ "$FZF_PROMPT" = "$SEARCH_PROMPT" ]; then
		echo "disable-search+clear-query+change-prompt($NORMAL_PROMPT)+rebind($NORMAL_KEYS)"
	else
		echo abort
	fi
	;;
next-group | prev-group)
	awk -v pos="$pos" -v kind="$kind" '
		$1 == "h" { h[++nh] = NR } END {
			cur = 1; for (i = 1; i <= nh; i++) if (h[i] <= pos) cur = i
			t = cur
			if (kind == "next-group" && cur < nh) t = cur + 1
			if (kind == "prev-group" && cur > 1) t = cur - 1
			p = h[t] + 1; if (p > NR) p = NR
			printf "pos(%d)", p
		}' "$meta"
	;;
digits)
	[ "$FZF_PROMPT" = "$NORMAL_PROMPT" ] || exit 0
	q=$FZF_QUERY
	[ -n "$q" ] || exit 0
	case "$q" in *[!0-9]*) echo clear-query; exit 0 ;; esac
	awk -v q="$q" '
		$1 == "w" { idx[NR] = $2 } END {
			# does any window number start with q? else restart from the last digit
			for (n in idx) if (index(idx[n], q) == 1) found = 1
			if (!found) {
				q1 = substr(q, length(q))
				for (n in idx) if (index(idx[n], q1) == 1) { printf "change-query(%s)", q1; exit }
				printf "clear-query"; exit
			}
			exact = 0; longer = 0; first = 0
			for (n in idx) {
				if (idx[n] == q) exact = n
				else if (index(idx[n], q) == 1) longer = 1
				if (index(idx[n], q) == 1 && (first == 0 || n + 0 < first)) first = n + 0
			}
			if (exact) printf "pos(%d)%s", exact, (longer ? "" : "+accept")
			else printf "pos(%d)", first
		}' "$meta"
	;;
esac