tbd-view

#!/usr/bin/env bash
#
set -eo pipefail

prompt_prefix=${1:?}
tbd_pid=${1%%.*}

# where commands are written to and outputs are to be read from and shown
tbd_pipe=.tbd-out.$$
mkfifo "$tbd_pipe"
echo "$tbd_pipe"      # output line 1

# where the current source line number should be written to by the debugger
view_pipe=.tbd-view.$$
mkfifo "$view_pipe"
echo "$view_pipe"     # output line 2

fifo-ack () {
    local fifo=${1:-${tbd_pipe:?}}
    echo ACK > "$fifo"
}

main () {
    : ${tbd_pid:?} ${prompt_prefix:?} ${window_id:?}
    [[ -p "${tbd_pipe:?}"  ]]
    [[ -p "${view_pipe:?}" ]]
    trap '
        set +e
        tmux kill-pane -t ":$window_id.right"
        rm -f "$view_pipe" "$tbd_pipe" "$0"
        history -a
    ' EXIT

    ( while kill -0 $tbd_pid >/dev/null 2>&1; do sleep 1; done
      kill $$
    ) &
    view-source-pane

    HISTFILE=$HOME/.tbd_history; history -r || true
    local line response rc
    while true; do
        response=$(cat "$tbd_pipe") && fifo-ack
        if [[ $response == "$prompt_prefix"* ]]; then
            IFS= read -erp "${response#$prompt_prefix}" line || rc=$?
            [[ ! $line ]] || history -s "$line"
            [[ ${rc:-0} == 0 ]] || break  # NOTE: Exiting the loop on Ctrl-D could potentially make the debugged script stuck on a break point.
            echo "$line" > "$tbd_pipe"
        else
            printf "%s\n" "$response"
        fi
    done
    echo /resume > "$tbd_pipe"
}

view-source-pane () {
    [[ -p ${view_pipe:?} ]]

    source-viewer () {
        if which batcat >/dev/null 2>&1; then bat () { batcat "$@"; }; fi
        local pipe=${1:?} file from to
        while true; do
            file=$(cat "$pipe") && fifo-ack "$pipe"
            read -t2 -r from to < "$pipe" && fifo-ack "$pipe"
            bat --color always ${NO_COLOR:+--color never} \
                --highlight-line "$from:${to:-$from}" "$file" \
                | less -K -RX +${from}g
        done
    }
    local view_script; view_script=$(mktemp)
    cat > "$view_script" <<EOF
#!/usr/bin/env bash
#
set -eo pipefail

$(declare -f fifo-ack)
$(declare -f source-viewer)
$(if [[ ${NO_COLOR:-} ]]; then echo export NO_COLOR=x; fi)

trap 'rm -f "\$0"' EXIT

source-viewer "\$@"
EOF
    chmod +x "$view_script"
    tmux split-window -dh -t ":$window_id" "$view_script" "$view_pipe"
}

window_name=$$; tmux new-window -n "$window_name"
window_id=$(tmux display-message -t ":=$window_name" -pF '#{window_id}')
echo "$window_id"     # output line 3

repl_script=$(mktemp)
cat > "$repl_script" <<EOF
#!/usr/bin/env bash
set -e

$(declare -p tbd_pid prompt_prefix tbd_pipe view_pipe window_id)
$(if [[ ${NO_COLOR:-} ]]; then echo export NO_COLOR=x; fi)

$(declare -f fifo-ack)
$(declare -f view-source-pane)

$(declare -f main)

clear
main \"\$@\"
EOF

chmod +x "$repl_script"

tmux send-key -t ":$window_id" "exec $(printf %q "$repl_script")"$'\n'