watch.sh

#!/bin/bash

set -eufo pipefail

# Kill background processes on script exit.
trap '[[ -n "$(jobs -p)" ]] && kill $(jobs -p) &> /dev/null' EXIT

usage() {
    cat <<EOS
Usage: $0 [-hbd]

This script watches code in frontend/ and backend/ for changes, automatically
rebuilding and (for backend changes) restarting the server.

Options:

    -h  Display this help message.
    -b  Backend-only (do not watch frontend/).
    -d  Run the server with DEPLOYMENT=1 (see 'make help' for details).
EOS
}

die() {
    echo "$0: $*" >&2
    exit 1
}

# Prefix output with "$1: " using bold ANSI color $2.
prefix() {
    sed "s/^/\x1b[$2;1m$1:\x1b[0m /"
}

prefix_watch() {
    prefix "WATCH" 32 # green
}

prefix_npm() {
    prefix "NPM" 33 # yellow
}

prefix_server() {
    prefix "SERVER" 34 # blue
}

watch_frontend=true
deployment=0

while getopts "hbd" opt; do
    case $opt in
        h) usage; exit 0 ;;
        b) watch_frontend=false ;;
        d) deployment=1 ;;
        *) exit 1 ;;
    esac
done
shift $((OPTIND - 1))
if [[ $# -gt 0 ]]; then
    die "unexpected arguments: $*"
fi

if ! command -v inotifywait &> /dev/null; then
    die "inotifywait not found"
fi

cd "$(dirname "$0")"

if [[ "$watch_frontend" == true ]]; then
    # Unless NO_COLOR is set, pass FORCE_COLOR to npm (which would otherwise
    # disable color because its output is piped).
    color=1
    [[ -n "${NO_COLOR+x}" ]] && color=0
    FORCE_COLOR=$color npm run --prefix frontend watch 2>&1 | prefix_npm &
fi

rebuild() {
    # Kill the "make run" process whose parent is this script.
    pkill -x make -P $$ 2>&1 | prefix_watch || :
    if make backend 2>&1 | prefix_watch; then
        make run DEPLOYMENT=$deployment 2>&1 | prefix_server &
    fi
}

rebuild
while read -r _ _ event_filename; do
    echo "$event_filename changed" | prefix_watch
    rebuild
done < <(inotifywait -m -e close_write backend 2> >(prefix_watch > /dev/tty))