Rough but working start to running on the pi

pi/Gemfile

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+source "https://rubygems.org"
+ruby "3.2.1"
+
+gem "json"
+gem "puma"
+gem "rack"

pi/Gemfile.lock

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+GEM
+  remote: https://rubygems.org/
+  specs:
+    json (2.6.3)
+    nio4r (2.5.8)
+    puma (6.1.1)
+      nio4r (~> 2.0)
+    rack (3.0.4.2)
+
+PLATFORMS
+  arm64-darwin-21
+  armv7l-linux-eabihf
+
+DEPENDENCIES
+  json
+  puma
+  rack
+
+RUBY VERSION
+   ruby 3.2.1p31
+
+BUNDLED WITH
+   2.4.7

pi/config.ru

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+require "bundler/setup"
+
+require "net/http"
+require "json"
+
+class StopLight
+  RED_LED = "16"
+  GREEN_LED = "14"
+  YELLOW_LED = "15"
+
+  def self.startup
+    File.write("/sys/class/gpio/export", RED_LED) unless File.exist?("/sys/class/gpio/gpio#{RED_LED}/value")
+    File.write("/sys/class/gpio/export", GREEN_LED) unless File.exist?("/sys/class/gpio/gpio#{GREEN_LED}/value")
+    File.write("/sys/class/gpio/export", YELLOW_LED) unless File.exist?("/sys/class/gpio/gpio#{YELLOW_LED}/value")
+
+    sleep 1
+
+    set_color(RED_LED, "1")
+    set_color(GREEN_LED, "1")
+    set_color(YELLOW_LED, "1")
+
+    sleep 1
+
+    set_color(RED_LED, "0")
+    set_color(GREEN_LED, "0")
+    set_color(YELLOW_LED, "0")
+  end
+
+  def self.set_colors(colors)
+    set_color(RED_LED, colors["red"] ? "1" : "0")
+    set_color(GREEN_LED, colors["green"] ? "1" : "0")
+    set_color(YELLOW_LED, colors["yellow"] ? "1" : "0")
+  end
+
+  def self.set_color(pin, value)
+    File.write("/sys/class/gpio/gpio#{pin}/value", value)
+  end
+end
+
+StopLight.startup
+
+run do |env|
+  req = Rack::Request.new(env)
+  case req.path
+  when "/set-colors"
+    colors = JSON.parse(req.body.read)["colors"]
+    StopLight.set_colors(colors)
+    [200, {}, ["OK"]]
+  else
+    [404, {}, ["Not Found"]]
+  end
+end

pi/readme.txt

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+sudo apt update
+sudo apt dist-upgrade
+sudo reboot
+
+sudo apt install libcurl4-openssl-dev git libreadline6-dev libssl-dev libyaml-dev libxml2-dev libxslt-dev autoconf ncurses-dev automake libtool bison
+
+wget https://cache.ruby-lang.org/pub/ruby/3.2/ruby-3.2.1.tar.gz
+tar xzf ruby-3.2.1.tar.gz
+ruby-3.2.1/
+./configure --prefix=/usr/local --enable-shared --disable-install-doc
+make -j 2
+sudo make install
+
+curl https://my.webhookrelay.com/webhookrelay/downloads/install-cli.sh | bash
+vi relay_config.yml
+```
+version: "v1"
+key: KEY_HERE
+secret: SECRET_HERE
+buckets:
+  - Buildlight
+```
+sudo relay service install -c /home/pi/relay_config.yml --user pi
+sudo relay service start
+
+mkdir app
+copy config.ru Gemfile Gemfile.lock
+bundle config set --local path 'vendor'
+bundle install
+
+# Setup puma to load via systemd
+https://github.com/puma/puma/blob/master/docs/systemd.md
+
+Change:
+```
+User=pi
+WorkingDirectory=/home/pi/app
+ExecStart=/usr/local/bin/bundle exec puma -p 8080 -v --redirect-stdout /home/pi/app/server.log
+```
+