Install ragel during build if needed

bin/setup

@@ -5,13 +5,4 @@ set -euo pipefail
 bundle
 
 # install ragel
-if [[ $(command -v ragel) == "" ]]; then
-  if [[ $(command -v brew) != "" ]]; then
-    brew install ragel
-  elif [[ $(command -v apt-get) != "" ]]; then
-    sudo apt-get install -y ragel
-  else
-    echo "could not install ragel, please do so manually"
-    exit 1
-  fi
-fi
+rake ragel:install

tasks/ragel.rake

@@ -4,7 +4,7 @@ RAGEL_SOURCE_FILES = %w[scanner] # scanner.rl imports the other files
 
 namespace :ragel do
   desc 'Process the ragel source files and output ruby code'
-  task :rb do
+  task rb: :install do
     RAGEL_SOURCE_FILES.each do |source_file|
       output_file = "#{RAGEL_OUTPUT_DIR}/#{source_file}.rb"
       # using faster flat table driven FSM, about 25% larger code, but about 30% faster
@@ -26,4 +26,19 @@ namespace :ragel do
       sh "rm -f #{RAGEL_OUTPUT_DIR}/#{file}.rb"
     end
   end
+
+  desc 'Make sure that ragel is installed'
+  task :install do
+    if system('command -v ragel')
+      # already installed
+    elsif system('command -v brew')
+      puts 'ragel not found, installing with homebrew ...'
+      `brew install ragel`
+    elsif system('command -v apt-get')
+      puts 'ragel not found, installing with apt-get ...'
+      `sudo apt-get install -y ragel`
+    else
+      raise 'Could not install ragel. Please install it manually.'
+    end
+  end
 end