Rake Task to Add Poirot's pre commit git hooks

Poirot_SetUp.rake

namespace :poirot do
  desc "Sets up Poirot's Git hooks for the local .git repository."
  task :install_githooks do
    def poirot_bash_script
      <<~HEREDOC
        #!/usr/bin/env bash

        function setup_poirot()
        {
            # Output to stderr
            exec 1>&2
            # Allow user input
            exec < /dev/tty
        }

        function setup_failure()
        {
            # Don't invoke Poirot for commits made from GitHub Desktop GUI
            echo "Couldn't set up Poirot to receive user input."
            exit 0
        }

        function run_poirot()
        {
            # Color codes for output
            RED="\033[1;31m"
            BLUE="\033[34m"
            RESET="\033[0m"

            # Run Poirot
            echo "Running Poirot..."

            if [ -n "$patterns_folder" ]; then
                echo "Pattern files:"
                for pattern_file in "$patterns_folder"/*.txt
                do
                    echo $pattern_file
                    patterns=$patterns","$pattern_file
                done
            fi
            poirot --staged --patterns="$patterns"

            # Read sys.exit from Poirot
            # Request input if match(es) found
            if [ $? -eq 1 ]
            then
                echo "${RED}Some pattern matches were found in your staged changes. Are you sure want to commit? Choose an option #.${RESET}"
                OPTIONS="Commit Cancel"
                select opt in $OPTIONS; do
                    if [ "$opt" = "Commit" ]; then
                        echo "${BLUE}Committing.${RESET}"
                        exit 0
                    elif [ "$opt" = "Cancel" ]; then
                        echo "${BLUE}Canceling commit. Go ahead and make any new changes.${RESET}"
                        exit 1
                    else
                        clear
                    fi
                done
            else
                exit 0
            fi
        }

        patterns_folder=""
        patterns=""

        # Read in optional patterns folder and patterns files
        while getopts "f:p:" opt; do
        case $opt in
            f)
            patterns_folder="$OPTARG"
            ;;
            p)
            patterns="$OPTARG"
            ;;
            \?)
            echo "Invalid option: -$OPTARG" >&2
            exit 1
            ;;
        esac
        done

        setup_poirot || setup_failure
        run_poirot
      HEREDOC
    end

    def guards
      # checks that all requirements are installed
      raise 'No .git directory found.' unless Dir.exist? '.git'
      raise 'No poirot installed' unless system('which poirot')
    end

    def create_precommit_poirot_file
      File.open('.git/hooks/pre-commit-poirot', 'w+') do |file|
        file.write(poirot_bash_script)
      end
    end

    def create_git_hook_precommit_poirot
      # creates file .git/hooks/pre-commit-poirot or overwrites it
      if File.exists?('.git/hooks/pre-commit-poirot')
        old_content = File.read('.git/hooks/pre-commit-poirot')
        unless old_content == poirot_bash_script
          puts 'Overwriting .git/hooks/pre-commit-poirot'
          create_precommit_poirot_file
        end
      else
        create_precommit_poirot_file
      end
    end

    def create_git_hook_precommit(git_hook_string)
      # To make it imdepotent first check that it doesn't contain the content already.
      if File.exists?('.git/hooks/pre-commit')
        old_content = File.read('.git/hooks/pre-commit')
        if old_content['.git/hooks/pre-commit-poirot']
          # update_git_hook(pattern_file, old_content)
          raise "#{git_hook_string} has to be updated manually on .git/hooks/pre-commit"
        else
          append_git_hook(git_hook_string)
        end
      else
        append_git_hook(git_hook_string)
      end
    end

    def append_git_hook(git_hook_string)
      # append this line git hook string to .git/hooks/pre-commit
      File.open('.git/hooks/pre-commit', 'a+') do |file|
        file.write git_hook_string
      end
    end

    guards
    pattern_file = ''
    pattern_list = ''
    git_hook_string = ".git/hooks/pre-commit-poirot -f #{pattern_file} -p #{pattern_list}"
    create_git_hook_precommit_poirot
    create_git_hook_precommit(git_hook_string)
    # Add executable bit to .git/hooks/pre-commit-poirot & .git/hooks/pre-commit
    FileUtils.chmod '+x', %w[.git/hooks/pre-commit-poirot .git/hooks/pre-commit]
  end
end