module MultiRepo::Helpers
  class License
    attr_reader :repo, :dry_run

    def initialize(repo, dry_run: false, **)
      @repo    = repo
      @dry_run = dry_run
      reload
    end

    def save!
      save_license!
      save_readme_license!
      reload unless dry_run
      true
    end

    def content
      @license.text
    end

    def license
      @license.key
    end

    def license=(value)
      @license = Licensee::License.new(value)
    end

    private

    def reload
      require 'licensee'
      @license = Licensee.license(repo.path.to_s)
    end

    def save_license!
      repo.rm_file("LICENSE.md", dry_run: dry_run)
      repo.rm_file("LICENSE", dry_run: dry_run)
      repo.write_file("LICENSE.txt", content, dry_run: dry_run)
    end

    def save_readme_license!
      readme_file = repo.detect_readme_file
      lines = readme_file ? File.read(repo.path.join(readme_file)).lines : []
      readme_file ||= "README.md"

      apply_readme_license!(lines)
      repo.write_file(readme_file, lines.join, dry_run: dry_run)
    end

    def extract_readme_license(lines)
      section = lines.each.with_index.drop_while do |l, _i|
        !l.downcase.include?("## license")
      end.take_while.with_index do |(l, _i), i2|
        i2 == 0 || !l.start_with?("## ")
      end

      section.each { |l, _i| l =~ /(mit|apache)/i && break }
      type =
        case $1.presence&.downcase
        when "mit"    then "mit"
        when "apache" then "apache-2.0"
        end

      return type, section.map(&:last)
    end

    def license_details
      case license
      when "mit"
        {
          :name => "MIT License",
          :url  => "https://opensource.org/licenses/MIT"
        }
      when "apache-2.0"
        {
          :name => "Apache License 2.0",
          :url  => "http://www.apache.org/licenses/LICENSE-2.0"
        }
      end
    end

    def apply_readme_license!(lines)
      readme_license, readme_license_indexes = extract_readme_license(lines)
      return if readme_license == license

      details = license_details
      return unless details

      lines.reject!.with_index { |_l, i| readme_license_indexes.include?(i) }

      start_index = readme_license_indexes[0] || lines.size
      new_lines = <<~EOF.lines
## License

This project is available as open source under the terms of the [#{details[:name]}](#{details[:url]}).

EOF

      new_lines.reverse_each do |l|
        lines.insert(start_index, l)
      end
    end
  end
end