require 'ostruct'

module HerokuRelease
  @@config = OpenStruct.new(
    :heroku_remote => "heroku",
    :prompt_for_comments => true
  )

  def self.config
    @@config
  end

  def self.config=(config)
    @@config = config
  end
  
  class Task
    def self.tasks
      {
        :push => nil,
        :tag => nil,
        :log => "Produces a changelog from release tags and their comments. Assumes tag comments have no newlines in them.",
        :current_release => "Show version of current release",
        :previous_release => "Show version of previous release",
        :pending => "Show git commits since last released version",
        :rollback => "Rollback to previous release and remove current release tag"
      }      
    end
    
    def push
      output 'Deploying site to Heroku ...'
      execute "git push #{config.heroku_remote} master"
    end

    def tag
      release_name = get_release_name
      quoted_tag_comment = single_quote(tag_comment)

      if config.version_file_path || config.changelog_path
        if config.version_file_path
          output "Updating version file at #{config.version_file_path}"
          update_version_file(release_name)
        end
        if config.changelog_path
          output "Updating #{config.changelog_path}"
          update_changelog(release_name, tag_comment)
        end
        commit(release_name, quoted_tag_comment)
      end

      output "Tagging release as '#{release_name}'"
      execute "git tag -a #{release_name} -m '#{quoted_tag_comment}'"
      execute "git push --tags origin"
      execute "git push --tags #{config.heroku_remote}"
    end

    def log
      output("\n" + changelog)
    end

    def current_release
      output current_release_version
    end

    def previous_release
      if previous_release_version
        output previous_release_version
      else
        output "no previous release found"
      end
    end

    def pending
      execute "git log #{current_release_version}..HEAD"
    end

    def rollback
      # Store releases in local variables so they don't change during tag deletion
      current = current_release_version
      previous = previous_release_version
      if previous
        output "Rolling back to '#{previous}' ..."
        execute "git push -f #{config.heroku_remote} #{previous}:master"
        output "Removing rolled back release tag '#{current}' ..."
        remove_tag(current)
        output 'Rollback completed'
      else
        output "No release tags found - cannot do rollback"
        output releases
      end
    end

    private

    def remove_tag(tag_name)
      execute "git tag -d #{tag_name}"
      execute "git push #{config.heroku_remote} :refs/tags/#{tag_name}"
      execute "git push origin :refs/tags/#{tag_name}"
    end

    def single_quote(string)
      string.gsub("'") { %q{'\''} } # quote single quotes
    end

    def tag_comment
      return ENV['COMMENT'] if ENV['COMMENT']      
      if config.prompt_for_comments
        print "Required - please enter a release comment: "
        $stdin.gets.strip
      else
        'Tagged release'
      end
    end

    def output(message)
      puts message
    end

    def execute(command)
      output `#{command}`.strip
    end

    def releases
      @releases ||= git_tags.split("\n").select { |t| t[0..7] == 'release-' }.sort
    end

    def current_release_version
      releases.last
    end

    def previous_release_version
      if releases.length >= 2 && previous = releases[-2]
        previous
      else
        nil
      end    
    end

    def update_version_file(release_name)
      File.open(config.version_file_path, "w") { |f| f.print release_name }
      execute "git add #{config.version_file_path}"
    end

    def update_changelog(release_name, tag_comment)
      write_changelog(release_name, tag_comment)
      execute "git add #{config.changelog_path}"
    end
    
    def commit(release_name, quoted_tag_comment)
      execute "git commit -m '#{release_name}: #{quoted_tag_comment}'"
      execute "git push origin master"      
    end
    
    def write_changelog(release_name, tag_comment)
      changelog_entries_with_next = [[release_name, tag_comment]] + changelog_entries
      File.open(config.changelog_path, "w") { |f| f.print(changelog_warning + changelog(changelog_entries_with_next)) }
    end

    def changelog_warning
      "# NOTE: this file is autogenerated by the heroku_release gem - do not hand edit\n\n"
    end

    def changelog(entries = changelog_entries)
      entries.map do |release, comment|
        "- #{release}\n\n#{comment}\n\n"
      end.join
    end

    def changelog_entries
      git_tags_with_comments.scan(/^\s*(release-\d+-\d+)\s*(.+)$/).reverse
    end

    def get_release_name
      "release-#{Time.now.utc.strftime("%Y%m%d-%H%M%S")}"
    end

    def git_tags
      `git tag`
    end

    def git_tags_with_comments
      `git tag -n`
    end

    def config
      HerokuRelease.config
    end
  end
end