helpers do

  def protected!
    redirect("/login.html") unless session['client']
  end

  def verify!
    # https://github.com/mastodon/mastodon/blob/main/app/controllers/concerns/signature_verification.rb
    # TODO verify digest
    begin
      signature_params = {}
      request.env["HTTP_SIGNATURE"].split(',').each do |pair|
        k, v = pair.split('=')
        signature_params[k] = v.gsub('"', '')
      end

      key_id = signature_params['keyId']
      headers = signature_params['headers']
      signature = Base64.decode64(signature_params['signature'])

      actor = fetch key_id
      key = OpenSSL::PKey::RSA.new(actor['publicKey']['publicKeyPem'])

      comparison = headers.split(' ').map do |signed_params_name|
        if signed_params_name == '(request-target)'
          '(request-target): post /inbox'
        elsif signed_params_name == 'content-type'
          "#{signed_params_name}: #{request.env["CONTENT_TYPE"]}"
        else
          "#{signed_params_name}: #{request.env["HTTP_" + signed_params_name.upcase]}"
        end
      end.join("\n")

      halt 400 unless key.verify(OpenSSL::Digest.new('SHA256'), signature, comparison)
    rescue => e
      p request.env["HTTP_SIGNATURE"], e
      halt 400
    end
  end

  def items
    nr = 0
    @items = Dir[File.join(@dir, '*.json')].sort.collect do |file|
      item = JSON.parse(File.read(file))
      mention = mention(item['attributedTo'])
      following_path = File.join('public', 'following', mention + '.json')
      File.exists?(following_path) ? follow = 'unfollow' : follow = 'follow'
      nr += 1
      { :id => item['id'],
        :nr => nr,
        :parent => item['inReplyTo'],
        :file => file,
        :actor_url => item['attributedTo'],
        :mention => mention,
        :follow => follow,
        :content => item['content'],
        :attachment => item['attachment'],
        :indent => 2,
        :replies => []
      }
    end.compact
    @items.last[:nr] = @items.last[:nr] - 2 unless @items.empty?
  end

  def threads
    items
    @threads = []
    @items.each do |i|
      if i[:parent].nil? or @items.select{|it| it[:id] == i[:parent] }.empty?
        @threads << i
      else
        @items.select{|it| it[:id] == i[:parent] }.each do |it|
          i[:indent] = it[:indent] + 2
          it[:replies] << i
        end
      end
    end
  end

  def html item
    @item = item
    erb :item
  end

  def delete object
    Dir["inbox/*.json"].each do |doc|
      FileUtils.rm doc if JSON.parse(File.read(doc))["id"] == object["id"]
    end
  end

  def create object
    unless object['type'] == 'Person'
      doc = File.join("inbox", "#{Time.now.strftime('%Y-%m-%dT%H:%M:%S.%N')}.json")
      File.open(doc, "w+") { |f| f.puts object.to_json }
      if object['inReplyTo']
        @dir = 'inbox'
        items
        if @items.select{|it| it[:id] == object['inReplyTo'] }.empty?
           download object['inReplyTo']
        end
      end
    end
  end

  def download object_url
    create fetch(object_url)
  end

  def people
    File.read('cache/people.tsv').split("\n").collect {|l| l.chomp.split("\t")}
  end

  def mention actor
    person = people.select{|p| p[1] == actor} 
    if person.empty?
      mention = "#{fetch(actor)["preferredUsername"]}@#{URI(actor).host}"
      File.open('cache/people.tsv','a'){|f| f.puts "#{mention}\t#{actor}"}
      mention
    else
      person[0][0]
    end
  end

  def actor mention
    mention = mention.sub(/^@/, '').chomp
    actors = people.select{|p| p[0] == mention} 
    if actors.empty?
      user, server = mention.split("@")
      actor = fetch("https://#{server}/.well-known/webfinger?resource=acct:#{mention}",
          "application/jrd+json")["links"].select { |l|
        l["rel"] == "self"
      }[0]["href"]
      File.open('cache/people.tsv','a'){|f| f.puts "#{mention}\t#{actor}"}
      actor
    else
      actors[0][0]
    end
  end

  def fetch url, accept = 'application/ld+json; profile="https://www.w3.org/ns/activitystreams"'
    p url
    response = `/run/current-system/sw/bin/curl --fail-with-body -sSL -H 'Accept: #{accept}' #{url}`
    halt 400 unless $?.success?
    JSON.parse(response)
  end

  def ordered_collection dir
    posts = Dir[File.join("public",dir, "*.json")].collect { |f| JSON.parse(File.read f) }.sort_by { |o| o["published"] }
    {
      "@context" => "https://www.w3.org/ns/activitystreams",
      "summary" => "#{USER} #{dir}",
      "type" => "OrderedCollection",
      "totalItems" => posts.size,
      "orderedItems" => posts,
    }
  end

  def send_signed object, url
    # https://github.com/mastodon/mastodon/blob/main/app/lib/request.rb
    keypair = OpenSSL::PKey::RSA.new(File.read('private.pem'))
    date = Time.now.utc.httpdate
    host = URI.parse(url).host
    inbox =  fetch(url)["inbox"]

    sha256 = OpenSSL::Digest::SHA256.new
    body = object.to_json
    digest = "SHA-256=" + sha256.base64digest(body)

    signed_string = "(request-target): post #{inbox}\nhost: #{host}\ndate: #{date}\ndigest: #{digest}\ncontent-type: application/activity+json"
    signature = Base64.strict_encode64(keypair.sign(OpenSSL::Digest.new('SHA256'), signed_string))
    signed_header = 'keyId="' + ACTOR + '#main-key",algorithm="rsa-sha256",headers="(request-target) host date digest content-type",signature="' + signature + '"'

    puts `/run/current-system/sw/bin/curl -i -X POST -H 'Content-Type: application/activity+json' -H 'Host: #{host}' -H 'Date: #{date}' -H 'Digest: #{digest}' -H 'Signature: #{signed_header}' -d '#{body}' #{inbox}`
  end

end