# TODO
# run as service
# federation
# client post media
# client follow
# client get media
# server follow
# test with pleroma etc
require 'json'
require 'net/http'
require 'uri'
require 'base64'
require 'securerandom'
require 'fileutils'
require 'digest/sha2'
require 'nokogiri'

USER = "pdp8"
WWW_DOMAIN = "pdp8.info"
WWW_URL = "https://#{WWW_DOMAIN}"
SOCIAL_DOMAIN = "social.#{WWW_DOMAIN}"

ACCOUNT = "#{USER}@#{SOCIAL_DOMAIN}"
SOCIAL_URL = "https://#{SOCIAL_DOMAIN}"
ACTOR = File.join(SOCIAL_URL, USER)

class Application
  def call(env)
    code = 404
    type = 'application/ld+json; profile="https://www.w3.org/ns/activitystreams"'
    response = "Not found."

    case env['REQUEST_METHOD']

    when 'POST'
      input = env["rack.input"].read
      case env["REQUEST_PATH"]

      when "/inbox" # receive from server
        if verify(env)
          begin
            object = JSON.parse(input)
            case object["type"]
            when "Create"
              File.open(File.join("inbox", SecureRandom.uuid + ".json"), "w+") { |f| f.puts input }
            when "Delete"
              puts input
            when "Follow"
              File.open(File.join("followers", SecureRandom.uuid + ".json"), "w+") { |f| f.puts input }
              accept = { "@context" => "https://www.w3.org/ns/activitystreams",
                         "id" => File.join(SOCIAL_URL + "#accepts", SecureRandom.uuid),
                         "type" => "Accept",
                         "actor" => ACTOR,
                         "object" => JSON.parse(input) }
              send accept, [accept["object"]["actor"]]
            when "Undo"
              o = object["object"]
              # puts o
              case o["type"]
              when "Follow"
                Dir["followers/*.json"].each do |follower|
                  puts follower
                  # puts JSON.parse(File.read(follower))["actor"]
                  if JSON.parse(File.read(follower))["actor"] == o["actor"]
                    FileUtils.rm follower
                  end
                end
                # ordered_collection("followers")
              end
              # puts input
            else
              puts input
            end
            code = 200
            response = "OK"
          rescue => e
            puts input, e.to_s
            response = "Request body contains invalid json."
          end
        else
          code = 403
          response = "Key verification failed for POST to #{env["REQUEST_URI"]}."
        end

      when "/outbox" # receive from client
        if auth(env)
          code, response = parse input
        else
          code = 403
          response = "You are not allowed to POST to #{env["REQUEST_URI"]}."
        end

      when "/follow" # receive from client
        if auth(env)
          input.split.each do |mention|
            actor = actor(mention)
            follow = { "@context" => "https://www.w3.org/ns/activitystreams",
                       "id" => File.join(SOCIAL_URL, "following", SecureRandom.uuid + ".json"),
                       "type" => "Follow",
                       "actor" => ACTOR,
                       "object" => actor }
            save follow
            puts(send follow, [actor])
            code = 200
            response = "OK"
          end
        else
          code = 403
          response = "You are not allowed to POST to #{env["REQUEST_URI"]}."
        end

      when "/unfollow" # receive from client
        if auth(env)
          input.split.each do |mention|
            actor = actor(mention)
            Dir["following/*.json"].each do |f|
              follow = JSON.parse(File.read(f))
              puts follow
              if follow["object"] == actor
                undo = { "@context" => "https://www.w3.org/ns/activitystreams",
                         "id" => File.join(SOCIAL_URL + "#undo", SecureRandom.uuid),
                         "type" => "Undo",
                         "actor" => ACTOR,
                         "object" => follow }
                send undo, [actor]
                FileUtils.rm f
              end
            end
          end
        end
      end

    when 'GET'

      case env["REQUEST_URI"] # REQUEST_PATH does not contain queries

      when "/.well-known/webfinger?resource=acct:#{ACCOUNT}"
        type = "application/jrd+json"
        response = File.read("webfinger")
        code = 200

      when "/#{USER}"
        # TODO serve html
        response = File.read(USER)
        code = 200

      when "/inbox"
        if auth(env)
          type, response = format ordered_collection(env["REQUEST_PATH"]), env["HTTP_ACCEPT"]
          code = 200
        else
          code = 403
          response = "You are not allowed to GET #{env["REQUEST_URI"]}."
        end

      when %r{/[outbox|following|followers|likes|shares]}
        response = ordered_collection(env["REQUEST_PATH"]).to_json
        code = 200
      end

    end
    [code, { "Content-Type" => type }, [response]]
  end

  def parse input
    date = Time.now.strftime("%Y-%m-%dT%H:%M:%S")
    # TODO media attachments, hashtags
    note = {
      "@context" => "https://www.w3.org/ns/activitystreams",
      "id" => File.join(SOCIAL_URL, "note", SecureRandom.uuid + ".json"),
      "type" => "Note",
      "attributedTo" => ACTOR,
      "published" => date,
      "content" => ""
    }
    create = {
      "@context" => "https://www.w3.org/ns/activitystreams",
      "id" => File.join(SOCIAL_URL, "create", SecureRandom.uuid + ".json"),
      "type" => "Create",
      "actor" => ACTOR,
      "object" => note,
      "published" => date,
    }
    recipients = []
    if /^@/.match input
      mentions, input = input.split("\n", 2)
      mentions.split(/, */).each do |m|
        recipients << actor(m.chomp)
      end
    end
    note["content"] = input.lines.select { |l| !l.empty? }.join("<br>")
    recipients += Dir[File.join("followers", "*.json")].collect { |f| JSON.parse(File.read(f))["actor"] }
    recipients.delete ACTOR
    recipients.uniq!
    note["to"] = recipients
    create["to"] = recipients

    save create
    save note
    FileUtils.ln_s File.join('..', path(create)), "outbox"

    responses = send create, recipients
    if responses.collect { |r| r.code.to_i }.uniq.max < 400
      code = 200
      response = "OK"
    else
      code = 502
      response = responses.select { |r| r.code.to_i >= 400 }.collect { |r| r.body }.uniq
    end
    [code, response]
  end

  def format response, accept
    if accept == "text/plain"
      response = response["orderedItems"].collect.with_index do |r, i|
        object = r["object"]
        doc = Nokogiri::HTML(object["content"])
        str = "#{i}\t#{object["published"]}\t#{}\n#{doc.text}"
        str << "\n" + object["attachment"].collect { |att|
                        `kitty +kitten icat #{att["url"]}`
                      }.join("\n") if object["attachment"]
        str
      end.join("\n\n")
      type = "text/plain"
    else
      response = response.to_json
      type = 'application/ld+json; profile="https://www.w3.org/ns/activitystreams"'
    end
    [type, response]
  end

  def actor mention
    mention = mention.sub(/^@/, '').chomp
    user, server = mention.split("@")
    get("https://#{server}/.well-known/webfinger?resource=acct:#{mention}",
        "application/jrd+json")["links"].select { |l|
      l["rel"] == "self"
    }[0]["href"]
  end

  def send object, urls
    # puts object, urls
    # https://github.com/mastodon/mastodon/blob/main/app/lib/request.rb
    keypair = OpenSSL::PKey::RSA.new(File.read('private.pem'))
    responses = []
    urls.each do |url|
      date = Time.now.utc.httpdate
      uri = URI.parse(url)

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

      signed_string = "(request-target): post #{inbox uri}\nhost: #{uri.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 + '"'

      uri = URI.parse(get(url)["inbox"])
      http = Net::HTTP.new(uri.host, uri.port)
      http.use_ssl = true
      header = {
        'Content-Type' => 'application/activity+json',
        'Host' => uri.host,
        'Date' => date,
        'Digest' => digest,
        'Signature' => signed_header,
      }
      request = Net::HTTP::Post.new(uri.request_uri, header)
      request.body = body

      responses << http.request(request)
    end
    # puts responses
    responses
  end

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

  def inbox uri
    URI(get(uri)["inbox"]).request_uri
  end

  def get url, accept = 'application/ld+json; profile="https://www.w3.org/ns/activitystreams"'
    uri = URI(url)
    http = Net::HTTP.new(uri.host, uri.port)
    http.use_ssl = true
    header = { 'Accept' => accept }
    request = Net::HTTP::Get.new(uri.request_uri, header)
    response = http.request(request)
    JSON.parse(response.body)
  end

  def path object
    object["id"].sub(SOCIAL_URL, '').sub('/', '')
  end

  def save object
    path = path object
    FileUtils.mkdir_p File.dirname(path)
    File.open(path, "w+") { |f| f.puts object.to_json }
  end

  def verify env
    # https://github.com/mastodon/mastodon/blob/main/app/controllers/concerns/signature_verification.rb
    # TODO verify digest
    signature_params = {}
    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 = get 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}: #{env["CONTENT_TYPE"]}"
      else
        "#{signed_params_name}: #{env["HTTP_" + signed_params_name.upcase]}"
      end
    end.join("\n")

    key.verify(OpenSSL::Digest.new('SHA256'), signature, comparison)
  end

  def auth env
    auth = Rack::Auth::Basic::Request.new(env)
    usr = File.read(".usr").chomp
    pwd = File.read(".pwd").chomp
    auth.provided? && auth.basic? && auth.credentials && auth.credentials == [usr, pwd]
  end
end