require 'arvados/keep'

class Collection < ArvadosModel
  include HasUuid
  include KindAndEtag
  include CommonApiTemplate

  before_validation :check_encoding
  before_validation :check_signatures
  before_validation :strip_manifest_text
  before_validation :set_portable_data_hash
  validate :ensure_hash_matches_manifest_text

  # Query only undeleted collections by default.
  default_scope where("expires_at IS NULL or expires_at > CURRENT_TIMESTAMP")

  api_accessible :user, extend: :common do |t|
    t.add :name
    t.add :description
    t.add :properties
    t.add :portable_data_hash
    t.add :signed_manifest_text, as: :manifest_text
  end

  def self.attributes_required_columns
    # If we don't list this explicitly, the params[:select] code gets
    # confused by the way we expose signed_manifest_text as
    # manifest_text in the API response, and never let clients select
    # the manifest_text column.
    super.merge('manifest_text' => ['manifest_text'])
  end

  def check_signatures
    return false if self.manifest_text.nil?

    return true if current_user.andand.is_admin

    # Provided the manifest_text hasn't changed materially since an
    # earlier validation, it's safe to pass this validation on
    # subsequent passes without checking any signatures. This is
    # important because the signatures have probably been stripped off
    # by the time we get to a second validation pass!
    return true if @signatures_checked and @signatures_checked == compute_pdh

    if self.manifest_text_changed?
      # Check permissions on the collection manifest.
      # If any signature cannot be verified, raise PermissionDeniedError
      # which will return 403 Permission denied to the client.
      api_token = current_api_client_authorization.andand.api_token
      signing_opts = {
        key: Rails.configuration.blob_signing_key,
        api_token: api_token,
        ttl: Rails.configuration.blob_signing_ttl,
      }
      self.manifest_text.lines.each do |entry|
        entry.split[1..-1].each do |tok|
          if /^[[:digit:]]+:[[:digit:]]+:/.match tok
            # This is a filename token, not a blob locator. Note that we
            # keep checking tokens after this, even though manifest
            # format dictates that all subsequent tokens will also be
            # filenames. Safety first!
          elsif Blob.verify_signature tok, signing_opts
            # OK.
          elsif Keep::Locator.parse(tok).andand.signature
            # Signature provided, but verify_signature did not like it.
            logger.warn "Invalid signature on locator #{tok}"
            raise ArvadosModel::PermissionDeniedError
          elsif Rails.configuration.permit_create_collection_with_unsigned_manifest
            # No signature provided, but we are running in insecure mode.
            logger.debug "Missing signature on locator #{tok} ignored"
          elsif Blob.new(tok).empty?
            # No signature provided -- but no data to protect, either.
          else
            logger.warn "Missing signature on locator #{tok}"
            raise ArvadosModel::PermissionDeniedError
          end
        end
      end
    end
    @signatures_checked = compute_pdh
  end

  def strip_manifest_text
    if self.manifest_text_changed?
      # Remove any permission signatures from the manifest.
      self.class.munge_manifest_locators!(self[:manifest_text]) do |loc|
        loc.without_signature.to_s
      end
    end
    true
  end

  def set_portable_data_hash
    if (portable_data_hash.nil? or
        portable_data_hash == "" or
        (manifest_text_changed? and !portable_data_hash_changed?))
      @need_pdh_validation = false
      self.portable_data_hash = compute_pdh
    elsif portable_data_hash_changed?
      @need_pdh_validation = true
      begin
        loc = Keep::Locator.parse!(self.portable_data_hash)
        loc.strip_hints!
        if loc.size
          self.portable_data_hash = loc.to_s
        else
          self.portable_data_hash = "#{loc.hash}+#{portable_manifest_text.bytesize}"
        end
      rescue ArgumentError => e
        errors.add(:portable_data_hash, "#{e}")
        return false
      end
    end
    true
  end

  def ensure_hash_matches_manifest_text
    return true unless manifest_text_changed? or portable_data_hash_changed?
    # No need verify it if :set_portable_data_hash just computed it!
    return true if not @need_pdh_validation
    expect_pdh = compute_pdh
    if expect_pdh != portable_data_hash
      errors.add(:portable_data_hash,
                 "does not match computed hash #{expect_pdh}")
      return false
    end
  end

  def check_encoding
    if manifest_text.encoding.name == 'UTF-8' and manifest_text.valid_encoding?
      true
    else
      begin
        # If Ruby thinks the encoding is something else, like 7-bit
        # ASCII, but its stored bytes are equal to the (valid) UTF-8
        # encoding of the same string, we declare it to be a UTF-8
        # string.
        utf8 = manifest_text
        utf8.force_encoding Encoding::UTF_8
        if utf8.valid_encoding? and utf8 == manifest_text.encode(Encoding::UTF_8)
          manifest_text = utf8
          return true
        end
      rescue
      end
      errors.add :manifest_text, "must use UTF-8 encoding"
      false
    end
  end

  def redundancy_status
    if redundancy_confirmed_as.nil?
      'unconfirmed'
    elsif redundancy_confirmed_as < redundancy
      'degraded'
    else
      if redundancy_confirmed_at.nil?
        'unconfirmed'
      elsif Time.now - redundancy_confirmed_at < 7.days
        'OK'
      else
        'stale'
      end
    end
  end

  def signed_manifest_text
    if has_attribute? :manifest_text
      token = current_api_client_authorization.andand.api_token
      @signed_manifest_text = self.class.sign_manifest manifest_text, token
    end
  end

  def self.sign_manifest manifest, token
    signing_opts = {
      key: Rails.configuration.blob_signing_key,
      api_token: token,
      ttl: Rails.configuration.blob_signing_ttl,
    }
    m = manifest.dup
    munge_manifest_locators!(m) do |loc|
      Blob.sign_locator(loc.to_s, signing_opts)
    end
    return m
  end

  def self.munge_manifest_locators! manifest
    # Given a manifest text and a block, yield each locator,
    # and replace it with whatever the block returns.
    manifest.andand.gsub!(/ [[:xdigit:]]{32}(\+[[:digit:]]+)?(\+\S+)/) do |word|
      if loc = Keep::Locator.parse(word.strip)
        " " + yield(loc)
      else
        " " + word
      end
    end
  end

  def self.normalize_uuid uuid
    hash_part = nil
    size_part = nil
    uuid.split('+').each do |token|
      if token.match /^[0-9a-f]{32,}$/
        raise "uuid #{uuid} has multiple hash parts" if hash_part
        hash_part = token
      elsif token.match /^\d+$/
        raise "uuid #{uuid} has multiple size parts" if size_part
        size_part = token
      end
    end
    raise "uuid #{uuid} has no hash part" if !hash_part
    [hash_part, size_part].compact.join '+'
  end

  # Return array of Collection objects
  def self.find_all_for_docker_image(search_term, search_tag=nil, readers=nil)
    readers ||= [Thread.current[:user]]
    base_search = Link.
      readable_by(*readers).
      readable_by(*readers, table_name: "collections").
      joins("JOIN collections ON links.head_uuid = collections.uuid").
      order("links.created_at DESC")

    # If the search term is a Collection locator that contains one file
    # that looks like a Docker image, return it.
    if loc = Keep::Locator.parse(search_term)
      loc.strip_hints!
      coll_match = readable_by(*readers).where(portable_data_hash: loc.to_s).limit(1).first
      if coll_match
        # Check if the Collection contains exactly one file whose name
        # looks like a saved Docker image.
        manifest = Keep::Manifest.new(coll_match.manifest_text)
        if manifest.exact_file_count?(1) and
            (manifest.files[0][1] =~ /^[0-9A-Fa-f]{64}\.tar$/)
          return [coll_match]
        end
      end
    end

    if search_tag.nil? and (n = search_term.index(":"))
      search_tag = search_term[n+1..-1]
      search_term = search_term[0..n-1]
    end

    # Find Collections with matching Docker image repository+tag pairs.
    matches = base_search.
      where(link_class: "docker_image_repo+tag",
            name: "#{search_term}:#{search_tag || 'latest'}")

    # If that didn't work, find Collections with matching Docker image hashes.
    if matches.empty?
      matches = base_search.
        where("link_class = ? and links.name LIKE ?",
              "docker_image_hash", "#{search_term}%")
    end

    # Generate an order key for each result.  We want to order the results
    # so that anything with an image timestamp is considered more recent than
    # anything without; then we use the link's created_at as a tiebreaker.
    uuid_timestamps = {}
    matches.all.map do |link|
      uuid_timestamps[link.head_uuid] = [(-link.properties["image_timestamp"].to_datetime.to_i rescue 0),
       -link.created_at.to_i]
    end
    Collection.where('uuid in (?)', uuid_timestamps.keys).sort_by { |c| uuid_timestamps[c.uuid] }
  end

  def self.for_latest_docker_image(search_term, search_tag=nil, readers=nil)
    find_all_for_docker_image(search_term, search_tag, readers).first
  end

  protected
  def portable_manifest_text
    portable_manifest = self[:manifest_text].dup
    self.class.munge_manifest_locators!(portable_manifest) do |loc|
      loc.hash + '+' + loc.size.to_s
    end
    portable_manifest
  end

  def compute_pdh
    portable_manifest = portable_manifest_text
    (Digest::MD5.hexdigest(portable_manifest) +
     '+' +
     portable_manifest.bytesize.to_s)
  end
end