require "uri"
require "../handler"
require "../mime-type"
require "../views/html/page"

class Guff::Handlers::GuffStuffHandler < Guff::Handler
  def initialize(models)
    super(models)
    @digests = {} of String => String
  end

  def call(context : HTTP::Server::Context)
    path = context.request.path.not_nil!

    if matching_request?(context.request.method, path)
      reply(context)
    else
      call_next(context)
    end
  end

  private def reply(context : HTTP::Server::Context)
    # get expanded path to file
    if path = expand_path(context.request.path.not_nil!)
      # get file digest
      file_digest = digest(path)

      # check for cache header
      if context.request.headers["if-none-match"]? == file_digest
        # cached, send 304 not modified
        context.response.status_code = 304
      else
        # not cached, set code and send headers
        context.response.status_code = 200
        context.response.content_type = Guff::MimeType.mime_type(path)
        context.response.content_length = File.size(path)
        context.response.headers["etag"] = file_digest

        if context.request.method == "GET"
          # send body
          File.open(path) do |fh|
            IO.copy(fh, context.response)
          end
        end
      end
    else
      # file not found
      context.response.status_code = 404
    end
  end

  VALID_METHODS = %w{GET HEAD}
  PATH_RE = %r{^/guff-stuff/}

  private def matching_request?(method, path)
    VALID_METHODS.includes?(method) && PATH_RE.match(path)
  end

  private def expand_path(req_path : String) : String?
    # unescape path, check for nil byte
    path = URI.unescape(req_path)
    return nil if path.includes?('\0')

    # build absolute path
    r = File.join(
      @models.config["stuff"],
      File.expand_path(path.gsub(PATH_RE, ""), "/")
    )

    # return path if file exists, or nil otherwise
    File.file?(r) ? r : nil
  end

  private def digest(path : String) : String
    @digests[path] ||= OpenSSL::Digest.new("SHA1").file(path).hexdigest
  end
end