# -*- encoding: utf-8 -*-
#
#--
# This file is part of HexaPDF.
#
# HexaPDF - A Versatile PDF Creation and Manipulation Library For Ruby
# Copyright (C) 2014-2017 Thomas Leitner
#
# HexaPDF is free software: you can redistribute it and/or modify it
# under the terms of the GNU Affero General Public License version 3 as
# published by the Free Software Foundation with the addition of the
# following permission added to Section 15 as permitted in Section 7(a):
# FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
# THOMAS LEITNER, THOMAS LEITNER DISCLAIMS THE WARRANTY OF NON
# INFRINGEMENT OF THIRD PARTY RIGHTS.
#
# HexaPDF is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public
# License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with HexaPDF. If not, see <http://www.gnu.org/licenses/>.
#
# The interactive user interfaces in modified source and object code
# versions of HexaPDF must display Appropriate Legal Notices, as required
# under Section 5 of the GNU Affero General Public License version 3.
#
# In accordance with Section 7(b) of the GNU Affero General Public
# License, a covered work must retain the producer line in every PDF that
# is created or manipulated using HexaPDF.
#++

require 'fiber'
require 'zlib'
require 'hexapdf/filter/predictor'
require 'hexapdf/configuration'
require 'hexapdf/error'

module HexaPDF
  module Filter

    # Implements the Deflate filter using the Zlib library.
    #
    # See: HexaPDF::Filter, PDF1.7 s7.4.4
    module FlateDecode

      class Pool #:nodoc:

        # Creates a new Zlib::Stream pool. A block must be given that returns a new Zlib::Stream
        # instance.
        def initialize(&block)
          @creator = block
          @pool = []
        end

        # Returns the next available stream of the pool, already reset to its initial state.
        def next_available
          @pool.find(-> { e = @creator.call; @pool << e; e }, &:finished?).tap(&:reset)
        end

      end

      @inflate_pool = Pool.new { Zlib::Inflate.new }
      @deflate_pool = Pool.new do
        Zlib::Deflate.new(HexaPDF::GlobalConfiguration['filter.flate_compression'],
                          Zlib::MAX_WBITS,
                          HexaPDF::GlobalConfiguration['filter.flate_memory'])
      end

      # See HexaPDF::Filter
      def self.decoder(source, options = nil)
        fib = Fiber.new do
          inflater = @inflate_pool.next_available
          while source.alive? && (data = source.resume)
            begin
              data = inflater.inflate(data)
            rescue
              raise FilterError, "Problem while decoding Flate encoded stream: #{$!}"
            end
            Fiber.yield(data)
          end
          begin
            inflater.finish
          rescue
            raise FilterError, "Problem while decoding Flate encoded stream: #{$!}"
          end
        end

        if options && options[:Predictor]
          Predictor.decoder(fib, options)
        else
          fib
        end
      end

      # See HexaPDF::Filter
      def self.encoder(source, options = nil)
        if options && options[:Predictor]
          source = Predictor.encoder(source, options)
        end

        Fiber.new do
          deflater = @deflate_pool.next_available
          while source.alive? && (data = source.resume)
            data = deflater.deflate(data)
            Fiber.yield(data)
          end
          deflater.finish
        end
      end

    end

  end
end