module Ascii85Native

# File lib/ascii85_native.rb, line 51
def self.decode(input, force_delimiter=false)
  return "" if input.nil? || input.size == 0

  # Array slicing in ruby 3.0.1 appears to be constant time O(1): no performance hit based on array size.
  # No reason to implement this code segment in C if this holds true.
  if force_delimiter
    input = input[2..-3]
  else
    stream_start = find_stream_start(input)
    stream_end = find_stream_end(input)
    input = input[stream_start..stream_end] if stream_start != 0 || stream_end != -1
  end

  FFI::MemoryPointer.new(:char, input.size) do |in_char|
    in_char.write_string(input)
    out_size = self.a85_decoded_size(input.size)

    FFI::MemoryPointer.new(:uint8, out_size) do |output|
      self.a85_decode(in_char, input.size, output)
      return output.read_string()
    end
  end
end

# File lib/ascii85_native.rb, line 22
def self.encode(input, include_delimiter=false)
  if input.nil? || input.size == 0 
    return '<~~>' if include_delimiter
    return ''
  end

  if input.class == String
    input_data = []
    input.each_byte { |byte| input_data << byte }
  else
    input_data = input
  end

  FFI::MemoryPointer.new(:uint8, input_data.size) do |in_uint8|
    in_uint8.write_array_of_type(FFI::TYPE_UINT8, :put_uint8, input_data)
    out_size = self.a85_encoded_size(input_data.size, true)

    FFI::MemoryPointer.new(:uint8, out_size) do |output|
      self.a85_encode(in_uint8, input_data.size, output, true)
      if include_delimiter
        return '<~' + (output.read_string() || '') + '~>'
      else
        return output.read_string()
      end
    end
  end
end

# File lib/ascii85_native.rb, line 94
def self.find_stream_end(input)
  end_slice = -1
  cursor = -1

  input.size.times do |i|
    if ["\n", "\r", ' '].include?(input[cursor])
      cursor -= 1
      next
    elsif input[cursor] == '>' && input[cursor-1] == '~'
      end_slice = cursor - 2
      break
    else
      break # input is not delimited
    end
  end

  return end_slice
end

# File lib/ascii85_native.rb, line 75
def self.find_stream_start(input)
  start_slice = 0
  cursor = 0 

  input.size.times do |i|
    if ["\n", "\r", ' '].include?(input[cursor])
      cursor += 1
      next
    elsif input[cursor] == '<' && input[cursor+1] == '~'
      start_slice = cursor + 2
      break
    else
      break # input is not delimited
    end
  end

  return start_slice
end