# encoding: UTF-8
module Axlsx

  # The Shared String Table class is responsible for managing and serializing common strings in a workbook.
  # While the ECMA-376 spec allows for both inline and shared strings it seems that at least some applications like iWorks Numbers
  # and Google Docs require that the shared string table is populated in order to interoperate properly.
  # As a developer, you should never need to directly work against this class. Simply set 'use_shared_strings'
  # on the package or workbook to generate a package that uses the shared strings table instead of inline strings.
  # @note Serialization performance is affected by using this serialization method so if you do not need interoperability
  # it is recomended that you use the default inline string method of serialization.
  class SharedStringsTable

    # The total number of strings in the workbook including duplicates
    # Empty cells are treated as blank strings
    # @return [Integer]
    attr_reader :count

    # The total number of unique strings in the workbook.
    # @return [Integer]
    def unique_count
      @unique_cells.size
    end

    # An array of unique cells. Multiple attributes of the cell are used in comparison
    # each of these unique cells is parsed into the shared string table.
    # @see Cell#sharable
    attr_reader :unique_cells

    # The xml:space attribute
    # @see Workbook#xml_space
    attr_reader :xml_space

    # Creates a new Shared Strings Table agains an array of cells
    # @param [Array] cells This is an array of all of the cells in the workbook
    # @param [Symbol] xml_space The xml:space behavior for the shared string table.
    def initialize(cells, xml_space=:preserve)
      @index = 0
      @xml_space = xml_space
      @unique_cells = {}
      @shared_xml_string = ""
      shareable_cells = cells.flatten.select{ |cell| cell.plain_string? }
      @count = shareable_cells.size
      resolve(shareable_cells)
    end

    # Serializes the object
    # @param [String] str
    # @return [String]
    def to_xml_string(str='')
      str << '<?xml version="1.0" encoding="UTF-8"?><sst xmlns="' << XML_NS << '"'
      str << ' count="' << @count.to_s << '" uniqueCount="' << unique_count.to_s << '"'
      str << ' xml:space="' << xml_space.to_s << '">' << @shared_xml_string << '</sst>'
      str = Axlsx::sanitize(str)
    end

    private

    # Interate over all of the cells in the array.
    # if our unique cells array does not contain a sharable cell,
    # add the cell to our unique cells array and set the ssti attribute on the index of this cell in the shared strings table
    # if a sharable cell already exists in our unique_cells array, set the ssti attribute of the cell and move on.
    # @return [Array] unique cells
    def resolve(cells)
      cells.each do |cell|
        cell_hash = cell.value
        if index = @unique_cells[cell_hash]
          cell.send :ssti=, index
        else
          cell.send :ssti=, @index
          @shared_xml_string << '<si>' << CellSerializer.run_xml_string(cell) << '</si>'
          @unique_cells[cell_hash] = @index
          @index += 1
        end
      end
    end
  end
end