module Spreadsheetable

# File lib/spreadsheetable.rb, line 7
def self.extend_object(base)
  raise TypeError.new unless base.is_a?(ActiveRecord::Relation) || (base.is_a?(Array) && base.first.is_a?(ActiveRecord::Base))
  base.instance_variable_set(:@sheet_columns, [])
  super
end

# File lib/spreadsheetable.rb, line 13
def sheet_columns= cols
  raise TypeError unless cols.is_a?(Array)
  @sheet_columns = cols
end

# File lib/spreadsheetable.rb, line 18
def to_spreadsheet
  book = ::Spreadsheet::Workbook.new
  sheet = book.create_worksheet()

  rows = [_sheet_header]
  rows += self.collect{|_row| _to_row(_row)}
  rows.each_with_index do |_row, i|
    sheet.row(i).concat _row
  end

  tmpfile = Tempfile.new ["excel_tmp", ".xls"]
  book.write tmpfile

  tmpfile
end

# File lib/spreadsheetable.rb, line 34
def xls
  to_spreadsheet
end

# File lib/spreadsheetable.rb, line 38
def _sheet_header
  default = self.is_a?(ActiveRecord::Relation) ? self.klass : self.first.class

  self.sheet_columns.collect{|col|
    names = col.to_s.split(".")
    if names.count == 1
      model = default
    else
      model = names[names.count - 2].classify.constantize
    end
    model.human_attribute_name names.last
  }
end

# File lib/spreadsheetable.rb, line 52
def _to_row record
  self.sheet_columns.collect{|c|
    eval("record." + c) rescue nil
  }
end