require 'csv'

class UsdaImporter

  ABBREV_COLUMNS = [
    'NDB_No',
    'Shrt_Desc',
    'Water',
    'Energ_Kcal',
    'Protein',
    'Lipid_Tot',
    'Ash',
    'Carbohydrt',
    'Fiber_TD',
    'Sugar_Tot',
    'Calcium',
    'Iron',
    'Magnesium',
    'Phosphorus',
    'Potassium',
    'Sodium',
    'Zinc',
    'Copper',
    'Manganese',
    'Selenium',
    'Vit_C',
    'Thiamin',
    'Riboflavin',
    'Niacin',
    'Panto_acid',
    'Vit_B6',
    'Folate_Tot',
    'Folic_acid',
    'Food_Folate',
    'Folate_DFE',
    'Choline_Tot',
    'Vit_B12',
    'Vit_A_IU',
    'Vit_A_RAE',
    'Retinol',
    'Alpha_Carot',
    'Beta_Carot',
    'Beta_Crypt',
    'Lycopene',
    'Lut+Zea',
    'Vit_E',
    'Vit_D_mcg',
    'Vit_D_IU',
    'Vit_K',
    'FA_Sat',
    'FA_Mono',
    'FA_Poly',
    'Cholestrl',
    'GmWt_1',
    'GmWt_Desc1',
    'GmWt_2',
    'GmWt_Desc2',
    'Refuse_Pct'
  ]
  
  FOOD_DATA_COLUMNS = [
      'NDB_No',
      'FdGrp_Cd',
      'Long_Desc',
      'Shrt_Desc',
      'ComName',
      'ManufacName',
      'Survey',
      'Ref_desc',
      'Refuse',
      'SciName',
      'N_Factor',
      'Pro_Factor',
      'Fat_Factor',
      'CHO_Factor'
  ]

  ABBREV_COLUMN_MAP = {
      ndbn: 'NDB_No',
      short_description: 'Shrt_Desc',
      water: 'Water',
      kcal: 'Energ_Kcal',
      protein: 'Protein',
      lipid: 'Lipid_Tot',
      ash: 'Ash',
      carbohydrates: 'Carbohydrt',
      fiber: 'Fiber_TD',
      sugar: 'Sugar_Tot',
      gram_weight_1: 'GmWt_1',
      gram_weight_2: 'GmWt_2',
      gram_weight_desc_1: 'GmWt_Desc1',
      gram_weight_desc_2: 'GmWt_Desc2',
      refuse_percent: 'Refuse_Pct'
  }

  FOOD_DATA_COLUMN_MAP = {
      scientific_name: 'SciName',
      refuse_description: 'Ref_desc',
      long_description: 'Long_Desc'
  }

  def initialize(directory)
    @directory = directory
  end

  def import

    UsdaFood.delete_all

    food_data_lookup = {}

    CSV.open(File.join(@directory, 'FOOD_DES.txt'), 'r:iso-8859-1:utf-8', csv_options(FOOD_DATA_COLUMNS)) do |csv|
      csv.each do |row|
        food_data_lookup[row['NDB_No']] = row.to_h
      end
    end

    CSV.open(File.join(@directory, 'ABBREV.txt'), 'r:iso-8859-1:utf-8', csv_options(ABBREV_COLUMNS)) do |csv|
      csv.each_slice(500) do |slice|
        UsdaFood.transaction do

          attributes = slice.map do |row|
            attrs = Hash[ABBREV_COLUMN_MAP.map { |db, col| [db, row[col]] }]
            lookup = food_data_lookup[attrs[:ndbn]]
            if lookup
              extra_attrs = Hash[FOOD_DATA_COLUMN_MAP.map { |db, col| [db, lookup[col]] }]
              attrs.merge!(extra_attrs)
            end
            attrs
          end

          UsdaFood.create(attributes)

        end
      end
    end

    usda_items = Hash[UsdaFood.where(ndbn: Ingredient.select(:ndbn)).map { |uf| [uf.ndbn, uf] }]

    Ingredient.where('ndbn IS NOT NULL').each do |i|
      item = usda_items[i.ndbn]

      if item
        i.set_usda_food(item)
        i.save
      end
    end

  end

  def csv_options(headers)
    { col_sep: '^', quote_char: '~', headers: headers }
  end

end