# frozen_string_literal: true

module LCClasses
  class LCClass < Array
    # Convert nested LCClasses::CLASS_HASH to nested array.
    def self.nest(hash)
      return self[] if hash.nil?

      hash.sort { |a, b| a[0] <=> b[0] }.inject(self[]) do |result, klass|
        result << if klass[1][:subclasses]
                    self[klass[0], klass[1][:name], self.nest(klass[1][:subclasses])]
                  else
                    self[klass[0], klass[1][:name]]
                  end
      end
    end

    # Convert nested LCClasses::CLASS_HASH to flat array.
    def self.flatten(hash)
      return self[] if hash.nil?

      hash.sort { |a, b| a[0] <=> b[0] }.inject(self[]) do |result, klass|
        result << self[klass[0], klass[1][:name]]
        result + self.flatten(klass[1][:subclasses])
      end
    end

    # Return the subclasses of this class, if any.
    def subclasses
      class_data = LCClasses::CLASS_HASH[self[0]]
      return if class_data.nil? || class_data.empty?

      LCClasses::LCClass.nest(class_data[:subclasses])
    end

    # The class code.
    def code
      self[0]
    end

    # THe class name.
    def name
      self[1]
    end
  end

  # Library of Congress Main Classes and Subclasses
  CLASS_HASH = {
    'A' => {
      :name => 'General Works',
      :subclasses => {
        'AC'   => { :name => 'Collections; Series; Collected works' },
        'AE'   => { :name => 'Encyclopedias' },
        'AG'   => { :name => 'Dictionaries and other general reference works' },
        'AI'   => { :name => 'Indexes' },
        'AM'   => { :name => 'Museums. Collectors and collecting' },
        'AN'   => { :name => 'Newspapers' },
        'AP'   => { :name => 'Periodicals' },
        'AS'   => { :name => 'Academies and learned societies' },
        'AY'   => { :name => 'Yearbooks. Almanacs. Directories' },
        'AZ'   => { :name => 'History of scholarship and learning. The humanities' }
      }
    },
    'B' => {
      :name => 'Philosophy, Psychology, Religion',
      :subclasses => {
        'B'    => { :name => 'Philosophy (General)' },
        'BC'   => { :name => 'Logic' },
        'BD'   => { :name => 'Speculative philosophy' },
        'BF'   => { :name => 'Psychology' },
        'BH'   => { :name => 'Aesthetics' },
        'BJ'   => { :name => 'Ethics' },
        'BL'   => { :name => 'Religions; Mythology; Rationalism' },
        'BM'   => { :name => 'Judaism' },
        'BP'   => { :name => 'Islam; Bahaism; Theosophy, etc.' },
        'BQ'   => { :name => 'Buddhism' },
        'BR'   => { :name => 'Christianity' },
        'BS'   => { :name => 'The Bible' },
        'BT'   => { :name => 'Doctrinal Theology' },
        'BV'   => { :name => 'Practical Theology' },
        'BX'   => { :name => 'Christian Denominations' }
      }
    },
    'C' => {
      :name => 'Auxiliary Sciences of History (General)',
      :subclasses => {
        'CB'   => { :name => 'History of Civilization' },
        'CC'   => { :name => 'Archaeology' },
        'CD'   => { :name => 'Diplomatics. Archives. Seals' },
        'CE'   => { :name => 'Technical Chronology. Calendar' },
        'CJ'   => { :name => 'Numismatics' },
        'CN'   => { :name => 'Inscriptions. Epigraphy' },
        'CR'   => { :name => 'Heraldry' },
        'CS'   => { :name => 'Genealogy' },
        'CT'   => { :name => 'Biography' }
      }
    },
    'D' => {
      :name => 'World History and History of Europe, Asia, Africa, Australia, New Zealand, etc.',
      :subclasses => {
        'D'    => { :name => 'History (General)' },
        'DA'   => { :name => 'Great Britain' },
        'DAW'  => { :name => 'Central Europe' },
        'DB'   => { :name => 'Austria - Liechtenstein - Hungary - Czechoslovakia' },
        'DC'   => { :name => 'France - Andorra - Monaco' },
        'DD'   => { :name => 'Germany' },
        'DE'   => { :name => 'Greco-Roman World' },
        'DF'   => { :name => 'Greece' },
        'DG'   => { :name => 'Italy - Malta' },
        'DH'   => { :name => 'Low Countries - Benelux Countries' },
        'DJ'   => { :name => 'Netherlands (Holland)' },
        'DJK'  => { :name => 'Eastern Europe (General)' },
        'DK'   => { :name => 'Russia. Soviet Union. Former Soviet Republics - Poland' },
        'DL'   => { :name => 'Northern Europe. Scandinavia' },
        'DP'   => { :name => 'Spain - Portugal' },
        'DQ'   => { :name => 'Switzerland' },
        'DR'   => { :name => 'Balkan Peninsula' },
        'DS'   => { :name => 'Asia' },
        'DT'   => { :name => 'Africa' },
        'DU'   => { :name => 'Oceania (South Seas)' },
        'DX'   => { :name => 'Gypsies' }
      }
    },
    'E' => {
      :name => 'History of America, United States'
    },
    'F' => {
      :name => 'Local History of the United States and British, Dutch, French, and Latin America'
    },
    'G' => {
      :name => 'Geography, Anthropology, Recreation',
      :subclasses => {
        'G'  => { :name => 'Geography (General). Atlases. Maps' },
        'GA' => { :name => 'Mathematical geography. Cartography' },
        'GB' => { :name => 'Physical geography' },
        'GC' => { :name => 'Oceanography' },
        'GE' => { :name => 'Environmental Sciences' },
        'GF' => { :name => 'Human ecology. Anthropogeography' },
        'GN' => { :name => 'Anthropology' },
        'GR' => { :name => 'Folklore' },
        'GT' => { :name => 'Manners and customs (General)' },
        'GV' => { :name => 'Recreation. Leisure' }
      }
    },
    'H' => {
      :name => 'Social Sciences',
      :subclasses => {
        'H'  => { :name => 'Social sciences (General)' },
        'HA' => { :name => 'Statistics' },
        'HB' => { :name => 'Economic theory. Demography' },
        'HC' => { :name => 'Economic history and conditions' },
        'HD' => { :name => 'Industries. Land use. Labor' },
        'HE' => { :name => 'Transportation and communications' },
        'HF' => { :name => 'Commerce' },
        'HG' => { :name => 'Finance' },
        'HJ' => { :name => 'Public finance' },
        'HM' => { :name => 'Sociology (General)' },
        'HN' => { :name => 'Social history and conditions. Social problems. Social reform' },
        'HQ' => { :name => 'The family. Marriage. Women' },
        'HS' => { :name => 'Societies: secret, benevolent, etc.' },
        'HT' => { :name => 'Communities. Classes. Races' },
        'HV' => { :name => 'Social pathology. Social and public welfare. Criminology' },
        'HX' => { :name => 'Socialism. Communism. Anarchism' }
      }
    },
    'J' => {
      :name => 'Political Sciences',
      :subclasses => {
        'J'  => { :name => 'General legislative and executive papers' },
        'JA' => { :name => 'Political science (General)' },
        'JC' => { :name => 'Political theory' },
        'JF' => { :name => 'Political institutions and public administration' },
        'JJ' => { :name => 'Political institutions and public administration (North America)' },
        'JK' => { :name => 'Political institutions and public administration (United States)' },
        'JL' => { :name => 'Political institutions and public administration (Canada, Latin America, etc.)' },
        'JN' => { :name => 'Political institutions and public administration (Europe)' },
        'JQ' => { :name => 'Political institutions and public administration (Asia, Africa, Australia, Pacific Area, etc.)' },
        'JS' => { :name => 'Local government. Municipal government' },
        'JV' => { :name => 'Colonies and colonization. Emigration and immigration. International migration' },
        'JX' => { :name => 'International law, see JZ and KZ (obsolete)' },
        'JZ' => { :name => 'International relations' }
      }
    },
    'K' => {
      :name => 'Law',
      :subclasses => {
        'K'       => { :name => 'Law in general. Comparative and uniform law. Jurisprudence' },
        'KB'      => { :name => 'Religious law in general. Comparative religious law. Jurisprudence' },
        'KBM'     => { :name => 'Jewish law' },
        'KBP'     => { :name => 'Islamic law' },
        'KBR'     => { :name => 'History of canon law' },
        'KBU'     => { :name => 'Law of the Roman Catholic Church. The Holy See' },
        'KD-KDK'  => { :name => 'United Kingdom and Ireland' },
        'KDZ'     => { :name => 'America. North America' },
        'KE'      => { :name => 'Canada' },
        'KF'      => { :name => 'United States' },
        'KG'      => { :name => 'Latin America - Mexico and Central America - West Indies. Caribbean area' },
        'KH'      => { :name => 'South America' },
        'KJ-KKZ'  => { :name => 'Europe' },
        'KL-KWX'  => { :name => 'Asia and Eurasia, Africa, Pacific Area, and Antarctica' },
        'KZ'      => { :name => 'Law of nations' }
      }
    },
    'L' => {
      :name => 'Education',
      :subclasses => {
        'L'  => { :name => 'Education (General)' },
        'LA' => { :name => 'History of education' },
        'LB' => { :name => 'Theory and practice of education' },
        'LC' => { :name => 'Special aspects of education' },
        'LD' => { :name => 'Individual institutions - United States' },
        'LE' => { :name => 'Individual institutions - America (except United States)' },
        'LF' => { :name => 'Individual institutions - Europe' },
        'LG' => { :name => 'Individual institutions - Asia, Africa, Indian Ocean islands, Australia, New Zealand, Pacific islands' },
        'LH' => { :name => 'College and school magazines and papers' },
        'LJ' => { :name => 'Student fraternities and societies, United States' },
        'LT' => { :name => 'Textbooks' }
      }
    },
    'M' => {
      :name => 'Music',
      :subclasses => {
        'M'  => { :name => 'Music' },
        'ML' => { :name => 'Literature on music' },
        'MT' => { :name => 'Instruction and study' }
      }
    },
    'N' => {
      :name => 'Fine Arts',
      :subclasses => {
        'N'  => { :name => 'Visual arts' },
        'NA' => { :name => 'Architecture' },
        'NB' => { :name => 'Sculpture' },
        'NC' => { :name => 'Drawing. Design. Illustration' },
        'ND' => { :name => 'Painting' },
        'NE' => { :name => 'Print media' },
        'NK' => { :name => 'Decorative arts' },
        'NX' => { :name => 'Arts in general' }
      }
    },
    'P' => {
      :name => 'Language and Literature',
      :subclasses => {
        'P'  => { :name => 'Philology. Linguistics' },
        'PA' => { :name => 'Greek language and literature. Latin language and literature' },
        'PB' => { :name => 'Modern languages. Celtic languages' },
        'PC' => { :name => 'Romanic languages' },
        'PD' => { :name => 'Germanic languages. Scandinavian languages' },
        'PE' => { :name => 'English language' },
        'PF' => { :name => 'West Germanic languages' },
        'PG' => { :name => 'Slavic languages and literatures. Baltic languages. Albanian language' },
        'PH' => { :name => 'Uralic languages. Basque language' },
        'PJ' => { :name => 'Oriental languages and literatures' },
        'PK' => { :name => 'Indo-Iranian languages and literatures' },
        'PL' => { :name => 'Languages and literatures of Eastern Asia, Africa, Oceania' },
        'PM' => { :name => 'Hyperborean, Indian, and artificial languages' },
        'PN' => { :name => 'Literature (General)' },
        'PQ' => { :name => 'French literature - Italian literature - Spanish literature - Portuguese literature' },
        'PR' => { :name => 'English literature' },
        'PS' => { :name => 'American literature' },
        'PT' => { :name => 'Germanic, Scandinavian, and Icelandic literatures' },
        'PZ' => { :name => 'Fiction and juvenile belles lettres' }
      }
    },
    'Q' => {
      :name => 'Science',
      :subclasses => {
        'Q'  => { :name => 'Science (General)' },
        'QA' => { :name => 'Mathematics' },
        'QB' => { :name => 'Astronomy' },
        'QC' => { :name => 'Physics' },
        'QD' => { :name => 'Chemistry' },
        'QE' => { :name => 'Geology' },
        'QH' => { :name => 'Natural history - Biology' },
        'QK' => { :name => 'Botany' },
        'QL' => { :name => 'Zoology' },
        'QM' => { :name => 'Human anatomy' },
        'QP' => { :name => 'Physiology' },
        'QR' => { :name => 'Microbiology' }
      }
    },
    'R' => {
      :name => 'Medicine',
      :subclasses => {
        'R'  => { :name => 'Medicine (General)' },
        'RA' => { :name => 'Public aspects of medicine' },
        'RB' => { :name => 'Pathology' },
        'RC' => { :name => 'Internal medicine' },
        'RD' => { :name => 'Surgery' },
        'RE' => { :name => 'Ophthalmology' },
        'RF' => { :name => 'Otorhinolaryngology' },
        'RG' => { :name => 'Gynecology and obstetrics' },
        'RJ' => { :name => 'Pediatrics' },
        'RK' => { :name => 'Dentistry' },
        'RL' => { :name => 'Dermatology' },
        'RM' => { :name => 'Therapeutics. Pharmacology' },
        'RS' => { :name => 'Pharmacy and materia medica' },
        'RT' => { :name => 'Nursing' },
        'RV' => { :name => 'Botanic, Thomsonian, and eclectic medicine' },
        'RX' => { :name => 'Homeopathy' },
        'RZ' => { :name => 'Other systems of medicine' }
      }
    },
    'S' => {
      :name => 'Agriculture',
      :subclasses => {
        'S'  => { :name => 'Agriculture (General)' },
        'SB' => { :name => 'Plant culture' },
        'SD' => { :name => 'Forestry' },
        'SF' => { :name => 'Animal culture' },
        'SH' => { :name => 'Aquaculture. Fisheries. Angling' },
        'SK' => { :name => 'Hunting sports' }
      }
    },
    'T' => {
      :name => 'Technology',
      :subclasses => {
        'T'  => { :name => 'Technology (General)' },
        'TA' => { :name => 'Engineering (General). Civil engineering' },
        'TC' => { :name => 'Hydraulic engineering. Ocean engineering' },
        'TD' => { :name => 'Environmental technology. Sanitary engineering' },
        'TE' => { :name => 'Highway engineering. Roads and pavements' },
        'TF' => { :name => 'Railroad engineering and operation' },
        'TG' => { :name => 'Bridge engineering' },
        'TH' => { :name => 'Building construction' },
        'TJ' => { :name => 'Mechanical engineering and machinery' },
        'TK' => { :name => 'Electrical engineering. Electronics. Nuclear engineering' },
        'TL' => { :name => 'Motor vehicles. Aeronautics. Astronautics' },
        'TN' => { :name => 'Mining engineering. Metallurgy' },
        'TP' => { :name => 'Chemical technology' },
        'TR' => { :name => 'Photography' },
        'TS' => { :name => 'Manufactures' },
        'TT' => { :name => 'Handicrafts. Arts and crafts' },
        'TX' => { :name => 'Home economics' }
      }
    },
    'U' => {
      :name => 'Military Science',
      :subclasses => {
        'U'  => { :name => 'Military science (General)' },
        'UA' => { :name => 'Armies: Organization, distribution, military situation' },
        'UB' => { :name => 'Military administration' },
        'UC' => { :name => 'Maintenance and transportation' },
        'UD' => { :name => 'Infantry' },
        'UE' => { :name => 'Cavalry. Armor' },
        'UF' => { :name => 'Artillery' },
        'UG' => { :name => 'Military engineering. Air forces' },
        'UH' => { :name => 'Other services' }
      }
    },
    'V' => {
      :name => 'Naval Science',
      :subclasses => {
        'V'  => { :name => 'Naval science (General)' },
        'VA' => { :name => 'Navies: Organization, distribution, naval situation' },
        'VB' => { :name => 'Naval administration' },
        'VC' => { :name => 'Naval maintenance' },
        'VD' => { :name => 'Naval seamen' },
        'VE' => { :name => 'Marines' },
        'VF' => { :name => 'Naval ordnance' },
        'VG' => { :name => 'Minor services of navies' },
        'VK' => { :name => 'Navigation. Merchant marine' },
        'VM' => { :name => 'Naval architecture. Shipbuilding. Marine engineering' }
      }
    },
    'Z' => {
      :name => 'Bibliography, Library Science',
      :subclasses => {
        'Z'   => { :name => 'Books (General). Writing. Paleography. Book industries and trade. Libraries. Bibliography' },
        'ZA'  => { :name => 'Information resources (General)' }
      }
    }
  }.freeze

  # An array of main LC Classes.
  def self.main_classes
    CLASS_HASH.map do |k, v|
      LCClasses::LCClass[k, v[:name]]
    end.sort
  end

  # An array of all LC Subclasses.
  def self.subclasses
    self.main_classes.inject([]) do |result, main_class|
      result + main_class.subclasses
    end
  end

  # A nested array of main classes and subclasses.
  def self.nested
    LCClasses::LCClass.nest(LCClasses::CLASS_HASH)
  end

  # All main classes and subclasses in a flat array.
  def self.flat
    LCClasses::LCClass.flatten(LCClasses::CLASS_HASH)
  end

  def self.find_by_code(code)
    LCClasses.flat.detect { |i| i[0] == code.to_s }
  end

  # Find an main classe by code.
  def self.find_main_class_by_code(code)
    LCClasses.main_classes.detect { |i| i[0] == code.to_s }
  end

  # Find a subclass by code.
  def self.find_subclass_by_code(code)
    LCClasses.subclasses.detect { |i| i[0] == code.to_s }
  end

  # Find all main classes and subclass that match or start with a code or character.
  def self.find_all_by_code(code)
    LCClasses.flat.select { |i| i[0] if i[0] =~ /^#{code}[A-Z]?[A-Z]?/ }
  end
end