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Filename : row.rb
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# frozen_string_literal: true

require "forwardable"

class CSV
  #
  # A CSV::Row is part Array and part Hash. It retains an order for the fields
  # and allows duplicates just as an Array would, but also allows you to access
  # fields by name just as you could if they were in a Hash.
  #
  # All rows returned by CSV will be constructed from this class, if header row
  # processing is activated.
  #
  class Row
    #
    # Constructs a new CSV::Row from +headers+ and +fields+, which are expected
    # to be Arrays. If one Array is shorter than the other, it will be padded
    # with +nil+ objects.
    #
    # The optional +header_row+ parameter can be set to +true+ to indicate, via
    # CSV::Row.header_row?() and CSV::Row.field_row?(), that this is a header
    # row. Otherwise, the row assumes to be a field row.
    #
    # A CSV::Row object supports the following Array methods through delegation:
    #
    # * empty?()
    # * length()
    # * size()
    #
    def initialize(headers, fields, header_row = false)
      @header_row = header_row
      headers.each { |h| h.freeze if h.is_a? String }

      # handle extra headers or fields
      @row = if headers.size >= fields.size
        headers.zip(fields)
      else
        fields.zip(headers).each(&:reverse!)
      end
    end

    # Internal data format used to compare equality.
    attr_reader :row
    protected   :row

    ### Array Delegation ###

    extend Forwardable
    def_delegators :@row, :empty?, :length, :size

    def initialize_copy(other)
      super
      @row = @row.dup
    end

    # Returns +true+ if this is a header row.
    def header_row?
      @header_row
    end

    # Returns +true+ if this is a field row.
    def field_row?
      not header_row?
    end

    # Returns the headers of this row.
    def headers
      @row.map(&:first)
    end

    #
    # :call-seq:
    #   field( header )
    #   field( header, offset )
    #   field( index )
    #
    # This method will return the field value by +header+ or +index+. If a field
    # is not found, +nil+ is returned.
    #
    # When provided, +offset+ ensures that a header match occurs on or later
    # than the +offset+ index. You can use this to find duplicate headers,
    # without resorting to hard-coding exact indices.
    #
    def field(header_or_index, minimum_index = 0)
      # locate the pair
      finder = (header_or_index.is_a?(Integer) || header_or_index.is_a?(Range)) ? :[] : :assoc
      pair   = @row[minimum_index..-1].send(finder, header_or_index)

      # return the field if we have a pair
      if pair.nil?
        nil
      else
        header_or_index.is_a?(Range) ? pair.map(&:last) : pair.last
      end
    end
    alias_method :[], :field

    #
    # :call-seq:
    #   fetch( header )
    #   fetch( header ) { |row| ... }
    #   fetch( header, default )
    #
    # This method will fetch the field value by +header+. It has the same
    # behavior as Hash#fetch: if there is a field with the given +header+, its
    # value is returned. Otherwise, if a block is given, it is yielded the
    # +header+ and its result is returned; if a +default+ is given as the
    # second argument, it is returned; otherwise a KeyError is raised.
    #
    def fetch(header, *varargs)
      raise ArgumentError, "Too many arguments" if varargs.length > 1
      pair = @row.assoc(header)
      if pair
        pair.last
      else
        if block_given?
          yield header
        elsif varargs.empty?
          raise KeyError, "key not found: #{header}"
        else
          varargs.first
        end
      end
    end

    # Returns +true+ if there is a field with the given +header+.
    def has_key?(header)
      !!@row.assoc(header)
    end
    alias_method :include?, :has_key?
    alias_method :key?,     :has_key?
    alias_method :member?,  :has_key?
    alias_method :header?,  :has_key?

    #
    # :call-seq:
    #   []=( header, value )
    #   []=( header, offset, value )
    #   []=( index, value )
    #
    # Looks up the field by the semantics described in CSV::Row.field() and
    # assigns the +value+.
    #
    # Assigning past the end of the row with an index will set all pairs between
    # to <tt>[nil, nil]</tt>. Assigning to an unused header appends the new
    # pair.
    #
    def []=(*args)
      value = args.pop

      if args.first.is_a? Integer
        if @row[args.first].nil?  # extending past the end with index
          @row[args.first] = [nil, value]
          @row.map! { |pair| pair.nil? ? [nil, nil] : pair }
        else                      # normal index assignment
          @row[args.first][1] = value
        end
      else
        index = index(*args)
        if index.nil?             # appending a field
          self << [args.first, value]
        else                      # normal header assignment
          @row[index][1] = value
        end
      end
    end

    #
    # :call-seq:
    #   <<( field )
    #   <<( header_and_field_array )
    #   <<( header_and_field_hash )
    #
    # If a two-element Array is provided, it is assumed to be a header and field
    # and the pair is appended. A Hash works the same way with the key being
    # the header and the value being the field. Anything else is assumed to be
    # a lone field which is appended with a +nil+ header.
    #
    # This method returns the row for chaining.
    #
    def <<(arg)
      if arg.is_a?(Array) and arg.size == 2  # appending a header and name
        @row << arg
      elsif arg.is_a?(Hash)                  # append header and name pairs
        arg.each { |pair| @row << pair }
      else                                   # append field value
        @row << [nil, arg]
      end

      self  # for chaining
    end

    #
    # A shortcut for appending multiple fields. Equivalent to:
    #
    #   args.each { |arg| csv_row << arg }
    #
    # This method returns the row for chaining.
    #
    def push(*args)
      args.each { |arg| self << arg }

      self  # for chaining
    end

    #
    # :call-seq:
    #   delete( header )
    #   delete( header, offset )
    #   delete( index )
    #
    # Removes a pair from the row by +header+ or +index+. The pair is
    # located as described in CSV::Row.field(). The deleted pair is returned,
    # or +nil+ if a pair could not be found.
    #
    def delete(header_or_index, minimum_index = 0)
      if header_or_index.is_a? Integer                 # by index
        @row.delete_at(header_or_index)
      elsif i = index(header_or_index, minimum_index)  # by header
        @row.delete_at(i)
      else
        [ ]
      end
    end

    #
    # The provided +block+ is passed a header and field for each pair in the row
    # and expected to return +true+ or +false+, depending on whether the pair
    # should be deleted.
    #
    # This method returns the row for chaining.
    #
    # If no block is given, an Enumerator is returned.
    #
    def delete_if(&block)
      return enum_for(__method__) { size } unless block_given?

      @row.delete_if(&block)

      self  # for chaining
    end

    #
    # This method accepts any number of arguments which can be headers, indices,
    # Ranges of either, or two-element Arrays containing a header and offset.
    # Each argument will be replaced with a field lookup as described in
    # CSV::Row.field().
    #
    # If called with no arguments, all fields are returned.
    #
    def fields(*headers_and_or_indices)
      if headers_and_or_indices.empty?  # return all fields--no arguments
        @row.map(&:last)
      else                              # or work like values_at()
        all = []
        headers_and_or_indices.each do |h_or_i|
          if h_or_i.is_a? Range
            index_begin = h_or_i.begin.is_a?(Integer) ? h_or_i.begin :
                                                        index(h_or_i.begin)
            index_end   = h_or_i.end.is_a?(Integer)   ? h_or_i.end :
                                                        index(h_or_i.end)
            new_range   = h_or_i.exclude_end? ? (index_begin...index_end) :
                                                (index_begin..index_end)
            all.concat(fields.values_at(new_range))
          else
            all << field(*Array(h_or_i))
          end
        end
        return all
      end
    end
    alias_method :values_at, :fields

    #
    # :call-seq:
    #   index( header )
    #   index( header, offset )
    #
    # This method will return the index of a field with the provided +header+.
    # The +offset+ can be used to locate duplicate header names, as described in
    # CSV::Row.field().
    #
    def index(header, minimum_index = 0)
      # find the pair
      index = headers[minimum_index..-1].index(header)
      # return the index at the right offset, if we found one
      index.nil? ? nil : index + minimum_index
    end

    #
    # Returns +true+ if +data+ matches a field in this row, and +false+
    # otherwise.
    #
    def field?(data)
      fields.include? data
    end

    include Enumerable

    #
    # Yields each pair of the row as header and field tuples (much like
    # iterating over a Hash). This method returns the row for chaining.
    #
    # If no block is given, an Enumerator is returned.
    #
    # Support for Enumerable.
    #
    def each(&block)
      return enum_for(__method__) { size } unless block_given?

      @row.each(&block)

      self  # for chaining
    end

    alias_method :each_pair, :each

    #
    # Returns +true+ if this row contains the same headers and fields in the
    # same order as +other+.
    #
    def ==(other)
      return @row == other.row if other.is_a? CSV::Row
      @row == other
    end

    #
    # Collapses the row into a simple Hash. Be warned that this discards field
    # order and clobbers duplicate fields.
    #
    def to_h
      hash = {}
      each do |key, _value|
        hash[key] = self[key] unless hash.key?(key)
      end
      hash
    end
    alias_method :to_hash, :to_h

    alias_method :to_ary, :to_a

    #
    # Returns the row as a CSV String. Headers are not used. Equivalent to:
    #
    #   csv_row.fields.to_csv( options )
    #
    def to_csv(**options)
      fields.to_csv(**options)
    end
    alias_method :to_s, :to_csv

    #
    # Extracts the nested value specified by the sequence of +index+ or +header+ objects by calling dig at each step,
    # returning nil if any intermediate step is nil.
    #
    def dig(index_or_header, *indexes)
      value = field(index_or_header)
      if value.nil?
        nil
      elsif indexes.empty?
        value
      else
        unless value.respond_to?(:dig)
          raise TypeError, "#{value.class} does not have \#dig method"
        end
        value.dig(*indexes)
      end
    end

    #
    # A summary of fields, by header, in an ASCII compatible String.
    #
    def inspect
      str = ["#<", self.class.to_s]
      each do |header, field|
        str << " " << (header.is_a?(Symbol) ? header.to_s : header.inspect) <<
               ":" << field.inspect
      end
      str << ">"
      begin
        str.join('')
      rescue  # any encoding error
        str.map do |s|
          e = Encoding::Converter.asciicompat_encoding(s.encoding)
          e ? s.encode(e) : s.force_encoding("ASCII-8BIT")
        end.join('')
      end
    end
  end
end