Super simple date parser

gistfile1.rb

# Toggle the comments below to switch between American/rational date parsing
require 'american_date'
require 'active_support/core_ext'
# require 'date'

class SimpleDates

  def self.parse(mystring)
    mystring = mystring.to_s.downcase.strip
    # Date._parse likes '/' better than '-', I guess?
    mystring_rp = mystring.gsub("-","/")
    result = single_year(mystring)     || 
    circa_dates(mystring)     ||
    seasons(mystring)         ||
    decades_et_al(mystring)   ||
    date_ranges(mystring)     ||
    random_punc(mystring)     ||
    rdate_parse(mystring_rp)
    return result.blank? ? "n.d." : result
  end


  private  
  class << self
  
    SEPARATORS = /[\/\-,\.\s]+/
    def single_year(mystring)
      mystring[/^\d{4}$/]    
    end
    
    # & re-parse
    def circa_dates(mystring)
      mystring.match(/([^a-zA-Z]{1}|^)(?<ext>[cC]\.?[aA]?([^b-zB-Z]{1}|$))/).tap do |mymatch|
        unless mymatch.nil?
          match_inside = parse(mystring.gsub(mymatch[:ext].to_s, ""))
          return "c. " + match_inside unless match_inside.nil?
        end
      end
    end
    
    # & reparse
    def seasons(mystring)
      mah_seasons = [/[Ss]pring/, /[Ss]pr/, /[Ss]ummer/, /[Ss]um/, /[Ff]all/, /[Aa]utumn/, /[Ww]inter/, /[Ww]in/, /[Ee]arly/, /[Ll]ate/ ]
      unless mah_seasons.map{|x| mystring.match(x) }.compact.empty? 
        mah_seasons.each {|x| mystring.gsub!(x,"") }
        return parse(mystring)
      end
      return nil
    end
 
    
    # & reparse
    def decades_et_al(mystring)
      # whole decades
      return mystring.gsub("'","") if mystring.match(/\d'?s$/)
      if mystring.match(/([^\d]|^)(\d{3})\-\?/)
        return "#{mystring.match(/([^\d]|^)(\d{3})\-\?/)[2]}0s?"
      end
      if mystring.match(/([^\d]|^)(\d{3})\?/)
        return "#{mystring.match(/([^\d]|^)(\d{3})\?/)[2]}0s?"
      end
      # uncertain
      mystring.match(/\s?\(?\s?\?\s?\)?\s?/).tap do |mymatch|
        mystring.gsub(mymatch.to_s, "").tap do |mysub|
          return parse(mysub) + "?" unless mymatch.nil?
        end
      end
    end
    
    def date_ranges(mystring)
      mystring.split(SEPARATORS).tap do |a| 
        return mystring if a.select{|x| x.to_i > 12 }.length > 2
        return mystring if a.select{|x| x.to_i > 31 }.length > 1
      end
      nil
    end
    
    def no_date(mystring)
      mystring.match(/^n\.?\s?d\.?\s?$|[Uu]ndated|[Uu]nknown|[Nn]o\s[Dd]ate/).tap do |o|
        return "n.d." unless o.nil?
      end
    end
    
    # & reparse
    def random_punc(mystring)
      mystring.match(/^\s*[\/\-,\.]+/).tap do |mymatch|
        return parse(mystring.gsub(mymatch.to_s,"")) unless mymatch.nil?        
      end
      mystring.match(/[\/\-,\.]+\s*$/).tap do |mymatch|
        return parse(mystring.gsub(mymatch.to_s,"")) unless mymatch.nil?        
      end
    end    
    # Date._parse is doing almost all the work....
    def rdate_parse(mystring_rp)
      Date._parse(mystring_rp).tap do |a| 
        [ a[:year], "%02d" % a[:mon].to_i, "%02d" % a[:mday].to_i ].tap do |x|
          return x.select{|y| y.to_i > 0 }.compact.join("-")
        end
      end
      nil
    end
    
  end

end


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