class String
  def from_csv(sep = /,/)
    ret = [[]]
    c = chars
    quote = "\""
    comma = ","
    i = 0
    expecting_quote = false
    while i < c.length
      if c[i] == quote
        if ret[-1].empty? then expecting_quote = true
        elsif c[i+1] == quote then i += 1; ret[-1].push(quote)
        elsif expecting_quote and (c[i+1] == comma) then 
          ret.push([])
          expecting_quote = false
          i += 1
        elsif expecting_quote and (c[i+1] == nil) then 
          expecting_quote = false
        else
          raise "Invalid CSV Line (misplaced quote at #{i}; #{c[i+1]}): #{self}"
        end
      elsif c[i] == comma
        if expecting_quote
          ret[-1].push(comma)
        else
          ret.push([])
          expecting_quote = false
        end
      else
        ret[-1].push(c[i])
      end
      i += 1
    end
    ret.map { |col| col.join}
  end
end

class Array
  def from_csv
    self.map { |l| l.to_s.chomp.from_csv }
  end

  def to_csv(f)
    File.open(f, "w+") { |f| each { |row| f.puts(row.join(',')) }}
  end
end

class IO
  def from_csv(args = {})
    header = args.fetch(:header, false)
    separator = args.fetch(:separator, /,/)
    keys = readline.chomp.
              sub(/ *$/, "").sub(/^ */,"").
              from_csv(separator) if header;
    map { |l| l.to_s.chomp.from_csv(separator) }.
      map { |a| if header then keys.zip(a).to_h else a end }
  end
end

class File
  def File.csv(f, args = {})
    File.open(f) {|io| io.from_csv(args) }
  end
end