class Convertor
  def initialize(input_filename, force_overwrite)
    @input_filename = input_filename
    @force_overwrite = force_overwrite
    @input_data = []
  end

  def convert!
    puts "Processing file #{@input_filename}"
    read_in_data
    split_comments!
    parse_header_attributes
    convert_from_string!
    strip_invalid!
    convert_fluxes_to_magnitudes!
    center_mag_on_zero!
    save!
    puts "Finished processing file #{@input_filename}"
  end

  private

    def read_in_data
      File.new(@input_filename, "r").each { |line| @input_data << line }
      #file closes automatically because it's opened in this method
      raise NoDataError if @input_data.empty?
    end

    def split_comments!
      @comments, @input_data = @input_data.partition { |line| line =~ /^#/ }
    end

    def convert_from_string!
      @input_data.map! { |line| line.split(" ").map(&:to_f)[0..1] }
    end

    def strip_invalid!
      @input_data.delete_if { |record| record[1] == 0.0 }
    end

    def convert_fluxes_to_magnitudes!
      @input_data.each { |record| record[1] = -2.5 * Math.log10(record[1]) }
    end

    def average_mag
      @input_data.map { |record| record[1] }.inject(:+).to_f / @input_data.size
    end

    def center_mag_on_zero!
      average = average_mag
      @input_data.each { |record| record[1] -= average }
    end

    def output_filename
      # Determine the output filename from header
      "kic#{@attributes[:kic_number]}_#{@attributes[:season]}_#{@input_filename.split("_")[1]}.txt"
    end

    def parse_header_attributes
      @attributes = @comments.select { |line| line.include? ":" }.map { |line| line.gsub("# ", "").split ":" }.to_hash
    end

    def save!
      raise FileExistsError if File.exist?(output_filename) && !@force_overwrite
      output_file = File.new output_filename, "a+"
      output_file.truncate(0) if @force_overwrite
      @input_data.each { |record| output_file << "#{record.join("\t")}\n" }
    end
end

class Array
  def to_hash
    self.inject({}) { |hash_version, element| hash_version[element[0].downcase.gsub(" ", "_").to_sym] = element[1].gsub(" ", "").strip; hash_version }
  end
end

class FileExistsError < StandardError; end
class NoDataError < StandardError; end

Kernel.abort "Please pass the input filename as an argument! Use -f to force overwrite." if ARGV.size < 1 #aborts the execution if no filename is provided as an argument with the program call

force_overwrite = false

if ARGV.first == "-f"
  force_overwrite = true
  ARGV.delete_at 0
end

ARGV.each do |filename|
  begin
    Convertor.new(filename, force_overwrite).convert!
  rescue FileExistsError
    puts "Your output file (#{filename}) already exists, please remove it first (or something)."
  end
end