require 'optparse'
require_relative '../n65'

module N65

  ####
  ##  This class handles the front end aspects,
  ##  parsing the commandline options and running the assembler
  class FrontEnd

    ####
    ##  Initialize with ARGV commandline
    def initialize(argv)
      @options = {output_file: nil, write_symbol_table: false, quiet: false}
      @argv = argv.dup
    end


    ####
    ##  Run the assembler
    def run
      ##  First use the option parser
      parser = create_option_parser
      parser.parse!(@argv)

      ##  Whatever is leftover in argv the input files
      if @argv.size.zero?
        STDERR.puts("No input files")
        exit(1)
      end

      ##  Only can assemble one file at once for now
      if @argv.size != 1
        STDERR.puts "Can only assemble one input file at once, but you can use .inc and .incbin directives"
        exit(1)
      end

      input_file = @argv.shift

      ##  Make sure the input file exists
      unless File.exists?(input_file)
        STDERR.puts "Input file #{input_file} does not exist"
        exit(1)
      end

      ##  Maybe they didn't provide an output file name, so we'll guess
      if @options[:output_file].nil?
        ext = File.extname(input_file)
        @options[:output_file] = input_file.gsub(ext, '') + '.nes'
      end

      if @options.values.any?(&:nil?)
        STDERR.puts "Missing options try --help"
        exit(1)
      end

      N65::Assembler.from_file(input_file, @options)
    end

    private

    ####
    ##  Create a commandline option parser
    def create_option_parser
      OptionParser.new do |opts|
        opts.banner = "Usage: #{$0} [options] <input_file.asm>"

        opts.on('-o', '--outfile filename', 'outfile') do |output_file|
          @options[:output_file] = output_file;
        end

        opts.on('-s', '--symbols', 'Outputs a symbol map') do
          @options[:write_symbol_table] = true
        end

        opts.on('-q', '--quiet', 'No output on success') do
          @options[:quiet] = true
        end

        opts.on('-v', '--version', 'Displays Version') do
          puts "N65 Assembler Version #{N65::VERSION}"
          exit
        end

        opts.on('-h', '--help', 'Displays Help') do
          puts opts
          exit
        end


      end
    end

  end

end