require 'erb'
require 'ostruct'

module Semi
  class Driver

    def initialize(path)
      @config = Semi::Config.new(path)
    end

    def start(args)
      # Initialize the dictionary with the defaults
      @dictionary = {}
      @config.defaults.each_pair do |name,val|
        hints = @config.validators[name] || nil
        @dictionary[name.downcase] = Semi::Variable.import(val, hints)
      end

      # Now manually merge in the env vars
      ENV.each_pair do |name, val|
        hints = @config.validators[name] || nil
        @dictionary[name.downcase] = Semi::Variable.import(val, hints)
      end

      # Now that all values should be present in @dictionary, do any expansions
      @dictionary.each_pair do |name, val|
        @dictionary[name] = Semi::Variable.expand(val, @dictionary)
      end

      # Check any validations being asserted
      @config.validators.each_key { |key|
        begin
          Semi::validate(@dictionary[key.downcase], @config.validators[key])
        rescue Semi::ValidationError => err
          if @dictionary.include? key
            puts "Can not validate #{key}: #{err}"
          elsif @config.validators[key].include? 'required'
            puts "#{key} is a required value, but it was not found."
            exit(5)
          end
        end
      }

      # prepare the dictionary for the templates
      @dictionary = OpenStruct.new(@dictionary)

      # Process the config files and generate final versions
      begin
        @config.files.each do |file|
          # Read the template file and render
          @config.process_file(file, @dictionary)
        end
      rescue NoMethodError
        puts "files key in semi.conf does not contain an array of files."
        exit (6)
      end

      # Replace ENV with @dictionary
      @dictionary.each_pair {|k,v| ENV[k.to_s] = v.to_s}

      # Check for pre-defined commands
      if ENV['SEMI_DEBUG']
        puts "Semi debug:: args = #{args.inspect}"
      end
      if args.count == 0 and @config.commands.include? 'default'
        args = @config.commands['default']
      elsif args.count == 1 and args[0] == 'help'
        puts "This container also supports the following commands:"
        puts""
        printf("  %-10s||   %s\n", 'Command', 'Actual command run / description')
        puts "---------------------------------------------------------------"
        @config.commands.each_pair do |cmd, cmd_line|
          printf("  %-10s   => %s\n", cmd, cmd_line)
        end
        printf("  %-10s   => %s\n", 'help', 'List shortcut and additional commands')
        exit(0)
      elsif @config.commands.include? args[0]
        args = [@config.commands[args[0]], args[1..-1]].flatten
      end

      # Execute the command line
      if ENV['SEMI_DEBUG']
        puts "Semi debug:: executing: #{args}"
      end
      begin
        exec([args].flatten.join(' '))
      rescue SystemCallError => e
        if e.errno == Errno::ENOENT
          puts "Command not found: executing: #{args}"
        else
          puts "Unknown system call failure: #{e.inspect}"
        end
        exit(e.errno)
      rescue Exception => e
        puts "Unknown exception: #{e.inspect}"
        exit(99)
      end
    end

  end
end