Class: EBNF::Writer

Inherits:
Object
  • Object
show all
Defined in:
lib/ebnf/writer.rb

Constant Summary collapse

LINE_LENGTH = 
80
LINE_LENGTH_HTML = 
200
ASCII_ESCAPE_NAMES =

ASCII escape names

[
"null",                 #x00
"start of heading",     #x01
"start of text",        #x02
"end of text",          #x03
"end of transmission",  #x04
"enquiry",              #x05
"acknowledge",          #x06
"bell",                 #x07
"backspace",            #x08
"horizontal tab",       #x09
"new line",             #x0A
"vertical tab",         #x0B
"form feed",            #x0C
"carriage return",      #x0D
"shift out",            #x0E
"shift in",             #x0F
"data link escape",     #x10
"device control 1",     #x11
"device control 2",     #x12
"device control 3",     #x13
"device control 4",     #x14
"negative acknowledge", #x15
"synchronous idle",     #x16
"end of trans. block",  #x17
"cancel",               #x18
"end of medium",        #x19
"substitute",           #x1A
"escape",               #x1B
"file separator",       #x1C
"group separator",      #x1D
"record separator",     #x1E
"unit separator",       #x1F
"space"                 #x20
]

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(rules, out: $stdout, html: false, format: :ebnf, validate: false, **options) ⇒ Writer

Returns a new instance of Writer.

Parameters:

  • rules (Array<Rule>)
  • format (:abnf, :ebnf, :isoebnf) (defaults to: :ebnf) —

    (:ebnf)

  • html (Boolean) (defaults to: false) —

    (false) generate HTML output

  • validate (Boolean) (defaults to: false) —

    (false) validate generated HTML.

  • options (Hash{Symbol => Object})
  • out (#write) (defaults to: $stdout) —

    ($stdout)



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# File 'lib/ebnf/writer.rb', line 106

def initialize(rules, out: $stdout, html: false, format: :ebnf, validate: false, **options)
  @options = options.merge(html: html)
  return if rules.empty?

  # Determine max LHS length
  format_meth = "format_#{format}".to_sym
  max_id = rules.max_by {|r| r.id.to_s.length}.id.to_s.length
  max_sym = rules.max_by {|r| r.sym.to_s.length}.sym.to_s.length
  lhs_length = max_sym + 1
  lhs_fmt = case format
  when :abnf    then "%<sym>-#{max_sym}s = "
  when :ebnf    then "%<sym>-#{max_sym}s ::= "
  when :isoebnf then "%<sym>-#{max_sym}s = "
  end
  if format == :ebnf && max_id > 0
    lhs_fmt = "%<id>-#{max_id+2}s " + lhs_fmt
    lhs_length += max_id + 3
  end
  rhs_length = (html ? LINE_LENGTH_HTML : LINE_LENGTH) - lhs_length

  if html
    # Output as formatted HTML
    begin
      require 'erubis'
      require 'htmlentities'
      @coder = HTMLEntities.new
      eruby = Erubis::Eruby.new(ERB_DESC)
      formatted_rules = rules.map do |rule|
        if rule.kind == :terminals || rule.kind == :pass
          OpenStruct.new(id: ("@#{rule.kind}"),
                         sym: nil,
                         assign: nil,
                         formatted: (
                           rule.kind == :terminals ?
                             "<strong># Productions for terminals</strong>" :
                             self.send(format_meth, rule.expr)))
        else
          formatted_expr = self.send(format_meth, rule.expr)
          # Measure text without markup
          formatted_expr_text = formatted_expr.gsub(%r{</?\w+[^>]*>}, '')
          if formatted_expr_text.length > rhs_length && (format != :abnf || rule.alt?)
            lines = []
            # Can only reasonably split apart alts
            self.send(format_meth, rule.expr, sep: "--rule-extensions--").
            split(/\s*--rule-extensions--\s*/).each_with_index do |formatted, ndx|
              assign = case format
              when :ebnf
                formatted.sub!(%r{\s*<code>\|</code>\s*}, '')
                (ndx > 0 ? (rule.alt? ? '|' : '') : '::=')
              when :abnf
                formatted.sub!(%r{\s*<code>/</code>\s*}, '')
                (ndx > 0 ? '=/' : '=')
              else
                formatted.sub!(%r{\s*<code>\|</code>\s*}, '')
                (ndx > 0 ? (rule.alt? ? '|' : '') : '=')
              end
              lines << OpenStruct.new(id: ((ndx == 0 ? "[#{rule.id}]" : "") if rule.id),
                                      sym: (rule.sym if ndx == 0 || format == :abnf),
                                      assign: assign,
                                      formatted: formatted)
            end
            if format == :isoebnf
              lines << OpenStruct.new(assign: ';')
            end
            lines
          else
            OpenStruct.new(id: ("[#{rule.id}]" if rule.id),
                           sym: rule.sym,
                           assign: (format == :ebnf ? '::=' : '='),
                           formatted: (formatted_expr + (format == :isoebnf ? ' ;' : '')))
          end
        end
      end.flatten

      html_result = eruby.evaluate(format: format, rules: formatted_rules)

      if validate
        begin
          # Validate the output HTML
          doc = Nokogiri::HTML5("<!DOCTYPE html>" + html_result, max_errors: 10)
          raise EncodingError, "Errors found in generated HTML:\n  " +
            doc.errors.map(&:to_s).join("\n  ") unless doc.errors.empty?
        rescue LoadError, NoMethodError
          # Skip
        end
      end

      out.write html_result
      return
    rescue LoadError
      $stderr.puts "Generating HTML requires erubis and htmlentities gems to be loaded"
    end
  end

  # Format each rule, considering the available rhs size
  rules.each do |rule|
    buffer = if rule.pass?
      "\n%-#{lhs_length-2}s      " % "@pass"
    elsif rule.kind == :terminals
      "\n%-#{lhs_length-2}s" % "@terminals"
    else
      lhs_fmt % {id: "[#{rule.id}]", sym: rule.sym}
    end
    formatted_expr = self.send(format_meth, rule.expr)
    if formatted_expr.length > rhs_length && (format != :abnf || rule.alt?)
      if format == :abnf
        # No whitespace, use =/
        self.send(format_meth, rule.expr, sep: "--rule-extensions--").
        split(/\s*--rule-extensions--\s*/).each_with_index do |formatted, ndx|
          if ndx > 0
            buffer << "\n" + lhs_fmt.sub('= ', '=/') % {id: "[#{rule.id}]", sym: rule.sym}
          end
          buffer << formatted.sub(/\s*\/\s*/, '')
        end
      else
        # Space out past "= "
        buffer << self.send(format_meth, rule.expr, sep: ("\n" + " " * (lhs_length + (rule.alt? ? 2 : 4) - (format == :ebnf ? 0 : 2))))
        buffer << ("\n" + " " * (lhs_length) + ';') if format == :isoebnf
      end
    else
      buffer << formatted_expr + (format == :isoebnf ? ' ;'  : '')
    end
    buffer << "\n\n" if [:terminals, :pass].include?(rule.kind)
    out.puts(buffer)
  end
end

Class Method Details

.html(*rules, format: :ebnf, validate: false) ⇒ Object

Write formatted rules to an IO like object as HTML

Parameters:

  • rules (Array<Rule>)
  • format (:abnf, :ebnf, :isoebnf) (defaults to: :ebnf) —

    (:ebnf)

  • validate (Boolean) (defaults to: false) —

    (false) validate generated HTML.

Returns:

  • (Object) 


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# File 'lib/ebnf/writer.rb', line 92

def self.html(*rules, format: :ebnf, validate: false)
  require 'stringio' unless defined?(StringIO)
  buf = StringIO.new
  Writer.new(rules, out: buf, html: true, format: format, validate: validate)
  buf.string
end

.print(*rules, format: :ebnf) ⇒ Object

Format rules to $stdout

Parameters:

  • rules (Array<Rule>)
  • format (:abnf, :ebnf, :isoebnf) (defaults to: :ebnf) —

    (:ebnf)

Returns:

  • (Object) 


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# File 'lib/ebnf/writer.rb', line 70

def self.print(*rules, format: :ebnf)
  write($stdout, *rules, format: format)
end

.string(*rules, format: :ebnf) ⇒ Object

Format rules to a String

Parameters:

  • rules (Array<Rule>)
  • format (:abnf, :ebnf, :isoebnf) (defaults to: :ebnf) —

    (:ebnf)

Returns:

  • (Object) 


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# File 'lib/ebnf/writer.rb', line 57

def self.string(*rules, format: :ebnf)
  require 'stringio' unless defined?(StringIO)
  buf = StringIO.new
  write(buf, *rules, format: format)
  buf.string
end

.write(out, *rules, format: :ebnf) ⇒ Object

Write formatted rules to an IO like object

Parameters:

  • out (Object)
  • rules (Array<Rule>)
  • format (:abnf, :ebnf, :isoebnf) (defaults to: :ebnf) —

    (:ebnf)

Returns:

  • (Object) 


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# File 'lib/ebnf/writer.rb', line 81

def self.write(out, *rules, format: :ebnf)
  Writer.new(rules, out: out, format: format)
end