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
]
ERB_DESC =
%q(
  <table class="grammar">
    <tbody id="grammar-productions" class="<%= @format %>">
      <% for rule in @rules %>
      <tr<%= %{ id="grammar-production-#{rule.sym}"} unless %w(=/ |).include?(rule.assign) || rule.sym.nil?%>>
        <% if rule.id %>
        <td<%= " colspan=2" unless rule.sym %>><%= rule.id %></td>
        <% end %>
        <% if rule.sym %>
        <td><code><%== rule.sym %></code></td>
        <% end %>
        <td><%= rule.assign %></td>
        <td><%= rule.formatted %></td>
      </tr>
      <% end %>
    </tbody>
  </table>
).gsub(/^      /, '')

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
          require 'nokogumbo'
          # 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
          # 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

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

Instance Method Details

#escape_abnf_hex(u) ⇒ Object (protected)


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# File 'lib/ebnf/writer.rb', line 550

def escape_abnf_hex(u)
  fmt = case u.ord
  when 0x0000..0x00ff then "%02X"
  when 0x0100..0xffff then "%04X"
  else                     "%08X"
  end
  char =  "%x" + (fmt % u.ord)
  if @options[:html]
    if u.ord <= 0x20
      char = %(<abbr title="#{ASCII_ESCAPE_NAMES[u.ord]}">#{@coder.encode char}</abbr>)
    elsif u.ord == 0x22
      %(<abbr title="quot">>&quot;</abbr>)
    elsif u.ord < 0x7F
      char = %(<abbr title="ascii '#{u}'">#{@coder.encode char}</abbr>)
    elsif u.ord == 0x7F
      char = %(<abbr title="delete">#{@coder.encode char}</abbr>)
    elsif u.ord <= 0xFF
      char = %(<abbr title="extended ascii '#{u}'">#{char}</abbr>)
    else
      char = %(<abbr title="unicode '#{u.unicode_normaliz}'">#{char}</abbr>)
    end
    %(<code class="grammar-char-escape">#{char}</code>)
  else
    char
  end
end

#escape_ebnf_hex(u) ⇒ Object (protected)


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# File 'lib/ebnf/writer.rb', line 358

def escape_ebnf_hex(u)
  fmt = case u.ord
  when 0x00..0x20     then "#x%02X"
  when 0x0000..0x00ff then "#x%02X"
  when 0x0100..0xffff then "#x%04X"
  else                     "#x%08X"
  end
  char = fmt % u.ord
  if @options[:html]
    char = if u.ord <= 0x20
      %(<abbr title="#{ASCII_ESCAPE_NAMES[u.ord]}">#{@coder.encode char}</abbr>)
    elsif u.ord == 0x22
      %(<abbr title="quot">>&quot;</abbr>)
    elsif u.ord < 0x7F
      %(<abbr title="ascii '#{@coder.encode u}'">#{@coder.encode char}</abbr>)
    elsif u.ord == 0x7F
      %(<abbr title="delete">#{@coder.encode char}</abbr>)
    elsif u.ord <= 0xFF
      %(<abbr title="extended ascii '#{@coder.encode char}'">#{char}</abbr>)
    elsif (%w(Control Private-use Surrogate Noncharacter Reserved) - ::Unicode::Types.of(u)).empty?
      %(<abbr title="unicode '#{u}'">#{char}</abbr>)
    else
      %(<abbr title="unicode '#{::Unicode::Types.of(u).first}'">#{char}</abbr>)
    end
    %(<code class="grammar-char-escape">#{char}</code>)
  else
    char
  end
end

#format_abnf(expr, sep: nil, embedded: false, sensitive: true) ⇒ Object (protected)

Format the expression part of a rule


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# File 'lib/ebnf/writer.rb', line 393

def format_abnf(expr, sep: nil, embedded: false, sensitive: true)
  return (@options[:html] ? %(<a href="#grammar-production-#{@coder.encode expr}">#{@coder.encode expr}</a>) : expr.to_s) if expr.is_a?(Symbol)
  if expr.is_a?(String)
    if expr.length == 1
      return format_abnf_char(expr)
    elsif expr.start_with?('%')
      # Already encoded
      return expr
    elsif expr =~ /"/
      # Split into segments
      segments = expr.split('"')

      return format_abnf_char(expr) if segments.empty?

      seq = segments.inject([]) {|memo, s| memo.concat([[:hex, "#x22"], s])}[1..-1]
      seq.unshift(:seq)
      return format_abnf(seq, sep: nil, embedded: false)
    else
      return (@options[:html] ? %("<code class="grammar-literal">#{'%s' if sensitive}#{@coder.encode expr}</code>") : %(#{'%s' if sensitive}"#{expr}"))
    end
  end
  parts = {
    alt:    (@options[:html] ? "<code>/</code> " : "/ "),
    star:   (@options[:html] ? "<code>*</code> " : "*"),
    plus:   (@options[:html] ? "<code>+</code> " : "1*"),
    opt:    (@options[:html] ? "<code>?</code> " : "?")
  }
  lbrac = (@options[:html] ? "<code>[</code> " : "[")
  rbrac = (@options[:html] ? "<code>]</code> " : "]")
  lparen = (@options[:html] ? "<code>(</code> " : "(")
  rparen = (@options[:html] ? "<code>)</code> " : ")")

  case expr.first
  when :istr
    # FIXME: if string part is segmented, need to do something different
    format_abnf(expr.last, embedded: true, sensitive: false)
  when :alt
    this_sep = (sep ? sep : " ") + parts[expr.first.to_sym]
    res = expr[1..-1].map {|e| format_abnf(e, embedded: true)}.join(this_sep)
    embedded ? (lparen + res + rparen) : res
  when :diff
    raise RangeError, "ABNF does not support the diff operator"
  when :opt
    char = parts[expr.first.to_sym]
    r = format_abnf(expr[1], embedded: true)
    "#{lbrac}#{r}#{rbrac}"
  when :plus, :star
    char = parts[expr.first.to_sym]
    r = format_abnf(expr[1], embedded: true)
    "#{char}#{r}"
  when :hex
    escape_abnf_hex(expr.last[2..-1].hex.chr)
  when :range
    # Returns an [:alt] or [:not [:alt]] if composed of multiple sequences
    # Note: ABNF does not support the `not` operator
    res = format_abnf_range(expr.last)
    res.is_a?(Array) ?
      format_abnf(res, embedded: true) :
      res
  when :seq
    this_sep = (sep ? sep : " ")
    res = expr[1..-1].map do |e|
      format_abnf(e, embedded: true)
    end.join(this_sep)
    embedded ? (lparen + res + rparen) : res
  when :rept
    # Expand repetition
    min, max, value = expr[1..-1]
    r = format_abnf(value, embedded: true)
    if min == max
      "#{min}#{r}"
    elsif min == 0 && max == '*'
      "#{parts[:star]}#{r}"
    elsif min > 0 && max == '*'
      "#{min}#{parts[:star]}#{r}"
    else
      "#{min}#{parts[:star]}#{max}#{r}"
    end
  else
    raise "Unknown operator: #{expr.first}"
  end
end

#format_abnf_char(c) ⇒ Object (protected)

Format a single-character string, prefering hex for non-main ASCII


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# File 'lib/ebnf/writer.rb', line 477

def format_abnf_char(c)
  if /[\x20-\x21\x23-\x7E]/.match?(c)
    @options[:html] ? %("<code class="grammar-literal">#{@coder.encode c}</code>") : c.inspect
  else
    escape_abnf_hex(c)
  end
end

#format_abnf_range(string) ⇒ Object (protected)

Format a range

Presumes range has already been validated

Raises:

  • (RangeError)

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# File 'lib/ebnf/writer.rb', line 488

def format_abnf_range(string)
  alt, o_dash = [:alt], false

  raise RangeError, "cannot format #{string.inspect} an ABNF range" if string.start_with?('^')

  if string.end_with?('-')
    o_dash = true
    string = string[0..-2]
  end

  scanner = StringScanner.new(string)
  hexes, deces = [], []
  in_range = false
  # Build op (alt) from different ranges/enums
  while !scanner.eos?
    if hex = scanner.scan(Terminals::HEX)
      # Append any decimal values
      alt << "%d" + deces.join(".") unless deces.empty?
      deces = []

      if in_range
        # Add "." sequences for any previous hexes
        alt << "%x" + hexes[0..-2].join(".") if hexes.length > 1
        alt << "%x#{hexes.last}-#{hex[2..-1]}"
        in_range, hexes = false, []
      else
        hexes << hex[2..-1]
      end
    elsif dec = scanner.scan(Terminals::R_CHAR)
      # Append any hexadecimal values
      alt << "%x" + hexes.join(".") unless hexes.empty?
      hexes = []

      if in_range
        # Add "." sequences for any previous hexes
        alt << "%d" + deces[0..-2].join(".") if deces.length > 1
        alt << "%d#{deces.last}-#{dec.codepoints.first}"
        in_range, deces = false, []
      else
        deces << dec.codepoints.first.to_s
      end
    end

    in_range = true if scanner.scan(/\-/)
  end

  deces << '45' if o_dash

  # Append hexes and deces as "." sequences (should be only one)
  alt << "%d" + deces.join(".") unless deces.empty?
  alt << "%x" + hexes.join(".") unless hexes.empty?

  # FIXME: HTML abbreviations?
  if alt.length == 2
    # Just return the range or enum
    alt.last
  else
    # Return the alt, which will be further formatted
    alt
  end
end

#format_ebnf(expr, sep: nil, embedded: false) ⇒ Object (protected)

Format the expression part of a rule


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# File 'lib/ebnf/writer.rb', line 241

def format_ebnf(expr, sep: nil, embedded: false)
  return (@options[:html] ? %(<a href="#grammar-production-#{@coder.encode expr}">#{@coder.encode expr}</a>) : expr.to_s) if expr.is_a?(Symbol)
  if expr.is_a?(String)
    return expr.length == 1 ?
      format_ebnf_char(expr) :
      format_ebnf_string(expr, expr.include?('"') ? "'" : '"')
  end
  parts = {
    alt:    (@options[:html] ? "<code>|</code> " : "| "),
    diff:   (@options[:html] ? "<code>-</code> " : "- "),
    star:   (@options[:html] ? "<code>*</code> " : "*"),
    plus:   (@options[:html] ? "<code>+</code> " : "+"),
    opt:    (@options[:html] ? "<code>?</code> " : "?")
  }
  lparen = (@options[:html] ? "<code>(</code> " : "(")
  rparen = (@options[:html] ? "<code>)</code> " : ")")

  case expr.first
  when :istr
    # Looses fidelity, but, oh well ...
    format_ebnf(expr.last, embedded: true)
  when :alt, :diff
    this_sep = (sep ? sep : " ") + parts[expr.first.to_sym]
    res = expr[1..-1].map {|e| format_ebnf(e, embedded: true)}.join(this_sep)
    embedded ? (lparen + res + rparen) : res
  when :star, :plus, :opt
    char = parts[expr.first.to_sym]
    r = format_ebnf(expr[1], embedded: true)
    "#{r}#{char}"
  when :hex
    escape_ebnf_hex(expr.last[2..-1].hex.chr(Encoding::UTF_8))
  when :range
    format_ebnf_range(expr.last)
  when :seq
    this_sep = (sep ? sep : " ")
    res = expr[1..-1].map do |e|
      format_ebnf(e, embedded: true)
    end.join(this_sep)
    embedded ? (lparen + res + rparen) : res
  when :rept
    # Expand repetition
    min, max, value = expr[1..-1]
    if min == 0 && max == 1
      format_ebnf([:opt, value], sep: sep, embedded: embedded)
    elsif min == 0 && max == '*'
      format_ebnf([:star, value], sep: sep, embedded: embedded)
    elsif min == 1 && max == '*'
      format_ebnf([:plus, value], sep: sep, embedded: embedded)
    else
      val2 = [:seq]
      while min > 0
        val2 << value
        min -= 1
        max -= 1 unless max == '*'
      end
      if max == '*'
        val2 << [:star, value]
      else
        opt = nil
        while max > 0
          opt = [:opt, opt ? [:seq, value, opt] : value]
          max -= 1
        end
        val2 << opt if opt
      end
      format_ebnf(val2, sep: sep, embedded: embedded)
    end
  else
    raise "Unknown operator: #{expr.first}"
  end
end

#format_ebnf_char(c) ⇒ Object (protected)

Format a single-character string, prefering hex for non-main ASCII


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# File 'lib/ebnf/writer.rb', line 314

def format_ebnf_char(c)
  case c.ord
  when (0x21)         then (@options[:html] ? %("<code class="grammar-literal">#{@coder.encode c}</code>") : %{"#{c}"})
  when 0x22           then (@options[:html] ? %('<code class="grammar-literal">&quot;</code>') : %{'"'})
  when (0x23..0x7e)   then (@options[:html] ? %("<code class="grammar-literal">#{@coder.encode c}</code>") : %{"#{c}"})
  when (0x80..0xFFFD) then (@options[:html] ? %("<code class="grammar-literal">#{@coder.encode c}</code>") : %{"#{c}"})
  else                     escape_ebnf_hex(c)
  end
end

#format_ebnf_range(string) ⇒ Object (protected)

Format a range


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# File 'lib/ebnf/writer.rb', line 325

def format_ebnf_range(string)
  lbrac  =  (@options[:html] ? "<code>[</code> " : "[")
  rbrac  =  (@options[:html] ? "<code>]</code> " : "]")

  buffer = lbrac
  s = StringScanner.new(string)
  while !s.eos?
    case
    when s.scan(/\A[!"\u0024-\u007e]+/)
      buffer << (@options[:html] ? %(<code class="grammar-literal">#{@coder.encode s.matched}</code>) : s.matched)
    when s.scan(/\A#x\h+/)
      buffer << escape_ebnf_hex(s.matched[2..-1].hex.chr(Encoding::UTF_8))
    else
      buffer << escape_ebnf_hex(s.getch)
    end
  end
  buffer + rbrac
end

#format_ebnf_string(string, quote = '"') ⇒ Object (protected)

Escape a string, using as many UTF-8 characters as possible


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# File 'lib/ebnf/writer.rb', line 345

def format_ebnf_string(string, quote = '"')
  string.each_char do |c|
    case c.ord
    when 0x00..0x19, quote.ord
      raise RangeError, "cannot format #{string.inspect} as an EBNF String: #{c.inspect} is out of range" unless
        ISOEBNF::TERMINAL_CHARACTER.match?(c)
    end
  end

  res = "#{quote}#{string}#{quote}"
  @options[:html] ? @coder.encode(res) : res
end

#format_isoebnf(expr, sep: nil, embedded: false) ⇒ Object (protected)

Format the expression part of a rule


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# File 'lib/ebnf/writer.rb', line 582

def format_isoebnf(expr, sep: nil, embedded: false)
  return (@options[:html] ? %(<a href="#grammar-production-#{@coder.encode expr}">#{@coder.encode expr}</a>) : expr.to_s) if expr.is_a?(Symbol)
  if expr.is_a?(String)
    expr = expr[2..-1].hex.chr if expr =~ /\A#x\h+/
    expr.chars.each do |c|
      raise RangeError, "cannot format #{expr.inspect} as an ISO EBNF String: #{c.inspect} is out of range" unless
        ISOEBNF::TERMINAL_CHARACTER.match?(c)
    end
    if expr =~ /"/
      return (@options[:html] ? %('<code class="grammar-literal">#{@coder.encode expr}</code>') : %('#{expr}'))
    else
      return (@options[:html] ? %("<code class="grammar-literal">#{@coder.encode expr}</code>") : %("#{expr}"))
    end
  end
  parts = {
    alt:    (@options[:html] ? "<code>|</code> " : "| "),
    diff:   (@options[:html] ? "<code>-</code> " : "- "),
  }
  lparen = (@options[:html] ? "<code>(</code> " : "(")
  rparen = (@options[:html] ? "<code>)</code> " : ")")

  case expr.first
  when :istr
    # Looses fidelity, but, oh well ...
    format_isoebnf(expr.last, embedded: true)
  when :alt, :diff
    this_sep = (sep ? sep : " ") + parts[expr.first.to_sym]
    res = expr[1..-1].map {|e| format_isoebnf(e, embedded: true)}.join(this_sep)
    embedded ? (lparen + res + rparen) : res
  when :opt
    r = format_isoebnf(expr[1], embedded: true)
    "[#{r}]"
  when :star
    r = format_isoebnf(expr[1], embedded: true)
    "{#{r}}"
  when :plus
    r = format_isoebnf(expr[1], embedded: true)
    "#{r}, {#{r}}"
  when :hex
    format_isoebnf(expr[1], embedded: true)
  when :range
    res = format_isoebnf_range(expr.last)
    res.is_a?(Array) ?
      format_isoebnf(res, embedded: true) :
      res
  when :seq
    this_sep = "," + (sep ? sep : " ")
    res = expr[1..-1].map do |e|
      format_isoebnf(e, embedded: true)
    end.join(this_sep)
    embedded ? (lparen + res + rparen) : res
  when :rept
    # Expand repetition
    min, max, value = expr[1..-1]
    if min == 0 && max == 1
      format_isoebnf([:opt, value], sep: sep, embedded: embedded)
    elsif min == 0 && max == '*'
      format_isoebnf([:star, value], sep: sep, embedded: embedded)
    elsif min == 1 && max == '*'
      format_isoebnf([:plus, value], sep: sep, embedded: embedded)
    else
      val2 = [:seq]
      while min > 0
        val2 << value
        min -= 1
        max -= 1 unless max == '*'
      end
      if max == '*'
        val2 << [:star, value]
      else
        opt = nil
        while max > 0
          opt = [:opt, opt ? [:seq, value, opt] : value]
          max -= 1
        end
        val2 << opt if opt
      end
      format_isoebnf(val2, sep: sep, embedded: embedded)
    end
  else
    raise "Unknown operator: #{expr.first}"
  end
end

#format_isoebnf_range(string) ⇒ Object (protected)

Format a range Range is formatted as a aliteration of characters

Raises:

  • (RangeError)

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# File 'lib/ebnf/writer.rb', line 668

def format_isoebnf_range(string)
  chars = []
  o_dash = false

  raise RangeError, "cannot format #{string.inspect} an ABNF range" if string.start_with?('^')

  if string.end_with?('-')
    o_dash = true
    string = string[0..-2]
  end

  scanner = StringScanner.new(string)
  in_range = false
  # Build chars from different ranges/enums
  while !scanner.eos?
    char = if hex = scanner.scan(Terminals::HEX)
      hex[2..-1].hex.ord.char(Encoding::UTF_8)
    else scanner.scan(Terminals::R_CHAR)
    end
    raise RangeError, "cannot format #{string.inspect} as an ISO EBNF Aliteration: #{char.inspect} is out of range" unless
      char && ISOEBNF::TERMINAL_CHARACTER.match?(char)

    if in_range
      # calculate characters from chars.last to this char
      raise RangeError, "cannot format #{string.inspect} as an ISO EBNF Aliteration" unless chars.last < char
      chars.concat (chars.last..char).to_a[1..-1]
      in_range = false
    else
      chars << char
    end

    in_range = true if scanner.scan(/\-/)
  end

  chars << '-' if o_dash

  # Possibly only a single character (no character?)
  chars.length == 1 ? chars.last.inspect : chars.unshift(:alt)
end