Class: RailsVitals::Playground::SafeChainBuilder

Inherits:
Object
  • Object
show all
Defined in:
lib/rails_vitals/playground/safe_chain_builder.rb

Constant Summary collapse

ALLOWED_METHODS = 
%w[
  all where select limit offset order group
  includes preload eager_load joins left_joins
  find find_by first last count sum average
  pluck distinct having references unscoped not
].freeze
DISALLOWED_CLASS_METHODS = 
%w[
  connection execute exec system eval send public_send __send__
  instance_eval class_eval module_eval define_method method_missing
  delete destroy delete_all destroy_all update_all
].freeze
ParseError = 
Class.new(StandardError)

Class Method Summary collapse

Class Method Details

.build(chain_str, model) ⇒ Object

Raises:



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# File 'lib/rails_vitals/playground/safe_chain_builder.rb', line 21

def self.build(chain_str, model)
  relation = model.all
  parse_chain(chain_str).each do |method_name, args|
    if DISALLOWED_CLASS_METHODS.include?(method_name)
      raise ParseError, "Method '#{method_name}' is not allowed for security reasons"
    end
    unless ALLOWED_METHODS.include?(method_name)
      raise ParseError, "Method '#{method_name}' is not allowed. Allowed: #{ALLOWED_METHODS.join(', ')}"
    end
    relation = relation.public_send(method_name, *args)
  end

  raise ParseError, "Expression must return an ActiveRecord::Relation" unless relation.is_a?(ActiveRecord::Relation)
  relation
end

.keyword_hash_start?(scanner) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rails_vitals/playground/safe_chain_builder.rb', line 86

def self.keyword_hash_start?(scanner)
  pos = scanner.pos
  ident = scanner.scan(/[a-zA-Z_][a-zA-Z0-9_]*/)
  return false unless ident

  scanner.skip(/\s*/)

  if scanner.scan(/:/) && !scanner.scan(/:/)
    scanner.pos = pos
    return true
  end

  scanner.pos = pos
  false
end

.parse_args(scanner) ⇒ Object 



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# File 'lib/rails_vitals/playground/safe_chain_builder.rb', line 64

def self.parse_args(scanner)
  args = []
  scanner.skip(/\s+/)
  return args if scanner.eos? || scanner.peek(1) == ")"

  loop do
    scanner.skip(/\s+/)
    break if scanner.eos? || scanner.peek(1) == ")"

    if keyword_hash_start?(scanner)
      args << scan_keyword_hash(scanner)
    else
      args << scan_value(scanner)
    end

    scanner.skip(/\s+/)
    break unless scanner.scan(/,/)
  end

  args
end

.parse_chain(str) ⇒ Object 



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# File 'lib/rails_vitals/playground/safe_chain_builder.rb', line 39

def self.parse_chain(str)
  scanner = StringScanner.new(str)
  calls = []
  scanner.skip(/\s+/)

  until scanner.eos?
    scanner.skip(/\.\s*/)

    name = scanner.scan(/[a-z_][a-zA-Z0-9_!?]*/)
    raise ParseError, "Expected method name at position #{scanner.pos}" unless name

    scanner.skip(/\s+/)
    if scanner.scan(/\(/)
      args = parse_args(scanner)
      scanner.skip(/\s*\)/)
      calls << [ name, args ]
    else
      calls << [ name, [] ]
    end
    scanner.skip(/\s+/)
  end

  calls
end

.parse_hash_key(scanner) ⇒ Object 



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# File 'lib/rails_vitals/playground/safe_chain_builder.rb', line 272

def self.parse_hash_key(scanner)
  case scanner.peek(1)
  when '"', "'" then scan_string(scanner)
  when ":" then scan_symbol(scanner)
  else
    ident = scanner.scan(/[a-zA-Z_][a-zA-Z0-9_]*/)
    raise ParseError, "Expected hash key" unless ident
    ident
  end
end

.scan_array(scanner) ⇒ Object

Raises:



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# File 'lib/rails_vitals/playground/safe_chain_builder.rb', line 225

def self.scan_array(scanner)
  scanner.pos += 1
  arr = []
  scanner.skip(/\s+/)
  unless scanner.peek(1) == "]"
    loop do
      arr << scan_value(scanner)
      scanner.skip(/\s+/)
      break unless scanner.scan(/,/)
      scanner.skip(/\s+/)
    end
  end
  scanner.skip(/\s*\]/)
  raise ParseError, "Unterminated array" unless scanner.matched
  arr
end

.scan_double_quoted_string(scanner) ⇒ Object

Raises:



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# File 'lib/rails_vitals/playground/safe_chain_builder.rb', line 177

def self.scan_double_quoted_string(scanner)
  scanner.pos += 1
  result = +""
  until scanner.eos?
    case scanner.peek(1)
    when '"'
      scanner.pos += 1
      return result
    when "\\"
      scanner.pos += 1
      escaped = scanner.getch
      case escaped
      when '"' then result << '"'
      when "\\" then result << "\\"
      when "n" then result << "\n"
      when "t" then result << "\t"
      when "r" then result << "\r"
      when "#" then result << "#"
      else result << "\\#{escaped}"
      end
    else
      result << scanner.getch
    end
  end
  raise ParseError, "Unterminated double-quoted string"
end

.scan_hash_literal(scanner) ⇒ Object

Raises:



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# File 'lib/rails_vitals/playground/safe_chain_builder.rb', line 242

def self.scan_hash_literal(scanner)
  scanner.pos += 1
  hash = {}
  scanner.skip(/\s+/)
  unless scanner.eos? || scanner.peek(1) == "}"
    loop do
      scanner.skip(/\s+/)
      break if scanner.eos? || scanner.peek(1) == "}"

      key = parse_hash_key(scanner)
      scanner.skip(/\s+/)

      if scanner.scan(/=>/)
        scanner.skip(/\s+/)
        hash[key] = scan_value(scanner)
      elsif scanner.scan(/:\s*/)
        hash[key.to_sym] = scan_value(scanner)
      else
        raise ParseError, "Expected '=>' or ':' after hash key"
      end

      scanner.skip(/\s+/)
      break unless scanner.scan(/,/)
    end
  end
  scanner.skip(/\s*}/)
  raise ParseError, "Unterminated hash" unless scanner.matched
  hash
end

.scan_keyword_hash(scanner) ⇒ Object 



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# File 'lib/rails_vitals/playground/safe_chain_builder.rb', line 102

def self.scan_keyword_hash(scanner)
  hash = {}
  loop do
    scanner.skip(/\s+/)
    break if scanner.eos? || scanner.peek(1) == ")" || scanner.peek(1) == "}"

    key = scanner.scan(/[a-zA-Z_][a-zA-Z0-9_]*/)
    raise ParseError, "Expected hash key" unless key
    scanner.skip(/\s*:\s*/)
    value = scan_value(scanner)
    hash[key.to_sym] = value
    scanner.skip(/\s+/)
    break unless scanner.scan(/,/)
  end
  hash
end

.scan_number(scanner) ⇒ Object

Raises:



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# File 'lib/rails_vitals/playground/safe_chain_builder.rb', line 215

def self.scan_number(scanner)
  num_str = scanner.scan(/-?[0-9]+(\.[0-9]+)?([eE][+-]?[0-9]+)?/)
  raise ParseError, "Invalid number at position #{scanner.pos}" unless num_str
  if num_str.include?(".") || num_str.match?(/[eE]/)
    num_str.to_f
  else
    num_str.to_i
  end
end

.scan_single_quoted_string(scanner) ⇒ Object

Raises:



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# File 'lib/rails_vitals/playground/safe_chain_builder.rb', line 154

def self.scan_single_quoted_string(scanner)
  scanner.pos += 1
  result = +""
  until scanner.eos?
    case scanner.peek(1)
    when "'"
      scanner.pos += 1
      return result
    when "\\"
      scanner.pos += 1
      escaped = scanner.getch
      case escaped
      when "'" then result << "'"
      when "\\" then result << "\\"
      else result << "\\#{escaped}"
      end
    else
      result << scanner.getch
    end
  end
  raise ParseError, "Unterminated single-quoted string"
end

.scan_string(scanner) ⇒ Object 



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# File 'lib/rails_vitals/playground/safe_chain_builder.rb', line 283

def self.scan_string(scanner)
  case scanner.peek(1)
  when "'" then scan_single_quoted_string(scanner)
  when '"' then scan_double_quoted_string(scanner)
  else raise ParseError, "Expected string"
  end
end

.scan_symbol(scanner) ⇒ Object 



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# File 'lib/rails_vitals/playground/safe_chain_builder.rb', line 204

def self.scan_symbol(scanner)
  scanner.pos += 1
  if scanner.scan(/[a-zA-Z_][a-zA-Z0-9_]*/)
    scanner.matched.to_sym
  elsif (str = scanner.scan(/"[^"]*"/) || scanner.scan(/'[^']*'/))
    str[1..-2].to_sym
  else
    raise ParseError, "Invalid symbol at position #{scanner.pos}"
  end
end

.scan_value(scanner) ⇒ Object

Raises:



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# File 'lib/rails_vitals/playground/safe_chain_builder.rb', line 119

def self.scan_value(scanner)
  scanner.skip(/\s+/)
  ch = scanner.peek(1)
  raise ParseError, "Unexpected end of expression" unless ch

  case ch
  when "'" then scan_single_quoted_string(scanner)
  when '"' then scan_double_quoted_string(scanner)
  when ":" then scan_symbol(scanner)
  when "t"
    if scanner.scan(/true\b/)
      true
    else
      raise ParseError, "Unexpected token at position #{scanner.pos}"
    end
  when "f"
    if scanner.scan(/false\b/)
      false
    else
      raise ParseError, "Unexpected token at position #{scanner.pos}"
    end
  when "n"
    if scanner.scan(/nil\b/)
      nil
    else
      raise ParseError, "Unexpected token at position #{scanner.pos}"
    end
  when "[" then scan_array(scanner)
  when "{" then scan_hash_literal(scanner)
  when "-", "+", "0", "1", "2", "3", "4", "5", "6", "7", "8", "9" then scan_number(scanner)
  else
    raise ParseError, "Unexpected token '#{ch}' at position #{scanner.pos}"
  end
end