Module: Mailmate::Lexer Private

Defined in:
lib/mailmate/lexer.rb

This module is part of a private API. You should avoid using this module if possible, as it may be removed or be changed in the future.

Defined Under Namespace

Classes: Error

Constant Summary collapse

KEYWORDS =

This constant is part of a private API. You should avoid using this constant if possible, as it may be removed or be changed in the future. 

%w[and or not exists].freeze
OP_FLAG_CHARS =

This constant is part of a private API. You should avoid using this constant if possible, as it may be removed or be changed in the future.

operator-modifier flags, e.g. =[c], >[f], !=[x]

"cafx"

Class Method Summary collapse

Class Method Details

.lex(input) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



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# File 'lib/mailmate/lexer.rb', line 16

def self.lex(input)
  tokens = []
  i = 0
  while i < input.length
    c = input[i]

    # Whitespace
    if c =~ /\s/
      i += 1
      next
    end

    # Punctuation
    if c == "("
      tokens << [:lparen]; i += 1; next
    elsif c == ")"
      tokens << [:rparen]; i += 1; next
    elsif c == "."
      tokens << [:dot]; i += 1; next
    end

    # Variable reference: $SENT, $PERSONAL_INBOX
    if c == "$"
      j = i + 1
      j += 1 while j < input.length && input[j] =~ /[A-Z_]/
      raise Error, "empty variable name at #{i}" if j == i + 1
      tokens << [:var, input[(i + 1)...j]]
      i = j
      next
    end

    # String: '...'  Only `\\` and `\'` are recognized escapes; other
    # backslashes are preserved literally so IMAP keywords like
    # `\Seen` / `\Flagged` survive intact.
    if c == "'"
      j = i + 1
      buf = +""
      while j < input.length && input[j] != "'"
        if input[j] == "\\" && j + 1 < input.length && (input[j + 1] == "\\" || input[j + 1] == "'")
          buf << input[j + 1]
          j += 2
        else
          buf << input[j]
          j += 1
        end
      end
      raise Error, "unterminated string starting at #{i}" if j >= input.length
      tokens << [:string, buf]
      i = j + 1
      next
    end

    # Operator: !=, =, ~, !~, <, <=, >, >=, with optional [flags]
    if "!=~<>".include?(c)
      op = c
      j = i + 1
      if c == "!" && j < input.length && (input[j] == "=" || input[j] == "~")
        op = "!" + input[j]
        j += 1
      elsif (c == "<" || c == ">") && j < input.length && input[j] == "="
        op = c + "="
        j += 1
      end
      # Optional [flags]
      flags = []
      if j < input.length && input[j] == "["
        k = j + 1
        while k < input.length && OP_FLAG_CHARS.include?(input[k])
          flags << input[k]
          k += 1
        end
        raise Error, "expected ] after operator flags at #{j}" if k >= input.length || input[k] != "]"
        j = k + 1
      end
      tokens << [:op, op, flags]
      i = j
      next
    end

    # Number: 0-9+
    if c =~ /\d/
      j = i
      j += 1 while j < input.length && input[j] =~ /\d/
      tokens << [:number, input[i...j].to_i]
      i = j
      next
    end

    # Shorthand: # or ## followed by ident
    if c == "#"
      j = i
      j += 1 while j < input.length && input[j] == "#"
      start = j
      j += 1 while j < input.length && input[j] =~ /[a-zA-Z0-9_-]/
      raise Error, "empty shorthand at #{i}" if start == j
      tokens << [:shorthand, input[i...j]]
      i = j
      next
    end

    # Identifier: [a-zA-Z_][a-zA-Z0-9_-]*
    if c =~ /[a-zA-Z_]/
      j = i
      j += 1 while j < input.length && input[j] =~ /[a-zA-Z0-9_-]/
      word = input[i...j]
      if KEYWORDS.include?(word)
        tokens << [:keyword, word]
      else
        tokens << [:ident, word]
      end
      i = j
      next
    end

    raise Error, "unexpected char #{c.inspect} at position #{i}"
  end
  tokens << [:eof]
  tokens
end