Class: Markbridge::Parsers::BBCode::PeekableEnumerator

Inherits:
Object
  • Object
show all
Defined in:
lib/markbridge/parsers/bbcode/peekable_enumerator.rb

Overview

Wrapper around a scanner that allows peeking at upcoming tokens without consuming them.

This class buffers tokens pulled from a scanner (which must implement next_token) so callers can:

  • inspect the next token with #peek without advancing the scanner
  • inspect several upcoming tokens with #peek_ahead
  • consume tokens with #next (returns nil when exhausted)

The enumerator is lazy: tokens are only requested from the scanner when needed. Once the underlying scanner returns nil, the enumerator is marked finished and further peeks return nil (for single peeks) or an empty array (for multi-peeks).

Examples:

Basic usage

scanner = YourScanner.new("...") # responds to `next_token`
enum = PeekableEnumerator.new(scanner)
enum.peek        # => next token (no consume)
enum.peek_ahead(3) # => array of up to 3 upcoming tokens
enum.next        # => consumes and returns next token

See Also:

Instance Method Summary collapse

Constructor Details

#initialize(scanner) ⇒ PeekableEnumerator

Initialize a new PeekableEnumerator.

Parameters:

  • scanner (Object) —

    the scanner object that responds to next_token



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# File 'lib/markbridge/parsers/bbcode/peekable_enumerator.rb', line 32

def initialize(scanner)
  @scanner = scanner
  @peeked = []
end

Instance Method Details

#next ⇒ Object? Also known as: next_token

Consume and return the next token.

Returns:

  • (Object, nil) —

    next token or nil when exhausted



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# File 'lib/markbridge/parsers/bbcode/peekable_enumerator.rb', line 39

def next
  ensure_peeked(1)
  @peeked.shift
end

#peek ⇒ Object?

Peek at the next single token without consuming it.

Returns:

  • (Object, nil) —

    the next token or nil when exhausted



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# File 'lib/markbridge/parsers/bbcode/peekable_enumerator.rb', line 46

def peek
  ensure_peeked(1)
  @peeked.first
end

#peek_ahead(count) ⇒ Array<Object>

Peek ahead at up to count upcoming tokens without consuming them.

Parameters:

  • count (Integer) —

    number of tokens to peek ahead (clamped to 0..)

Returns:

  • (Array<Object>) —

    array of upcoming tokens (possibly empty)



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# File 'lib/markbridge/parsers/bbcode/peekable_enumerator.rb', line 54

def peek_ahead(count)
  count = [count, 0].max
  ensure_peeked(count)
  @peeked.first(count)
end