Balanced Brackets

# title: Balanced Brackets
# source: https://rosettacode.org/wiki/Balanced_brackets
# category: Rosetta Code Popular
# difficulty: Easy
# summary: Check whether bracket pairs are properly nested and closed by scanning the text with a stack.
# tags: popular, parsing, stack, strings
# vibe: 0.2

def opener_for(char)
  if char == ")"
    "("
  elsif char == "]"
    "["
  elsif char == "}"
    "{"
  else
    nil
  end
end

def closer?(char)
  char == ")" || char == "]" || char == "}"
end

def balanced_brackets?(text)
  stack = []
  depth = 0
  index = 0

  while index < text.length
    char = text.slice(index)

    if char == "(" || char == "[" || char == "{"
      stack = stack.push(char)
      depth = depth + 1
    elsif closer?(char)
      if depth == 0
        return false
      end

      popped = stack.pop
      stack = popped[:array]
      depth = depth - 1

      if popped[:popped] != opener_for(char)
        return false
      end
    end

    index = index + 1
  end

  depth == 0
end

def run
  {
    nested_true: balanced_brackets?("{[()()]}"),
    mixed_true: balanced_brackets?("function(x) { return [x, x + 1] }"),
    crossed_false: balanced_brackets?("([)]"),
    incomplete_false: balanced_brackets?("{[()}")
  }
end