module Sprockets::Utils

def concat_javascript_sources(buf, source)
  return buf if source.bytesize <= 0
  buf << source
  # If the source contains non-ASCII characters, indexing on it becomes O(N).
  # This will lead to O(N^2) performance in string_end_with_semicolon?, so we should use 32 bit encoding to make sure indexing stays O(1)
  source = source.encode(Encoding::UTF_32LE) unless source.ascii_only?
  return buf if string_end_with_semicolon?(source)
  # If the last character in the string was whitespace,
  # such as a newline, then we want to put the semicolon
  # before the whitespace. Otherwise append a semicolon.
  if whitespace = WHITESPACE_ORDINALS[source[-1].ord]
    buf[-1] = ";#{whitespace}"
  else
    buf << ";"
  end
  buf
end

def dfs(initial)
  nodes, seen = Set.new, Set.new
  stack = Array(initial).reverse
  while node = stack.pop
    if seen.include?(node)
      nodes.add(node)
    else
      seen.add(node)
      stack.push(node)
      stack.concat(Array(yield node).reverse)
    end
  end
  nodes
end

def dfs_paths(path)
  paths = []
  stack = [path]
  seen  = Set.new
  while path = stack.pop
    seen.add(path.last)
    paths << path
    children = yield path.last
    children.reverse_each do |node|
      stack.push(path + [node]) unless seen.include?(node)
    end
  end
  paths
end

def duplicable?(obj)
  case obj
  when NilClass, FalseClass, TrueClass, Symbol, Numeric
    false
  else
    true
  end
end

def hash_reassoc(hash, key_a, key_b = nil, &block)
  if key_b
    hash_reassoc1(hash, key_a) do |value|
      hash_reassoc(value, key_b, &block)
    end
  else
    hash_reassoc1(hash, key_a, &block)
  end
end

def hash_reassoc1(hash, key)
  hash = hash.dup if hash.frozen?
  old_value = hash[key]
  old_value = old_value.dup if duplicable?(old_value)
  new_value = yield old_value
  new_value.freeze if duplicable?(new_value)
  hash.store(key, new_value)
  hash.freeze
end

def module_include(base, mod)
  old_methods = {}
  mod.instance_methods.each do |sym|
    old_methods[sym] = base.instance_method(sym) if base.method_defined?(sym)
  end
  mod.instance_methods.each do |sym|
    method = mod.instance_method(sym)
    base.send(:define_method, sym, method)
  end
  yield
ensure
  mod.instance_methods.each do |sym|
    base.send(:undef_method, sym) if base.method_defined?(sym)
  end
  old_methods.each do |sym, method|
    base.send(:define_method, sym, method)
  end
end

def string_end_with_semicolon?(str)
  i = str.size - 1
  while i >= 0
    c = str[i].ord
    i -= 1
    next if WHITESPACE_ORDINALS[c]
    return c === 0x3B
  end
  true
end