module Sprockets::Utils

def concat_javascript_sources(buf, source)
  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?
    if !string_end_with_semicolon?(source)
      buf << ";\n"
    elsif source[source.size - 1].ord != 0x0A
      buf << "\n"
    end
  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, seen = [path], Set.new
  while path = stack.pop
    if !seen.include?(path.last)
      seen.add(path.last)
      paths << path if path.size > 1
      Array(yield path.last).reverse_each do |node|
        stack.push(path + [node])
      end
    end
  end
  paths
end

def duplicable?(obj)
  if RUBY_VERSION >= "2.4.0"
    true
  else
    case obj
    when NilClass, FalseClass, TrueClass, Symbol, Numeric
      false
    else
      true
    end
  end
end

def hash_reassoc(hash, *keys, &block)
  if keys.size == 1
    hash_reassoc1(hash, keys[0], &block)
  else
    hash_reassoc1(hash, keys[0]) do |value|
      hash_reassoc(value, *keys[1..-1], &block)
    end
  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
  unless UNBOUND_METHODS_BIND_TO_ANY_OBJECT
    base.send(:include, mod) unless base < mod
  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 normalize_extension(extension)
  extension = extension.to_s
  if extension[/^\./]
    extension
  else
    ".#{extension}"
  end
end

def string_end_with_semicolon?(str)
  i = str.size - 1
  while i >= 0
    c = str[i].ord
    i -= 1
    # Need to compare against the ordinals because the string can be UTF_8 or UTF_32LE encoded
    # 0x0A == "\n"
    # 0x20 == " "
    # 0x09 == "\t"
    # 0x3B == ";"
    unless c == 0x0A || c == 0x20 || c == 0x09
      return c === 0x3B
    end
  end
  true
end