class Bootsnap::LoadPathCache::Store

def commit_transaction
  if @dirty
    dump_data
    @dirty = false
  end
end

def dump_data
  # Change contents atomically so other processes can't get invalid
  # caches if they read at an inopportune time.
  tmp = "#{@store_path}.#{Process.pid}.#{(rand * 100000).to_i}.tmp"
  FileUtils.mkpath(File.dirname(tmp))
  exclusive_write = File::Constants::CREAT | File::Constants::EXCL | File::Constants::WRONLY
  # `encoding:` looks redundant wrt `binwrite`, but necessary on windows
  # because binary is part of mode.
  File.binwrite(tmp, MessagePack.dump(@data), mode: exclusive_write, encoding: Encoding::BINARY)
  FileUtils.mv(tmp, @store_path)
rescue Errno::EEXIST
  retry
end

def fetch(key)
  raise(SetOutsideTransactionNotAllowed) unless @txn_mutex.owned?
  v = get(key)
  unless v
    @dirty = true
    v = yield
    @data[key] = v
  end
  v
end

def get(key)
  @data[key]
end

def initialize(store_path)
  @store_path = store_path
  # TODO: Remove conditional once Ruby 2.2 support is dropped.
  @txn_mutex =  defined?(::Mutex) ? ::Mutex.new : ::Thread::Mutex.new
  @dirty = false
  load_data
end

def load_data
  @data = begin
    MessagePack.load(File.binread(@store_path))
    # handle malformed data due to upgrade incompatability
  rescue Errno::ENOENT, MessagePack::MalformedFormatError, MessagePack::UnknownExtTypeError, EOFError
    {}
  rescue ArgumentError => e
    e.message =~ /negative array size/ ? {} : raise
  end
end

def set(key, value)
  raise(SetOutsideTransactionNotAllowed) unless @txn_mutex.owned?
  if value != @data[key]
    @dirty = true
    @data[key] = value
  end
end

def transaction
  raise(NestedTransactionError) if @txn_mutex.owned?
  @txn_mutex.synchronize do
    begin
      yield
    ensure
      commit_transaction
    end
  end
end