module Dotenv

def instrument(name, payload = {}, &block)
  if instrumenter
    instrumenter.instrument("#{name}.dotenv", payload, &block)
  else
    block&.call payload
  end
end

def load(*filenames, overwrite: false, ignore: true)
  parse(*filenames, overwrite: overwrite, ignore: ignore) do |env|
    instrument(:load, env: env) do |payload|
      update(env, overwrite: overwrite)
    end
  end
end

def load!(*filenames)
  load(*filenames, ignore: false)
end

def modify(env = {}, &block)
  SEMAPHORE.synchronize do
    diff = Dotenv::Diff.new
    update(env, overwrite: true)
    block.call
  ensure
    restore(diff.a, safe: true)
  end
end

def overwrite(*filenames)
  load(*filenames, overwrite: true)
end

def overwrite!(*filenames)
  load(*filenames, overwrite: true, ignore: false)
end

def parse(*filenames, overwrite: false, ignore: true, &block)
  filenames << ".env" if filenames.empty?
  filenames = filenames.reverse if overwrite
  filenames.reduce({}) do |hash, filename|
    begin
      env = Environment.new(File.expand_path(filename), overwrite: overwrite)
      env = block.call(env) if block
    rescue Errno::ENOENT, Errno::EISDIR
      raise unless ignore
    end
    hash.merge! env || {}
  end
end

def require_keys(*keys)
  missing_keys = keys.flatten - ::ENV.keys
  return if missing_keys.empty?
  raise MissingKeys, missing_keys
end

def restore(env = @diff&.a, safe: Thread.current == Thread.main)
  # No previously saved or provided state to restore
  return unless env
  diff = Dotenv::Diff.new(b: env)
  return unless diff.any?
  unless safe
    raise ThreadError, <<~EOE.tr("\n", " ")
      Dotenv.restore is not thread safe. Use `Dotenv.modify { }` to update ENV for the duration
      of the block in a thread safe manner, or call `Dotenv.restore(safe: true)` to ignore
      this error.
    EOE
  end
  instrument(:restore, diff: diff) { ENV.replace(env) }
end

def save
  instrument(:save) do |payload|
    @diff = payload[:diff] = Dotenv::Diff.new
  end
end

def update(env = {}, overwrite: false)
  instrument(:update) do |payload|
    diff = payload[:diff] = Dotenv::Diff.new do
      ENV.update(env.transform_keys(&:to_s)) do |key, old_value, new_value|
        # This block is called when a key exists. Return the new value if overwrite is true.
        overwrite ? new_value : old_value
      end
    end
    diff.env
  end
end