class Dry::Schema::KeyValidator

def call(result)
  input = result.to_h
  input_paths = key_paths(input)
  key_paths = key_map.to_dot_notation
  input_paths.each do |path|
    error_path = validate_path(key_paths, path)
    next unless error_path
    result.add_error([:unexpected_key, [error_path, input]])
  end
  result
end

def hashes_or_arrays(xs)
  xs.select { |x|
    (x.is_a?(::Array) || x.is_a?(::Hash)) && !x.empty?
  }
end

def key_paths(hash)
  hash.flat_map { |key, value|
    case value
    when ::Hash
      if value.empty?
        [key.to_s]
      else
        [key].product(key_paths(hash[key])).map { _1.join(DOT) }
      end
    when ::Array
      hashes_or_arrays = hashes_or_arrays(value)
      if hashes_or_arrays.empty?
        [key.to_s]
      else
        hashes_or_arrays.flat_map.with_index { |el, idx|
          key_paths(el).map { ["#{key}[#{idx}]", *_1].join(DOT) }
        }
      end
    else
      key.to_s
    end
  }
end

def paths_match?(input_path, key_path)
  residue = key_path.sub(input_path, "")
  residue.empty? || residue.start_with?(DOT, BRACKETS)
end

def validate_path(key_paths, path)
  if path[INDEX_REGEX]
    key = path.gsub(INDEX_REGEX, BRACKETS)
    if key_paths.none? { paths_match?(key, _1) }
      arr = path.gsub(INDEX_REGEX) { ".#{_1[1]}" }
      arr.split(DOT).map { DIGIT_REGEX.match?(_1) ? Integer(_1, 10) : _1.to_sym }
    end
  elsif key_paths.none? { paths_match?(path, _1) }
    path
  end
end