# encoding: utf-8

module FileWatch
  class SincedbRecordSerializer

    attr_reader :expired_keys

    def self.days_to_seconds(days)
      (24 * 3600) * days.to_f
    end

    def initialize(sincedb_value_expiry)
      @sincedb_value_expiry = sincedb_value_expiry
      @expired_keys = []
    end

    def update_sincedb_value_expiry_from_days(days)
      @sincedb_value_expiry = SincedbRecordSerializer.days_to_seconds(days)
    end

    def serialize(db, io, as_of = Time.now.to_f)
      @expired_keys.clear
      db.each do |key, value|
        if as_of > value.last_changed_at_expires(@sincedb_value_expiry)
          @expired_keys << key
          next
        end
        io.write(serialize_record(key, value))
      end
    end

    def deserialize(io)
      io.each do |record|
        yield deserialize_record(record) #.tap{|val| STDERR.puts val}
      end
    end

    def serialize_record(k, v)
      # effectively InodeStruct#to_s SincedbValue#to_s
      "#{k} #{v}\n"
    end

    def deserialize_record(record)
      return [] if record.nil? || record.empty?
      parts = record.split(" ")
      parse_line_v2(parts) || parse_line_v1(parts)
    end

    private

    def parse_line_v2(parts)
      # new format e.g. 2977152 1 4 94 1519319662.852678 'path/to/file'
      # do we want to store the last known state of the watched file too?
      return false if parts.size < 5
      inode_struct = prepare_inode_struct(parts)
      pos = parts.shift.to_i
      expires_at = Float(parts.shift) # this is like Time.now.to_f
      path_in_sincedb = parts.join(" ")
      value = SincedbValue.new(pos, expires_at).add_path_in_sincedb(path_in_sincedb)
      [inode_struct, value]
    end

    def parse_line_v1(parts)
      # old inode based e.g. 2977152 1 4 94
      inode_struct = prepare_inode_struct(parts)
      pos = parts.shift.to_i
      [inode_struct, SincedbValue.new(pos)]
    end

    def prepare_inode_struct(parts)
      InodeStruct.new(parts.shift, *parts.shift(2).map(&:to_i))
    end
  end
end
