Local Syncing

[oubiwann]

Once this ticket is done:

• Add TCP server for local syncing #9

we'll be able to send encrypted copies of the data base to other local nodes/instances. Full syncing is going to be a while out ... I think I'd prefer wait on syncing passwords until we had support for multiple versions (see #32). For now, though, we can sync metadata.

Before this, we need some new features/enhancements:

• Database restores #44
• Update metadata to include synced timestamp field #43
• When a password is accessed, update the last_used field with time::now #42

The communications and actions protocol might look something like this:

• A sends encrypted data to B
• B receives request and acknowledges by sending encrypted data to A
• A lets B know that it received B's data
• At this point, both may proceed with the following, sending an error to the peer in the event of a problem (which will cause both to abort):
  • decrypt data
  • iterate over data to be synced, collecting into a temp data structure
  • backing up the current state to disk, tagged with "sync"
  • updating local state

We'll need a protocol struct for tracking all this ... maybe in sync.rs:

struct Protocol {
  node: String,
  initiator: (Initiator::Self, Initiator::Other),
  data_sent: bool,
  data_received: bool,
  error: (Error::Self, Error::Other, Error:None),
  decrypted: bool,
  iterated: bool,
  backup: bool,
  data_merged: bool,
  data_replaced: bool,
}

Merging logic to be done:

• created - take the less recent date
• imported - take the less recent date
• updated - take the more recent date
• password_changed - take the more recent date
• last_used - take the more recent date
• synced - time::now
• access_count - sum from both

Any fields not listed will be done after #32 has been completed.

With this in place:

• Add new sync CLI command, taking the host as arg