presence

type Memory struct {
	// contains filtered or unexported fields
}

type Options struct {
	// Store keeps the visits; nil keeps them in memory.
	Store Store
	// TTL is how long a tab counts as present after it last reported; zero
	// means 45 seconds. Tabs report more often than that.
	TTL time.Duration
	// Sweep is how often forgotten tabs are cleared and their pages told;
	// zero means 10 seconds.
	Sweep time.Duration
	// MaxStreams caps the open streams of the server, MaxStreamsPerUser
	// those of one user; zero means 500 and 8.
	MaxStreams        int
	MaxStreamsPerUser int
	// Now is the clock, for tests; nil uses time.Now.
	Now func() time.Time
}

type Store interface {
	// Touch records the visit, replacing the earlier one of the same user
	// and tab, and returns the page that tab was on before: empty for a new
	// tab.
	Touch(ctx context.Context, visit Visit) (previous string, err error)
	// Leave forgets the tab of user and returns the page it was on; empty
	// when the store did not know it.
	Leave(ctx context.Context, user, tab string) (page string, err error)
	// Visits lists the visits of page.
	Visits(ctx context.Context, page string) ([]Visit, error)
	// Expire forgets the visits last seen before before and returns the
	// pages they were on.
	Expire(ctx context.Context, before time.Time) (pages []string, err error)
}

type Tracker struct {
	// contains filtered or unexported fields
}

type Viewer struct {
	ID   string
	Name string
	// Initials are one or two letters of the name for a small avatar; "?"
	// without name.
	Initials string
}

type Visit struct {
	// Tab identifies the browser tab; the browser chooses it.
	Tab string
	// User is the user's ID and Name what others see: the user's name, never
	// an e-mail address. An empty name shows as a general one.
	User string
	Name string
	// Page is the normalised admin path, the same for every language tab
	// of an editor, such as the editor of a page.
	Page string
	// Seen is when the tab last reported.
	Seen time.Time
}