1 files changed, 41 insertions, 0 deletions
diff --git a/pim/lib/cal/backend.go b/pim/lib/cal/backend.go
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+package cal
+
+import "time"
+
+// A Backend supplies a calendar's events and, where the protocol allows
+// it, accepts changes back.
+//
+// Everything above this line -- the tree, recurrence expansion, ctl,
+// query, alarm, changed, the 9p service -- is the same whether the
+// events arrived as a published .ics, over CalDAV or over JMAP. Only
+// fetching and writing differ, so only fetching and writing live here.
+type Backend interface {
+	// Name of the calendar, as it appears in ctl.
+	Name() string
+
+	// Caps says what this backend can do, so that a tool can report
+	// "read only" rather than trying and failing. The vocabulary is
+	// read, write, rsvp, schedule; see pim/doc/design.md.
+	Caps() string
+
+	// Refresh is how often to poll. Zero means never.
+	Refresh() time.Duration
+
+	// Status reports when the backend last synced and the error, if
+	// any, from that attempt.
+	Status() (time.Time, string)
+
+	// Sync brings the backend up to date and reports whether anything
+	// actually changed. A backend that cannot tell should say true --
+	// the cost is a needless rebuild, not a wrong answer.
+	Sync() (bool, error)
+
+	// Events returns the calendar as it now stands.
+	Events() ([]*Event, error)
+}
+
+// Describer is implemented by backends with more to say in ctl: the
+// source directory, the url, whatever identifies where events came from.
+type Describer interface {
+	Describe() string
+}