model

type Content interface {
	ID() string     // universally unique ID, typically a URL
	Title_() string // empty if missing or not supported
	Body_() string  // text content; some day, a sequence of multimedia elements

	// These are zero if unknown.
	CreatedAt_() time.Time
	UpdatedAt_() time.Time
}

type DBContent struct {
	DBTime  timed.DBTime
	Content Content
}

type Identity struct {
	Realm Realm
	ID    string // unique for the realm
	Name  string // non-canonical display name, if known (e.g. "Pat Brown", "The Go Team")
}

type Post interface {
	Content

	Project() string   // ID of project this belongs to
	Author() *Identity // nil if unknown or not supported
	CanEdit() bool     // can the content or metadata of this post be modified?

	CanHaveChildren() bool // can this kind of Post have children?
	ParentID() string      // the parent post's ID, empty if this is a root post

	Updates() PostUpdates // set changes on a PostUpdates, then pass to [Source.Update]
}

type PostUpdates interface {
	SetTitle(string) error // set the title
	SetBody(string) error  // set the body
}

type Realm string

type Source[T Content] interface {
	// A unique name for the source. For example, "GitHubIssues".
	Name() string

	// Download the current value for the ID from the external source.
	Read(ctx context.Context, id string) (T, error)

	// Update c by applying the given Updates.
	// Updates should describe how to modify c in a form that the Source
	// understands. For a [Post], call [Post.Update] to obtain such a value.
	Update(ctx context.Context, c T, u Updates) error

	// Create a new instance of T in the source, returning its unique ID.
	Create(context.Context, T) (id string, err error)

	// Delete the item with the given ID.
	// No error is returned if the ID is not found.
	// An error is returned if deletion is not unsupported or the item cannot be deleted.
	Delete(_ context.Context, id string) error
}

type Updates interface {
}

type Watcher[T any] interface {
	Recent() iter.Seq[T]
	Restart()
	MarkOld(timed.DBTime)
	Flush()
	Latest() timed.DBTime
}