gapi: Add world interface and refactor existing code to use it

This is the initial base of what will hopefully become a powerful API
that machines will use to communicate. It will be the basis of the
stateful data store that can be used for exported resources, fact
exchange, state machine flags, locks, and much more.

etcd/world.go

@@ -0,0 +1,43 @@
+// Mgmt
+// Copyright (C) 2013-2016+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package etcd
+
+import (
+	"github.com/purpleidea/mgmt/resources"
+)
+
+// World is an etcd backed implementation of the World interface.
+type World struct {
+	Hostname string // uuid for the consumer of these
+	EmbdEtcd *EmbdEtcd
+}
+
+// ResExport exports a list of resources under our hostname namespace.
+// Subsequent calls replace the previously set collection atomically.
+func (obj *World) ResExport(resourceList []resources.Res) error {
+	return EtcdSetResources(obj.EmbdEtcd, obj.Hostname, resourceList)
+}
+
+// ResCollect gets the collection of exported resources which match the filter.
+// It does this atomically so that a call always returns a complete collection.
+func (obj *World) ResCollect(hostnameFilter, kindFilter []string) ([]resources.Res, error) {
+	// XXX: should we be restricted to retrieving resources that were
+	// exported with a tag that allows or restricts our hostname? We could
+	// enforce that here if the underlying API supported it... Add this?
+	return EtcdGetResources(obj.EmbdEtcd, hostnameFilter, kindFilter)
+}