organize essential APIs into platform, workflow and pkg folders (#337)

Add more logic to the way code is organized.

	/pkg -- library code not directly connected to micromdm
	/mdm -- packages meant for the services devices interract with. The MDM protocol.
	/dep -- DEP API and related packages.
	/platform -- Core APIs the server provides. Commands API, Devices API, queue, pubsub etc.
	/workflow -- Packages/API that build on top of platform. Today that's the webhook package.
		     Depending on what ends up here, the workflow folder might become its own repository.

platform/queue/queue_test.go

@@ -0,0 +1,178 @@
+package queue
+
+import (
+	"context"
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"github.com/boltdb/bolt"
+	"github.com/micromdm/mdm"
+)
+
+func TestNext_Error(t *testing.T) {
+	store, teardown := setupDB(t)
+	defer teardown()
+
+	dc := &DeviceCommand{DeviceUDID: "TestDevice"}
+	dc.Commands = append(dc.Commands, Command{UUID: "xCmd"})
+	dc.Commands = append(dc.Commands, Command{UUID: "yCmd"})
+	dc.Commands = append(dc.Commands, Command{UUID: "zCmd"})
+	if err := store.Save(dc); err != nil {
+		t.Fatal(err)
+	}
+
+	ctx := context.Background()
+	resp := mdm.Response{
+		UDID:        dc.DeviceUDID,
+		CommandUUID: "xCmd",
+		Status:      "Error",
+	}
+	for range dc.Commands {
+		cmd, err := store.Next(ctx, resp)
+		if err != nil {
+			t.Fatalf("expected nil, but got err: %s", err)
+		}
+		if cmd == nil {
+			t.Fatal("expected cmd but got nil")
+		}
+
+		if have, errd := cmd.UUID, resp.CommandUUID; have == errd {
+			t.Error("got back command which previously failed")
+		}
+	}
+}
+
+func TestNext_NotNow(t *testing.T) {
+	store, teardown := setupDB(t)
+	defer teardown()
+
+	dc := &DeviceCommand{DeviceUDID: "TestDevice"}
+	dc.Commands = append(dc.Commands, Command{UUID: "xCmd"})
+	dc.Commands = append(dc.Commands, Command{UUID: "yCmd"})
+	if err := store.Save(dc); err != nil {
+		t.Fatal(err)
+	}
+
+	ctx := context.Background()
+	tf := func(t *testing.T) {
+
+
+		resp := mdm.Response{
+			UDID:        dc.DeviceUDID,
+			CommandUUID: "yCmd",
+			Status:      "NotNow",
+		}
+		cmd, err := store.Next(ctx, resp)
+
+		if err != nil {
+				t.Fatalf("expected nil, but got err: %s", err)
+		}
+
+		resp = mdm.Response{
+			UDID:        dc.DeviceUDID,
+			CommandUUID: cmd.UUID,
+			Status:      "NotNow",
+		}
+
+		cmd, err = store.Next(ctx, resp)
+		if err != nil {
+			t.Fatalf("expected nil, but got err: %s", err)
+		}
+		if cmd != nil {
+			t.Error("Got back a notnowed command.")
+		}
+	}
+
+	t.Run("withManyCommands", tf)
+	dc.Commands = []Command{{UUID: "xCmd"}}
+	if err := store.Save(dc); err != nil {
+		t.Fatal(err)
+	}
+	t.Run("withOneCommand", tf)
+}
+
+func TestNext_Idle(t *testing.T) {
+	store, teardown := setupDB(t)
+	defer teardown()
+
+	dc := &DeviceCommand{DeviceUDID: "TestDevice"}
+	dc.Commands = append(dc.Commands, Command{UUID: "xCmd"})
+	dc.Commands = append(dc.Commands, Command{UUID: "yCmd"})
+	dc.Commands = append(dc.Commands, Command{UUID: "zCmd"})
+	if err := store.Save(dc); err != nil {
+		t.Fatal(err)
+	}
+
+	ctx := context.Background()
+	resp := mdm.Response{
+		UDID:        dc.DeviceUDID,
+		CommandUUID: "xCmd",
+		Status:      "Idle",
+	}
+	for i, _ := range dc.Commands {
+		cmd, err := store.Next(ctx, resp)
+		if err != nil {
+			t.Fatalf("expected nil, but got err: %s", err)
+		}
+		if cmd == nil {
+			t.Fatal("expected cmd but got nil")
+		}
+
+		if have, want := cmd.UUID, dc.Commands[i].UUID; have != want {
+			t.Errorf("have %s, want %s, index %d", have, want, i)
+		}
+	}
+}
+
+func TestNext_zeroCommands(t *testing.T) {
+	store, teardown := setupDB(t)
+	defer teardown()
+
+	dc := &DeviceCommand{DeviceUDID: "TestDevice"}
+	if err := store.Save(dc); err != nil {
+		t.Fatal(err)
+	}
+
+	var allStatuses = []string{
+		"Acknowledged",
+		"NotNow",
+	}
+
+	ctx := context.Background()
+	for _, s := range allStatuses {
+		t.Run(s, func(t *testing.T) {
+			resp := mdm.Response{CommandUUID: s, Status: s}
+			cmd, err := store.Next(ctx, resp)
+			if err != nil {
+				t.Errorf("expected nil, but got err: %s", err)
+			}
+			if cmd != nil {
+				t.Errorf("expected nil cmd but got %s", cmd.UUID)
+			}
+		})
+	}
+
+}
+
+func setupDB(t *testing.T) (*Store, func()) {
+	f, _ := ioutil.TempFile("", "bolt-")
+	teardown := func() {
+		f.Close()
+		os.Remove(f.Name())
+	}
+
+	db, err := bolt.Open(f.Name(), 0777, nil)
+	if err != nil {
+		t.Fatalf("couldn't open bolt, err %s\n", err)
+	}
+	err = db.Update(func(tx *bolt.Tx) error {
+		_, err := tx.CreateBucketIfNotExists([]byte(DeviceCommandBucket))
+		return err
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	store := &Store{db}
+	return store, teardown
+}