[milo] Refactor all html knowledge out of backends.

milo/buildsource/builder.go

Index: milo/buildsource/builder.go
diff --git a/milo/buildsource/builder.go b/milo/buildsource/builder.go
new file mode 100644
index 0000000000000000000000000000000000000000..d085057cb5b856c775444a87f2f7db22e2b547d6
--- /dev/null
+++ b/milo/buildsource/builder.go
@@ -0,0 +1,97 @@
+// Copyright 2017 The LUCI Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package buildsource
+
+import (
+	"strconv"
+	"strings"
+
+	"golang.org/x/net/context"
+
+	"github.com/luci/gae/service/datastore"
+
+	"github.com/luci/luci-go/common/errors"
+	"github.com/luci/luci-go/common/logging"
+	"github.com/luci/luci-go/milo/api/resp"
+	"github.com/luci/luci-go/milo/buildsource/buildbot"
+	"github.com/luci/luci-go/milo/buildsource/buildbucket"
+	"github.com/luci/luci-go/milo/common"
+)
+
+// BuilderID is the universal ID of a builder, and has the form:
+//   buildbucket/bucket/builder
+//   buildbot/master/builder
+type BuilderID string
+
+// Split breaks the BuilderID into pieces.
+//   - backend is either 'buildbot' or 'buildbucket'
+//   - backendGroup is either the bucket or master name
+//   - builderName is the builder name.
+//
+// Returns an error if the BuilderID is malformed (wrong # slashes) or if any of
+// the pieces are empty.
+func (b BuilderID) Split() (backend, backendGroup, builderName string, err error) {
+	toks := strings.SplitN(string(b), "/", 3)
+	if len(toks) != 3 {
+		err = errors.Reason("bad BuilderID: not enough tokens: %q", b).
+			Tag(common.CodeParameterError).Err()
+		return
+	}
+	backend, backendGroup, builderName = toks[0], toks[1], toks[2]
+	switch backend {
+	case "buildbot", "buildbucket":
+	default:
+		err = errors.Reason("bad BuilderID: unknown backend %q", backend).
+			Tag(common.CodeParameterError).Err()
+		return
+	}
+	if backendGroup == "" {
+		err = errors.New("bad BuilderID: empty backendGroup", common.CodeParameterError)
+		return
+	}
+	if builderName == "" {
+		err = errors.New("bad BuilderID: empty builderName", common.CodeParameterError)
+		return
+	}
+	return
+}
+
+// Get allows you to obtain the resp.Builder that corresponds with this
+// BuilderID.
+func (b BuilderID) Get(c context.Context, limitStr string, cursorStr string) (*resp.Builder, error) {
+	// TODO(iannucci): replace these implementations with a BuildSummary query.
+
+	limit := 0
+	if limitStr != "" {
+		switch limitVal, err := strconv.ParseInt(limitStr, 10, 0); err {
+		case nil:
+			limit = int(limitVal)
+		default:
+			logging.WithError(err).Warningf(c, "ignoring bad limit %q", limitStr)
+		}
+	}
+	if limit <= 0 {
+		limit = 25
+	}
+
+	source, group, builder, err := b.Split()
+	if err != nil {
+		return nil, err
+	}
+
+	switch source {
+	case "buildbot":
+		cursor, err := datastore.DecodeCursor(c, cursorStr)
+		if err != nil {
+			return nil, errors.Annotate(err, "bad cursor").Err()
+		}
+		return buildbot.GetBuilder(c, group, builder, limit, cursor)
+
+	case "buildbucket":
+		return buildbucket.GetBuilder(c, group, builder, limit)
+	}
+
+	panic("impossible")
+}