[milo] Refactor all html knowledge out of backends.

milo/buildsource/builder.go

+// 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")
+}