Refactor current GAE abstraction library to be free of the SDK*

go/src/infra/gae/libs/gae/helper/datastore.go

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// HEAVILY adapted from github.com/golang/appengine/datastore
+
+package helper
+
+import (
+        "fmt"
+        "infra/gae/libs/gae"

[Vadim Sh., 2015/07/13 21:17:11]

nit: group non-stdlib imports separately

[iannucci, 2015/07/13 22:39:51]

blargh I thought I got all these

+        "reflect"
+)
+
+// GetStructPLS resolves o into a gae.DSStructPLS. o must be a pointer to a
+// struct of some sort.
+func GetStructPLS(o interface{}) gae.DSStructPLS {
+        v := reflect.ValueOf(o)
+        if v.Kind() != reflect.Ptr || v.Elem().Kind() != reflect.Struct {
+                return &structPLS{c: &structCodec{problem: gae.ErrDSInvalidEntityType}}
+        }
+        v = v.Elem()
+        t := v.Type()
+
+        structCodecsMutex.RLock()
+        if c, ok := structCodecs[t]; ok {
+                structCodecsMutex.RUnlock()
+                return &structPLS{v, c}
+        }
+        structCodecsMutex.RUnlock()
+
+        structCodecsMutex.Lock()
+        defer structCodecsMutex.Unlock()
+        return &structPLS{v, getStructCodecLocked(t)}
+}
+
+// GetPLS resolves o into a gae.DSPropertyLoadSaver. If o implements the
+// gae.DSPropertyLoadSaver interface already, it's returned unchanged. Otherwise
+// this calls GetStructPLS and returns the result.
+func GetPLS(o interface{}) (gae.DSPropertyLoadSaver, error) {
+        if pls, ok := o.(gae.DSPropertyLoadSaver); ok {
+                return pls, nil
+        }
+        pls := GetStructPLS(o)
+        if err := pls.Problem(); err != nil {
+                return nil, err
+        }
+        return pls, nil
+}
+
+// MultiGetPLS resolves os to a []gae.DSPropertyLoadSaver. os must be a slice of
+// something. If os is already a []gae.DSPropertyLoadSaver, it's returned
+// unchanged. Otherwise this calls GetPLS on each item, and composes the
+// resulting slice that way.
+func MultiGetPLS(os interface{}) ([]gae.DSPropertyLoadSaver, error) {
+        if plss, ok := os.([]gae.DSPropertyLoadSaver); ok {
+                return plss, nil
+        }
+
+        v := reflect.ValueOf(os)
+        if v.Kind() != reflect.Slice {
+                return nil, fmt.Errorf("gae/helper: bad type in MultiObjToPLS: %T", os)
+        }
+
+        // TODO(riannucci): define a higher-level type DSMultiPropertyLoadSaver
+        // to avoid this slice?
+        ret := make([]gae.DSPropertyLoadSaver, v.Len())
+        for i := 0; i < v.Len(); i++ {
+                pls, err := GetPLS(v.Index(i).Interface())
+                if err != nil {
+                        return nil, err
+                }
+                ret[i] = pls
+        }
+        return ret, nil
+}