Add 'user friendly' datastore API.

service/datastore/datastore.go

Index: service/datastore/datastore.go
diff --git a/service/datastore/datastore.go b/service/datastore/datastore.go
new file mode 100644
index 0000000000000000000000000000000000000000..b2169038ac9e85dcea5248d716cc7e593855eb9d
--- /dev/null
+++ b/service/datastore/datastore.go
@@ -0,0 +1,200 @@
+// 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.
+
+package datastore
+
+import (
+	"fmt"
+	"reflect"
+
+	"github.com/luci/luci-go/common/errors"
+)
+
+type datastoreImpl struct{ RawInterface }
+
+var _ Interface = (*datastoreImpl)(nil)
+
+func (d *datastoreImpl) NewKeyObj(src interface{}) Key {
+	ret, err := d.NewKeyObjErr(src)
+	if err != nil {
+		panic(err)
+	}
+	return ret
+}
+
+func (d *datastoreImpl) NewKeyObjErr(src interface{}) (Key, error) {
+	return newKeyObjErr(d.NewKey, src)
+}
+
+func (d *datastoreImpl) Run(q Query, proto interface{}, cb RunCB) error {
+	if _, ok := proto.(*Key); ok {
+		return d.RawInterface.Run(q.KeysOnly(), func(k Key, _ PropertyMap, gc func() (Cursor, error)) bool {
+			return cb(k, gc)
+		})
+	}
+
+	t := reflect.TypeOf(proto)
+	if t.Kind() != reflect.Ptr {
+		return fmt.Errorf("invalid Run proto type: %T", proto)
+	}
+	e := t.Elem()
+	var mkPLS func() (interface{}, PropertyLoadSaver)
+	if t.Implements(typeOfPropertyLoadSaver) {
+		mkPLS = func() (interface{}, PropertyLoadSaver) {
+			iface := reflect.New(e).Interface()
+			return iface, iface.(PropertyLoadSaver)
+		}
+	} else if e.Kind() == reflect.Struct {
+		cdc := getCodec(e)
+		mkPLS = func() (interface{}, PropertyLoadSaver) {
+			ptr := reflect.New(e)
+			return ptr.Interface(), &structPLS{ptr.Elem(), cdc}
+		}
+	}
+	if mkPLS == nil {
+		return fmt.Errorf("invalid Run proto type: %T", proto)
+	}
+
+	innerErr := error(nil)
+	err := d.RawInterface.Run(q, func(k Key, pm PropertyMap, gc func() (Cursor, error)) bool {
+		iface, pls := mkPLS()
+		if innerErr = pls.Load(pm); innerErr != nil {
+			return false
+		}
+		setKey(pls, k)
+		return cb(iface, gc)
+	})
+	if err == nil {
+		err = innerErr

[Vadim Sh., 2015/07/29 16:21:43]

are you sure you want to return error(nil) instead of nil?..

[iannucci, 2015/08/03 03:56:31]

pretty sure it's the same thing.  `innerErr := error(nil)` is the same as `var
innerErr error`.

I do this because innerErr may have been assigned in the callback above.

+	}
+	return err
+}
+
+func (d *datastoreImpl) GetAll(q Query, dst interface{}) error {
+	v := reflect.ValueOf(dst)
+	if v.IsNil() {
+		return errors.New("invalid GetAll dst: <nil>")
+	}
+
+	t := v.Type()
+	if t.Kind() != reflect.Ptr || t.Elem().Kind() != reflect.Slice {
+		return fmt.Errorf("invalid GetAll dst: must have a ptr-to-slice %T", dst)
+	}
+
+	if keys, ok := dst.(*[]Key); ok {
+		return d.RawInterface.Run(q.KeysOnly(), func(k Key, _ PropertyMap, _ func() (Cursor, error)) bool {
+			*keys = append(*keys, k)
+			return true
+		})
+	}
+
+	slice := v.Elem()
+	mat := parseArg(t.Elem())
+	if !mat.valid || mat.newElem == nil {
+		return fmt.Errorf("invalid GetAll input type: %T", dst)
+	}
+
+	lme := errors.LazyMultiError{Size: slice.Len()}
+	i := 0
+	err := d.RawInterface.Run(q, func(k Key, pm PropertyMap, _ func() (Cursor, error)) bool {
+		itm := mat.newElem()
+		slice.Set(reflect.Append(slice, itm))
+		mat.setKey(itm, k)
+		lme.Assign(i, mat.setPM(itm, pm))
+		i++
+		return true
+	})
+	if err == nil {
+		err = lme.Get()
+	}
+	return err
+}
+
+func (d *datastoreImpl) Get(dst interface{}) (err error) {
+	return errors.SingleError(d.GetMulti([]interface{}{dst}))
+}
+
+func (d *datastoreImpl) Put(src interface{}) (err error) {
+	return errors.SingleError(d.PutMulti([]interface{}{src}))
+}
+
+func (d *datastoreImpl) Delete(key Key) (err error) {
+	return errors.SingleError(d.DeleteMulti([]Key{key}))
+}
+
+func (d *datastoreImpl) GetMulti(dst interface{}) error {
+	slice := reflect.ValueOf(dst)
+	mat := parseMultiArg(slice.Type())
+	if !mat.valid {
+		return fmt.Errorf("invalid GetMulti input type: %T", dst)
+	}
+
+	keys, err := mat.GetKeys(d.NewKey, slice)
+	if err != nil {
+		return err
+	}
+
+	lme := errors.LazyMultiError{Size: len(keys)}
+	i := 0
+	err = d.RawInterface.GetMulti(keys, func(pm PropertyMap, err error) {
+		if !lme.Assign(i, err) {
+			lme.Assign(i, mat.setPM(slice.Index(i), pm))
+		}
+		i++
+	})
+
+	if err == nil {
+		err = lme.Get()
+	}
+	return err
+}
+
+func (d *datastoreImpl) PutMulti(src interface{}) error {
+	slice := reflect.ValueOf(src)
+	mat := parseMultiArg(slice.Type())
+	if !mat.valid {
+		return fmt.Errorf("invalid PutMulti input type: %T", src)
+	}
+
+	keys, err := mat.GetKeys(d.NewKey, slice)
+	if err != nil {
+		return err
+	}
+
+	vals, err := mat.GetPMs(slice)
+	if err != nil {
+		return err
+	}
+
+	lme := errors.LazyMultiError{Size: len(keys)}
+	i := 0
+	err = d.RawInterface.PutMulti(keys, vals, func(key Key, err error) {
+		mat.setKey(slice.Index(i), key)
+		lme.Assign(i, err)
+		i++
+	})
+
+	if err == nil {
+		err = lme.Get()
+	}
+	return err
+}
+
+func (d *datastoreImpl) DeleteMulti(keys []Key) (err error) {
+	lme := errors.LazyMultiError{Size: len(keys)}
+	i := 0
+	extErr := d.RawInterface.DeleteMulti(keys, func(internalErr error) {
+		lme.Assign(i, internalErr)
+		i++
+	})
+	err = lme.Get()
+	if err == nil {
+		err = extErr
+	}
+	return
+}
+
+func (d *datastoreImpl) Raw() RawInterface {
+	return d.RawInterface
+}