Refactor keys and queries in datastore service and implementation.

service/datastore/index.go

Index: service/datastore/index.go
diff --git a/service/datastore/index.go b/service/datastore/index.go
index 44cb172bd05fa2c340a958a48598b5a6d1f521bf..cf26fc2b3978bf20c2696f0b422e688b5ba2e737 100644
--- a/service/datastore/index.go
+++ b/service/datastore/index.go
@@ -6,6 +6,8 @@ package datastore
 
 import (
 	"bytes"
+	"fmt"
+	"strings"
 )
 
 const MaxIndexColumns = 64
@@ -30,6 +32,23 @@ type IndexColumn struct {
 	Direction IndexDirection
 }
 
+func ParseIndexColumn(spec string) (IndexColumn, error) {
+	col := IndexColumn{}
+	if strings.HasPrefix(spec, "-") {
+		col.Direction = DESCENDING
+		col.Property = strings.TrimSpace(spec[1:])
+	} else if strings.HasPrefix(spec, "+") {
+		return col, fmt.Errorf("datastore: invalid order: %q", spec)
+	} else {
+		col.Direction = ASCENDING
+		col.Property = strings.TrimSpace(spec)
+	}
+	if col.Property == "" {
+		return col, fmt.Errorf("datastore: empty order")
+	}
+	return col, nil
+}
+
 func (i IndexColumn) cmp(o IndexColumn) int {
 	// sort ascending first
 	if i.Direction == ASCENDING && o.Direction == DESCENDING {
@@ -40,6 +59,21 @@ func (i IndexColumn) cmp(o IndexColumn) int {
 	return cmpString(i.Property, o.Property)()
 }
 
+func (i IndexColumn) String() string {
+	ret := ""
+	if i.Direction == DESCENDING {
+		ret = "-"
+	}
+	return ret + i.Property
+}
+
+func (i IndexColumn) GQL() string {
+	if i.Direction == DESCENDING {
+		return gqlQuoteName(i.Property) + " DESC"
+	}
+	return gqlQuoteName(i.Property)
+}
+
 type IndexDefinition struct {
 	Kind     string
 	Ancestor bool