Make jsonconfig into its own library

Will move away from camli/blobserver in future commit.

build.pl

@@ -404,6 +404,7 @@ TARGET: lib/go/camli/blobserver/s3
 TARGET: lib/go/camli/client
 TARGET: lib/go/camli/errorutil
 TARGET: lib/go/camli/httputil
+TARGET: lib/go/camli/jsonconfig
 TARGET: lib/go/camli/jsonsign
 TARGET: lib/go/camli/lru
 TARGET: lib/go/camli/magic

lib/go/camli/jsonconfig/jsonconfig.go

@@ -0,0 +1,137 @@
+/*
+Copyright 2011 Google Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package jsonconfig
+
+import (
+	"fmt"
+	"os"
+	"strings"
+)
+
+type Obj map[string]interface{}
+
+func (jc Obj) RequiredString(key string) string {
+	jc.noteKnownKey(key)
+	ei, ok := jc[key]
+	if !ok {
+		jc.appendError(fmt.Errorf("Missing required config key %q (string)", key))
+		return ""
+	}
+	s, ok := ei.(string)
+	if !ok {
+		jc.appendError(fmt.Errorf("Expected config key %q to be a string", key))
+		return ""
+	}
+	return s
+}
+
+func (jc Obj) OptionalString(key, def string) string {
+	jc.noteKnownKey(key)
+	ei, ok := jc[key]
+	if !ok {
+		return def
+	}
+	s, ok := ei.(string)
+	if !ok {
+		jc.appendError(fmt.Errorf("Expected config key %q to be a string", key))
+		return ""
+	}
+	return s
+}
+
+func (jc Obj) RequiredBool(key string) bool {
+	jc.noteKnownKey(key)
+	ei, ok := jc[key]
+	if !ok {
+		jc.appendError(fmt.Errorf("Missing required config key %q (boolean)", key))
+		return false
+	}
+	b, ok := ei.(bool)
+	if !ok {
+		jc.appendError(fmt.Errorf("Expected config key %q to be a boolean", key))
+		return false
+	}
+	return b
+}
+
+func (jc Obj) OptionalBool(key string, def bool) bool {
+	jc.noteKnownKey(key)
+	ei, ok := jc[key]
+	if !ok {
+		return def
+	}
+	b, ok := ei.(bool)
+	if !ok {
+		jc.appendError(fmt.Errorf("Expected config key %q to be a boolean", key))
+		return def
+	}
+	return b
+}
+
+func (jc Obj) noteKnownKey(key string) {
+	_, ok := jc["_knownkeys"]
+	if !ok {
+                jc["_knownkeys"] = make(map[string]bool)
+	}
+	jc["_knownkeys"].(map[string]bool)[key] = true
+}
+
+func (jc Obj) appendError(err os.Error) {
+	ei, ok := jc["_errors"]
+	if ok {
+		jc["_errors"] = append(ei.([]os.Error), err)
+	} else {
+		jc["_errors"] = []os.Error{err}
+	}
+}
+
+func (jc Obj) lookForUnknownKeys() {
+	ei, ok := jc["_knownkeys"]
+	var known map[string]bool
+	if ok {
+		known = ei.(map[string]bool)
+	}
+	for k, _ := range jc {
+		if ok && known[k] {
+			continue
+		}
+		if strings.HasPrefix(k, "_") {
+			// Permit keys with a leading underscore as a
+			// form of comments.
+			continue
+		}
+		jc.appendError(fmt.Errorf("Unknown key %q", k))
+	}
+}
+
+func (jc Obj) Validate() os.Error {
+	jc.lookForUnknownKeys()
+
+	ei, ok := jc["_errors"]
+	if !ok {
+		return nil
+	}
+	errList := ei.([]os.Error)
+	if len(errList) == 1 {
+		return errList[0]
+	}
+	strs := make([]string, 0)
+	for _, v := range errList {
+		strs = append(strs, v.String())
+	}
+	return fmt.Errorf("Multiple errors: " + strings.Join(strs, ", "))
+}