Refactor a bit.

globalinfo.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.
-
-package gae
-
-import (
-        "time"
-
-        "golang.org/x/net/context"
-)
-
-// GlobalInfo is the interface for all of the package methods which normally
-// would be in the 'appengine' package.
-type GlobalInfo interface {
-        AppID() string
-        Datacenter() string
-        DefaultVersionHostname() string
-        InstanceID() string
-        IsDevAppServer() bool
-        IsOverQuota(err error) bool
-        IsTimeoutError(err error) bool
-        ModuleHostname(module, version, instance string) (string, error)
-        ModuleName() string
-        RequestID() string
-        ServerSoftware() string
-        ServiceAccount() (string, error)
-        VersionID() string
-
-        Namespace(namespace string) (context.Context, error)
-
-        AccessToken(scopes ...string) (token string, expiry time.Time, err error)
-        PublicCertificates() ([]GICertificate, error)
-        SignBytes(bytes []byte) (keyName string, signature []byte, err error)
-}
-
-// GIFactory is the function signature for factory methods compatible with
-// SetGIFactory.
-type GIFactory func(context.Context) GlobalInfo
-
-// GIFilter is the function signature for a filter GI implementation. It
-// gets the current GI implementation, and returns a new GI implementation
-// backed by the one passed in.
-type GIFilter func(context.Context, GlobalInfo) GlobalInfo
-
-// GetGIUnfiltered gets gets the GlobalInfo implementation from context without
-// any of the filters applied.
-func GetGIUnfiltered(c context.Context) GlobalInfo {
-        if f, ok := c.Value(globalInfoKey).(GIFactory); ok && f != nil {
-                return f(c)
-        }
-        return nil
-}
-
-// GetGI gets gets the GlobalInfo implementation from context.
-func GetGI(c context.Context) GlobalInfo {
-        ret := GetGIUnfiltered(c)
-        if ret == nil {
-                return nil
-        }
-        for _, f := range getCurGIFilters(c) {
-                ret = f(c, ret)
-        }
-        return ret
-}
-
-// SetGIFactory sets the function to produce GlobalInfo instances, as returned
-// by the GetGI method.
-func SetGIFactory(c context.Context, gif GIFactory) context.Context {
-        return context.WithValue(c, globalInfoKey, gif)
-}
-
-// SetGI sets the current GlobalInfo object in the context. Useful for testing
-// with a quick mock. This is just a shorthand SetGIFactory invocation to set
-// a factory which always returns the same object.
-func SetGI(c context.Context, gi GlobalInfo) context.Context {
-        return SetGIFactory(c, func(context.Context) GlobalInfo { return gi })
-}
-
-func getCurGIFilters(c context.Context) []GIFilter {
-        curFiltsI := c.Value(globalInfoFilterKey)
-        if curFiltsI != nil {
-                return curFiltsI.([]GIFilter)
-        }
-        return nil
-}
-
-// AddGIFilters adds GlobalInfo filters to the context.
-func AddGIFilters(c context.Context, filts ...GIFilter) context.Context {
-        if len(filts) == 0 {
-                return c
-        }
-        cur := getCurGIFilters(c)
-        newFilts := make([]GIFilter, 0, len(cur)+len(filts))
-        newFilts = append(newFilts, getCurGIFilters(c)...)
-        newFilts = append(newFilts, filts...)
-        return context.WithValue(c, globalInfoFilterKey, newFilts)
-}