136 lines
4.3 KiB
Go
136 lines
4.3 KiB
Go
// Mgmt
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// Copyright (C) 2013-2017+ James Shubin and the project contributors
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// Written by James Shubin <james@shubin.ca> and the project contributors
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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package resources
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import (
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"bytes"
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"encoding/base64"
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"encoding/gob"
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"fmt"
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"reflect"
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"sort"
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"strings"
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errwrap "github.com/pkg/errors"
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)
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const (
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// StructTag is the key we use in struct field names for key mapping.
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StructTag = "lang"
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)
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// ResourceSlice is a linear list of resources. It can be sorted.
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type ResourceSlice []Res
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func (rs ResourceSlice) Len() int { return len(rs) }
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func (rs ResourceSlice) Swap(i, j int) { rs[i], rs[j] = rs[j], rs[i] }
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func (rs ResourceSlice) Less(i, j int) bool { return rs[i].String() < rs[j].String() }
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// Sort the list of resources and return a copy without modifying the input.
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func Sort(rs []Res) []Res {
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resources := []Res{}
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for _, r := range rs { // copy
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resources = append(resources, r)
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}
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sort.Sort(ResourceSlice(resources))
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return resources
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// sort.Sort(ResourceSlice(rs)) // this is wrong, it would modify input!
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//return rs
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}
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// ResToB64 encodes a resource to a base64 encoded string (after serialization).
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func ResToB64(res Res) (string, error) {
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b := bytes.Buffer{}
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e := gob.NewEncoder(&b)
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err := e.Encode(&res) // pass with &
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if err != nil {
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return "", errwrap.Wrapf(err, "gob failed to encode")
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}
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return base64.StdEncoding.EncodeToString(b.Bytes()), nil
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}
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// B64ToRes decodes a resource from a base64 encoded string (after deserialization).
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func B64ToRes(str string) (Res, error) {
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var output interface{}
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bb, err := base64.StdEncoding.DecodeString(str)
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if err != nil {
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return nil, errwrap.Wrapf(err, "base64 failed to decode")
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}
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b := bytes.NewBuffer(bb)
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d := gob.NewDecoder(b)
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err = d.Decode(&output) // pass with &
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if err != nil {
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return nil, errwrap.Wrapf(err, "gob failed to decode")
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}
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res, ok := output.(Res)
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if !ok {
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return nil, fmt.Errorf("output `%v` is not a Res", output)
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}
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return res, nil
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}
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// StructTagToFieldName returns a mapping from recommended alias to actual field
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// name. It returns an error if it finds a collision. It uses the `lang` tags.
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func StructTagToFieldName(res Res) (map[string]string, error) {
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// TODO: fallback to looking up yaml tags, although harder to parse
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result := make(map[string]string) // `lang` field tag -> field name
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st := reflect.TypeOf(res).Elem() // elem for ptr to res
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for i := 0; i < st.NumField(); i++ {
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field := st.Field(i)
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name := field.Name
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// TODO: golang 1.7+
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// if !ok, then nothing is found
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//if alias, ok := field.Tag.Lookup(StructTag); ok { // golang 1.7+
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if alias := field.Tag.Get(StructTag); alias != "" { // golang 1.6
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if val, exists := result[alias]; exists {
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return nil, fmt.Errorf("field `%s` uses the same key `%s` as field `%s`", name, alias, val)
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}
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// empty string ("") is a valid value
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if alias != "" {
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result[alias] = name
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}
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}
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}
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return result, nil
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}
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// LowerStructFieldNameToFieldName returns a mapping from the lower case version
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// of each field name to the actual field name. It only returns public fields.
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// It returns an error if it finds a collision.
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func LowerStructFieldNameToFieldName(res Res) (map[string]string, error) {
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result := make(map[string]string) // lower field name -> field name
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st := reflect.TypeOf(res).Elem() // elem for ptr to res
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for i := 0; i < st.NumField(); i++ {
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field := st.Field(i)
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name := field.Name
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if strings.Title(name) != name { // must have been a priv field
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continue
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}
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if alias := strings.ToLower(name); alias != "" {
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if val, exists := result[alias]; exists {
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return nil, fmt.Errorf("field `%s` uses the same key `%s` as field `%s`", name, alias, val)
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}
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result[alias] = name
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}
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}
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return result, nil
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}
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