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store.go
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store.go
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// Package store is a dead simple configuration manager for Go applications.
package store
import (
"bytes"
"encoding/json"
"fmt"
"io/ioutil"
"os"
"path/filepath"
"reflect"
"runtime"
"github.com/BurntSushi/toml"
"gopkg.in/yaml.v2"
)
// MarshalFunc is any marshaler.
type MarshalFunc func(v interface{}) ([]byte, error)
// UnmarshalFunc is any unmarshaler.
type UnmarshalFunc func(data []byte, v interface{}) error
var (
applicationName = ""
formats = map[string]format{}
)
type format struct {
m MarshalFunc
um UnmarshalFunc
}
func init() {
formats["json"] = format{m: json.Marshal, um: json.Unmarshal}
formats["yaml"] = format{m: yaml.Marshal, um: yaml.Unmarshal}
formats["yml"] = format{m: yaml.Marshal, um: yaml.Unmarshal}
formats["toml"] = format{
m: func(v interface{}) ([]byte, error) {
b := bytes.Buffer{}
err := toml.NewEncoder(&b).Encode(v)
return b.Bytes(), err
},
um: toml.Unmarshal,
}
}
// Init sets up a unique application name that will be used for name of the
// configuration directory on the file system. By default, Store puts all the
// config data to to $XDG_CONFIG_HOME or $HOME on Linux systems
// and to %APPDATA% on Windows.
//
// Beware: Store will panic on any sensitive calls unless you run Init inb4.
func Init(application string) {
applicationName = application
}
// Register is the way you register configuration formats, by mapping some
// file name extension to corresponding marshal and unmarshal functions.
// Once registered, the format given would be compatible with Load and Save.
func Register(extension string, m MarshalFunc, um UnmarshalFunc) {
formats[extension] = format{m, um}
}
// Load reads a configuration from `path` and puts it into `v` pointer. Store
// supports either JSON, TOML or YAML and will deduce the file format out of
// the filename (.json/.toml/.yaml). For other formats of custom extensions
// please you LoadWith.
//
// Path is a full filename, including the file extension, e.g. "foobar.json".
// If `path` doesn't exist, Load will create one and emptify `v` pointer by
// replacing it with a newly created object, derived from type of `v`.
//
// Load panics on unknown configuration formats.
func Load(path string, v interface{}) error {
if applicationName == "" {
panic("store: application name not defined")
}
if format, ok := formats[extension(path)]; ok {
return LoadWith(path, v, format.um)
}
panic("store: unknown configuration format")
}
// Save puts a configuration from `v` pointer into a file `path`. Store
// supports either JSON, TOML or YAML and will deduce the file format out of
// the filename (.json/.toml/.yaml). For other formats of custom extensions
// please you LoadWith.
//
// Path is a full filename, including the file extension, e.g. "foobar.json".
//
// Save panics on unknown configuration formats.
func Save(path string, v interface{}) error {
if applicationName == "" {
panic("store: application name not defined")
}
if format, ok := formats[extension(path)]; ok {
return SaveWith(path, v, format.m)
}
panic("store: unknown configuration format")
}
// LoadWith loads the configuration using any unmarshaler at all.
func LoadWith(path string, v interface{}, um UnmarshalFunc) error {
if applicationName == "" {
panic("store: application name not defined")
}
globalPath := buildPlatformPath(path)
data, err := ioutil.ReadFile(globalPath)
if err != nil {
// There is a chance that file we are looking for
// just doesn't exist. In this case we are supposed
// to create an empty configuration file, based on v.
empty := reflect.New(reflect.TypeOf(v))
if innerErr := Save(path, &empty); innerErr != nil {
// Smth going on with the file system... returning error.
return err
}
v = empty
return nil
}
if err := um(data, v); err != nil {
return fmt.Errorf("store: failed to unmarshal %s: %v", path, err)
}
return nil
}
// SaveWith saves the configuration using any marshaler at all.
func SaveWith(path string, v interface{}, m MarshalFunc) error {
if applicationName == "" {
panic("store: application name not defined")
}
var b bytes.Buffer
if data, err := m(v); err == nil {
b.Write(data)
} else {
return fmt.Errorf("store: failed to marshal %s: %v", path, err)
}
b.WriteRune('\n')
globalPath := buildPlatformPath(path)
if err := os.MkdirAll(filepath.Dir(globalPath), os.ModePerm); err != nil {
return err
}
if err := ioutil.WriteFile(globalPath, b.Bytes(), os.ModePerm); err != nil {
return err
}
return nil
}
func extension(path string) string {
for i := len(path) - 1; i >= 0; i-- {
if path[i] == '.' {
return path[i+1:]
}
}
return ""
}
// buildPlatformPath builds a platform-dependent path for relative path given.
func buildPlatformPath(path string) string {
if runtime.GOOS == "windows" {
return fmt.Sprintf("%s\\%s\\%s", os.Getenv("APPDATA"),
applicationName,
path)
}
var unixConfigDir string
if xdg := os.Getenv("XDG_CONFIG_HOME"); xdg != "" {
unixConfigDir = xdg
} else {
unixConfigDir = os.Getenv("HOME") + "/.config"
}
return fmt.Sprintf("%s/%s/%s", unixConfigDir,
applicationName,
path)
}
// SetApplicationName is DEPRECATED (use Init instead).
func SetApplicationName(handle string) {
applicationName = handle
}