forked from ebhomengo/niki
99 lines
2.7 KiB
Go
99 lines
2.7 KiB
Go
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// Package env implements a koanf.Provider that reads environment
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// variables as conf maps.
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package env
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import (
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"errors"
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"os"
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"strings"
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"github.com/knadh/koanf/maps"
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)
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// Env implements an environment variables provider.
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type Env struct {
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prefix string
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delim string
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cb func(key string, value string) (string, interface{})
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}
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// Provider returns an environment variables provider that returns
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// a nested map[string]interface{} of environment variable where the
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// nesting hierarchy of keys is defined by delim. For instance, the
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// delim "." will convert the key `parent.child.key: 1`
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// to `{parent: {child: {key: 1}}}`.
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//
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// If prefix is specified (case-sensitive), only the env vars with
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// the prefix are captured. cb is an optional callback that takes
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// a string and returns a string (the env variable name) in case
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// transformations have to be applied, for instance, to lowercase
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// everything, strip prefixes and replace _ with . etc.
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// If the callback returns an empty string, the variable will be
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// ignored.
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func Provider(prefix, delim string, cb func(s string) string) *Env {
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e := &Env{
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prefix: prefix,
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delim: delim,
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}
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if cb != nil {
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e.cb = func(key string, value string) (string, interface{}) {
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return cb(key), value
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}
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}
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return e
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}
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// ProviderWithValue works exactly the same as Provider except the callback
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// takes a (key, value) with the variable name and value and allows you
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// to modify both. This is useful for cases where you may want to return
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// other types like a string slice instead of just a string.
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func ProviderWithValue(prefix, delim string, cb func(key string, value string) (string, interface{})) *Env {
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return &Env{
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prefix: prefix,
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delim: delim,
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cb: cb,
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}
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}
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// ReadBytes is not supported by the env provider.
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func (e *Env) ReadBytes() ([]byte, error) {
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return nil, errors.New("env provider does not support this method")
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}
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// Read reads all available environment variables into a key:value map
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// and returns it.
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func (e *Env) Read() (map[string]interface{}, error) {
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// Collect the environment variable keys.
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var keys []string
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for _, k := range os.Environ() {
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if e.prefix != "" {
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if strings.HasPrefix(k, e.prefix) {
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keys = append(keys, k)
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}
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} else {
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keys = append(keys, k)
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}
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}
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mp := make(map[string]interface{})
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for _, k := range keys {
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parts := strings.SplitN(k, "=", 2)
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// If there's a transformation callback,
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// run it through every key/value.
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if e.cb != nil {
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key, value := e.cb(parts[0], parts[1])
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// If the callback blanked the key, it should be omitted
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if key == "" {
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continue
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}
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mp[key] = value
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} else {
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mp[parts[0]] = parts[1]
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}
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}
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return maps.Unflatten(mp, e.delim), nil
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}
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