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52 lines
1.1 KiB
52 lines
1.1 KiB
// Package cfg implements a simple wrapper around go's flag package, in order to
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// implement initialization hooks.
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package cfg
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import (
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"context"
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"flag"
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"os"
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)
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// Cfger is a component which can be used with Cfg to setup its initialization.
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type Cfger interface {
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SetupCfg(*Cfg)
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}
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// Cfg is a wrapper around the stdlib's FlagSet and a set of initialization
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// hooks.
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type Cfg struct {
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*flag.FlagSet
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hooks []func(ctx context.Context) error
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}
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// New initializes and returns a new instance of *Cfg.
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func New() *Cfg {
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return &Cfg{
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FlagSet: flag.NewFlagSet("", flag.ExitOnError),
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}
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}
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// OnInit appends the given callback to the sequence of hooks which will run on
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// a call to Init.
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func (c *Cfg) OnInit(cb func(context.Context) error) {
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c.hooks = append(c.hooks, cb)
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}
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// Init runs all hooks registered using OnInit, in the same order OnInit was
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// called. If one returns an error that error is returned and no further hooks
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// are run.
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func (c *Cfg) Init(ctx context.Context) error {
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if err := c.FlagSet.Parse(os.Args[1:]); err != nil {
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return err
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}
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for _, h := range c.hooks {
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if err := h(ctx); err != nil {
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return err
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}
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}
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return nil
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}
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