52 lines
1.3 KiB
Go
52 lines
1.3 KiB
Go
// Package configfile publishes default configuration without replacing user files.
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package configfile
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import (
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"encoding/json"
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"errors"
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"fmt"
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"log/slog"
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"os"
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"path/filepath"
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)
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// Ensure publishes a complete JSON file only when path does not exist.
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// Linking a same-directory temporary file makes publication atomic and refuses
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// to replace a configuration created by another process in the meantime.
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func Ensure(path string, defaults any) error {
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if _, err := os.Stat(path); err == nil {
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return nil
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} else if !errors.Is(err, os.ErrNotExist) {
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return err
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}
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data, err := json.MarshalIndent(defaults, "", " ")
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if err != nil {
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return err
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}
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if err = os.MkdirAll(filepath.Dir(path), 0755); err != nil {
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return fmt.Errorf("create configuration directory: %w", err)
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}
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file, err := os.CreateTemp(filepath.Dir(path), ".config-*.tmp")
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if err != nil {
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return err
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}
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defer os.Remove(file.Name())
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if _, err = file.Write(append(data, '\n')); err == nil {
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err = file.Sync()
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}
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closeErr := file.Close()
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if err != nil {
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return err
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}
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if closeErr != nil {
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return closeErr
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}
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if err = os.Link(file.Name(), path); errors.Is(err, os.ErrExist) {
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return nil
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} else if err != nil {
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return fmt.Errorf("create default configuration %s: %w", path, err)
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}
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slog.Info("default configuration created", "path", path)
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return nil
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}
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