nix-amer/internal/cnf/loader.go

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package cnf
import (
"errors"
"fmt"
"io"
"os"
"path/filepath"
)
var ErrUnknownExtension = errors.New("unknown extension format")
var ErrUnknownFormat = errors.New("cannot infer format from content")
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// Load the current file and create the configuration format accordingly
func Load(path string) (ConfigurationFormat, error) {
var confFormat ConfigurationFormat
// 1. check file
if _, err := os.Stat(path); os.IsNotExist(err) {
return nil, fmt.Errorf("cannot find file '%s'", path)
}
// 2. Try to load from extension
extension := filepath.Ext(path)
if len(extension) > 0 {
confFormat = loadFromExtension(extension)
if confFormat == nil {
return nil, ErrUnknownExtension
}
// open file
file, err := os.Open(path)
if err != nil {
return nil, err
}
defer file.Close()
// parse
_, err = confFormat.ReadFrom(file)
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if err != nil {
return nil, fmt.Errorf("cannot parse file as '%s' | %s", extension, err)
}
return confFormat, nil
}
// 3. open file
file, err := os.Open(path)
if err != nil {
return nil, err
}
defer file.Close()
// 4. Try to guess from the content
confFormat = loadFromContent(file)
if confFormat == nil {
return nil, ErrUnknownFormat
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}
return confFormat, nil
}
func loadFromExtension(ext string) ConfigurationFormat {
// select configuration or fail if not known
switch ext {
case ".json":
return new(json)
case ".ini":
return new(ini)
case ".yaml":
return new(yaml)
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case ".conf":
return new(confl)
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default:
return nil
}
}
func loadFromContent(file io.Reader) ConfigurationFormat {
return nil
}