gol4ng/logger

package provider

import (
    "fmt"
    "io"
    "os"
    "time"

    "github.com/gol4ng/logger/writer"
)

// LogFileProvider creates one static file with the given name and format
// if the file name already exists, it renames it with the time and create a new static file
//
// ex: LogFileProvider("dev", os.TempDir()+"/my_app_%s.log", "2006-01-02") will create a file named "/tmp/my_app_dev.log"
// and each time the provider is called, it will backup the current "/tmp/dev.log" to "/tmp/my_app_2006-01-02.log"
func LogFileProvider(name string, format string, timeFormat string) writer.Provider {
    basePath := fmt.Sprintf(format, name)
    return func(w io.Writer) (io.Writer, error) {
        if w != nil {
            if err := os.Rename(basePath, fmt.Sprintf(format, time.Now().Format(timeFormat))); err != nil {
                return nil, err
            }
            if _w, ok := w.(io.Closer); ok {
                if err := _w.Close(); err != nil {
                    return nil, err
                }
            }
        }
        return os.OpenFile(
            basePath,
            os.O_CREATE|os.O_APPEND|os.O_WRONLY,
            0666,
        )
    }
}