package logs

import (
	"fmt"
	"os"
	"path"
	"strings"
	"time"
)

type rolling struct {
	name    string
	ext     string
	maxSize int64
	size    int64
	bs      chan []byte
	file    *os.File
}

func newRolling(file string, maxSize int64) *rolling {
	ext := path.Ext(file)
	if ext == "" {
		ext = ".log"
	}

	size := 100
	i := strings.LastIndex(file, ext)
	r := &rolling{
		name:    file[0:i],
		ext:     ext,
		maxSize: maxSize,
		bs:      make(chan []byte, size),
	}

	r.updateFile(0)

	go r.rolling()

	return r
}

func (p *rolling) updateFile(num int) {
	logFile, err := os.OpenFile(
		fmt.Sprintf("%s_%03d%s", time.Now().Format(p.name), num, p.ext),
		os.O_RDWR|os.O_CREATE|os.O_APPEND,
		0766,
	)
	if err != nil {
		panic(err)
	}

	s, err := logFile.Stat()
	if err != nil {
		panic(err)
	}

	if s.Size() > p.maxSize {
		logFile.Close()
		p.updateFile(num + 1)

		return
	}

	p.size = s.Size()
	p.file = logFile
}

func (p *rolling) rolling() {
	for {
		bs := <-p.bs
		p.size += int64(len(bs))

		if p.size > p.maxSize {
			p.updateFile(0)
		}

		_, _ = p.file.Write(bs)
	}
}

// Write 写入.
func (p *rolling) Write(bs []byte) (n int, err error) {
	p.bs <- bs

	return len(bs), nil
}

func (p *rolling) Close() error {
	return p.file.Close()
}