package loader

import (
	"errors"
	"gitee.com/h79/goutils/common/file"
	"os"
)

type Filer struct {
	Loader
	path           string
	lastModifyTime int64
	da             Data
}

func NewFiler(path string, format string, data Data) *Loader {
	l := &Filer{
		Loader: initLoader(),
		path:   path,
		da:     data,
	}
	return l.WithFormat(format).WithLoadFunc(l.load)
}

func (f *Filer) load() (Data, error) {
	lastModify, data, err := LoadFile(f.path, f.lastModifyTime, func(v []byte) (Data, error) {
		er := f.unmarshal.Unmarshal(v, f.da)
		return f.da, er
	})
	f.lastModifyTime = lastModify
	return data, err
}

type DecodeFunc func(v []byte) (Data, error)

func LoadFile(path string, lastModifyTime int64, decoder DecodeFunc) (int64, Data, error) {

	f, er := os.Open(path)
	if er != nil {
		return lastModifyTime, nil, er
	}
	defer f.Close()
	fileInfo, err := f.Stat()
	if err != nil {
		return lastModifyTime, nil, err
	}
	curModifyTime := fileInfo.ModTime().Unix()
	if curModifyTime > lastModifyTime {
		body, err := file.ReadFile(f)
		if err != nil {
			return lastModifyTime, nil, err
		}
		data, err := decoder(body)
		if err != nil {
			return lastModifyTime, nil, err
		}
		lastModifyTime = curModifyTime
		return lastModifyTime, data, nil
	}
	return lastModifyTime, nil, ErrNoModified
}

var ErrNoModified = errors.New("file not modified")