// Author: NiuJiuRu
// Email: niujiuru@qq.com

package ftpclient

import (
	"context"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"sync"
	"sync/atomic"
	"time"

	"github.com/jlaffaye/ftp"
	"hnyfkj.com.cn/rtu/linux/baseapp"
)

const MODULE_NAME = "FtpClient"

const (
	defaultRtyInterval     = 1 * time.Second
	defaultLogInterval     = 2 * time.Second
	DefaultUploadTimeout   = 5 * time.Minute
	DefaultDownloadTimeout = 5 * time.Minute
)

var (
	fileLock = struct {
		sync.Mutex
		m map[string]struct{}
	}{m: make(map[string]struct{})}

	FileUpFolder = "" // 上传文件目录

	FileUploader = struct {
		UploadLock sync.Mutex // 上传照片任务只能串行进行时, 可以通过使用该锁来实现排队串行
	}{}
)

func tryLockFile(file string) (unlock func(), ok bool) {
	fileLock.Lock()
	defer fileLock.Unlock()
	if _, ok := fileLock.m[file]; ok {
		return nil, false
	}
	fileLock.m[file] = struct{}{}
	return func() {
		fileLock.Lock()
		delete(fileLock.m, file)
		fileLock.Unlock()
	}, true
}

type progressReader struct {
	io.Reader
	filename           string
	total, transferred int64
	label              string // "上传"或"下载"
	ctx                context.Context
	doneLogged         int32
}

func newProgressReader(r io.Reader, filename string, total, transferred int64, label string, ctx context.Context) *progressReader {
	pr := &progressReader{Reader: r, filename: filename, total: total, transferred: transferred, label: label, ctx: ctx}
	go pr.startProgressLogger()
	return pr
}

func (p *progressReader) Read(buf []byte) (int, error) {
	n, err := p.Reader.Read(buf)
	if n > 0 {
		atomic.AddInt64(&p.transferred, int64(n))
	}
	if err == io.EOF && atomic.CompareAndSwapInt32(&p.doneLogged, 0, 1) {
		transferred := atomic.LoadInt64(&p.transferred)
		baseapp.Logger.Infof("[%s] 文件%q%s进度: 100.00%%, 剩余: %d字节, 总大小: %d字节", MODULE_NAME, p.filename, p.label, p.total-transferred, p.total)
	}
	return n, err
}

func (p *progressReader) startProgressLogger() {
	ticker := time.NewTicker(defaultLogInterval)
	defer ticker.Stop()

	for {
		select {
		case <-ticker.C:
			if atomic.LoadInt32(&p.doneLogged) == 1 {
				return
			}

			transferred := atomic.LoadInt64(&p.transferred)
			if transferred >= p.total {
				return
			}

			progress := float64(transferred) / float64(p.total) * 100
			baseapp.Logger.Infof("[%s] 文件%q%s进度: %.2f%%, 剩余: %d字节, 总大小: %d字节", MODULE_NAME, p.filename, p.label, progress, p.total-transferred, p.total)
		case <-p.ctx.Done():
			return
		}
	}
}

type stopError struct{ err error }

func (e *stopError) Error() string { return e.err.Error() }

func UploadFileToFtp(ctx context.Context, localFile, serverAddr, loginUser, loginPass string, timeout time.Duration) (string, error) {
	unlock, ok := tryLockFile(localFile)
	if !ok {
		return "", fmt.Errorf("文件%q正在使用中", localFile)
	}
	defer unlock()

	if ctx == nil {
		ctx = context.Background()
	}
	timeoutCtx, cancel := context.WithTimeout(ctx, timeout)
	defer cancel()

	if FileUpFolder == "" {
		return "", fmt.Errorf("无效的上传目录")
	}

	lf, err := os.Open(localFile)
	if err != nil {
		return "", err
	}
	defer lf.Close()

	info, err := lf.Stat()
	if err != nil {
		return "", err
	}
	lfs := info.Size() // 总上传的字节数

	rd := FileUpFolder                                        // 远程目录名
	remoteFile := filepath.Join(rd, filepath.Base(localFile)) // 远程文件名

	for {
		select {
		case <-timeoutCtx.Done():
			return "", timeoutCtx.Err()
		default:
		}

		err := func() error {
			c, err := ftp.Dial(serverAddr, ftp.DialWithContext(timeoutCtx))
			if err != nil {
				return &stopError{err}
			}
			defer c.Quit()

			if err := c.Login(loginUser, loginPass); err != nil {
				return &stopError{err}
			}

			_ = c.MakeDir(rd) // 尝试创建远程目录, 忽略已存在和其它错误

			rfs, err := c.FileSize(remoteFile) // 已上传的字节数
			if err != nil || rfs > lfs {
				rfs = 0
			}

			if _, err := lf.Seek(rfs, io.SeekStart); err != nil {
				return &stopError{err}
			}

			pr := newProgressReader(lf, localFile, lfs, rfs, "上传", timeoutCtx)

			if err := c.StorFrom(remoteFile, pr, uint64(rfs)); err != nil {
				return err
			}

			return nil
		}()

		if err != nil {
			if lfe, ok := err.(*stopError); ok {
				return "", lfe.err
			}
			time.Sleep(defaultRtyInterval)
			continue
		}

		return remoteFile, nil
	}
}

func DownloadFileFromFtp(ctx context.Context, serverAddr, loginUser, loginPass, remoteFile string, timeout time.Duration) (string, error) {
	unlock, ok := tryLockFile(remoteFile)
	if !ok {
		return "", fmt.Errorf("文件%q正在使用中", remoteFile)
	}
	defer unlock()

	if ctx == nil {
		ctx = context.Background()
	}
	timeoutCtx, cancel := context.WithTimeout(ctx, timeout)
	defer cancel()

	ld := baseapp.VAR_DIR                                     // 本地目录名
	localFile := filepath.Join(ld, filepath.Base(remoteFile)) // 本地文件名

	lf, err := os.OpenFile(localFile, os.O_CREATE|os.O_RDWR, 0644)
	if err != nil {
		return "", err
	}
	defer lf.Close()

	info, err := lf.Stat()
	if err != nil {
		return "", err
	}
	lfs := info.Size() // 已下载的字节数

	for {
		select {
		case <-timeoutCtx.Done():
			return "", timeoutCtx.Err()
		default:
		}

		err := func() error {
			c, err := ftp.Dial(serverAddr, ftp.DialWithContext(timeoutCtx))
			if err != nil {
				return &stopError{err}
			}
			defer c.Quit()

			if err := c.Login(loginUser, loginPass); err != nil {
				return &stopError{err}
			}

			rfs, err := c.FileSize(remoteFile) // 总下载的字节数
			if err != nil {
				return &stopError{err}
			}

			if lfs > rfs {
				lfs = 0
			}

			if _, err := lf.Seek(lfs, io.SeekStart); err != nil {
				return &stopError{err}
			}

			resp, err := c.RetrFrom(remoteFile, uint64(lfs))
			if err != nil {
				return err
			}
			defer resp.Close()

			pr := newProgressReader(resp, remoteFile, rfs, lfs, "下载", timeoutCtx)
			n, err := io.Copy(lf, pr)
			if err != nil {
				return err
			}
			lfs += n

			return nil
		}()

		if err != nil {
			if lfe, ok := err.(*stopError); ok {
				return "", lfe.err
			}
			time.Sleep(defaultRtyInterval)
			continue
		}

		return localFile, nil
	}
}