package mget

import (
	"b612.me/stario"
	"b612.me/starnet"
	"b612.me/staros"
	"context"
	"encoding/json"
	"fmt"
	"os"
	"strconv"
	"strings"
	"sync"
	"sync/atomic"
	"time"
)

type Mget struct {
	Setting starnet.Request
	Redo
	//本地文件地址
	Tareget string
	//本地文件大小
	TargetSize int64
	//redo文件最大丢数据量
	RedoRPO int
	//单个buffer大小
	BufferSize int
	//并发下载线程数
	dynLength     bool
	Thread        int `json:"thread"`
	tf            *os.File
	ch            chan Buffer
	ctx           context.Context
	fn            context.CancelFunc
	wg            sync.WaitGroup
	threads       []*downloader
	lastUndoInfo  []Range
	writeError    error
	writeEnable   bool
	processEnable bool
	speedlimit    int64
}

type Buffer struct {
	Data  []byte
	Start uint64
}

func (w *Mget) Clone() *starnet.Request {
	req := starnet.NewSimpleRequest(w.Setting.Uri(), w.Setting.Method())
	req.SetHeaders(CloneHeader(w.Setting.Headers()))
	req.SetCookies(CloneCookies(w.Setting.Cookies()))
	req.SetSkipTLSVerify(w.Setting.SkipTLSVerify())
	req.SetProxy(w.Setting.Proxy())
	return req
}

func (w *Mget) IsUrl206() (*starnet.Response, bool, error) {
	req := w.Clone()
	req.SetHeader("Range", "bytes=0-")
	res, err := req.Do()
	if err != nil {
		return nil, false, err
	}
	if res.StatusCode == 206 {
		return res, true, nil
	}
	return res, false, nil
}

func (w *Mget) prepareRun(res *starnet.Response, is206 bool) error {
	var err error

	length := res.Header.Get("Content-Length")
	if length == "" {
		length = "0"
		w.dynLength = true
		is206 = false
	}
	w.TargetSize, err = strconv.ParseInt(length, 10, 64)
	if err != nil {
		return fmt.Errorf("parse content length error: %w", err)
	}
	if w.Tareget == "" {
		w.Tareget = GetFileName(res.Response)
	}
	fmt.Println("Will write to:", w.Tareget)
	fmt.Println("Size:", w.TargetSize)
	fmt.Println("Is206:", is206)
	w.Redo = Redo{
		Filename:      w.Tareget,
		ContentLength: uint64(w.TargetSize),
		OriginUri:     w.Setting.Uri(),
		Date:          time.Now(),
		Is206:         is206,
	}
	fmt.Println("Threads:", w.Thread)
	if staros.Exists(w.Tareget + ".bgrd") {
		fmt.Println("Found redo file, try to recover...")
		var redo Redo
		data, err := os.ReadFile(w.Tareget + ".bgrd")
		if err != nil {
			return fmt.Errorf("read redo file error: %w", err)
		}
		err = json.Unmarshal(data, &redo)
		if err != nil {
			return fmt.Errorf("unmarshal redo file error: %w", err)
		}
		redo.reform()
		if redo.ContentLength != w.Redo.ContentLength {
			fmt.Println("Content length not match, redo file may be invalid, ignore it")
			return nil
		}
		if redo.OriginUri != w.Redo.OriginUri {
			fmt.Println("Origin uri not match, redo file may be invalid, ignore it")
			return nil
		}
		w.Redo = redo
		w.Redo.isRedo = true
		w.lastUndoInfo, err = w.Redo.ReverseRange()
		if err != nil {
			return fmt.Errorf("reverse redo range error: %w", err)
		}
		fmt.Println("Recover redo file success,process:", w.Redo.FormatPercent())
	}
	return nil
}

func (w *Mget) Run() error {
	var err error
	var res *starnet.Response
	var is206 bool
	w.ctx, w.fn = context.WithCancel(context.Background())
	w.ch = make(chan Buffer)
	defer w.fn()
	w.threads = make([]*downloader, w.Thread)
	if w.Setting.Uri() == "" {
		w.Setting = *starnet.NewSimpleRequest(w.OriginUri, "GET")
	}
	for {
		res, is206, err = w.IsUrl206()
		if err != nil {
			return fmt.Errorf("check 206 error: %w", err)
		}
		err = w.prepareRun(res, is206)
		if err != nil {
			return fmt.Errorf("prepare run error: %w", err)
		}
		if res.StatusCode != 206 && res.StatusCode != 200 {
			return fmt.Errorf("Server return %d", res.StatusCode)
		}
		if !is206 {
			var di = &downloader{
				alive: true,
				downloadinfo: &downloadinfo{
					Start: 0,
					End:   w.TargetSize - 1,
					Size:  w.TargetSize,
				},
			}
			w.threads[0] = di
			state := uint32(0)
			err = IOWriter(w.ctx, w.ch, &state, di.downloadinfo, res.Body().Reader(), w.BufferSize, &di.Start, &di.End)
			di.alive = false
			if err == nil {
				return nil
			}
			continue
		} else {
			res.Body().Close()
		}
		break
	}
	go func() {
		w.writeEnable = true
		w.writeError = w.WriteServer()
		w.writeEnable = false
	}()
	if w.TargetSize == 0 {
		return nil
	}
	for i := 0; i < w.Thread; i++ {
		w.wg.Add(1)
		go w.dispatch(i)
	}
	go w.Process()
	w.wg.Wait()
	time.Sleep(2 * time.Microsecond)
	for {
		if w.writeEnable {
			w.fn()
			time.Sleep(time.Millisecond * 50)
			continue
		}
		if w.writeError != nil {
			err = w.Redo.Save()
			return fmt.Errorf("write error: %w %v", w.writeError, err)
		}
		break
	}
	w.fn()
	stario.WaitUntilTimeout(time.Second*2,
		func(c chan struct{}) error {
			for {
				if w.processEnable {
					time.Sleep(time.Millisecond * 50)
					continue
				}
				return nil
			}
		})

	r, err := w.ReverseRange()
	if err != nil {
		return err
	}
	if len(r) == 0 {
		return os.Remove(w.Tareget + ".bgrd")
	}
	return w.Redo.Save()
}

func (w *Mget) dispatch(idx int) error {
	defer w.wg.Done()
	var start, end int64
	if len(w.lastUndoInfo) == 0 {
		count := w.TargetSize / int64(w.Thread)
		start = count * int64(idx)
		end = count*int64(idx+1) - 1
		if idx == w.Thread-1 {
			end = w.TargetSize - 1
		}
	} else {
		w.Lock()
		if len(w.lastUndoInfo) == 0 {
			d := &downloader{}
			w.threads[idx] = d
			w.Unlock()
			goto morejob
		}
		start = int64(w.lastUndoInfo[0].Min)
		end = int64(w.lastUndoInfo[0].Max)
		w.lastUndoInfo = w.lastUndoInfo[1:]
		w.Unlock()
	}
	for {
		req := w.Clone()
		req.SetCookies(CloneCookies(w.Setting.Cookies()))
		d := &downloader{
			Request:    req,
			ch:         w.ch,
			ctx:        w.ctx,
			bufferSize: w.BufferSize,
			downloadinfo: &downloadinfo{
				Start: start,
				End:   end,
			},
		}
		w.threads[idx] = d
		if err := d.Run(); err != nil {
			fmt.Printf("thread %d error: %v\n", idx, err)
			if d.Start >= d.End {
				break
			}
			start = d.Start
			end = d.End
			continue
		}
		break
	}
morejob:
	for {
		w.Lock()
		if len(w.lastUndoInfo) > 0 {
			w.threads[idx].Start = int64(w.lastUndoInfo[idx].Min)
			w.threads[idx].End = int64(w.lastUndoInfo[idx].Max)
			w.lastUndoInfo = w.lastUndoInfo[1:]
			w.Unlock()
		} else {
			w.Unlock()
			if !w.RequestNewTask(w.threads[idx]) {
				break
			}
		}
		for {
			req := w.Clone()
			req.SetCookies(CloneCookies(w.Setting.Cookies()))
			d := &downloader{
				Request:    req,
				ch:         w.ch,
				ctx:        w.ctx,
				bufferSize: w.BufferSize,
				downloadinfo: &downloadinfo{
					Start: w.threads[idx].Start,
					End:   w.threads[idx].End,
				},
			}
			w.threads[idx] = d
			if err := d.Run(); err != nil {
				fmt.Printf("thread %d error: %v\n", idx, err)
				if d.Start >= d.End {
					break
				}
				start = d.Start
				end = d.End
				continue
			}
			break
		}
	}
	return nil
}

func (w *Mget) getSleepTime() time.Duration {
	if w.speedlimit == 0 {
		return 0
	}
	return time.Nanosecond * time.Duration(16384*1000*1000*1000/w.speedlimit) / 2

}
func (w *Mget) WriteServer() error {
	var err error
	defer w.fn()
	if !w.isRedo {
		w.tf, err = createFileWithSize(w.Tareget, w.TargetSize)
	} else {
		w.tf, err = os.OpenFile(w.Tareget, os.O_RDWR, 0666)
	}
	if err != nil {
		return err
	}

	lastUpdateRange := 0
	currentRange := 0

	currentCount := int64(0)
	lastDate := time.Now()
	lastCount := int64(0)
	speedControl := func(count int) {
		if w.speedlimit == 0 {
			return
		}
		currentCount += int64(count)
		for {
			if time.Since(lastDate) < time.Second {
				if currentCount-lastCount > w.speedlimit {
					time.Sleep(w.getSleepTime())
				} else {
					break
				}
			} else {
				lastDate = time.Now()
				lastCount = currentCount
				break
			}
		}
	}
	for {
		select {
		case <-w.ctx.Done():
			return nil
		case b := <-w.ch:
			n, err := w.tf.WriteAt(b.Data, int64(b.Start))
			if err != nil {
				fmt.Println("write error:", err)
				return err
			}
			speedControl(n)
			if w.dynLength {
				w.ContentLength += uint64(n)
			}
			currentRange += n
			end := b.Start + uint64(n) - 1
			err = w.Update(int(b.Start), int(end))
			if err != nil {
				return err
			}
			if currentRange-lastUpdateRange >= w.RedoRPO {
				w.tf.Sync()
				go w.Redo.Save()
				lastUpdateRange = currentRange
			}
		}
	}
}

type downloader struct {
	*starnet.Request
	alive      bool
	ch         chan Buffer
	ctx        context.Context
	state      uint32
	bufferSize int
	*downloadinfo
}

func (d *downloader) Run() error {
	d.alive = true
	defer func() {
		d.alive = false
	}()
	d.SetHeader("Range", fmt.Sprintf("bytes=%d-%d", d.Start, d.End))
	res, err := d.Do()
	if err != nil {
		return err
	}
	if res.Header.Get("Content-Range") == "" {
		return fmt.Errorf("server not support range")
	}
	start, end, _, err := parseContentRange(res.Header.Get("Content-Range"))
	if d.Start != start {
		return fmt.Errorf("server not support range")
	}
	d.End = end
	d.downloadinfo = &downloadinfo{
		Start: d.Start,
		End:   d.End,
		Size:  d.End - d.Start + 1,
	}
	reader := res.Body().Reader()
	return IOWriter(d.ctx, d.ch, &d.state, d.downloadinfo, reader, d.bufferSize, &d.Start, &d.End)
}

func (w *Mget) RequestNewTask(task *downloader) bool {
	//stop thhe world first
	w.Lock()
	defer w.Unlock()
	defer func() {
		for _, v := range w.threads {
			if v != nil {
				atomic.StoreUint32(&v.state, 0)
			}
		}
	}()
	var maxThread *downloader
	for _, v := range w.threads {
		if v != nil {
			atomic.StoreUint32(&v.state, 1)
		}
	}
	time.Sleep(time.Microsecond * 2)

	for _, v := range w.threads {
		if v == nil {
			continue
		}
		if maxThread == nil {
			maxThread = v
			continue
		}
		if v.End-v.Start > maxThread.End-maxThread.Start {
			maxThread = v
		}
	}
	if maxThread == nil || maxThread.End <= maxThread.Start {
		return false
	}
	if (maxThread.End-maxThread.Start)/2 < int64(w.BufferSize*2) || (maxThread.End-maxThread.Start)/2 < 100*1024 {
		return false
	}
	task.End = maxThread.End
	maxThread.End = maxThread.Start + (maxThread.End-maxThread.Start)/2
	task.Start = maxThread.End + 1
	//fmt.Printf("thread got new task %d-%d\n", task.Start, task.End)
	return true
}

type downloadinfo struct {
	Start       int64
	End         int64
	Size        int64
	current     int64
	lastCurrent int64
	lastTime    time.Time
	speed       float64
}

func (d *downloadinfo) Current() int64 {
	return d.current
}

func (d *downloadinfo) Percent() float64 {
	return float64(d.current) / float64(d.Size)
}

func (d *downloadinfo) FormatPercent() string {
	return fmt.Sprintf("%.2f%%", d.Percent()*100)
}

func (d *downloadinfo) SetCurrent(info int64) {
	d.current = info
	now := time.Now()
	if now.Sub(d.lastTime) >= time.Millisecond*500 {
		d.speed = float64(d.current-d.lastCurrent) / (float64(now.Sub(d.lastTime).Milliseconds()) / 1000.00)
		d.lastCurrent = d.current
		d.lastTime = time.Now()
	}
}

func (d *downloadinfo) AddCurrent(info int64) {
	d.current += info
	now := time.Now()
	if now.Sub(d.lastTime) >= time.Millisecond*500 {
		d.speed = float64(d.current-d.lastCurrent) / (float64(now.Sub(d.lastTime).Milliseconds()) / 1000.00)
		d.lastCurrent = d.current
		d.lastTime = time.Now()
	}
}

func (d *downloadinfo) FormatSpeed(unit string) string {
	switch strings.ToLower(unit) {
	case "kb":
		return fmt.Sprintf("%.2f KB/s", d.speed/1024)
	case "mb":
		return fmt.Sprintf("%.2f MB/s", d.speed/1024/1024)
	case "gb":
		return fmt.Sprintf("%.2f GB/s", d.speed/1024/1024/1024)
	default:
		return fmt.Sprintf("%.2f B/s", d.speed)
	}
}

func (d *downloadinfo) Speed() float64 {
	return d.speed
}