package downloader

import (
	"errors"
	"git.bvbej.com/bvbej/base-golang/pkg/downloader/base"
	"git.bvbej.com/bvbej/base-golang/pkg/downloader/controller"
	"git.bvbej.com/bvbej/base-golang/pkg/downloader/fetcher"
	"git.bvbej.com/bvbej/base-golang/pkg/downloader/protocol/http"
	"git.bvbej.com/bvbej/base-golang/pkg/downloader/util"
	"github.com/google/uuid"
	"net/url"
	"strings"
	"sync"
	"time"
)

type Listener func(event *Event)

type TaskInfo struct {
	ID       string
	Res      *base.Resource
	Opts     *base.Options
	Status   base.Status
	Progress *Progress

	fetcher fetcher.Fetcher
	timer   *util.Timer
	locker  *sync.Mutex
}

type Progress struct {
	// 下载耗时(纳秒)
	Used int64
	// 每秒下载字节数
	Speed int64
	// 已下载的字节数
	Downloaded int64
}

type downloader struct {
	*controller.DefaultController
	fetchBuilders map[string]func() fetcher.Fetcher
	task          *TaskInfo
	listener      Listener
	finished      bool
	finishedCh    chan error
}

func newDownloader(f func() (protocols []string, builder func() fetcher.Fetcher)) *downloader {
	d := &downloader{
		DefaultController: controller.NewController(),
		finishedCh:        make(chan error),
	}

	d.fetchBuilders = make(map[string]func() fetcher.Fetcher)
	protocols, builder := f()
	for _, p := range protocols {
		d.fetchBuilders[strings.ToUpper(p)] = builder
	}

	return d
}

func (d *downloader) buildFetcher(URL string) (fetcher.Fetcher, error) {
	parseURL, err := url.Parse(URL)
	if err != nil {
		return nil, err
	}
	if fetchBuilder, ok := d.fetchBuilders[strings.ToUpper(parseURL.Scheme)]; ok {
		fetched := fetchBuilder()
		fetched.Setup(d.DefaultController)
		return fetched, nil
	}
	return nil, errors.New("unsupported protocol")
}

func (d *downloader) Resolve(req *base.Request) (*base.Resource, error) {
	fetched, err := d.buildFetcher(req.URL)
	if err != nil {
		return nil, err
	}
	return fetched.Resolve(req)
}

func (d *downloader) Create(res *base.Resource, opts *base.Options) (err error) {
	fetched, err := d.buildFetcher(res.Req.URL)
	if err != nil {
		return
	}
	if !res.Range || opts.Connections < 1 {
		opts.Connections = 1
	}
	err = fetched.Create(res, opts)
	if err != nil {
		return
	}

	task := &TaskInfo{
		ID:       uuid.New().String(),
		Res:      res,
		Opts:     opts,
		Status:   base.DownloadStatusStart,
		Progress: &Progress{},
		fetcher:  fetched,
		timer:    &util.Timer{},
		locker:   new(sync.Mutex),
	}
	d.task = task
	task.timer.Start()
	d.emit(EventKeyStart)
	err = fetched.Start()
	if err != nil {
		return
	}

	go func() {
		err = fetched.Wait()
		if err != nil {
			d.emit(EventKeyError, err)
			task.Status = base.DownloadStatusError
		} else {
			task.Progress.Used = task.timer.Used()
			if task.Res.TotalSize == 0 {
				task.Res.TotalSize = task.fetcher.Progress().TotalDownloaded()
			}
			used := task.Progress.Used / int64(time.Second)
			if used == 0 {
				used = 1
			}
			task.Progress.Speed = task.Res.TotalSize / used
			task.Progress.Downloaded = task.Res.TotalSize
			d.emit(EventKeyDone)
			task.Status = base.DownloadStatusDone
		}
		d.emit(EventKeyFinally, err)
		time.AfterFunc(1100*time.Millisecond, func() {
			d.finished = true
			d.finishedCh <- err
		})
	}()

	// 每秒统计一次下载速度
	go func() {
		for !d.finished {
			if d.task.Status == base.DownloadStatusPause {
				continue
			}

			current := d.task.fetcher.Progress().TotalDownloaded()
			d.task.Progress.Used = d.task.timer.Used()
			d.task.Progress.Speed = current - d.task.Progress.Downloaded
			d.task.Progress.Downloaded = current
			d.emit(EventKeyProgress)

			time.Sleep(time.Second)
		}
	}()

	return
}

func (d *downloader) Pause() error {
	d.task.locker.Lock()
	defer d.task.locker.Unlock()
	d.task.timer.Pause()
	err := d.task.fetcher.Pause()
	if err != nil {
		return err
	}
	d.emit(EventKeyPause)
	d.task.Status = base.DownloadStatusPause
	return nil
}

func (d *downloader) Continue() error {
	d.task.locker.Lock()
	defer d.task.locker.Unlock()
	d.task.timer.Continue()
	err := d.task.fetcher.Continue()
	if err != nil {
		return err
	}
	d.emit(EventKeyContinue)
	d.task.Status = base.DownloadStatusStart
	return nil
}

func (d *downloader) Listener(fn Listener) {
	d.listener = fn
}

func (d *downloader) emit(eventKey EventKey, errs ...error) {
	if d.listener != nil {
		var err error
		if len(errs) > 0 {
			err = errs[0]
		}
		d.listener(&Event{
			Key:  eventKey,
			Task: d.task,
			Err:  err,
		})
	}
}

var _ Boot = (*boot)(nil)

type Boot interface {
	URL(url string) Boot
	Extra(extra any) Boot
	Listener(listener Listener) Boot
	Create(opts *base.Options) <-chan error
}

type boot struct {
	url        string
	extra      any
	listener   Listener
	downloader *downloader
}

func (b *boot) resolve() (*base.Resource, error) {
	return b.downloader.Resolve(&base.Request{
		URL:   b.url,
		Extra: b.extra,
	})
}

func (b *boot) URL(url string) Boot {
	b.url = url
	return b
}

func (b *boot) Extra(extra any) Boot {
	b.extra = extra
	return b
}

func (b *boot) Listener(listener Listener) Boot {
	b.listener = listener
	return b
}

func (b *boot) Create(opts *base.Options) <-chan error {
	res, err := b.resolve()
	if err != nil {
		b.downloader.finishedCh <- err
		return b.downloader.finishedCh
	}
	b.downloader.Listener(b.listener)

	err = b.downloader.Create(res, opts)
	if err != nil {
		b.downloader.finishedCh <- err
		return b.downloader.finishedCh
	}

	return b.downloader.finishedCh
}

func New() Boot {
	return &boot{
		downloader: newDownloader(http.FetcherBuilder),
	}
}