/*
Copyright (c) 2014-2015 VMware, Inc. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package nfc

import (
	"context"
	"log"
	"net/url"
	"sync"
	"sync/atomic"
	"time"

	"github.com/vmware/govmomi/vim25/progress"
	"github.com/vmware/govmomi/vim25/types"
)

type FileItem struct {
	types.OvfFileItem
	URL *url.URL

	ch chan progress.Report
}

func NewFileItem(u *url.URL, item types.OvfFileItem) FileItem {
	return FileItem{
		OvfFileItem: item,
		URL:         u,
		ch:          make(chan progress.Report),
	}
}

func (o FileItem) Sink() chan<- progress.Report {
	return o.ch
}

type LeaseUpdater struct {
	lease *Lease

	pos   int64 // Number of bytes
	total int64 // Total number of bytes

	done chan struct{} // When lease updater should stop

	wg sync.WaitGroup // Track when update loop is done
}

func newLeaseUpdater(ctx context.Context, lease *Lease, info *LeaseInfo) *LeaseUpdater {
	l := LeaseUpdater{
		lease: lease,

		done: make(chan struct{}),
	}

	for _, item := range info.Items {
		l.total += item.Size
		go l.waitForProgress(item)
	}

	// Kickstart update loop
	l.wg.Add(1)
	go l.run()

	return &l
}

func (l *LeaseUpdater) waitForProgress(item FileItem) {
	var pos, total int64

	total = item.Size

	for {
		select {
		case <-l.done:
			return
		case p, ok := <-item.ch:
			// Return in case of error
			if ok && p.Error() != nil {
				return
			}

			if !ok {
				// Last element on the channel, add to total
				atomic.AddInt64(&l.pos, total-pos)
				return
			}

			// Approximate progress in number of bytes
			x := int64(float32(total) * (p.Percentage() / 100.0))
			atomic.AddInt64(&l.pos, x-pos)
			pos = x
		}
	}
}

func (l *LeaseUpdater) run() {
	defer l.wg.Done()

	tick := time.NewTicker(2 * time.Second)
	defer tick.Stop()

	for {
		select {
		case <-l.done:
			return
		case <-tick.C:
			// From the vim api HttpNfcLeaseProgress(percent) doc, percent ==
			// "Completion status represented as an integer in the 0-100 range."
			// Always report the current value of percent, as it will renew the
			// lease even if the value hasn't changed or is 0.
			percent := int32(float32(100*atomic.LoadInt64(&l.pos)) / float32(l.total))
			err := l.lease.Progress(context.TODO(), percent)
			if err != nil {
				log.Printf("NFC lease progress: %s", err)
				return
			}
		}
	}
}

func (l *LeaseUpdater) Done() {
	close(l.done)
	l.wg.Wait()
}
