// Copyright (C) 2015 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at http://mozilla.org/MPL/2.0/.

package model

import (
	"github.com/syncthing/syncthing/lib/protocol"
	"github.com/syncthing/syncthing/lib/sync"
)

// deviceFolderFileDownloadState holds current download state of a file that
// a remote device has advertised. blockIndexes represends indexes within
// FileInfo.Blocks that the remote device already has, and version represents
// the version of the file that the remote device is downloading.
type deviceFolderFileDownloadState struct {
	blockIndexes []int32
	version      protocol.Vector
}

// deviceFolderDownloadState holds current download state of all files that
// a remote device is currently downloading in a specific folder.
type deviceFolderDownloadState struct {
	mut                      sync.RWMutex
	files                    map[string]deviceFolderFileDownloadState
	numberOfBlocksInProgress int
}

// Has returns whether a block at that specific index, and that specific version of the file
// is currently available on the remote device for pulling from a temporary file.
func (p *deviceFolderDownloadState) Has(file string, version protocol.Vector, index int32) bool {
	p.mut.RLock()
	defer p.mut.RUnlock()

	local, ok := p.files[file]

	if !ok || !local.version.Equal(version) {
		return false
	}

	for _, existingIndex := range local.blockIndexes {
		if existingIndex == index {
			return true
		}
	}
	return false
}

// Update updates internal state of what has been downloaded into the temporary
// files by the remote device for this specific folder.
func (p *deviceFolderDownloadState) Update(updates []protocol.FileDownloadProgressUpdate) {
	p.mut.Lock()
	defer p.mut.Unlock()

	for _, update := range updates {
		local, ok := p.files[update.Name]
		if update.UpdateType == protocol.UpdateTypeForget && ok && local.version.Equal(update.Version) {
			p.numberOfBlocksInProgress -= len(local.blockIndexes)
			delete(p.files, update.Name)
		} else if update.UpdateType == protocol.UpdateTypeAppend {
			if !ok {
				local = deviceFolderFileDownloadState{
					blockIndexes: update.BlockIndexes,
					version:      update.Version,
				}
			} else if !local.version.Equal(update.Version) {
				p.numberOfBlocksInProgress -= len(local.blockIndexes)
				local.blockIndexes = append(local.blockIndexes[:0], update.BlockIndexes...)
				local.version = update.Version
			} else {
				local.blockIndexes = append(local.blockIndexes, update.BlockIndexes...)
			}
			p.files[update.Name] = local
			p.numberOfBlocksInProgress += len(update.BlockIndexes)
		}
	}
}

// NumberOfBlocksInProgress returns the number of blocks the device has downloaded
// for a specific folder.
func (p *deviceFolderDownloadState) NumberOfBlocksInProgress() int {
	p.mut.RLock()
	n := p.numberOfBlocksInProgress
	p.mut.RUnlock()
	return n
}

// deviceDownloadState represents the state of all in progress downloads
// for all folders of a specific device.
type deviceDownloadState struct {
	mut     sync.RWMutex
	folders map[string]*deviceFolderDownloadState
}

// Update updates internal state of what has been downloaded into the temporary
// files by the remote device for this specific folder.
func (t *deviceDownloadState) Update(folder string, updates []protocol.FileDownloadProgressUpdate) {
	if t == nil {
		return
	}
	t.mut.RLock()
	f, ok := t.folders[folder]
	t.mut.RUnlock()

	if !ok {
		f = &deviceFolderDownloadState{
			mut:   sync.NewRWMutex(),
			files: make(map[string]deviceFolderFileDownloadState),
		}
		t.mut.Lock()
		t.folders[folder] = f
		t.mut.Unlock()
	}

	f.Update(updates)
}

// Has returns whether block at that specific index, and that specific version of the file
// is currently available on the remote device for pulling from a temporary file.
func (t *deviceDownloadState) Has(folder, file string, version protocol.Vector, index int32) bool {
	if t == nil {
		return false
	}
	t.mut.RLock()
	f, ok := t.folders[folder]
	t.mut.RUnlock()

	if !ok {
		return false
	}

	return f.Has(file, version, index)
}

// NumberOfBlocksInProgress returns the number of blocks the device has downloaded
// for all folders.
func (t *deviceDownloadState) NumberOfBlocksInProgress() int {
	if t == nil {
		return 0
	}

	n := 0
	t.mut.RLock()
	for _, folder := range t.folders {
		n += folder.NumberOfBlocksInProgress()
	}
	t.mut.RUnlock()
	return n
}

func newDeviceDownloadState() *deviceDownloadState {
	return &deviceDownloadState{
		mut:     sync.NewRWMutex(),
		folders: make(map[string]*deviceFolderDownloadState),
	}
}