// Copyright (C) 2014 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 https://mozilla.org/MPL/2.0/.

package model

import (
	"github.com/syncthing/syncthing/lib/config"
	"github.com/syncthing/syncthing/lib/db"
	"github.com/syncthing/syncthing/lib/events"
	"github.com/syncthing/syncthing/lib/fs"
	"github.com/syncthing/syncthing/lib/ignore"
	"github.com/syncthing/syncthing/lib/protocol"
	"github.com/syncthing/syncthing/lib/util"
	"github.com/syncthing/syncthing/lib/versioner"
)

func init() {
	folderFactories[config.FolderTypeSendOnly] = newSendOnlyFolder
}

type sendOnlyFolder struct {
	folder
}

func newSendOnlyFolder(model *model, fset *db.FileSet, ignores *ignore.Matcher, cfg config.FolderConfiguration, _ versioner.Versioner, _ fs.Filesystem, evLogger events.Logger, ioLimiter *byteSemaphore) service {
	f := &sendOnlyFolder{
		folder: newFolder(model, fset, ignores, cfg, evLogger, ioLimiter),
	}
	f.folder.puller = f
	f.folder.Service = util.AsService(f.serve, f.String())
	return f
}

func (f *sendOnlyFolder) PullErrors() []FileError {
	return nil
}

// pull checks need for files that only differ by metadata (no changes on disk)
func (f *sendOnlyFolder) pull() bool {
	select {
	case <-f.initialScanFinished:
	default:
		// Once the initial scan finished, a pull will be scheduled
		return false
	}

	batch := make([]protocol.FileInfo, 0, maxBatchSizeFiles)
	batchSizeBytes := 0

	snap := f.fset.Snapshot()
	defer snap.Release()
	snap.WithNeed(protocol.LocalDeviceID, func(intf protocol.FileIntf) bool {
		if len(batch) == maxBatchSizeFiles || batchSizeBytes > maxBatchSizeBytes {
			f.updateLocalsFromPulling(batch)
			batch = batch[:0]
			batchSizeBytes = 0
		}

		if f.ignores.ShouldIgnore(intf.FileName()) {
			file := intf.(protocol.FileInfo)
			file.SetIgnored(f.shortID)
			batch = append(batch, file)
			batchSizeBytes += file.ProtoSize()
			l.Debugln(f, "Handling ignored file", file)
			return true
		}

		curFile, ok := snap.Get(protocol.LocalDeviceID, intf.FileName())
		if !ok {
			if intf.IsDeleted() {
				l.Debugln("Should never get a deleted file as needed when we don't have it")
			}
			return true
		}

		file := intf.(protocol.FileInfo)
		if !file.IsEquivalentOptional(curFile, f.ModTimeWindow(), f.IgnorePerms, false, 0) {
			return true
		}

		file.Version = file.Version.Merge(curFile.Version)
		batch = append(batch, file)
		batchSizeBytes += file.ProtoSize()
		l.Debugln(f, "Merging versions of identical file", file)

		return true
	})

	if len(batch) > 0 {
		f.updateLocalsFromPulling(batch)
	}

	return true
}

func (f *sendOnlyFolder) Override() {
	f.doInSync(func() error { f.override(); return nil })
}

func (f *sendOnlyFolder) override() {
	l.Infof("Overriding global state on folder %v", f.Description)

	f.setState(FolderScanning)
	defer f.setState(FolderIdle)

	batch := make([]protocol.FileInfo, 0, maxBatchSizeFiles)
	batchSizeBytes := 0
	snap := f.fset.Snapshot()
	defer snap.Release()
	snap.WithNeed(protocol.LocalDeviceID, func(fi protocol.FileIntf) bool {
		need := fi.(protocol.FileInfo)
		if len(batch) == maxBatchSizeFiles || batchSizeBytes > maxBatchSizeBytes {
			f.updateLocalsFromScanning(batch)
			batch = batch[:0]
			batchSizeBytes = 0
		}

		have, ok := snap.Get(protocol.LocalDeviceID, need.Name)
		// Don't override files that are in a bad state (ignored,
		// unsupported, must rescan, ...).
		if ok && have.IsInvalid() {
			return true
		}
		if !ok || have.Name != need.Name {
			// We are missing the file
			need.SetDeleted(f.shortID)
		} else {
			// We have the file, replace with our version
			have.Version = have.Version.Merge(need.Version).Update(f.shortID)
			need = have
		}
		need.Sequence = 0
		batch = append(batch, need)
		batchSizeBytes += need.ProtoSize()
		return true
	})
	if len(batch) > 0 {
		f.updateLocalsFromScanning(batch)
	}
}