// 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 config

import (
	"errors"
	"fmt"
	"runtime"
	"strings"
	"time"

	"github.com/shirou/gopsutil/disk"

	"github.com/syncthing/syncthing/lib/fs"
	"github.com/syncthing/syncthing/lib/protocol"
	"github.com/syncthing/syncthing/lib/util"
)

var (
	ErrPathNotDirectory = errors.New("folder path not a directory")
	ErrPathMissing      = errors.New("folder path missing")
	ErrMarkerMissing    = errors.New("folder marker missing (this indicates potential data loss, search docs/forum to get information about how to proceed)")
)

const DefaultMarkerName = ".stfolder"

type FolderConfiguration struct {
	ID                      string                      `xml:"id,attr" json:"id"`
	Label                   string                      `xml:"label,attr" json:"label" restart:"false"`
	FilesystemType          fs.FilesystemType           `xml:"filesystemType" json:"filesystemType"`
	Path                    string                      `xml:"path,attr" json:"path"`
	Type                    FolderType                  `xml:"type,attr" json:"type"`
	Devices                 []FolderDeviceConfiguration `xml:"device" json:"devices"`
	RescanIntervalS         int                         `xml:"rescanIntervalS,attr" json:"rescanIntervalS" default:"3600"`
	FSWatcherEnabled        bool                        `xml:"fsWatcherEnabled,attr" json:"fsWatcherEnabled" default:"true"`
	FSWatcherDelayS         int                         `xml:"fsWatcherDelayS,attr" json:"fsWatcherDelayS" default:"10"`
	IgnorePerms             bool                        `xml:"ignorePerms,attr" json:"ignorePerms"`
	AutoNormalize           bool                        `xml:"autoNormalize,attr" json:"autoNormalize" default:"true"`
	MinDiskFree             Size                        `xml:"minDiskFree" json:"minDiskFree" default:"1%"`
	Versioning              VersioningConfiguration     `xml:"versioning" json:"versioning"`
	Copiers                 int                         `xml:"copiers" json:"copiers"` // This defines how many files are handled concurrently.
	PullerMaxPendingKiB     int                         `xml:"pullerMaxPendingKiB" json:"pullerMaxPendingKiB"`
	Hashers                 int                         `xml:"hashers" json:"hashers"` // Less than one sets the value to the number of cores. These are CPU bound due to hashing.
	Order                   PullOrder                   `xml:"order" json:"order"`
	IgnoreDelete            bool                        `xml:"ignoreDelete" json:"ignoreDelete"`
	ScanProgressIntervalS   int                         `xml:"scanProgressIntervalS" json:"scanProgressIntervalS"` // Set to a negative value to disable. Value of 0 will get replaced with value of 2 (default value)
	PullerPauseS            int                         `xml:"pullerPauseS" json:"pullerPauseS"`
	MaxConflicts            int                         `xml:"maxConflicts" json:"maxConflicts" default:"-1"`
	DisableSparseFiles      bool                        `xml:"disableSparseFiles" json:"disableSparseFiles"`
	DisableTempIndexes      bool                        `xml:"disableTempIndexes" json:"disableTempIndexes"`
	Paused                  bool                        `xml:"paused" json:"paused"`
	WeakHashThresholdPct    int                         `xml:"weakHashThresholdPct" json:"weakHashThresholdPct"` // Use weak hash if more than X percent of the file has changed. Set to -1 to always use weak hash.
	MarkerName              string                      `xml:"markerName" json:"markerName"`
	CopyOwnershipFromParent bool                        `xml:"copyOwnershipFromParent" json:"copyOwnershipFromParent"`
	RawModTimeWindowS       int                         `xml:"modTimeWindowS" json:"modTimeWindowS"`
	MaxConcurrentWrites     int                         `xml:"maxConcurrentWrites" json:"maxConcurrentWrites" default:"2"`
	DisableFsync            bool                        `xml:"disableFsync" json:"disableFsync"`
	BlockPullOrder          BlockPullOrder              `xml:"blockPullOrder" json:"blockPullOrder"`
	CopyRangeMethod         fs.CopyRangeMethod          `xml:"copyRangeMethod" json:"copyRangeMethod" default:"standard"`

	cachedFilesystem    fs.Filesystem
	cachedModTimeWindow time.Duration

	DeprecatedReadOnly       bool    `xml:"ro,attr,omitempty" json:"-"`
	DeprecatedMinDiskFreePct float64 `xml:"minDiskFreePct,omitempty" json:"-"`
	DeprecatedPullers        int     `xml:"pullers,omitempty" json:"-"`
}

type FolderDeviceConfiguration struct {
	DeviceID     protocol.DeviceID `xml:"id,attr" json:"deviceID"`
	IntroducedBy protocol.DeviceID `xml:"introducedBy,attr" json:"introducedBy"`
}

func NewFolderConfiguration(myID protocol.DeviceID, id, label string, fsType fs.FilesystemType, path string) FolderConfiguration {
	f := FolderConfiguration{
		ID:             id,
		Label:          label,
		Devices:        []FolderDeviceConfiguration{{DeviceID: myID}},
		FilesystemType: fsType,
		Path:           path,
	}

	util.SetDefaults(&f)

	f.prepare()
	return f
}

func (f FolderConfiguration) Copy() FolderConfiguration {
	c := f
	c.Devices = make([]FolderDeviceConfiguration, len(f.Devices))
	copy(c.Devices, f.Devices)
	c.Versioning = f.Versioning.Copy()
	return c
}

func (f FolderConfiguration) Filesystem() fs.Filesystem {
	// This is intentionally not a pointer method, because things like
	// cfg.Folders["default"].Filesystem() should be valid.
	if f.cachedFilesystem == nil {
		l.Infoln("bug: uncached filesystem call (should only happen in tests)")
		return fs.NewFilesystem(f.FilesystemType, f.Path)
	}
	return f.cachedFilesystem
}

func (f FolderConfiguration) ModTimeWindow() time.Duration {
	return f.cachedModTimeWindow
}

func (f *FolderConfiguration) CreateMarker() error {
	if err := f.CheckPath(); err != ErrMarkerMissing {
		return err
	}
	if f.MarkerName != DefaultMarkerName {
		// Folder uses a non-default marker so we shouldn't mess with it.
		// Pretend we created it and let the subsequent health checks sort
		// out the actual situation.
		return nil
	}

	permBits := fs.FileMode(0777)
	if runtime.GOOS == "windows" {
		// Windows has no umask so we must chose a safer set of bits to
		// begin with.
		permBits = 0700
	}
	fs := f.Filesystem()
	err := fs.Mkdir(DefaultMarkerName, permBits)
	if err != nil {
		return err
	}
	if dir, err := fs.Open("."); err != nil {
		l.Debugln("folder marker: open . failed:", err)
	} else if err := dir.Sync(); err != nil {
		l.Debugln("folder marker: fsync . failed:", err)
	}
	fs.Hide(DefaultMarkerName)

	return nil
}

// CheckPath returns nil if the folder root exists and contains the marker file
func (f *FolderConfiguration) CheckPath() error {
	fi, err := f.Filesystem().Stat(".")
	if err != nil {
		if !fs.IsNotExist(err) {
			return err
		}
		return ErrPathMissing
	}

	// Users might have the root directory as a symlink or reparse point.
	// Furthermore, OneDrive bullcrap uses a magic reparse point to the cloudz...
	// Yet it's impossible for this to happen, as filesystem adds a trailing
	// path separator to the root, so even if you point the filesystem at a file
	// Stat ends up calling stat on C:\dir\file\ which, fails with "is not a directory"
	// in the error check above, and we don't even get to here.
	if !fi.IsDir() && !fi.IsSymlink() {
		return ErrPathNotDirectory
	}

	_, err = f.Filesystem().Stat(f.MarkerName)
	if err != nil {
		if !fs.IsNotExist(err) {
			return err
		}
		return ErrMarkerMissing
	}

	return nil
}

func (f *FolderConfiguration) CreateRoot() (err error) {
	// Directory permission bits. Will be filtered down to something
	// sane by umask on Unixes.
	permBits := fs.FileMode(0777)
	if runtime.GOOS == "windows" {
		// Windows has no umask so we must chose a safer set of bits to
		// begin with.
		permBits = 0700
	}

	filesystem := f.Filesystem()

	if _, err = filesystem.Stat("."); fs.IsNotExist(err) {
		err = filesystem.MkdirAll(".", permBits)
	}

	return err
}

func (f FolderConfiguration) Description() string {
	if f.Label == "" {
		return f.ID
	}
	return fmt.Sprintf("%q (%s)", f.Label, f.ID)
}

func (f *FolderConfiguration) DeviceIDs() []protocol.DeviceID {
	deviceIDs := make([]protocol.DeviceID, len(f.Devices))
	for i, n := range f.Devices {
		deviceIDs[i] = n.DeviceID
	}
	return deviceIDs
}

func (f *FolderConfiguration) prepare() {
	f.cachedFilesystem = fs.NewFilesystem(f.FilesystemType, f.Path)

	if f.RescanIntervalS > MaxRescanIntervalS {
		f.RescanIntervalS = MaxRescanIntervalS
	} else if f.RescanIntervalS < 0 {
		f.RescanIntervalS = 0
	}

	if f.FSWatcherDelayS <= 0 {
		f.FSWatcherEnabled = false
		f.FSWatcherDelayS = 10
	}

	if f.Versioning.Params == nil {
		f.Versioning.Params = make(map[string]string)
	}

	if f.WeakHashThresholdPct == 0 {
		f.WeakHashThresholdPct = 25
	}

	if f.MarkerName == "" {
		f.MarkerName = DefaultMarkerName
	}

	switch {
	case f.RawModTimeWindowS > 0:
		f.cachedModTimeWindow = time.Duration(f.RawModTimeWindowS) * time.Second
	case runtime.GOOS == "android":
		if usage, err := disk.Usage(f.Filesystem().URI()); err != nil {
			f.cachedModTimeWindow = 2 * time.Second
			l.Debugf(`Detecting FS at "%v" on android: Setting mtime window to 2s: err == "%v"`, f.Path, err)
		} else if usage.Fstype == "" || strings.Contains(strings.ToLower(usage.Fstype), "fat") {
			f.cachedModTimeWindow = 2 * time.Second
			l.Debugf(`Detecting FS at "%v" on android: Setting mtime window to 2s: usage.Fstype == "%v"`, f.Path, usage.Fstype)
		} else {
			l.Debugf(`Detecting FS at %v on android: Leaving mtime window at 0: usage.Fstype == "%v"`, f.Path, usage.Fstype)
		}
	}
}

// RequiresRestartOnly returns a copy with only the attributes that require
// restart on change.
func (f FolderConfiguration) RequiresRestartOnly() FolderConfiguration {
	copy := f

	// Manual handling for things that are not taken care of by the tag
	// copier, yet should not cause a restart.
	copy.cachedFilesystem = nil

	blank := FolderConfiguration{}
	util.CopyMatchingTag(&blank, &copy, "restart", func(v string) bool {
		if len(v) > 0 && v != "false" {
			panic(fmt.Sprintf(`unexpected tag value: %s. expected untagged or "false"`, v))
		}
		return v == "false"
	})
	return copy
}

func (f *FolderConfiguration) SharedWith(device protocol.DeviceID) bool {
	for _, dev := range f.Devices {
		if dev.DeviceID == device {
			return true
		}
	}
	return false
}

func (f *FolderConfiguration) CheckAvailableSpace(req int64) error {
	val := f.MinDiskFree.BaseValue()
	if val <= 0 {
		return nil
	}
	fs := f.Filesystem()
	usage, err := fs.Usage(".")
	if err != nil {
		return nil
	}
	usage.Free -= req
	if usage.Free > 0 {
		if err := CheckFreeSpace(f.MinDiskFree, usage); err == nil {
			return nil
		}
	}
	return fmt.Errorf("insufficient space in %v %v", fs.Type(), fs.URI())
}