// 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 http://mozilla.org/MPL/2.0/.

// Package config implements reading and writing of the syncthing configuration file.
package config

import (
	"encoding/json"
	"encoding/xml"
	"io"
	"math/rand"
	"net/url"
	"os"
	"reflect"
	"sort"
	"strconv"
	"strings"

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

const (
	OldestHandledVersion = 10
	CurrentVersion       = 12
	MaxRescanIntervalS   = 365 * 24 * 60 * 60
)

var (
	// DefaultDiscoveryServersV4 should be substituted when the configuration
	// contains <globalAnnounceServer>default-v4</globalAnnounceServer>. This is
	// done by the "consumer" of the configuration, as we don't want these
	// saved to the config.
	DefaultDiscoveryServersV4 = []string{
		"https://discovery-v4-1.syncthing.net/?id=SR7AARM-TCBUZ5O-VFAXY4D-CECGSDE-3Q6IZ4G-XG7AH75-OBIXJQV-QJ6NLQA", // 194.126.249.5, Sweden
		"https://discovery-v4-2.syncthing.net/?id=DVU36WY-H3LVZHW-E6LLFRE-YAFN5EL-HILWRYP-OC2M47J-Z4PE62Y-ADIBDQC", // 45.55.230.38, USA
		"https://discovery-v4-3.syncthing.net/?id=VK6HNJ3-VVMM66S-HRVWSCR-IXEHL2H-U4AQ4MW-UCPQBWX-J2L2UBK-NVZRDQZ", // 128.199.95.124, Singapore
	}
	// DefaultDiscoveryServersV6 should be substituted when the configuration
	// contains <globalAnnounceServer>default-v6</globalAnnounceServer>.
	DefaultDiscoveryServersV6 = []string{
		"https://discovery-v6-1.syncthing.net/?id=SR7AARM-TCBUZ5O-VFAXY4D-CECGSDE-3Q6IZ4G-XG7AH75-OBIXJQV-QJ6NLQA", // 2001:470:28:4d6::5, Sweden
		"https://discovery-v6-2.syncthing.net/?id=DVU36WY-H3LVZHW-E6LLFRE-YAFN5EL-HILWRYP-OC2M47J-Z4PE62Y-ADIBDQC", // 2604:a880:800:10::182:a001, USA
		"https://discovery-v6-3.syncthing.net/?id=VK6HNJ3-VVMM66S-HRVWSCR-IXEHL2H-U4AQ4MW-UCPQBWX-J2L2UBK-NVZRDQZ", // 2400:6180:0:d0::d9:d001, Singapore
	}
	// DefaultDiscoveryServers should be substituted when the configuration
	// contains <globalAnnounceServer>default</globalAnnounceServer>.
	DefaultDiscoveryServers = append(DefaultDiscoveryServersV4, DefaultDiscoveryServersV6...)
)

func New(myID protocol.DeviceID) Configuration {
	var cfg Configuration
	cfg.Version = CurrentVersion
	cfg.OriginalVersion = CurrentVersion

	setDefaults(&cfg)
	setDefaults(&cfg.Options)
	setDefaults(&cfg.GUI)

	cfg.prepare(myID)

	return cfg
}

func ReadXML(r io.Reader, myID protocol.DeviceID) (Configuration, error) {
	var cfg Configuration

	setDefaults(&cfg)
	setDefaults(&cfg.Options)
	setDefaults(&cfg.GUI)

	err := xml.NewDecoder(r).Decode(&cfg)
	cfg.OriginalVersion = cfg.Version

	cfg.prepare(myID)
	return cfg, err
}

func ReadJSON(r io.Reader, myID protocol.DeviceID) (Configuration, error) {
	var cfg Configuration

	setDefaults(&cfg)
	setDefaults(&cfg.Options)
	setDefaults(&cfg.GUI)

	err := json.NewDecoder(r).Decode(&cfg)
	cfg.OriginalVersion = cfg.Version

	cfg.prepare(myID)
	return cfg, err
}

type Configuration struct {
	Version        int                   `xml:"version,attr" json:"version"`
	Folders        []FolderConfiguration `xml:"folder" json:"folders"`
	Devices        []DeviceConfiguration `xml:"device" json:"devices"`
	GUI            GUIConfiguration      `xml:"gui" json:"gui"`
	Options        OptionsConfiguration  `xml:"options" json:"options"`
	IgnoredDevices []protocol.DeviceID   `xml:"ignoredDevice" json:"ignoredDevices"`
	XMLName        xml.Name              `xml:"configuration" json:"-"`

	OriginalVersion int `xml:"-" json:"-"` // The version we read from disk, before any conversion
}

func (cfg Configuration) Copy() Configuration {
	newCfg := cfg

	// Deep copy FolderConfigurations
	newCfg.Folders = make([]FolderConfiguration, len(cfg.Folders))
	for i := range newCfg.Folders {
		newCfg.Folders[i] = cfg.Folders[i].Copy()
	}

	// Deep copy DeviceConfigurations
	newCfg.Devices = make([]DeviceConfiguration, len(cfg.Devices))
	for i := range newCfg.Devices {
		newCfg.Devices[i] = cfg.Devices[i].Copy()
	}

	newCfg.Options = cfg.Options.Copy()

	// DeviceIDs are values
	newCfg.IgnoredDevices = make([]protocol.DeviceID, len(cfg.IgnoredDevices))
	copy(newCfg.IgnoredDevices, cfg.IgnoredDevices)

	return newCfg
}

func (cfg *Configuration) WriteXML(w io.Writer) error {
	e := xml.NewEncoder(w)
	e.Indent("", "    ")
	err := e.Encode(cfg)
	if err != nil {
		return err
	}
	_, err = w.Write([]byte("\n"))
	return err
}

func (cfg *Configuration) prepare(myID protocol.DeviceID) {
	fillNilSlices(&cfg.Options)

	// Initialize any empty slices
	if cfg.Folders == nil {
		cfg.Folders = []FolderConfiguration{}
	}
	if cfg.IgnoredDevices == nil {
		cfg.IgnoredDevices = []protocol.DeviceID{}
	}
	if cfg.Options.AlwaysLocalNets == nil {
		cfg.Options.AlwaysLocalNets = []string{}
	}

	// Check for missing, bad or duplicate folder ID:s
	var seenFolders = map[string]*FolderConfiguration{}
	for i := range cfg.Folders {
		folder := &cfg.Folders[i]
		folder.prepare()

		if seen, ok := seenFolders[folder.ID]; ok {
			l.Warnf("Multiple folders with ID %q; disabling", folder.ID)
			seen.Invalid = "duplicate folder ID"
			folder.Invalid = "duplicate folder ID"
		} else {
			seenFolders[folder.ID] = folder
		}
	}

	cfg.Options.ListenAddress = uniqueStrings(cfg.Options.ListenAddress)
	cfg.Options.GlobalAnnServers = uniqueStrings(cfg.Options.GlobalAnnServers)

	if cfg.Version > 0 && cfg.Version < OldestHandledVersion {
		l.Warnf("Configuration version %d is deprecated. Attempting best effort conversion, but please verify manually.", cfg.Version)
	}

	// Upgrade configuration versions as appropriate
	if cfg.Version <= 10 {
		convertV10V11(cfg)
	}
	if cfg.Version == 11 {
		convertV11V12(cfg)
	}

	// Build a list of available devices
	existingDevices := make(map[protocol.DeviceID]bool)
	for _, device := range cfg.Devices {
		existingDevices[device.DeviceID] = true
	}

	// Ensure this device is present in the config
	if !existingDevices[myID] {
		myName, _ := os.Hostname()
		cfg.Devices = append(cfg.Devices, DeviceConfiguration{
			DeviceID: myID,
			Name:     myName,
		})
		existingDevices[myID] = true
	}

	sort.Sort(DeviceConfigurationList(cfg.Devices))
	// Ensure that any loose devices are not present in the wrong places
	// Ensure that there are no duplicate devices
	// Ensure that puller settings are sane
	for i := range cfg.Folders {
		cfg.Folders[i].Devices = ensureDevicePresent(cfg.Folders[i].Devices, myID)
		cfg.Folders[i].Devices = ensureExistingDevices(cfg.Folders[i].Devices, existingDevices)
		cfg.Folders[i].Devices = ensureNoDuplicates(cfg.Folders[i].Devices)
		sort.Sort(FolderDeviceConfigurationList(cfg.Folders[i].Devices))
	}

	// An empty address list is equivalent to a single "dynamic" entry
	for i := range cfg.Devices {
		n := &cfg.Devices[i]
		if len(n.Addresses) == 0 || len(n.Addresses) == 1 && n.Addresses[0] == "" {
			n.Addresses = []string{"dynamic"}
		}
	}

	// Very short reconnection intervals are annoying
	if cfg.Options.ReconnectIntervalS < 5 {
		cfg.Options.ReconnectIntervalS = 5
	}

	if cfg.GUI.RawAPIKey == "" {
		cfg.GUI.RawAPIKey = randomString(32)
	}
}

func convertV11V12(cfg *Configuration) {
	// Change listen address schema
	for i, addr := range cfg.Options.ListenAddress {
		if len(addr) > 0 && !strings.HasPrefix(addr, "tcp://") {
			cfg.Options.ListenAddress[i] = tcpAddr(addr)
		}
	}

	for i, device := range cfg.Devices {
		for j, addr := range device.Addresses {
			if addr != "dynamic" && addr != "" {
				cfg.Devices[i].Addresses[j] = tcpAddr(addr)
			}
		}
	}

	// Use new discovery server
	var newDiscoServers []string
	var useDefault bool
	for _, addr := range cfg.Options.GlobalAnnServers {
		if addr == "udp4://announce.syncthing.net:22026" {
			useDefault = true
		} else if addr == "udp6://announce-v6.syncthing.net:22026" {
			useDefault = true
		} else {
			newDiscoServers = append(newDiscoServers, addr)
		}
	}
	if useDefault {
		newDiscoServers = append(newDiscoServers, "default")
	}
	cfg.Options.GlobalAnnServers = newDiscoServers

	// Use new multicast group
	if cfg.Options.LocalAnnMCAddr == "[ff32::5222]:21026" {
		cfg.Options.LocalAnnMCAddr = "[ff12::8384]:21027"
	}

	// Use new local discovery port
	if cfg.Options.LocalAnnPort == 21025 {
		cfg.Options.LocalAnnPort = 21027
	}

	// Set MaxConflicts to unlimited
	for i := range cfg.Folders {
		cfg.Folders[i].MaxConflicts = -1
	}

	cfg.Version = 12
}

func convertV10V11(cfg *Configuration) {
	// Set minimum disk free of existing folders to 1%
	for i := range cfg.Folders {
		cfg.Folders[i].MinDiskFreePct = 1
	}
	cfg.Version = 11
}

func setDefaults(data interface{}) error {
	s := reflect.ValueOf(data).Elem()
	t := s.Type()

	for i := 0; i < s.NumField(); i++ {
		f := s.Field(i)
		tag := t.Field(i).Tag

		v := tag.Get("default")
		if len(v) > 0 {
			switch f.Interface().(type) {
			case string:
				f.SetString(v)

			case int:
				i, err := strconv.ParseInt(v, 10, 64)
				if err != nil {
					return err
				}
				f.SetInt(i)

			case float64:
				i, err := strconv.ParseFloat(v, 64)
				if err != nil {
					return err
				}
				f.SetFloat(i)

			case bool:
				f.SetBool(v == "true")

			case []string:
				// We don't do anything with string slices here. Any default
				// we set will be appended to by the XML decoder, so we fill
				// those after decoding.

			default:
				panic(f.Type())
			}
		}
	}
	return nil
}

// fillNilSlices sets default value on slices that are still nil.
func fillNilSlices(data interface{}) error {
	s := reflect.ValueOf(data).Elem()
	t := s.Type()

	for i := 0; i < s.NumField(); i++ {
		f := s.Field(i)
		tag := t.Field(i).Tag

		v := tag.Get("default")
		if len(v) > 0 {
			switch f.Interface().(type) {
			case []string:
				if f.IsNil() {
					// Treat the default as a comma separated slice
					vs := strings.Split(v, ",")
					for i := range vs {
						vs[i] = strings.TrimSpace(vs[i])
					}

					rv := reflect.MakeSlice(reflect.TypeOf([]string{}), len(vs), len(vs))
					for i, v := range vs {
						rv.Index(i).SetString(v)
					}
					f.Set(rv)
				}
			}
		}
	}
	return nil
}

func uniqueStrings(ss []string) []string {
	var m = make(map[string]bool, len(ss))
	for _, s := range ss {
		m[strings.Trim(s, " ")] = true
	}

	var us = make([]string, 0, len(m))
	for k := range m {
		us = append(us, k)
	}

	sort.Strings(us)

	return us
}

func ensureDevicePresent(devices []FolderDeviceConfiguration, myID protocol.DeviceID) []FolderDeviceConfiguration {
	for _, device := range devices {
		if device.DeviceID.Equals(myID) {
			return devices
		}
	}

	devices = append(devices, FolderDeviceConfiguration{
		DeviceID: myID,
	})

	return devices
}

func ensureExistingDevices(devices []FolderDeviceConfiguration, existingDevices map[protocol.DeviceID]bool) []FolderDeviceConfiguration {
	count := len(devices)
	i := 0
loop:
	for i < count {
		if _, ok := existingDevices[devices[i].DeviceID]; !ok {
			devices[i] = devices[count-1]
			count--
			continue loop
		}
		i++
	}
	return devices[0:count]
}

func ensureNoDuplicates(devices []FolderDeviceConfiguration) []FolderDeviceConfiguration {
	count := len(devices)
	i := 0
	seenDevices := make(map[protocol.DeviceID]bool)
loop:
	for i < count {
		id := devices[i].DeviceID
		if _, ok := seenDevices[id]; ok {
			devices[i] = devices[count-1]
			count--
			continue loop
		}
		seenDevices[id] = true
		i++
	}
	return devices[0:count]
}

// randomCharset contains the characters that can make up a randomString().
const randomCharset = "01234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-"

// randomString returns a string of random characters (taken from
// randomCharset) of the specified length.
func randomString(l int) string {
	bs := make([]byte, l)
	for i := range bs {
		bs[i] = randomCharset[rand.Intn(len(randomCharset))]
	}
	return string(bs)
}

func tcpAddr(host string) string {
	u := url.URL{
		Scheme: "tcp",
		Host:   host,
	}
	return u.String()
}