package jsondb

import (
	"encoding/base64"
	"encoding/json"
	"fmt"
	"log"
	"os"
	"path"
	"strconv"
	"strings"
	"time"

	"github.com/sdomino/scribble"
	"github.com/skip2/go-qrcode"
	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"

	"github.com/ngoduykhanh/wireguard-ui/model"
	"github.com/ngoduykhanh/wireguard-ui/util"
)

// legacyDefaultServerID is the synthetic ID assigned to a pre-existing
// single-server installation when it is migrated to the multi-server layout.
const legacyDefaultServerID = util.DefaultServerID

type JsonDB struct {
	conn   *scribble.Driver
	dbPath string
}

// New returns a new pointer JsonDB
func New(dbPath string) (*JsonDB, error) {
	conn, err := scribble.New(dbPath, nil)
	if err != nil {
		return nil, err
	}
	ans := JsonDB{
		conn:   conn,
		dbPath: dbPath,
	}
	return &ans, nil
}

func (o *JsonDB) Init() error {
	var clientPath = path.Join(o.dbPath, "clients")
	var serverPath = path.Join(o.dbPath, "server")
	var userPath = path.Join(o.dbPath, "users")
	var wakeOnLanHostsPath = path.Join(o.dbPath, "wake_on_lan_hosts")
	var serverInterfacePath = path.Join(serverPath, "interfaces.json")
	var serverKeyPairPath = path.Join(serverPath, "keypair.json")
	var globalSettingPath = path.Join(serverPath, "global_settings.json")
	var hashesPath = path.Join(serverPath, "hashes.json")

	// create directories if they do not exist
	if _, err := os.Stat(clientPath); os.IsNotExist(err) {
		os.MkdirAll(clientPath, os.ModePerm)
	}
	if _, err := os.Stat(serverPath); os.IsNotExist(err) {
		os.MkdirAll(serverPath, os.ModePerm)
	}
	if _, err := os.Stat(userPath); os.IsNotExist(err) {
		os.MkdirAll(userPath, os.ModePerm)
	}
	if _, err := os.Stat(wakeOnLanHostsPath); os.IsNotExist(err) {
		os.MkdirAll(wakeOnLanHostsPath, os.ModePerm)
	}

	// server's interface
	if _, err := os.Stat(serverInterfacePath); os.IsNotExist(err) {
		serverInterface := new(model.ServerInterface)
		serverInterface.Addresses = util.LookupEnvOrStrings(util.ServerAddressesEnvVar, []string{util.DefaultServerAddress})
		serverInterface.ListenPort = util.LookupEnvOrInt(util.ServerListenPortEnvVar, util.DefaultServerPort)
		serverInterface.PostUp = util.LookupEnvOrString(util.ServerPostUpScriptEnvVar, "")
		serverInterface.PostDown = util.LookupEnvOrString(util.ServerPostDownScriptEnvVar, "")
		serverInterface.UpdatedAt = time.Now().UTC()
		o.conn.Write("server", "interfaces", serverInterface)
		err := util.ManagePerms(serverInterfacePath)
		if err != nil {
			return err
		}
	}

	// server's key pair
	if _, err := os.Stat(serverKeyPairPath); os.IsNotExist(err) {
		key, err := wgtypes.GeneratePrivateKey()
		if err != nil {
			return scribble.ErrMissingCollection
		}
		serverKeyPair := new(model.ServerKeypair)
		serverKeyPair.PrivateKey = key.String()
		serverKeyPair.PublicKey = key.PublicKey().String()
		serverKeyPair.UpdatedAt = time.Now().UTC()
		o.conn.Write("server", "keypair", serverKeyPair)
		err = util.ManagePerms(serverKeyPairPath)
		if err != nil {
			return err
		}
	}

	// global settings
	if _, err := os.Stat(globalSettingPath); os.IsNotExist(err) {
		endpointAddress := util.LookupEnvOrString(util.EndpointAddressEnvVar, "")
		if endpointAddress == "" {
			// automatically find an external IP address
			publicInterface, err := util.GetPublicIP()
			if err != nil {
				return err
			}
			endpointAddress = publicInterface.IPAddress
		}

		globalSetting := new(model.GlobalSetting)
		globalSetting.EndpointAddress = endpointAddress
		globalSetting.DNSServers = util.LookupEnvOrStrings(util.DNSEnvVar, []string{util.DefaultDNS})
		globalSetting.MTU = util.LookupEnvOrInt(util.MTUEnvVar, util.DefaultMTU)
		globalSetting.PersistentKeepalive = util.LookupEnvOrInt(util.PersistentKeepaliveEnvVar, util.DefaultPersistentKeepalive)
		globalSetting.FirewallMark = util.LookupEnvOrString(util.FirewallMarkEnvVar, util.DefaultFirewallMark)
		globalSetting.Table = util.LookupEnvOrString(util.TableEnvVar, util.DefaultTable)
		globalSetting.ConfigFilePath = util.LookupEnvOrString(util.ConfigFilePathEnvVar, util.DefaultConfigFilePath)
		globalSetting.UpdatedAt = time.Now().UTC()
		o.conn.Write("server", "global_settings", globalSetting)
		err := util.ManagePerms(globalSettingPath)
		if err != nil {
			return err
		}
	}

	// hashes
	if _, err := os.Stat(hashesPath); os.IsNotExist(err) {
		clientServerHashes := new(model.ClientServerHashes)
		clientServerHashes.Client = "none"
		clientServerHashes.Server = "none"
		o.conn.Write("server", "hashes", clientServerHashes)
		err := util.ManagePerms(hashesPath)
		if err != nil {
			return err
		}
	}

	// user info
	results, err := o.conn.ReadAll("users")
	if err != nil || len(results) < 1 {
		user := new(model.User)
		user.Username = util.LookupEnvOrString(util.UsernameEnvVar, util.DefaultUsername)
		user.Admin = util.DefaultIsAdmin
		user.PasswordHash = util.LookupEnvOrString(util.PasswordHashEnvVar, "")
		if user.PasswordHash == "" {
			user.PasswordHash = util.LookupEnvOrFile(util.PasswordHashFileEnvVar, "")
			if user.PasswordHash == "" {
				plaintext := util.LookupEnvOrString(util.PasswordEnvVar, util.DefaultPassword)
				if plaintext == util.DefaultPassword {
					plaintext = util.LookupEnvOrFile(util.PasswordFileEnvVar, util.DefaultPassword)
				}
				hash, err := util.HashPassword(plaintext)
				if err != nil {
					return err
				}
				user.PasswordHash = hash
			}
		}

		o.conn.Write("users", user.Username, user)
		results, _ = o.conn.ReadAll("users")
		err = util.ManagePerms(path.Join(path.Join(o.dbPath, "users"), user.Username+".json"))
		if err != nil {
			return err
		}
	}

	// migrate legacy single-server layout to the new multi-server layout
	if err := o.migrateLegacyServer(); err != nil {
		return err
	}

	// init cache
	for _, i := range results {
		user := model.User{}

		if err := json.Unmarshal([]byte(i), &user); err == nil {
			util.DBUsersToCRC32[user.Username] = util.GetDBUserCRC32(user)
		}
	}

	clients, err := o.GetClients(false)
	if err != nil {
		return nil
	}
	for _, cl := range clients {
		client := cl.Client
		if client.Enabled && len(client.TgUserid) > 0 {
			if userid, err := strconv.ParseInt(client.TgUserid, 10, 64); err == nil {
				util.UpdateTgToClientID(userid, client.ID)
			}
		}
	}

	return nil
}

// migrateLegacyServer detects a pre-multi-server DB layout (single
// "server" collection, no "servers" registry yet) and migrates it into
// the new per-server layout ("servers/<id>.json", "server_settings/<id>.json",
// "server_hashes/<id>.json"), backfilling ServerID on every existing client.
// It is idempotent: it only runs once, guarded by the absence of the
// "servers" directory, and never deletes or modifies the legacy "server"
// collection - existing store methods keep reading/writing it directly
// until they are switched over to the new layout in a later step.
func (o *JsonDB) migrateLegacyServer() error {
	legacyServerPath := path.Join(o.dbPath, "server")
	legacyInterfacePath := path.Join(legacyServerPath, "interfaces.json")
	newServersPath := path.Join(o.dbPath, "servers")

	if _, err := os.Stat(legacyInterfacePath); os.IsNotExist(err) {
		// nothing to migrate (fresh install)
		return nil
	}
	if _, err := os.Stat(newServersPath); err == nil {
		// already migrated
		return nil
	}

	var legacyInterface model.ServerInterface
	if err := o.conn.Read("server", "interfaces", &legacyInterface); err != nil {
		return fmt.Errorf("migration: cannot read legacy server interface: %v", err)
	}
	var legacyKeyPair model.ServerKeypair
	if err := o.conn.Read("server", "keypair", &legacyKeyPair); err != nil {
		return fmt.Errorf("migration: cannot read legacy server keypair: %v", err)
	}
	var legacyGlobalSettings model.GlobalSetting
	if err := o.conn.Read("server", "global_settings", &legacyGlobalSettings); err != nil {
		return fmt.Errorf("migration: cannot read legacy global settings: %v", err)
	}
	var legacyHashes model.ClientServerHashes
	hasHashes := true
	if err := o.conn.Read("server", "hashes", &legacyHashes); err != nil {
		hasHashes = false
	}

	serverID := legacyDefaultServerID
	ifaceName := legacyDefaultServerID
	if legacyGlobalSettings.ConfigFilePath != "" {
		base := path.Base(legacyGlobalSettings.ConfigFilePath)
		if strings.HasSuffix(base, ".conf") {
			ifaceName = strings.TrimSuffix(base, ".conf")
		}
	}

	legacyInterface.Name = ifaceName

	server := model.Server{
		ID:        serverID,
		Name:      "Default Server",
		KeyPair:   &legacyKeyPair,
		Interface: &legacyInterface,
	}
	if err := o.conn.Write("servers", serverID, server); err != nil {
		return fmt.Errorf("migration: cannot write servers/%s.json: %v", serverID, err)
	}
	if err := util.ManagePerms(path.Join(newServersPath, serverID+".json")); err != nil {
		return err
	}

	serverSetting := model.ServerSetting{
		EndpointAddress: legacyGlobalSettings.EndpointAddress,
		FirewallMark:    legacyGlobalSettings.FirewallMark,
		Table:           legacyGlobalSettings.Table,
		ConfigFilePath:  legacyGlobalSettings.ConfigFilePath,
		UpdatedAt:       time.Now().UTC(),
	}
	if err := o.conn.Write("server_settings", serverID, serverSetting); err != nil {
		return fmt.Errorf("migration: cannot write server_settings/%s.json: %v", serverID, err)
	}
	if err := util.ManagePerms(path.Join(o.dbPath, "server_settings", serverID+".json")); err != nil {
		return err
	}

	if hasHashes {
		if err := o.conn.Write("server_hashes", serverID, legacyHashes); err != nil {
			return fmt.Errorf("migration: cannot write server_hashes/%s.json: %v", serverID, err)
		}
		if err := util.ManagePerms(path.Join(o.dbPath, "server_hashes", serverID+".json")); err != nil {
			return err
		}
	}

	// backfill ServerID on every existing client
	clientRecords, err := o.conn.ReadAll("clients")
	if err != nil && err != scribble.ErrMissingCollection {
		return fmt.Errorf("migration: cannot read clients: %v", err)
	}
	for _, rec := range clientRecords {
		var client model.Client
		if err := json.Unmarshal(rec, &client); err != nil {
			return fmt.Errorf("migration: cannot decode client json: %v", err)
		}
		if client.ServerID != "" {
			continue
		}
		client.ServerID = serverID
		if err := o.conn.Write("clients", client.ID, client); err != nil {
			return fmt.Errorf("migration: cannot backfill server_id on client %s: %v", client.ID, err)
		}
	}

	// backfill ServerIDs on every existing user so nobody is locked out of
	// the migrated server by the new per-server access control (users
	// created after migration default to no access, per model.User).
	userRecords, err := o.conn.ReadAll("users")
	if err != nil && err != scribble.ErrMissingCollection {
		return fmt.Errorf("migration: cannot read users: %v", err)
	}
	for _, rec := range userRecords {
		var user model.User
		if err := json.Unmarshal(rec, &user); err != nil {
			return fmt.Errorf("migration: cannot decode user json: %v", err)
		}
		if len(user.ServerIDs) > 0 {
			continue
		}
		user.ServerIDs = []string{serverID}
		if err := o.conn.Write("users", user.Username, user); err != nil {
			return fmt.Errorf("migration: cannot backfill server_ids on user %s: %v", user.Username, err)
		}
	}

	// NOTE: the legacy "server" directory is intentionally left in place
	// (not renamed/removed). GetGlobalSettings/SaveGlobalSettings still read
	// and write the app-wide settings record there (DNS/MTU/
	// PersistentKeepalive are not yet per-server concerns); every other
	// server-scoped read/write now goes exclusively through the per-server
	// registry (servers/<id>.json via GetServerByID/UpdateServerInterface/
	// UpdateServerKeyPair/GetServerSettings), so this directory is kept only
	// as a landing spot for one-time migration and for global settings.
	log.Printf("Migrated legacy single-server DB to multi-server layout (server id: %s); legacy db/server/ kept in place for now", serverID)
	return nil
}

// GetUsers func to get all users from the database
func (o *JsonDB) GetUsers() ([]model.User, error) {
	var users []model.User
	results, err := o.conn.ReadAll("users")
	if err != nil {
		return users, err
	}
	for _, i := range results {
		user := model.User{}

		if err := json.Unmarshal(i, &user); err != nil {
			return users, fmt.Errorf("cannot decode user json structure: %v", err)
		}
		users = append(users, user)
	}
	return users, err
}

// GetUserByName func to get single user from the database
func (o *JsonDB) GetUserByName(username string) (model.User, error) {
	user := model.User{}

	if err := o.conn.Read("users", username, &user); err != nil {
		return user, err
	}

	return user, nil
}

// SaveUser func to save user in the database
func (o *JsonDB) SaveUser(user model.User) error {
	userPath := path.Join(path.Join(o.dbPath, "users"), user.Username+".json")
	output := o.conn.Write("users", user.Username, user)
	err := util.ManagePerms(userPath)
	if err != nil {
		return err
	}
	util.DBUsersToCRC32[user.Username] = util.GetDBUserCRC32(user)
	return output
}

// DeleteUser func to remove user from the database
func (o *JsonDB) DeleteUser(username string) error {
	delete(util.DBUsersToCRC32, username)
	return o.conn.Delete("users", username)
}

// GetGlobalSettings func to query global settings from the database
func (o *JsonDB) GetGlobalSettings() (model.GlobalSetting, error) {
	settings := model.GlobalSetting{}
	return settings, o.conn.Read("server", "global_settings", &settings)
}

func (o *JsonDB) GetClients(hasQRCode bool) ([]model.ClientData, error) {
	var clients []model.ClientData

	// read all client json files in "clients" directory
	records, err := o.conn.ReadAll("clients")
	if err != nil {
		return clients, err
	}

	// build the ClientData list
	for _, f := range records {
		client := model.Client{}
		clientData := model.ClientData{}

		// get client info
		if err := json.Unmarshal(f, &client); err != nil {
			return clients, fmt.Errorf("cannot decode client json structure: %v", err)
		}

		// generate client qrcode image in base64
		if hasQRCode && client.PrivateKey != "" {
			server, _ := o.GetServerByID(util.DefaultServerID)
			globalSettings, _ := o.GetGlobalSettings()

			png, err := qrcode.Encode(util.BuildClientConfig(client, server, globalSettings), qrcode.Medium, 256)
			if err == nil {
				clientData.QRCode = "data:image/png;base64," + base64.StdEncoding.EncodeToString(png)
			} else {
				fmt.Print("Cannot generate QR code: ", err)
			}
		}

		// create the list of clients and their qrcode data
		clientData.Client = &client
		clients = append(clients, clientData)
	}

	return clients, nil
}

func (o *JsonDB) GetClientByID(clientID string, qrCodeSettings model.QRCodeSettings) (model.ClientData, error) {
	client := model.Client{}
	clientData := model.ClientData{}

	// read client information
	if err := o.conn.Read("clients", clientID, &client); err != nil {
		return clientData, err
	}

	// generate client qrcode image in base64
	if qrCodeSettings.Enabled && client.PrivateKey != "" {
		server, _ := o.GetServerByID(util.DefaultServerID)
		globalSettings, _ := o.GetGlobalSettings()
		client := client
		if !qrCodeSettings.IncludeDNS {
			globalSettings.DNSServers = []string{}
		}
		if !qrCodeSettings.IncludeMTU {
			globalSettings.MTU = 0
		}

		png, err := qrcode.Encode(util.BuildClientConfig(client, server, globalSettings), qrcode.Medium, 256)
		if err == nil {
			clientData.QRCode = "data:image/png;base64," + base64.StdEncoding.EncodeToString(png)
		} else {
			fmt.Print("Cannot generate QR code: ", err)
		}
	}

	clientData.Client = &client

	return clientData, nil
}

func (o *JsonDB) SaveClient(client model.Client) error {
	clientPath := path.Join(path.Join(o.dbPath, "clients"), client.ID+".json")
	output := o.conn.Write("clients", client.ID, client)
	if output == nil {
		if client.Enabled && len(client.TgUserid) > 0 {
			if userid, err := strconv.ParseInt(client.TgUserid, 10, 64); err == nil {
				util.UpdateTgToClientID(userid, client.ID)
			}
		} else {
			util.RemoveTgToClientID(client.ID)
		}
	} else {
		util.RemoveTgToClientID(client.ID)
	}
	err := util.ManagePerms(clientPath)
	if err != nil {
		return err
	}
	return output
}

func (o *JsonDB) DeleteClient(clientID string) error {
	util.RemoveTgToClientID(clientID)
	return o.conn.Delete("clients", clientID)
}

func (o *JsonDB) SaveGlobalSettings(globalSettings model.GlobalSetting) error {
	globalSettingsPath := path.Join(path.Join(o.dbPath, "server"), "global_settings.json")
	output := o.conn.Write("server", "global_settings", globalSettings)
	err := util.ManagePerms(globalSettingsPath)
	if err != nil {
		return err
	}
	return output
}

func (o *JsonDB) GetPath() string {
	return o.dbPath
}

func (o *JsonDB) GetHashes() (model.ClientServerHashes, error) {
	hashes := model.ClientServerHashes{}
	return hashes, o.conn.Read("server", "hashes", &hashes)
}

func (o *JsonDB) SaveHashes(hashes model.ClientServerHashes) error {
	hashesPath := path.Join(path.Join(o.dbPath, "server"), "hashes.json")
	output := o.conn.Write("server", "hashes", hashes)
	err := util.ManagePerms(hashesPath)
	if err != nil {
		return err
	}
	return output
}

// UpdateServerInterface func updates the Interface of an existing server
func (o *JsonDB) UpdateServerInterface(serverID string, serverInterface model.ServerInterface) error {
	if err := validateServerID(serverID); err != nil {
		return err
	}
	server, err := o.GetServerByID(serverID)
	if err != nil {
		return err
	}
	server.Interface = &serverInterface
	if err := o.conn.Write("servers", serverID, server); err != nil {
		return err
	}
	return util.ManagePerms(path.Join(o.dbPath, "servers", serverID+".json"))
}

// UpdateServerKeyPair func updates the KeyPair of an existing server
func (o *JsonDB) UpdateServerKeyPair(serverID string, serverKeyPair model.ServerKeypair) error {
	if err := validateServerID(serverID); err != nil {
		return err
	}
	server, err := o.GetServerByID(serverID)
	if err != nil {
		return err
	}
	server.KeyPair = &serverKeyPair
	if err := o.conn.Write("servers", serverID, server); err != nil {
		return err
	}
	return util.ManagePerms(path.Join(o.dbPath, "servers", serverID+".json"))
}

// GetServers func to get all servers from the database
func (o *JsonDB) GetServers() ([]model.Server, error) {
	var servers []model.Server
	results, err := o.conn.ReadAll("servers")
	if err != nil {
		if err == scribble.ErrMissingCollection {
			return servers, nil
		}
		return servers, err
	}
	for _, i := range results {
		server := model.Server{}
		if err := json.Unmarshal([]byte(i), &server); err != nil {
			return servers, fmt.Errorf("cannot decode server json structure: %v", err)
		}
		servers = append(servers, server)
	}
	return servers, nil
}

// validateServerID checks a server ID before it is ever used as a jsondb
// record key, shared by every server-scoped store method below.
func validateServerID(serverID string) error {
	if !util.ValidateRecordID(serverID) {
		return fmt.Errorf("invalid server id: %s", serverID)
	}
	return nil
}

// GetServerByID func to query a single server by id from the database
func (o *JsonDB) GetServerByID(serverID string) (model.Server, error) {
	server := model.Server{}
	if err := validateServerID(serverID); err != nil {
		return server, err
	}
	err := o.conn.Read("servers", serverID, &server)
	return server, err
}

// CreateServer func to create a new server in the database
func (o *JsonDB) CreateServer(server model.Server) error {
	if server.ID == "" {
		return fmt.Errorf("cannot create server: missing id")
	}
	if err := validateServerID(server.ID); err != nil {
		return err
	}
	if server.Interface != nil && server.Interface.Name != "" && !util.ValidateInterfaceName(server.Interface.Name) {
		return fmt.Errorf("invalid interface name: %s", server.Interface.Name)
	}
	if err := o.conn.Write("servers", server.ID, server); err != nil {
		return err
	}
	return util.ManagePerms(path.Join(o.dbPath, "servers", server.ID+".json"))
}

// DeleteServer func to remove a server from the database, refusing if
// any client still references it
func (o *JsonDB) DeleteServer(serverID string) error {
	if err := validateServerID(serverID); err != nil {
		return err
	}
	records, err := o.conn.ReadAll("clients")
	if err != nil && err != scribble.ErrMissingCollection {
		return err
	}
	count := 0
	for _, rec := range records {
		var client model.Client
		if err := json.Unmarshal(rec, &client); err != nil {
			return fmt.Errorf("cannot decode client json structure: %v", err)
		}
		if client.ServerID == serverID {
			count++
		}
	}
	if count > 0 {
		return fmt.Errorf("cannot delete server %s: %d client(s) still reference it", serverID, count)
	}
	return o.conn.Delete("servers", serverID)
}

// GetServerSettings func to query per-server settings from the database
func (o *JsonDB) GetServerSettings(serverID string) (model.ServerSetting, error) {
	settings := model.ServerSetting{}
	if err := validateServerID(serverID); err != nil {
		return settings, err
	}
	return settings, o.conn.Read("server_settings", serverID, &settings)
}

// SaveServerSettings func to save per-server settings in the database
func (o *JsonDB) SaveServerSettings(serverID string, settings model.ServerSetting) error {
	if err := validateServerID(serverID); err != nil {
		return err
	}
	settingsPath := path.Join(o.dbPath, "server_settings", serverID+".json")
	output := o.conn.Write("server_settings", serverID, settings)
	err := util.ManagePerms(settingsPath)
	if err != nil {
		return err
	}
	return output
}

// GetServerHashes func to query per-server client/server hashes from the database
func (o *JsonDB) GetServerHashes(serverID string) (model.ClientServerHashes, error) {
	hashes := model.ClientServerHashes{}
	if err := validateServerID(serverID); err != nil {
		return hashes, err
	}
	return hashes, o.conn.Read("server_hashes", serverID, &hashes)
}

// SaveServerHashes func to save per-server client/server hashes in the database
func (o *JsonDB) SaveServerHashes(serverID string, hashes model.ClientServerHashes) error {
	if err := validateServerID(serverID); err != nil {
		return err
	}
	hashesPath := path.Join(o.dbPath, "server_hashes", serverID+".json")
	output := o.conn.Write("server_hashes", serverID, hashes)
	err := util.ManagePerms(hashesPath)
	if err != nil {
		return err
	}
	return output
}