package main

import (
	"database/sql"
	"errors"
	"fmt"
	"io"
	"log"
	"os"
	"path/filepath"
	"strconv"
	"strings"

	ftpserver "goftp.io/server/v2"
)

func startProtocolServers(cfg Config, db *sql.DB) error {
	if cfg.SFTPEnabled {
		return fmt.Errorf("SFTP_ENABLED=true is configured, but SFTP server is not implemented")
	}

	if cfg.FTPEnabled {
		ftpSrv, err := buildFTPServer(cfg, db)
		if err != nil {
			return fmt.Errorf("build ftp server: %w", err)
		}
		go runFTPServer("FTP", ftpSrv)
	}

	if cfg.FTPSEnabled {
		ftpsSrv, err := buildFTPSServer(cfg, db)
		if err != nil {
			return fmt.Errorf("build ftps server: %w", err)
		}
		go runFTPServer("FTPS", ftpsSrv)
	}

	return nil
}

func runFTPServer(name string, srv *ftpserver.Server) {
	log.Printf("%s listening on %s:%d", name, srv.Hostname, srv.Port)
	if err := srv.ListenAndServe(); err != nil && !errors.Is(err, ftpserver.ErrServerClosed) {
		log.Printf("%s server stopped: %v", name, err)
	}
}

type ftpUserDriver struct {
	db   *sql.DB
	root string
}

func buildFTPServer(cfg Config, db *sql.DB) (*ftpserver.Server, error) {
	return buildFileZFTPServer(ftpServerOptions{
		name:         "FileZ FTP",
		host:         cfg.FTPHost,
		port:         cfg.FTPPort,
		publicIP:     cfg.FTPPublicIP,
		passivePorts: cfg.FTPPassivePorts,
		tls:          false,
	}, db, cfg.StorageRoot)
}

func buildFTPSServer(cfg Config, db *sql.DB) (*ftpserver.Server, error) {
	return buildFileZFTPServer(ftpServerOptions{
		name:         "FileZ FTPS",
		host:         cfg.FTPSHost,
		port:         cfg.FTPSPort,
		publicIP:     cfg.FTPSPublicIP,
		passivePorts: cfg.FTPSPassivePorts,
		tls:          true,
		certFile:     cfg.FTPSCertFile,
		keyFile:      cfg.FTPSKeyFile,
		explicitFTPS: cfg.FTPSExplicit,
		forceTLS:     cfg.FTPSForceTLS,
	}, db, cfg.StorageRoot)
}

type ftpServerOptions struct {
	name         string
	host         string
	port         int
	publicIP     string
	passivePorts string
	tls          bool
	certFile     string
	keyFile      string
	explicitFTPS bool
	forceTLS     bool
}

func buildFileZFTPServer(opts ftpServerOptions, db *sql.DB, storageRoot string) (*ftpserver.Server, error) {
	drv := &ftpUserDriver{db: db, root: storageRoot}
	serverOpts := &ftpserver.Options{
		Name:           opts.name,
		Hostname:       opts.host,
		Port:           opts.port,
		PublicIP:       opts.publicIP,
		PassivePorts:   opts.passivePorts,
		WelcomeMessage: opts.name + " ready",
		Driver:         drv,
		Auth:           drv,
		Perm:           ftpserver.NewSimplePerm("filez", "filez"),
		TLS:            opts.tls,
		CertFile:       opts.certFile,
		KeyFile:        opts.keyFile,
		ExplicitFTPS:   opts.explicitFTPS,
		ForceTLS:       opts.forceTLS,
	}
	return ftpserver.NewServer(serverOpts)
}

func (d *ftpUserDriver) CheckPasswd(ctx *ftpserver.Context, username, password string) (bool, error) {
	username = strings.TrimSpace(username)
	if username == "" {
		return false, nil
	}

	var userID int64
	var hash string
	err := d.db.QueryRow(`SELECT id, password_hash FROM users WHERE email = ?`, username).Scan(&userID, &hash)
	if err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			return false, nil
		}
		return false, err
	}
	if !verifyPasswordHash(hash, password) {
		return false, nil
	}

	if err := os.MkdirAll(d.userRoot(userID), 0o755); err != nil {
		return false, err
	}
	d.setUserID(ctx, userID)
	return true, nil
}

func (d *ftpUserDriver) userRoot(userID int64) string {
	return filepath.Join(d.root, strconv.FormatInt(userID, 10))
}

func (d *ftpUserDriver) setUserID(ctx *ftpserver.Context, userID int64) {
	if ctx == nil || ctx.Sess == nil {
		return
	}
	if ctx.Sess.Data == nil {
		ctx.Sess.Data = make(map[string]interface{})
	}
	ctx.Sess.Data["filez_user_id"] = userID
}

func (d *ftpUserDriver) userIDFromCtx(ctx *ftpserver.Context) (int64, error) {
	if ctx == nil || ctx.Sess == nil {
		return 0, fmt.Errorf("missing ftp session")
	}

	if v, ok := ctx.Sess.Data["filez_user_id"]; ok {
		switch id := v.(type) {
		case int64:
			if id > 0 {
				return id, nil
			}
		case int:
			if id > 0 {
				return int64(id), nil
			}
		}
	}

	username := strings.TrimSpace(ctx.Sess.LoginUser())
	if username == "" {
		return 0, fmt.Errorf("missing ftp username")
	}

	var userID int64
	if err := d.db.QueryRow(`SELECT id FROM users WHERE email = ?`, username).Scan(&userID); err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			return 0, fmt.Errorf("user not found")
		}
		return 0, err
	}
	d.setUserID(ctx, userID)
	return userID, nil
}

func (d *ftpUserDriver) fullPath(ctx *ftpserver.Context, rel string) (string, error) {
	userID, err := d.userIDFromCtx(ctx)
	if err != nil {
		return "", err
	}
	root := d.userRoot(userID)
	if err := os.MkdirAll(root, 0o755); err != nil {
		return "", err
	}

	clean := filepath.FromSlash(strings.TrimPrefix(normalizePath(rel), "/"))
	full := filepath.Clean(filepath.Join(root, clean))
	if full != root && !strings.HasPrefix(full, root+string(os.PathSeparator)) {
		return "", fmt.Errorf("invalid path")
	}
	return full, nil
}

func (d *ftpUserDriver) Stat(ctx *ftpserver.Context, rel string) (os.FileInfo, error) {
	full, err := d.fullPath(ctx, rel)
	if err != nil {
		return nil, err
	}
	return os.Stat(full)
}

func (d *ftpUserDriver) ListDir(ctx *ftpserver.Context, rel string, callback func(os.FileInfo) error) error {
	full, err := d.fullPath(ctx, rel)
	if err != nil {
		return err
	}
	entries, err := os.ReadDir(full)
	if err != nil {
		return err
	}
	for _, entry := range entries {
		info, err := entry.Info()
		if err != nil {
			continue
		}
		if err := callback(info); err != nil {
			return err
		}
	}
	return nil
}

func (d *ftpUserDriver) DeleteDir(ctx *ftpserver.Context, rel string) error {
	if normalizePath(rel) == "/" {
		return fmt.Errorf("cannot remove root directory")
	}
	full, err := d.fullPath(ctx, rel)
	if err != nil {
		return err
	}
	st, err := os.Stat(full)
	if err != nil {
		return err
	}
	if !st.IsDir() {
		return fmt.Errorf("not a directory")
	}
	return os.RemoveAll(full)
}

func (d *ftpUserDriver) DeleteFile(ctx *ftpserver.Context, rel string) error {
	full, err := d.fullPath(ctx, rel)
	if err != nil {
		return err
	}
	st, err := os.Stat(full)
	if err != nil {
		return err
	}
	if st.IsDir() {
		return fmt.Errorf("not a file")
	}
	return os.Remove(full)
}

func (d *ftpUserDriver) Rename(ctx *ftpserver.Context, fromPath, toPath string) error {
	if normalizePath(fromPath) == "/" {
		return fmt.Errorf("cannot rename root directory")
	}
	oldPath, err := d.fullPath(ctx, fromPath)
	if err != nil {
		return err
	}
	newPath, err := d.fullPath(ctx, toPath)
	if err != nil {
		return err
	}
	if err := os.MkdirAll(filepath.Dir(newPath), 0o755); err != nil {
		return err
	}
	return os.Rename(oldPath, newPath)
}

func (d *ftpUserDriver) MakeDir(ctx *ftpserver.Context, rel string) error {
	full, err := d.fullPath(ctx, rel)
	if err != nil {
		return err
	}
	return os.MkdirAll(full, 0o755)
}

func (d *ftpUserDriver) GetFile(ctx *ftpserver.Context, rel string, offset int64) (int64, io.ReadCloser, error) {
	full, err := d.fullPath(ctx, rel)
	if err != nil {
		return 0, nil, err
	}
	f, err := os.Open(full)
	if err != nil {
		return 0, nil, err
	}
	defer func() {
		if err != nil {
			_ = f.Close()
		}
	}()

	st, err := f.Stat()
	if err != nil {
		return 0, nil, err
	}
	if offset < 0 {
		offset = 0
	}
	if _, err := f.Seek(offset, io.SeekStart); err != nil {
		return 0, nil, err
	}
	sz := st.Size() - offset
	if sz < 0 {
		sz = 0
	}
	return sz, f, nil
}

func (d *ftpUserDriver) PutFile(ctx *ftpserver.Context, rel string, data io.Reader, offset int64) (int64, error) {
	full, err := d.fullPath(ctx, rel)
	if err != nil {
		return 0, err
	}
	if err := os.MkdirAll(filepath.Dir(full), 0o755); err != nil {
		return 0, err
	}

	if offset < 0 {
		f, err := os.Create(full)
		if err != nil {
			return 0, err
		}
		defer f.Close()
		return io.Copy(f, data)
	}

	flags := os.O_CREATE | os.O_WRONLY
	if offset == 0 {
		flags |= os.O_TRUNC
	}
	f, err := os.OpenFile(full, flags, 0o644)
	if err != nil {
		return 0, err
	}
	defer f.Close()
	if _, err := f.Seek(offset, io.SeekStart); err != nil {
		return 0, err
	}
	return io.Copy(f, data)
}