package shares

import (
	"errors"
	"fmt"
	"net"
	"path"
	"regexp"
	"strings"
)

var (
	reShareName = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9_.-]{0,79}$`)
	reWorkgroup = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9_-]{0,14}$`)
	reUser      = regexp.MustCompile(`^[a-z_][a-z0-9_-]{0,31}$`)
	reHost      = regexp.MustCompile(`^[A-Za-z0-9*][A-Za-z0-9*.-]{0,253}$`)
	reComment   = regexp.MustCompile(`^[^\r\n\[\]]{0,120}$`)
)

// reserved Samba section names that must not be used as share names.
var reservedShares = map[string]bool{"global": true, "homes": true, "printers": true, "print$": true}

func ValidateShareName(s string) error {
	if !reShareName.MatchString(s) {
		return errors.New("share name: 1-80 characters, letters, digits, _ . - and must start with a letter or digit")
	}
	if reservedShares[strings.ToLower(s)] {
		return fmt.Errorf("share name %q is reserved by Samba", s)
	}
	return nil
}

func ValidateWorkgroup(s string) error {
	if !reWorkgroup.MatchString(s) {
		return errors.New("workgroup: 1-15 characters, letters, digits, _ -")
	}
	return nil
}

func ValidateUserName(s string) error {
	if !reUser.MatchString(s) {
		return errors.New("user name: lowercase letters, digits, _ -, up to 32 characters")
	}
	if s == "root" || s == "nobody" {
		return fmt.Errorf("user %s cannot be an SMB user", s)
	}
	return nil
}

func ValidateComment(s string) error {
	if !reComment.MatchString(s) {
		return errors.New("comment: up to 120 characters, no [ ] or line breaks")
	}
	return nil
}

// systemRoots are OS trees that must never be shared.
var systemRoots = []string{"/etc", "/proc", "/sys", "/dev", "/boot", "/run", "/usr", "/bin", "/sbin",
	"/lib", "/lib32", "/lib64", "/libx32", "/var", "/root", "/snap", "/lost+found"}

// ValidateNotSystem refuses the root filesystem and system directories.
func ValidateNotSystem(p string) error {
	if p == "/" {
		return errors.New("refusing to share the root filesystem")
	}
	if UnderRoots(p, systemRoots) {
		return fmt.Errorf("%s is a system directory and cannot be shared", p)
	}
	return nil
}

// ValidatePath accepts an absolute, clean, non-system path without control
// characters. Existence and symlinks are checked by the caller.
func ValidatePath(p string) error {
	if p == "" {
		return errors.New("path is required")
	}
	if !strings.HasPrefix(p, "/") || path.Clean(p) != p || strings.ContainsAny(p, "\"\\\r\n\t") {
		return errors.New("path must be absolute and normalised (no .., trailing / or quotes)")
	}
	return ValidateNotSystem(p)
}

// UnderRoots reports whether p equals or lies below one of the roots.
func UnderRoots(p string, roots []string) bool {
	for _, r := range roots {
		if r == "" || r == "/" {
			continue
		}
		if p == r || strings.HasPrefix(p, r+"/") {
			return true
		}
	}
	return false
}

// ValidateClient accepts *, a host name (wildcards allowed), an IP or a CIDR.
func ValidateClient(c string) error {
	if c == "*" {
		return nil
	}
	if strings.Contains(c, "/") {
		if _, _, err := net.ParseCIDR(c); err != nil {
			return fmt.Errorf("client %q: bad network, use e.g. 192.168.1.0/24", c)
		}
		return nil
	}
	if net.ParseIP(c) != nil || reHost.MatchString(c) {
		return nil
	}
	return fmt.Errorf("client %q: use a host name, IP address, network (CIDR) or *", c)
}

func (s SMBShare) Validate() error {
	if err := ValidateShareName(s.Name); err != nil {
		return err
	}
	if err := ValidatePath(s.Path); err != nil {
		return err
	}
	if err := ValidateComment(s.Comment); err != nil {
		return err
	}
	if !s.Guest && len(s.Users) == 0 {
		return fmt.Errorf("share %s: allow guests or pick at least one user", s.Name)
	}
	for _, u := range s.Users {
		if err := ValidateUserName(u); err != nil {
			return err
		}
	}
	return nil
}

func (e NFSExport) Validate() error {
	if err := ValidatePath(e.Path); err != nil {
		return err
	}
	if len(e.Clients) == 0 {
		return fmt.Errorf("export %s: at least one client is required (or *)", e.Path)
	}
	for _, c := range e.Clients {
		if err := ValidateClient(c); err != nil {
			return err
		}
	}
	switch e.Squash {
	case "root", "all", "none":
	default:
		return errors.New("squash must be root, all or none")
	}
	return nil
}

// SplitList turns "a, b;c\nd" into ["a","b","c","d"].
func SplitList(s string) []string {
	var out []string
	for _, f := range strings.FieldsFunc(s, func(r rune) bool { return r == ',' || r == ';' || r == '\n' || r == ' ' || r == '\t' || r == '\r' }) {
		if f = strings.TrimSpace(f); f != "" {
			out = append(out, f)
		}
	}
	return out
}