rstango 0.4.0

//! Types for the names Tango gives to things: case-ignored names, and type safe Tango
//! Resource Locators.

use std::fmt::{self, Debug, Display};
use std::hash::{Hash, Hasher};
use std::convert::Infallible;
use std::borrow::Borrow;
use std::num::NonZero;
use std::str::FromStr;
use std::ops::Deref;
use std::sync::Arc;


/// A name of something Tango names, compared and hashed the way Tango compares such a
/// name: ignoring the case, and on ASCII alone, every name Tango has being ASCII.
/// 
/// Which is what a server has to do of the names of its classes, of its devices, and of
/// the commands and attributes of each of them: cppTango lowercases every one of them
/// before it looks it up, and the database, being a SQL one, matches them the same way.
/// A name is kept as it was given all the same, because it is also what a client is shown.
#[repr(transparent)]
pub struct Name(str);

impl Name {

    /// Borrow a string as a name, which costs nothing: a name is a [`str`] with another
    /// comparison and nothing else.
    #[inline]
    pub fn new(name: &str) -> &Self {
        // SAFETY: Name is a repr(transparent) wrapper around str, so a reference to one is
        // a reference to the other.
        unsafe { &*(name as *const str as *const Self) }
    }

    /// Return the name as it was given, with its case.
    #[inline]
    pub fn as_str(&self) -> &str {
        &self.0
    }

    /// Copy the name into an owned one.
    #[inline]
    pub fn to_arc(&self) -> ArcName {
        ArcName(Arc::from(&self.0))
    }

}

impl PartialEq for Name {
    #[inline]
    fn eq(&self, other: &Self) -> bool {
        self.0.eq_ignore_ascii_case(&other.0)
    }
}

impl Eq for Name {}

impl Hash for Name {
    fn hash<H: Hasher>(&self, state: &mut H) {
        // Byte by byte rather than hashing the lowercased name, which would mean allocating
        // one on every lookup, with the same terminator `str` itself writes so that two
        // names one of which is a prefix of the other do not hash alike.
        for byte in self.0.bytes() {
            state.write_u8(byte.to_ascii_lowercase());
        }
        state.write_u8(0xff);
    }
}

impl Debug for Name {
    #[inline]
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        Debug::fmt(&self.0, f)
    }
}

impl Display for Name {
    #[inline]
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        Display::fmt(&self.0, f)
    }
}

/// Atomic counted reference to a [`Name`].
pub struct ArcName(Arc<str>);

impl From<Arc<str>> for ArcName {
    fn from(value: Arc<str>) -> Self {
        Self(value)
    }
}

impl From<&str> for ArcName {
    #[inline]
    fn from(value: &str) -> Self {
        Self(Arc::from(value))
    }
}

impl FromStr for ArcName {

    type Err = Infallible;

    #[inline]
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        Ok(Self::from(s))
    }

}

impl Deref for ArcName {
    type Target = Name;
    #[inline]
    fn deref(&self) -> &Self::Target {
        Name::new(&self.0)
    }
}

impl Borrow<Name> for ArcName {
    #[inline]
    fn borrow(&self) -> &Name {
        self
    }
}

impl PartialEq for ArcName {
    fn eq(&self, other: &Self) -> bool {
        **self == **other
    }
}

impl Eq for ArcName {}

impl Hash for ArcName {
    fn hash<H: Hasher>(&self, state: &mut H) {
        (**self).hash(state);
    }
}

impl Debug for ArcName {
    #[inline]
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        Debug::fmt(&**self, f)
    }
}

impl Display for ArcName {
    #[inline]
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        Display::fmt(&**self, f)
    }
}

// A Tango name is made of ASCII letters, digits, `_` and `-`, starting with a letter or a
// digit, see `is_tango_name_char`; what differs from one kind of name to another is how
// long it may be and how it is split.

fn check_non_empty_name(name: &str) -> bool {
    !name.is_empty() && name.chars().enumerate().all(is_tango_name_char)
}

fn check_non_empty_u8_name(name: &str) -> bool {
    !name.is_empty() && name.len() <= 255 && name.chars().enumerate().all(is_tango_name_char)
}

/// Check if a given Tango class name is valid.
pub fn check_tango_class_name(name: &str) -> bool {
    check_non_empty_name(name)
}

/// Check if a given part of a Tango server name, its executable or its instance, is valid.
pub fn check_tango_server_part_name(part: &str) -> bool {
    check_non_empty_name(part)
}

/// Check if a given Tango server name, `exe/inst`, is valid.
pub fn check_tango_server_name(name: &str) -> bool {
    let Some((exe, inst)) = name.split_once('/') else { return false };
    check_tango_server_part_name(exe) && 
    check_tango_server_part_name(inst)
}

fn check_tango_dev_part_name(part: &str) -> bool {
    !part.is_empty() && part.len() <= 85 && part.chars().enumerate().all(is_tango_name_char)
}

/// Check if a given Tango device name, `domain/family/member`, is valid, each part being
/// at most 85 long. An alias is not a device name, see [`check_tango_alias`].
pub fn check_tango_dev_name(name: &str) -> bool {
    let Some((domain, rest)) = name.split_once('/') else { return false };
    let Some((family, member)) = rest.split_once('/') else { return false };
    check_tango_dev_part_name(domain) &&
    check_tango_dev_part_name(family) &&
    check_tango_dev_part_name(member)
}

/// Check if a given Tango attribute name is valid, at most 255 long.
pub fn check_tango_attr_name(name: &str) -> bool {
    check_non_empty_u8_name(name)
}

/// Check if a given Tango command name is valid, at most 255 long.
pub fn check_tango_command_name(name: &str) -> bool {
    check_non_empty_u8_name(name)
}

/// Check if a given Tango property name is valid, at most 255 long.
pub fn check_tango_property_name(name: &str) -> bool {
    check_non_empty_u8_name(name)
}

/// Check if a given Tango device or attribute alias is valid, at most 255 long.
pub fn check_tango_alias(name: &str) -> bool {
    check_non_empty_u8_name(name)
}

/// An error common for name validation in Tango.
#[derive(thiserror::Error, Debug)]
pub enum TrlError {
    #[error("Invalid protocol, expecting tango://")]
    InvalidProtocol,
    #[error("Invalid host, wrong characters or too long (> 255)")]
    InvalidHost,
    #[error("Invalid port, expecting non-null 16-bit integer")]
    InvalidPort,
    #[error("Invalid hash, expecting #dbase=yes/no")]
    InvalidHash,
    #[error("Invalid or missing path, device-name[/attribute] with device-name being an alias or domain/family/member")]
    InvalidPath,
    #[error("Invalid device name, wrong characters or too long (> 85 per domain/family/member)")]
    InvalidDevName,
    #[error("Invalid attribute name, wrong characters or too long (> 255)")]
    InvalidAttrName,
    #[error("Invalid device or attribute alias, wrong characters or too long (> 255)")]
    InvalidAlias,
    #[error("Invalid property name, wrong characters or too long (> 255)")]
    InvalidPropName,
}

/// Tango Resource Locator, borrowing the string it was parsed from.
/// 
/// This is a custom reference: it is [`Copy`] and parsing one allocates nothing, the
/// owned counterpart being [`ArcTrl`].
/// 
/// RFC: 
/// - <https://tango-controls.readthedocs.io/projects/rfc/en/latest/16/TangoResourceLocator.html>
/// - <https://tango-controls.readthedocs.io/projects/rfc/en/latest/2/Device.html>
/// - <https://tango-controls.readthedocs.io/projects/rfc/en/latest/4/Attribute.html>
/// - <https://tango-controls.readthedocs.io/projects/rfc/en/latest/5/Property.html>
#[derive(Clone, Copy)]
pub struct Trl<'a> {
    /// The raw string.
    raw: &'a str,
    /// Where the parts are in the raw string.
    meta: TrlMeta,
}

/// Tango Resource Locator, owning the string it was parsed from.
/// 
/// Cloning this structure is cheap because it is backed by an Arc, and [`Self::as_trl`]
/// gives the [`Trl`] to read it through.
#[derive(Clone)]
pub struct ArcTrl {
    /// The raw string.
    raw: Arc<str>,
    /// Where the parts are in the raw string.
    meta: TrlMeta,
}

/// Where the parts of a TRL are in its raw string, shared by [`Trl`] and [`ArcTrl`].
#[derive(Debug, Clone, Copy)]
struct TrlMeta {
    /// If the host and port are present, this is the length of it.
    host_len_and_port: Option<(NonZero<u8>, NonZero<u16>)>,
    /// Offset of where the object starts.
    object_index: u16,
    /// Inner description of the object.
    object: TrlObjectMeta,
    /// From RFC 5/Property, maximum property name length is 255.
    property_len: Option<NonZero<u8>>,
    /// True if the tango:// protocol is present.
    protocol: bool,
    /// True if the host/port directly targets a database or not.
    db: bool,
}

/// The length of the device located, including the slashes. This can target either a
/// device or a device attribute, or be a simple alias without slashes. Both device
/// name and alias have max length of 255 if we don't count the slashes.
/// 
/// From RFC 4/Attribute, maximum attr name length is 255.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
enum TrlObjectMeta {
    Alias(NonZero<u8>),
    Dev(NonZero<u8>),
    Attr(NonZero<u8>, NonZero<u8>),
}

impl TrlMeta {

    fn parse(raw: &str) -> Result<Self, TrlError> {

        let mut rem = raw;
        let mut object_offset = 0u16;

        // Check protocol
        let mut protocol = false;
        if let Some((proto, new_rem)) = rem.split_once("://") {
            if proto != "tango" {
                return Err(TrlError::InvalidProtocol);
            }
            object_offset += "tango://".len() as u16;
            protocol = true;
            rem = new_rem;
        }

        // Parse the end hash first.
        let mut db = true;
        if let Some((new_rem, hash)) = rem.rsplit_once('#') {
            db = match hash {
                "dbase=yes" => true,
                "dbase=no" => false,
                _ => return Err(TrlError::InvalidHash),
            };
            rem = new_rem;
        }

        // Then parse the property, we don't validate the property immediately because 
        // acceptable characters depend on whether this is device property or attr property.
        let mut property_len = None;
        if let Some((new_rem, property_raw)) = rem.rsplit_once("->") {
            if !check_tango_property_name(property_raw) {
                return Err(TrlError::InvalidPropName);
            }
            property_len = Some(NonZero::new(property_raw.len() as u8).unwrap());
            rem = new_rem;
        }

        // Only 4 parts at most, construct an array on stack.
        let mut parts = [""; 5];
        let mut parts_count = 0;
        for part in rem.split('/') {
            // If there are more parts it's not normal!
            if parts_count >= parts.len() {
                return Err(TrlError::InvalidPath);
            }
            parts[parts_count] = part;
            parts_count += 1;
        }

        
        // Get a slice with the real number of parts.
        let mut parts = &mut parts[..parts_count];
        debug_assert!(!parts.is_empty(), "A split we should have at least one element");

        // Try to find host:port in the first part if possible.
        let mut host_len_and_port = None;
        if let Some((host_raw, port_raw)) = parts[0].split_once(':') {

            // Remove the host:port part from the parts, check if there are still parts.
            parts = &mut parts[1..];
            if parts.is_empty() {
                return Err(TrlError::InvalidPath)
            }

            let host_len = u8::try_from(host_raw.len()).ok()
                .and_then(NonZero::new)
                .ok_or(TrlError::InvalidHost)?;

            if !host_raw.chars().enumerate().all(is_hostname_char) {
                return Err(TrlError::InvalidHost);
            }

            let port = port_raw.parse::<NonZero<u16>>()
                .map_err(|_| TrlError::InvalidPort)?;

            host_len_and_port = Some((host_len, port));

            // +1 for ':', +1 for '/'
            object_offset += host_raw.len() as u16 + 1 + port_raw.len() as u16 + 1;

        }

        // If this is an alias, it can be of length 255.
        let object;
        if parts.len() == 1 {
            if !check_tango_alias(parts[0]) {
                return Err(TrlError::InvalidAlias);
            }
            object = TrlObjectMeta::Alias(NonZero::new(parts[0].len() as u8).unwrap());
        } else if parts.len() == 3 || parts.len() == 4 {

            let mut dev_len_raw = 0; // Add the 2 slashes to len.
            for &dev_part in &parts[..3] {
                if !check_tango_dev_part_name(dev_part) {
                    return Err(TrlError::InvalidDevName);
                }
                dev_len_raw += dev_part.len();
            }

            // Unwrap because we check every part to not be empty.
            let dev_len = NonZero::new(dev_len_raw as u8).unwrap();

            if let Some(&attr_raw) = parts.get(3) {
                if !check_tango_attr_name(attr_raw) {
                    return Err(TrlError::InvalidAttrName);
                }
                object = TrlObjectMeta::Attr(dev_len, NonZero::new(attr_raw.len() as u8).unwrap());
            } else {
                object = TrlObjectMeta::Dev(dev_len);
            }

        } else {
            return Err(TrlError::InvalidPath);
        }

        Ok(Self {
            host_len_and_port,
            object_index: object_offset,
            object,
            property_len,
            protocol,
            db,
        })

    }

}

impl<'a> Trl<'a> {

    /// Parse a TRL, borrowing the given string.
    pub fn parse(raw: &'a str) -> Result<Self, TrlError> {
        Ok(Self { raw, meta: TrlMeta::parse(raw)? })
    }

    /// Return the raw string for this TRL.
    #[inline]
    pub fn as_str(self) -> &'a str {
        self.raw
    }

    /// Copy the raw string into an owned TRL, without parsing it again.
    #[inline]
    pub fn to_arc(self) -> ArcTrl {
        ArcTrl { raw: Arc::from(self.raw), meta: self.meta }
    }

    #[inline]
    fn host_and_port_index(self) -> usize {
        if self.meta.protocol { "tango://".len() } else { 0 }
    }

    /// The host and port of this TRL, if it has any.
    pub fn host_and_port(self) -> Option<(&'a str, u16)> {
        let index = self.host_and_port_index();
        self.meta.host_len_and_port.map(|(host_len, port)| {
            (&self.raw[index..][..host_len.get() as usize], port.get())
        })
    }

    #[inline]
    fn object_index(self) -> usize {
        self.meta.object_index as usize
    }

    /// The object this TRL locates: an alias, a device or a device attribute.
    pub fn object(self) -> TrlObject<'a> {
        let index = self.object_index();
        match self.meta.object {
            TrlObjectMeta::Alias(alias_len) => {
                TrlObject::Alias(&self.raw[index..][..alias_len.get() as usize])
            }
            TrlObjectMeta::Dev(dev_len) => {
                // +2 for slashes that were ignored in length.
                TrlObject::Dev(&self.raw[index..][..dev_len.get() as usize + 2])
            }
            TrlObjectMeta::Attr(dev_len, attr_len) => {
                // +2 for slashes that were ignored in length.
                let (dev_name, raw) = self.raw[index..].split_at(dev_len.get() as usize + 2);
                // Start at 1 to ignore the slash between device and attribute.
                let attr_name = &raw[1..][..attr_len.get() as usize];
                TrlObject::Attr(dev_name, attr_name)
            }
        }
    }

    #[inline]
    fn property_index(self) -> usize {
        self.object_index() + match self.meta.object {
            TrlObjectMeta::Alias(alias_len) => 
                alias_len.get() as usize,
            TrlObjectMeta::Dev(dev_len) => 
                dev_len.get() as usize + 2,
            TrlObjectMeta::Attr(dev_len, attr_len) => 
                dev_len.get() as usize + attr_len.get() as usize + 3,
        } + 2  // +2 for the "->"
    }

    /// The name of the property this TRL locates on its object, if any.
    pub fn property(self) -> Option<&'a str> {
        let index = self.property_index();
        self.meta.property_len.map(|len| {
            &self.raw[index..][..len.get() as usize]
        })
    }

    /// Whether the object is reached through a database, which `#dbase=no` turns off.
    #[inline]
    pub fn db(self) -> bool {
        self.meta.db
    }

}

impl ArcTrl {

    /// Borrow this TRL.
    #[inline]
    pub fn as_trl(&self) -> Trl<'_> {
        Trl { raw: &self.raw, meta: self.meta }
    }

    /// Return the raw string for this TRL.
    #[inline]
    pub fn as_str(&self) -> &str {
        &self.raw
    }

}

impl FromStr for ArcTrl {

    type Err = TrlError;

    fn from_str(raw: &str) -> Result<Self, Self::Err> {
        Ok(Self { raw: Arc::from(raw), meta: TrlMeta::parse(raw)? })
    }

}

impl From<Trl<'_>> for ArcTrl {
    #[inline]
    fn from(trl: Trl<'_>) -> Self {
        trl.to_arc()
    }
}

impl<'a> From<&'a ArcTrl> for Trl<'a> {
    #[inline]
    fn from(trl: &'a ArcTrl) -> Self {
        trl.as_trl()
    }
}

impl fmt::Debug for Trl<'_> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_tuple("Trl").field(&self.raw).finish()
    }
}

impl fmt::Display for Trl<'_> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(self.raw)
    }
}

impl fmt::Debug for ArcTrl {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_tuple("ArcTrl").field(&&*self.raw).finish()
    }
}

impl fmt::Display for ArcTrl {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(&self.raw)
    }
}

/// The object pointed to by a Tango Resource Locator.
pub enum TrlObject<'a> {
    /// An alias for a device or attribute.
    Alias(&'a str),
    /// A device name.
    Dev(&'a str),
    /// An attribute name with its device name.
    Attr(&'a str, &'a str),
}

/// From the RFC.
fn is_hostname_char((i, c): (usize, char)) -> bool {
    c.is_ascii_alphanumeric() || (i != 0 && (c == '-' || c == '.'))
}

/// From the RFC. 
/// 
/// With added:
/// - Dash as non first char '-'
/// - Digits as first char
fn is_tango_name_char((i, c): (usize, char)) -> bool {
    c.is_ascii_alphanumeric() || (i != 0 && (c == '_' || c == '-'))
}

/// Something that can be parsed into, or borrowed as, a [`Trl`].
pub trait IntoTrl<'a> {
    /// Get this as a TRL, failing if it is not a valid one.
    fn into_trl(self) -> Result<Trl<'a>, TrlError>;
}

impl<'a> IntoTrl<'a> for Trl<'a> {
    fn into_trl(self) -> Result<Trl<'a>, TrlError> {
        Ok(self)
    }
}

impl<'a> IntoTrl<'a> for &'a ArcTrl {
    fn into_trl(self) -> Result<Trl<'a>, TrlError> {
        Ok(self.as_trl())
    }
}

impl<'a> IntoTrl<'a> for &'a str {
    fn into_trl(self) -> Result<Trl<'a>, TrlError> {
        Trl::parse(self)
    }
}


#[cfg(test)]
mod tests {

    use super::*;
    use std::num::NonZero;
    use std::collections::HashSet;

    #[test]
    fn name_ignores_case() {

        assert_eq!(Name::new("Sys/TG_Test/1"), Name::new("sys/tg_test/1"));
        assert_ne!(Name::new("sys/tg_test/1"), Name::new("sys/tg_test/2"));
        assert_ne!(Name::new("attr"), Name::new("attr_2"));

        let names = HashSet::from([ArcName::from("Double_Scalar")]);
        assert!(names.contains(Name::new("double_scalar")));
        assert!(!names.contains(Name::new("double_scalar_w")));

    }

    #[test]
    fn name_keeps_case() {

        let name = Name::new("Double_Scalar");
        assert_eq!(name.as_str(), "Double_Scalar");
        assert_eq!(name.to_string(), "Double_Scalar");

        let arc_name = name.to_arc();
        assert_eq!(arc_name.as_str(), "Double_Scalar");
        assert_eq!(arc_name.to_string(), "Double_Scalar");
        assert_eq!("double_scalar".parse::<ArcName>().unwrap(), arc_name);

    }

    /// Letters, digits, `_` and `-` only, the latter two never first.
    #[test]
    fn name_chars() {
        assert!(check_tango_class_name("Motor_2-a"));
        assert!(check_tango_class_name("2Motor"));
        assert!(!check_tango_class_name(""));
        assert!(!check_tango_class_name("_Motor"));
        assert!(!check_tango_class_name("-Motor"));
        assert!(!check_tango_class_name("Mo tor"));
        assert!(!check_tango_class_name("Mo.tor"));
        assert!(!check_tango_class_name("Mo/tor"));
        assert!(!check_tango_class_name("Motör"));
    }

    /// At most 255 long for attributes, commands, properties and aliases, unbounded for
    /// classes.
    #[test]
    fn name_length() {
        let (max, over) = ("a".repeat(255), "a".repeat(256));
        assert!(check_tango_attr_name(&max) && !check_tango_attr_name(&over));
        assert!(check_tango_command_name(&max) && !check_tango_command_name(&over));
        assert!(check_tango_property_name(&max) && !check_tango_property_name(&over));
        assert!(check_tango_alias(&max) && !check_tango_alias(&over));
        assert!(check_tango_class_name(&over));
    }

    /// Exactly three parts, each a name at most 85 long.
    #[test]
    fn dev_name() {
        assert!(check_tango_dev_name("sys/tg_test/1"));
        assert!(check_tango_dev_name(&format!("{0}/{0}/{0}", "a".repeat(85))));
        assert!(!check_tango_dev_name(&format!("a/a/{}", "a".repeat(86))));
        assert!(!check_tango_dev_name("sys/tg_test"));
        assert!(!check_tango_dev_name("sys/tg_test/1/2"));
        assert!(!check_tango_dev_name("sys//1"));
        assert!(!check_tango_dev_name("sys/tg_test/_1"));
    }

    /// Exactly two parts, each a name.
    #[test]
    fn server_name() {
        assert!(check_tango_server_name("TangoTest/test"));
        assert!(!check_tango_server_name("TangoTest"));
        assert!(!check_tango_server_name("TangoTest/"));
        assert!(!check_tango_server_name("TangoTest/te/st"));
        assert!(!check_tango_server_name("TangoTest/te st"));
    }

    #[test]
    fn parse_and_get() {

        #[derive(Debug, Clone, Copy, PartialEq, Eq)]
        enum TrlObjectKind {
            Alias,
            Dev,
            Attr,
        }

        for protocol in [false, true] {
            for host_and_port in [false, true] {
                for object in [TrlObjectKind::Alias, TrlObjectKind::Dev, TrlObjectKind::Attr] {
                    for property in [false, true] {
                        for db in [None, Some(false), Some(true)] {
                        
                            let mut buf = String::new();
                            
                            if protocol {
                                buf.push_str("tango://");
                            }

                            if host_and_port {
                                buf.push_str("example.com:10000/");
                            }

                            let object_index = buf.len() as u16;
                            match object {
                                TrlObjectKind::Alias => buf.push_str("alias"),
                                TrlObjectKind::Dev => buf.push_str("domain/family/member"),
                                TrlObjectKind::Attr => buf.push_str("domain/family/member/attribute"),
                            }

                            if property {
                                buf.push_str("->property");
                            }

                            match db {
                                Some(false) => buf.push_str("#dbase=no"),
                                Some(true) => buf.push_str("#dbase=yes"),
                                None => (),
                            }

                            let trl = Trl::parse(&buf).unwrap();

                            assert_eq!(trl.meta.protocol, protocol);
                            assert_eq!(trl.meta.host_len_and_port, host_and_port.then_some((NonZero::new(11u8).unwrap(), NonZero::new(10000u16).unwrap())));
                            assert_eq!(trl.meta.object_index, object_index);
                            assert_eq!(trl.meta.object, match object {
                                TrlObjectKind::Alias => TrlObjectMeta::Alias(NonZero::new(5u8).unwrap()),
                                TrlObjectKind::Dev => TrlObjectMeta::Dev(NonZero::new(18u8).unwrap()),
                                TrlObjectKind::Attr => TrlObjectMeta::Attr(NonZero::new(18u8).unwrap(), NonZero::new(9u8).unwrap()),
                            });
                            assert_eq!(trl.meta.property_len, property.then_some(NonZero::new(8u8).unwrap()));
                            assert_eq!(trl.meta.db, db.unwrap_or(true));

                        }
                    }
                }
            }
        }

    }

}