rstango 0.4.0

//! Proxy to database devices.

use std::ops::{Deref, DerefMut};
use std::future::Future;
use std::borrow::Cow;
use std::fmt::Debug;
use std::sync::Arc;

use crate::dev::{All, DevProxy, Named, NamedResult, ProxyTarget, ToNames, ToNamesNotAll, unexpected_len_err};
use crate::error::{Error, ErrorKind, Result, reason};
use crate::backend::{default_backend, Backend};
use crate::prop::{FromProp, IntoProp};
use crate::value::{Scalar, Spectrum};


/// Proxy to a database with easy abstraction for commands that request devices.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
#[repr(transparent)]
pub struct DatabaseProxy {
    dev: DevProxy,
}

impl DatabaseProxy {

    // -- Constructors --

    /// New handle to the environment database.
    pub fn new_from_env() -> Self {
        Self::new_from_env_with_backend(default_backend())
    }

    /// New handle to specific host/port.
    pub fn new(host: &str, port: u16) -> Self {
        Self::new_with_backend(default_backend(), host, port)
    }

    /// New handle to the environment database, with backend.
    pub fn new_from_env_with_backend(backend: Arc<dyn Backend>) -> Self {
        Self {
            dev: DevProxy::new_from_target_with_backend(backend, ProxyTarget::DatabaseFromEnv),
        }
    }

    /// New handle to specific host/port, with backend.
    pub fn new_with_backend(backend: Arc<dyn Backend>, host: &str, port: u16) -> Self {
        Self {
            dev: DevProxy::new_from_target_with_backend(backend, ProxyTarget::DatabaseAt { 
                host: Arc::from(host), 
                port,
            }),
        }
    }

    /// Internal function to reinterpret a device proxy reference as a database proxy.
    pub(crate) fn from_dev(dev: &DevProxy) -> &DatabaseProxy {
        // SAFETY: DatabaseProxy is transparent over DevProxy
        unsafe { &*(dev as *const _ as *const DatabaseProxy) }
    }

    /// Internal function to manually create a database proxy by assuming that the given
    /// device proxy is such device.
    pub(crate) fn with_dev(dev: DevProxy) -> Self {
        Self {
            dev,
        }
    }

    /// The host and port this database is reached at, connecting it if that has not
    /// happened yet, which is the one of `TANGO_HOST` that answered when it is taken from
    /// the environment.
    pub(crate) async fn host_and_port_async(&self) -> Result<(Arc<str>, u16)> {
        let host_and_port = self.dev.database_host_and_port_async().await?;
        Ok(host_and_port.expect("This should be defined if the target is a database"))
    }

    // -- Info --

    /// Get the description of the database server and of what it holds, line by line.
    #[doc(alias = "DbInfo")]
    pub async fn database_info_async(&self) -> Result<Spectrum<str>> {
        self.command_async("DbInfo", ()).await
    }

    /// The blocking form of [`Self::database_info_async`].
    #[doc(alias = "DbInfo")]
    pub fn database_info(&self) -> Result<Spectrum<str>> {
        self.block_on(self.database_info_async())?
    }

    // -- Dev Add/Delete --

    /// Define a device of the given class in a server, named `exe/inst`.
    #[doc(alias = "DbAddDevice")]
    pub async fn add_dev_async(&self, name: &str, class: &str, server: &str) -> Result<()> {
        self.command_async("DbAddDevice", [server, name, class]).await
    }

    /// The blocking form of [`Self::add_dev_async`].
    #[doc(alias = "DbAddDevice")]
    pub fn add_dev(&self, name: &str, class: &str, server: &str) -> Result<()> {
        self.block_on(self.add_dev_async(name, class, server))?
    }

    /// Delete a device.
    #[doc(alias = "DbDeleteDevice")]
    pub async fn delete_dev_async(&self, name: &str) -> Result<()> {
        self.command_async("DbDeleteDevice", name).await
    }

    /// The blocking form of [`Self::delete_dev_async`].
    #[doc(alias = "DbDeleteDevice")]
    pub fn delete_dev(&self, name: &str) -> Result<()> {
        self.block_on(self.delete_dev_async(name))?
    }

    // -- Server --

    /// Define a server, named `exe/inst`, along with its devices, each given with its class,
    /// a device already defined in another server being moved to this one.
    #[doc(alias = "DbAddServer")]
    pub async fn add_server_async(&self, server: &str, devs: &[(&str, &str)]) -> Result<()> {
        let mut args = Vec::with_capacity(1 + devs.len() * 2);
        args.push(server);
        args.extend(devs.iter().flat_map(|&(name, class)| [name, class]));
        self.command_async("DbAddServer", &args[..]).await
    }

    /// The blocking form of [`Self::add_server_async`].
    #[doc(alias = "DbAddServer")]
    pub fn add_server(&self, server: &str, devs: &[(&str, &str)]) -> Result<()> {
        self.block_on(self.add_server_async(server, devs))?
    }

    /// Delete a server, named `exe/inst`, along with every device of it.
    #[doc(alias = "DbDeleteServer")]
    pub async fn delete_server_async(&self, server: &str) -> Result<()> {
        self.command_async("DbDeleteServer", server).await
    }

    /// The blocking form of [`Self::delete_server_async`].
    #[doc(alias = "DbDeleteServer")]
    pub fn delete_server(&self, server: &str) -> Result<()> {
        self.block_on(self.delete_server_async(server))?
    }

    /// Rename a server, named `exe/inst`, its devices following it.
    #[doc(alias = "DbRenameServer")]
    pub async fn rename_server_async(&self, name: &str, new_name: &str) -> Result<()> {
        self.command_async("DbRenameServer", [name, new_name]).await
    }

    /// The blocking form of [`Self::rename_server_async`].
    #[doc(alias = "DbRenameServer")]
    pub fn rename_server(&self, name: &str, new_name: &str) -> Result<()> {
        self.block_on(self.rename_server_async(name, new_name))?
    }

    /// List the devices a server, named `exe/inst`, should run, the class each device is an
    /// instance of being named by that device. This is what a server queries when booting
    /// in order to know which devices to create and export.
    #[doc(alias = "DbGetDeviceClassList")]
    pub async fn list_server_dev_async(&self, server: &str) -> Result<Vec<Named<Scalar<str>>>> {

        let flat: Spectrum<str> = self.command_async("DbGetDeviceClassList", server).await?;

        let mut pairs = Vec::with_capacity(flat.len() / 2);
        let mut index = 0;

        while let Some(dev_name) = flat.get_scalar([index]) {
            let Some(class_name) = flat.get_scalar([index + 1]) else {
                return Err(Error::new(ErrorKind::InvalidData)
                    .with_description(format!("Database answered device {:?} of server {server:?} without its class", dev_name.value()))
                    .with_append_description("Expected: a string spectrum of device/class pairs"));
            };
            pairs.push(Named::new(dev_name, class_name));
            index += 2;
        }

        Ok(pairs)

    }

    /// The blocking form of [`Self::list_server_dev_async`].
    #[doc(alias = "DbGetDeviceClassList")]
    pub fn list_server_dev(&self, server: &str) -> Result<Vec<Named<Scalar<str>>>> {
        self.block_on(self.list_server_dev_async(server))?
    }

    // -- Dev List --

    /// List all existing devices, filtering using a filter, using a pattern for 
    /// matching with domain/family/member pattern, supporting one '*' per member.
    #[doc(alias = "DbGetDeviceWideList")]
    pub async fn list_dev_async(&self, filter: &str) -> Result<Spectrum<str>> {
        self.command_async("DbGetDeviceWideList", filter).await
    }

    /// The blocking form of [`Self::list_dev_async`].
    #[doc(alias = "DbGetDeviceWideList")]
    pub fn list_dev(&self, filter: &str) -> Result<Spectrum<str>> {
        self.block_on(self.list_dev_async(filter))?
    }

    /// Same as [`Self::list_dev`] but returns only the member part of the
    /// device names (in domain/family/member).
    #[doc(alias = "DbGetDeviceMemberList")]
    pub async fn list_dev_member_async(&self, filter: &str) -> Result<Spectrum<str>> {
        self.command_async("DbGetDeviceMemberList", filter).await
    }

    /// The blocking form of [`Self::list_dev_member_async`].
    #[doc(alias = "DbGetDeviceMemberList")]
    pub fn list_dev_member(&self, filter: &str) -> Result<Spectrum<str>> {
        self.block_on(self.list_dev_member_async(filter))?
    }

    /// Same as [`Self::list_dev`] but returns only the family part of the
    /// device names (in domain/family/member).
    #[doc(alias = "DbGetDeviceFamilyList")]
    pub async fn list_dev_family_async(&self, filter: &str) -> Result<Spectrum<str>> {
        self.command_async("DbGetDeviceFamilyList", filter).await
    }

    /// The blocking form of [`Self::list_dev_family_async`].
    #[doc(alias = "DbGetDeviceFamilyList")]
    pub fn list_dev_family(&self, filter: &str) -> Result<Spectrum<str>> {
        self.block_on(self.list_dev_family_async(filter))?
    }

    /// Same as [`Self::list_dev`] but returns only the domain part of the
    /// device names (in domain/family/member).
    #[doc(alias = "DbGetDeviceDomainList")]
    pub async fn list_dev_domain_async(&self, filter: &str) -> Result<Spectrum<str>> {
        self.command_async("DbGetDeviceDomainList", filter).await
    }

    /// The blocking form of [`Self::list_dev_domain_async`].
    #[doc(alias = "DbGetDeviceDomainList")]
    pub fn list_dev_domain(&self, filter: &str) -> Result<Spectrum<str>> {
        self.block_on(self.list_dev_domain_async(filter))?
    }

    // -- Export --

    /// Mark a device as exported, recording how to reach it.
    #[doc(alias = "DbExportDevice")]
    pub async fn export_dev_async(&self, info: ExportDevInfo<'_>) -> Result<()> {
        self.command_async("DbExportDevice", data_from_export_dev_info(&[info][..])).await
    }

    /// The blocking form of [`Self::export_dev_async`].
    #[doc(alias = "DbExportDevice")]
    pub fn export_dev(&self, info: ExportDevInfo<'_>) -> Result<()> {
        self.block_on(self.export_dev_async(info))?
    }

    /// Mark a device as no longer exported.
    #[doc(alias = "DbUnExportDevice")]
    pub async fn unexport_dev_async(&self, dev_name: &str) -> Result<()> {
        self.command_async("DbUnExportDevice", dev_name).await
    }

    /// The blocking form of [`Self::unexport_dev_async`].
    #[doc(alias = "DbUnExportDevice")]
    pub fn unexport_dev(&self, dev_name: &str) -> Result<()> {
        self.block_on(self.unexport_dev_async(dev_name))?
    }

    /// Mark the devices of a server as exported, see [`Self::export_dev_async`].
    #[doc(alias = "DbExportServer")]
    pub async fn export_server_async(&self, infos: &[ExportDevInfo<'_>]) -> Result<()> {
        self.command_async("DbExportServer", data_from_export_dev_info(infos)).await
    }

    /// The blocking form of [`Self::export_server_async`].
    #[doc(alias = "DbExportServer")]
    pub fn export_server(&self, infos: &[ExportDevInfo<'_>]) -> Result<()> {
        self.block_on(self.export_server_async(infos))?
    }

    /// Mark every device of a server, named `exe/inst`, as no longer exported.
    #[doc(alias = "DbUnExportServer")]
    pub async fn unexport_server_async(&self, server: &str) -> Result<()> {
        self.command_async("DbUnExportServer", server).await
    }

    /// The blocking form of [`Self::unexport_server_async`].
    #[doc(alias = "DbUnExportServer")]
    pub fn unexport_server(&self, server: &str) -> Result<()> {
        self.block_on(self.unexport_server_async(server))?
    }

    /// Same input as [`Self::list_dev`], but returns only devices that should
    /// currently be exported.
    #[doc(alias = "DbGetDeviceExportedList")]
    pub async fn list_exported_dev_async(&self, filter: &str) -> Result<Spectrum<str>> {
        self.command_async("DbGetDeviceExportedList", filter).await
    }

    /// The blocking form of [`Self::list_exported_dev_async`].
    #[doc(alias = "DbGetDeviceExportedList")]
    pub fn list_exported_dev(&self, filter: &str) -> Result<Spectrum<str>> {
        self.block_on(self.list_exported_dev_async(filter))?
    }

    // -- Import --

    /// Get how to reach a device, failing with [`ErrorKind::DevNotFound`] if not defined.
    #[doc(alias = "DbImportDevice")]
    pub async fn import_dev_async(&self, dev_name: &str) -> Result<ImportDevInfo> {

        let (
            [exported, pid],
            svalue,
        ) = match self.command_async("DbImportDevice", dev_name).await.and_then(long2_string) {
            Ok(ret) => ret,
            Err(err) => {
                if let ErrorKind::Reason(reason::DB_DeviceNotDefined) = err.kind() {
                    return Err(Error::new(ErrorKind::DevNotFound)
                        .with_description(format!("Device {dev_name:?} is not defined in the database"))
                        .with_parent(err));
                } else {
                    return Err(err);
                }
            }
        };

        if svalue.len() != 5 && svalue.len() != 6 {
            return Err(Error::new(ErrorKind::InvalidData)
                .with_description(format!("Database answered {} strings for device {dev_name:?} where 5 or 6 were expected", svalue.len()))
                .with_append_description(format_args!("Got: {svalue:?}")));
        }

        // Each within the length just checked.
        let field = |index| svalue.get_scalar([index]).unwrap();

        Ok(ImportDevInfo {
            name: field(0),
            itr: field(1),
            host: field(4),
            version: field(2),
            server: field(3),
            class: svalue.get_scalar([5]),
            exported: exported == 1,
            pid,
        })

    }

    /// The blocking form of [`Self::import_dev_async`].
    #[doc(alias = "DbImportDevice")]
    pub fn import_dev(&self, dev_name: &str) -> Result<ImportDevInfo> {
        self.block_on(self.import_dev_async(dev_name))?
    }

    // -- Dev Info --

    /// Get what the database knows of a device, failing with [`ErrorKind::DevNotFound`] if
    /// not defined.
    #[doc(alias = "DbGetDeviceInfo")]
    pub async fn get_dev_info_async(&self, dev_name: &str) -> Result<DbDevInfo> {
        
        let (
            [exported, pid],
            svalue,
        ) = match self.command_async("DbGetDeviceInfo", dev_name).await.and_then(long2_string) {
            Ok(ret) => ret,
            Err(err) => {
                if let ErrorKind::Reason(reason::DB_DeviceNotDefined) = err.kind() {
                    return Err(Error::new(ErrorKind::DevNotFound)
                        .with_description(format!("Device {dev_name:?} is not defined in the database"))
                        .with_parent(err));
                } else {
                    return Err(err);
                }
            }
        };

        if svalue.len() != 7 && svalue.len() != 8 {
            return Err(Error::new(ErrorKind::InvalidData)
                .with_description(format!("Database answered {} strings for device {dev_name:?} where 7 or 8 were expected", svalue.len()))
                .with_append_description(format_args!("Got: {svalue:?}")));
        }

        // Each within the length just checked.
        let field = |index| svalue.get_scalar([index]).unwrap();

        Ok(DbDevInfo {
            name: field(0),
            itr: field(1),
            host: Some(field(4)).filter(|host| host.value() != "nada"),
            version: field(2),
            server: field(3),
            class: svalue.get_scalar([7]),
            last_exported: Some(field(5)).filter(|time| time.value() != "?"),
            last_unexported: Some(field(6)).filter(|time| time.value() != "?"),
            exported: exported == 1,
            pid: Some(pid).filter(|&pid| pid != 0),
        })

    }

    /// The blocking form of [`Self::get_dev_info_async`].
    #[doc(alias = "DbGetDeviceInfo")]
    pub fn get_dev_info(&self, dev_name: &str) -> Result<DbDevInfo> {
        self.block_on(self.get_dev_info_async(dev_name))?
    }
    
    // -- Dev Alias --

    /// Get alias for a given device.
    #[doc(alias = "DbGetDeviceAlias")]
    pub async fn get_dev_alias_async(&self, dev_name: &str) -> Result<Option<Scalar<str>>> {
        match self.command_async::<_, Scalar<str>>("DbGetDeviceAlias", dev_name).await {
            Ok(ret) => Ok(Some(ret)),
            Err(err) => {
                if let ErrorKind::Reason(reason::DB_AliasNotDefined) = err.kind() {
                    Ok(None)
                } else {
                    Err(err)
                }
            }
        }
    }

    /// The blocking form of [`Self::get_dev_alias_async`].
    #[doc(alias = "DbGetDeviceAlias")]
    pub fn get_dev_alias(&self, dev_name: &str) -> Result<Option<Scalar<str>>> {
        self.block_on(self.get_dev_alias_async(dev_name))?
    }

    /// Resolve a device alias, failing with [`ErrorKind::AliasNotFound`] if not found.
    #[doc(alias = "DbGetAliasDevice")]
    pub async fn resolve_dev_alias_async(&self, alias: &str) -> Result<Scalar<str>> {
        match self.command_async("DbGetAliasDevice", alias).await {
            Ok(ret) => Ok(ret),
            Err(err) => {
                if let ErrorKind::Reason(reason::DB_AliasNotDefined) = err.kind() {
                    Err(Error::new(ErrorKind::AliasNotFound)
                        .with_description(format!("Device alias {alias:?} is not defined in the database"))
                        .with_parent(err))
                } else {
                    Err(err)
                }
            }
        }
    }

    /// The blocking form of [`Self::resolve_dev_alias_async`].
    #[doc(alias = "DbGetAliasDevice")]
    pub fn resolve_dev_alias(&self, alias: &str) -> Result<Scalar<str>> {
        self.block_on(self.resolve_dev_alias_async(alias))?
    }

    /// List all device aliases matching the given filter (using at most one '*').
    #[doc(alias = "DbGetDeviceAliasList")]
    pub async fn list_dev_aliases_async(&self, filter: &str) -> Result<Spectrum<str>> {
        self.command_async("DbGetDeviceAliasList", filter).await
    }

    /// The blocking form of [`Self::list_dev_aliases_async`].
    #[doc(alias = "DbGetDeviceAliasList")]
    pub fn list_dev_aliases(&self, filter: &str) -> Result<Spectrum<str>> {
        self.block_on(self.list_dev_aliases_async(filter))?
    }

    // -- Attr Alias --

    /// Get alias for a given attribute.
    #[doc(alias = "DbGetAttributeAlias")]
    pub async fn get_attr_alias_async(&self, attr_name: &str) -> Result<Option<Scalar<str>>> {
        match self.command_async::<_, Scalar<str>>("DbGetAttributeAlias", attr_name).await {
            Ok(ret) => Ok(Some(ret)),
            Err(err) => {
                if let ErrorKind::Reason(reason::DB_AliasNotDefined) = err.kind() {
                    Ok(None)
                } else {
                    Err(err)
                }
            }
        }
    }

    /// The blocking form of [`Self::get_attr_alias_async`].
    #[doc(alias = "DbGetAttributeAlias")]
    pub fn get_attr_alias(&self, attr_name: &str) -> Result<Option<Scalar<str>>> {
        self.block_on(self.get_attr_alias_async(attr_name))?
    }

    /// Resolve an attribute alias, failing with [`ErrorKind::AliasNotFound`] if not found.
    #[doc(alias = "DbGetAliasAttribute")]
    pub async fn resolve_attr_alias_async(&self, alias: &str) -> Result<Scalar<str>> {
        match self.command_async("DbGetAliasAttribute", alias).await {
            Ok(ret) => Ok(ret),
            Err(err) => {
                if let ErrorKind::Reason(reason::DB_AliasNotDefined) = err.kind() {
                    Err(Error::new(ErrorKind::AliasNotFound)
                        .with_description(format!("Attribute alias {alias:?} is not defined in the database"))
                        .with_parent(err))
                } else {
                    Err(err)
                }
            }
        }
    }

    /// The blocking form of [`Self::resolve_attr_alias_async`].
    #[doc(alias = "DbGetAliasAttribute")]
    pub fn resolve_attr_alias(&self, alias: &str) -> Result<Scalar<str>> {
        self.block_on(self.resolve_attr_alias_async(alias))?
    }

    /// List all attribute aliases matching the given filter (using at most one '*').
    #[doc(alias = "DbGetAttributeAliasList")]
    pub async fn list_attr_aliases_async(&self, filter: &str) -> Result<Spectrum<str>> {
        self.command_async("DbGetAttributeAliasList", filter).await
    }

    /// The blocking form of [`Self::list_attr_aliases_async`].
    #[doc(alias = "DbGetAttributeAliasList")]
    pub fn list_attr_aliases(&self, filter: &str) -> Result<Spectrum<str>> {
        self.block_on(self.list_attr_aliases_async(filter))?
    }

    // -- Free Prop List --

    /// List the names of the free properties of an object matching the given filter.
    #[doc(alias = "DbGetPropertyList")]
    pub async fn list_free_prop_async(&self, obj_name: &str, filter: &str) -> Result<Spectrum<str>> {
        self.command_async("DbGetPropertyList", [obj_name, filter]).await
    }

    /// The blocking form of [`Self::list_free_prop_async`].
    #[doc(alias = "DbGetPropertyList")]
    pub fn list_free_prop(&self, obj_name: &str, filter: &str) -> Result<Spectrum<str>> {
        self.block_on(self.list_free_prop_async(obj_name, filter))?
    }

    // -- Class Prop List --

    /// List the names of the properties of a class matching the given filter.
    #[doc(alias = "DbGetClassPropertyList")]
    #[doc(alias = "DbGetClassPropertyListWildcard")]
    pub async fn list_class_prop_async(&self, obj_name: &str, filter: &str) -> Result<Spectrum<str>> {
        if filter == "*" {
            self.command_async("DbGetClassPropertyList", [obj_name]).await
        } else {
            self.command_async("DbGetClassPropertyListWildcard", [obj_name, filter]).await
        }
    }

    /// The blocking form of [`Self::list_class_prop_async`].
    #[doc(alias = "DbGetClassPropertyList")]
    #[doc(alias = "DbGetClassPropertyListWildcard")]
    pub fn list_class_prop(&self, obj_name: &str, filter: &str) -> Result<Spectrum<str>> {
        self.block_on(self.list_class_prop_async(obj_name, filter))?
    }

    // -- Dev Prop List --

    /// List the names of the properties of a device matching the given filter.
    #[doc(alias = "DbGetDevicePropertyList")]
    pub async fn list_dev_prop_async(&self, obj_name: &str, filter: &str) -> Result<Spectrum<str>> {
        self.command_async("DbGetDevicePropertyList", [obj_name, filter]).await
    }

    /// The blocking form of [`Self::list_dev_prop_async`].
    #[doc(alias = "DbGetDevicePropertyList")]
    pub fn list_dev_prop(&self, obj_name: &str, filter: &str) -> Result<Spectrum<str>> {
        self.block_on(self.list_dev_prop_async(obj_name, filter))?
    }

    // -- Common Prop Get --

    /// The reply to a read of the properties of that object, which is what every property
    /// read comes down to, see [`PropCommands`]: the parameters are the object and the
    /// names of the properties, see [`prop_params`], or absent for every property it has.
    ///
    /// The names are what the answer is checked against once it comes back, so the reply
    /// keeps them, sharing the parameters they were sent in.
    pub(crate) async fn get_raw_prop_async(&self,
        commands: PropCommands,
        obj_name: &str,
        params: Option<Spectrum<str>>,
    ) -> Result<get_prop::PropReply> {

        let params = match params {
            Some(params) => params,
            None => {
                let list_params = [obj_name, "*"];
                let list_params = if commands.list_wildcard { &list_params[..] } else { &list_params[0..1] };
                let names: Spectrum<str> = self.command_async(commands.list, list_params).await?;
                prop_params(obj_name, names.iter())
            }
        };

        let names = params.slice(1..);

        // The database rejects a request carrying no property name at all, answering that
        // it needs at least the object and one property, so it is simply not sent: there is
        // nothing to report, which is what an object having no property at all gives, the
        // property list command having then answered with an empty list.
        if names.is_empty() {
            return Ok(get_prop::PropReply::empty());
        }

        let listing: Spectrum<str> = self.command_async(commands.get, params).await?;
        get_prop::PropReply::new(obj_name, listing, names)

    }

    /// Read properties of that object, parsed into the shape the given names ask for.
    fn get_any_prop_async<Spec, Names: ToNames>(&self,
        commands: PropCommands,
        obj_name: &str,
        names: Names,
    ) -> impl Future<Output = Result<Spec::Output>> + Send
    where
        Spec: GetPropSpec<Names>,
    {
        let params = names.iter_names().map(|names| prop_params(obj_name, names));
        async move {
            let mut reply = self.get_raw_prop_async(commands, obj_name, params).await?;
            Spec::collect(&mut reply)
        }
    }

    // -- Free Prop Get --

    /// The properties of that free object, parsed into the shape the given names ask for,
    /// see [`Self::get_dev_prop_async`] for the accepted signatures.
    #[doc(alias = "DbGetProperty")]
    pub fn get_free_prop_async<Spec, Names: ToNames>(&self, obj_name: &str, names: Names) -> impl Future<Output = Result<Spec::Output>> + Send
    where
        Spec: GetPropSpec<Names>,
    {
        self.get_any_prop_async::<Spec, Names>(PropCommands::FREE, obj_name, names)
    }

    /// The properties of that free object, see [`Self::get_free_prop_async`].
    #[doc(alias = "DbGetProperty")]
    pub fn get_free_prop<Spec, Names: ToNames>(&self, obj_name: &str, names: Names) -> Result<Spec::Output>
    where
        Spec: GetPropSpec<Names>,
    {
        self.block_on(self.get_free_prop_async::<Spec, Names>(obj_name, names))?
    }

    // -- Class Prop Get --

    /// The properties of that class, parsed into the shape the given names ask for, see
    /// [`Self::get_dev_prop_async`] for the accepted signatures.
    #[doc(alias = "DbGetClassProperty")]
    pub fn get_class_prop_async<Spec, Names: ToNames>(&self, class_name: &str, names: Names) -> impl Future<Output = Result<Spec::Output>> + Send
    where
        Spec: GetPropSpec<Names>,
    {
        self.get_any_prop_async::<Spec, Names>(PropCommands::CLASS, class_name, names)
    }

    /// The properties of that class, see [`Self::get_class_prop_async`].
    #[doc(alias = "DbGetClassProperty")]
    pub fn get_class_prop<Spec, Names: ToNames>(&self, class_name: &str, names: Names) -> Result<Spec::Output>
    where
        Spec: GetPropSpec<Names>,
    {
        self.block_on(self.get_class_prop_async::<Spec, Names>(class_name, names))?
    }

    // -- Dev Prop Get --

    /// The properties of that device, parsed into the shape the given names ask for. This
    /// specification is really flexible and allows various signatures for the function:
    /// 1. `get_dev_prop<T>(&str, &str) -> Result<T>`
    /// 2. `get_dev_prop<T>(&str, &[&str]) -> Result<Vec<Result<T>>>`
    /// 3. `get_dev_prop<T>(&str, [&str; N]) -> Result<[Result<T>; N]>`
    /// 4. `get_dev_prop<(A, B, ...)>(&str, (&str, &str, ...)) -> Result<(Result<A>, Result<B>, ...)>`
    /// 5. `get_dev_prop<Spectrum<str>>(&str, All) -> Result<Vec<Named<Spectrum<str>>>>`
    ///
    /// Form 2 also takes the names as a [`Spectrum<str>`], owned or borrowed. Every value
    /// is parsed with [`FromProp`]: a [`String`], a [`Vec<String>`], a [`Spectrum<str>`]
    /// sharing the reply, a [`bool`] or a number. Like for [`DevProxy::read_attr`], the
    /// type has to come from a turbofish, as in `get_dev_prop::<f64, _>(dev, "speed")`,
    /// or from the binding the output is assigned to.
    ///
    /// A property the database holds nothing for has no value, which the text forms read
    /// as empty and the others fail with [`ErrorKind::InvalidProp`]. Form 5 gives every
    /// property the device has, each with its name, as the raw values it holds.
    ///
    /// All the properties are read within a single request. Note that, unlike the
    /// many-properties forms, form 1 has no per-property slot in its output and therefore
    /// returns that property's error directly.
    #[doc(alias = "DbGetDeviceProperty")]
    pub fn get_dev_prop_async<Spec, Names: ToNames>(&self, dev_name: &str, names: Names) -> impl Future<Output = Result<Spec::Output>> + Send
    where
        Spec: GetPropSpec<Names>,
    {
        self.get_any_prop_async::<Spec, Names>(PropCommands::DEV, dev_name, names)
    }

    /// The properties of that device, see [`Self::get_dev_prop_async`].
    #[doc(alias = "DbGetDeviceProperty")]
    pub fn get_dev_prop<Spec, Names: ToNames>(&self, dev_name: &str, names: Names) -> Result<Spec::Output>
    where
        Spec: GetPropSpec<Names>,
    {
        self.block_on(self.get_dev_prop_async::<Spec, Names>(dev_name, names))?
    }

    // -- Common Prop Command --

    /// Send a property command with those parameters, which every property write and
    /// deletion comes down to, see [`prop_params`].
    pub(crate) async fn prop_command_async(&self, cmd_name: &'static str, params: Spectrum<str>) -> Result<()> {
        self.command_async(cmd_name, params).await
    }

    // -- Free Prop Set --

    /// Write the given properties of that free object, see [`Self::set_dev_prop_async`]
    /// for the accepted signatures.
    #[doc(alias = "DbPutProperty")]
    pub fn set_free_prop_async<'a, Spec>(&self, obj_name: &'a str, spec: Spec) -> impl Future<Output = Result<()>> + Send
    where
        Spec: SetPropSpec<'a>,
    {
        self.prop_command_async("DbPutProperty", prop_params(obj_name, set_prop_params(spec).iter().map(|param| &**param)))
    }

    /// Write the given properties of that free object, see [`Self::set_free_prop_async`].
    #[doc(alias = "DbPutProperty")]
    pub fn set_free_prop<'a, Spec>(&self, obj_name: &'a str, spec: Spec) -> Result<()>
    where
        Spec: SetPropSpec<'a>,
    {
        self.block_on(self.set_free_prop_async(obj_name, spec))?
    }

    // -- Class Prop Set --

    /// Write the given properties of that class, see [`Self::set_dev_prop_async`] for the
    /// accepted signatures.
    #[doc(alias = "DbPutClassProperty")]
    pub fn set_class_prop_async<'a, Spec>(&self, class_name: &'a str, spec: Spec) -> impl Future<Output = Result<()>> + Send
    where
        Spec: SetPropSpec<'a>,
    {
        self.prop_command_async("DbPutClassProperty", prop_params(class_name, set_prop_params(spec).iter().map(|param| &**param)))
    }

    /// Write the given properties of that class, see [`Self::set_class_prop_async`].
    #[doc(alias = "DbPutClassProperty")]
    pub fn set_class_prop<'a, Spec>(&self, class_name: &'a str, spec: Spec) -> Result<()>
    where
        Spec: SetPropSpec<'a>,
    {
        self.block_on(self.set_class_prop_async(class_name, spec))?
    }

    // -- Dev Prop Set --

    /// Write the given properties of that device, given as pairs of a name and a value.
    /// Like for [`Self::get_dev_prop`], this specification is really flexible and allows
    /// various signatures for the function:
    /// 1. `set_dev_prop(&str, (&str, T)) -> Result<()>`
    /// 2. `set_dev_prop(&str, [(&str, T); N]) -> Result<()>`
    /// 3. `set_dev_prop(&str, Vec<(&str, T)>) -> Result<()>`
    /// 4. `set_dev_prop(&str, ((&str, A), (&str, B), ...)) -> Result<()>`
    ///
    /// Each value only needs to implement [`IntoProp`], a [`bool`], a number or a string,
    /// so the value types are inferred from the specification and never have to be named,
    /// form 4 giving each property its own type, as in
    /// `set_dev_prop(dev, (("speed", 2.5), ("unit", "mm")))`.
    ///
    /// All the properties are written within a single request, a property that was
    /// already there being overwritten.
    #[doc(alias = "DbPutDeviceProperty")]
    pub fn set_dev_prop_async<'a, Spec>(&self, dev_name: &'a str, spec: Spec) -> impl Future<Output = Result<()>> + Send
    where
        Spec: SetPropSpec<'a>,
    {
        self.prop_command_async("DbPutDeviceProperty", prop_params(dev_name, set_prop_params(spec).iter().map(|param| &**param)))
    }

    /// Write the given properties of that device, see [`Self::set_dev_prop_async`].
    #[doc(alias = "DbPutDeviceProperty")]
    pub fn set_dev_prop<'a, Spec>(&self, dev_name: &'a str, spec: Spec) -> Result<()>
    where
        Spec: SetPropSpec<'a>,
    {
        self.block_on(self.set_dev_prop_async(dev_name, spec))?
    }

    // -- Free Prop Del --

    /// Delete the given properties of that free object, see [`Self::delete_dev_prop_async`]
    /// for the accepted signatures.
    #[doc(alias = "DbDeleteProperty")]
    pub fn delete_free_prop_async<Names: ToNamesNotAll>(&self, obj_name: &str, names: Names) -> impl Future<Output = Result<()>> + Send {
        self.prop_command_async("DbDeleteProperty", prop_params(obj_name, names.iter_names_not_all()))
    }

    /// Delete the given properties of that free object, see [`Self::delete_free_prop_async`].
    #[doc(alias = "DbDeleteProperty")]
    pub fn delete_free_prop<Names: ToNamesNotAll>(&self, obj_name: &str, names: Names) -> Result<()> {
        self.block_on(self.delete_free_prop_async(obj_name, names))?
    }

    // -- Class Prop Del --

    /// Delete the given properties of that class, see [`Self::delete_dev_prop_async`] for the
    /// accepted signatures.
    #[doc(alias = "DbDeleteClassProperty")]
    pub fn delete_class_prop_async<Names: ToNamesNotAll>(&self, class_name: &str, names: Names) -> impl Future<Output = Result<()>> + Send {
        self.prop_command_async("DbDeleteClassProperty", prop_params(class_name, names.iter_names_not_all()))
    }

    /// Delete the given properties of that class, see [`Self::delete_class_prop_async`].
    #[doc(alias = "DbDeleteClassProperty")]
    pub fn delete_class_prop<Names: ToNamesNotAll>(&self, class_name: &str, names: Names) -> Result<()> {
        self.block_on(self.delete_class_prop_async(class_name, names))?
    }

    // -- Dev Prop Del --

    /// Delete the given properties of that device, which allows various signatures for the
    /// function:
    /// 1. `delete_dev_prop(&str, &str) -> Result<()>`
    /// 2. `delete_dev_prop(&str, &[&str]) -> Result<()>`
    /// 3. `delete_dev_prop(&str, [&str; N]) -> Result<()>`
    /// 4. `delete_dev_prop(&str, (&str, &str, ...)) -> Result<()>`
    ///
    /// Form 2 also takes the names as a [`Spectrum<str>`], owned or borrowed. Every name
    /// has to be given, [`All`] not being accepted, and deleting a property the database
    /// holds nothing for is not an error.
    #[doc(alias = "DbDeleteDeviceProperty")]
    pub fn delete_dev_prop_async<Names: ToNamesNotAll>(&self, dev_name: &str, names: Names) -> impl Future<Output = Result<()>> + Send {
        self.prop_command_async("DbDeleteDeviceProperty", prop_params(dev_name, names.iter_names_not_all()))
    }

    /// Delete the given properties of that device, see [`Self::delete_dev_prop_async`].
    #[doc(alias = "DbDeleteDeviceProperty")]
    pub fn delete_dev_prop<Names: ToNamesNotAll>(&self, dev_name: &str, names: Names) -> Result<()> {
        self.block_on(self.delete_dev_prop_async(dev_name, names))?
    }

    // -- Common Attr Prop Get --

    /// The reply to a read of the properties of attributes of that object, which is what
    /// every attribute property read comes down to, see [`AttrPropCommands`]: the parameters
    /// are the object and the names of the attributes, see [`prop_params`], or absent for
    /// every attribute that has any property, and the properties are those of the given
    /// names of every attribute, or absent for every property each one has.
    ///
    /// The database answers with every property it holds of each attribute, there being no
    /// asking it for some of them only, so the properties asked for are looked up in what it
    /// answered, and one it does not hold is given with no value, see
    /// [`get_prop::PropReply::Attr`].
    pub(crate) async fn get_raw_attr_prop_async(&self,
        commands: AttrPropCommands,
        obj_name: &str,
        params: Option<Spectrum<str>>,
        prop_names: Option<Spectrum<str>>,
    ) -> Result<get_prop::AttrPropReply> {

        let params = match params {
            Some(params) => params,
            None => {
                let attr_names: Spectrum<str> = self.command_async(commands.list, [obj_name, "*"]).await?;
                prop_params(obj_name, attr_names.iter())
            }
        };

        // The names the answer is checked against, sharing the parameters.
        let attr_names = params.slice(1..);

        // A request carrying no attribute at all is not worth sending, there being nothing
        // it could answer with.
        if attr_names.is_empty() {
            return Ok(get_prop::AttrPropReply::empty());
        }

        let listing: Spectrum<str> = self.command_async(commands.get, params).await?;
        get_prop::AttrPropReply::new(obj_name, listing, attr_names, prop_names)

    }

    /// Read the properties of attributes of that object, parsed into the shape the names of
    /// the attributes and the names of the properties ask for, see [`GetAttrPropSpec`].
    fn get_any_attr_prop_async<Spec, AttrNames, Names>(&self,
        commands: AttrPropCommands,
        obj_name: &str,
        attr_names: AttrNames,
        prop_names: Names,
    ) -> impl Future<Output = Result<Spec::Output>> + Send
    where
        Spec: GetAttrPropSpec<AttrNames, Names>,
        AttrNames: ToNames,
        Names: ToNames,
    {
        let params = attr_names.iter_names().map(|attr_names| prop_params(obj_name, attr_names));
        let prop_names = prop_names.to_names();
        async move {
            let mut reply = self.get_raw_attr_prop_async(commands, obj_name, params, prop_names).await?;
            Spec::collect(&mut reply)
        }
    }

    // -- Class Attr Prop Get --

    /// The properties of the given attributes of that class, parsed into the shape the names
    /// of the attributes and of the properties ask for, see [`Self::get_dev_attr_prop_async`]
    /// for the accepted signatures.
    #[doc(alias = "DbGetClassAttributeProperty2")]
    pub fn get_class_attr_prop_async<Spec, AttrNames, Names>(&self, class_name: &str, attr_names: AttrNames, prop_names: Names) -> impl Future<Output = Result<Spec::Output>> + Send
    where
        Spec: GetAttrPropSpec<AttrNames, Names>,
        AttrNames: ToNames,
        Names: ToNames,
    {
        self.get_any_attr_prop_async::<Spec, AttrNames, Names>(AttrPropCommands::CLASS, class_name, attr_names, prop_names)
    }

    /// The properties of the given attributes of that class, see
    /// [`Self::get_class_attr_prop_async`].
    #[doc(alias = "DbGetClassAttributeProperty2")]
    pub fn get_class_attr_prop<Spec, AttrNames, Names>(&self, class_name: &str, attr_names: AttrNames, prop_names: Names) -> Result<Spec::Output>
    where
        Spec: GetAttrPropSpec<AttrNames, Names>,
        AttrNames: ToNames,
        Names: ToNames,
    {
        self.block_on(self.get_class_attr_prop_async::<Spec, AttrNames, Names>(class_name, attr_names, prop_names))?
    }

    // -- Dev Attr Prop Get --

    /// The properties of the given attributes of that device, or of every attribute of it
    /// that has any, parsed into the shape the names of the attributes and of the properties
    /// ask for. The names of the properties are given the way they are to
    /// [`Self::get_dev_prop`], and give the same output for every attribute, written `P`
    /// below, which the names of the attributes then shape in the same way:
    /// 1. `get_dev_attr_prop<T>(&str, &str, Names) -> Result<P>`
    /// 2. `get_dev_attr_prop<T>(&str, &[&str], Names) -> Result<Vec<Result<P>>>`
    /// 3. `get_dev_attr_prop<T>(&str, [&str; N], Names) -> Result<[Result<P>; N]>`
    /// 4. `get_dev_attr_prop<T>(&str, (&str, &str, ...), Names) -> Result<(Result<P>, Result<P>, ...)>`
    /// 5. `get_dev_attr_prop<T>(&str, All, Names) -> Result<Vec<NamedResult<P>>>`
    ///
    /// Form 2 also takes the names as a [`Spectrum<str>`], owned or borrowed, and form 5
    /// gives every attribute the device holds any property for, each with its name. For
    /// instance:
    /// - `get_dev_attr_prop::<String, _, _>(dev, "Position", "unit") -> Result<String>`
    /// - `get_dev_attr_prop::<String, _, _>(dev, ["Position", "Speed"], "unit") -> Result<[Result<String>; 2]>`
    /// - `get_dev_attr_prop::<(String, f64), _, _>(dev, "Position", ("label", "__value")) -> Result<(Result<String>, Result<f64>)>`
    /// - `get_dev_attr_prop::<Spectrum<str>, _, _>(dev, All, All) -> Result<Vec<NamedResult<Vec<Named<Spectrum<str>>>>>>`
    ///
    /// All the attributes are read within a single request. Note that form 1 has no
    /// per-attribute slot in its output and therefore returns that attribute's error
    /// directly, the same way form 1 of the properties does.
    #[doc(alias = "DbGetDeviceAttributeProperty2")]
    pub fn get_dev_attr_prop_async<Spec, AttrNames, Names>(&self, dev_name: &str, attr_names: AttrNames, prop_names: Names) -> impl Future<Output = Result<Spec::Output>> + Send
    where
        Spec: GetAttrPropSpec<AttrNames, Names>,
        AttrNames: ToNames,
        Names: ToNames,
    {
        self.get_any_attr_prop_async::<Spec, AttrNames, Names>(AttrPropCommands::DEV, dev_name, attr_names, prop_names)
    }

    /// The properties of the given attributes of that device, see
    /// [`Self::get_dev_attr_prop_async`].
    #[doc(alias = "DbGetDeviceAttributeProperty2")]
    pub fn get_dev_attr_prop<Spec, AttrNames, Names>(&self, dev_name: &str, attr_names: AttrNames, prop_names: Names) -> Result<Spec::Output>
    where
        Spec: GetAttrPropSpec<AttrNames, Names>,
        AttrNames: ToNames,
        Names: ToNames,
    {
        self.block_on(self.get_dev_attr_prop_async::<Spec, AttrNames, Names>(dev_name, attr_names, prop_names))?
    }

    // -- Class Attr Prop Set --

    /// Write the given properties of attributes of that class, see
    /// [`Self::set_dev_attr_prop_async`] for the accepted signatures.
    #[doc(alias = "DbPutClassAttributeProperty2")]
    pub fn set_class_attr_prop_async<'a, Spec>(&self, class_name: &'a str, spec: Spec) -> impl Future<Output = Result<()>> + Send
    where
        Spec: SetAttrPropSpec<'a>,
    {
        self.prop_command_async("DbPutClassAttributeProperty2", attr_prop_params(class_name, spec))
    }

    /// Write the given properties of attributes of that class, see
    /// [`Self::set_class_attr_prop_async`].
    #[doc(alias = "DbPutClassAttributeProperty2")]
    pub fn set_class_attr_prop<'a, Spec>(&self, class_name: &'a str, spec: Spec) -> Result<()>
    where
        Spec: SetAttrPropSpec<'a>,
    {
        self.block_on(self.set_class_attr_prop_async(class_name, spec))?
    }

    // -- Dev Attr Prop Set --

    /// Write the given properties of attributes of that device, each attribute given as a
    /// pair of its name and of its properties, the latter in any of the forms
    /// [`Self::set_dev_prop`] accepts, written `S` below:
    /// 1. `set_dev_attr_prop(&str, (&str, S)) -> Result<()>`
    /// 2. `set_dev_attr_prop(&str, [(&str, S); N]) -> Result<()>`
    /// 3. `set_dev_attr_prop(&str, Vec<(&str, S)>) -> Result<()>`
    ///
    /// Forms 2 and 3 give every attribute the same form of properties. For instance:
    /// - `set_dev_attr_prop(dev, ("Position", ("unit", "mm")))`
    /// - `set_dev_attr_prop(dev, ("Position", (("unit", "mm"), ("min_value", -5))))`
    /// - `set_dev_attr_prop(dev, [("Position", vec![("label", "Pos")]), ("Speed", vec![("rel_change", "1")])])`
    ///
    /// All the attributes are written within a single request.
    #[doc(alias = "DbPutDeviceAttributeProperty2")]
    pub fn set_dev_attr_prop_async<'a, Spec>(&self, dev_name: &'a str, spec: Spec) -> impl Future<Output = Result<()>> + Send
    where
        Spec: SetAttrPropSpec<'a>,
    {
        self.prop_command_async("DbPutDeviceAttributeProperty2", attr_prop_params(dev_name, spec))
    }

    /// Write the given properties of attributes of that device, see
    /// [`Self::set_dev_attr_prop_async`].
    #[doc(alias = "DbPutDeviceAttributeProperty2")]
    pub fn set_dev_attr_prop<'a, Spec>(&self, dev_name: &'a str, spec: Spec) -> Result<()>
    where
        Spec: SetAttrPropSpec<'a>,
    {
        self.block_on(self.set_dev_attr_prop_async(dev_name, spec))?
    }

    // -- Class Attr Prop Del --

    /// Delete the given properties of one attribute of that class, see
    /// [`Self::delete_dev_attr_prop_async`] for the accepted signatures.
    #[doc(alias = "DbDeleteClassAttributeProperty")]
    pub fn delete_class_attr_prop_async<Names: ToNamesNotAll>(&self, class_name: &str, attr_name: &str, names: Names) -> impl Future<Output = Result<()>> + Send {
        let params = prop_params(class_name, Some(attr_name).into_iter().chain(names.iter_names_not_all()));
        self.prop_command_async("DbDeleteClassAttributeProperty", params)
    }

    /// Delete the given properties of one attribute of that class, see
    /// [`Self::delete_class_attr_prop_async`].
    #[doc(alias = "DbDeleteClassAttributeProperty")]
    pub fn delete_class_attr_prop<Names: ToNamesNotAll>(&self, class_name: &str, attr_name: &str, names: Names) -> Result<()> {
        self.block_on(self.delete_class_attr_prop_async(class_name, attr_name, names))?
    }

    // -- Dev Attr Prop Del --

    /// Delete the given properties of one attribute of that device, the names of the
    /// properties being given the way they are to [`Self::delete_dev_prop`]:
    /// 1. `delete_dev_attr_prop(&str, &str, &str) -> Result<()>`
    /// 2. `delete_dev_attr_prop(&str, &str, &[&str]) -> Result<()>`
    /// 3. `delete_dev_attr_prop(&str, &str, [&str; N]) -> Result<()>`
    /// 4. `delete_dev_attr_prop(&str, &str, (&str, &str, ...)) -> Result<()>`
    ///
    /// Only one attribute is deleted from per request, the database having no command
    /// deleting from several at once.
    #[doc(alias = "DbDeleteDeviceAttributeProperty")]
    pub fn delete_dev_attr_prop_async<Names: ToNamesNotAll>(&self, dev_name: &str, attr_name: &str, names: Names) -> impl Future<Output = Result<()>> + Send {
        let params = prop_params(dev_name, Some(attr_name).into_iter().chain(names.iter_names_not_all()));
        self.prop_command_async("DbDeleteDeviceAttributeProperty", params)
    }

    /// Delete the given properties of one attribute of that device, see
    /// [`Self::delete_dev_attr_prop_async`].
    #[doc(alias = "DbDeleteDeviceAttributeProperty")]
    pub fn delete_dev_attr_prop<Names: ToNamesNotAll>(&self, dev_name: &str, attr_name: &str, names: Names) -> Result<()> {
        self.block_on(self.delete_dev_attr_prop_async(dev_name, attr_name, names))?
    }

}

impl Deref for DatabaseProxy {
    type Target = DevProxy;
    fn deref(&self) -> &Self::Target {
        &self.dev
    }
}

impl DerefMut for DatabaseProxy {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.dev
    }
}

// =========================== //
//    Device import/export     //
// =========================== //

/// The information required to export a device.
#[derive(Debug, Clone)]
pub struct ExportDevInfo<'a> {
    /// The name of the device.
    pub name: Cow<'a, str>,
    /// The Interoperable Tango Reference to reach the device.
    pub itr: Cow<'a, str>,
    /// The host the device is served on.
    pub host: Cow<'a, str>,
    /// The version of the protocol the device is served with.
    pub version: Cow<'a, str>,
    /// The Process ID of the device's server.
    pub pid: i32,
}

fn data_from_export_dev_info(infos: &[ExportDevInfo<'_>]) -> Spectrum<str> {

    let mut vec = Vec::with_capacity(infos.len() * 5);

    for info in infos {
        vec.push(Cow::Borrowed(&*info.name));
        vec.push(Cow::Borrowed(&*info.itr));
        vec.push(Cow::Borrowed(&*info.host));
        vec.push(Cow::Owned(format!("{}", info.pid)));
        vec.push(Cow::Borrowed(&*info.version));
    }

    Spectrum::from(&vec[..])

}

/// The two members of what the database answers about a device with, which are the
/// exported flag and the process ID, and then its strings.
fn long2_string((longs, strings): (Spectrum<i32>, Spectrum<str>)) -> Result<([i32; 2], Spectrum<str>)> {
    let longs = <[i32; 2]>::try_from(longs.as_slice())
        .map_err(|_| Error::new(ErrorKind::InvalidData)
            .with_description(format!("Database answered {} longs where 2 were expected", longs.len()))
            .with_append_description(format_args!("Got: {longs:?}")))?;
    Ok((longs, strings))
}

/// Information for how to import a device from the database.
#[derive(Debug, Clone)]
pub struct ImportDevInfo {
    /// The name of the device.
    pub name: Scalar<str>,
    /// The Interoperable Tango Reference to reach the device.
    pub itr: Scalar<str>,
    /// The device host.
    pub host: Scalar<str>,
    /// The device version.
    pub version: Scalar<str>,
    /// The device server.
    pub server: Scalar<str>,
    /// Class of this device.
    pub class: Option<Scalar<str>>,
    /// True if the device is currently exported by a server.
    pub exported: bool,
    /// The last known Process ID of the device's server.
    pub pid: i32,
}

/// What the database knows of a device, see [`DatabaseProxy::get_dev_info`].
#[derive(Debug, Clone)]
pub struct DbDevInfo {
    /// The name of the device.
    pub name: Scalar<str>,
    /// The Interoperable Tango Reference to reach the device.
    pub itr: Scalar<str>,
    /// The device host.
    pub host: Option<Scalar<str>>,
    /// The device version.
    pub version: Scalar<str>,
    /// The device server.
    pub server: Scalar<str>,
    /// Class of this device.
    pub class: Option<Scalar<str>>,
    /// When the device was last exported, as the database writes it, if it ever was.
    pub last_exported: Option<Scalar<str>>,    // TODO: Convert to chrono DateTime
    /// When the device was last unexported, as the database writes it, if it ever was.
    pub last_unexported: Option<Scalar<str>>,  // TODO: Convert to chrono DateTime
    /// True if the device is currently exported by a server.
    pub exported: bool,
    /// The last known Process ID of the device's server.
    pub pid: Option<i32>,
}

// =========================== //
//      Property requests      //
// =========================== //

// The property requests give back futures declared `Send`, which hold nothing of what they
// were given but what is taken out of it before anything is awaited: the names, and the
// values to write, so that they are `Send` whatever the names and the values are, which is
// what an asynchronous handler boxing them needs.

/// What a property write carries behind the object: how many properties, then each
/// property with how many values it has and those values, the names and the values staying
/// borrowed.
pub(crate) fn set_prop_params<'a, Spec: SetPropSpec<'a>>(spec: Spec) -> Vec<Cow<'a, str>> {
    let mut builder = set_prop::Builder::new();
    spec.push_to_builder(&mut builder);
    builder.finalize()
}

/// The parameters of a property command, the object first, copied together into the one
/// buffer the command is given.
pub(crate) fn prop_params<'a>(obj_name: &'a str, rest: impl Iterator<Item = &'a str>) -> Spectrum<str> {
    Spectrum::from_strs(Some(obj_name).into_iter().chain(rest)).expect("property parameters of more than 4 GiB")
}

// =========================== //
//       Get properties        //
// =========================== //

/// The commands reading the properties of one kind of object.
#[derive(Debug, Clone, Copy)]
pub(crate) struct PropCommands {
    /// The command reading properties by name.
    get: &'static str,
    /// The command listing the names of the properties.
    list: &'static str,
    /// Whether that listing command takes a filter, the class one taking none.
    list_wildcard: bool,
}

impl PropCommands {
    const FREE: Self = Self { get: "DbGetProperty", list: "DbGetPropertyList", list_wildcard: true };
    const CLASS: Self = Self { get: "DbGetClassProperty", list: "DbGetClassPropertyList", list_wildcard: false };
    pub(crate) const DEV: Self = Self { get: "DbGetDeviceProperty", list: "DbGetDevicePropertyList", list_wildcard: true };
}

/// Sealing module for the reply structure.
mod get_prop {

    use super::{Error, ErrorKind, Named, Result, Scalar, Spectrum};

    /// The properties the database answered a request with, one entry per property and in
    /// the order they were requested, taken one at a time, see [`super::GetPropSpec::collect`].
    ///
    /// Every name and every value shares the octets the answer was decoded out of, so nothing
    /// of them is copied before a caller parses them.
    #[derive(Debug)]
    pub enum PropReply {
        /// The properties of an object, still in the flat sequence of strings the database
        /// speaks in, read one at a time.
        Listing {
            /// The listing, empty when nothing was asked: a request carrying no property name
            /// at all is one the database refuses, so it is not sent, and an object that has no
            /// property gives exactly that.
            listing: Spectrum<str>,
            /// The names that were asked for, in the order they were, which the order of the
            /// answer is checked against.
            names: Spectrum<str>,
            /// Which property is taken next.
            index: usize,
            /// Where in the listing that property starts.
            cursor: usize,
        },
        /// The properties of one attribute, read out of the listing of an attribute property
        /// request, see [`AttrPropReply`].
        ///
        /// The database answers with every property it holds of an attribute, there being no
        /// asking it for some of them only, so the ones asked for are looked up among those
        /// ignoring the case, which is how Tango compares them, and one it does not hold is
        /// given with no value, which is what it answers for a property of an object.
        Attr {
            /// The listing of the whole request, every attribute in it.
            listing: Spectrum<str>,
            /// Where the first property of the attribute starts.
            begin: usize,
            /// How many properties the attribute has.
            count: usize,
            /// The names that were asked for, or none for every property the attribute has,
            /// in the order the database gave them.
            names: Option<Spectrum<str>>,
            /// Which property is taken next.
            index: usize,
            /// Where in the listing that property starts, when every one is taken.
            cursor: usize,
        },
    }

    impl PropReply {

        /// The reply to a request that asked for nothing, which is not sent: it carries no
        /// property and never looks at a listing.
        pub(super) fn empty() -> Self {
            Self::Listing { listing: Spectrum::new(), names: Spectrum::new(), index: 0, cursor: 0 }
        }

        /// The reply to a request for the properties of that object of the given names,
        /// answered with that listing, whose head is read here, see [`read_head`], so that
        /// what is left to take is the properties themselves.
        pub(super) fn new(obj_name: &str, listing: Spectrum<str>, names: Spectrum<str>) -> Result<Self> {
            let cursor = read_head(&listing, obj_name, names.len(), "property count", "properties")?;
            Ok(Self::Listing { listing, names, index: 0, cursor })
        }

        /// How many properties are left to be taken: what was asked for, minus what has already
        /// been taken.
        pub fn len(&self) -> usize {
            match self {
                Self::Listing { names, index, .. } => names.len() - index,
                Self::Attr { names: Some(names), index, .. } => names.len() - index,
                Self::Attr { names: None, count, index, .. } => count - index,
            }
        }

        /// Whether every property has been taken, or nothing was asked for at all.
        pub fn is_empty(&self) -> bool {
            self.len() == 0
        }

        /// Take the next property, which is its name as the database gave it back and the
        /// values it holds, both sharing the listing.
        ///
        /// A property carries a list of values and not one value: what a single value looks
        /// like is what [`crate::prop::FromProp`] makes of that list, an empty one being a property that is
        /// defined and holds nothing.
        ///
        /// A listing that does not add up ends the iteration rather than failing that one
        /// property: where a property starts is where the one before it ended, so nothing
        /// behind a broken one can be read either.
        pub fn next(&mut self) -> Option<Result<Named<Spectrum<str>>>> {

            let (listing, names, index, cursor) = match self {
                Self::Listing { listing, names, index, cursor } => (listing, names, index, cursor),
                Self::Attr { listing, begin, count, names, index, cursor } => {
                    return next_attr_prop(listing, *begin, *count, names.as_ref(), index, cursor);
                }
            };

            let expected = names.get([*index])?;
            *index += 1;

            match next_prop(listing, expected, cursor) {
                Ok(prop) => Some(Ok(prop)),
                Err(err) => {
                    *index = names.len();
                    Some(Err(err))
                }
            }

        }

    }

    /// Read one property out of the listing, starting at `cursor` and leaving it where the next
    /// property starts, see [`PropReply::next`].
    ///
    /// This is where the shape the database speaks in is read: a property is its name, how many
    /// values it holds, and then those values.
    fn next_prop(listing: &Spectrum<str>, expected: &str, cursor: &mut usize) -> Result<Named<Spectrum<str>>> {

        let (Some(name), Some(count_raw)) = (listing.get([*cursor]), listing.get([*cursor + 1])) else {
            return Err(Error::new(ErrorKind::InvalidData)
                .with_description(format!("Database answer is missing the name and values count of property {expected:?}"))
                .with_append_description(format_args!("Got: {listing:?}")));
        };

        if !name.eq_ignore_ascii_case(expected) {
            return Err(Error::new(ErrorKind::InvalidData)
                .with_description(format!("Database answered property {name:?} where {expected:?} was requested")));
        }

        let Ok(count) = count_raw.parse::<usize>() else {
            return Err(Error::new(ErrorKind::InvalidData)
                .with_description(format!("Database answered values count {count_raw:?} of property {name:?}, which is not a number")));
        };

        let name_index = *cursor;
        let begin = *cursor + 2;
        *cursor = begin + count;

        if *cursor > listing.len() {
            return Err(Error::new(ErrorKind::InvalidData)
                .with_description(format!("Database answer is missing values of property {name:?}"))
                .with_append_description(format_args!("Got: {listing:?}")));
        }

        let name = listing.slice(name_index..name_index + 1).into_scalar().expect("one name");
        Ok(Named::new(name, listing.slice(begin..*cursor)))

    }

    /// Take the next property of an attribute, see [`PropReply::Attr`]: the next one of the
    /// names asked for, looked up among every property of the attribute, or the next one the
    /// attribute has when none was asked for in particular.
    ///
    /// The properties of the attribute were walked once already, by [`AttrPropReply::next`],
    /// so that the next attribute could be found behind them, which a broken one fails.
    fn next_attr_prop(
        listing: &Spectrum<str>,
        begin: usize,
        count: usize,
        names: Option<&Spectrum<str>>,
        index: &mut usize,
        cursor: &mut usize,
    ) -> Option<Result<Named<Spectrum<str>>>> {

        let Some(names) = names else {
            if *index >= count {
                return None;
            }
            *index += 1;
            return Some(next_value_prop(listing, cursor));
        };

        let name = names.get_scalar([*index])?;
        *index += 1;

        let mut lookup = begin;
        for _ in 0..count {
            match next_value_prop(listing, &mut lookup) {
                Ok(prop) if prop.name.value().eq_ignore_ascii_case(name.value()) => {
                    return Some(Ok(prop));
                }
                Ok(_) => {}
                Err(err) => {
                    *index = names.len();
                    return Some(Err(err));
                }
            }
        }

        Some(Ok(Named::new(name, Spectrum::new())))

    }

    /// Read one property of an attribute out of the listing, starting at `cursor` and leaving
    /// it where the next property starts: its name, how many values it holds, and then those
    /// values, a property holding no value being followed by a single placeholder all the
    /// same, which is not one of its values.
    fn next_value_prop(listing: &Spectrum<str>, cursor: &mut usize) -> Result<Named<Spectrum<str>>> {

        let name = next_str(listing, cursor, "property name")?;
        let count = next_count(listing, cursor, "property values count")?;

        let begin = *cursor;
        *cursor += count.max(1);
        if *cursor > listing.len() {
            return Err(Error::new(ErrorKind::InvalidData)
                .with_description(format!("Database answer is missing values of property {:?}", name.value()))
                .with_append_description(format_args!("Got: {listing:?}")));
        }

        Ok(Named::new(name, listing.slice(begin..begin + count)))

    }

    /// The properties of attributes the database answered a request with, one entry per
    /// attribute and in the order they were requested, taken one at a time, each being the
    /// properties of that attribute, see [`PropReply::Attr`].
    ///
    /// The listing is the flat sequence of strings the database speaks in: every attribute is
    /// its name, how many properties it has, and then those properties.
    #[derive(Debug)]
    pub struct AttrPropReply {
        /// The listing, empty when nothing was asked.
        listing: Spectrum<str>,
        /// The names of the attributes that were asked for, in the order they were, which the
        /// order of the answer is checked against.
        attr_names: Spectrum<str>,
        /// The names of the properties asked for of every attribute, or none for every one.
        prop_names: Option<Spectrum<str>>,
        /// Which attribute is taken next.
        index: usize,
        /// Where in the listing that attribute starts.
        cursor: usize,
    }

    impl AttrPropReply {

        /// The reply to a request that asked for no attribute, which is not sent: it carries
        /// no attribute and never looks at a listing.
        pub(super) fn empty() -> Self {
            Self { listing: Spectrum::new(), attr_names: Spectrum::new(), prop_names: None, index: 0, cursor: 0 }
        }

        /// The reply to a request for the properties of the given names of the attributes of
        /// that object of the given names, answered with that listing, whose head is read
        /// here, see [`read_head`], so that what is left to take is the attributes themselves.
        pub(super) fn new(
            obj_name: &str,
            listing: Spectrum<str>,
            attr_names: Spectrum<str>,
            prop_names: Option<Spectrum<str>>,
        ) -> Result<Self> {
            let cursor = read_head(&listing, obj_name, attr_names.len(), "attribute count", "attributes")?;
            Ok(Self { listing, attr_names, prop_names, index: 0, cursor })
        }

        /// How many attributes are left to be taken.
        pub fn len(&self) -> usize {
            self.attr_names.len() - self.index
        }

        /// Take the next attribute, which is its name as the database gave it back and its
        /// properties.
        ///
        /// A listing that does not add up ends the iteration, an attribute starting where the
        /// one before it ended.
        pub fn next(&mut self) -> Option<Result<Named<PropReply>>> {

            let Self { listing, attr_names, prop_names, index, cursor } = self;

            let expected = attr_names.get([*index])?;
            *index += 1;

            let res = (|| {

                let name = next_str(listing, cursor, "attribute name")?;
                if !name.value().eq_ignore_ascii_case(expected) {
                    return Err(Error::new(ErrorKind::InvalidData)
                        .with_description(format!("Database answered attribute {:?} where {expected:?} was requested",
                            name.value())));
                }

                // The properties are walked here, so that the next attribute is found behind
                // them, and read again as they are taken.
                let count = next_count(listing, cursor, "property count")?;
                let begin = *cursor;
                for _ in 0..count {
                    next_value_prop(listing, cursor)?;
                }

                Ok(Named::new(name, PropReply::Attr {
                    listing: listing.clone(),
                    begin,
                    count,
                    names: prop_names.clone(),
                    index: 0,
                    cursor: begin,
                }))

            })();

            if res.is_err() {
                *index = attr_names.len();
            }

            Some(res)

        }

    }

    /// Read the head of a listing, which is the object it is of and how many entries follow,
    /// checked against what was asked for, giving back where the first entry starts.
    fn read_head(listing: &Spectrum<str>, obj_name: &str, expected: usize, what: &str, entries: &str) -> Result<usize> {

        let mut cursor = 0;

        let output_obj_name = next_str(listing, &mut cursor, "object name")?;
        if !output_obj_name.value().eq_ignore_ascii_case(obj_name) {
            return Err(Error::new(ErrorKind::InvalidData)
                .with_description(format!("Database answered for object {:?} where {obj_name:?} was requested",
                    output_obj_name.value())));
        }

        let count = next_count(listing, &mut cursor, what)?;
        if count != expected {
            return Err(Error::new(ErrorKind::InvalidData)
                .with_description(format!("Database answered {count} {entries} of object {obj_name:?} where {expected} were requested")));
        }

        Ok(cursor)

    }

    /// The string at the cursor of a listing, moving the cursor past it.
    fn next_str(listing: &Spectrum<str>, cursor: &mut usize, what: &str) -> Result<Scalar<str>> {
        let Some(value) = listing.get_scalar([*cursor]) else {
            return Err(Error::new(ErrorKind::InvalidData)
                .with_description(format!("Database answer is missing the {what}"))
                .with_append_description(format_args!("Got: {listing:?}")));
        };
        *cursor += 1;
        Ok(value)
    }

    /// The count at the cursor of a listing, moving the cursor past it, see [`next_str`].
    fn next_count(listing: &Spectrum<str>, cursor: &mut usize, what: &str) -> Result<usize> {
        let raw = next_str(listing, cursor, what)?;
        raw.value().trim().parse::<usize>().map_err(|_| Error::new(ErrorKind::InvalidData)
            .with_description(format!("Database answered {what} {:?}, which is not a number", raw.value())))
    }

}

/// A trait for property specifiers, which allows a great flexibility in how
/// [`DatabaseProxy::get_dev_prop`] works.
///
/// **Supporting trait**: it is only there to make this crate's API easier to use, it is
/// implemented for everything that API accepts and is not one to implement anywhere else.
pub trait GetPropSpec<Names> {

    /// Kind of output type returned.
    type Output;

    /// Build the output out of the properties, taking them one at a time.
    ///
    /// The shape of the output is what the names that were given say it is, and what every
    /// property is parsed into is what this is implemented on.
    fn collect(props: &mut get_prop::PropReply) -> Result<Self::Output>;

}

/// One name, one property: that property *is* the output, and its failure is the output's
/// own since there is no slot of its own to carry it in.
impl<T> GetPropSpec<&'_ str> for T
where
    T: FromProp,
{

    type Output = T;

    fn collect(props: &mut get_prop::PropReply) -> Result<Self::Output> {
        match props.next() {
            Some(entry) => T::from_prop(&entry?.value),
            None => Err(unexpected_len_err(1)),
        }
    }

}

impl<T> GetPropSpec<&'_ [&'_ str]> for T
where
    T: FromProp,
{

    type Output = Vec<Result<T>>;

    fn collect(props: &mut get_prop::PropReply) -> Result<Self::Output> {

        // How many properties there are is known before the first one is taken, so the room
        // for them is made once.
        let mut values = Vec::with_capacity(props.len());

        while let Some(entry) = props.next() {
            values.push(T::from_prop(&entry?.value));
        }

        Ok(values)

    }

}

impl<T> GetPropSpec<Spectrum<str>> for T
where
    T: FromProp,
{

    type Output = Vec<Result<T>>;

    fn collect(props: &mut get_prop::PropReply) -> Result<Self::Output> {
        <T as GetPropSpec<&[&str]>>::collect(props)
    }

}

impl<T> GetPropSpec<&Spectrum<str>> for T
where
    T: FromProp,
{

    type Output = Vec<Result<T>>;

    fn collect(props: &mut get_prop::PropReply) -> Result<Self::Output> {
        <T as GetPropSpec<&[&str]>>::collect(props)
    }

}

impl<T, const N: usize> GetPropSpec<[&'_ str; N]> for T
where
    T: FromProp,
{

    type Output = [Result<T>; N];

    fn collect(props: &mut get_prop::PropReply) -> Result<Self::Output> {

        // One property per slot, a last one behind them being a broken reply as much as one
        // of them missing, see [`crate::dev::take_array`].
        let mut slots = [const { None }; N];
        for slot in &mut slots {
            let entry = props.next().ok_or_else(|| unexpected_len_err(N))?;
            *slot = Some(T::from_prop(&entry?.value));
        }
        if props.next().is_some() {
            return Err(unexpected_len_err(N));
        }

        Ok(slots.map(|slot| slot.expect("every slot is filled")))

    }
    
}

impl GetPropSpec<All> for Spectrum<str> {

    type Output = Vec<Named<Spectrum<str>>>;

    fn collect(props: &mut get_prop::PropReply) -> Result<Self::Output> {

        // Nothing was named here, so every property carries its own name, both sharing the
        // listing they were read out of.
        let mut values = Vec::with_capacity(props.len());

        while let Some(entry) = props.next() {
            values.push(entry?);
        }

        Ok(values)

    }

}

macro_rules! impl_get_prop_spec_tuple {
    ( @one: $comp:ident ) => { 1 };
    ( @name: $comp:ident ) => { &'name str };
    ( $( $comp:ident )* ) => {

        #[allow(non_snake_case)]
        impl<'name, $($comp,)* > GetPropSpec<( $( impl_get_prop_spec_tuple!(@name: $comp), )* )> for ( $($comp,)* )
        where
            $(
            $comp: FromProp,
            )*
        {

            type Output = ( $( Result<$comp>,)* );

            fn collect(props: &mut get_prop::PropReply) -> Result<Self::Output> {

                const LEN: usize = 0 $( + impl_get_prop_spec_tuple!(@one: $comp) )*;

                // The properties are taken in the order the names were given, which is the
                // order the components of a tuple are built in, and every one of them is
                // parsed into the type of its own component.
                let output = ( $( {
                    let entry = props.next().ok_or_else(|| unexpected_len_err(LEN))?;
                    $comp::from_prop(&entry?.value)
                }, )* );
                if props.next().is_some() {
                    return Err(unexpected_len_err(LEN));
                }

                Ok(output)

            }

        }

    };
}

impl_get_prop_spec_tuple!(A);
impl_get_prop_spec_tuple!(A B);
impl_get_prop_spec_tuple!(A B C);
impl_get_prop_spec_tuple!(A B C D);
impl_get_prop_spec_tuple!(A B C D E);
impl_get_prop_spec_tuple!(A B C D E F);

// =========================== //
//       Set properties        //
// =========================== //

/// Sealing module for the Builder structure.
mod set_prop {

    use super::{Cow, IntoProp, SetPropSpec};

    pub struct Builder<'a> {
        array: Vec<Cow<'a, str>>,
        count: usize,
    }

    impl<'a> Builder<'a> {

        pub fn new() -> Self {
            Self {
                array: vec![Cow::Borrowed("")],  // Properties count is set when finalized.
                count: 0,
            }
        }

        pub fn push<T>(&mut self, name: &'a str, value: T)
        where
            T: IntoProp<'a>,
        {
            self.array.push(Cow::Borrowed(name));
            self.array.push(Cow::Borrowed(""));  // Will be written just after...
            let len = self.array.len();
            self.array.extend(value.into_prop());
            let count = self.array.len() - len;
            self.array[len - 1] = Cow::Owned(format!("{count}"));  // Actually write count!
            self.count += 1;
        }

        pub fn finalize(mut self) -> Vec<Cow<'a, str>> {
            // Write the number of properties ahead of the array.
            self.array[0] = Cow::Owned(format!("{}", self.count));
            self.array
        }

    }

    /// The counterpart of [`Builder`] for the properties of attributes: every attribute
    /// is its name followed by what a [`Builder`] makes of its properties.
    pub struct AttrBuilder<'a> {
        array: Vec<Cow<'a, str>>,
        count: usize,
    }

    impl<'a> AttrBuilder<'a> {

        pub fn new() -> Self {
            Self {
                array: vec![Cow::Borrowed("")],  // Attributes count is set when finalized.
                count: 0,
            }
        }

        pub fn push<S>(&mut self, attr_name: &'a str, spec: S)
        where
            S: SetPropSpec<'a>,
        {
            let mut builder = Builder::new();
            spec.push_to_builder(&mut builder);
            self.array.push(Cow::Borrowed(attr_name));
            self.array.extend(builder.finalize());
            self.count += 1;
        }

        pub fn finalize(mut self) -> Vec<Cow<'a, str>> {
            self.array[0] = Cow::Owned(format!("{}", self.count));
            self.array
        }

    }

}

/// The properties to write, as name/value pairs, see [`DatabaseProxy::set_dev_prop`].
///
/// **Supporting trait**: it is only there to make this crate's API easier to use, it is
/// implemented for everything that API accepts and is not one to implement anywhere else.
pub trait SetPropSpec<'a>: Sized {
    /// Make this write specification into the params for the set property command.
    fn push_to_builder(self, builder: &mut set_prop::Builder<'a>);
}

/// For a single property.
impl<'a, T> SetPropSpec<'a> for (&'a str, T)
where
    T: IntoProp<'a>,
{

    #[inline]
    fn push_to_builder(self, builder: &mut set_prop::Builder<'a>) {
        builder.push(self.0, self.1);
    }

}

/// For an array of properties.
impl<'a, T, const N: usize> SetPropSpec<'a> for [(&'a str, T); N]
where
    T: IntoProp<'a>,
{

    #[inline]
    fn push_to_builder(self, builder: &mut set_prop::Builder<'a>) {
        for (name, value) in self {
            builder.push(name, value);
        }
    }

}

/// For a vector of properties.
impl<'a, 'aa: 'a, T> SetPropSpec<'a> for Vec<(&'aa str, T)>
where
    T: IntoProp<'a>,
{

    #[inline]
    fn push_to_builder(self, builder: &mut set_prop::Builder<'a>) {
        for (name, value) in self {
            builder.push(name, value);
        }
    }

}

macro_rules! impl_set_prop_spec_tuple {
    ( @name: $comp:ident ) => { &'a str };
    ( $( $comp:ident )* ) => {

        #[allow(non_snake_case, unused_assignments)]
        impl<'a, $($comp,)*> SetPropSpec<'a> for ( $( (impl_set_prop_spec_tuple!(@name: $comp), $comp), )* )
        where
            $(
                $comp: IntoProp<'a>,
            )*
        {

            #[inline]
            fn push_to_builder(self, builder: &mut set_prop::Builder<'a>) {
                let ( $($comp,)* ) = self;
                $(
                    builder.push($comp.0, $comp.1);
                )*
            }

        }

    };
}

impl_set_prop_spec_tuple!(A);
impl_set_prop_spec_tuple!(A B);
impl_set_prop_spec_tuple!(A B C);
impl_set_prop_spec_tuple!(A B C D);
impl_set_prop_spec_tuple!(A B C D E);
impl_set_prop_spec_tuple!(A B C D E F);

// =========================== //
//  Get attribute properties   //
// =========================== //

/// The commands reading the properties of the attributes of one kind of object.
#[derive(Debug, Clone, Copy)]
pub(crate) struct AttrPropCommands {
    /// The command reading the properties of attributes by name.
    get: &'static str,
    /// The command listing the attributes that have any property.
    list: &'static str,
}

impl AttrPropCommands {
    pub(crate) const CLASS: Self = Self { get: "DbGetClassAttributeProperty2", list: "DbGetClassAttributeList" };
    pub(crate) const DEV: Self = Self { get: "DbGetDeviceAttributeProperty2", list: "DbGetDeviceAttributeList" };
}

/// A trait for attribute property specifiers, which allows a great flexibility in how
/// [`DatabaseProxy::get_dev_attr_prop`] works: the attributes are shaped by their names, the
/// way any request on names is, see [`crate::dev::ToNamesSpec`], and the properties of every
/// one of them by the names of the properties, see [`GetPropSpec`], which is what this is
/// implemented on.
///
/// **Supporting trait**: it is only there to make this crate's API easier to use, it is
/// implemented for everything that API accepts and is not one to implement anywhere else.
pub trait GetAttrPropSpec<AttrNames, Names> {

    /// Kind of output type returned.
    type Output;

    /// Build the output out of the attributes, taking them one at a time, and the properties
    /// of every one of them.
    fn collect(attrs: &mut get_prop::AttrPropReply) -> Result<Self::Output>;

}

/// The properties of the next attribute, parsed, the listing not adding up failing the
/// whole output, see [`get_prop::AttrPropReply::next`].
fn next_attr<T: GetPropSpec<Names>, Names>(attrs: &mut get_prop::AttrPropReply) -> Option<Result<NamedResult<T::Output>>> {
    Some(attrs.next()?.map(|attr| attr.map(|mut props| T::collect(&mut props))))
}

/// One attribute: its properties *are* the output, and their failure is the output's own
/// since there is no slot of its own to carry it in.
impl<T: GetPropSpec<Names>, Names> GetAttrPropSpec<&'_ str, Names> for T {

    type Output = T::Output;

    fn collect(attrs: &mut get_prop::AttrPropReply) -> Result<Self::Output> {
        match next_attr::<T, Names>(attrs) {
            Some(attr) => attr?.value,
            None => Err(unexpected_len_err(1)),
        }
    }

}

/// Every attribute of a list, each with the outcome of its own properties.
fn collect_attr_list<T: GetPropSpec<Names>, Names>(attrs: &mut get_prop::AttrPropReply) -> Result<Vec<Result<T::Output>>> {
    let mut outputs = Vec::with_capacity(attrs.len());
    while let Some(attr) = next_attr::<T, Names>(attrs) {
        outputs.push(attr?.value);
    }
    Ok(outputs)
}

impl<T: GetPropSpec<Names>, Names> GetAttrPropSpec<&'_ [&'_ str], Names> for T {
    type Output = Vec<Result<T::Output>>;
    fn collect(attrs: &mut get_prop::AttrPropReply) -> Result<Self::Output> {
        collect_attr_list::<T, Names>(attrs)
    }
}

impl<T: GetPropSpec<Names>, Names> GetAttrPropSpec<Spectrum<str>, Names> for T {
    type Output = Vec<Result<T::Output>>;
    fn collect(attrs: &mut get_prop::AttrPropReply) -> Result<Self::Output> {
        collect_attr_list::<T, Names>(attrs)
    }
}

impl<T: GetPropSpec<Names>, Names> GetAttrPropSpec<&'_ Spectrum<str>, Names> for T {
    type Output = Vec<Result<T::Output>>;
    fn collect(attrs: &mut get_prop::AttrPropReply) -> Result<Self::Output> {
        collect_attr_list::<T, Names>(attrs)
    }
}

impl<T: GetPropSpec<Names>, Names, const N: usize> GetAttrPropSpec<[&'_ str; N], Names> for T {

    type Output = [Result<T::Output>; N];

    fn collect(attrs: &mut get_prop::AttrPropReply) -> Result<Self::Output> {
        // One attribute per slot, a last one behind them being a broken reply as much as one
        // of them missing, see [`crate::dev::take_array`].
        let mut slots = [const { None }; N];
        for slot in &mut slots {
            *slot = Some(next_attr::<T, Names>(attrs).ok_or_else(|| unexpected_len_err(N))??.value);
        }
        if attrs.next().is_some() {
            return Err(unexpected_len_err(N));
        }
        Ok(slots.map(|slot| slot.expect("every slot is filled")))
    }

}

/// Nothing was named here, so every attribute carries its own name.
impl<T: GetPropSpec<Names>, Names> GetAttrPropSpec<All, Names> for T {

    type Output = Vec<NamedResult<T::Output>>;

    fn collect(attrs: &mut get_prop::AttrPropReply) -> Result<Self::Output> {
        let mut outputs = Vec::with_capacity(attrs.len());
        while let Some(attr) = next_attr::<T, Names>(attrs) {
            outputs.push(attr?);
        }
        Ok(outputs)
    }

}

macro_rules! impl_get_attr_prop_spec_tuple {
    ( @one: $index:tt ) => { 1 };
    ( @name: $index:tt ) => { &'name str };
    ( @output: $index:tt ) => { Result<T::Output> };
    ( @next: $index:tt, $attrs:ident ) => { next_attr::<T, Names>($attrs).ok_or_else(|| unexpected_len_err(LEN))??.value };
    ( $( $index:tt )* ) => {

        impl<'name, T: GetPropSpec<Names>, Names> GetAttrPropSpec<( $( impl_get_attr_prop_spec_tuple!(@name: $index), )* ), Names> for T {

            type Output = ( $( impl_get_attr_prop_spec_tuple!(@output: $index), )* );

            fn collect(attrs: &mut get_prop::AttrPropReply) -> Result<Self::Output> {
                const LEN: usize = 0 $( + impl_get_attr_prop_spec_tuple!(@one: $index) )*;
                // The attributes come in the order the names were given, which is the order
                // the components of a tuple are built in.
                let output = ( $( impl_get_attr_prop_spec_tuple!(@next: $index, attrs), )* );
                if attrs.next().is_some() {
                    return Err(unexpected_len_err(LEN));
                }
                Ok(output)
            }

        }

    };
}

impl_get_attr_prop_spec_tuple!(0);
impl_get_attr_prop_spec_tuple!(0 1);
impl_get_attr_prop_spec_tuple!(0 1 2);
impl_get_attr_prop_spec_tuple!(0 1 2 3);
impl_get_attr_prop_spec_tuple!(0 1 2 3 4);
impl_get_attr_prop_spec_tuple!(0 1 2 3 4 5);

// =========================== //
//  Set attribute properties   //
// =========================== //

/// An abstract specification of the properties to write of one to many attributes, every
/// attribute being given what [`SetPropSpec`] takes for the properties of an object, see
/// [`DatabaseProxy::set_dev_attr_prop`].
///
/// **Supporting trait**: it is only there to make this crate's API easier to use, it is
/// implemented for everything that API accepts and is not one to implement anywhere else.
pub trait SetAttrPropSpec<'a>: Sized {
    /// Make this write specification into the params for the set property command.
    fn push_to_builder(self, builder: &mut set_prop::AttrBuilder<'a>);
}

/// For the properties of a single attribute.
impl<'a, S> SetAttrPropSpec<'a> for (&'a str, S)
where
    S: SetPropSpec<'a>,
{

    #[inline]
    fn push_to_builder(self, builder: &mut set_prop::AttrBuilder<'a>) {
        builder.push(self.0, self.1);
    }

}

/// For an array of attributes.
impl<'a, S, const N: usize> SetAttrPropSpec<'a> for [(&'a str, S); N]
where
    S: SetPropSpec<'a>,
{

    #[inline]
    fn push_to_builder(self, builder: &mut set_prop::AttrBuilder<'a>) {
        for (attr_name, spec) in self {
            builder.push(attr_name, spec);
        }
    }

}

/// For a vector of attributes.
impl<'a, S> SetAttrPropSpec<'a> for Vec<(&'a str, S)>
where
    S: SetPropSpec<'a>,
{

    #[inline]
    fn push_to_builder(self, builder: &mut set_prop::AttrBuilder<'a>) {
        for (attr_name, spec) in self {
            builder.push(attr_name, spec);
        }
    }

}

/// The parameters of an attribute property write, the object first.
fn attr_prop_params<'a, Spec: SetAttrPropSpec<'a>>(obj_name: &str, spec: Spec) -> Spectrum<str> {
    let mut builder = set_prop::AttrBuilder::new();
    spec.push_to_builder(&mut builder);
    prop_params(obj_name, builder.finalize().iter().map(|param| &**param))
}

#[cfg(test)]
mod tests {

    use futures::future::BoxFuture;

    use super::*;

    /// The attribute property reads, awaited within a future boxed as `Send`, which is what
    /// an asynchronous handler is: this only has to compile.
    #[allow(dead_code)]
    fn attr_props_in_send_future(db: &DatabaseProxy) -> BoxFuture<'_, Result<()>> {
        Box::pin(async move {
            let _ = db.get_dev_attr_prop_async::<f64, _, _>("motor/dev/1", "Position", "max_value").await?;
            let _ = db.get_class_attr_prop_async::<(String, f64), _, _>("Motor", ["Position"], ("label", "max_value")).await?;
            let _ = db.get_dev_attr_prop_async::<Spectrum<str>, _, _>("motor/dev/1", All, All).await?;
            Ok(())
        })
    }

    /// The reply to a property request that was asked for the given names and answered
    /// with the given listing, which is the flat list the database speaks in: the object,
    /// how many properties follow, and then every property as its name, how many values it
    /// holds, and those values.
    fn reply(names: &[&str], listing: &[&str]) -> get_prop::PropReply {
        get_prop::PropReply::new(listing[0], Spectrum::from(listing), Spectrum::from(names)).unwrap()
    }

    /// The reply to an attribute property request that was asked for the given attributes
    /// and properties, and answered with the given listing, the flat list the database
    /// speaks in.
    fn attr_reply(attr_names: &[&str], prop_names: Option<&[&str]>, listing: &[&str]) -> get_prop::AttrPropReply {
        get_prop::AttrPropReply::new(listing[0], Spectrum::from(listing), Spectrum::from(attr_names), prop_names.map(Spectrum::from)).unwrap()
    }

    /// The database answering for another object than the one asked about, or with another
    /// count than what was asked for, fails the whole reply before anything is read out of
    /// it, and a request that asks for nothing carries nothing.
    #[test]
    fn listing_head() {

        let names = || Spectrum::from(&["prop"][..]);

        let err = get_prop::PropReply::new("obj", Spectrum::from(&["another", "1", "prop", "0"][..]), names()).unwrap_err();
        assert_eq!(err.kind(), ErrorKind::InvalidData);
        let err = get_prop::PropReply::new("obj", Spectrum::from(&["obj", "2", "prop", "0"][..]), names()).unwrap_err();
        assert_eq!(err.kind(), ErrorKind::InvalidData);
        let err = get_prop::AttrPropReply::new("obj", Spectrum::from(&["obj", "2", "prop", "0"][..]), names(), None).unwrap_err();
        assert_eq!(err.kind(), ErrorKind::InvalidData);

        let mut props = get_prop::PropReply::empty();
        assert!(props.is_empty());
        assert!(props.next().is_none());
        let mut attrs = get_prop::AttrPropReply::empty();
        assert_eq!(attrs.len(), 0);
        assert!(attrs.next().is_none());

    }

    /// The properties of an attribute, as they are taken out of its reply.
    fn attr_props(props: &mut get_prop::PropReply) -> Vec<(String, Vec<String>)> {
        let mut taken = Vec::new();
        while let Some(prop) = props.next() {
            let prop = prop.unwrap();
            taken.push((prop.name.value().to_string(), prop.value.iter().map(str::to_string).collect()));
        }
        taken
    }

    const ATTR_LISTING: &[&str] = &[
        "sys/tg_test/1", "3",
        "first", "2", "label", "1", "First", "rel_change", "2", "-1", "2",
        "empty", "1", "unit", "0", " ",
        "none", "0",
    ];

    /// The attributes come back one entry per attribute asked for, in the order they were,
    /// an attribute the database holds nothing of included, every one with every property
    /// it has when none is asked for in particular, and a property holding no value
    /// followed by a placeholder that is not one of its values.
    #[test]
    fn attr_props_in_order() {

        let mut reply = attr_reply(&["first", "empty", "none"], None, ATTR_LISTING);
        assert_eq!(reply.len(), 3);

        let Named { name, value: mut props } = reply.next().unwrap().unwrap();
        assert_eq!(name.value(), "first");
        assert_eq!(props.len(), 2);
        assert_eq!(attr_props(&mut props), [
            ("label".to_string(), vec!["First".to_string()]),
            ("rel_change".to_string(), vec!["-1".to_string(), "2".to_string()]),
        ]);

        let mut props = reply.next().unwrap().unwrap().value;
        assert_eq!(attr_props(&mut props), [("unit".to_string(), vec![])]);

        let mut props = reply.next().unwrap().unwrap().value;
        assert!(attr_props(&mut props).is_empty());

        assert!(reply.next().is_none());

    }

    /// The properties asked for are looked up among every one an attribute has ignoring the
    /// case, in the order they were asked for, one it does not have coming with no value.
    #[test]
    fn attr_prop_lookup() {

        let mut reply = attr_reply(&["first", "empty", "none"], Some(&["REL_CHANGE", "unit"]), ATTR_LISTING);

        let mut props = reply.next().unwrap().unwrap().value;
        assert_eq!(props.len(), 2);
        assert_eq!(attr_props(&mut props), [
            ("rel_change".to_string(), vec!["-1".to_string(), "2".to_string()]),
            ("unit".to_string(), vec![]),
        ]);

        let mut props = reply.next().unwrap().unwrap().value;
        assert_eq!(attr_props(&mut props), [
            ("REL_CHANGE".to_string(), vec![]),
            ("unit".to_string(), vec![]),
        ]);

    }

    /// The database naming back another attribute than the one asked for fails that
    /// attribute, as does one announcing more values than it carries, and nothing is read
    /// behind either, an attribute starting where the one before it ended.
    #[test]
    fn incoherent_attr_props() {

        let mut reply = attr_reply(&["asked", "behind"], None, &["obj", "2", "another", "0", "behind", "0"]);
        assert_eq!(reply.next().unwrap().unwrap_err().kind(), ErrorKind::InvalidData);
        assert!(reply.next().is_none());

        let mut reply = attr_reply(&["asked"], None, &["obj", "1", "asked", "1", "label", "2", "one"]);
        assert_eq!(reply.next().unwrap().unwrap_err().kind(), ErrorKind::InvalidData);

    }

    /// What an attribute property write carries: the object, how many attributes, then
    /// every attribute with how many properties it has, and every property with how many
    /// values it has and those values.
    #[test]
    fn attr_prop_write() {
        let params = attr_prop_params("obj", [
            ("first", vec![("label", "First"), ("unit", "mm")]),
            ("second", vec![("label", "Second")]),
        ]);
        assert_eq!(params.iter().collect::<Vec<_>>(), [
            "obj", "2",
            "first", "2", "label", "1", "First", "unit", "1", "mm",
            "second", "1", "label", "1", "Second",
        ]);
    }

    /// The properties come back in the order they were asked for, each with the values it
    /// holds and nothing of the ones around it.
    #[test]
    fn props_in_order() {

        let mut props = reply(&["first", "second"],
            &["sys/tg_test/1", "2", "first", "1", "one", "second", "2", "two", "three"]);

        assert_eq!(props.len(), 2);

        let Named { name, value: values } = props.next().unwrap().unwrap();
        assert_eq!(name.value(), "first");
        assert_eq!(values.iter().collect::<Vec<_>>(), ["one"]);

        let Named { name, value: values } = props.next().unwrap().unwrap();
        assert_eq!(name.value(), "second");
        assert_eq!(values.iter().collect::<Vec<_>>(), ["two", "three"]);

        assert!(props.next().is_none());

    }

    /// A property that is defined and holds nothing comes back with no value at all, which
    /// is not the same as it not being there.
    #[test]
    fn prop_without_value() {
        let mut props = reply(&["empty"], &["obj", "1", "empty", "0"]);
        let Named { name, value: values } = props.next().unwrap().unwrap();
        assert_eq!(name.value(), "empty");
        assert!(values.is_empty());
    }

    /// The database naming another property back than the one that was asked for is it
    /// breaking the order the answer is read in, which that one property fails with.
    #[test]
    fn incoherent_prop_name() {
        let mut props = reply(&["asked"], &["obj", "1", "another", "1", "one"]);
        let err = props.next().unwrap().unwrap_err();
        assert_eq!(err.kind(), ErrorKind::InvalidData);
    }

    /// A property announcing more values than the listing carries fails: the values are a
    /// slice of the listing and there is nothing there to slice.
    ///
    /// Nothing is read behind it either, a property starting where the one before it ended.
    #[test]
    fn missing_prop_values() {
        let mut props = reply(&["prop", "behind"], &["obj", "2", "prop", "2", "one"]);
        let err = props.next().unwrap().unwrap_err();
        assert_eq!(err.kind(), ErrorKind::InvalidData);
        assert!(props.next().is_none());
    }

    /// One name asks for one property, which is parsed into the type the caller expects of
    /// it and is the output itself.
    #[test]
    fn single_prop_parsed() {
        let mut props = reply(&["prop"], &["obj", "1", "prop", "1", "3.5"]);
        let value = <f64 as GetPropSpec<&str>>::collect(&mut props).unwrap();
        assert_eq!(value, 3.5);
    }

}