use std::{ffi::CString, sync::Arc};

use crate::{
    core_interfaces::{WL_DISPLAY_INTERFACE, WL_REGISTRY_INTERFACE},
    protocol::{same_interface, Argument, Interface, Message, ObjectInfo, ANONYMOUS_INTERFACE},
    types::server::{DisconnectReason, GlobalInfo, InvalidId},
};
use smallvec::SmallVec;

use super::{
    client::ClientStore, registry::Registry, ClientData, ClientId, Credentials, Data,
    GlobalHandler, GlobalId, ObjectData, ObjectId,
};
use crate::rs::map::Object;

/// Main handle of a backend to the Wayland protocol
///
/// This type hosts most of the protocol-related functionality of the backend, and is the
/// main entry point for manipulating Wayland objects. It can be retrieved both from
/// the backend via [`Backend::handle()`](super::Backend::handle), and is given to you as argument
/// in most event callbacks.
#[derive(Debug)]
pub struct Handle<D> {
    pub(crate) clients: ClientStore<D>,
    pub(crate) registry: Registry<D>,
}

enum DispatchAction<D> {
    Request {
        object: Object<Data<D>>,
        object_id: ObjectId,
        opcode: u16,
        arguments: SmallVec<[Argument<ObjectId>; 4]>,
        is_destructor: bool,
        created_id: Option<ObjectId>,
    },
    Bind {
        object: ObjectId,
        client: ClientId,
        global: GlobalId,
        handler: Arc<dyn GlobalHandler<D>>,
    },
}

impl<D> Handle<D> {
    pub(crate) fn new() -> Self {
        let debug =
            matches!(std::env::var_os("WAYLAND_DEBUG"), Some(str) if str == "1" || str == "server");
        Handle { clients: ClientStore::new(debug), registry: Registry::new() }
    }

    pub(crate) fn cleanup(&mut self) {
        let dead_clients = self.clients.cleanup();
        self.registry.cleanup(&dead_clients);
    }

    pub(crate) fn dispatch_events_for(
        &mut self,
        data: &mut D,
        client_id: ClientId,
    ) -> std::io::Result<usize> {
        let mut dispatched = 0;
        loop {
            let action = if let Ok(client) = self.clients.get_client_mut(client_id.clone()) {
                let (message, object) = match client.next_request() {
                    Ok(v) => v,
                    Err(e) if e.kind() == std::io::ErrorKind::WouldBlock => {
                        if dispatched > 0 {
                            break;
                        } else {
                            return Err(e);
                        }
                    }
                    Err(e) => return Err(e),
                };
                dispatched += 1;
                if same_interface(object.interface, &WL_DISPLAY_INTERFACE) {
                    client.handle_display_request(message, &mut self.registry);
                    continue;
                } else if same_interface(object.interface, &WL_REGISTRY_INTERFACE) {
                    if let Some((client, global, object, handler)) =
                        client.handle_registry_request(message, &mut self.registry)
                    {
                        DispatchAction::Bind { client, global, object, handler }
                    } else {
                        continue;
                    }
                } else {
                    let object_id = ObjectId {
                        id: message.sender_id,
                        serial: object.data.serial,
                        interface: object.interface,
                        client_id: client.id.clone(),
                    };
                    let opcode = message.opcode;
                    let (arguments, is_destructor, created_id) =
                        match client.process_request(&object, message) {
                            Some(args) => args,
                            None => continue,
                        };
                    // Return the whole set to invoke the callback while handle is not borrower via client
                    DispatchAction::Request {
                        object,
                        object_id,
                        opcode,
                        arguments,
                        is_destructor,
                        created_id,
                    }
                }
            } else {
                return Err(std::io::Error::new(
                    std::io::ErrorKind::InvalidInput,
                    "Invalid client ID",
                ));
            };
            match action {
                DispatchAction::Request {
                    object,
                    object_id,
                    opcode,
                    arguments,
                    is_destructor,
                    created_id,
                } => {
                    let ret = object.data.user_data.clone().request(
                        self,
                        data,
                        client_id.clone(),
                        Message { sender_id: object_id.clone(), opcode, args: arguments },
                    );
                    if is_destructor {
                        object.data.user_data.destroyed(client_id.clone(), object_id.clone());
                        if let Ok(client) = self.clients.get_client_mut(client_id.clone()) {
                            client.send_delete_id(object_id);
                        }
                    }
                    match (created_id, ret) {
                        (Some(child_id), Some(child_data)) => {
                            if let Ok(client) = self.clients.get_client_mut(client_id.clone()) {
                                client
                                    .map
                                    .with(child_id.id, |obj| obj.data.user_data = child_data)
                                    .unwrap();
                            }
                        }
                        (None, None) => {}
                        (Some(child_id), None) => {
                            panic!(
                                "Callback creating object {} did not provide any object data.",
                                child_id
                            );
                        }
                        (None, Some(_)) => {
                            panic!("An object data was returned from a callback not creating any object");
                        }
                    }
                }
                DispatchAction::Bind { object, client, global, handler } => {
                    let child_data =
                        handler.bind(self, data, client.clone(), global, object.clone());
                    if let Ok(client) = self.clients.get_client_mut(client.clone()) {
                        client.map.with(object.id, |obj| obj.data.user_data = child_data).unwrap();
                    }
                }
            }
        }
        Ok(dispatched)
    }

    pub(crate) fn flush(&mut self, client: Option<ClientId>) -> std::io::Result<()> {
        if let Some(client) = client {
            match self.clients.get_client_mut(client) {
                Ok(client) => client.flush(),
                Err(InvalidId) => Ok(()),
            }
        } else {
            for client in self.clients.clients_mut() {
                let _ = client.flush();
            }
            Ok(())
        }
    }
}

impl<D> Handle<D> {
    /// Returns information about some object.
    pub fn object_info(&self, id: ObjectId) -> Result<ObjectInfo, InvalidId> {
        self.clients.get_client(id.client_id.clone())?.object_info(id)
    }

    /// Returns the id of the client which owns the object.
    pub fn get_client(&self, id: ObjectId) -> Result<ClientId, InvalidId> {
        if self.clients.get_client(id.client_id.clone()).is_ok() {
            Ok(id.client_id)
        } else {
            Err(InvalidId)
        }
    }

    /// Returns the data associated with a client.
    pub fn get_client_data(&self, id: ClientId) -> Result<Arc<dyn ClientData<D>>, InvalidId> {
        let client = self.clients.get_client(id)?;
        Ok(client.data.clone())
    }

    /// Retrive the [`Credentials`] of a client
    pub fn get_client_credentials(&self, id: ClientId) -> Result<Credentials, InvalidId> {
        let client = self.clients.get_client(id)?;
        Ok(client.get_credentials())
    }

    /// Returns an iterator over all clients connected to the server.
    pub fn all_clients<'a>(&'a self) -> Box<dyn Iterator<Item = ClientId> + 'a> {
        Box::new(self.clients.all_clients_id())
    }

    /// Returns an iterator over all objects owned by a client.
    pub fn all_objects_for<'a>(
        &'a self,
        client_id: ClientId,
    ) -> Result<Box<dyn Iterator<Item = ObjectId> + 'a>, InvalidId> {
        let client = self.clients.get_client(client_id)?;
        Ok(Box::new(client.all_objects()))
    }

    /// Retrieve the `ObjectId` for a wayland object given its protocol numerical ID
    pub fn object_for_protocol_id(
        &self,
        client_id: ClientId,
        interface: &'static Interface,
        protocol_id: u32,
    ) -> Result<ObjectId, InvalidId> {
        let client = self.clients.get_client(client_id)?;
        let object = client.object_for_protocol_id(protocol_id)?;
        if same_interface(interface, object.interface) {
            Ok(object)
        } else {
            Err(InvalidId)
        }
    }

    /// Create a new object for given client
    ///
    /// To ensure state coherence of the protocol, the created object should be immediately
    /// sent as a "New ID" argument in an event to the client.
    pub fn create_object(
        &mut self,
        client_id: ClientId,
        interface: &'static Interface,
        version: u32,
        data: Arc<dyn ObjectData<D>>,
    ) -> Result<ObjectId, InvalidId> {
        let client = self.clients.get_client_mut(client_id)?;
        Ok(client.create_object(interface, version, data))
    }

    /// Returns an object id that represents a null object.
    pub fn null_id(&mut self) -> ObjectId {
        ObjectId {
            id: 0,
            serial: 0,
            client_id: ClientId { id: 0, serial: 0 },
            interface: &ANONYMOUS_INTERFACE,
        }
    }

    /// Send an event to the client
    ///
    /// Returns an error if the sender ID of the provided message is no longer valid.
    ///
    /// **Panic:**
    ///
    /// Checks against the protocol specification are done, and this method will panic if they do
    /// not pass:
    ///
    /// - the message opcode must be valid for the sender interface
    /// - the argument list must match the prototype for the message associated with this opcode
    pub fn send_event(&mut self, msg: Message<ObjectId>) -> Result<(), InvalidId> {
        self.clients.get_client_mut(msg.sender_id.client_id.clone())?.send_event(msg)
    }

    /// Returns the data associated with an object.
    pub fn get_object_data(&self, id: ObjectId) -> Result<Arc<dyn ObjectData<D>>, InvalidId> {
        self.clients.get_client(id.client_id.clone())?.get_object_data(id)
    }

    /// Sets the data associated with some object.
    pub fn set_object_data(
        &mut self,
        id: ObjectId,
        data: Arc<dyn ObjectData<D>>,
    ) -> Result<(), InvalidId> {
        self.clients.get_client_mut(id.client_id.clone())?.set_object_data(id, data)
    }

    /// Posts an error on an object. This will also disconnect the client which created the object.
    pub fn post_error(&mut self, object_id: ObjectId, error_code: u32, message: CString) {
        if let Ok(client) = self.clients.get_client_mut(object_id.client_id.clone()) {
            client.post_error(object_id, error_code, message)
        }
    }

    /// Kills the connection to a client.
    ///
    /// The disconnection reason determines the error message that is sent to the client (if any).
    pub fn kill_client(&mut self, client_id: ClientId, reason: DisconnectReason) {
        if let Ok(client) = self.clients.get_client_mut(client_id) {
            client.kill(reason)
        }
    }

    /// Creates a global of the specified interface and version and then advertises it to clients.
    ///
    /// The clients which the global is advertised to is determined by the implementation of the [`GlobalHandler`].
    pub fn create_global(
        &mut self,
        interface: &'static Interface,
        version: u32,
        handler: Arc<dyn GlobalHandler<D>>,
    ) -> GlobalId {
        self.registry.create_global(interface, version, handler, &mut self.clients)
    }

    /// Disables a global object that is currently active.
    ///
    /// The global removal will be signaled to all currently connected clients. New clients will not know of the global,
    /// but the associated state and callbacks will not be freed. As such, clients that still try to bind the global
    /// afterwards (because they have not yet realized it was removed) will succeed.
    pub fn disable_global(&mut self, id: GlobalId) {
        self.registry.disable_global(id, &mut self.clients)
    }

    /// Removes a global object and free its ressources.
    ///
    /// The global object will no longer be considered valid by the server, clients trying to bind it will be killed,
    /// and the global ID is freed for re-use.
    ///
    /// It is advised to first disable a global and wait some amount of time before removing it, to ensure all clients
    /// are correctly aware of its removal. Note that clients will generally not expect globals that represent a capability
    /// of the server to be removed, as opposed to globals representing peripherals (like `wl_output` or `wl_seat`).
    pub fn remove_global(&mut self, id: GlobalId) {
        self.registry.remove_global(id, &mut self.clients)
    }

    /// Returns information about a global.
    pub fn global_info(&self, id: GlobalId) -> Result<GlobalInfo, InvalidId> {
        self.registry.get_info(id)
    }

    /// Returns the handler which manages the visibility and notifies when a client has bound the global.
    pub fn get_global_handler(&self, id: GlobalId) -> Result<Arc<dyn GlobalHandler<D>>, InvalidId> {
        self.registry.get_handler(id)
    }
}