use std::sync::{Arc, Mutex};

use crate::protocol::wl_display;
use crate::protocol::wl_registry;
use crate::{Attached, DispatchData, Interface, Main, Proxy};

struct Inner {
    list: Vec<(u32, String, u32)>,
}

/// An utility to manage global objects
///
/// This utility provides an implemenation for the registry
/// that track the list of globals for you, as well as utilities
/// to bind them.
#[derive(Clone)]
pub struct GlobalManager {
    inner: Arc<Mutex<Inner>>,
    registry: Main<wl_registry::WlRegistry>,
}

/// An error that occurred trying to bind a global
#[derive(Debug, PartialEq)]
pub enum GlobalError {
    /// The requested global was missing
    Missing,
    /// The global advertised by the server has a lower version number
    /// than the one requested
    VersionTooLow(u32),
}

impl ::std::error::Error for GlobalError {}

impl ::std::fmt::Display for GlobalError {
    fn fmt(&self, f: &mut ::std::fmt::Formatter) -> Result<(), ::std::fmt::Error> {
        match *self {
            GlobalError::Missing => f.write_str("The requested global was missing."),
            GlobalError::VersionTooLow(_) => {
                f.write_str("The requested global's version is too low.")
            }
        }
    }
}

/// Event provided to the user callback of GlobalManager
pub enum GlobalEvent {
    /// A new global was created
    New {
        /// Id of the new global
        id: u32,
        /// Interface of the new global
        interface: String,
        /// Maximum supported version of the new global
        version: u32,
    },
    /// A global was removed
    Removed {
        /// Id of the removed global
        id: u32,
        /// Interface of the removed global
        interface: String,
    },
}

impl GlobalManager {
    /// Create a global manager handling a registry
    ///
    /// You need to provide an attached handle of the Waland display, and the
    /// global manager will be managed by the associated event queue.
    pub fn new(display: &Attached<wl_display::WlDisplay>) -> GlobalManager {
        let inner = Arc::new(Mutex::new(Inner { list: Vec::new() }));
        let inner_clone = inner.clone();

        let registry = display
            .as_ref()
            .send::<wl_registry::WlRegistry>(wl_display::Request::GetRegistry {}, None)
            .unwrap();
        registry.quick_assign(move |_proxy, msg, _data| {
            let mut inner = inner.lock().unwrap();
            match msg {
                wl_registry::Event::Global { name, interface, version } => {
                    inner.list.push((name, interface, version));
                }
                wl_registry::Event::GlobalRemove { name } => {
                    inner.list.retain(|&(n, _, _)| n != name);
                }
            }
        });

        GlobalManager { inner: inner_clone, registry }
    }

    /// Create a global manager handling a registry with a callback
    ///
    /// This global manager will track globals as a simple one, but will
    /// also forward the registry events to your callback.
    ///
    /// This can be used if you want to handle specially certain globals, but want
    /// to use the default mechanism for the rest.
    ///
    /// You need to provide an attached handle of the Waland display, and the
    /// global manager will be managed by the associated event queue.
    pub fn new_with_cb<F>(
        display: &Attached<wl_display::WlDisplay>,
        mut callback: F,
    ) -> GlobalManager
    where
        F: FnMut(GlobalEvent, Attached<wl_registry::WlRegistry>, DispatchData) + 'static,
    {
        let inner = Arc::new(Mutex::new(Inner { list: Vec::new() }));
        let inner_clone = inner.clone();

        let registry = display
            .as_ref()
            .send::<wl_registry::WlRegistry>(wl_display::Request::GetRegistry {}, None)
            .unwrap();
        registry.quick_assign(move |proxy, msg, data| {
            let mut inner = inner.lock().unwrap();
            let inner = &mut *inner;
            match msg {
                wl_registry::Event::Global {
                    name,
                    interface,
                    version,
                } => {
                    inner.list.push((name, interface.clone(), version));
                    callback(
                        GlobalEvent::New {
                            id: name,
                            interface,
                            version,
                        },
                        (*proxy).clone(),
                        data,
                    );
                }
                wl_registry::Event::GlobalRemove { name } => {
                    if let Some((i, _)) = inner.list.iter().enumerate().find(|&(_, &(n, _, _))| n == name) {
                        let (id, interface, _) = inner.list.swap_remove(i);
                        callback(GlobalEvent::Removed { id, interface }, (*proxy).clone(), data);
                    } else {
                        panic!(
                            "Wayland protocol error: the server removed non-existing global \"{}\".",
                            name
                        );
                    }
                }
            }
        });

        GlobalManager { inner: inner_clone, registry }
    }

    /// Instantiate a global with a specific version
    ///
    /// Meaning of requests and events can change depending on the object version you use,
    /// as such unless you specifically want to support several versions of a protocol, it is
    /// recommended to use this method with an hardcoded value for the version (the one you'll
    /// use a as reference for your implementation). Notably you should *not* use `I::VERSION`
    /// as a version, as this value can change when the protocol files are updated.
    ///
    /// This method is only appropriate for globals that are expected to
    /// not exist with multiplicity (such as `wl_compositor` or `wl_shm`),
    /// as it will always bind the first one that was advertized.
    pub fn instantiate_exact<I>(&self, version: u32) -> Result<Main<I>, GlobalError>
    where
        I: Interface + AsRef<Proxy<I>> + From<Proxy<I>>,
    {
        let inner = self.inner.lock().unwrap();
        for &(id, ref interface, server_version) in &inner.list {
            if interface == I::NAME {
                if version > server_version {
                    return Err(GlobalError::VersionTooLow(server_version));
                } else {
                    return Ok(self.registry.bind::<I>(version, id));
                }
            }
        }
        Err(GlobalError::Missing)
    }

    /// Instantiate a global from a version range
    ///
    /// If you want to support several versions of a particular global, this method allows you to
    /// specify a range of versions that you accept. It'll bind the highest possible version that
    /// is between `min_version` and `max_version` inclusive, and return an error if the highest
    /// version supported by the compositor is lower than `min_version`. As for
    /// `instantiate_exact`, you should not use `I::VERSION` here: the versions your code support
    /// do not change when the protocol files are updated.
    ///
    /// When trying to support several versions of a protocol, you can check which version has
    /// actually been used on any object using the `Proxy::version()` method.
    ///
    /// As `instantiate_exact`, it should only be used for singleton globals, for the same reasons.
    pub fn instantiate_range<I>(
        &self,
        min_version: u32,
        max_version: u32,
    ) -> Result<Main<I>, GlobalError>
    where
        I: Interface + AsRef<Proxy<I>> + From<Proxy<I>>,
    {
        let inner = self.inner.lock().unwrap();
        for &(id, ref interface, version) in &inner.list {
            if interface == I::NAME {
                if version >= min_version {
                    let version = ::std::cmp::min(version, max_version);
                    return Ok(self.registry.bind::<I>(version, id));
                } else {
                    return Err(GlobalError::VersionTooLow(version));
                }
            }
        }
        Err(GlobalError::Missing)
    }

    /// Retrieve the list of currently known globals
    pub fn list(&self) -> Vec<(u32, String, u32)> {
        self.inner.lock().unwrap().list.clone()
    }
}

/// A trait for implementation of the global advertisement
///
/// It is automatically implemented for `FnMut(Main<I>, DispatchData)` closures,
/// in which case the `error` messages are ignored.
pub trait GlobalImplementor<I: Interface + AsRef<Proxy<I>> + From<Proxy<I>>> {
    /// A new global of given interface has been instantiated and you can assign
    /// a filter to it.
    fn new_global(&mut self, global: Main<I>, data: DispatchData);
    /// A global was advertised but its version was lower than the minimal version
    /// you requested.
    ///
    /// The advertised version is provided as argument.
    fn error(&mut self, _version: u32, _data: DispatchData) {}
}

impl<F, I: Interface> GlobalImplementor<I> for F
where
    I: Interface + AsRef<Proxy<I>> + From<Proxy<I>>,
    F: FnMut(Main<I>, DispatchData),
{
    fn new_global(&mut self, global: Main<I>, data: DispatchData) {
        (*self)(global, data)
    }
}

/// Convenience macro to create a `GlobalManager` callback
///
/// This macro aims to simplify the specific but common case of
/// providing a callback to the `GlobalManager` that needs to
/// auto-bind all advertised instances of some specific globals
/// whenever they happen. Typically, your application will likely
/// want to keep track of all `wl_seat` and `wl_output` globals
/// to be able to correctly react to user input and their different
/// monitors.
///
/// The output of this macro is a closure, that can be given to
/// `GlobalManager::new_with_cb` as the callback argument.
///
/// Example use is typically:
///
/// ```no_run
/// # #[macro_use] extern crate wayland_client;
/// use wayland_client::GlobalManager;
/// # use wayland_client::{Display, Main, DispatchData};
/// use wayland_client::protocol::{wl_output, wl_seat};
///
/// # fn main() {
/// # let display = Display::connect_to_env().unwrap();
/// # let mut event_queue = display.create_event_queue();
/// # let seat_implementor: fn(Main<_>, DispatchData) = unimplemented!();
/// # let output_implementor: fn(Main<_>, DispatchData) = unimplemented!();
/// let globals = GlobalManager::new_with_cb(
///     &display.attach(event_queue.token()),
///     global_filter!(
///         // Bind all wl_seat with version 4
///         [wl_seat::WlSeat, 4, seat_implementor],
///         // Bind all wl_output with version 1
///         [wl_output::WlOutput, 1, output_implementor]
///     )
/// );
/// # }
/// ```
///
/// The supplied callbacks for each global kind must be an instance of a type
/// implementing the `GlobalImplementor<I>` trait. The argument provided to your
/// callback is a `Main` handle of the newly instantiated global, and you should assign it
/// to a filter in this callback if you plan to do so.. The error case happens if the server
/// advertised a lower version of the global than the one you requested, in which case you
/// are given the version it advertised in the error method, if you want to handle it graciously.
///
/// You can also provide closures for the various callbacks, in this case the errors will
/// be ignored. However, due to a lack of capability of rustc's inference, you'll likely need
/// to add some type annotation to your closure, typically something like this:
///
/// ```ignore
/// global_filter!(
///     [Interface, version, |proxy: Main<_>, dispatch_data| {
///         /* Setup the global as required */
///     }]
/// );
/// ```
#[macro_export]
macro_rules! global_filter {
    ($([$interface:ty, $version:expr, $callback:expr]),*) => {
        {
            use $crate::protocol::wl_registry;
            use $crate::{GlobalEvent, Interface, Attached, GlobalImplementor, DispatchData};
            type Callback = Box<dyn FnMut(u32, u32, Attached<wl_registry::WlRegistry>, DispatchData<'_>)>;
            let mut callbacks: Vec<(&'static str, Callback)> = Vec::new();
            // Create the callback list
            $({
                let mut cb = { $callback };
                callbacks.push((
                    <$interface as Interface>::NAME,
                    Box::new(move |id, version, registry: Attached<wl_registry::WlRegistry>, ddata: DispatchData| {
                        if version < $version {
                            GlobalImplementor::<$interface>::error(&mut cb, version, ddata);
                        } else {
                            let proxy = registry.bind::<$interface>(version, id);
                            GlobalImplementor::<$interface>::new_global(&mut cb, proxy, ddata);
                        }
                    }) as Box<_>
                ));
            })*

            // return the global closure
            move |event: GlobalEvent, registry: Attached<wl_registry::WlRegistry>, ddata| {
                if let GlobalEvent::New { id, interface, version } = event {
                    for &mut (iface, ref mut cb) in &mut callbacks {
                        if iface == interface {
                            cb(id, version, registry, ddata);
                            break;
                        }
                    }
                }
            }
        }
    }
}