use atomic_refcell::AtomicRefCell;
use baseview::{EventStatus, Window, WindowHandler, WindowOpenOptions};
use crossbeam::queue::ArrayQueue;
use parking_lot::{Mutex, RwLock};
use raw_window_handle::HasRawWindowHandle;
use std::any::Any;
use std::collections::HashSet;
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::Arc;
use std::thread;

use super::backend::Backend;
use super::context::{WrapperGuiContext, WrapperProcessContext};
use crate::context::Transport;
use crate::param::internals::{ParamPtr, Params};
use crate::param::ParamFlags;
use crate::plugin::{BufferConfig, BusConfig, Editor, ParentWindowHandle, Plugin};

/// How many parameter changes we can store in our unprocessed parameter change queue. Storing more
/// than this many parmaeters at a time will cause changes to get lost.
const EVENT_QUEUE_CAPACITY: usize = 2048;

/// Configuration for a standalone plugin that would normally be provided by the DAW.
#[derive(Debug, Clone)]
pub struct WrapperConfig {
    /// The number of input channels.
    pub input_channels: u32,
    /// The number of output channels.
    pub output_channels: u32,
    /// The audio backend's sample rate.
    pub sample_rate: f32,
    /// The audio backend's period size.
    pub period_size: u32,

    /// The editor's DPI scaling factor. Currently baseview has no way to report this to us, so
    /// we'll expose it as a command line option instead.
    ///
    /// This option is ignored on macOS.
    pub dpi_scale: f32,

    /// The current tempo.
    pub tempo: f32,
    /// The time signature's numerator.
    pub timesig_num: u32,
    /// The time signature's denominator.
    pub timesig_denom: u32,
}

pub struct Wrapper<P: Plugin, B: Backend> {
    backend: AtomicRefCell<B>,

    /// The wrapped plugin instance.
    plugin: RwLock<P>,
    /// The plugin's parameters. These are fetched once during initialization. That way the
    /// `ParamPtr`s are guaranteed to live at least as long as this object and we can interact with
    /// the `Params` object without having to acquire a lock on `plugin`.
    _params: Arc<dyn Params>,
    /// The plugin's editor, if it has one. This object does not do anything on its own, but we need
    /// to instantiate this in advance so we don't need to lock the entire [`Plugin`] object when
    /// creating an editor.
    pub editor: Option<Arc<dyn Editor>>,

    config: WrapperConfig,

    /// The bus and buffer configurations are static for the standalone target.
    bus_config: BusConfig,
    buffer_config: BufferConfig,

    /// The set of parameter pointers in `params`. This is technically not necessary, but for
    /// consistency with the plugin wrappers we'll check whether the `ParamPtr` for an incoming
    /// parameter change actually belongs to a registered parameter.
    known_parameters: HashSet<ParamPtr>,
    /// Parameter changes that have been output by the GUI that have not yet been set in the plugin.
    /// This queue will be flushed at the end of every processing cycle, just like in the plugin
    /// versions.
    unprocessed_param_changes: ArrayQueue<(ParamPtr, f32)>,
}

/// Errors that may arise while initializing the wrapped plugins.
#[derive(Debug, Clone, Copy)]
pub enum WrapperError {
    /// The plugin does not accept the IO configuration from the config.
    IncompatibleConfig,
    /// The plugin returned `false` during initialization.
    InitializationFailed,
}

struct WrapperWindowHandler {
    /// The editor handle for the plugin's open editor. The editor should clean itself up when it
    /// gets dropped.
    _editor_handle: Box<dyn Any>,

    /// If contains a value, then the GUI will be resized at the start of the next frame. This is
    /// set from [`WrapperGuiContext::request_resize()`].
    new_window_size: Arc<Mutex<Option<(u32, u32)>>>,
}

impl WindowHandler for WrapperWindowHandler {
    fn on_frame(&mut self, window: &mut Window) {
        if let Some((new_width, new_height)) = self.new_window_size.lock().take() {
            // Window resizing in baseview has only been implemented on Linux
            #[cfg(target_os = "linux")]
            {
                window.resize(baseview::Size {
                    width: new_width as f64,
                    height: new_height as f64,
                });
            }
        }
    }

    fn on_event(&mut self, _window: &mut Window, _event: baseview::Event) -> EventStatus {
        EventStatus::Ignored
    }
}

impl<P: Plugin, B: Backend> Wrapper<P, B> {
    /// Instantiate a new instance of the standalone wrapper. Returns an error if the plugin does
    /// not accept the IO configuration from the wrapper config.
    pub fn new(backend: B, config: WrapperConfig) -> Result<Arc<Self>, WrapperError> {
        let plugin = P::default();
        let params = plugin.params();
        let editor = plugin.editor().map(Arc::from);

        // For consistency's sake we'll include the same assertions as the other backends
        // TODO: Move these common checks to a function instead of repeating them in every wrapper
        let param_map = params.param_map();
        if cfg!(debug_assertions) {
            let param_ids: HashSet<_> = param_map.iter().map(|(id, _, _)| id.clone()).collect();
            nih_debug_assert_eq!(
                param_map.len(),
                param_ids.len(),
                "The plugin has duplicate parameter IDs, weird things may happen. \
                 Consider using 6 character parameter IDs to avoid collissions.."
            );

            let mut bypass_param_exists = false;
            for (_, ptr, _) in &param_map {
                let flags = unsafe { ptr.flags() };
                let is_bypass = flags.contains(ParamFlags::BYPASS);

                if is_bypass && bypass_param_exists {
                    nih_debug_assert_failure!(
                        "Duplicate bypass parameters found, the host will only use the first one"
                    );
                }

                bypass_param_exists |= is_bypass;
            }
        }

        let wrapper = Arc::new(Wrapper {
            backend: AtomicRefCell::new(backend),

            plugin: RwLock::new(plugin),
            _params: params,
            editor,

            bus_config: BusConfig {
                num_input_channels: config.input_channels,
                num_output_channels: config.output_channels,
            },
            buffer_config: BufferConfig {
                sample_rate: config.sample_rate,
                max_buffer_size: config.period_size,
            },
            config,

            known_parameters: param_map.into_iter().map(|(_, ptr, _)| ptr).collect(),
            unprocessed_param_changes: ArrayQueue::new(EVENT_QUEUE_CAPACITY),
        });

        // Right now the IO configuration is fixed in the standalone target, so if the plugin cannot
        // work with this then we cannot initialize the plugin at all.
        {
            let mut plugin = wrapper.plugin.write();
            if !plugin.accepts_bus_config(&wrapper.bus_config) {
                return Err(WrapperError::IncompatibleConfig);
            }

            if !plugin.initialize(
                &wrapper.bus_config,
                &wrapper.buffer_config,
                &mut wrapper.make_process_context(Transport::new(wrapper.config.sample_rate)),
            ) {
                return Err(WrapperError::InitializationFailed);
            }
        }

        Ok(wrapper)
    }

    /// Open the editor, start processing audio, and block this thread until the editor is closed.
    /// If the plugin does not have an editor, then this will block until SIGINT is received.
    ///
    /// Will return an error if the plugin threw an error during audio processing or if the editor
    /// could not be opened.
    pub fn run(self: Arc<Self>) -> Result<(), WrapperError> {
        // We'll spawn a separate thread to handle IO and to process audio. This audio thread should
        // terminate together with this function.
        let terminate_audio_thread = Arc::new(AtomicBool::new(false));
        let audio_thread = {
            let terminate_audio_thread = terminate_audio_thread.clone();
            let this = self.clone();
            thread::spawn(move || this.run_audio_thread(terminate_audio_thread))
        };

        match self.editor.clone() {
            Some(editor) => {
                // We'll use this mutex to communicate window size changes. If we need to send a lot
                // more information to the window handler at some point, then consider replacing
                // this with a channel.
                let new_window_size = Arc::new(Mutex::new(None));
                let context = self.clone().make_gui_context(new_window_size.clone());

                // DPI scaling should not be used on macOS since the OS handles it there
                #[cfg(target_os = "macos")]
                let scaling_policy = baseview::WindowScalePolicy::SystemScaleFactor;
                #[cfg(not(target_os = "macos"))]
                let scaling_policy = {
                    editor.set_scale_factor(self.config.dpi_scale);
                    baseview::WindowScalePolicy::ScaleFactor(self.config.dpi_scale as f64)
                };

                let (width, height) = editor.size();
                Window::open_blocking(
                    WindowOpenOptions {
                        title: String::from(P::NAME),
                        size: baseview::Size {
                            width: width as f64,
                            height: height as f64,
                        },
                        scale: scaling_policy,
                        gl_config: None,
                    },
                    move |window| {
                        // TODO: This spawn function should be able to fail and return an error, but
                        //       baseview does not support this yet. Once this is added, we should
                        //       immediately close the parent window when this happens so the loop
                        //       can exit.
                        let editor_handle = editor.spawn(
                            ParentWindowHandle {
                                handle: window.raw_window_handle(),
                            },
                            context,
                        );

                        WrapperWindowHandler {
                            _editor_handle: editor_handle,
                            new_window_size,
                        }
                    },
                )
            }
            None => {
                // TODO: Block until SIGINT is received if the plugin does not have an editor
                todo!("Support standalone plugins without editors");
            }
        }

        terminate_audio_thread.store(true, Ordering::SeqCst);
        audio_thread.join().unwrap();

        Ok(())
    }

    /// Set a parameter based on a `ParamPtr`. The value will be updated at the end of the next
    /// processing cycle, and this won't do anything if the parameter has not been registered by the
    /// plugin.
    ///
    /// This returns false if the parmeter was not set because the `Paramptr` was either unknown or
    /// the queue is full.
    pub fn set_parameter(&self, param: ParamPtr, normalized: f32) -> bool {
        if !self.known_parameters.contains(&param) {
            return false;
        }

        let push_succesful = self
            .unprocessed_param_changes
            .push((param, normalized))
            .is_ok();
        nih_debug_assert!(push_succesful, "The parmaeter change queue was full");

        push_succesful
    }

    /// The audio thread. This should be called from another thread, and it will run until
    /// `should_terminate` is `true`.
    fn run_audio_thread(self: Arc<Self>, should_terminate: Arc<AtomicBool>) {
        self.clone().backend.borrow_mut().run(move |buffer| {
            if should_terminate.load(Ordering::SeqCst) {
                return false;
            }

            // TODO: Process incoming events
            // TODO: Process audio
            // TODO: Handle parameter chagnes

            // We'll always write these events to the first sample, so even when we add note output we
            // shouldn't have to think about interleaving events here
            let sample_rate = self.buffer_config.sample_rate;
            let mut parameter_values_changed = false;
            while let Some((param_ptr, normalized_value)) = self.unprocessed_param_changes.pop() {
                unsafe { param_ptr.set_normalized_value(normalized_value) };
                unsafe { param_ptr.update_smoother(sample_rate, false) };
                parameter_values_changed = true;
            }

            // Allow the editor to react to the new parameter values if the editor uses a reactive data
            // binding model
            if parameter_values_changed {
                if let Some(editor) = &self.editor {
                    editor.param_values_changed();
                }
            }

            // TODO: MIDI output
            // TODO: Handle state restore

            true
        });
    }

    fn make_gui_context(
        self: Arc<Self>,
        new_window_size: Arc<Mutex<Option<(u32, u32)>>>,
    ) -> Arc<WrapperGuiContext<P, B>> {
        Arc::new(WrapperGuiContext {
            wrapper: self,
            new_window_size,
        })
    }

    fn make_process_context(&self, transport: Transport) -> WrapperProcessContext<'_, P, B> {
        WrapperProcessContext {
            wrapper: self,
            transport,
        }
    }
}