use baseview::{EventStatus, Window, WindowHandler, WindowOpenOptions};
use parking_lot::RwLock;
use raw_window_handle::HasRawWindowHandle;
use std::any::Any;
use std::sync::Arc;

use super::context::{WrapperGuiContext, WrapperProcessContext};
use crate::context::Transport;
use crate::plugin::{BufferConfig, BusConfig, Editor, ParentWindowHandle, Plugin};

/// 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> {
    /// The wrapped plugin instance.
    plugin: RwLock<P>,
    /// 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.
    editor: Option<Arc<dyn Editor>>,

    config: WrapperConfig,

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

/// 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,
}

/// We need a window handler for baseview, but since we only create a window to report the plugin in
/// this won't do much.
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>,
}

impl WindowHandler for WrapperWindowHandler {
    fn on_frame(&mut self, _window: &mut Window) {}

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

impl<P: Plugin> Wrapper<P> {
    /// 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(config: WrapperConfig) -> Result<Arc<Self>, WrapperError> {
        let plugin = P::default();
        let editor = plugin.editor().map(Arc::from);

        let wrapper = Arc::new(Wrapper {
            plugin: RwLock::new(plugin),
            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,
        });

        // 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> {
        // TODO: Do IO things, kinda important

        match self.editor.clone() {
            Some(editor) => {
                let context = self.clone().make_gui_context();
                let (width, height) = editor.size();

                // 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)
                };

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

        Ok(())
    }

    fn make_gui_context(self: Arc<Self>) -> Arc<WrapperGuiContext<P>> {
        Arc::new(WrapperGuiContext { wrapper: self })
    }

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