use std::borrow::Cow;
use std::ffi::{CStr, CString};

use ecs::actions::Actions;
use ecs::extension::Collector as ExtensionCollector;
use ecs::sole::Single;
use ecs::Sole;
use glfw::WindowSize;

use crate::data_types::dimens::Dimens;
use crate::event::{Conclude as ConcludeEvent, Start as StartEvent};
use crate::vector::Vec2;

mod reexports
{
    pub use glfw::window::{
        CursorMode,
        Hint as CreationHint,
        HintValue as CreationHintValue,
        InputMode,
        Key,
        KeyModifiers,
        KeyState,
    };
}

pub use reexports::*;

#[derive(Debug, Sole)]
/// Has to be dropped last since it holds the OpenGL context.
#[sole(drop_last)]
pub struct Window
{
    inner: glfw::Window,
}

impl Window
{
    /// Returns a new Window builder.
    #[must_use]
    pub fn builder() -> Builder
    {
        Builder::default()
    }

    /// Sets the value of a input mode.
    ///
    /// # Errors
    /// Returns `Err` if the input mode is unsupported on the current system.
    pub fn set_input_mode(
        &self,
        input_mode: InputMode,
        enabled: bool,
    ) -> Result<(), Error>
    {
        Ok(self.inner.set_input_mode(input_mode, enabled)?)
    }

    /// Sets the cursor mode.
    ///
    /// # Errors
    /// If a platform error occurs.
    pub fn set_cursor_mode(&self, cursor_mode: CursorMode) -> Result<(), Error>
    {
        Ok(self.inner.set_cursor_mode(cursor_mode)?)
    }

    /// Returns whether or not the window should close. Will return true when the user has
    /// attempted to close the window.
    #[must_use]
    pub fn should_close(&self) -> bool
    {
        self.inner.should_close()
    }

    /// Processes all pending events.
    ///
    /// # Errors
    /// If a platform error occurs.
    pub fn poll_events(&self) -> Result<(), Error>
    {
        Ok(self.inner.poll_events()?)
    }

    /// Swaps the front and back buffers of the window.
    ///
    /// # Errors
    /// Will return `Err` if a platform error occurs or if no OpenGL window context
    /// is present.
    pub fn swap_buffers(&self) -> Result<(), Error>
    {
        Ok(self.inner.swap_buffers()?)
    }

    /// Returns the size of the window.
    ///
    /// # Errors
    /// Will return `Err` if a platform error occurs.
    pub fn size(&self) -> Result<Dimens<u32>, Error>
    {
        let size = self.inner.size()?;

        Ok(Dimens {
            width: size.width,
            height: size.height,
        })
    }

    /// Returns the address of the specified OpenGL function, if it is supported by the
    /// current OpenGL context.
    ///
    /// # Errors
    /// Will return `Err` if a platform error occurs or if no current context has
    /// been set.
    ///
    /// # Panics
    /// Will panic if the `proc_name` argument contains a nul byte.
    pub fn get_proc_address(
        &self,
        proc_name: &str,
    ) -> Result<unsafe extern "C" fn(), Error>
    {
        let proc_name_c: Cow<CStr> = CStr::from_bytes_with_nul(proc_name.as_bytes())
            .map(Cow::Borrowed)
            .or_else(|_| CString::new(proc_name).map(Cow::Owned))
            .expect("OpenGL function name contains a nul byte");

        Ok(self.inner.get_proc_address(&proc_name_c)?)
    }

    /// Makes the OpenGL context of the window current for the calling thread.
    ///
    /// # Errors
    /// Will return `Err` if a platform error occurs or if no OpenGL context is
    /// present.
    pub fn make_context_current(&self) -> Result<(), Error>
    {
        Ok(self.inner.make_context_current()?)
    }

    /// Sets the window's framebuffer size callback.
    pub fn set_framebuffer_size_callback(&self, callback: impl Fn(Dimens<u32>) + 'static)
    {
        self.inner.set_framebuffer_size_callback(move |size| {
            callback(Dimens {
                width: size.width,
                height: size.height,
            });
        });
    }

    /// Sets the window's key size callback.
    pub fn set_key_callback(
        &self,
        callback: impl Fn(Key, i32, KeyState, KeyModifiers) + 'static,
    )
    {
        self.inner.set_key_callback(callback);
    }

    /// Sets the window's cursor position callback.
    pub fn set_cursor_pos_callback(&self, callback: impl Fn(Vec2<f64>) + 'static)
    {
        self.inner
            .set_cursor_pos_callback(move |pos| callback(Vec2 { x: pos.x, y: pos.y }));
    }

    /// Sets the window's close callback.
    pub fn set_close_callback(&self, callback: impl Fn() + 'static)
    {
        self.inner.set_close_callback(callback);
    }

    /// Sets the window's focus callback. The callback is called when the window loses or
    /// gains input focus.
    pub fn set_focus_callback(&self, callback: impl Fn(bool) + 'static)
    {
        self.inner.set_focus_callback(callback);
    }
}

/// [`Window`] builder.
#[derive(Debug, Clone, Default)]
pub struct Builder
{
    inner: glfw::WindowBuilder,
}

impl Builder
{
    #[must_use]
    pub fn creation_hint(mut self, hint: CreationHint, value: CreationHintValue) -> Self
    {
        self.inner = self.inner.hint(hint, value);

        self
    }

    /// Creates a new window.
    ///
    /// # Errors
    /// Will return `Err` if the title contains a internal nul byte or if a platform error
    /// occurs.
    pub fn create(&self, size: Dimens<u32>, title: &str) -> Result<Window, Error>
    {
        let builder = self.inner.clone().hint(
            CreationHint::OpenGLDebugContext,
            CreationHintValue::Bool(cfg!(feature = "debug")),
        );

        let window = builder.create(
            &WindowSize {
                width: size.width,
                height: size.height,
            },
            title,
        )?;

        Ok(Window { inner: window })
    }
}

#[derive(Debug)]
pub struct Extension
{
    window_builder: Builder,
    window_size: Dimens<u32>,
    window_title: String,
}

impl Extension
{
    #[must_use]
    pub fn new(window_builder: Builder) -> Self
    {
        Self { window_builder, ..Default::default() }
    }

    #[must_use]
    pub fn window_size(mut self, window_size: Dimens<u32>) -> Self
    {
        self.window_size = window_size;

        self
    }

    #[must_use]
    pub fn window_title(mut self, window_title: impl Into<String>) -> Self
    {
        self.window_title = window_title.into();

        self
    }
}

impl ecs::extension::Extension for Extension
{
    fn collect(self, mut collector: ExtensionCollector<'_>)
    {
        collector.add_system(StartEvent, initialize);
        collector.add_system(ConcludeEvent, update);

        let window = self
            .window_builder
            .create(self.window_size, &self.window_title)
            .unwrap();

        window.set_cursor_mode(CursorMode::Normal).unwrap();

        collector.add_sole(window).ok();
    }
}

impl Default for Extension
{
    fn default() -> Self
    {
        Self {
            window_builder: Builder::default(),
            window_size: Dimens { width: 1920, height: 1080 },
            window_title: String::new(),
        }
    }
}

#[derive(Debug, thiserror::Error)]
#[error(transparent)]
pub struct Error(glfw::Error);

impl From<glfw::Error> for Error
{
    fn from(err: glfw::Error) -> Self
    {
        Self(err)
    }
}

fn initialize(window: Single<Window>, actions: Actions)
{
    let actions_weak_ref = actions.to_weak_ref();

    window.set_close_callback(move || {
        let actions_weak_ref = actions_weak_ref.clone();

        let actions_ref = actions_weak_ref.access().expect("No world");

        actions_ref.to_actions().stop();
    });
}

fn update(window: Single<Window>)
{
    window
        .swap_buffers()
        .expect("Failed to swap window buffers");

    window.poll_events().expect("Failed to poll window events");
}