use std::cell::RefCell;
use std::ffi::{c_int, CStr, CString};
use std::panic::catch_unwind;
use std::ptr::null_mut;

use crate::init::{initialize, Glfw};
use crate::{get_glfw_error, Error};

pub struct Window
{
    _init: Glfw,
    handle: *mut crate::ffi::GLFWwindow,
}

impl Window
{
    /// Creates a new window.
    ///
    /// # Errors
    /// Will return `Err` if
    /// - The title contains an internal nul byte
    /// - A GLFW error occurs
    pub fn create(size: &Size, title: &str) -> Result<Self, Error>
    {
        let init = initialize()?;

        let c_title =
            CString::new(title).map_err(|_| Error::InternalNulByteInWindowTitle)?;

        // SAFETY: The initialize function makes sure the current thread is the main
        // thread
        let handle = unsafe {
            #[allow(clippy::cast_possible_wrap)]
            crate::ffi::glfwCreateWindow(
                size.width as i32,
                size.height as i32,
                c_title.as_ptr(),
                null_mut(),
                null_mut(),
            )
        };

        get_glfw_error()?;

        Ok(Self {
            _init: init,
            handle,
        })
    }

    /// Makes the context of the window current for the calling thread.
    ///
    /// # Errors
    /// Will return `Err` if a GLFW platform error occurs or if no OpenGL context is
    /// present.
    pub fn make_context_current(&self) -> Result<(), Error>
    {
        unsafe { crate::ffi::glfwMakeContextCurrent(self.handle) };

        get_glfw_error()?;

        Ok(())
    }

    /// Returns the address of the specified OpenGL function, if it is supported by the
    /// current context.
    ///
    /// # Errors
    /// Will return `Err` if a GLFW platform error occurs or if no current context has
    /// been set.
    pub fn get_proc_address(
        &self,
        proc_name: &CStr,
    ) -> Result<unsafe extern "C" fn(), Error>
    {
        let proc_addr = unsafe { crate::ffi::glfwGetProcAddress(proc_name.as_ptr()) };

        get_glfw_error()?;

        // SAFETY: Is only None when a error has occured and that case is handled above
        Ok(unsafe { proc_addr.unwrap_unchecked() })
    }

    /// Processes all pending events.
    ///
    /// # Errors
    /// Will return `Err` if a GLFW platform error occurs.
    pub fn poll_events(&self) -> Result<(), Error>
    {
        // SAFETY: The initialize function (called when the window is created) makes sure
        // the current thread is the main thread
        unsafe { crate::ffi::glfwPollEvents() };

        get_glfw_error()?;

        Ok(())
    }

    /// Swaps the front and back buffers of the window.
    ///
    /// # Errors
    /// Will return `Err` if a GLFW platform error occurs or if no OpenGL window context
    /// is present.
    pub fn swap_buffers(&self) -> Result<(), Error>
    {
        unsafe {
            crate::ffi::glfwSwapBuffers(self.handle);
        };

        get_glfw_error()?;

        Ok(())
    }

    /// Returns whether or not the window should close.
    #[must_use]
    pub fn should_close(&self) -> bool
    {
        let should_close = unsafe { crate::ffi::glfwWindowShouldClose(self.handle) };

        should_close == crate::ffi::GLFW_TRUE
    }

    /// Retrieves the size of the window.
    ///
    /// # Errors
    /// Will return `Err` if a GLFW platform error occurs.
    pub fn size(&self) -> Result<Size, Error>
    {
        let mut width = 0;
        let mut height = 0;

        // SAFETY: The initialize function (called when the window is created) makes sure
        // the current thread is the main thread
        unsafe { crate::ffi::glfwGetWindowSize(self.handle, &mut width, &mut height) };

        get_glfw_error()?;

        #[allow(clippy::cast_sign_loss)]
        Ok(Size {
            width: width as u32,
            height: height as u32,
        })
    }

    pub fn set_framebuffer_size_callback(&self, callback: impl Fn(Size) + 'static)
    {
        FRAMEBUFFER_SIZE_CB.with_borrow_mut(|framebuffer_size_cb| {
            *framebuffer_size_cb = Some(Box::new(callback));
        });

        // SAFETY: The initialize function (called when the window is created) makes sure
        // the current thread is the main thread
        unsafe {
            crate::ffi::glfwSetFramebufferSizeCallback(
                self.handle,
                Some(framebuffer_size_callback),
            );
        }
    }
}

/// Window size.
pub struct Size
{
    pub width: u32,
    pub height: u32,
}

type FramebufferSizeCb = Box<dyn Fn(Size)>;

thread_local! {
static FRAMEBUFFER_SIZE_CB: RefCell<Option<FramebufferSizeCb>> = RefCell::new(None);
}

extern "C" fn framebuffer_size_callback(
    _window: *mut crate::ffi::GLFWwindow,
    c_width: c_int,
    c_height: c_int,
)
{
    // Width and height can't possibly have their sign bit set
    let width = u32::from_le_bytes(c_width.to_le_bytes());
    let height = u32::from_le_bytes(c_height.to_le_bytes());

    // Unwinds are catched because unwinding from Rust code into foreign code is UB.
    let res = catch_unwind(|| {
        FRAMEBUFFER_SIZE_CB
            .try_with(|framebuffer_size_cb| {
                if let Some(cb) = framebuffer_size_cb.borrow().as_deref() {
                    cb(Size { width, height });
                }
            })
            .ok();
    });

    if res.is_err() {
        println!("ERROR: Panic in framebuffer size callback");
    }
}