use std::ffi::c_int;
use std::ptr::null_mut;

use crate::util::is_main_thread;
use crate::{get_glfw_error, Error};

/// GLFW 3.x.x is supported
static SUPPORTED_GLFW_VERSION_MAJOR: c_int = 3;

/// Initializes GLFW and returns a initialization token.
///
/// # Errors
/// Will return `Err` if
/// - The current thread is not the main thread
/// - A GLFW error occurs
pub fn initialize() -> Result<Glfw, Error>
{
    if !is_main_thread() {
        return Err(Error::NotInMainThread);
    }

    let mut major: c_int = 0;

    unsafe { crate::ffi::glfwGetVersion(&mut major, null_mut(), null_mut()) };

    if major != SUPPORTED_GLFW_VERSION_MAJOR {
        return Err(Error::UnsupportedVersion);
    }

    // SAFETY: The current thread is the main thread
    let success = unsafe { crate::ffi::glfwInit() };

    if success == crate::ffi::GLFW_FALSE {
        get_glfw_error()?;
    }

    Ok(Glfw { _priv: &() })
}

/// GLFW initialization token.
#[derive(Debug)]
pub struct Glfw
{
    /// This field has two purposes
    /// - To make the struct not constructable without calling [`initialize`].
    /// - To make the struct `!Send` and `!Sync`.
    _priv: *const (),
}

impl Drop for Glfw
{
    fn drop(&mut self)
    {
        // SAFETY: The current thread cannot be any other thread than the main thread
        // since the initialize function checks it and the GLFW initialization token is
        // neither Send or Sync
        unsafe { crate::ffi::glfwTerminate() };
    }
}