use ContextError;
use CreationError;
use CreationError::OsError;
use GlAttributes;
use GlContext;
use PixelFormatRequirements;
use libc;
use std::ptr;

use core_foundation::base::TCFType;
use core_foundation::string::CFString;
use core_foundation::bundle::{CFBundleGetBundleWithIdentifier, CFBundleGetFunctionPointerForName};
use cocoa::base::{id, nil};
use cocoa::appkit::*;
use PixelFormat;

mod gl {
    include!(concat!(env!("OUT_DIR"), "/gl_bindings.rs"));
}

static mut framebuffer: u32 = 0;
static mut texture: u32 = 0;

pub struct HeadlessContext {
    width: u32,
    height: u32,
    context: id,
}

impl HeadlessContext {
    pub fn new((width, height): (u32, u32), pf_reqs: &PixelFormatRequirements,
               opengl: &GlAttributes<&HeadlessContext>) -> Result<HeadlessContext, CreationError>
    {
        let context = unsafe {
            let attributes = [
                NSOpenGLPFAAccelerated as u32,
                NSOpenGLPFAAllowOfflineRenderers as u32,
                NSOpenGLPFADoubleBuffer as u32,
                0
            ];

            let pixelformat = NSOpenGLPixelFormat::alloc(nil).initWithAttributes_(&attributes);
            if pixelformat == nil {
                return Err(OsError(format!("Could not create the pixel format")));
            }
            let context = NSOpenGLContext::alloc(nil).initWithFormat_shareContext_(pixelformat, nil);
            if context == nil {
                return Err(OsError(format!("Could not create the rendering context")));
            }
            context
        };

        let headless = HeadlessContext {
            width: width,
            height: height,
            context: context,
        };

        // Load the function pointers as we need them to create the FBO
        gl::load_with(|s| headless.get_proc_address(s) as *const libc::c_void);

        Ok(headless)
    }
}

impl GlContext for HeadlessContext {
    unsafe fn make_current(&self) -> Result<(), ContextError> {
        self.context.makeCurrentContext();

        gl::GenFramebuffersEXT(1, &mut framebuffer);
        gl::BindFramebufferEXT(gl::FRAMEBUFFER_EXT, framebuffer);
        gl::GenTextures(1, &mut texture);
        gl::BindTexture(gl::TEXTURE_2D, texture);
        gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_MAG_FILTER, gl::LINEAR as i32);
        gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_MIN_FILTER, gl::LINEAR as i32);
        gl::TexImage2D(gl::TEXTURE_2D, 0, gl::RGBA8 as i32, self.width as i32, self.height as i32,
                       0, gl::RGBA, gl::UNSIGNED_BYTE, ptr::null());
        gl::FramebufferTexture2DEXT(gl::FRAMEBUFFER_EXT, gl::COLOR_ATTACHMENT0_EXT,
                                    gl::TEXTURE_2D, texture, 0);
        let status = gl::CheckFramebufferStatusEXT(gl::FRAMEBUFFER_EXT);
        if status != gl::FRAMEBUFFER_COMPLETE_EXT {
            panic!("Error while creating the framebuffer");
        }

        Ok(())
    }

    fn is_current(&self) -> bool {
        unimplemented!()
    }

    fn get_proc_address(&self, _addr: &str) -> *const libc::c_void {
        let symbol_name: CFString = _addr.parse().unwrap();
        let framework_name: CFString = "com.apple.opengl".parse().unwrap();
        let framework = unsafe {
            CFBundleGetBundleWithIdentifier(framework_name.as_concrete_TypeRef())
        };
        let symbol = unsafe {
            CFBundleGetFunctionPointerForName(framework, symbol_name.as_concrete_TypeRef())
        };
        symbol as *const libc::c_void
    }

    fn swap_buffers(&self) -> Result<(), ContextError> {
        Ok(())
    }

    fn get_api(&self) -> ::Api {
        ::Api::OpenGl
    }

    fn get_pixel_format(&self) -> PixelFormat {
        unimplemented!();
    }
}

unsafe impl Send for HeadlessContext {}
unsafe impl Sync for HeadlessContext {}

impl Drop for HeadlessContext {
    fn drop(&mut self) {
        unsafe {
            gl::DeleteTextures(1, &texture);
            gl::DeleteFramebuffersEXT(1, &framebuffer);
        }
    }
}