use std::{
    io, mem,
    ops::BitAnd,
    ptr, slice,
    sync::atomic::{AtomicBool, Ordering},
};

use crate::window::CursorIcon;
use winapi::{
    ctypes::wchar_t,
    shared::{
        minwindef::{BOOL, DWORD},
        windef::{HWND, POINT, RECT},
    },
    um::{winbase::lstrlenW, winuser},
};

pub fn has_flag<T>(bitset: T, flag: T) -> bool
where
    T: Copy + PartialEq + BitAnd<T, Output = T>,
{
    bitset & flag == flag
}

pub fn wchar_to_string(wchar: &[wchar_t]) -> String {
    String::from_utf16_lossy(wchar).to_string()
}

pub fn wchar_ptr_to_string(wchar: *const wchar_t) -> String {
    let len = unsafe { lstrlenW(wchar) } as usize;
    let wchar_slice = unsafe { slice::from_raw_parts(wchar, len) };
    wchar_to_string(wchar_slice)
}

pub unsafe fn status_map<T, F: FnMut(&mut T) -> BOOL>(mut fun: F) -> Option<T> {
    let mut data: T = mem::zeroed();
    if fun(&mut data) != 0 {
        Some(data)
    } else {
        None
    }
}

fn win_to_err<F: FnOnce() -> BOOL>(f: F) -> Result<(), io::Error> {
    if f() != 0 {
        Ok(())
    } else {
        Err(io::Error::last_os_error())
    }
}

pub fn get_cursor_pos() -> Option<POINT> {
    unsafe { status_map(|cursor_pos| winuser::GetCursorPos(cursor_pos)) }
}

pub fn get_window_rect(hwnd: HWND) -> Option<RECT> {
    unsafe { status_map(|rect| winuser::GetWindowRect(hwnd, rect)) }
}

pub fn get_client_rect(hwnd: HWND) -> Result<RECT, io::Error> {
    unsafe {
        let mut rect = mem::zeroed();
        let mut top_left = mem::zeroed();

        win_to_err(|| winuser::ClientToScreen(hwnd, &mut top_left))?;
        win_to_err(|| winuser::GetClientRect(hwnd, &mut rect))?;
        rect.left += top_left.x;
        rect.top += top_left.y;
        rect.right += top_left.x;
        rect.bottom += top_left.y;

        Ok(rect)
    }
}

pub fn adjust_window_rect(hwnd: HWND, rect: RECT) -> Option<RECT> {
    unsafe {
        let style = winuser::GetWindowLongW(hwnd, winuser::GWL_STYLE);
        let style_ex = winuser::GetWindowLongW(hwnd, winuser::GWL_EXSTYLE);
        adjust_window_rect_with_styles(hwnd, style as _, style_ex as _, rect)
    }
}

pub fn adjust_window_rect_with_styles(
    hwnd: HWND,
    style: DWORD,
    style_ex: DWORD,
    rect: RECT,
) -> Option<RECT> {
    unsafe {
        status_map(|r| {
            *r = rect;

            let b_menu = !winuser::GetMenu(hwnd).is_null() as BOOL;
            winuser::AdjustWindowRectEx(r, style as _, b_menu, style_ex as _)
        })
    }
}

pub fn set_cursor_hidden(hidden: bool) {
    static HIDDEN: AtomicBool = AtomicBool::new(false);
    let changed = HIDDEN.swap(hidden, Ordering::SeqCst) ^ hidden;
    if changed {
        unsafe { winuser::ShowCursor(!hidden as BOOL) };
    }
}

pub fn set_cursor_clip(rect: Option<RECT>) -> Result<(), io::Error> {
    unsafe {
        let rect_ptr = rect
            .as_ref()
            .map(|r| r as *const RECT)
            .unwrap_or(ptr::null());
        win_to_err(|| winuser::ClipCursor(rect_ptr))
    }
}

pub fn is_focused(window: HWND) -> bool {
    window == unsafe { winuser::GetActiveWindow() }
}

impl CursorIcon {
    pub(crate) fn to_windows_cursor(self) -> *const wchar_t {
        match self {
            CursorIcon::Arrow | CursorIcon::Default => winuser::IDC_ARROW,
            CursorIcon::Hand => winuser::IDC_HAND,
            CursorIcon::Crosshair => winuser::IDC_CROSS,
            CursorIcon::Text | CursorIcon::VerticalText => winuser::IDC_IBEAM,
            CursorIcon::NotAllowed | CursorIcon::NoDrop => winuser::IDC_NO,
            CursorIcon::Grab | CursorIcon::Grabbing | CursorIcon::Move | CursorIcon::AllScroll => {
                winuser::IDC_SIZEALL
            }
            CursorIcon::EResize
            | CursorIcon::WResize
            | CursorIcon::EwResize
            | CursorIcon::ColResize => winuser::IDC_SIZEWE,
            CursorIcon::NResize
            | CursorIcon::SResize
            | CursorIcon::NsResize
            | CursorIcon::RowResize => winuser::IDC_SIZENS,
            CursorIcon::NeResize | CursorIcon::SwResize | CursorIcon::NeswResize => {
                winuser::IDC_SIZENESW
            }
            CursorIcon::NwResize | CursorIcon::SeResize | CursorIcon::NwseResize => {
                winuser::IDC_SIZENWSE
            }
            CursorIcon::Wait => winuser::IDC_WAIT,
            CursorIcon::Progress => winuser::IDC_APPSTARTING,
            CursorIcon::Help => winuser::IDC_HELP,
            _ => winuser::IDC_ARROW, // use arrow for the missing cases.
        }
    }
}