module clipboard

import time

#include <windows.h>
#flag -luser32

struct WndClassEx {
    cb_size         u32
    style           u32
    lpfn_wnd_proc   voidptr
    cb_cls_extra    int
    cb_wnd_extra    int
    h_instance      C.HINSTANCE
    h_icon          C.HICON
    h_cursor        C.HCURSOR
    hbr_background  C.HBRUSH
    lpsz_menu_name  &u16 = unsafe { nil } // LPCWSTR
    lpsz_class_name &u16 = unsafe { nil }
    h_icon_sm       &u16 = unsafe { nil }
}

fn C.RegisterClassEx(class &WndClassEx) int

fn C.GetClipboardOwner() &C.HWND

fn C.CreateWindowEx(dwExStyle i64, lpClassName &u16, lpWindowName &u16, dwStyle i64, x int, y int, nWidth int, nHeight int, hWndParent i64, hMenu voidptr, h_instance voidptr, lpParam voidptr) &C.HWND

// fn C.MultiByteToWideChar(CodePage u32, dw_flags u16, lpMultiByteStr byteptr, cbMultiByte int, lpWideCharStr u16, cchWideChar int) int
fn C.EmptyClipboard()

fn C.CloseClipboard()

fn C.GlobalAlloc(uFlag u32, size i64) C.HGLOBAL

fn C.GlobalFree(buf C.HGLOBAL)

fn C.GlobalLock(buf C.HGLOBAL) voidptr

fn C.GlobalUnlock(buf C.HGLOBAL) bool

fn C.SetClipboardData(uFormat u32, data voidptr) C.HANDLE

fn C.GetClipboardData(uFormat u32) C.HANDLE

fn C.DefWindowProc(hwnd C.HWND, msg u32, wParam C.WPARAM, lParam C.LPARAM) C.LRESULT

fn C.SetLastError(error i64)

fn C.OpenClipboard(hwnd C.HWND) int

fn C.DestroyWindow(hwnd C.HWND)

// Clipboard represents a system clipboard.
//
// System "copy" and "paste" actions utilize the clipboard for temporary storage.
[heap]
pub struct Clipboard {
    max_retries int
    retry_delay int
mut:
    hwnd C.HWND
    foo  int // TODO remove
}

fn (cb &Clipboard) get_clipboard_lock() bool {
    mut retries := cb.max_retries
    mut last_error := u32(0)
    for {
        retries--
        if retries < 0 {
            break
        }
        last_error = C.GetLastError()
        if C.OpenClipboard(cb.hwnd) > 0 {
            return true
        } else if last_error != u32(C.ERROR_ACCESS_DENIED) {
            return false
        }
        time.sleep(cb.retry_delay * time.second)
    }
    C.SetLastError(last_error)
    return false
}

fn new_clipboard() &Clipboard {
    mut cb := &Clipboard{
        max_retries: 5
        retry_delay: 5
    }
    class_name := 'clipboard'
    wndclass := WndClassEx{
        cb_size: sizeof(WndClassEx)
        lpfn_wnd_proc: voidptr(&C.DefWindowProc)
        lpsz_class_name: class_name.to_wide()
        lpsz_menu_name: 0
        h_icon_sm: 0
    }
    if C.RegisterClassEx(&wndclass) == 0 && C.GetLastError() != u32(C.ERROR_CLASS_ALREADY_EXISTS) {
        println('Failed registering class.')
    }
    hwnd := C.CreateWindowEx(0, wndclass.lpsz_class_name, wndclass.lpsz_class_name, 0,
        0, 0, 0, 0, C.HWND_MESSAGE, C.NULL, C.NULL, C.NULL)
    if hwnd == C.NULL {
        println('Error creating window!')
    }
    cb.hwnd = hwnd
    return cb
}

// check_availability returns true if the clipboard is ready to be used.
pub fn (cb &Clipboard) check_availability() bool {
    return cb.hwnd != C.HWND(C.NULL)
}

// has_ownership returns true if the contents of
// the clipboard were created by this clipboard instance.
pub fn (cb &Clipboard) has_ownership() bool {
    return C.GetClipboardOwner() == cb.hwnd
}

// clear empties the clipboard contents.
pub fn (mut cb Clipboard) clear() {
    if !cb.get_clipboard_lock() {
        return
    }
    C.EmptyClipboard()
    C.CloseClipboard()
    cb.foo = 0
}

// free releases all memory associated with the clipboard
// instance.
pub fn (mut cb Clipboard) free() {
    C.DestroyWindow(cb.hwnd)
    cb.foo = 0
}

// the string.to_wide doesn't work with SetClipboardData, don't know why
fn to_wide(text string) C.HGLOBAL {
    len_required := C.MultiByteToWideChar(C.CP_UTF8, C.MB_ERR_INVALID_CHARS, text.str,
        text.len + 1, C.NULL, 0)
    buf := C.GlobalAlloc(C.GMEM_MOVEABLE, i64(sizeof(u16)) * len_required)
    if buf != C.HGLOBAL(C.NULL) {
        mut locked := &u16(C.GlobalLock(buf))
        C.MultiByteToWideChar(C.CP_UTF8, C.MB_ERR_INVALID_CHARS, text.str, text.len + 1,
            locked, len_required)
        unsafe {
            locked[len_required - 1] = u16(0)
        }
        C.GlobalUnlock(buf)
    }
    return buf
}

// set_text transfers `text` to the system clipboard.
// This is often associated with a *copy* action (`Ctrl` + `C`).
pub fn (mut cb Clipboard) set_text(text string) bool {
    cb.foo = 0
    buf := to_wide(text)
    if !cb.get_clipboard_lock() {
        C.GlobalFree(buf)
        return false
    } else {
        // EmptyClipboard must be called to properly update clipboard ownership
        C.EmptyClipboard()
        if C.SetClipboardData(C.CF_UNICODETEXT, buf) == C.HANDLE(C.NULL) {
            println('SetClipboardData: Failed.')
            C.CloseClipboard()
            C.GlobalFree(buf)
            return false
        }
    }
    // CloseClipboard appears to change the sequence number...
    C.CloseClipboard()
    return true
}

// get_text retrieves the contents of the system clipboard
// as a `string`.
// This is often associated with a *paste* action (`Ctrl` + `V`).
pub fn (mut cb Clipboard) get_text() string {
    cb.foo = 0
    if !cb.get_clipboard_lock() {
        return ''
    }
    h_data := C.GetClipboardData(C.CF_UNICODETEXT)
    if h_data == C.HANDLE(C.NULL) {
        C.CloseClipboard()
        return ''
    }
    str := unsafe { string_from_wide(&u16(C.GlobalLock(C.HGLOBAL(h_data)))) }
    C.GlobalUnlock(C.HGLOBAL(h_data))
    return str
}

// new_primary returns a new X11 `PRIMARY` type `Clipboard` instance allocated on the heap.
// Please note: new_primary only works on X11 based systems.
pub fn new_primary() &Clipboard {
    panic('Primary clipboard is not supported on non-Linux systems.')
}