//! Compatibility shims for MSVC CRT symbols required by WebView2LoaderStatic.lib.
//!
//! When statically linking the WebView2 loader on GNU/MinGW, the MSVC-compiled
//! object code references these symbols. We provide minimal implementations so
//! the linker can resolve them.

use std::sync::atomic::{AtomicI32, Ordering};

// ── MSVC Buffer Security Check (/GS) ────────────────────────────────────────
//
// MSVC's /GS flag instruments functions with stack canaries. These two symbols
// implement the canary check. The cookie value is arbitrary -- real MSVC CRT
// randomises it at startup, but for a statically-linked helper library this
// fixed sentinel is sufficient.

#[no_mangle]
pub static __security_cookie: u64 = 0x00002B992DDFA232;

#[no_mangle]
pub unsafe extern "C" fn __security_check_cookie(cookie: u64) {
    if cookie != __security_cookie {
        std::process::abort();
    }
}

// ── MSVC Thread-Safe Static Initialisation ───────────────────────────────────
//
// C++11 guarantees that function-local statics are initialised exactly once,
// even under concurrent access. MSVC implements this with an epoch counter and
// a set of helper functions. The WebView2 loader uses a few statics internally.
//
// Simplified implementation: uses an atomic spin for the guard. This is safe
// because WebView2 initialisation runs on the main thread in practice.

#[no_mangle]
pub static _Init_thread_epoch: AtomicI32 = AtomicI32::new(0);

#[no_mangle]
pub unsafe extern "C" fn _Init_thread_header(guard: *mut i32) {
    if guard.is_null() {
        return;
    }
    // Spin until we can claim the guard (-1 = uninitialized, 0 = done, 1 = in progress)
    loop {
        let val = guard.read_volatile();
        if val == 0 {
            // Already initialised -- tell caller to skip
            return;
        }
        if val == -1 {
            // Not yet initialised -- try to claim it
            guard.write_volatile(1);
            return;
        }
        // val == 1: another thread is initialising -- yield and retry
        std::thread::yield_now();
    }
}

#[no_mangle]
pub unsafe extern "C" fn _Init_thread_footer(guard: *mut i32) {
    if !guard.is_null() {
        guard.write_volatile(0); // Mark initialisation complete
        _Init_thread_epoch.fetch_add(1, Ordering::Release);
    }
}

// ── MSVC C++ Runtime Operators (mangled names) ───────────────────────────────
//
// The static library is compiled with MSVC, which uses its own C++ name mangling.
// MinGW's libstdc++ exports the same operators but with GCC/Itanium mangling,
// so the linker can't match them. We provide the MSVC-mangled versions here.

/// `std::nothrow` -- MSVC-mangled `?nothrow@std@@3Unothrow_t@1@B`
/// An empty struct constant used as a tag for nothrow `new`.
#[export_name = "?nothrow@std@@3Unothrow_t@1@B"]
pub static MSVC_STD_NOTHROW: u8 = 0;

/// `operator new(size_t, const std::nothrow_t&)` -- nothrow allocation
/// MSVC-mangled: `??2@YAPEAX_KAEBUnothrow_t@std@@@Z`
#[export_name = "??2@YAPEAX_KAEBUnothrow_t@std@@@Z"]
pub unsafe extern "C" fn msvc_operator_new_nothrow(size: usize, _nothrow: *const u8) -> *mut u8 {
    let size = if size == 0 { 1 } else { size };
    let layout = std::alloc::Layout::from_size_align_unchecked(size, 8);
    let ptr = std::alloc::alloc(layout);
    ptr // null on failure -- nothrow semantics
}

/// `operator delete(void*, size_t)` -- sized deallocation
/// MSVC-mangled: `??3@YAXPEAX_K@Z`
#[export_name = "??3@YAXPEAX_K@Z"]
pub unsafe extern "C" fn msvc_operator_delete_sized(ptr: *mut u8, size: usize) {
    if !ptr.is_null() {
        let size = if size == 0 { 1 } else { size };
        let layout = std::alloc::Layout::from_size_align_unchecked(size, 8);
        std::alloc::dealloc(ptr, layout);
    }
}