const posix = switch(@compileVar("os")) {
    Os.linux => @import("linux.zig"),
    Os.darwin, Os.macosx, Os.ios => @import("darwin.zig"),
    else => @compileError("Unsupported OS"),
};
const windows = @import("windows.zig");
const errno = @import("errno.zig");
const linking_libc = @import("build.zig").linking_libc;
const c = @import("c/index.zig");

error Unexpected;

/// Fills `buf` with random bytes. If linking against libc, this calls the
/// appropriate OS-specific library call. Otherwise it uses the zig standard
/// library implementation.
pub fn getRandomBytes(buf: []u8) -> %void {
    while (true) {
        const err = switch (@compileVar("os")) {
            Os.linux => {
                if (linking_libc) {
                    if (c.getrandom(buf.ptr, buf.len, 0) == -1) *c._errno() else 0
                } else {
                    posix.getErrno(posix.getrandom(buf.ptr, buf.len, 0))
                }
            },
            Os.darwin, Os.macosx, Os.ios => {
                if (linking_libc) {
                    if (posix.getrandom(buf.ptr, buf.len) == -1) *c._errno() else 0
                } else {
                    posix.getErrno(posix.getrandom(buf.ptr, buf.len))
                }
            },
            Os.windows => {
                var hCryptProv: windows.HCRYPTPROV = undefined;
                if (!windows.CryptAcquireContext(&hCryptProv, null, null, windows.PROV_RSA_FULL, 0)) {
                    return error.Unexpected;
                }
                defer _ = windows.CryptReleaseContext(hCryptProv, 0);

                if (!windows.CryptGenRandom(hCryptProv, windows.DWORD(buf.len), buf.ptr)) {
                    return error.Unexpected;
                }
                return;
            },
            else => @compileError("Unsupported OS"),
        };
        if (err > 0) {
            return switch (err) {
                errno.EINVAL => @unreachable(),
                errno.EFAULT => @unreachable(),
                errno.EINTR  => continue,
                else         => error.Unexpected,
            }
        }
        return;
    }
}

/// Raises a signal in the current kernel thread, ending its execution.
/// If linking against libc, this calls the abort() libc function. Otherwise
/// it uses the zig standard library implementation.
pub coldcc fn abort() -> unreachable {
    if (linking_libc) {
        c.abort();
    }
    switch (@compileVar("os")) {
        Os.linux => {
            _ = posix.raise(posix.SIGABRT);
            _ = posix.raise(posix.SIGKILL);
            while (true) {}
        },
        else => @compileError("Unsupported OS"),
    }
}