#include "rpc/platform/instance_lock.hpp"

#include <cstddef>
#include <cstring>

#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>

#include "util/crypto.hpp"

namespace velox::daemon::rpc::platform {

int acquire_instance_lock(const std::string& runtime_dir) {
    const int fd = ::socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
    if (fd < 0) return -1;

    // Truncated to 16 hex chars (64 bits): a collision would need two distinct runtime
    // dirs to hash together, which is not a security boundary here — the socket itself is
    // still 0600 same-UID-checked; this is only "don't let two daemons stomp each other".
    const std::string name =
        "velox-daemon-" + velox::daemon::crypto::sha256_hex(runtime_dir).substr(0, 16);
    sockaddr_un addr{};
    addr.sun_family = AF_UNIX;
    // Leading NUL selects the abstract namespace; the name follows, not NUL-terminated.
    addr.sun_path[0] = '\0';
    std::memcpy(addr.sun_path + 1, name.c_str(), name.size());
    const socklen_t len =
        static_cast<socklen_t>(offsetof(sockaddr_un, sun_path) + 1 + name.size());

    if (::bind(fd, reinterpret_cast<sockaddr*>(&addr), len) != 0) {
        ::close(fd);
        return -1;
    }
    return fd;
}

}  // namespace velox::daemon::rpc::platform