#include "rpc/runtime_dir.hpp"

#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#include <cerrno>
#include <cstdlib>
#include <string>

namespace velox::daemon::rpc {

namespace {

std::error_code errc(int e) { return std::error_code(e, std::generic_category()); }

// Ensure `dir` exists as a directory we own with mode 0700. Creates it if absent.
std::error_code ensure_private_dir(const std::string& dir) {
    if (::mkdir(dir.c_str(), 0700) != 0 && errno != EEXIST) return errc(errno);

    struct stat st{};
    if (::lstat(dir.c_str(), &st) != 0) return errc(errno);
    if (!S_ISDIR(st.st_mode)) return errc(ENOTDIR);
    if (st.st_uid != ::geteuid()) return errc(EPERM);

    // Tighten if a prior run (or umask) left it looser. Group/other bits must be clear:
    // the socket is 0600 but a traversable parent still lets another user stat it.
    if ((st.st_mode & 077) != 0 && ::chmod(dir.c_str(), 0700) != 0) return errc(errno);
    return {};
}

}  // namespace

std::error_code resolve_runtime_dir(RuntimeDir& out) {
    std::string base;
    if (const char* xdg = ::getenv("XDG_RUNTIME_DIR"); xdg != nullptr && xdg[0] != '\0') {
        base = xdg;
    } else {
        base = "/run/user/" + std::to_string(::geteuid());
        struct stat st{};
        if (::stat(base.c_str(), &st) != 0 || !S_ISDIR(st.st_mode)) {
            // No XDG_RUNTIME_DIR and no /run/user/<uid>: we refuse rather than pick an
            // insecure fallback. The caller surfaces this as "cannot start".
            return errc(ENOENT);
        }
    }
    if (!base.empty() && base.back() == '/') base.pop_back();

    const std::string dir = base + "/velox";
    if (auto ec = ensure_private_dir(dir)) return ec;

    out.path = dir;
    return {};
}

std::error_code resolve_data_dir(std::string& out) {
    std::string base;
    if (const char* xdg = ::getenv("XDG_DATA_HOME"); xdg != nullptr && xdg[0] != '\0') {
        base = xdg;
    } else if (const char* home = ::getenv("HOME"); home != nullptr && home[0] != '\0') {
        base = std::string(home) + "/.local/share";
    } else {
        return errc(ENOENT);
    }
    if (!base.empty() && base.back() == '/') base.pop_back();

    // Create the XDG base components leniently, then the velox dir with a strict check.
    ::mkdir(base.c_str(), 0700);
    const std::string dir = base + "/velox";
    if (auto ec = ensure_private_dir(dir)) return ec;

    out = dir;
    return {};
}

}  // namespace velox::daemon::rpc