#pragma once
#include <sys/types.h>

#include <cstdint>
#include <filesystem>
#include <memory>
#include <string>

namespace doos {

struct Limits {
    std::uint64_t memoryBytes = 0;  // 0 = not limited
    std::uint32_t pids = 0;
    std::uint32_t milliCpus = 0;    // 0 = all cores
};

// cgroup v2 subtree of one running container under the cgroup delegated to the user's systemd manager:
//
//   doos/<name>/        limits live here (memory.max, pids.max, cpu.max), no processes
//     main/             the container's init and everything it starts; frozen when the size cap is hit
//     shell/            processes started by later `doos attach` calls; never frozen (rescue path), same limits
//
// Best effort: create() returns null when delegation is absent, and the caller must say why.
class Cgroup {
public:
    static std::unique_ptr<Cgroup> create(const std::string& name, const Limits& limits, std::string& whyNot,
                                          std::string& notEnforced);
    // Existing group of a running container, for joiners. Null when none.
    static std::unique_ptr<Cgroup> open(const std::string& name);
    ~Cgroup();
    Cgroup(const Cgroup&) = delete;
    Cgroup& operator=(const Cgroup&) = delete;

    void addMain(pid_t pid) const;
    void addShell(pid_t pid) const;
    void freeze(bool on) const;
    bool frozen() const { return frozen_; }
    // Number of OOM kills and of fork failures at the pids limit since creation.
    std::uint64_t oomKills() const;
    std::uint64_t pidFailures() const;

private:
    Cgroup(std::filesystem::path dir, bool owner) : dir_(std::move(dir)), owner_(owner) {}
    static std::filesystem::path base(std::string& whyNot);
    std::uint64_t counter(const char* file, const char* key) const;
    std::filesystem::path dir_;
    bool owner_;
    mutable bool frozen_ = false;
};

}  // namespace doos