#pragma once

#include "arch/MMU.h"
#include "fs/VFS.h"
#include "memory/AddressSpace.h"
#include <bits/signal.h>
#include <luna/LinkedList.h>
#include <luna/OwnedPtr.h>
#include <luna/Result.h>
#include <luna/Stack.h>
#include <luna/StaticString.h>
#include <luna/String.h>

#ifdef ARCH_X86_64
#include "arch/x86_64/CPU.h"
#else
#error "Unknown architecture."
#endif

enum class ThreadState
{
    None,
    Idle,
    Runnable,
    Sleeping,
    Waiting,
    Exited,
    Dying
};

struct OpenFileDescription : public Shareable
{
    SharedPtr<VFS::Inode> inode;
    int flags { 0 };

    OpenFileDescription(SharedPtr<VFS::Inode>, int);
    ~OpenFileDescription();
};

struct FileDescriptor
{
    SharedPtr<OpenFileDescription> description;
    usize offset { 0 };
    int flags { 0 };

    bool should_append();
    bool should_block();
    bool is_writable();
    bool is_readable();

    SharedPtr<VFS::Inode> inode()
    {
        return description->inode;
    }

    int& status_flags()
    {
        return description->flags;
    }
};

static constexpr int FD_MAX = 64;

struct Credentials
{
    u32 uid { 0 };
    u32 euid { 0 };
    u32 suid { 0 };
    u32 gid { 0 };
    u32 egid { 0 };
    u32 sgid { 0 };
};

struct Thread : public LinkedListNode<Thread>
{
    Registers regs;

    pid_t id;
    pid_t pgid { 0 };

    Credentials auth;

    u64 user_ticks_self = 0;
    u64 kernel_ticks_self = 0;
    u64 user_ticks_children = 0;
    u64 kernel_ticks_children = 0;

    u64 ticks_left;
    u64 sleep_ticks_left;

    Stack stack;
    Stack kernel_stack;

    OwnedPtr<AddressSpace> address_space;
    Option<FileDescriptor> fd_table[FD_MAX] = {};

    Result<int> allocate_fd(int min);
    Result<FileDescriptor*> resolve_fd(int fd);
    Result<SharedPtr<VFS::Inode>> resolve_atfile(int dirfd, const String& path, bool allow_empty_path,
                                                 bool follow_last_symlink,
                                                 SharedPtr<VFS::Inode>* parent_inode = nullptr);

    struct sigaction signal_handlers[NSIG];
    sigset_t signal_mask { 0 };
    sigset_t pending_signals { 0 };
    bool interrupted { false };

    FPData fp_data;

    ThreadState state = ThreadState::Runnable;

    bool is_kernel { true };
    bool has_called_exec { false };

    int status { 0 };

    mode_t umask { 0 };

    StaticString<128> name;

    String current_directory_path = {};
    SharedPtr<VFS::Inode> current_directory = {};

    Thread* parent { nullptr };
    Option<pid_t> child_being_waited_for = {};

    PageDirectory* self_directory() const
    {
        return address_space->page_directory();
    }

    PageDirectory* active_directory { nullptr };

    [[noreturn]] void exit_and_signal_parent(int status);

    bool is_idle()
    {
        return state == ThreadState::Idle;
    }

    void wake_up()
    {
        state = ThreadState::Runnable;
    }

    void init_regs_kernel();
    void init_regs_user();

    void set_arguments(u64 arg1, u64 arg2, u64 arg3, u64 arg4);

    void set_ip(u64 ip);
    u64 ip();

    void set_sp(u64 sp);
    u64 sp();

    void set_return(u64 ret);
    u64 return_register();

    void process_pending_signals(Registers* current_regs);

    bool will_invoke_signal_handler();

    bool deliver_signal(int signo, Registers* current_regs);
    void sigreturn(Registers* current_regs);

    Result<u64> push_mem_on_stack(const u8* mem, usize size);
    Result<u64> pop_mem_from_stack(u8* mem, usize size);

    void send_signal(int signo);

    static void init();
};

void switch_context(Thread* old_thread, Thread* new_thread, Registers* regs);

bool is_in_kernel(Registers* regs);

Result<Thread*> new_thread();

pid_t next_thread_id();

extern LinkedList<Thread> g_threads;