#ifndef MERCURY_KERNEL_APPLICATION_HPP
#define MERCURY_KERNEL_APPLICATION_HPP

#include <mercury/kernel/vfile.hpp>
#include <cstdint>

namespace mercury::kernel::application {

  enum class app_state {
    running,
    paused,
    zombie
  };

  struct app_instance {

    app_state state;

    uint64_t *p4;
    uint64_t *p3;
    uint64_t *p2;

    bool *p2es_to_free_on_exit;

    uint64_t p4_paddr;

    //set to 0 if none
    uint64_t framebuffer_vaddr;

    //only valid if state is zombie
    int exit_code;

    //only valid if state is paused
    struct {
      uint64_t rip;
      uint64_t rsp;
      //TODO: etc.
    } saved_regs;

    app_instance();
    ~app_instance();

    //2MiB page. vaddr and paddr must be aligned, and vaddr in valid range.
    void map_page(uint64_t vaddr, uint64_t paddr,
      bool write, bool execute, bool free_pram_on_exit);

    //2MiB pages. returns start of first page.
    uint64_t get_free_vaddr_pages(uint64_t count);

    void create_stack();

    void set_instruction_pointer(uint64_t vaddr);

    //2MiB pages; only lower half.
    uint64_t count_mapped_vram_pages();

  };

  extern app_instance *running_app;

  enum class create_app_result {
    success,
    device_error,
    app_corrupt,
    fs_corrupt
  };

  create_app_result create_app(const vfile::vfile &file, app_instance *&out);

}

#endif