#ifndef H_ktypes
#define H_ktypes

#define NULL ((void*) 0)

/*
 *  Error codes
 */

enum error_code {
    ENOCODE = 1,    // invalid syscall code
    EINVAL  = 2,    // invalid argument value
    ENOMEM  = 3,    // not enough memory
    ENOBUFS = 4,    // no space left in buffer
    ESRCH   = 5,    // no such process
};

/*
 *  Scheduling types
 */

enum process_status {
    PROC_DEAD       = 0,
    PROC_RDY        = 1,
    PROC_WAIT_PROC  = 2,
    PROC_WAIT_SLEEP = 3,
};

// process structure:
typedef struct ProcessControlBlock ProcessControlBlock;
struct loaded_binary;

struct ProcessControlBlock {
    int pid;
    int pc;
    int regs[31];
    int exit_code;
    // scheduling information
    enum process_status status;
    ProcessControlBlock* waiting_for_process;
    struct loaded_binary* binary;
    unsigned long long int asleep_until;
    // parent
    ProcessControlBlock* parent;
};

enum pcb_struct_registers {
    REG_RA = 0,
    REG_SP = 1,
    REG_GP = 2,
    REG_TP = 3,
    REG_T0 = 4,
    REG_T1 = 5,
    REG_t2 = 6,
    REG_FP = 7,
    REG_S0 = 7,
    REG_S1 = 8,
    REG_A0 = 9,
    REG_S2 = 17,
    REG_T3 = 27
};


/* This struct holds information about binaries which are currently loaded into
 * memory. Currently the kernel is not able to load binaries into memory, as
 * no file system layer is implemented. When the memory image is built, the 
 * list of loaded binaries is populated aswell.
 */
typedef struct loaded_binary {
    int binid;
    int entrypoint;
    void* bounds[2];
} loaded_binary;


/*
 *  Optionals
 *
 * in this kernel, an optional can hold a value or an error, but we can't use 
 * unions here because we need to be able to distinguish errors from results.
 * this is a little space inefficient, but we'll have to deal with this, or else
 * we get global errno variables.
 */

#define CreateOptionalOfType(type)\
typedef struct Optional##type { \
    enum error_code error;      \
    type value;                 \
} optional_##type

#define has_value(optional) (optional.error == 0)
#define has_error(optional) (!has_value(optional))


typedef unsigned int size_t;
typedef void* voidptr;
typedef ProcessControlBlock* pcbptr;

// create optionals for required types
CreateOptionalOfType(int);
CreateOptionalOfType(size_t);
CreateOptionalOfType(pcbptr);
CreateOptionalOfType(voidptr);

#endif