#ifndef DCPU16_H_3XXIQQG2
#define DCPU16_H_3XXIQQG2

#include <stdlib.h>

/* the target system's concept of a word */
typedef unsigned short DCPU16_WORD;

/* how much ram the system has */
#define DCPU16_RAM 0x10000
#define DCPU16_INTERRUPT_QUEUE_SIZE 256

extern const char * const dcpu16_reg_names[];
enum dcpu16_register_indexes {
    DCPU16_REG_A = 0,
    DCPU16_REG_B,
    DCPU16_REG_C,
    DCPU16_REG_X,
    DCPU16_REG_Y,
    DCPU16_REG_Z,
    DCPU16_REG_I,
    DCPU16_REG_J,
    DCPU16_REG_PC,
    DCPU16_REG_SP,
    DCPU16_REG_EX,
    DCPU16_REG_IA,
    DCPU16_REG__NUM
};

/* we call this sort of function for emitting a readable message */
typedef void (dcpu16_msg_cb_t)(unsigned int, char *, ...);

/* we may emit any of these types of messages */
enum dcpu16_msg_type {
    DCPU16_MSG_ERROR = 0,
    DCPU16_MSG_INFO,
    DCPU16_MSG_DEBUG
};

/* update the default message handler */
dcpu16_msg_cb_t *dcpu16_msg_set_default(dcpu16_msg_cb_t *);

/* hardware devices may want to call this directly, without a core context */
extern dcpu16_msg_cb_t *dcpu16_msg_;

/* a self-contained dcpu16 core */
struct dcpu16 {
    dcpu16_msg_cb_t *msg_cb_;           /* callback to invoke for messages */

    struct dcpu16_acct_cb *cb_table_;   /* list of callbacks to invoke for certain events */
    size_t cb_table_entries_;           /* callback list maintenance */
    size_t cb_table_allocated_;         /* callback list maintenance */

    struct dcpu16_hw *hw_table_;        /* list of hardware attached to system */
    size_t hw_table_entries_;           /* hardware list maintenance */
    size_t hw_table_allocated_;         /* hardware list maintenance */

    unsigned long long cycle_;          /* number of cycles this core has executed */
    unsigned int skip_ : 1;             /* skip execution of next instruction */
    unsigned int interrupts_deferred_ : 1; /* queue software interrupts */
    unsigned int on_fire_ : 1;          /* cpu is on fire */
    DCPU16_WORD reg_work_[2];           /* work registers for holding literal values while decoding instructions */
    DCPU16_WORD interrupts_[DCPU16_INTERRUPT_QUEUE_SIZE];    /* fifo of pending interrupts */
    size_t interrupts_head_;            /* interrupt queue maintenance */
    size_t interrupts_tail_;            /* interrupt queue maintenance */

    DCPU16_WORD reg[DCPU16_REG__NUM];   /* system registers, a b c x y z i j */
    DCPU16_WORD ram[DCPU16_RAM];        /* memory */
};

/* these are used for accounting/watchpointing/modules/&c */
typedef unsigned int dcpu16_acct_event;
typedef void (dcpu16_ev_cb_t)(struct dcpu16 *, dcpu16_acct_event, DCPU16_WORD, void *);
#define DCPU16_ACCT_EV_CYCLE    (1<<1)
#define DCPU16_ACCT_EV_READ     (1<<2)
#define DCPU16_ACCT_EV_WRITE    (1<<3)
#define DCPU16_ACCT_EV_REG_READ (1<<4)
#define DCPU16_ACCT_EV_REG_WRITE (1<<5)
#define DCPU16_ACCT_EV_NOP      (1<<6)
#define DCPU16_ACCT_EV_RESET    (1<<7)
struct dcpu16_acct_cb {
    dcpu16_ev_cb_t *fn; /* call this */
    void *data;         /* also mention this */
    dcpu16_acct_event mask; /* when (mask & event) is true and */
    DCPU16_WORD addr_l, /* addr is this or higher and */
                addr_h; /* addr is this or lower */
};

typedef void (dcpu16_hw_signal_t)(struct dcpu16 *, struct dcpu16_hw *);
/* this structure defines a specific instance of this type of 'hardware' */
struct dcpu16_hw {
    struct dcpu16 *vm;              /* which system do I belong to */
    struct dcpu16_hw_module *mod;   /* whence I came */
    void *data;                     /* per-instance data */
};

/* human-readable text describing hw module control operations, for convenience's sake */
struct dcpu16_hw_ctl_cmd {
    char *command;
    char *data_in_type;
    char *data_out_type;
    char *description;
};

typedef int (dcpu16_hw_data_init_t)(struct dcpu16_hw *, void *);
typedef void (dcpu16_hw_data_free_t)(struct dcpu16_hw *);
typedef int (dcpu16_hw_ctl_t)(struct dcpu16_hw *, const char *, void *, void *);
struct dcpu16_hw_module {
    char *name_;                /* dymo label on front panel */

    DCPU16_WORD id_l;
    DCPU16_WORD id_h;
    DCPU16_WORD ver;
    DCPU16_WORD mfg_l;
    DCPU16_WORD mfg_h;

    dcpu16_hw_signal_t *hwi;    /* hardware interrupt handler */
    dcpu16_hw_signal_t *cycle;  /* cycle tick handler */
    dcpu16_hw_signal_t *reset;  /* reset handler */

    dcpu16_hw_data_init_t *data_init;   /* how to allocate a dcpu16_hw instance's data */
    dcpu16_hw_data_free_t *data_free;
    dcpu16_hw_ctl_t *ctl;
    struct dcpu16_hw_ctl_cmd *ctl_cmd;
};

/* update a message handler */
dcpu16_msg_cb_t *dcpu16_msg_set(struct dcpu16 *, dcpu16_msg_cb_t *);

/* instantiate a new core */
struct dcpu16 *dcpu16_new(void);

/* reset a core to initial state */
void dcpu16_reset(struct dcpu16 *);

/* print words in buf as asm */
DCPU16_WORD dcpu16_mnemonify_buf(DCPU16_WORD *);

/* print the instruction at the specified address, returns number of words consumed in decoding */
DCPU16_WORD dcpu16_disassemble_print(struct dcpu16 *, DCPU16_WORD);

/* create and delete 'hardware' objects */
struct dcpu16_hw *dcpu16_hw_new(struct dcpu16 *, struct dcpu16_hw_module *, void *);
void dcpu16_hw_del(struct dcpu16_hw **);

/* set options on hardware objects */
int dcpu16_hw_ctl(struct dcpu16_hw *, const char *, void *, void *);

/* register new 'hardware' device with system */
int dcpu16_hw_attach(struct dcpu16 *, struct dcpu16_hw *);

/* register a callback for an accounting event */
int dcpu16_acct_add(struct dcpu16 *, dcpu16_acct_event, dcpu16_ev_cb_t *, DCPU16_WORD, DCPU16_WORD, void *);

/* execute the next instruction */
void dcpu16_step(struct dcpu16 *);

/* release a core */
void dcpu16_delete(struct dcpu16 **);

/* signal hardware interrupt */
int dcpu16_interrupt(struct dcpu16 *, DCPU16_WORD);

/* consume a cycle */
void dcpu16_cycle_inc(struct dcpu16 *, unsigned int);

#endif /* DCPU16_H_3XXIQQG2 */