#include <stdio.h>
#include <stdint.h>

#define NPAGES 4

typedef enum { ST_INVALID, ST_ERASED, ST_VALID } state_t;

typedef struct {
    uint8_t data;
    state_t st;
} page_t;

static page_t blk[NPAGES];

static void dump(void) {
    printf("  ");
    for (int i = 0; i < NPAGES; i++) {
        const char *s = (blk[i].st == ST_INVALID) ? "INV" :
                        (blk[i].st == ST_ERASED) ? "ERS" : "VAL";
        printf("[%s %02X] ", s, blk[i].data);
    }
    printf("\n");
}

static void do_erase(void) {
    printf("ERASE block\n");
    for (int i = 0; i < NPAGES; i++) {
        blk[i].data = 0xFF;
        blk[i].st = ST_ERASED;
    }
    dump();
}

static void do_program(int pg, uint8_t val) {
    printf("PROGRAM page %d <- %02X\n", pg, val);
    if (pg < 0 || pg >= NPAGES || blk[pg].st != ST_ERASED) {
        printf("  ERROR: page not erasable\n");
        return;
    }
    blk[pg].data = val;
    blk[pg].st = ST_VALID;
    dump();
}

static void do_read(int pg) {
    printf("READ page %d\n", pg);
    if (pg < 0 || pg >= NPAGES || blk[pg].st != ST_VALID) {
        printf("  (not valid)\n");
        return;
    }
    printf("  data = %02X\n", blk[pg].data);
}

int main(void) {
    for (int i = 0; i < NPAGES; i++) {
        blk[i].data = 0x00;
        blk[i].st = ST_INVALID;
    }
    printf("INIT\n");
    dump();
    do_erase();
    do_program(0, 0xA5);
    do_program(0, 0x5A);
    do_program(2, 0x3C);
    do_read(0);
    do_read(1);
    do_erase();
    return 0;
}