#include "vmsim.h"

/** pageFault **/
/*  Process page fault */
int pageFault(unsigned logicalAddress) {
    int pageNumber = logicalAddress >> 10;
    static int clockHand = 0; // always points to one index past last frame referenced
    int i;

    /* my implementation */

    /* placement round */
    for(i=0; i< numPageFrames; i++) {
        /* if we've reached a page not in memory, use that index */
        if(pageTable[i].valid == 0) {
            pageTable[i].vmPage = pageNumber;
            pageTable[i].valid = 1;
            pageTable[i].referenced = 0;
            pageTable[i].modified = 0;
            clockHand = i+1;
            if(clockHand >= numPageFrames) clockHand = 0;
            return (0);
        }
    }


    /* Replacement Loop, because placement failed */
    while(1) {
        /* if current spot is not referenced, replace it */
        if(pageTable[clockHand].referenced == 0) {
            pageTable[clockHand].vmPage = pageNumber;
            pageTable[clockHand].valid = 1;
            pageTable[clockHand].referenced = 0;
            if(pageTable[clockHand].modified == 1) {
                pageTable[clockHand].modified = 0;
                clockHand++; /* increment clock pointer for next time */
                if(clockHand >= numPageFrames) clockHand = 0;
                return (2);
            } else {
                clockHand++; /* increment clock pointer for next time */
                if(clockHand >= numPageFrames) clockHand = 0;
                return (1);
            }
        } else { /* if spot has already been referenced, set it to unreferenced and move on */
            pageTable[clockHand].referenced = 0;
        }
        /* if we failed for this index, increment clockHand, if over threshold, reset to 0 */
        clockHand++;
        if(clockHand >= numPageFrames) clockHand = 0;
    }
    printf("Oh no! I don't think I'm supposed to be here! ");
}