/*
 * The saved moisture levels from Moisture Detection 2, now accessed with pointers.
 * Put two readings back in order, handle a reading that never arrived, and
 * report the range of the saved data.
 */
#include <stdio.h>

#define MAX_READINGS 4

void swap_readings(int a, int b);
int *level_at(int minutes[], int levels[], int count, int minute);
int level_range(const int levels[], int count, int *lowest, int *highest);

int main(void)
{
    /* Slot i of minutes and slot i of levels are one reading. Minute 3 never arrived. */
    int minutes[MAX_READINGS] = {1, 2, 4, 5};
    int levels[MAX_READINGS] = {40, 12, 3, 7};

    int lowest = -1;
    int highest = -1;
    int status;

    /* Part A: the levels for minutes 1 and 2 were saved the wrong way round. */
    swap_readings(levels[0], levels[1]);
    printf("after swap: minute %d = %d, minute %d = %d\n",
           minutes[0], levels[0], minutes[1], levels[1]);
    if (levels[0] == 12 && levels[1] == 40) {
        printf("check A: PASS\n");
    } else {
        printf("check A: FAIL, minutes 1 and 2 are still the wrong way round\n");
    }

    /*
     * Part B: minutes 3 and 4 were swapped too. Once check A passes, remove
     * the // from the two lines below.
     */
    // swap_readings(level_at(minutes, levels, MAX_READINGS, 3),
    //               level_at(minutes, levels, MAX_READINGS, 4));
    printf("check B: the program reached Part C\n");

    /* Part C */
    status = level_range(levels, MAX_READINGS, &lowest, &highest);
    printf("range of %d readings: status %d, lowest %d, highest %d\n",
           MAX_READINGS, status, lowest, highest);
    if (status == 0 && lowest == 3 && highest == 40) {
        printf("check C1: PASS\n");
    } else {
        printf("check C1: FAIL, expected status 0, lowest 3, highest 40\n");
    }

    lowest = -1;
    highest = -1;
    status = level_range(levels, 0, &lowest, &highest);
    printf("range of 0 readings: status %d, lowest %d, highest %d\n",
           status, lowest, highest);
    if (status != 0 && lowest == -1 && highest == -1) {
        printf("check C2: PASS\n");
    } else {
        printf("check C2: FAIL, an empty log has no range: return nonzero, write nothing\n");
    }
    return 0;
}

/*
 * Given: returns the address of the level saved at minute, or NULL when
 * there is no reading for that minute.
 */
int *level_at(int minutes[], int levels[], int count, int minute)
{
    int i;

    for (i = 0; i < count; i = i + 1) {
        if (minutes[i] == minute) {
            return &levels[i];
        }
    }
    return NULL;
}

/*
 * YOUR TASK: swap the caller's two readings. As written, a and b are copies,
 * so the swap never reaches main().
 */
void swap_readings(int a, int b)
{
    int held = a;

    a = b;
    b = held;
}

/*
 * YOUR TASK: with at least one reading, write the lowest level through lowest
 * and the highest through highest, and return 0. An empty log has no lowest
 * or highest: return 1 and write nothing.
 */
int level_range(const int levels[], int count, int *lowest, int *highest)
{
    (void)levels; (void)count; (void)lowest; (void)highest;    /* delete once you use them */
    return 1;
}