#include "moisture_sensor.h"

#include <stdio.h>
#include <stdlib.h>

/* the most readings one session can send; the sensor keeps its own copy */
#define SENSOR_LIMIT 64

static int total;
static int sent;
static int minute;
static int level;
static int sent_times[SENSOR_LIMIT];
static int sent_levels[SENSOR_LIMIT];

/*
 * srand() fixes where rand() starts, so the same seed sends the same readings
 * every run on one machine. Different C libraries may still send different ones.
 * Reference: https://en.cppreference.com/w/c/numeric/random/rand
 */
void sensor_start(unsigned int seed, int readings)
{
    srand(seed);
    total = readings < 0 ? 0 : (readings > SENSOR_LIMIT ? SENSOR_LIMIT : readings);
    sent = 0;
    minute = 0;
}

static int next_level(void)
{
    int kind = rand() % 20;

    if (kind < 2) {
        return -(1 + rand() % 5);           /* a sensor fault */
    }
    if (kind < 4) {
        return 0;                           /* dry */
    }
    if (kind < 7) {
        return 101 + rand() % 20;           /* saturated */
    }
    return 1 + rand() % 100;
}

int sensor_has_next(void)
{
    if (sent >= total) {
        return 0;
    }
    minute = minute + 1 + rand() % 15;
    level = next_level();
    sent_times[sent] = minute;
    sent_levels[sent] = level;
    sent = sent + 1;
    printf("sensor: minute %d, level %d\n", minute, level);
    return 1;
}

int sensor_time(void)
{
    return minute;
}

int sensor_level(void)
{
    return level;
}

void sensor_check_log(int times[], int levels[], size_t count)
{
    size_t want = 0;
    int i;

    for (i = 0; i < sent; i++) {
        if (sent_levels[i] < 0) {
            continue;
        }
        if (want == count) {
            printf("check: FAIL, minute %d (level %d) is valid but was not stored\n",
                   sent_times[i], sent_levels[i]);
            return;
        }
        if (times[want] != sent_times[i] || levels[want] != sent_levels[i]) {
            printf("check: FAIL, slot %zu holds minute %d level %d; expected minute %d level %d\n",
                   want, times[want], levels[want], sent_times[i], sent_levels[i]);
            return;
        }
        want = want + 1;
    }
    if (want != count) {
        printf("check: FAIL, count is %zu but the sensor sent %zu valid reading(s)\n", count, want);
        return;
    }
    printf("check: PASS, all %zu valid reading(s) stored in order\n", count);
}