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

#include "puzzle_input.h"
#include "day.h"

#define STATES_MAX_LEN 500
#define FISH_DAYS 9

uint8_t states_g[STATES_MAX_LEN];


typedef struct {
    uint64_t spawn_count[FISH_DAYS];
    uint8_t day_ndx;
} fish_buffer_t;

void insert_fish_at_ndx(fish_buffer_t * buff, uint8_t day_ndx, uint64_t count) {
    uint8_t norm_ndx = (buff->day_ndx + day_ndx) % FISH_DAYS;
    buff->spawn_count[norm_ndx] += count;
}

uint64_t fish_today(fish_buffer_t * buff) {
    return buff->spawn_count[buff->day_ndx];
}

void inc_day(fish_buffer_t * buff) {
    buff->day_ndx = (buff->day_ndx + 1) % FISH_DAYS;
}

int day_6() {
    parse_ret_t res;
    uint16_t len;
    uint16_t day = 0;
    uint64_t fish_count;
    fish_buffer_t fish_buffer = {0};

    res = read_input_split_on("../inputs/day_6.txt", (void *)states_g, 500, parse_byte_from_buff, &len, ',');

    if (res != PARSER_OK) {
        printf("Unable to parse input data: %d", res);
        return -1;
    }

    for (int initial_ndx = 0; initial_ndx < len; initial_ndx++) {
        fish_buffer.spawn_count[states_g[initial_ndx]]++;
    }

    fish_count = len;

    while (day < 256) {
        uint64_t spawns_today = fish_today(&fish_buffer);
        inc_day(&fish_buffer);
        insert_fish_at_ndx(&fish_buffer, 6, spawns_today);

        fish_count += spawns_today;

        day++;

        if (day == 80) {
            printf("PART 1: Fish count: %lu\n", fish_count);
        }
    }

    printf("PART 2: Fish count: %lu\n", fish_count);
    return 0;
}