#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <stdint.h>

// too low 425996

// #define FILENAME "sample.txt"
#define FILENAME "input.txt"

#define BOARD_MAX 256
#define NUMBERS_MAX 2048

#define MIN(a,b) (((int)(a)<(int)(b))?(a):(b))
#define MAX(a,b) (((int)(a)>(int)(b))?(a):(b))

typedef struct {
    int number;
    
    size_t x;
    size_t y;
    size_t len;
} num;

typedef struct {
    size_t x;
    size_t y;

    uint64_t p;
    size_t nrefs;
} gear;

void num_print(num number);
int num_near_symbol(num number);

void gear_print(gear g);
void gear_add(size_t x, size_t y, size_t number);

static num numbers[NUMBERS_MAX];
static size_t nnumbers;

static gear gears[NUMBERS_MAX];
static size_t ngears;

static char board[BOARD_MAX][BOARD_MAX];
static size_t width;
static size_t height;

int main(void)
{
    FILE *fp = fopen(FILENAME, "r");
    if(!fp) {
        perror("fopen: failed");
        return 1;
    }

    char line[256];
    
    fgets(line, sizeof(line), fp);
    width = strlen(line) - 1; // minus \n

    fseek(fp, 0, SEEK_SET);

    // load the numbers
    while(fgets(line, sizeof(line), fp)) {
        // copy the board
        memcpy(board[height], line, width);

        char numstr[16] = {0};
        size_t len = 0;
        for(size_t i = 0; i < width; i++) {          
            while(isdigit(board[height][i])){
                numstr[len] = board[height][i];
                i++; len++;
            }
            
            if(numstr[0] != 0) {
                numbers[nnumbers++] = (num){ atoi(numstr), i-len, height, len };
                memset(numstr, 0, sizeof(numstr));
                len = 0;
            }
        }
        
        height++;
    }
    
    fclose(fp);
    
    uint64_t sum = 0;
    for(size_t i = 0; i < nnumbers; i++) {
        if(num_near_symbol(numbers[i])) {
            sum += numbers[i].number;
        }
    }

    printf("Part 1: %lu\n", sum);

    sum = 0;
    for(size_t i = 0; i < ngears; i++) {
        if(gears[i].nrefs == 2) sum += gears[i].p;
    }

    printf("Part 2: %lu\n", sum);
    return 0;
}

int num_near_symbol(num number)
{
    for(size_t i = MAX(number.y - 1, 0); i <= MIN(number.y + 1, height-1); i++)
        for(size_t j = MAX(number.x - 1, 0); j <= MIN(number.x + number.len, width-1); j++) {
            if((i == number.y) && ((j >= number.x) && (j < number.x + number.len))) continue;
               
            if(board[i][j] == '*') gear_add(j, i, number.number);
            if(board[i][j] != '.') return 1;
        }
    return 0;
}

void num_print(num number)
{
    printf("%d: %ld %ld %ld\n", number.number, number.len, number.x, number.y);
}

void gear_print(gear g)
{
    printf("%ld %ld %ld %ld\n", g.x, g.y, g.nrefs, g.p);
}

void gear_add(size_t x, size_t y, size_t number)
{
    for(size_t i = ngears - 1; i < ngears; i--)
        if((gears[i].x == x) && (gears[i].y == y)) {
            gears[i].nrefs++;
            gears[i].p *= number;
            return;
        }

    gears[ngears].x = x;
    gears[ngears].y = y;
    gears[ngears].p = number;
    gears[ngears].nrefs = 1;
    ngears++;
}