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

char input[] = {
#embed "day1_input"
};

char test[] = {
#embed "day1_test"
};

unsigned grabnum(const char *s, const char **end) {
    unsigned r = 0;
    for (; *s >= '0' && *s <= '9'; s++)
        r = r * 10 + (*s - '0');
    *end = s;
    return r;
}

unsigned long do_part1(size_t src_len, const char src[src_len]) {
    const char *s = src;
    unsigned long count = 0;
    unsigned long pos = 1'000'000'000'050;
    while (s < &src[src_len]) {
        const char *ns = s + 1;
        unsigned r = grabnum(ns, &ns);
        if (*s == 'L') {
            pos -= r;
        } else {
            pos += r;
        }
        count += pos % 100 == 0;
        s = ns + 1;
    }
    return count;
}

unsigned do_part2(size_t src_len, const char src[src_len]) {
    const char *s = src, *ns = s + 1;
    unsigned count = 0;
    unsigned pos = 50;
    for (;s < &src[src_len]; s = ns + 1, ns = s + 1) {
        unsigned r = grabnum(ns, &ns);
        if (*s == 'L') {
            if (pos == 0) pos = 100;
            unsigned to_zero = pos;
            if (r < to_zero) {
                pos -= r;
            } else {
                unsigned over = r - to_zero;
                unsigned rots = over / 100;
                unsigned adjust = over % 100;
                count += 1 + rots;
                pos = (100 - adjust) % 100;
            }
        } else {
            unsigned to_zero = 100 - pos;
            if (r < to_zero) {
                pos += r;
            } else {
                unsigned over = r - to_zero;
                unsigned rots = over / 100;
                unsigned adjust = over % 100;
                count += 1 + rots;
                pos = adjust;
            }
        }
    }
    return count;
}

int main() {
    printf("PART 1 TEST: ");
    if (unsigned long v = do_part1(countof(test), test); v != 3) {
        printf("FAILED (got %lu, expected 3)\n", v);
    } else {
        printf("PASSED\n");
    }

    printf("PART 1 RESULT: %lu\n",
        do_part1(countof(input), input));

    printf("PART 2 TEST: ");
    if (unsigned v = do_part2(countof(test), test); v != 6) {
        printf("FAILED (got %u, expected 6)\n", v);
    } else {
        printf("PASSED\n");
    }

    printf("PART 2 RESULT: %u\n",
        do_part2(countof(input), input));
}