#include <stdlib.h>
#include <stdcountof.h>
#include <stdint.h>
#include <string.h>

#define SYS_write 1
#define SYS_exit_group 231

#define STDOUT_FILENO 1

static
void write(uint64_t fileno, void *buffer, size_t len) {
    uint64_t a,d;
    asm volatile("syscall"
        :"=a"(a),"=d"(d):"a"(SYS_write),"D"(fileno),"S"(buffer),"d"(len):"memory");
}

[[noreturn]] static
void exit_group() {
    asm volatile(
        "syscall\n"
        "ud2"
        ::"a"(SYS_exit_group),"D"(0));
    for (;;);
}

#define xstr(s) str(s)
#define str(s) #s

static
void print_many_char(size_t len, char chars[len]) {
    write(STDOUT_FILENO, chars, len);
}

#define print(string) print_many_char(sizeof(string)-1, string)

static
void printd(unsigned long v) {
    if (!v) {
        print("0");
        return;
    }
    char buf[32];
    char *p = buf+32;
    unsigned count = 0;
    while (v) {
        p--;
        *p = '0' + (v % 10);
        v /= 10;
        count++;
    }
    write(STDOUT_FILENO, p, count);
}

static
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;
}

#define DBG 1

#define RUN_PART1 1
#define RUN_PART2 1
#define RUN_TEST1 1
#define RUN_TEST2 1

#define TEST1_EXPECT 3
#define TEST2_EXPECT 6

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

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

static
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;
}

static
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;
}

void run() {
#if RUN_TEST1
    print("PART 1 TEST: ");
    if (unsigned long v = do_part1(countof(test), test); v != TEST1_EXPECT) {
        print("FAILED (got ");
        printd(v);
        print(", expected " xstr(TEST1_EXPECT) ")\n");
    } else {
        print("PASSED\n");
    }
#endif

#if RUN_PART1
    print("PART 1 RESULT: ");
    printd(do_part1(countof(input), input));
    print("\n");
#endif

#if RUN_TEST2
    print("PART 2 TEST: ");
    if (unsigned v = do_part2(countof(test), test); v != TEST2_EXPECT) {
        print("FAILED (got ");
        printd(v);
        print(", expected " xstr(TEST2_EXPECT) ")\n");
    } else {
        print("PASSED\n");
    }
#endif

#if RUN_PART2
    print("PART 2 RESULT: ");
    printd(do_part2(countof(input), input));
    print("\n");
#endif

    exit_group();
}