#include "lib.h"

#define DBG 0

static
unsigned char input[] = {
#embed "day2_input.txt"
};

static
unsigned char test[] = {
#embed "day2_test.txt"
};

uint64_t ipow(uint64_t a, uint64_t b) {
    uint64_t m = a;
    for (;b;b--) m += a;
    return m;
}

static
uint64_t range(uint64_t start, uint64_t end, uint64_t len) {
#if DBG
    print("==\n");
    printd(start); print(" "); printd(end); print("\n");
#endif

    if ((len & 1) == 1) {
        return 0;
    }

    uint64_t divisor = ipow(10, len / 2);

    uint64_t first = (start + divisor - 1) / divisor;
    uint64_t second = end / divisor;

#if DBG
    print("\n");
    printd(divisor); print("\n");
    printd(first); print(" "); printd(second); print("\n");
#endif

    uint64_t r = (((second + first) * (second + 1 - first)) / 2) * divisor;

#if DBG
    printd(r); print("\n");
#endif

    return r;
}

static
uint64_t do_part1(size_t file_len, unsigned char file[file_len]) {
    unsigned char buffer[65535];
    memcpy(buffer, file, file_len);
    size_t size = file_len;
    buffer[file_len-1] = ',';

    uint64_t out = 0;
    uint64_t i = 0;

    while (i < size) {
#if DBG
        print("--------------\n");
#endif
        uint64_t startlen = 0, endlen = 0;
        uint64_t start = grabnum(buffer+i, NULL);

        while (buffer[i] != '-') {
            i++;
            startlen++;
        }
        i++;

        uint64_t end = grabnum(buffer+i, NULL);

        while (buffer[i] != ',') {
            i++;
            endlen++;
        }
        i++;

#if DBG
        printd(startlen); print(" "); printd(start); print((char[]){ 10 });
        printd(startlen); print(" "); printd(start); print((char[]){ 10 });
#endif

        if (endlen != startlen) {
            out += range(start, ipow(10, startlen) - 1, startlen)
                +  range(ipow(10, startlen), end, endlen);
        } else {
            out += range(start, end, startlen);
        }

#if DBG
        print((char[]) { 10 });
#endif
    }

    return out;
}

#define RUN_TEST1 1
#define RUN_PART1 1

#define TEST1_EXPECT 0x1227775554l

void run() {
    volatile uintptr_t s = (uintptr_t)&s;
    printh(s);
    print("\n");
#if RUN_TEST1
    print("PART 1 TEST: ");
    if (uint64_t 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

    exit_group(0);
}