#include "lib.h"

static
ch input[] = {
#embed "day6_input.txt"
};

static
ch test[] = {
#embed "day6_test.txt"
};

typedef struct { ch l[64]; } line;
static_assert(sizeof(line) == 0x40);

alignas(0x40) static
struct {
    line padstart[4];
    struct { num pad[3]; num prev_op_off, op_off, ledge_off, redge_off, rem; };
    union { line l; struct { ch s[16]; num op, pad0, pad1, v; }; } b;
    union { line l; struct { ch s[16], pad0, sr[16], pad1; num v, vr; }; } a;
    line padend;
} m;
static_assert(offsetof(typeof(m),b) % 64 == 0);
static_assert(sizeof(m.b) == 64);
static_assert(sizeof(m.a) == 64);
static_assert(offsetof(typeof(m),padend) % 64 == 0);

static
num do_part1(size_t file_len, ch file[file_len]) {
    ch *s = file;
    m = (typeof(m)){ };

    s = memchr(s, '\n', file_len);
    const num stride = s - file;

    s = file;
    while (*s != '+' && *s != '*') s += stride;
    const num heightb = (s - file);
    const num height  = (s - file) / stride;
    ch *const op = s;

    // constructing a pointer more than 1 past the end of an array
    // is UB, sadly, so we'll use offsets
    m.op_off = op - file;
    s = file;
    do {
        m.ledge_off = m.op_off - heightb;
        if (s[m.op_off] == '+') {
            m.a.v = 0;
            m.rem = height;
            m.b.op = '+' << 8;
            snprintd(m.a.v, 16, m.a.s);
            do {
                ch *t = s + m.ledge_off;
                while (*t < '0') t++;
                m.b.v = grabnum(t, NULL);
                snprintd(m.b.v, 16, m.b.s);
                m.a.v += m.b.v;
                snprintd(m.a.v, 16, m.a.s);
                m.ledge_off += stride;
                m.rem--;
            } while (m.rem);
            m.a.vr += m.a.v;
            snprintd(m.a.vr, 16, m.a.sr);
        } else if (s[m.op_off] == '*') {
            m.a.v = 1;
            m.rem = height;
            m.b.op = '*' << 8;
            snprintd(m.a.v, 16, m.a.s);
            do {
                ch *t = s + m.ledge_off;
                while (*t < '0') t++;
                m.b.v = grabnum(t, NULL);
                snprintd(m.b.v, 16, m.b.s);
                m.a.v *= m.b.v;
                snprintd(m.a.v, 16, m.a.s);
                m.ledge_off += stride;
                m.rem--;
            } while (m.rem);
            m.a.vr += m.a.v;
            snprintd(m.a.vr, 16, m.a.sr);
        }
        m.op_off++;
        while (m.op_off < file_len) {
            if (s[m.op_off] == '+' || s[m.op_off] == '*')
                break;
            m.op_off++;
        }
    } while (m.op_off < file_len);

    return m.a.vr;
}

static
num do_part2(size_t file_len, unsigned char file[file_len]) {
    ch *s = file;
    m = (typeof(m)){ };

    s = memchr(s, '\n', file_len);
    const num stride = s - file;

    s = file;
    while (*s != '+' && *s != '*') s += stride;
    const num heightb = (s - file);
    const num height  = (s - file) / stride;
    ch *const op = s;

    // constructing a pointer more than 1 past the end of an array
    // is UB, sadly, so we'll use offsets
    const num fop_off = op - file;
    m.prev_op_off = fop_off + stride - 1;
    s = file;
    do {
        // we don't need to do these in the same order as the example
        // because both these operations are commutative.
        // but you know what? we can anyway. for fun. and pretty output
        {
            num op_off = m.prev_op_off - 1;
            while (s[op_off] != '+' && s[op_off] != '*' && s[op_off] != '\n')
                op_off--;
            m.op_off = op_off;
        }
        m.ledge_off = m.op_off - heightb;
        m.redge_off = (s[m.prev_op_off] == '\n' ? -1 : -2) + m.prev_op_off - heightb;
        if (s[m.op_off] == '+') {
            m.a.v = 0;
            m.rem = m.redge_off - m.ledge_off + 1;
            const num frem = m.rem;

            m.b.op = '+' << 8;
            snprintd(m.a.v, 16, m.a.s);

            do {
                m.b.v = 0;
                ch *t = s + m.redge_off;
                for (num i = height; i; i--,t+=stride) {
                    if (*t >= '0') {
                        m.b.v *= 10;
                        m.b.v += *t - '0';
                    }
                }
                snprintd(m.b.v, 16, m.b.s);
                m.a.v += m.b.v;
                snprintd(m.a.v, 16, m.a.s);
                m.redge_off--;
                m.rem--;
            } while (m.rem);
            m.a.vr += m.a.v;
            snprintd(m.a.vr, 16, m.a.sr);
        } else if (s[m.op_off] == '*') {
            m.a.v = 1;
            m.rem = m.redge_off - m.ledge_off + 1;
            const num frem = m.rem;

            m.b.op = '*' << 8;
            snprintd(m.a.v, 16, m.a.s);

            do {
                m.b.v = 0;
                ch *t = s + m.redge_off;
                for (num i = height; i; i--,t+=stride) {
                    if (*t >= '0') {
                        m.b.v *= 10;
                        m.b.v += *t - '0';
                    }
                }
                snprintd(m.b.v, 16, m.b.s);
                m.a.v *= m.b.v;
                snprintd(m.a.v, 16, m.a.s);
                m.redge_off--;
                m.rem--;
            } while (m.rem);
            m.a.vr += m.a.v;
            snprintd(m.a.vr, 16, m.a.sr);
        }

        m.prev_op_off = m.op_off;
    } while (m.prev_op_off != fop_off);

    return m.a.vr;
}

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

#define TEST1_EXPECT 4277556
#define TEST2_EXPECT 3263827

void run() {
#if RUN_TEST1
    print("PART 1 TEST: ");
    if (num 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 (num 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(0);
}