/* === aoc202408 =======================================================
   Oh! another square of text!
   Idea: for all points p with an antenna find all points q>p with
a corresponding frequency. For each such pair calculate the 2 antinodes
and add the resulting points (if not there already) to an array.
   The answer to Part One is the number of elements in the array
===================================================================== */









void aoc202408(char *data, size_t len) {
    (void)len; // unused argument
    struct TextGrid tg;
    tg.data = data;
    tg.cols = strchr(data, '\n') - data + 1;
    tg.rows = tg.cols - 1; // rows includes the '\n'
    #if 0
    unsigned anti[256][2]; // locations of antinodes
    unsigned nanti = 0;
    #endif

    char *p = data;
    while (*p) {
        while ((*p == '.') || (*p == '\n')) p++;
        if (*p) {
            // p points to an antenna
            unsigned prow = TGrow(&tg, p), pcol = TGcol(&tg, p);
            char *q = strchr(p+1, *p);
            while (q) {
                // q points to an antenna of the same type as p
                unsigned qrow = TGrow(&tg, q), qcol = TGcol(&tg, q);
                int deltarow = (int)qrow - (int)prow;
                int deltacol = (int)qcol - (int)pcol;
                printf("p is at (C:%u, R:%u); q is at (C:%u, R:%u) ... delta: (C: %d, R: %d)\n",
                      pcol, prow, qcol, qrow, deltacol, deltarow);
                int col1 = (int)pcol - deltacol, row1 = (int)prow - deltarow;
                if (TGvalid(&tg, row1, col1)) {
                    printf("antinode at (C:%u, R:%u)\n", col1, row1);
                }
                int col2 = (int)qcol + deltacol, row2 = (int)qrow + deltarow;
                if (TGvalid(&tg, row2, col2)) {
                    printf("antinode at (C:%u, R:%u)\n", col2, row2);

                }
                q = strchr(q+1, *p); // next antenna of this type
            }
            p += 1;
        }
    }
    #if 0
    unsigned size = 1 + strchr(data, '\n') - data;
    for (unsigned row = 0; row < size-1; row++) {

        for (unsigned col = 0; col < size-1; col++) {
            char *p = data + linearize2d(size, row, col);
            if (*p != '.') {
                char *q = strchr(p + 1, *p);
                while (q) {
                    printf("found '%c'('%c')\n", *p, *q);
                    ptrdiff_t delta = q - p;
#if 0
                    int row_pos = (int)(linear_pos / size);
                    int col_pos = (int)(linear_pos % size);
#endif
                    if (p >= data + delta) {
                        // antinode
                        anti[nanti][0] = row(p - delta);
                        anti[nanti++][1] = col(p - delta);
                    }
                    if (q < "end of data" - delta) {
                        // antinode
                        anti[nanti][0] = row(q + delta);
                        anti[nanti++][1] = col(q + delta);
                    }
                    q = strchr(q + 1, *p);
                }

            }
        }
    }
    printf("There are %u antinodes within the map.\n", nanti);
    #endif
}

/* === aoc202407 =======================================================
   Part one looks easy
   Part two also easy
 ===================================================================== */