/*
 * Cycle 9 Phase 3 — NEON M3 baseline for H.264 luma qpel mc20 (8x8,
 * horizontal half-pel, 6-tap filter).
 *
 * M1 vs C ref + M3 throughput. License: BSD-2-Clause.
 */
#define _POSIX_C_SOURCE 200809L
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <stddef.h>
#include <string.h>
#include <time.h>
#include <getopt.h>

extern void daedalus_put_h264_qpel8_mc20_ref(
    uint8_t *dst, const uint8_t *src, ptrdiff_t stride);
extern void ff_put_h264_qpel8_mc20_neon(
    uint8_t *dst, const uint8_t *src, ptrdiff_t stride);

#define TILE_STRIDE 16
#define TILE_ROWS   12       /* room for src[-2..+8] + dst[0..7] in one tile */
#define TILE_BYTES  (TILE_ROWS * TILE_STRIDE)
#define SRC_COL     3        /* src points at col SRC_COL of tile = leftmost output col */
#define DST_COL     3        /* dst also at col SRC_COL (overwrite in place); use separate tile for compare */

static uint64_t xs_state;
static inline uint64_t xs(void) {
    uint64_t x = xs_state;
    x ^= x << 13; x ^= x >> 7; x ^= x << 17;
    return xs_state = x;
}

static void gen_tile(uint8_t *tile)
{
    for (int i = 0; i < TILE_BYTES; i++) tile[i] = (uint8_t)(xs() & 0xff);
}

static double now_seconds(void) {
    struct timespec ts;
    clock_gettime(CLOCK_MONOTONIC_RAW, &ts);
    return ts.tv_sec + ts.tv_nsec * 1e-9;
}

static int correctness_check(uint64_t seed, int n)
{
    xs_state = seed ? seed : 0xc0de9264cULL;
    int mismatches = 0, prints = 0;

    /* Use a SRC tile (input) and two DST tiles (one for ref, one for NEON). */
    uint8_t src_tile[TILE_BYTES];
    uint8_t dst_a[TILE_BYTES], dst_b[TILE_BYTES];

    for (int i = 0; i < n; i++) {
        gen_tile(src_tile);
        memset(dst_a, 0, sizeof(dst_a));
        memset(dst_b, 0, sizeof(dst_b));

        const uint8_t *src_ptr = src_tile + SRC_COL;
        uint8_t *dst_a_ptr = dst_a + DST_COL;
        uint8_t *dst_b_ptr = dst_b + DST_COL;

        daedalus_put_h264_qpel8_mc20_ref(dst_a_ptr, src_ptr, TILE_STRIDE);
        ff_put_h264_qpel8_mc20_neon(dst_b_ptr, src_ptr, TILE_STRIDE);

        int diff = 0;
        for (int r = 0; r < 8; r++)
            for (int c = 0; c < 8; c++)
                if (dst_a[r*TILE_STRIDE + DST_COL + c] != dst_b[r*TILE_STRIDE + DST_COL + c]) diff++;
        if (diff) {
            if (prints < 3) {
                fprintf(stderr, "MISMATCH block %d (%d/64 pix diff):\n", i, diff);
                prints++;
            }
            mismatches++;
        }
    }
    printf("M1₉ correctness: %d / %d blocks bit-exact (%.4f%%)\n",
           n - mismatches, n, 100.0 * (n - mismatches) / n);
    return mismatches;
}

static void throughput_neon(uint64_t seed, int n_blocks, double duration_s)
{
    xs_state = seed ? seed : 0xc0de9264cULL;
    uint8_t *src_master = malloc((size_t) n_blocks * TILE_BYTES);
    uint8_t *dst_master = malloc((size_t) n_blocks * TILE_BYTES);
    uint8_t *dst_work   = malloc((size_t) n_blocks * TILE_BYTES);
    if (!src_master || !dst_master || !dst_work) { fprintf(stderr, "alloc fail\n"); exit(1); }

    for (int i = 0; i < n_blocks; i++) {
        for (int j = 0; j < TILE_BYTES; j++) {
            src_master[i*TILE_BYTES + j] = (uint8_t)(xs() & 0xff);
            dst_master[i*TILE_BYTES + j] = 0;
        }
    }

    memcpy(dst_work, dst_master, (size_t) n_blocks * TILE_BYTES);
    for (int i = 0; i < n_blocks; i++)
        ff_put_h264_qpel8_mc20_neon(dst_work + i*TILE_BYTES + DST_COL,
                                     src_master + i*TILE_BYTES + SRC_COL, TILE_STRIDE);

    double t0 = now_seconds();
    double t_end = t0 + duration_s;
    uint64_t done = 0;
    while (now_seconds() < t_end) {
        memcpy(dst_work, dst_master, (size_t) n_blocks * TILE_BYTES);
        for (int i = 0; i < n_blocks; i++)
            ff_put_h264_qpel8_mc20_neon(dst_work + i*TILE_BYTES + DST_COL,
                                         src_master + i*TILE_BYTES + SRC_COL, TILE_STRIDE);
        done += n_blocks;
    }
    double elapsed = now_seconds() - t0;

    int iters = (int)(done / n_blocks);
    double s0 = now_seconds();
    for (int i = 0; i < iters; i++)
        memcpy(dst_work, dst_master, (size_t) n_blocks * TILE_BYTES);
    double s1 = now_seconds();

    double kernel_seconds = elapsed - (s1 - s0);
    double mbps = done / kernel_seconds / 1e6;

    printf("M3₉ NEON throughput:\n");
    printf("  blocks/batch:    %d\n", n_blocks);
    printf("  batches done:    %d\n", iters);
    printf("  total blocks:    %llu\n", (unsigned long long) done);
    printf("  elapsed (kernel)=%.6f s\n", kernel_seconds);
    printf("  throughput      = %.3f Mblock/s\n", mbps);
    printf("  per-block       = %.1f ns\n", kernel_seconds / done * 1e9);
    /* 1080p H.264 luma MC: ~32400 blocks/frame × 30 fps ≈ 0.972 Mblock/s
     * for 8x8 blocks. For 16x16 (typical macroblock-mode MC) it's
     * ~0.243 Mblock/s. Use the conservative 8x8 estimate. */
    printf("  H.264 1080p30 8x8 MC floor: %.2fx margin (0.972 Mblock/s req'd)\n", mbps / 0.972);

    free(src_master); free(dst_master); free(dst_work);
}

int main(int argc, char **argv)
{
    int n_blocks = 65536;
    double duration = 5.0;
    uint64_t seed = 0;
    int do_correctness = 1;

    static struct option opts[] = {
        {"blocks",         required_argument, 0, 'b'},
        {"duration",       required_argument, 0, 'd'},
        {"seed",           required_argument, 0, 's'},
        {"no-correctness", no_argument,       0, 'C'},
        {0,0,0,0}
    };
    for (int c; (c = getopt_long(argc, argv, "b:d:s:C", opts, 0)) != -1;) {
        switch (c) {
        case 'b': n_blocks = atoi(optarg); break;
        case 'd': duration = atof(optarg); break;
        case 's': seed = strtoull(optarg, 0, 0); break;
        case 'C': do_correctness = 0; break;
        default: return 2;
        }
    }

    if (do_correctness) {
        printf("=== M1₉ bit-exact (10000 random 8x8 blocks) ===\n");
        int mis = correctness_check(seed, 10000);
        if (mis != 0) {
            fprintf(stderr, "M1 gate FAILED — refusing to measure throughput.\n");
            return 1;
        }
        printf("\n");
    }

    printf("=== M3₉ NEON throughput ===\n");
    throughput_neon(seed, n_blocks, duration);
    return 0;
}