/* SPDX-License-Identifier: AGPL-3.0-or-later */
/* Copyright (C) 2026 David (Corey) Herrera */
/**
 * @file fm_golden_vectors.h
 * @brief Reader for the PNGOLDEN1 CPU-reference vectors the Metal kernel
 *   tests check against. Header-only so a test file just includes it.
 *
 *   PROVENANCE: the .bin files in metal/tests/golden are byte copies of the
 *   qwen35moe golden set generated by Pantheon's gen_golden_qwen35.c from a
 *   fixed xorshift32 seed (0x9E3779B9), regenerated there with
 *   `make USE_BLAS=1 golden`. They are checked in here so foundry's tests
 *   need no sibling checkout. Point FM_GOLDEN_DIR at a freshly regenerated
 *   Pantheon set to check for drift.
 *
 *   FILE FORMAT (self-describing):
 *     line 1, ASCII:  PNGOLDEN1 <name> <dtype> <count> seed=0x9E3779B9\n
 *     remainder:      <count> little-endian <dtype> values
 *
 * @status Reads the f32 files, which is every vector these tests use.
 * @issues None
 * @todo None
 */

#ifndef FOUNDRY_METAL_TEST_GOLDEN_VECTORS_H
#define FOUNDRY_METAL_TEST_GOLDEN_VECTORS_H

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* Directory the vectors are read from. Set once at startup. */
static char fm_golden_dir[1024] = "metal/tests/golden";

/**
 * Points the reader at the golden directory: $FM_GOLDEN_DIR if set,
 * otherwise the `golden` directory beside the test binary, which makes the
 * tests runnable from any working directory.
 *
 * @param argv0  argv[0] of the test binary
 */
static void fm_golden_locate(const char *argv0)
{
    const char *env = getenv("FM_GOLDEN_DIR");
    if (env && env[0]) {
        snprintf(fm_golden_dir, sizeof(fm_golden_dir), "%s", env);
        return;
    }
    const char *slash = argv0 ? strrchr(argv0, '/') : NULL;
    if (slash)
        snprintf(fm_golden_dir, sizeof(fm_golden_dir), "%.*s/golden",
                 (int)(slash - argv0), argv0);
}

/**
 * Reads a PNGOLDEN1 f32 vector.
 *
 * Never returns a short or silently defaulted buffer: a missing file, a bad
 * magic, a non-f32 dtype, a count that disagrees with `expect_count`, or a
 * truncated payload all print the reason and return NULL, so a test can
 * only ever run against the real oracle.
 *
 * @param name          File name inside the golden directory
 * @param expect_count  Element count the caller requires
 * @return              malloc'd array of expect_count floats (caller frees),
 *                      or NULL
 */
static float *fm_golden_load_f32(const char *name, size_t expect_count)
{
    char path[1152];
    char header[256];
    char magic[16] = {0}, vec_name[64] = {0}, dtype[8] = {0};
    unsigned long count = 0;
    float *values = NULL;
    FILE *f = NULL;

    snprintf(path, sizeof(path), "%s/%s", fm_golden_dir, name);
    f = fopen(path, "rb");
    if (!f) {
        fprintf(stderr, "  golden: cannot open %s\n", path);
        return NULL;
    }
    if (!fgets(header, sizeof(header), f)) {
        fprintf(stderr, "  golden: %s has no header line\n", path);
        goto cleanup;
    }
    if (sscanf(header, "%15s %63s %7s %lu", magic, vec_name, dtype, &count) != 4 ||
        strcmp(magic, "PNGOLDEN1") != 0 || strcmp(dtype, "f32") != 0) {
        fprintf(stderr, "  golden: %s has a bad header: %s", path, header);
        goto cleanup;
    }
    if (count != expect_count) {
        fprintf(stderr, "  golden: %s holds %lu values, expected %zu\n",
                path, count, expect_count);
        goto cleanup;
    }

    values = (float *)malloc(expect_count * sizeof(float));
    if (!values) {
        fprintf(stderr, "  golden: out of memory for %s\n", path);
        goto cleanup;
    }
    if (fread(values, sizeof(float), expect_count, f) != expect_count) {
        fprintf(stderr, "  golden: %s payload is truncated\n", path);
        free(values);
        values = NULL;
    }

cleanup:
    fclose(f);
    return values;
}

#endif /* FOUNDRY_METAL_TEST_GOLDEN_VECTORS_H */