/*
 * 932_str_elem_cap_run — runtime coverage for the F2 fold: a str-element
 * VALUE read via N_INDEX must load the full 24B {ptr,len,cap} header, not
 * just {ptr,len}. str is 24B since Phase 2 (#1); pre-F2 the N_INDEX
 * str-element arms dropped the cap word.
 *
 * The existing byte-id gates (990-997) can't catch a no-op fold here: a
 * shared 2-word miscompile passes byte-id silently. So this pins the
 * *runtime* contract — build each fixture through both the cstage `ww`
 * and the wwstage `ww_ww` driver and confirm the program's assertions
 * hold (exit 0).
 *
 * Each row POISONS the element so cap != len (a `.cap =` pseudo-field
 * write, no malloc / no import — keeps the fixture self-contained so
 * ww_ww writes intermediates only next to the /tmp source, not lib/).
 * A 2-word read leaves cap = len (Site A) or a stale slice-cap (Site B),
 * so the read-back .cap mismatches the poisoned value and the row fails.
 *
 * Both N_INDEX base forms are covered:
 *   - Site A: N_IDENT base — `xs[0]` on a local `[N]str`.
 *   - Site B: fallback base — `b.items[0]` where the base `b.items` is
 *     an N_DOT (slice field), not a plain ident.
 *
 * The cap word is observed through `let e: str = <index>` (a 3-word
 * copy into the slot) then `e.cap` (an N_IDENT pseudo-field read off the
 * slot). A direct `<index>.cap` would NOT observe it — the non-ident
 * .cap N_DOT path only handles .ptr/.len today (a separate gap, out of
 * F2's scope).
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/wait.h>

static int
runwait(const char *cmd)
{
	int rc = system(cmd);
	if (rc == -1) return -1;
	if (WIFEXITED(rc)) return WEXITSTATUS(rc);
	return -1;
}

struct row { const char *label; const char *src; int want; };

static const struct row rows[] = {
	/* Site A — N_IDENT base. Poison cap=8 (len=2), read back via a
	 * local [2]str. Broken 2-word read leaves cap = len = 2. */
	{ "sitea_ident_base",
	  "export fn main() i32 = {\n"
	  "    let p: str = \"hi\";\n"
	  "    p.cap = 8i32;\n"
	  "    let xs: [2]str;\n"
	  "    xs[0] = p;\n"
	  "    let e: str = xs[0];\n"
	  "    if (e.cap: i32 != 8) { return 1; };\n"
	  "    if (e.len: i32 != 2) { return 2; };\n"
	  "    return 0;\n"
	  "};\n",
	  0 },
	/* Site B — fallback base. Element behind an N_DOT slice field, so
	 * the N_INDEX base isn't a plain ident. Poison cap=9 (len=5).
	 * Broken read leaves cap = the slice header's own cap, not the
	 * element's. */
	{ "siteb_fallback_base",
	  "type box = struct { items: []str };\n"
	  "export fn main() i32 = {\n"
	  "    let q: str = \"world\";\n"
	  "    q.cap = 9i32;\n"
	  "    let arr: [2]str;\n"
	  "    arr[0] = q;\n"
	  "    let b: box;\n"
	  "    b.items = arr[0:2];\n"
	  "    let e: str = b.items[0];\n"
	  "    if (e.cap: i32 != 9) { return 1; };\n"
	  "    if (e.len: i32 != 5) { return 2; };\n"
	  "    return 0;\n"
	  "};\n",
	  0 },
};

static int
run_driver(const char *driver, const struct row *r, int i)
{
	char src[96], tmpdir[96], cmd[1024];
	snprintf(src, sizeof src, "/tmp/strelemcap_%d_%d.ww", getpid(), i);
	snprintf(tmpdir, sizeof tmpdir, "/tmp/strelemcap_%d_d_%d", getpid(), i);

	FILE *f = fopen(src, "wb");
	if (!f) return -1;
	fputs(r->src, f);
	fclose(f);

	mkdir(tmpdir, 0755);
	snprintf(cmd, sizeof cmd, "cd %s && %s build %s",
	    tmpdir, driver, src);
	if (runwait(cmd) != 0) {
		fprintf(stderr, "row[%s]: build via %s failed\n",
		    r->label, driver);
		unlink(src); rmdir(tmpdir);
		return -1;
	}

	const char *base = strrchr(src, '/');
	base = base ? base + 1 : src;
	char outbin[160];
	snprintf(outbin, sizeof outbin, "%s/%s", tmpdir, base);
	char *dot = strrchr(outbin, '.');
	if (dot && strcmp(dot, ".ww") == 0) *dot = '\0';
	int got = runwait(outbin);

	unlink(src); unlink(outbin); rmdir(tmpdir);
	return got;
}

int
main(void)
{
	const char *bin = getenv("BIN");
	if (!bin) bin = "out/bin";
	char absbin[512];
	if (bin[0] != '/') {
		char cwd[256];
		if (getcwd(cwd, sizeof cwd) == NULL) return 1;
		snprintf(absbin, sizeof absbin, "%s/%s", cwd, bin);
		bin = absbin;
	}

	char cdrv[640];
	snprintf(cdrv, sizeof cdrv, "%s/ww", bin);
	char wdrv[640];
	snprintf(wdrv, sizeof wdrv, "%s/ww_ww", bin);

	struct { const char *name; const char *path; int gated_on_existence; }
	drivers[] = {
		{ "cstage",  cdrv, 0 },
		{ "wwstage", wdrv, 1 },
		{ NULL, NULL, 0 },
	};

	int n = (int)(sizeof rows / sizeof rows[0]);
	int total = 0, fail = 0;
	for (int d = 0; drivers[d].name; d++) {
		if (drivers[d].gated_on_existence
		    && access(drivers[d].path, X_OK) != 0) {
			fprintf(stderr,
			    "str_elem_cap_run: skip %s (no %s)\n",
			    drivers[d].name, drivers[d].path);
			continue;
		}
		for (int i = 0; i < n; i++) {
			int got = run_driver(drivers[d].path, &rows[i], i);
			total++;
			if (got != rows[i].want) {
				fprintf(stderr,
				    "str_elem_cap_run[%s][%s]: exit=%d want=%d\n",
				    drivers[d].name, rows[i].label,
				    got, rows[i].want);
				fail++;
			}
		}
	}

	if (fail) {
		fprintf(stderr, "str_elem_cap_run: %d/%d fixtures failed\n",
		    fail, total);
		return 1;
	}
	printf("str_elem_cap_run: %d/%d ok\n", total, total);
	return 0;
}