/*
 * 743_variadic_pack — sentinel for STATUS-3 #16. cstage cgen's
 * variadic gather (`f(args: str...)` called as `f("a", "b", "c")`)
 * emitted only the ptr eightbyte of each str element; the .len
 * eightbyte was never stored, so the callee's `args[i].len` read
 * stack residue. Tagged-union variadics escaped because they took
 * the cg_widen_tagged_store branch; primitive-type variadics
 * (str..., slice..., rune... bigger than 8B) did not.
 *
 * Surfaced by worker-strings pre-flight on the Hare-faithful
 * `concat(strs: str...)` shape; no in-tree caller exercised it
 * because the c1 strings subset shipped non-variadic. Bootstrap
 * byte-id masked it (selfhost only calls fmt.println, which uses
 * tagged-union variadics, hitting the widen-store branch).
 *
 * Rule 10: both stages must emit the same {ptr-store, len-store}
 * pair sequence. Pre-fix cstage emitted 3 ptr-stores only; wwstage
 * already emitted both halves via cgenexpr.ww's velemstr branch.
 *
 * Rows pin asm-presence in both stages and cmp -s byte-id.
 */
#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;
}

static int
slurp(const char *path, char *buf, size_t cap)
{
	FILE *f = fopen(path, "rb");
	if (!f) return -1;
	size_t n = fread(buf, 1, cap - 1, f);
	fclose(f);
	buf[n] = '\0';
	return (int)n;
}

/* Count occurrences of `needle` in `hay` between [start, end). */
static int
count_substr(const char *hay, const char *start, const char *end,
    const char *needle)
{
	int n = 0;
	size_t nlen = strlen(needle);
	const char *p = start;
	while (p + nlen <= end) {
		if (memcmp(p, needle, nlen) == 0) { n++; p += nlen; }
		else { p++; }
	}
	return n;
}

static int
check_caller_stores(const char *spath)
{
	char buf[1 << 16];
	if (slurp(spath, buf, sizeof buf) < 0) return -1;

	const char *body = strstr(buf, "TEXT main");
	if (!body) {
		fprintf(stderr, "variadic_pack: no TEXT main label\n");
		return -1;
	}
	const char *end = strstr(body, "\nTEXT ");
	if (!end) end = buf + strlen(buf);

	/* Three str elements => 3 ptr-stores (MOVQ AX, off(BP)) AND
	 * 3 len-stores (MOVQ BX, off(BP)). The len-store is the bug
	 * pin: pre-fix it was missing entirely. */
	int ptr_stores = count_substr(buf, body, end, "MOVQ\tAX, -");
	int len_stores = count_substr(buf, body, end, "MOVQ\tBX, -");
	if (len_stores < 3) {
		fprintf(stderr,
		    "variadic_pack: only %d len-stores (MOVQ BX, -K(BP)) "
		    "in main; expected >= 3\n", len_stores);
		return -1;
	}
	if (ptr_stores < 3) {
		fprintf(stderr,
		    "variadic_pack: only %d ptr-stores in main; "
		    "expected >= 3\n", ptr_stores);
		return -1;
	}
	return 0;
}

static const char *src_text =
    "fn sumlen(parts: str...) i32 = {\n"
    "    let z: i32 = 0;\n"
    "    let i: i32 = 0;\n"
    "    for (i < parts.len) {\n"
    "        z += parts[i].len;\n"
    "        i += 1;\n"
    "    };\n"
    "    return z;\n"
    "};\n"
    "fn main() i32 = {\n"
    "    return sumlen(\"a\", \"bb\", \"ccc\");\n"
    "};\n";

static int
emit_s(const char *w6c, char *out_s, size_t cap, int tag)
{
	char src[64], cmd[1024];
	snprintf(src, sizeof src, "/tmp/vp_asm_%d_%d.ww", getpid(), tag);
	snprintf(out_s, cap, "/tmp/vp_asm_%d_%d.s", getpid(), tag);

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

	snprintf(cmd, sizeof cmd, "%s -o %s %s 2>/dev/null", w6c, out_s, src);
	int rc = runwait(cmd);
	unlink(src);
	return rc;
}

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 w6c[640], w6c_ww[640];
	snprintf(w6c, sizeof w6c, "%s/w6c", bin);
	snprintf(w6c_ww, sizeof w6c_ww, "%s/w6c_ww", bin);

	int have_ww = (access(w6c_ww, X_OK) == 0);
	int total = 0, fail = 0;

	char cs_path[128], ws_path[128];
	if (emit_s(w6c, cs_path, sizeof cs_path, 0) != 0) {
		fprintf(stderr, "variadic_pack[cstage]: w6c failed\n");
		return 1;
	}
	total++;
	if (check_caller_stores(cs_path) != 0) fail++;

	if (have_ww) {
		if (emit_s(w6c_ww, ws_path, sizeof ws_path, 1) != 0) {
			fprintf(stderr,
			    "variadic_pack[wwstage]: w6c_ww failed\n");
			unlink(cs_path);
			return 1;
		}
		total++;
		if (check_caller_stores(ws_path) != 0) fail++;

		/* Byte-id between stages on the variadic-pack shape. */
		total++;
		char cmd[512];
		snprintf(cmd, sizeof cmd, "cmp -s %s %s", cs_path, ws_path);
		if (runwait(cmd) != 0) {
			fprintf(stderr,
			    "variadic_pack: cstage vs wwstage asm differs\n");
			fail++;
		}
		unlink(ws_path);
	}
	unlink(cs_path);

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