/*
 * 727_modcall_widen_slice — sentinel for #28. Pins wwstage's cgcall to
 * look up calleeparams for module-qualified `mod.fn(...)` callees, so
 * pushargsrev's widening detection fires for an N_IDENT slice arg
 * passed to a tagged-union parameter slot.
 *
 * Pre-fix wwstage `cgcall` (selfhost/cmd/wcc/cgenexpr.ww:2861) only
 * called fnparamslookup when `callee.kind == nkind.N_IDENT`. For
 * `mod.fn(...)` (N_DOT callee), `calleeparams` stayed nil; pushargsrev's
 * widening detection is gated on `param != nil` so it never fired;
 * the N_IDENT-slice fast path (cgenutil.ww:368-383) then pushed only
 * 3 slot words (ptr/len/cap) and DROPPED the variant tag word. The
 * callee subsequently dispatched on (callee-arg-reg holds ptr instead
 * of tag) — a runtime miscompile, not a pure byte-id divergence.
 *
 * Cstage finds params via `n->lhs->type` (the checker-set type on the
 * N_DOT callee node, cmd/w6c/cgen.c:4161-4165), bypassing the name-
 * driven registry. Wwstage needed the mirror via N_DOT.lhs.str.
 *
 * Same-family sister of #21 (N_CALL dispatch in pushargsrev), #19
 * (N_TSLICE match arm), #24 (N_CALL slice arm) — the pattern is
 * wwstage dispatchers periodically missing arms cstage gets natively
 * via typed AST.
 *
 * Bootstrap-blocking when lib/strings v3 (drags utf8 + bytes into the
 * build) lands.
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.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;
};

/* Two-module probe: `caller` calls `needle.want(h, n)` where `n: []u8`
 * widens into `(u8 | []u8)`. The // MODULE: directives + `use needle;`
 * shape parallels what cmd/ww driver synthesises in combined.ww. */
static const struct row rows[] = {
	{ "dot_callee_slice_widen",
	  "package needle;\n"
	  "export fn want(haystack: []u8, needle: (u8 | []u8)) i32 = {\n"
	  "    let r: i32 = haystack.len;\n"
	  "    match (needle) {\n"
	  "    case let b: u8     => r = r + (b: i32);\n"
	  "    case let s: []u8   => r = r + s.len;\n"
	  "    };\n"
	  "    return r;\n"
	  "};\n"
	  "package caller;\n"
	  "import needle;\n"
	  "export fn main() i32 = {\n"
	  "    let h: []u8;\n"
	  "    let n: []u8 = h;\n"
	  "    return needle.want(h, n);\n"
	  "};\n" },
};

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;
}

static int
emit_s(const char *w6c, const struct row *r, int i, char *out_s, size_t cap)
{
	char src[64], cmd[1024];
	snprintf(src, sizeof src, "/tmp/mws_%d_%d.ww", getpid(), i);
	snprintf(out_s, cap, "/tmp/mws_%d_%d_%s.s",
	    getpid(), i, w6c[strlen(w6c) - 1] == 'w' ? "ww" : "c");

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

/* Inside TEXT main, the call to needle.want must push 4 needle words
 * (cap, len, ptr, tag) before the haystack pushes. Asserts the tag-
 * synth `MOVQ $1, AX; PUSHQ AX` lands between the slice-triple pushes
 * and the next-arg load. Pre-fix the tag synth is absent — the
 * needle slot ends at the third PUSHQ AX. */
static int
check_tag_push_present(const char *spath, const struct row *r,
    const char *stage)
{
	char buf[1 << 14];
	if (slurp(spath, buf, sizeof buf) < 0) {
		fprintf(stderr, "row[%s][%s]: cannot read %s\n",
		    r->label, stage, spath);
		return -1;
	}
	const char *fn = strstr(buf, "TEXT main");
	if (!fn) {
		fprintf(stderr, "row[%s][%s]: no TEXT main in %s\n",
		    r->label, stage, spath);
		return -1;
	}
	const char *call = strstr(fn, "CALL\tneedle.want");
	if (!call) {
		fprintf(stderr, "row[%s][%s]: no CALL needle.want\n",
		    r->label, stage);
		return -1;
	}
	/* Tag synth: a `MOVQ\t$1, AX` followed by a `PUSHQ\tAX` between
	 * fn-start and the call. The literal `$1` is the slice-variant
	 * tag index in (u8 | []u8). */
	int found = 0;
	const char *p = fn;
	while (p < call) {
		const char *m = strstr(p, "MOVQ\t$1, AX");
		if (!m || m >= call) break;
		const char *nx = strstr(m, "PUSHQ\tAX");
		if (nx && nx < call) { found = 1; break; }
		p = m + 1;
	}
	if (!found) {
		fprintf(stderr,
		    "row[%s][%s]: no tag-synth `MOVQ $1, AX; PUSHQ AX` before CALL needle.want\n",
		    r->label, stage);
		return -1;
	}
	/* Also assert the post-call `ADDQ $8, SP` (overflow cleanup) is
	 * emitted — 7 SysV reg slots for {haystack 3 + needle 4} leaves
	 * 1 word stack-overflowed. Pre-fix wwstage only pushed 6, so no
	 * cleanup either. */
	const char *cleanup = strstr(call, "ADDQ\t$8, SP");
	const char *nexttext = strstr(call, "TEXT ");
	if (!cleanup || (nexttext && cleanup > nexttext)) {
		fprintf(stderr,
		    "row[%s][%s]: no `ADDQ $8, SP` overflow cleanup after CALL needle.want\n",
		    r->label, stage);
		return -1;
	}
	return 0;
}

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 n = (int)(sizeof rows / sizeof rows[0]);
	int total = 0, fail = 0;

	for (int i = 0; i < n; i++) {
		char cs_path[128], ws_path[128];

		if (emit_s(w6c, &rows[i], i, cs_path, sizeof cs_path) != 0) {
			fprintf(stderr,
			    "modcall_widen_slice[cstage][%s]: w6c failed\n",
			    rows[i].label);
			fail++; total++; continue;
		}
		total++;
		if (check_tag_push_present(cs_path, &rows[i], "cstage") != 0)
			fail++;

		if (!have_ww) { unlink(cs_path); continue; }

		if (emit_s(w6c_ww, &rows[i], i, ws_path, sizeof ws_path) != 0) {
			fprintf(stderr,
			    "modcall_widen_slice[wwstage][%s]: w6c_ww failed\n",
			    rows[i].label);
			fail++; total++;
			unlink(cs_path); continue;
		}
		total++;
		if (check_tag_push_present(ws_path, &rows[i], "wwstage") != 0)
			fail++;

		/* byte-id between stages — the principled sentinel for the
		 * polarity catalog. */
		total++;
		char cmd[512];
		snprintf(cmd, sizeof cmd, "cmp -s %s %s", cs_path, ws_path);
		if (runwait(cmd) != 0) {
			fprintf(stderr,
			    "modcall_widen_slice[%s]: cstage vs wwstage asm differs\n",
			    rows[i].label);
			fail++;
		}

		unlink(cs_path); unlink(ws_path);
	}

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