/*
 * 783_amp_fn_assign_run — project #206 close. Pins that a bare
 * `&fn_name` is assignable into a `*<fn-alias>` slot and a
 * `(*<fn-alias> | void)` tagged slot (the io vstream vtable shape)
 * WITHOUT the explicit `(&fn): *alias` cast that the lib/{io,memio,
 * fmt,bufio,log} vstream surfaces currently carry. #94 fold-eFinal
 * drops those casts wholesale once this is green.
 *
 * THE FIX (Option C, both stages, checker-only — cgen is a no-op
 * fn-pointer reinterpret): type_assignable / isassignable stay fully
 * NOMINAL (a materialized `*fn` value laundered into a `*alias` is
 * rejected, mirror of harec ref/harec/src/types.c:1039-1066). A
 * caller-site gate `assignable_addrfn` (cmd/wcc/check.c) /
 * `assignableaddrfn` (selfhost/cmd/wcc/check.ww) admits ONLY a DIRECT
 * `&`-of-fn-ident whose signature structurally matches the
 * destination's pointed-to fn alias, or — for a tagged dst — the
 * single matching ptr-to-fn variant (>=2 same-sig variants is
 * ambiguous → reject). This is harec's adopt-the-alias-at-the-`&`-site
 * rule (ref/harec/src/check.c:3594-3626) without threading a type
 * hint through the bottom-up expression checker.
 *
 * ROW POLARITY:
 *   POSITIVE rows build + run on BOTH stages and assert cs.s == ww.s
 *   (rule-10). `let_call` and `structlit_build` pin the let-binding and
 *   struct-literal-field-init gate sites. `fieldstore_dispatch` pins the
 *   eFinal SHIPPING shape: a bare &fn field-STORE into one slot of the
 *   three-slot io.vtable (reader/writer/closer), then a dispatcher match
 *   on a *vtable POINTER-param (test 775) — exercising both the live-
 *   code-address call-through and the void-arm. It is byte-id-clean: the
 *   single-slot local-composite zero-init divergence (project #213,
 *   reproduces with the cast form and a pure `(i32|void)` field — NOT a
 *   #206 regression) is a single-field artifact the real three-slot
 *   io.vtable does not hit.
 *
 *   NEGATIVE non-tagged rows (`neg_launder`, `neg_samesig`) MUST fail
 *   to build on BOTH stages — #206 turned the wwstage lenient pointer-fn
 *   punt into a confident reject, so a laundered `*fn` value and a
 *   same-signature distinct alias are nominally rejected on both.
 *
 *   NEGATIVE tagged-slot rows (`neg_ambiguous_tagged`,
 *   `neg_launder_tagged`) are pinned CSTAGE-ONLY. cstage REJECTS both.
 *   wwstage WRONGLY ACCEPTS them: its `(X | void)` tagged-assignability
 *   leniently matches any `*fn` against the `void` variant (project
 *   #214, the void-variant OVER-acceptance). #214 is an accept-INVALID
 *   hole and its close is REQUIRED BEFORE wwstage can become the
 *   authoritative selfhost checker; these rows graduate to STAGE_WW
 *   when #214 closes. Mirrors the 777/780/781/782 STAGE_CS carve-out.
 *
 * GATE POLARITY: must stay GREEN. Red means the #206 gate over- or
 * under-accepts, the nominal reject regressed, or the fn-pointer
 * call-arm miscompiled.
 */
#include <stdio.h>
#include <stdlib.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;
}

#define STAGE_CS	1
#define STAGE_WW	2

struct row {
	const char *label;
	const char *src;
	int want_exit;		/* expected program exit (build+run rows) */
	int stage_mask;
	int byte_id;		/* assert cs.s == ww.s */
	int expect_fail;	/* 1 = build MUST fail; want_exit ignored */
};

static const struct row rows[] = {
	/* POSITIVE byte-id: bare &fn into a *<fn-alias> let, then call. */
	{ "let_call",
	  "package main;\n"
	  "type reader = fn(x: i32) i32;\n"
	  "fn rd(x: i32) i32 = { return x + 1; };\n"
	  "fn main() i32 = {\n"
	  "    let p: *reader = &rd;\n"
	  "    return (*p)(41);\n"
	  "};\n",
	  42, STAGE_CS | STAGE_WW, 1, 0 },

	/* POSITIVE byte-id: struct-literal field-init of a (*alias|void)
	 * slot with bare &fn (the Hare `vtable{reader=&fn}` shape). Build
	 * only — no match (project #212 blocks struct-lit-tagged + match
	 * on wwstage cgen); the checker gate acceptance is what this pins. */
	{ "structlit_build",
	  "package main;\n"
	  "type reader = fn(x: i32) i32;\n"
	  "type vtable = struct { r: (*reader | void) };\n"
	  "fn rd(x: i32) i32 = { return x + 1; };\n"
	  "fn main() i32 = {\n"
	  "    let v = vtable { r = &rd };\n"
	  "    return 0;\n"
	  "};\n",
	  0, STAGE_CS | STAGE_WW, 1, 0 },

	/* POSITIVE byte-id: bare &fn FIELD-STORE into a (*reader|void) slot
	 * of the THREE-slot vtable (the exact io.vtable reader/writer/closer
	 * eFinal shape, test 775), then dispatcher match on a *vtable
	 * POINTER-param. The live-code-address call-through AND the void-arm
	 * discrimination are exercised, and cs.s == ww.s (rule-10). This is
	 * the eFinal SHIPPING path, so it MUST be byte-id-clean: the single-
	 * slot local-composite zero-init divergence (#213) is a single-field
	 * artifact that the real three-slot io.vtable does not hit. */
	{ "fieldstore_dispatch",
	  "package main;\n"
	  "type reader = fn(s: *vtable, x: i32) i32;\n"
	  "type vtable = struct {\n"
	  "    reader: (*reader | void),\n"
	  "    writer: (*reader | void),\n"
	  "    closer: (*reader | void),\n"
	  "};\n"
	  "fn rd(s: *vtable, x: i32) i32 = { return x + 1; };\n"
	  "fn dispatch(s: *vtable, x: i32) i32 = {\n"
	  "    match (s.reader) {\n"
	  "    case void => { return -1; };\n"
	  "    case let f: *reader => { return (*f)(s, x); };\n"
	  "    };\n"
	  "};\n"
	  "fn main() i32 = {\n"
	  "    let a: vtable;\n"
	  "    a.reader = &rd;\n"
	  "    let b: vtable;\n"
	  "    b.reader = void;\n"
	  "    return dispatch(&a, 41) + dispatch(&b, 0) + 11;\n"
	  "};\n",
	  52, STAGE_CS | STAGE_WW, 1, 0 },

	/* NEGATIVE both stages: a materialized *fn value laundered into a
	 * *reader slot. harec rejects (nominal pointer assignability); both
	 * ww stages now reject too. */
	{ "neg_launder",
	  "package main;\n"
	  "type reader = fn(x: i32) i32;\n"
	  "fn rd(x: i32) i32 = { return x + 1; };\n"
	  "fn main() i32 = {\n"
	  "    let p = &rd;\n"
	  "    let s: *reader = p;\n"
	  "    return 0;\n"
	  "};\n",
	  0, STAGE_CS | STAGE_WW, 0, 1 },

	/* NEGATIVE both stages: distinct same-signature aliases. A `&add1`
	 * must NOT flow into a *negator slot — defeating that nominal
	 * distinction is exactly what the gate's structural-but-direct rule
	 * prevents (the gate fires for &add1 only against an alias whose
	 * underlying fn matches; the laundered value here is not a direct
	 * &fn, and even a direct &add1 into *negator is accepted only if
	 * negator's underlying matches — which it does structurally, so the
	 * laundering form below, NOT a direct &fn, is the one that must
	 * reject). */
	{ "neg_samesig",
	  "package main;\n"
	  "type adder = fn(x: i32) i32;\n"
	  "type negator = fn(x: i32) i32;\n"
	  "fn add1(x: i32) i32 = { return x + 1; };\n"
	  "fn main() i32 = {\n"
	  "    let p = &add1;\n"
	  "    let n: *negator = p;\n"
	  "    return 0;\n"
	  "};\n",
	  0, STAGE_CS | STAGE_WW, 0, 1 },

	/* NEGATIVE cstage-only (#214 wwstage void-variant over-acceptance):
	 * two same-signature ptr-to-fn variants in the tagged dst — a direct
	 * &fn is ambiguous and must be rejected, never silently bound to one. */
	{ "neg_ambiguous_tagged",
	  "package main;\n"
	  "type reader = fn(x: i32) i32;\n"
	  "type writer = fn(x: i32) i32;\n"
	  "fn myfn(x: i32) i32 = { return x; };\n"
	  "fn main() i32 = {\n"
	  "    let x: (*reader | *writer | void) = &myfn;\n"
	  "    return 0;\n"
	  "};\n",
	  0, STAGE_CS, 0, 1 },

	/* NEGATIVE cstage-only (#214): laundering a materialized *fn into a
	 * (*reader|void) tagged slot. cstage rejects nominally; wwstage's
	 * void-variant leniency wrongly accepts. */
	{ "neg_launder_tagged",
	  "package main;\n"
	  "type reader = fn(x: i32) i32;\n"
	  "fn rd(x: i32) i32 = { return x + 1; };\n"
	  "fn main() i32 = {\n"
	  "    let p = &rd;\n"
	  "    let s: (*reader | void) = p;\n"
	  "    return 0;\n"
	  "};\n",
	  0, STAGE_CS, 0, 1 },
};

static void
cleanup_tmp(const char *tmpdir, const char *base)
{
	char p[1024];
	snprintf(p, sizeof p, "%s/%s",             tmpdir, base); unlink(p);
	snprintf(p, sizeof p, "%s/%s.ww",          tmpdir, base); unlink(p);
	snprintf(p, sizeof p, "%s/%s.o",           tmpdir, base); unlink(p);
	snprintf(p, sizeof p, "%s/%s.combined.ww", tmpdir, base); unlink(p);
	/* #93: the sep scratch dir + the tmpdir-pinned pkgcache. */
	snprintf(p, sizeof p, "rm -rf %s/%s.sepwork %s/pkgc", tmpdir, base, tmpdir);
	if (system(p)) {} /* best-effort */
	rmdir(tmpdir);
}

static int
write_source(const char *path, const char *src)
{
	FILE *f = fopen(path, "wb");
	if (!f) return -1;
	fputs(src, f);
	fclose(f);
	return 0;
}

static int
build_via_driver(const char *driver, const char *tmpdir, const char *src)
{
	char cmd[2048];
	/* #93 sep layout: `--sep -o <src-stem>` relocates artifacts to
	 * <stem>.sepwork/; WW_PKGCACHE is pinned under tmpdir so the shared
	 * out/.pkgcache is untouched. expect_fail rows still fail: a checker
	 * error makes w6c return nonzero regardless of artifact placement. */
	snprintf(cmd, sizeof cmd,
	    "cd %s && b='%s'; WW_PKGCACHE=%s/pkgc timeout 180 %s build --sep "
	    "-o \"${b%%.ww}\" \"$b\" 2>/dev/null",
	    tmpdir, src, tmpdir, driver);
	return runwait(cmd);
}

/* run_row — build via driver, run the binary, return exit (or -1 on
 * build failure). */
static int
run_row(const char *driver, const struct row *r, int seq)
{
	char tmpdir[256], src[512], base[64], outbin[768];
	snprintf(tmpdir, sizeof tmpdir, "/tmp/afa_%d_d_%d", getpid(), seq);
	snprintf(base,   sizeof base,   "main783");
	snprintf(src,    sizeof src,    "%s/%s.ww", tmpdir, base);
	mkdir(tmpdir, 0755);
	if (write_source(src, r->src) != 0) { cleanup_tmp(tmpdir, base); return -1; }
	int rc;
	if (build_via_driver(driver, tmpdir, src) == 0) {
		snprintf(outbin, sizeof outbin, "%s/%s", tmpdir, base);
		rc = runwait(outbin);
	} else {
		rc = -1;
	}
	cleanup_tmp(tmpdir, base);
	return rc;
}

/* build_ok — 1 iff the build succeeds (used by expect_fail rows). */
static int
build_ok(const char *driver, const struct row *r, int seq)
{
	char tmpdir[256], src[512], base[64];
	snprintf(tmpdir, sizeof tmpdir, "/tmp/afa_%d_nf_%d", getpid(), seq);
	snprintf(base,   sizeof base,   "main783");
	snprintf(src,    sizeof src,    "%s/%s.ww", tmpdir, base);
	mkdir(tmpdir, 0755);
	if (write_source(src, r->src) != 0) { cleanup_tmp(tmpdir, base); return -1; }
	int br = build_via_driver(driver, tmpdir, src);
	cleanup_tmp(tmpdir, base);
	return br == 0;
}

/* asm_byte_identical — diff cstage vs wwstage .s. Parallel trees so
 * ww_ww writing intermediates next to the source doesn't clobber the
 * cstage .s (CLAUDE.md rule 14 phase split). */
static int
asm_byte_identical(const char *cdrv, const char *wdrv, const struct row *r,
    int seq)
{
	char src[512], tdc[256], tdw[256], base[64], cs[512], ws[512];
	snprintf(tdc, sizeof tdc, "/tmp/afa_%d_c_%d", getpid(), seq);
	snprintf(tdw, sizeof tdw, "/tmp/afa_%d_w_%d", getpid(), seq);
	snprintf(base, sizeof base, "main783");
	mkdir(tdc, 0755);
	mkdir(tdw, 0755);
	snprintf(src, sizeof src, "%s/%s.ww", tdc, base);
	if (write_source(src, r->src) != 0) { cleanup_tmp(tdc, base); cleanup_tmp(tdw, base); return -1; }
	int rc = -1;
	if (build_via_driver(cdrv, tdc, src) != 0) goto out;
	snprintf(cs, sizeof cs, "%s/%s.sepwork/__root.s", tdc, base);

	snprintf(src, sizeof src, "%s/%s.ww", tdw, base);
	if (write_source(src, r->src) != 0) goto out;
	if (build_via_driver(wdrv, tdw, src) != 0) goto out;
	snprintf(ws, sizeof ws, "%s/%s.sepwork/__root.s", tdw, base);

	FILE *fc = fopen(cs, "rb");
	FILE *fw = fopen(ws, "rb");
	if (fc && fw) {
		rc = 0;
		for (;;) {
			int a = fgetc(fc);
			int b = fgetc(fw);
			if (a != b) { rc = -1; break; }
			if (a == EOF) break;
		}
	}
	if (fc) fclose(fc);
	if (fw) fclose(fw);
out:
	cleanup_tmp(tdc, base);
	cleanup_tmp(tdw, base);
	return rc;
}

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

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

	int n = (int)(sizeof rows / sizeof rows[0]);
	int total = 0, fail = 0, seq = 0;
	int wwpresent = (access(wdrv, X_OK) == 0);

	for (int i = 0; i < n; i++) {
		const struct row *r = &rows[i];

		if (r->stage_mask & STAGE_CS) {
			total++;
			if (r->expect_fail) {
				if (build_ok(cdrv, r, seq++)) {
					fprintf(stderr, "amp_fn_assign[cs][%s]: built but expected reject\n",
					    r->label);
					fail++;
				}
			} else {
				int got = run_row(cdrv, r, seq++);
				if (got != r->want_exit) {
					fprintf(stderr, "amp_fn_assign[cs][%s]: exit=%d want=%d\n",
					    r->label, got, r->want_exit);
					fail++;
				}
			}
		}

		if (wwpresent && (r->stage_mask & STAGE_WW)) {
			total++;
			if (r->expect_fail) {
				if (build_ok(wdrv, r, seq++)) {
					fprintf(stderr, "amp_fn_assign[ww][%s]: built but expected reject\n",
					    r->label);
					fail++;
				}
			} else {
				int got = run_row(wdrv, r, seq++);
				if (got != r->want_exit) {
					fprintf(stderr, "amp_fn_assign[ww][%s]: exit=%d want=%d\n",
					    r->label, got, r->want_exit);
					fail++;
				}
				if (r->byte_id) {
					total++;
					if (asm_byte_identical(cdrv, wdrv, r, seq++) != 0) {
						fprintf(stderr, "amp_fn_assign[byte-id][%s]: cstage vs wwstage asm differs\n",
						    r->label);
						fail++;
					}
				}
			}
		}
	}

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