/*
 * 799_tuple_sret_receive — project #10 Fold B (wide tuple-return / sret,
 * RECEIVE side). Fold A (798) made the CALLEE emit an over-capacity tuple
 * return (> 4 GP / > 2 SSE eightbytes) via sret, but every receive site
 * stayed LOUD-STOPPED, so such a fn was not yet usefully callable. Fold B
 * wires the call/receive end:
 *   - single-var-let  `let t = f();`     — t's slot IS the sret dest; the
 *                                           callee writes the whole tuple
 *                                           there, t.0/t.1 read by offset.
 *   - destructure     `let (a, b) = f();` — the callee sret's into the
 *                                           @sretscr slot, then each element
 *                                           is copied out to its binding at
 *                                           the SAME packed offset the SEND
 *                                           wrote (foff += element size).
 *   - reassign        `t = f();`          — same as single-var, into t's slot.
 *   - return-forward  `return f();`       — outer @sretarg threads to inner.
 *
 * THIS IS THE RUNTIME NET Fold A deferred: byte-id alone is blind to a
 * receive that lays the elements out at a different offset than the SEND
 * (both stages would be wrong the same way). Each row both (a) RUNS the
 * round-trip under cstage and asserts the data arrives intact, and (b)
 * asserts w6c vs w6c_ww .s byte-identity (rule-10). The shape is the
 * bytes.cut target — ([]u8, []u8) = 6 GP eightbytes, over the 4-GP cap.
 *
 * Data is read back by INDEXING the slice elements (t.0[i] / a[i]); the
 * destructure row also asserts len() on its bindings. NOTE: len(t.N) on a
 * tuple-element slice is a SEPARATE, pre-existing N_DOT-tuple+len
 * composition bug (reads .ptr, not .len) orthogonal to the sret receive —
 * it is deliberately NOT exercised here (filed for follow-up).
 *
 * GATE POLARITY: must stay GREEN. A wrong exit means the receive lays the
 * tuple out inconsistently with the SEND (silent corruption); a byte-id
 * FAIL means cstage and wwstage diverged on the receive (rule-10).
 */
#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_exit; };

static const struct row rows[] = {
	/* (a) destructure round-trip: bindings carry both halves; len() on a
	 * destructured binding works, and indexing reads the right bytes. */
	{ "destructure",
	  "package main;\n"
	  "fn mk(a: []u8, b: []u8) ([]u8, []u8) = { return (a, b); };\n"
	  "export fn main() i32 = {\n"
	  "	let buf: [8]u8 = [10u8, 11u8, 12u8, 13u8, 20u8, 21u8, 22u8, 23u8];\n"
	  "	let x: []u8 = buf[0:4];\n"
	  "	let y: []u8 = buf[4:8];\n"
	  "	let (a, b) = mk(x, y);\n"
	  "	if (len(a) != 4) { return 1; };\n"
	  "	if (len(b) != 4) { return 2; };\n"
	  "	if (a[0] != 10u8) { return 3; };\n"
	  "	if (a[3] != 13u8) { return 4; };\n"
	  "	if (b[0] != 20u8) { return 5; };\n"
	  "	if (b[3] != 23u8) { return 6; };\n"
	  "	return 0;\n"
	  "};\n", 0 },
	/* (b) single-var-let + positional field read (t.0 / t.1 by offset,
	 * indexed). Locks that the whole tuple materialises in t's slot. */
	{ "single_var_let",
	  "package main;\n"
	  "fn mk(a: []u8, b: []u8) ([]u8, []u8) = { return (a, b); };\n"
	  "export fn main() i32 = {\n"
	  "	let buf: [8]u8 = [10u8, 11u8, 12u8, 13u8, 20u8, 21u8, 22u8, 23u8];\n"
	  "	let x: []u8 = buf[0:4];\n"
	  "	let y: []u8 = buf[4:8];\n"
	  "	let t = mk(x, y);\n"
	  "	if (t.0[0] != 10u8) { return 1; };\n"
	  "	if (t.0[3] != 13u8) { return 2; };\n"
	  "	if (t.1[0] != 20u8) { return 3; };\n"
	  "	if (t.1[3] != 23u8) { return 4; };\n"
	  "	return 0;\n"
	  "};\n", 0 },
	/* (c) return-forward: outer fn forwards inner's over-cap tuple via the
	 * shared @sretarg (cg_sret_forward), no intermediate materialise. */
	{ "return_forward",
	  "package main;\n"
	  "fn mk(a: []u8, b: []u8) ([]u8, []u8) = { return (a, b); };\n"
	  "fn fwd(a: []u8, b: []u8) ([]u8, []u8) = { return mk(a, b); };\n"
	  "export fn main() i32 = {\n"
	  "	let buf: [8]u8 = [10u8, 11u8, 12u8, 13u8, 20u8, 21u8, 22u8, 23u8];\n"
	  "	let x: []u8 = buf[0:4];\n"
	  "	let y: []u8 = buf[4:8];\n"
	  "	let (a, b) = fwd(x, y);\n"
	  "	if (len(a) != 4) { return 1; };\n"
	  "	if (a[0] != 10u8) { return 2; };\n"
	  "	if (b[3] != 23u8) { return 3; };\n"
	  "	return 0;\n"
	  "};\n", 0 },
	/* (d) whole-tuple reassign `t = f();` into an existing slot. */
	{ "reassign",
	  "package main;\n"
	  "fn mk(a: []u8, b: []u8) ([]u8, []u8) = { return (a, b); };\n"
	  "export fn main() i32 = {\n"
	  "	let buf: [8]u8 = [10u8, 11u8, 12u8, 13u8, 20u8, 21u8, 22u8, 23u8];\n"
	  "	let x: []u8 = buf[0:4];\n"
	  "	let y: []u8 = buf[4:8];\n"
	  "	let t = mk(x, y);\n"
	  "	t = mk(y, x);\n"
	  "	if (t.0[0] != 20u8) { return 1; };\n"
	  "	if (t.1[0] != 10u8) { return 2; };\n"
	  "	return 0;\n"
	  "};\n", 0 },
	{ NULL, NULL, 0 }
};

static int
slurp_eq(const char *a, const char *b)
{
	FILE *fa = fopen(a, "rb");
	FILE *fb = fopen(b, "rb");
	if (!fa || !fb) { if (fa) fclose(fa); if (fb) fclose(fb); return -1; }
	int rc = 0;
	for (;;) {
		int ca = fgetc(fa);
		int cb = fgetc(fb);
		if (ca != cb) { rc = -1; break; }
		if (ca == EOF) break;
	}
	fclose(fa); fclose(fb);
	return rc;
}

int
main(void)
{
	const char *bin = getenv("BIN");
	if (!bin) bin = "out/bin";
	char absbin[1024];
	if (bin[0] != '/') {
		char cwd[1024];
		if (getcwd(cwd, sizeof cwd) == NULL) return 1;
		snprintf(absbin, sizeof absbin, "%s/%s", cwd, bin);
		bin = absbin;
	}

	char w6c[1100], w6c_ww[1100];
	snprintf(w6c, sizeof w6c, "%s/w6c", bin);
	snprintf(w6c_ww, sizeof w6c_ww, "%s/w6c_ww", bin);
	if (access(w6c_ww, X_OK) != 0) {
		fprintf(stderr, "tuple_sret_receive: w6c_ww missing — cannot run "
		    "the cs==ww byte-id gate\n");
		return 1;
	}

	int n = 0, fail = 0;
	for (int i = 0; rows[i].src; i++, n++) {
		char src[64];
		snprintf(src, sizeof src, "/tmp/wwtsr_%d_%d.ww", getpid(), i);
		FILE *f = fopen(src, "wb");
		if (f == NULL) { fail++; continue; }
		fputs(rows[i].src, f);
		fclose(f);

		/* (a) cstage build + run in a scratch dir. */
		char tmpdir[64];
		snprintf(tmpdir, sizeof tmpdir, "/tmp/wwtsr_%d_d_%d", getpid(), i);
		mkdir(tmpdir, 0755);

		char cmd[2048];
		snprintf(cmd, sizeof cmd, "cd %s && %s/ww build %s",
		    tmpdir, bin, src);
		if (runwait(cmd) != 0) {
			fprintf(stderr, "row[%s]: cstage build failed\n",
			    rows[i].label);
			fail++;
			unlink(src); rmdir(tmpdir);
			continue;
		}

		char outbin[128];
		const char *base = strrchr(src, '/');
		base = base ? base + 1 : src;
		snprintf(outbin, sizeof outbin, "%s/%s", tmpdir, base);
		char *dot = strrchr(outbin, '.');
		if (dot && strcmp(dot, ".ww") == 0) *dot = '\0';

		int got = runwait(outbin);
		if (got != rows[i].want_exit) {
			fprintf(stderr, "row[%s]: cstage exit %d, want %d\n",
			    rows[i].label, got, rows[i].want_exit);
			fail++;
		}
		unlink(outbin); rmdir(tmpdir);

		/* (b) cs==ww byte-id gate. */
		char cs_s[64], ws_s[64];
		snprintf(cs_s, sizeof cs_s, "/tmp/wwtsr_%d_%d_cs.s", getpid(), i);
		snprintf(ws_s, sizeof ws_s, "/tmp/wwtsr_%d_%d_ww.s", getpid(), i);

		snprintf(cmd, sizeof cmd, "%s -o %s %s 2>/dev/null", w6c, cs_s, src);
		if (runwait(cmd) != 0) {
			fprintf(stderr, "row[%s]: w6c failed\n", rows[i].label);
			fail++; unlink(src); continue;
		}
		snprintf(cmd, sizeof cmd, "%s -o %s %s 2>/dev/null",
		    w6c_ww, ws_s, src);
		if (runwait(cmd) != 0) {
			fprintf(stderr, "row[%s]: w6c_ww failed\n", rows[i].label);
			fail++; unlink(src); unlink(cs_s); continue;
		}
		if (slurp_eq(cs_s, ws_s) != 0) {
			fprintf(stderr, "row[%s]: cstage/wwstage .s DIFFER "
			    "(rule-10 byte-id violation)\n", rows[i].label);
			fail++;
		}
		unlink(src); unlink(cs_s); unlink(ws_s);
	}

	if (fail) {
		fprintf(stderr, "%d/%d tuple-sret-receive tests failed\n", fail, n);
		return 1;
	}
	printf("tuple_sret_receive: %d/%d ok (cstage run + cs==ww byte-id)\n",
	    n, n);
	return 0;
}