/*
 * 831_match_field_inplace — match on a tagged-union struct-FIELD
 * scrutinee. wwstage cgmatch reads an addressable BP-relative field
 * (`match (b.t)`, b a local VALUE struct) IN PLACE at base.off +
 * field.offset, dispatching off the field's own slot — no @match_spill
 * copy. Verbatim mirror of cstage N_MATCH's in-place arm
 * (cmd/w6c/cgen.c:10241-10296). Task #25 (M1).
 *
 * Pre-fix (wwstage): the non-ident cgmatch branch unconditionally
 * spilled ANY non-ident scrutinee — including an addressable field —
 * into @match_spill (+16B scratch → frame TEXT $48). cstage read the
 * field where it lives (TEXT $32). Both stages were runtime-correct
 * (ken's battery), so this was a latent rule-10 leanness gap, not a
 * miscompile; the fix aligns wwstage DOWN to cstage so both emit
 * byte-identical asm.
 *
 * Predicate (copied from cstage): in-place iff the scrutinee is an
 * N_DOT whose lhs is a BARE N_IDENT with a stamped type, that type
 * chases to TY_STRUCT, and the field resolves by name. Everything else
 * — a *ptr-field base (`match (h.t)`, h:*struct, chases to TY_PTR so
 * the by-name scan misses), a plain-local tagged ident, a call-result
 * scrutinee — keeps its existing (in-place-ident / spill) path,
 * unchanged.
 *
 * What this table pins, per row, across BOTH driver stages plus a
 * cstage-vs-wwstage asm byte-identity check:
 *   (a) local VALUE-struct tagged field   [NEW in-place arm]
 *   (b) *ptr-struct tagged field          [stays on spill — TY_PTR]
 *   (c) plain-local tagged ident          [unchanged in-place-ident]
 *   (d) call-result tagged scrutinee      [spill]
 *   (e) bool->int payload remap on a field [width: 1-word variants]
 *   (f) str-payload (24B box) on a field   [width: 3-word variant]
 *
 * The boundary, not just the new arm, is the subject: a regression
 * that mis-routed (b)/(c)/(d) into the in-place arm, or failed to route
 * (a)/(e)/(f) there, would break either the runtime exit code or the
 * byte-identity. The $48->$32 frame convergence itself is ken's
 * authoritative byte-id bind; a runtime test cannot observe frame size.
 */
#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;
}

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

static const struct row rows[] = {
	/* (a) NEW in-place arm: local VALUE struct, field reassigned to
	 * the int variant, matched in place. Returns 42. */
	{ "local_field_int_inplace",
	  "package main;\n"
	  "type box = struct { t: (int | bool), n: int };\n"
	  "fn main() i32 = {\n"
	  "    let b: box = box { t = 0, n = 5 };\n"
	  "    b.t = 42;\n"
	  "    match (b.t) {\n"
	  "    case let n: int => return n: i32;\n"
	  "    case bool => return 1;\n"
	  "    };\n"
	  "};\n",
	  42 },
	/* (b) *ptr-struct field: base chases to TY_PTR, the by-name scan
	 * misses, scrutinee falls to the spill path — exactly as cstage,
	 * no separate deref guard. Returns 9. */
	{ "ptr_field_stays_spill",
	  "package main;\n"
	  "type box = struct { t: (int | bool), n: int };\n"
	  "fn pick(h: *box) i32 = {\n"
	  "    match (h.t) {\n"
	  "    case let n: int => return n: i32;\n"
	  "    case bool => return 1;\n"
	  "    };\n"
	  "};\n"
	  "fn main() i32 = {\n"
	  "    let b: box = box { t = 9, n = 5 };\n"
	  "    return pick(&b);\n"
	  "};\n",
	  9 },
	/* (c) plain-local tagged ident: unchanged in-place-ident path
	 * (not N_DOT). Returns 5. */
	{ "plain_local_ident",
	  "package main;\n"
	  "fn main() i32 = {\n"
	  "    let t: (int | bool) = 5;\n"
	  "    match (t) {\n"
	  "    case let n: int => return n: i32;\n"
	  "    case bool => return 1;\n"
	  "    };\n"
	  "};\n",
	  5 },
	/* (d) call-result tagged scrutinee: not N_DOT, keeps the spill
	 * path. Returns 7. */
	{ "call_result_spill",
	  "package main;\n"
	  "fn mk(b: bool) (int | bool) = {\n"
	  "    if (b) { return 7; };\n"
	  "    return false;\n"
	  "};\n"
	  "fn main() i32 = {\n"
	  "    match (mk(true)) {\n"
	  "    case let n: int => return n: i32;\n"
	  "    case bool => return 1;\n"
	  "    };\n"
	  "};\n",
	  7 },
	/* (e) width: a field whose variant remaps from bool to int. The
	 * in-place arm reads tag + one payload word at the field slot;
	 * the int arm also reads a sibling field (b.n) to prove the
	 * surrounding struct frame is undisturbed. Returns 7 + 5 = 12. */
	{ "field_bool_to_int_remap",
	  "package main;\n"
	  "type box = struct { t: (int | bool), n: int };\n"
	  "fn main() i32 = {\n"
	  "    let b: box = box { t = true, n = 5 };\n"
	  "    b.t = 7;\n"
	  "    match (b.t) {\n"
	  "    case let n: int => return (n + b.n): i32;\n"
	  "    case bool => return 1;\n"
	  "    };\n"
	  "};\n",
	  12 },
	/* (f) width: a 24B str-payload variant read in place at the
	 * field slot (tag@+0, .ptr@+8, .len@+16). Returns len("hello")
	 * = 5. */
	{ "field_str_payload_24B",
	  "package main;\n"
	  "type box = struct { t: (str | int), n: int };\n"
	  "fn main() i32 = {\n"
	  "    let b: box = box { t = 0, n = 5 };\n"
	  "    b.t = \"hello\";\n"
	  "    match (b.t) {\n"
	  "    case let s: str => return len(s): i32;\n"
	  "    case int => return 99;\n"
	  "    };\n"
	  "};\n",
	  5 },
};

static int
run_driver(const char *driver, const struct row *r, int i)
{
	char src[128], tmpdir[64], outbin[128], rmcmd[160], cmd[1024];
	snprintf(tmpdir, sizeof tmpdir, "/tmp/wcmfi_%d_d_%d", getpid(), i);
	mkdir(tmpdir, 0755);
	snprintf(src, sizeof src, "%s/wcmfi_%d_%d.ww", tmpdir, getpid(), i);
	snprintf(outbin, sizeof outbin, "%s/wcmfi_%d_%d", tmpdir, getpid(), i);
	snprintf(rmcmd, sizeof rmcmd, "rm -rf %s", tmpdir);

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

	snprintf(cmd, sizeof cmd, "%s build -o %s %s", driver, outbin, src);
	if (runwait(cmd) != 0) {
		fprintf(stderr, "row[%s]: build via %s failed\n",
		    r->label, driver);
		runwait(rmcmd);
		return -1;
	}

	int got = runwait(outbin);

	runwait(rmcmd);
	return got;
}

/* asm_byte_identical — the whole point of M1 is that wwstage's frame
 * stops bloating for an addressable field scrutinee, so the cstage vs
 * wwstage text output must match byte-for-byte on every row. */
static int
asm_byte_identical(const char *bin, const struct row *r, int i)
{
	char src[64], cs[64], ws[64], cmd[1024];
	snprintf(src, sizeof src, "/tmp/wcmfi_asm_%d_%d.ww", getpid(), i);
	snprintf(cs,  sizeof cs,  "/tmp/wcmfi_asm_%d_%d_c.s", getpid(), i);
	snprintf(ws,  sizeof ws,  "/tmp/wcmfi_asm_%d_%d_w.s", getpid(), i);

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

	snprintf(cmd, sizeof cmd, "%s/w6c -o %s %s 2>/dev/null", bin, cs, src);
	if (runwait(cmd) != 0) {
		fprintf(stderr, "row[%s]: w6c errored\n", r->label);
		unlink(src);
		return -1;
	}
	snprintf(cmd, sizeof cmd, "%s/w6c_ww -o %s %s 2>/dev/null",
	    bin, ws, src);
	if (runwait(cmd) != 0) {
		fprintf(stderr, "row[%s]: w6c_ww errored\n", r->label);
		unlink(src); unlink(cs);
		return -1;
	}

	FILE *fc = fopen(cs, "rb");
	FILE *fw = fopen(ws, "rb");
	int rc = 0;
	if (!fc || !fw) {
		rc = -1;
	} else {
		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);
	if (rc != 0)
		fprintf(stderr, "row[%s]: cstage vs wwstage asm differs\n",
		    r->label);
	unlink(src); unlink(cs); unlink(ws);
	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 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, "match_field_inplace: 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,
				    "match_field_inplace[%s][%s]: exit=%d want=%d\n",
				    drivers[d].name, rows[i].label,
				    got, rows[i].want);
				fail++;
			}
		}
	}

	if (access(wdrv, X_OK) == 0) {
		for (int i = 0; i < n; i++) {
			total++;
			if (asm_byte_identical(bin, &rows[i], i) != 0)
				fail++;
		}
	}

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