/*
 * 995_self_rebuild — the wwstage rebuilds itself.
 *
 * Drives ww_ww (the ww-side driver, which shells to w6c_ww/w6a_ww/w6l_ww)
 * over each wwstage tool's source and diffs the result byte-for-byte
 * against the cstage-built binary in $BIN. A green run means the
 * toolchain can recompile itself without touching cc, modulo the
 * cold-start binary — which is the v1.0 lock from PLAN.md.
 *
 * This is stricter than `make bootstrap`: that loop only proves the
 * wwdump cgen self-stabilises; this proves every wwstage tool round-
 * trips through the wwstage pipeline.
 */
#include <stdio.h>
#include <stdlib.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;
}

static const char *
absbin(void)
{
	const char *b = getenv("BIN");
	if (!b) b = "out/bin";
	if (b[0] == '/') return b;
	static char buf[2048];
	char cwd[1024];
	if (getcwd(cwd, sizeof cwd) == NULL) return NULL;
	snprintf(buf, sizeof buf, "%s/%s", cwd, b);
	return buf;
}

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;
}

/* Each tool builds via `ww_ww build -I <local> -I lib/ww -I selfhost/cmd/wcc src`.
 * lib/ww holds the language introspection (lex/tok/ast/parse/typ/sym);
 * selfhost/cmd/wcc holds the compiler internals (mem/check/cgen*).
 * Some tools have a local module dir (w6a, w6l with sibling .ww files).
 * inc_local is "" for tools without one (w6c, ww, wwdump).
 */
static int
rebuild_one(const char *bin, const char *cwd, const char *tool,
    const char *src_rel, const char *inc_local)
{
	char workdir[64];
	snprintf(workdir, sizeof workdir, "/tmp/wwsr_%d_%s", getpid(), tool);
	char cmd[4096];
	snprintf(cmd, sizeof cmd, "rm -rf %s && mkdir -p %s", workdir, workdir);
	if (runwait(cmd) != 0) return -1;

	if (inc_local && inc_local[0]) {
		snprintf(cmd, sizeof cmd,
		    "cd %s && %s/ww_ww build -I %s/%s -I %s/lib/ww -I %s/lib/ww/lex -I %s/lib/ww/parse -I %s/selfhost/cmd/wcc "
		    "%s/%s >/dev/null 2>&1",
		    workdir, bin, cwd, inc_local, cwd, cwd, cwd, cwd, cwd, src_rel);
	} else {
		snprintf(cmd, sizeof cmd,
		    "cd %s && %s/ww_ww build -I %s/lib/ww -I %s/lib/ww/lex -I %s/lib/ww/parse -I %s/selfhost/cmd/wcc "
		    "%s/%s >/dev/null 2>&1",
		    workdir, bin, cwd, cwd, cwd, cwd, cwd, src_rel);
	}
	if (runwait(cmd) != 0) {
		fprintf(stderr, "self-rebuild FAIL: ww_ww build errored on %s\n", tool);
		return -1;
	}

	char rebuilt[256], canonical[256];
	snprintf(rebuilt,   sizeof rebuilt,   "%s/main", workdir);
	snprintf(canonical, sizeof canonical, "%s/%s_ww", bin, tool);

	int rc = slurp_eq(rebuilt, canonical);
	if (rc != 0) {
		fprintf(stderr, "self-rebuild FAIL: %s rebuilt != cstage %s\n",
		    tool, canonical);
	}

	/* Leave the driver's intermediates (.s/.o/.combined.ww) next to the
	 * source — 991/992/994 read those fixtures, and `make wwstage` had
	 * already produced byte-identical copies anyway. */
	snprintf(cmd, sizeof cmd, "rm -rf %s", workdir);
	runwait(cmd);
	return rc;
}

int
main(void)
{
	const char *bin = absbin();
	if (!bin) return 1;
	char cwd[1024];
	if (getcwd(cwd, sizeof cwd) == NULL) return 1;

	struct {
		const char *tool;
		const char *src;
		const char *inc_local;
	} tools[] = {
		{ "w6c",     "selfhost/cmd/w6c/main.ww",     "" },
		{ "w6a",     "selfhost/cmd/w6a/main.ww",     "selfhost/cmd/w6a" },
		{ "w6l",     "selfhost/cmd/w6l/main.ww",     "selfhost/cmd/w6l" },
		{ "ww",     "selfhost/cmd/ww/main.ww",     "" },
		{ "wwdump", "selfhost/cmd/wwdump/main.ww", "" },
		{ NULL, NULL, NULL },
	};

	int fail = 0, n = 0;
	for (int i = 0; tools[i].tool; i++) {
		if (rebuild_one(bin, cwd, tools[i].tool, tools[i].src,
		    tools[i].inc_local) != 0)
			fail++;
		n++;
	}
	if (fail) {
		fprintf(stderr, "self-rebuild: %d/%d tool(s) diverged\n", fail, n);
		return 1;
	}
	printf("self-rebuild: %d wwstage tool(s) round-trip byte-identical "
	    "through ww_ww + w6c_ww + w6a_ww + w6l_ww\n", n);
	return 0;
}