/*
 * 989_pkgcache_concurrent_run — concurrent shared-cache build-correctness
 * smoke (#104). N distinct root programs that all `import shared` are built
 * CONCURRENTLY into ONE shared WW_PKGCACHE; every resulting binary must be
 * byte-IDENTICAL to a reference built in ISOLATION (private cache) and run to
 * its expected exit. This guards that concurrent `ww build --sep` sharing one
 * out/.pkgcache produces correct, deterministic binaries — a regression guard
 * for the cache subsystem under contention (store crash, lock bug, wrong-key
 * copy, etc.).
 *
 * It does NOT prove the temp+rename store is atomic against torn reads: with
 * content-keying every concurrent cold build MISSES at lookup and STORES (it
 * never HIT-reads a mid-store entry), so the torn-read window is not forced
 * here. That race is closed by construction at the cache_store fix site; the
 * deferred white-box guard is TASK #105.
 *
 * Both driver stages (rule 10): the cs and ww references are byte-identical.
 * Light wwstage-driver test (CLAUDE.md rule 14): all outputs + caches live
 * under a private /tmp tree, so it is parallel-safe and off every byte-id /
 * bootstrap gate. Models 989_pkgcache_run conventions.
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/wait.h>
#include <sys/stat.h>

#define NPROG 4
#define BASE_EXIT 7	/* shared.v() == 7; rootI returns 7 + I */

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

static int
slurp(const char *path, char **outbuf, size_t *outlen)
{
	FILE *f = fopen(path, "rb");
	if (!f) return -1;
	fseek(f, 0, SEEK_END);
	long n = ftell(f);
	fseek(f, 0, SEEK_SET);
	if (n < 0) { fclose(f); return -1; }
	char *b = malloc((size_t)n + 1);
	if (!b) { fclose(f); return -1; }
	if (fread(b, 1, (size_t)n, f) != (size_t)n) { free(b); fclose(f); return -1; }
	b[n] = '\0';
	fclose(f);
	*outbuf = b;
	*outlen = (size_t)n;
	return 0;
}

static int
files_eq(const char *a, const char *b)
{
	char *ba = NULL, *bb = NULL;
	size_t na = 0, nb = 0;
	if (slurp(a, &ba, &na) < 0 || slurp(b, &bb, &nb) < 0) {
		free(ba); free(bb);
		return -1;
	}
	int eq = (na == nb && memcmp(ba, bb, na) == 0);
	free(ba); free(bb);
	return eq ? 0 : 1;
}

static const char *shared_src =
	"package shared;\n"
	"export fn v() i32 = { return 7; };\n";

int
main(void)
{
	const char *bin = absbin();
	if (!bin) return 1;
	int fail = 0;
	char td[64], cmd[8192], batch[32768];
	char sharedww[1024];

	snprintf(td, sizeof td, "/tmp/wwconc_%d", getpid());
	snprintf(cmd, sizeof cmd, "rm -rf %s", td);
	runwait(cmd);
	snprintf(cmd, sizeof cmd, "mkdir -p %s/shared", td);
	runwait(cmd);

	snprintf(sharedww, sizeof sharedww, "%s/shared/shared.ww", td);
	if (write_file(sharedww, shared_src)) { fail++; goto out; }

	/* N distinct roots, each importing the one shared pkg. Distinct return
	 * (7 + I) so each program — and so each clean binary — is distinguishable,
	 * while the contended cache entry (shared) is common to all. */
	for (int i = 0; i < NPROG; i++) {
		char rootww[1024], src[256];
		snprintf(rootww, sizeof rootww, "%s/root%d.ww", td, i);
		snprintf(src, sizeof src,
		    "package main;\nimport shared;\n"
		    "fn main() i32 = { return shared.v() + %d; };\n", i);
		if (write_file(rootww, src)) { fail++; goto out; }
	}

	struct { const char *drv, *tag; } stg[] = {
		{ "ww",    "cs" },
		{ "ww_ww", "ww" },
	};

	for (int s = 0; s < 2; s++) {
		const char *drv = stg[s].drv, *tag = stg[s].tag;
		char shcache[1024];
		snprintf(shcache, sizeof shcache, "%s/cache.%s", td, tag);

		/* References: each rootI built ISOLATED (private cache, no contention)
		 * = the clean baseline bytes a concurrent build must reproduce. */
		for (int i = 0; i < NPROG; i++) {
			char refcache[1024], refprog[1024], refscr[1024], rootww[1024];
			snprintf(refcache, sizeof refcache, "%s/refc.%s.%d", td, tag, i);
			snprintf(refprog, sizeof refprog, "%s/ref.%s.%d", td, tag, i);
			snprintf(refscr, sizeof refscr, "%s/ref.%s.%d.sepwork", td, tag, i);
			snprintf(rootww, sizeof rootww, "%s/root%d.ww", td, i);
			snprintf(cmd, sizeof cmd,
			    "rm -rf %s %s; WW_PKGCACHE='%s' timeout 240 %s/%s build --sep "
			    "-o %s %s >/dev/null 2>&1",
			    refscr, refcache, refcache, bin, drv, refprog, rootww);
			if (runwait(cmd) != 0) {
				fprintf(stderr, "concur FAIL[%s]: reference build %d failed\n",
				    drv, i);
				fail++;
			}
			if (runwait(refprog) != BASE_EXIT + i) {
				fprintf(stderr, "concur FAIL[%s]: reference %d wrong exit\n",
				    drv, i);
				fail++;
			}
		}

		/* Fresh shared cache so every build in the batch MISS-stores `shared`
		 * concurrently → write contention on shared/P.{wwi,o,key}. Distinct
		 * per-prog output so every binary can be verified, not just one. */
		snprintf(cmd, sizeof cmd, "rm -rf %s", shcache);
		runwait(cmd);

		size_t off = 0;
		off += (size_t)snprintf(batch + off, sizeof batch - off,
		    "export WW_PKGCACHE='%s'; ", shcache);
		for (int i = 0; i < NPROG; i++) {
			off += (size_t)snprintf(batch + off, sizeof batch - off,
			    "( rm -rf %s/c.%s.%d.sepwork; timeout 240 %s/%s build "
			    "--sep -o %s/c.%s.%d %s/root%d.ww >/dev/null 2>&1 ) & ",
			    td, tag, i, bin, drv,
			    td, tag, i, td, i);
		}
		off += (size_t)snprintf(batch + off, sizeof batch - off, "wait");
		if (off >= sizeof batch) {
			fprintf(stderr, "concur FAIL: batch cmd truncated\n");
			fail++; goto out;
		}
		runwait(batch);

		for (int i = 0; i < NPROG; i++) {
			char prog[1024], refprog[1024];
			snprintf(prog, sizeof prog, "%s/c.%s.%d", td, tag, i);
			snprintf(refprog, sizeof refprog, "%s/ref.%s.%d", td, tag, i);
			if (runwait(prog) != BASE_EXIT + i) {
				fprintf(stderr, "concur FAIL[%s]: concurrent prog i=%d "
				    "wrong/failed exit\n", drv, i);
				fail++;
			}
			if (files_eq(prog, refprog) != 0) {
				fprintf(stderr, "concur FAIL[%s]: concurrent binary i=%d "
				    "!= isolated reference\n", drv, i);
				fail++;
			}
		}
	}

	/* rule 10: the cs and ww isolated references are byte-identical. */
	for (int i = 0; i < NPROG; i++) {
		char a[1024], b[1024];
		snprintf(a, sizeof a, "%s/ref.cs.%d", td, i);
		snprintf(b, sizeof b, "%s/ref.ww.%d", td, i);
		if (files_eq(a, b) != 0) {
			fprintf(stderr, "concur FAIL: cs != ww reference %d (rule 10)\n", i);
			fail++;
		}
	}

out:
	snprintf(cmd, sizeof cmd, "rm -rf %s", td);
	runwait(cmd);
	if (fail) {
		fprintf(stderr, "concur: %d check(s) failed\n", fail);
		return 1;
	}
	printf("concur: %d concurrent --sep builds sharing one cache, both stages "
	    "— every binary byte-identical to its isolated reference + correct run; "
	    "cs==ww references (rule 10)\n", NPROG);
	return 0;
}