/*
 * Phase-8 marker for ET_DYN linking on the ww side: a green run means
 * the ww-side linker emits PT_INTERP/PT_DYNAMIC binaries byte-for-byte
 * identical to the C linker on the same inputs — i.e. the dynamic
 * linking story is fully ported. The input is generated privately so the
 * platform gate owns its complete source and artifact lifecycle.
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.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(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;
}

int
main(void)
{
	const char *bin = absbin();
	if (!bin) return 1;

	char cwd[1024];
	if (getcwd(cwd, sizeof cwd) == NULL) return 1;

	const char *libdir = NULL;
	if (access("/usr/lib/libc.so.6", 0) == 0)
		libdir = "/usr/lib";
	else if (access("/lib/x86_64-linux-gnu/libc.so.6", 0) == 0)
		libdir = "/lib/x86_64-linux-gnu";
	else if (access("/lib64/libc.so.6", 0) == 0)
		libdir = "/lib64";
	if (libdir == NULL) {
		puts("w6l_ww-dyn: no libc.so.6 on this system — skipping");
		return 77;
	}

	char td[] = "/tmp/wwld_XXXXXX";
	if (mkdtemp(td) == NULL) {
		perror("w6l_ww-dyn mkdtemp");
		return 1;
	}

	/* #93 sep layout: build an explicit command source via `ww build`,
	 * then independently link <stem>.sepwork/__root.o with both linkers.
	 * The direct getpid call guarantees one dynamic libc relocation. */
	char cmd[4096], src[256], stem[256], scratch[320];
	char obj[384], co[256], wo[256];
	snprintf(src, sizeof src, "%s/dyn.ww", td);
	snprintf(stem, sizeof stem, "%s/built", td);
	snprintf(scratch, sizeof scratch, "%s.sepwork", stem);
	snprintf(obj, sizeof obj, "%s/__root.o", scratch);
	snprintf(co, sizeof co, "%s/c", td);
	snprintf(wo, sizeof wo, "%s/w", td);

	int rc = 0;
	FILE *f = fopen(src, "wb");
	if (f == NULL) {
		fprintf(stderr, "w6l_ww-dyn FAIL: cannot create generated source\n");
		rc = 1;
		goto cleanup;
	}
	fputs("package main;\n"
	    "@symbol(\"getpid\") fn cgetpid() i32;\n"
	    "export fn main() i32 = {\n"
	    "\tif (cgetpid() < 0) { return 1; };\n"
	    "\treturn 0;\n"
	    "};\n", f);
	int writebad = ferror(f);
	if (fclose(f) != 0) writebad = 1;
	if (writebad) {
		fprintf(stderr, "w6l_ww-dyn FAIL: cannot write generated source\n");
		rc = 1;
		goto cleanup;
	}

	snprintf(cmd, sizeof cmd,
	    "%s/ww build -o %s %s -L %s -l c >/dev/null 2>&1",
	    bin, stem, src, libdir);
	if (runwait(cmd) != 0) {
		fprintf(stderr, "w6l_ww-dyn FAIL: cannot build generated command\n");
		rc = 1;
		goto cleanup;
	}

	snprintf(cmd, sizeof cmd,
	    "%s/w6l -o %s %s -L %s "
	    "-l c %s/out/lib/libwwrt.a 2>/dev/null",
	    bin, co, obj, libdir, cwd);
	if (runwait(cmd) != 0) {
		fprintf(stderr, "w6l_ww-dyn FAIL: C w6l errored\n");
		rc = 1;
		goto cleanup;
	}

	snprintf(cmd, sizeof cmd,
	    "%s/w6l_ww -o %s %s -L %s "
	    "-l c %s/out/lib/libwwrt.a 2>/dev/null",
	    bin, wo, obj, libdir, cwd);
	if (runwait(cmd) != 0) {
		fprintf(stderr, "w6l_ww-dyn FAIL: ww w6l errored\n");
		rc = 1;
		goto cleanup;
	}

	char *bc = NULL, *bw = NULL;
	size_t nc = 0, nw = 0;
	if (slurp(co, &bc, &nc) < 0 || slurp(wo, &bw, &nw) < 0) {
		fprintf(stderr, "w6l_ww-dyn FAIL: cannot read outputs\n");
		rc = 1;
	} else if (nc == 0) {
		fprintf(stderr, "w6l_ww-dyn FAIL: empty outputs\n");
		rc = 1;
	} else if (nc != nw || memcmp(bc, bw, nc) != 0) {
		fprintf(stderr, "w6l_ww-dyn FAIL: C %zu vs ww %zu bytes\n",
		    nc, nw);
		rc = 1;
	} else if (runwait(co) != 0 || runwait(wo) != 0) {
		fprintf(stderr, "w6l_ww-dyn FAIL: linked command did not run\n");
		rc = 1;
	} else {
		printf("w6l_ww-dyn: byte-identical to C w6l on generated command "
		    "(PT_INTERP + PT_DYNAMIC + .rela.plt + .gnu.version_r, "
		    "%zu bytes)\n", nc);
	}
	free(bc); free(bw);

cleanup:
	/* `ww build` retains this exact mkdtemp-owned scratch child. */
	snprintf(cmd, sizeof cmd, "rm -rf -- %s", scratch);
	int cleanfail = runwait(cmd) != 0;
	if (unlink(src) != 0 && errno != ENOENT) {
		perror(src);
		cleanfail = 1;
	}
	if (unlink(stem) != 0 && errno != ENOENT) {
		perror(stem);
		cleanfail = 1;
	}
	if (unlink(co) != 0 && errno != ENOENT) {
		perror(co);
		cleanfail = 1;
	}
	if (unlink(wo) != 0 && errno != ENOENT) {
		perror(wo);
		cleanfail = 1;
	}
	if (rmdir(td) != 0) {
		perror(td);
		cleanfail = 1;
	}
	if (cleanfail && rc == 0)
		rc = 1;
	return rc;
}