#include "daemon-utils.h"
#include "config.h"
#include "run-command.h"
#include "strbuf.h"
#include "string-list.h"
#include "trace2.h"
#include "version.h"
#include "dir.h"
#include "date.h"

#define TR2_CAT "test-http-server"

static const char *pid_file;
static int verbose;
static int reuseaddr;

static const char test_http_auth_usage[] =
"http-server [--verbose]\n"
"           [--timeout=<n>] [--max-connections=<n>]\n"
"           [--reuseaddr] [--pid-file=<file>]\n"
"           [--listen=<host_or_ipaddr>]* [--port=<n>]\n"
;

static unsigned int timeout;

static void logreport(const char *label, const char *err, va_list params)
{
	struct strbuf msg = STRBUF_INIT;

	strbuf_addf(&msg, "[%"PRIuMAX"] %s: ", (uintmax_t)getpid(), label);
	strbuf_vaddf(&msg, err, params);
	strbuf_addch(&msg, '\n');

	fwrite(msg.buf, sizeof(char), msg.len, stderr);
	fflush(stderr);

	strbuf_release(&msg);
}

__attribute__((format (printf, 1, 2)))
static void logerror(const char *err, ...)
{
	va_list params;
	va_start(params, err);
	logreport("error", err, params);
	va_end(params);
}

__attribute__((format (printf, 1, 2)))
static void loginfo(const char *err, ...)
{
	va_list params;
	if (!verbose)
		return;
	va_start(params, err);
	logreport("info", err, params);
	va_end(params);
}

/*
 * The code in this section is used by "worker" instances to service
 * a single connection from a client.  The worker talks to the client
 * on 0 and 1.
 */

enum worker_result {
	/*
	 * Operation successful.
	 * Caller *might* keep the socket open and allow keep-alive.
	 */
	WR_OK       = 0,

	/*
	 * Various errors while processing the request and/or the response.
	 * Close the socket and clean up.
	 * Exit child-process with non-zero status.
	 */
	WR_IO_ERROR = 1<<0,

	/*
	 * Close the socket and clean up.  Does not imply an error.
	 */
	WR_HANGUP   = 1<<1,
};

/*
 * Fields from a parsed HTTP request.
 */
struct req {
	struct strbuf start_line;

	const char *method;
	const char *http_version;

	struct strbuf uri_path;
	struct strbuf query_args;

	struct string_list header_list;
	const char *content_type;
	ssize_t content_length;
};

#define REQ__INIT { \
	.start_line = STRBUF_INIT, \
	.uri_path = STRBUF_INIT, \
	.query_args = STRBUF_INIT, \
	.header_list = STRING_LIST_INIT_NODUP, \
	.content_type = NULL, \
	.content_length = -1 \
	}

static void req__release(struct req *req)
{
	strbuf_release(&req->start_line);

	strbuf_release(&req->uri_path);
	strbuf_release(&req->query_args);

	string_list_clear(&req->header_list, 0);
}

static enum worker_result send_http_error(
	int fd,
	int http_code, const char *http_code_name,
	int retry_after_seconds, struct string_list *response_headers,
	enum worker_result wr_in)
{
	struct strbuf response_header = STRBUF_INIT;
	struct strbuf response_content = STRBUF_INIT;
	struct string_list_item *h;
	enum worker_result wr;

	strbuf_addf(&response_content, "Error: %d %s\r\n",
		    http_code, http_code_name);
	if (retry_after_seconds > 0)
		strbuf_addf(&response_content, "Retry-After: %d\r\n",
			    retry_after_seconds);

	strbuf_addf  (&response_header, "HTTP/1.1 %d %s\r\n", http_code, http_code_name);
	strbuf_addstr(&response_header, "Cache-Control: private\r\n");
	strbuf_addstr(&response_header,	"Content-Type: text/plain\r\n");
	strbuf_addf  (&response_header,	"Content-Length: %d\r\n", (int)response_content.len);
	if (retry_after_seconds > 0)
		strbuf_addf(&response_header, "Retry-After: %d\r\n", retry_after_seconds);
	strbuf_addf(  &response_header,	"Server: test-http-server/%s\r\n", git_version_string);
	strbuf_addf(  &response_header, "Date: %s\r\n", show_date(time(NULL), 0, DATE_MODE(RFC2822)));
	if (response_headers)
		for_each_string_list_item(h, response_headers)
			strbuf_addf(&response_header, "%s\r\n", h->string);
	strbuf_addstr(&response_header, "\r\n");

	if (write_in_full(fd, response_header.buf, response_header.len) < 0) {
		logerror("unable to write response header");
		wr = WR_IO_ERROR;
		goto done;
	}

	if (write_in_full(fd, response_content.buf, response_content.len) < 0) {
		logerror("unable to write response content body");
		wr = WR_IO_ERROR;
		goto done;
	}

	wr = wr_in;

done:
	strbuf_release(&response_header);
	strbuf_release(&response_content);

	return wr;
}

/*
 * Read the HTTP request up to the start of the optional message-body.
 * We do this byte-by-byte because we have keep-alive turned on and
 * cannot rely on an EOF.
 *
 * https://tools.ietf.org/html/rfc7230
 *
 * We cannot call die() here because our caller needs to properly
 * respond to the client and/or close the socket before this
 * child exits so that the client doesn't get a connection reset
 * by peer error.
 */
static enum worker_result req__read(struct req *req, int fd)
{
	struct strbuf h = STRBUF_INIT;
	struct string_list start_line_fields = STRING_LIST_INIT_DUP;
	int nr_start_line_fields;
	const char *uri_target;
	const char *query;
	char *hp;
	const char *hv;

	enum worker_result result = WR_OK;

	/*
	 * Read line 0 of the request and split it into component parts:
	 *
	 *    <method> SP <uri-target> SP <HTTP-version> CRLF
	 *
	 */
	if (strbuf_getwholeline_fd(&req->start_line, fd, '\n') == EOF) {
		result = WR_OK | WR_HANGUP;
		goto done;
	}

	strbuf_trim_trailing_newline(&req->start_line);

	nr_start_line_fields = string_list_split(&start_line_fields,
						 req->start_line.buf,
						 ' ', -1);
	if (nr_start_line_fields != 3) {
		logerror("could not parse request start-line '%s'",
			 req->start_line.buf);
		result = WR_IO_ERROR;
		goto done;
	}

	req->method = xstrdup(start_line_fields.items[0].string);
	req->http_version = xstrdup(start_line_fields.items[2].string);

	uri_target = start_line_fields.items[1].string;

	if (strcmp(req->http_version, "HTTP/1.1")) {
		logerror("unsupported version '%s' (expecting HTTP/1.1)",
			 req->http_version);
		result = WR_IO_ERROR;
		goto done;
	}

	query = strchr(uri_target, '?');

	if (query) {
		strbuf_add(&req->uri_path, uri_target, (query - uri_target));
		strbuf_trim_trailing_dir_sep(&req->uri_path);
		strbuf_addstr(&req->query_args, query + 1);
	} else {
		strbuf_addstr(&req->uri_path, uri_target);
		strbuf_trim_trailing_dir_sep(&req->uri_path);
	}

	/*
	 * Read the set of HTTP headers into a string-list.
	 */
	while (1) {
		if (strbuf_getwholeline_fd(&h, fd, '\n') == EOF)
			goto done;
		strbuf_trim_trailing_newline(&h);

		if (!h.len)
			goto done; /* a blank line ends the header */

		hp = strbuf_detach(&h, NULL);
		string_list_append(&req->header_list, hp);

		/* also store common request headers as struct req members */
		if (skip_prefix(hp, "Content-Type: ", &hv)) {
			req->content_type = hv;
		} else if (skip_prefix(hp, "Content-Length: ", &hv)) {
			req->content_length = strtol(hv, &hp, 10);
		}
	}

	/*
	 * We do not attempt to read the <message-body>, if it exists.
	 * We let our caller read/chunk it in as appropriate.
	 */

done:
	string_list_clear(&start_line_fields, 0);

	/*
	 * This is useful for debugging the request, but very noisy.
	 */
	if (trace2_is_enabled()) {
		struct string_list_item *item;
		trace2_printf("%s: %s", TR2_CAT, req->start_line.buf);
		trace2_printf("%s: hver: %s", TR2_CAT, req->http_version);
		trace2_printf("%s: hmth: %s", TR2_CAT, req->method);
		trace2_printf("%s: path: %s", TR2_CAT, req->uri_path.buf);
		trace2_printf("%s: qury: %s", TR2_CAT, req->query_args.buf);
		if (req->content_length >= 0)
			trace2_printf("%s: clen: %d", TR2_CAT, req->content_length);
		if (req->content_type)
			trace2_printf("%s: ctyp: %s", TR2_CAT, req->content_type);
		for_each_string_list_item(item, &req->header_list)
			trace2_printf("%s: hdrs: %s", TR2_CAT, item->string);
	}

	return result;
}

static enum worker_result dispatch(struct req *req)
{
	return send_http_error(STDOUT_FILENO, 501, "Not Implemented", -1, NULL,
			       WR_OK | WR_HANGUP);
}

static enum worker_result worker(void)
{
	struct req req = REQ__INIT;
	char *client_addr = getenv("REMOTE_ADDR");
	char *client_port = getenv("REMOTE_PORT");
	enum worker_result wr = WR_OK;

	if (client_addr)
		loginfo("Connection from %s:%s", client_addr, client_port);

	set_keep_alive(0, logerror);

	while (1) {
		req__release(&req);

		alarm(timeout);
		wr = req__read(&req, 0);
		alarm(0);

		if (wr != WR_OK)
			break;

		wr = dispatch(&req);
		if (wr != WR_OK)
			break;
	}

	close(STDIN_FILENO);
	close(STDOUT_FILENO);

	return !!(wr & WR_IO_ERROR);
}

static int max_connections = 32;

static unsigned int live_children;

static struct child *first_child;

static struct strvec cld_argv = STRVEC_INIT;
static void handle(int incoming, struct sockaddr *addr, socklen_t addrlen)
{
	struct child_process cld = CHILD_PROCESS_INIT;

	if (max_connections && live_children >= max_connections) {
		kill_some_child(first_child);
		sleep(1);  /* give it some time to die */
		check_dead_children(first_child, &live_children, loginfo);
		if (live_children >= max_connections) {
			close(incoming);
			logerror("Too many children, dropping connection");
			return;
		}
	}

	if (addr->sa_family == AF_INET) {
		char buf[128] = "";
		struct sockaddr_in *sin_addr = (void *) addr;
		inet_ntop(addr->sa_family, &sin_addr->sin_addr, buf, sizeof(buf));
		strvec_pushf(&cld.env, "REMOTE_ADDR=%s", buf);
		strvec_pushf(&cld.env, "REMOTE_PORT=%d",
				 ntohs(sin_addr->sin_port));
#ifndef NO_IPV6
	} else if (addr->sa_family == AF_INET6) {
		char buf[128] = "";
		struct sockaddr_in6 *sin6_addr = (void *) addr;
		inet_ntop(AF_INET6, &sin6_addr->sin6_addr, buf, sizeof(buf));
		strvec_pushf(&cld.env, "REMOTE_ADDR=[%s]", buf);
		strvec_pushf(&cld.env, "REMOTE_PORT=%d",
				 ntohs(sin6_addr->sin6_port));
#endif
	}

	strvec_pushv(&cld.args, cld_argv.v);
	cld.in = incoming;
	cld.out = dup(incoming);

	if (cld.out < 0)
		logerror("could not dup() `incoming`");
	else if (start_command(&cld))
		logerror("unable to fork");
	else
		add_child(&cld, addr, addrlen, first_child, &live_children);
}

static void child_handler(int signo)
{
	/*
	 * Otherwise empty handler because systemcalls will get interrupted
	 * upon signal receipt
	 * SysV needs the handler to be rearmed
	 */
	signal(SIGCHLD, child_handler);
}

static int service_loop(struct socketlist *socklist)
{
	struct pollfd *pfd;
	int i;

	CALLOC_ARRAY(pfd, socklist->nr);

	for (i = 0; i < socklist->nr; i++) {
		pfd[i].fd = socklist->list[i];
		pfd[i].events = POLLIN;
	}

	signal(SIGCHLD, child_handler);

	for (;;) {
		int i;
		int nr_ready;
		int timeout = (pid_file ? 100 : -1);

		check_dead_children(first_child, &live_children, loginfo);

		nr_ready = poll(pfd, socklist->nr, timeout);
		if (nr_ready < 0) {
			if (errno != EINTR) {
				logerror("Poll failed, resuming: %s",
				      strerror(errno));
				sleep(1);
			}
			continue;
		}
		else if (nr_ready == 0) {
			/*
			 * If we have a pid_file, then we watch it.
			 * If someone deletes it, we shutdown the service.
			 * The shell scripts in the test suite will use this.
			 */
			if (!pid_file || file_exists(pid_file))
				continue;
			goto shutdown;
		}

		for (i = 0; i < socklist->nr; i++) {
			if (pfd[i].revents & POLLIN) {
				union {
					struct sockaddr sa;
					struct sockaddr_in sai;
#ifndef NO_IPV6
					struct sockaddr_in6 sai6;
#endif
				} ss;
				socklen_t sslen = sizeof(ss);
				int incoming = accept(pfd[i].fd, &ss.sa, &sslen);
				if (incoming < 0) {
					switch (errno) {
					case EAGAIN:
					case EINTR:
					case ECONNABORTED:
						continue;
					default:
						die_errno("accept returned");
					}
				}
				handle(incoming, &ss.sa, sslen);
			}
		}
	}

shutdown:
	loginfo("Starting graceful shutdown (pid-file gone)");
	for (i = 0; i < socklist->nr; i++)
		close(socklist->list[i]);

	return 0;
}

static int serve(struct string_list *listen_addr, int listen_port)
{
	struct socketlist socklist = { NULL, 0, 0 };

	socksetup(listen_addr, listen_port, &socklist, reuseaddr, logerror);
	if (socklist.nr == 0)
		die("unable to allocate any listen sockets on port %u",
		    listen_port);

	loginfo("Ready to rumble");

	/*
	 * Wait to create the pid-file until we've setup the sockets
	 * and are open for business.
	 */
	if (pid_file)
		write_file(pid_file, "%"PRIuMAX, (uintmax_t) getpid());

	return service_loop(&socklist);
}

/*
 * This section is executed by both the primary instance and all
 * worker instances.  So, yes, each child-process re-parses the
 * command line argument and re-discovers how it should behave.
 */

int cmd_main(int argc, const char **argv)
{
	int listen_port = 0;
	struct string_list listen_addr = STRING_LIST_INIT_NODUP;
	int worker_mode = 0;
	int i;

	trace2_cmd_name("test-http-server");
	trace2_cmd_list_config();
	trace2_cmd_list_env_vars();
	setup_git_directory_gently(NULL);

	for (i = 1; i < argc; i++) {
		const char *arg = argv[i];
		const char *v;

		if (skip_prefix(arg, "--listen=", &v)) {
			string_list_append(&listen_addr, xstrdup_tolower(v));
			continue;
		}
		if (skip_prefix(arg, "--port=", &v)) {
			char *end;
			unsigned long n;
			n = strtoul(v, &end, 0);
			if (*v && !*end) {
				listen_port = n;
				continue;
			}
		}
		if (!strcmp(arg, "--worker")) {
			worker_mode = 1;
			trace2_cmd_mode("worker");
			continue;
		}
		if (!strcmp(arg, "--verbose")) {
			verbose = 1;
			continue;
		}
		if (skip_prefix(arg, "--timeout=", &v)) {
			timeout = atoi(v);
			continue;
		}
		if (skip_prefix(arg, "--max-connections=", &v)) {
			max_connections = atoi(v);
			if (max_connections < 0)
				max_connections = 0; /* unlimited */
			continue;
		}
		if (!strcmp(arg, "--reuseaddr")) {
			reuseaddr = 1;
			continue;
		}
		if (skip_prefix(arg, "--pid-file=", &v)) {
			pid_file = v;
			continue;
		}

		fprintf(stderr, "error: unknown argument '%s'\n", arg);
		usage(test_http_auth_usage);
	}

	/* avoid splitting a message in the middle */
	setvbuf(stderr, NULL, _IOFBF, 4096);

	if (listen_port == 0)
		listen_port = DEFAULT_GIT_PORT;

	/*
	 * If no --listen=<addr> args are given, the setup_named_sock()
	 * code will use receive a NULL address and set INADDR_ANY.
	 * This exposes both internal and external interfaces on the
	 * port.
	 *
	 * Disallow that and default to the internal-use-only loopback
	 * address.
	 */
	if (!listen_addr.nr)
		string_list_append(&listen_addr, "127.0.0.1");

	/*
	 * worker_mode is set in our own child process instances
	 * (that are bound to a connected socket from a client).
	 */
	if (worker_mode)
		return worker();

	/*
	 * `cld_argv` is a bit of a clever hack. The top-level instance
	 * of test-http-server does the normal bind/listen/accept stuff.
	 * For each incoming socket, the top-level process spawns
	 * a child instance of test-http-server *WITH* the additional
	 * `--worker` argument. This causes the child to set `worker_mode`
	 * and immediately call `worker()` using the connected socket (and
	 * without the usual need for fork() or threads).
	 *
	 * The magic here is made possible because `cld_argv` is static
	 * and handle() (called by service_loop()) knows about it.
	 */
	strvec_push(&cld_argv, argv[0]);
	strvec_push(&cld_argv, "--worker");
	for (i = 1; i < argc; ++i)
		strvec_push(&cld_argv, argv[i]);

	/*
	 * Setup primary instance to listen for connections.
	 */
	return serve(&listen_addr, listen_port);
}