/* SPDX-License-Identifier: GPL-2.0 */

/** \file audiod_command.c Commands for para_audiod. */

#include "para.h"

#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <sys/un.h>
#include <netdb.h>
#include <lopsub.h>

#include "audiod.lsg.h"
#include "lsu.h"
#include "audiod_cmd.lsg.h"
#include "list.h"
#include "sched.h"
#include "buffer_tree.h"
#include "filter.h"
#include "grab_client.h"
#include "error.h"
#include "sideband.h"
#include "audiod.h"
#include "net.h"
#include "daemon.h"
#include "string.h"
#include "write.h"
#include "fd.h"

/** \cond doxygen_exclude */
#define OPT_GIVEN(_opt, _cmd, _lpr) (lls_opt_given(lls_opt_result( \
	LSG_AUDIOD_CMD_ ## _cmd ## _OPT_ ## _opt, _lpr)))

extern struct sched *sched;
extern char *stat_item_values[NUM_STAT_ITEMS];

/* The maximal number of simultaneous connections. */
#define MAX_STAT_CLIENTS 50

/* Pointer to a command handler function. */
typedef int (*audiod_cmd_handler_t)(int, struct lls_parse_result *);

/* The lopsub user_data pointer. Only the command handler at the moment. */
struct audiod_command_info {
	audiod_cmd_handler_t handler; /**< Implementation of the command. */
};


/* Define the user_data pointer as expected by lopsub. */
#define EXPORT_AUDIOD_CMD_HANDLER(_cmd) \
	/** Implementation of _cmd. */ \
	const struct audiod_command_info lsg_audiod_cmd_com_ ## _cmd ## _user_data = { \
		.handler = com_ ## _cmd \
	};

/* Flags used for the stat command of para_audiod. */
enum stat_client_flags {
	/** Enable parser-friendly output. */
	SCF_PARSER_FRIENDLY = 1,
};

static INITIALIZED_LIST_HEAD(client_list);
static int num_clients;

/* The list of all status items used by para_{server,audiod,gui}. */
const char *status_item_list[] = {STATUS_ITEMS};

/*
 * Describes one status client of para_audiod.
 *
 * There is one instance of this structure per audiod client that has sent
 * the 'stat' command. These instances are organized as a linked list.
 */
struct stat_client {
	/* The stat client's file descriptor. */
	int fd;
	/* Bitmask of those status items the client is interested in. */
	uint64_t item_mask;
	/* See stat_client flags. */
	unsigned flags;
	/* Its entry in the list of stat clients. */
	struct list_head node;
};

/** \endcond */

/*
 * Add a status client to the client list and increment num_clients.
 * The mask parameter specifies which status items are sent to the client.
 */
static int stat_client_add(int fd, uint64_t mask, unsigned flags)
{
	struct stat_client *new_client;
	int ret;

	if (num_clients >= MAX_STAT_CLIENTS) {
		PARA_ERROR_LOG("maximal number of stat clients (%d) exceeded\n",
			MAX_STAT_CLIENTS);
		return -E_TOO_MANY_CLIENTS;
	}
	ret = dup(fd);
	if (ret < 0)
		return -ERRNO_TO_PARA_ERROR(errno);
	new_client = zalloc(sizeof(*new_client));
	new_client->fd = ret;
	PARA_INFO_LOG("adding client on fd %d\n", new_client->fd);
	new_client->item_mask = mask;
	new_client->flags = flags;
	para_list_add(&new_client->node, &client_list);
	num_clients++;
	return 1;
}

static void close_stat_client(struct stat_client *sc)
{
	PARA_INFO_LOG("closing client fd %d\n", sc->fd);
	close(sc->fd);
	list_del(&sc->node);
	free(sc);
	num_clients--;
}

/**
 * Empty the status clients list.
 *
 * This iterates over the list of connected status clients, closes each client
 * file descriptor and frees the resources.
 */
void close_stat_clients(void)
{
	struct stat_client *sc, *tmp;

	list_for_each_entry_safe(sc, tmp, &client_list, node)
		close_stat_client(sc);
	assert(num_clients == 0);
}

/**
 * Send a sideband packet to a client.
 *
 * Create a header and send header and buffer to the client using \ref
 * xwritev().
 *
 * \param fd Identifies the client.
 * \param buf May be NULL.
 * \param len Number of bytes to send, not including header.
 * \param band Stored as part of the header.
 *
 * \return Standard.
 */
int client_write_bin(int fd, char *buf, size_t len, enum sb_designator band)
{
	struct sb_context *ctx;
	struct sb_buffer sbb;
	struct iovec iov[2];
	int ret;

	sbb.iov.iov_base = buf;
	sbb.iov.iov_len = len;
	sbb.band = band;
	ctx = sb_new_send(&sbb, true, NULL, NULL);
	do {
		ret = sb_get_send_buffers(ctx, iov);
		ret = xwritev(fd, iov, ret);
		if (ret < 0) {
			sb_free(ctx);
			return ret;
		}
	} while (sb_sent(ctx, ret) == false);
	return 1;
}

static int client_write(int fd, char *buf, enum sb_designator band)
{
	return client_write_bin(fd, buf, buf? strlen(buf) : 0, band);
}

/**
 * Write the contents of a status item to all connected status clients.
 *
 * \param item_num The number of the status item.
 *
 * Removes the status client from the client list on write errors.
 */
void stat_client_write_item(int item_num)
{
	struct stat_client *sc, *tmp;
	struct para_buffer pb = {.flags = 0};
	struct para_buffer pfpb = {.flags = PBF_SIZE_PREFIX};
	const uint64_t one = 1;
	char *msg = stat_item_values[item_num];
	struct para_buffer *b;

	list_for_each_entry_safe(sc, tmp, &client_list, node) {
		int ret;

		if (!((one << item_num) & sc->item_mask))
			continue;
		b = (sc->flags & SCF_PARSER_FRIENDLY)? &pfpb : &pb;
		if (!b->buf)
			WRITE_STATUS_ITEM(b, item_num, "%s\n", msg? msg : "");
		ret = client_write(sc->fd, b->buf, SBD_OUTPUT);
		if (ret < 0) {
			PARA_INFO_LOG("%s: closing stat client on fd %d\n",
				para_strerror(-ret), sc->fd);
			close_stat_client(sc);
		}
	}
	free(pb.buf);
	free(pfpb.buf);
}

/* Check if the given string is a known status item and return its index. */
static int stat_item_valid(const char *item)
{
	int i;
	if (!item || !*item) {
		PARA_ERROR_LOG("%s\n", "no item");
		return -E_UNKNOWN_STAT_ITEM;
	}
	FOR_EACH_STATUS_ITEM(i)
		if (!strcmp(status_item_list[i], item))
			return i;
	PARA_ERROR_LOG("invalid stat item: %s\n", item);
	return -E_UNKNOWN_STAT_ITEM;
}

__malloc static char *audiod_status_string(void)
{
	const char *status = (audiod_status == AUDIOD_ON)?
		"on" : (audiod_status == AUDIOD_OFF)? "off": "sb";
	return para_strdup(status);
}

static int com_help(int fd, struct lls_parse_result *lpr)
{
	char *buf;
	int ret, ret2;
	bool long_help = OPT_GIVEN(LONG, HELP, lpr);

	ret = lsu_com_help(long_help, lpr, audiod_cmd_suite, NULL, &buf, NULL);
	ret2 = client_write(fd, buf, ret < 0? SBD_ERROR_LOG : SBD_OUTPUT);
	free(buf);
	return ret < 0? ret : ret2;
}
EXPORT_AUDIOD_CMD_HANDLER(help)

static int com_ll(int fd, struct lls_parse_result *lpr)
{
	unsigned ll;
	char *errctx;
	const char *sev[] = {SEVERITIES};
	const char *arg;
	int ret = lls(lls_check_arg_count(lpr, 0, 1, &errctx));

	if (ret < 0) {
		char *tmp = make_message("%s\n", errctx);
		free(errctx);
		client_write(fd, tmp, SBD_ERROR_LOG);
		free(tmp);
		return ret;
	}
	if (lls_num_inputs(lpr) == 0) {
		char *msg;
		ll = daemon_get_loglevel();
		msg = make_message("%s\n", sev[ll]);
		ret = client_write(fd, msg, SBD_OUTPUT);
		free(msg);
		return ret;
	}
	arg = lls_input(0, lpr);
	for (ll = 0; ll < NUM_LOGLEVELS; ll++) {
		if (!strcmp(arg, sev[ll]))
			break;
	}
	if (ll >= NUM_LOGLEVELS)
		return -ERRNO_TO_PARA_ERROR(EINVAL);
	PARA_INFO_LOG("new log level: %s\n", sev[ll]);
	daemon_set_loglevel(ll);
	return 1;
}
EXPORT_AUDIOD_CMD_HANDLER(ll)

static int com_tasks(int fd, __a_unused struct lls_parse_result *lpr)
{
	int ret;
	char *tl = get_task_list(sched);

	if (!tl) /* no tasks registered yet */
		return 0;
	ret = client_write(fd, tl, SBD_OUTPUT);
	free(tl);
	return ret;
}
EXPORT_AUDIOD_CMD_HANDLER(tasks)

static int com_stat(int fd, struct lls_parse_result *lpr)
{
	int i, ret;
	bool parser_friendly = OPT_GIVEN(PARSER_FRIENDLY, STAT, lpr);
	bool one_shot = OPT_GIVEN(ONE_SHOT, STAT, lpr);
	uint64_t mask = 0;
	const uint64_t one = 1;
	struct para_buffer b = {.flags = 0};
	unsigned num_inputs, client_flags = 0;

	ret = mark_fd_nonblocking(fd);
	if (ret < 0)
		return ret;
	if (parser_friendly) {
		b.flags = PBF_SIZE_PREFIX;
		client_flags |= SCF_PARSER_FRIENDLY;
	}
	num_inputs = lls_num_inputs(lpr);
	if (num_inputs == 0)
		mask--; /* set all bits */
	for (i = 0; i < num_inputs; i++) {
		ret = stat_item_valid(lls_input(i, lpr));
		if (ret < 0)
			return ret;
		mask |= (one << ret);
	}
	PARA_INFO_LOG("mask: 0x%llx\n", (long long unsigned)mask);
	FOR_EACH_STATUS_ITEM(i) {
		char *item = stat_item_values[i];
		if (!((one << i) & mask))
			continue;
		WRITE_STATUS_ITEM(&b, i, "%s\n", item? item : "");
	}
	ret = client_write(fd, b.buf, SBD_OUTPUT);
	free(b.buf);
	if (ret < 0)
		return ret;
	if (one_shot)
		return 0;
	ret = stat_client_add(fd, mask, client_flags);
	return ret < 0? ret : -E_SUBCMD_RUNNING;
}
EXPORT_AUDIOD_CMD_HANDLER(stat)

static int com_grab(int fd, struct lls_parse_result *lpr)
{
	char buf[] = "The grab subcommand is deprecated.\n";
	int ret;

	PARA_WARNING_LOG("running deprecated grab subcommand on fd %d\n", fd);
	ret = client_write(fd, buf, SBD_WARNING_LOG);
	if (ret < 0)
		return ret;
	ret = grab_client_new(fd, lpr, sched);
	return ret < 0? ret : -E_SUBCMD_RUNNING;
}
EXPORT_AUDIOD_CMD_HANDLER(grab)

static int com_term(__a_unused int fd, __a_unused struct lls_parse_result *lpr)
{
	return -E_AUDIOD_TERM;
}
EXPORT_AUDIOD_CMD_HANDLER(term)

static int com_on(__a_unused int fd, __a_unused struct lls_parse_result *lpr)
{
	audiod_status = AUDIOD_ON;
	return 1;
}
EXPORT_AUDIOD_CMD_HANDLER(on)

static int com_off(__a_unused int fd, __a_unused struct lls_parse_result *lpr)
{
	audiod_status = AUDIOD_OFF;
	return 1;
}
EXPORT_AUDIOD_CMD_HANDLER(off)

static int com_sb(__a_unused int fd, __a_unused struct lls_parse_result *lpr)
{
	audiod_status = AUDIOD_STANDBY;
	return 1;
}
EXPORT_AUDIOD_CMD_HANDLER(sb)

static int com_cycle(__a_unused int fd, __a_unused struct lls_parse_result *lpr)
{
	switch (audiod_status) {
		case  AUDIOD_ON: audiod_status = AUDIOD_STANDBY; break;
		case  AUDIOD_OFF: audiod_status = AUDIOD_ON; break;
		case  AUDIOD_STANDBY: audiod_status = AUDIOD_OFF; break;
	}
	return 1;
}
EXPORT_AUDIOD_CMD_HANDLER(cycle)

static int com_version(int fd, struct lls_parse_result *lpr)
{
	int ret;
	char *msg;
	bool verbose = OPT_GIVEN(VERBOSE, VERSION, lpr);

	if (verbose)
		msg = make_message("%s", version_text("audiod"));
	else
		msg = make_message("%s\n", version_single_line("audiod"));
	ret = client_write(fd, msg, SBD_OUTPUT);
	free(msg);
	return ret < 0? ret : 0;
}
EXPORT_AUDIOD_CMD_HANDLER(version)

#ifndef HAVE_UCRED
static int recv_cred_buffer(int fd, struct iovec *iov, uid_t *uid)
{
	*uid = 1;
	return recv_buffer(fd, iov->iov_base, iov->iov_len);
}
#else /* HAVE_UCRED */
static void dispose_fds(int *fds, unsigned num)
{
	int i;

	for (i = 0; i < num; i++)
		close(fds[i]);
}

/*
 * Receive a buffer and the Unix credentials of the sending process.
 * Returns negative on errors, the number of bytes received on success. The
 * user id of the sending process is returned via the uid pointer argument.
 */
static int recv_cred_buffer(int fd, struct iovec *iov, uid_t *uid)
{
	char control[255] __a_aligned(8);
	struct msghdr msg;
	struct cmsghdr *cmsg;
	int ret, yes = 1;
	struct ucred cred;
	bool have_uid = false;

	*uid = -1;
	setsockopt(fd, SOL_SOCKET, SO_PASSCRED, &yes, sizeof(int));
	memset(&msg, 0, sizeof(msg));
	memset(iov->iov_base, 0, iov->iov_len);
	msg.msg_iov = iov;
	msg.msg_iovlen = 1;
	msg.msg_control = control;
	msg.msg_controllen = sizeof(control);
	ret = recvmsg(fd, &msg, 0);
	if (ret < 0)
		return -ERRNO_TO_PARA_ERROR(errno);
	cmsg = CMSG_FIRSTHDR(&msg);
	while (cmsg) {
		if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type
				== SCM_CREDENTIALS) {
			memcpy(&cred, CMSG_DATA(cmsg), sizeof(struct ucred));
			*uid = cred.uid;
			have_uid = true;
		} else
			if (cmsg->cmsg_level == SOL_SOCKET
					&& cmsg->cmsg_type == SCM_RIGHTS) {
				dispose_fds((int *)CMSG_DATA(cmsg),
					(cmsg->cmsg_len - CMSG_LEN(0))
					/ sizeof(int));
			}
		cmsg = CMSG_NXTHDR(&msg, cmsg);
	}
	return have_uid? ret: -E_SCM_CREDENTIALS;
}
#endif /* HAVE_UCRED */

/**
 * Handle arriving connections on the local socket.
 *
 * \param accept_fd The fd to accept connections on.
 *
 * This is called in each iteration of the main loop of the scheduler. If there
 * is an incoming connection, the function reads the command sent by the peer,
 * checks the connecting user's permissions by using unix socket credentials
 * (if supported by the OS) and calls the corresponding command handler if
 * permissions are OK.
 *
 * \return Positive on success, negative on errors, zero if there was no
 * connection to accept.
 *
 * \sa \ref para_accept().
 */
int dispatch_local_connection(int accept_fd)
{
	int argc, ret, clifd;
	char buf[MAXLINE], **argv = NULL;
	struct iovec iov = {.iov_base = buf, .iov_len = sizeof(buf) - 1};
	struct sockaddr_un unix_addr;
	uid_t uid;
	const struct lls_command *cmd;
	struct lls_parse_result *lpr;
	char *errctx = NULL;
	const struct audiod_command_info *aci;
	size_t received;
	char *p, *end;

	ret = para_accept(accept_fd, &unix_addr, sizeof(struct sockaddr_un), &clifd);
	if (ret <= 0)
		return ret;
	ret = recv_cred_buffer(clifd, &iov, &uid);
	if (ret < 0)
		goto out;
	received = ret;
#ifdef HAVE_UCRED
	ret = -E_UCRED_PERM;
	if (!uid_is_whitelisted(uid))
		goto close_clifd;
#endif
	p = buf + 1;
	end = buf + received;
	argc = 0;
	while (p < end) {
		argc++;
		p = memchr(p, '\0', end - p);
		ret = -ERRNO_TO_PARA_ERROR(EINVAL);
		if (!p)
			goto close_clifd;
		p++;
	}
	argv = alloc((argc + 1) * sizeof(char *));
	p = buf + 1;
	for (unsigned n = 0; n < argc; n++) {
		argv[n] = para_strdup(p);
		p += strlen(p) + 1;
	}
	argv[argc] = NULL;
	ret = lls(lls_lookup_subcmd(argv[0], audiod_cmd_suite, &errctx));
	if (ret < 0)
		goto free_argv;
	cmd = lls_cmd(ret, audiod_cmd_suite);
	ret = lls(lls_parse(argc, argv, cmd, &lpr, &errctx));
	if (ret < 0)
		goto free_argv;
	aci = lls_user_data(cmd);
	ret = aci->handler(clifd, lpr);
	lls_free_parse_result(lpr, cmd);
free_argv:
	free_argv(argv);
close_clifd:
	if (ret == -E_CLIENT_WRITE)
		goto out;
	if (ret == -E_SUBCMD_RUNNING) {
		ret = 0;
		goto out;
	}
	if (ret < 0) {
		char *tmp;
		if (errctx) {
			tmp = make_message("errctx: %s\n", errctx);
			free(errctx);
			client_write(clifd, tmp, SBD_ERROR_LOG);
			free(tmp);
		}
		tmp = make_message("%s\n", para_strerror(-ret));
		client_write(clifd, tmp, SBD_ERROR_LOG);
		free(tmp);
		client_write(clifd, NULL, ret == -E_AUDIOD_TERM?
			SBD_EXIT__SUCCESS : SBD_EXIT__FAILURE);
		goto out;
	}
	client_write(clifd, NULL, SBD_EXIT__SUCCESS);
out:
	close(clifd);
	return ret;
}

/**
 * Send the current audiod status to all connected stat clients.
 *
 * \param force Whether to write unchanged items.
 */
void audiod_status_dump(bool force)
{
	char *old, *new;

	old = stat_item_values[SI_play_time];
	new = get_time_string();
	if (new) {
		if (force || !old || strcmp(old, new)) {
			free(old);
			stat_item_values[SI_play_time] = new;
			stat_client_write_item(SI_play_time);
		} else
			free(new);
	}

	new = daemon_get_uptime_str(now);
	old = stat_item_values[SI_audiod_uptime];
	if (force || !old || strcmp(old, new)) {
		free(old);
		stat_item_values[SI_audiod_uptime] = new;
		stat_client_write_item(SI_audiod_uptime);
	} else
		free(new);

	old = stat_item_values[SI_audiod_status];
	new = audiod_status_string();
	if (force || !old || strcmp(old, new)) {
		free(old);
		stat_item_values[SI_audiod_status] = new;
		stat_client_write_item(SI_audiod_status);
	} else
		free(new);

	old = stat_item_values[SI_decoder_flags];
	new = audiod_get_decoder_flags();
	if (force || !old || strcmp(old, new)) {
		free(old);
		stat_item_values[SI_decoder_flags] = new;
		stat_client_write_item(SI_decoder_flags);
	} else
		free(new);
}