/*
 * libifupdown/lifecycle.c
 * Purpose: management of interface lifecycle (bring up, takedown, reload)
 *
 * Copyright (c) 2020 Ariadne Conill <ariadne@dereferenced.org>
 * Copyright (c) 2020 Maximilian Wilhelm <max@sdn.clinic>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * This software is provided 'as is' and without any warranty, express or
 * implied.  In no event shall the authors be liable for any damages arising
 * from the use of this software.
 */

#include <ctype.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>

#include "libifupdown/environment.h"
#include "libifupdown/execute.h"
#include "libifupdown/interface.h"
#include "libifupdown/lifecycle.h"
#include "libifupdown/state.h"
#include "libifupdown/tokenize.h"
#include "libifupdown/config-file.h"

#define BUFFER_LEN 4096

static bool
handle_commands_for_phase(const struct lif_execute_opts *opts, char *const envp[], const struct lif_interface *iface, const char *phase)
{
	const struct lif_node *iter;

	LIF_DICT_FOREACH(iter, &iface->vars)
	{
		const struct lif_dict_entry *entry = iter->data;

		if (strcmp(entry->key, phase))
			continue;

		const char *cmd = entry->data;
		if (!lif_execute_fmt(opts, envp, "%s", cmd))
			return false;
	}

	return true;
}

static inline bool
handle_single_executor_for_phase(const struct lif_dict_entry *entry, const struct lif_execute_opts *opts, char *const envp[], const char *phase, const char *lifname)
{
	if (strcmp(entry->key, "use"))
		return true;

	const char *cmd = entry->data;
	if (!lif_maybe_run_executor(opts, envp, cmd, phase, lifname))
		return false;

	return true;
}

static bool
handle_executors_for_phase(const struct lif_execute_opts *opts, char *const envp[], const struct lif_interface *iface, bool up, const char *phase)
{
	const struct lif_node *iter;

	if (up)
	{
		LIF_DICT_FOREACH(iter, &iface->vars)
			handle_single_executor_for_phase(iter->data, opts, envp, phase, iface->ifname);
	}
	else
	{
		LIF_DICT_FOREACH_REVERSE(iter, &iface->vars)
			handle_single_executor_for_phase(iter->data, opts, envp, phase, iface->ifname);
	}

	return true;
}

static bool
query_dependents_from_executors(const struct lif_execute_opts *opts, char *const envp[], const struct lif_interface *iface, char *buf, size_t bufsize, const char *phase)
{
	const struct lif_node *iter;

	LIF_DICT_FOREACH(iter, &iface->vars)
	{
		char resbuf[1024] = {};
		const struct lif_dict_entry *entry = iter->data;
		struct lif_execute_opts exec_opts = {
			.verbose = opts->verbose,
			.executor_path = opts->executor_path,
			.interfaces_file = opts->interfaces_file
		};

		if (strcmp(entry->key, "use"))
			continue;

		const char *cmd = entry->data;
		if (!lif_maybe_run_executor_with_result(&exec_opts, envp, cmd, resbuf, sizeof resbuf, phase, iface->ifname))
			return false;

		if (!*resbuf)
			continue;

		strlcat(buf, " ", bufsize);
		strlcat(buf, resbuf, bufsize);
	}

	return true;
}

bool
append_to_buffer(char **buffer, size_t *buffer_len, char **end, const char *value)
{
	size_t value_len = strlen (value);

	/* Make sure there is enough room to add the value to the buffer */
	if (*buffer_len < strlen (*buffer) + value_len + 2)
	{
		*buffer = realloc (*buffer, *buffer_len * 2);
		if (*buffer == NULL)
			/* XXX Here be dragons */
			return false;

		*buffer_len = *buffer_len * 2;
	}

	/* Append value to buffer */
	size_t printed = snprintf (*end, value_len + 2, "%s ", value);
	if (printed < value_len + 1)
		/* Here be dragons */
		return false;

	/* Move end pointer to last printed byte */
	*end += printed;

	return true;
}

static void
build_environment(char **envp[], const struct lif_execute_opts *opts, const struct lif_interface *iface, const char *lifname, const char *phase, const char *mode)
{
	if (lifname == NULL)
		lifname = iface->ifname;

	lif_environment_push(envp, "IFACE", lifname);
	lif_environment_push(envp, "PHASE", phase);
	lif_environment_push(envp, "MODE", mode);
	lif_environment_push(envp, "METHOD", "none");

	if (opts->verbose)
		lif_environment_push(envp, "VERBOSE", "1");

	if (opts->interfaces_file)
		lif_environment_push(envp, "INTERFACES_FILE", opts->interfaces_file);

	const struct lif_node *iter;
	bool did_address = false, did_gateway = false;

	/* Allocate a buffer for all possible addresses, if any */
	char *addresses = calloc (BUFFER_LEN, 1);
	size_t addresses_size = BUFFER_LEN;
	char *addresses_end = addresses;

	/* Allocate a buffer for all possible gateways, if any */
	char *gateways = calloc (BUFFER_LEN, 1);
	size_t gateways_size = BUFFER_LEN;
	char *gateways_end = gateways;

	LIF_DICT_FOREACH(iter, &iface->vars)
	{
		struct lif_dict_entry *entry = iter->data;

		if (!strcmp(entry->key, "address"))
		{
			char addrbuf[4096];

			if (!lif_address_format_cidr(iface, entry, addrbuf, sizeof(addrbuf)))
				continue;

			/* Append address to buffer */
			append_to_buffer(&addresses, &addresses_size, &addresses_end, addrbuf);

			/* Only print IF_ADDRESS once */
			if (did_address)
				continue;

			lif_environment_push(envp, "IF_ADDRESS", addrbuf);
			did_address = true;

			continue;
		}
		else if (!strcmp(entry->key, "gateway"))
		{
			/* Append address to buffer */
			append_to_buffer(&gateways, &gateways_size, &gateways_end, entry->data);

			if (did_gateway)
				continue;

			did_gateway = true;
		}
		else if (!strcmp(entry->key, "requires"))
		{
			if (iface->is_bridge)
				lif_environment_push(envp, "IF_BRIDGE_PORTS", (const char *) entry->data);
		}

		char envkey[4096] = "IF_";
		strlcat(envkey, entry->key, sizeof envkey);
		char *ep = envkey + 2;

		while (*ep++)
		{
			*ep = toupper(*ep);

			if (*ep == '-')
				*ep = '_';
		}

		lif_environment_push(envp, envkey, (const char *) entry->data);
	}

	if (addresses != NULL)
		lif_environment_push(envp, "IF_ADDRESSES", addresses);
	if (gateways != NULL)
		lif_environment_push(envp, "IF_GATEWAYS", gateways);

	/* Clean up */
	free (addresses);
	free (gateways);
}

bool
lif_lifecycle_query_dependents(const struct lif_execute_opts *opts, struct lif_interface *iface, const char *lifname)
{
	char deps[4096] = {};
	char final_deps[4096] = {};

	if (lifname == NULL)
		lifname = iface->ifname;

	char **envp = NULL;

	build_environment(&envp, opts, iface, lifname, "depend", "depend");

	struct lif_dict_entry *entry = lif_dict_find(&iface->vars, "requires");
	if (entry != NULL)
		strlcpy(deps, entry->data, sizeof deps);

	if (!query_dependents_from_executors(opts, envp, iface, deps, sizeof deps, "depend"))
		return false;

	char *p = deps;
	while (*p)
	{
		char *token = lif_next_token(&p);

		if (strstr(final_deps, token) != NULL)
			continue;

		strlcat(final_deps, token, sizeof final_deps);
		strlcat(final_deps, " ", sizeof final_deps);
	}

	if (entry != NULL)
	{
		free(entry->data);
		entry->data = strdup(final_deps);
	}
	else if (*final_deps)
		lif_dict_add(&iface->vars, "requires", strdup(final_deps));

	lif_environment_free(&envp);

	return true;
}

bool
lif_lifecycle_run_phase(const struct lif_execute_opts *opts, struct lif_interface *iface, const char *phase, const char *lifname, bool up)
{
	char **envp = NULL;

	build_environment(&envp, opts, iface, lifname, phase, up ? "start" : "stop");

	if (!handle_executors_for_phase(opts, envp, iface, up, phase))
		goto handle_error;

	if (!handle_commands_for_phase(opts, envp, iface, phase))
		goto handle_error;

	/* if we don't need to support /etc/if-X.d we're done here */
	if (!lif_config.allow_addon_scripts)
		goto out_free;

	/* Check if scripts dir for this phase is present and bail out if it isn't */
	struct stat dir_stat;
	char dir_path[4096];
	snprintf (dir_path, 4096, "/etc/network/if-%s.d", phase);

	if (stat (dir_path, &dir_stat) != 0 || S_ISDIR (dir_stat.st_mode) == 0) {
		goto out_free;
	}

	/* we should do error handling here, but ifupdown1 doesn't */
	lif_execute_fmt(opts, envp, "/bin/run-parts %s", dir_path);

out_free:
	lif_environment_free(&envp);
	return true;

handle_error:
	lif_environment_free(&envp);
	return false;
}

/* this function returns true if we can skip processing the interface for now,
 * otherwise false.
 */
static bool
handle_refcounting(struct lif_dict *state, struct lif_interface *iface, bool up)
{
	size_t orig_refcount = iface->refcount;

	if (up)
		lif_state_ref_if(state, iface->ifname, iface);
	else
		lif_state_unref_if(state, iface->ifname, iface);

#ifdef DEBUG_REFCOUNTING
	fprintf(stderr, "handle_refcounting(): orig_refcount=%zu, refcount=%zu, direction=%s\n",
		orig_refcount, iface->refcount, up ? "UP" : "DOWN");
#endif

	/* if going up and orig_refcount > 0 -- we're already configured. */
	if (up && orig_refcount > 0)
		return true;

	/* if going down and iface->refcount > 1 -- we still have other dependents. */
	if (!up && iface->refcount > 1)
		return true;

	/* we can change this interface -- no blocking dependents. */
	return false;
}

static bool
handle_dependents(const struct lif_execute_opts *opts, struct lif_interface *parent, struct lif_dict *collection, struct lif_dict *state, bool up)
{
	struct lif_dict_entry *requires = lif_dict_find(&parent->vars, "requires");

	/* no dependents, nothing to worry about */
	if (requires == NULL)
		return true;

	/* set the parent's pending flag to break dependency cycles */
	parent->is_pending = true;

	char require_ifs[4096] = {};
	strlcpy(require_ifs, requires->data, sizeof require_ifs);
	char *bufp = require_ifs;

	for (char *tokenp = lif_next_token(&bufp); *tokenp; tokenp = lif_next_token(&bufp))
	{
		struct lif_interface *iface = lif_interface_collection_find(collection, tokenp);

		if (iface->has_config_error)
		{
			if (opts->force)
				fprintf (stderr, "ifupdown: (de)configuring dependent interface %s (of %s) despite config errors\n",
				         iface->ifname, parent->ifname);
			else
			{
				fprintf (stderr, "ifupdown: skipping dependent interface %s (of %s) as it has config errors\n",
			        iface->ifname, parent->ifname);
				continue;
			}
		}

		/* if handle_refcounting returns true, it means we've already
		 * configured the interface, or it is too soon to deconfigure
		 * the interface.
		 */
		if (handle_refcounting(state, iface, up))
		{
			if (opts->verbose)
				fprintf(stderr, "ifupdown: skipping dependent interface %s (of %s) -- %s\n",
					iface->ifname, parent->ifname,
					up ? "already configured" : "transient dependencies still exist");

			continue;
		}

		if (!up && iface->is_explicit)
		{
			if (opts->verbose)
				fprintf(stderr, "ifupdown: skipping dependent interface %s (of %s) -- interface is marked as explicitly configured\n",
					iface->ifname, parent->ifname);

			continue;
		}

		if (opts->verbose)
			fprintf(stderr, "ifupdown: changing state of dependent interface %s (of %s) to %s\n",
				iface->ifname, parent->ifname, up ? "up" : "down");

		if (!lif_lifecycle_run(opts, iface, collection, state, iface->ifname, up))
		{
			parent->is_pending = false;
			return false;
		}
	}

	parent->is_pending = false;
	return true;
}

bool
lif_lifecycle_run(const struct lif_execute_opts *opts, struct lif_interface *iface, struct lif_dict *collection, struct lif_dict *state, const char *lifname, bool up)
{
	/* if we're already pending, exit */
	if (iface->is_pending)
		return true;

	if (iface->is_template)
		return false;

	if (lifname == NULL)
		lifname = iface->ifname;

	if (up)
	{
		/* when going up, dependents go up first. */
		if (!handle_dependents(opts, iface, collection, state, up))
			return false;

		/* XXX: we should try to recover (take the iface down) if bringing it up fails.
		 * but, right now neither debian ifupdown or busybox ifupdown do any recovery,
		 * so we wont right now.
		 */
		if (!lif_lifecycle_run_phase(opts, iface, "create", lifname, up))
			return false;

		if (!lif_lifecycle_run_phase(opts, iface, "pre-up", lifname, up))
			return false;

		if (!lif_lifecycle_run_phase(opts, iface, "up", lifname, up))
			return false;

		if (!lif_lifecycle_run_phase(opts, iface, "post-up", lifname, up))
			return false;

		lif_state_ref_if(state, lifname, iface);
	}
	else
	{
		if (!lif_lifecycle_run_phase(opts, iface, "pre-down", lifname, up))
			return false;

		if (!lif_lifecycle_run_phase(opts, iface, "down", lifname, up))
			return false;

		if (!lif_lifecycle_run_phase(opts, iface, "post-down", lifname, up))
			return false;

		if (!lif_lifecycle_run_phase(opts, iface, "destroy", lifname, up))
			return false;

		/* when going up, dependents go down last. */
		if (!handle_dependents(opts, iface, collection, state, up))
			return false;

		lif_state_unref_if(state, lifname, iface);
	}

	return true;
}

static bool
count_interface_rdepends(const struct lif_execute_opts *opts, struct lif_dict *collection, struct lif_interface *parent, size_t depth)
{
	/* if we have looped, return true immediately to break the loop. */
	if (parent->is_pending)
		return true;

	/* query our dependents if we don't have them already */
	if (!lif_lifecycle_query_dependents(opts, parent, parent->ifname))
		return false;

	/* set rdepends_count to depth, dependents will be depth + 1 */
	parent->is_pending = true;
	parent->rdepends_count = depth;

	struct lif_dict_entry *requires = lif_dict_find(&parent->vars, "requires");

	/* no dependents, nothing to worry about */
	if (requires == NULL)
	{
		parent->is_pending = false;
		return true;
	}

	/* walk any dependents */
	char require_ifs[4096] = {};
	strlcpy(require_ifs, requires->data, sizeof require_ifs);
	char *bufp = require_ifs;

	for (char *tokenp = lif_next_token(&bufp); *tokenp; tokenp = lif_next_token(&bufp))
	{
		struct lif_interface *iface = lif_interface_collection_find(collection, tokenp);

		if (!count_interface_rdepends(opts, collection, iface, depth + 1))
		{
			parent->is_pending = false;
			return false;
		}
	}

	parent->is_pending = false;
	return true;
}

ssize_t
lif_lifecycle_count_rdepends(const struct lif_execute_opts *opts, struct lif_dict *collection)
{
	struct lif_node *iter;

	LIF_DICT_FOREACH(iter, collection)
	{
		struct lif_dict_entry *entry = iter->data;
		struct lif_interface *iface = entry->data;

		/* start depth at interface's rdepends_count, which will be 0 for the root,
		 * but will be more if additional rdepends are found...
		 */
		if (!count_interface_rdepends(opts, collection, iface, iface->rdepends_count))
		{
			fprintf(stderr, "ifupdown: dependency graph is broken for interface %s\n", iface->ifname);
			return -1;
		}
	}

	/* figure out the max depth */
	size_t maxdepth = 0;

	LIF_DICT_FOREACH(iter, collection)
	{
		struct lif_dict_entry *entry = iter->data;
		struct lif_interface *iface = entry->data;

		if (iface->rdepends_count > maxdepth)
			maxdepth = iface->rdepends_count;
	}

	/* move the collection to a temporary list so we can reorder it */
	struct lif_list temp_list = {};
	struct lif_node *iter_next;

	LIF_LIST_FOREACH_SAFE(iter, iter_next, collection->list.head)
	{
		void *data = iter->data;

		lif_node_delete(iter, &collection->list);
		memset(iter, 0, sizeof *iter);

		lif_node_insert(iter, data, &temp_list);
	}

	/* walk backwards from maxdepth to 0, readding nodes */
	for (ssize_t curdepth = maxdepth; curdepth > -1; curdepth--)
	{
		LIF_LIST_FOREACH_SAFE(iter, iter_next, temp_list.head)
		{
			struct lif_dict_entry *entry = iter->data;
			struct lif_interface *iface = entry->data;

			if ((ssize_t) iface->rdepends_count != curdepth)
				continue;

			lif_node_delete(iter, &temp_list);
			memset(iter, 0, sizeof *iter);

			lif_node_insert(iter, entry, &collection->list);
		}
	}

	return maxdepth;
}
