/*
 Copyright 2015, 2016, 2017 IoT.bzh

 author: José Bollo <jose.bollo@iot.bzh>

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
*/

#define _GNU_SOURCE

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <assert.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <poll.h>
#include <signal.h>

extern char **environ;

#include "verbose.h"
#include "afm-launch-mode.h"
#include "afm-launch.h"
#include "secmgr-wrap.h"

#define DEFAULT_TYPE "text/html"

/*
 * structure for a launching type
 */
struct type_list {
	struct type_list *next; /* next type */
	char type[1];           /* type name */
};

/*
 * structure for launch vectors
 */
struct exec_vector {
	int has_readyfd;     /* has a request for readyness */
	const char **args;   /* vector of arguments */
};

struct desc_launcher {
	struct desc_launcher *next;   /* next launcher description */
	enum afm_launch_mode mode;    /* the launch mode */
	struct type_list *types;      /* the launched types */
	struct exec_vector execs[2];  /* the launching vectors */
};

struct launchparam {
	int port;
	int readyfd;
	char **uri;
	const char *secret;
	const char *datadir;
	struct exec_vector *execs;
};

/*
 * Structure for reading the configuration file
 */
struct confread {
	const char *filepath; /* path of the configuration file */
	FILE *file;           /* handle to the file */
	int lineno;           /* current line number */
	int index;            /* start of the current token (in buffer) */
	int length;           /* length of the current token */
	char buffer[4096];    /* current line */
};

/*
 * list of launch descriptions
 */
struct desc_launcher *launchers = NULL;

/*
 * the group when launched (to avoid the setgid effect)
 */
static gid_t groupid = 0;

/*
 * separators within configuration files
 */
static const char separators[] = " \t\n";

/*
 * default string emitted when for application not having signal
 */
static const char readystr[] = "READY=1";

/*
 * default time out for readiness of signaling applications
 */
static const int ready_timeout = 1500;

#if defined(DUMP_LAUNCHERS)
/*
 * dump all the known launchers to the 'file'
 */
static void dump_launchers(FILE *file)
{
	int j, k;
	struct desc_launcher *desc;
	struct type_list *type;

	for (desc = launchers ; desc != NULL ; desc = desc->next) {
		fprintf(file, "mode %s\n", name_of_launch_mode(desc->mode));
		for (type = desc->types ; type != NULL ; type = type->next)
			fprintf(file, "%s\n", type->type);
		for ( j = 0 ; j < 2 ; j++)
			if (desc->execs[j].args != NULL) {
				for (k = 0; desc->execs[j].args[k] != NULL; k++)
					fprintf(file, "  %s",
							desc->execs[j].args[k]);
				fprintf(file, "\n");
			}
		fprintf(file, "\n");
	}
}
#endif

/*
 * update 'cread' to point the the next token
 * returns the length of the token that is nul if no
 * more token exists in the line
 */
static int next_token(struct confread *cread)
{
	int idx = cread->index + cread->length;
	cread->index = idx + (int)strspn(&cread->buffer[idx], separators);
	cread->length = (int)strcspn(&cread->buffer[cread->index], separators);
	return cread->length;
}

/*
 * reads the next line, skipping empty lines or lines
 * having only comments.
 * returns either 0 at end of the file, -1 in case of error or
 * in case of success the length of the first token.
 */
static int read_line(struct confread *cread)
{
	while (fgets(cread->buffer, sizeof cread->buffer, cread->file) != NULL) {
		cread->lineno++;
		cread->index = (int)strspn(cread->buffer, separators);
		if (cread->buffer[cread->index]
		  && cread->buffer[cread->index] != '#') {
			cread->length = (int)strcspn(
				&cread->buffer[cread->index], separators);
			assert(cread->length > 0);
			return cread->length;
		}
	}
	if (ferror(cread->file)) {
		ERROR("%s:%d: error while reading, %m", cread->filepath,
								cread->lineno);
		return -1;
	}
	return 0;
}

/*
 * extract from 'cread' a launch vector that is allocated in
 * one piece of memory.
 * 'cread' is left unchanged (index and length are not changed)
 */
static const char **read_vector(struct confread *cread)
{
	int index0, length0;
	const char **vector;
	char *args;
	unsigned count, length;

	/* record origin */
	index0 = cread->index;
	length0 = cread->length;

	/* count */
	count = 0;
	length = 0;
	while(cread->length) {
		count++;
		length += (unsigned)cread->length;
		next_token(cread);
	}

	/* allocates */
	cread->index = index0;
	cread->length = length0;
	vector = malloc(length + count + (count + 1) * sizeof(char*));
	if (vector == NULL)
		return NULL;

	/* copies */
	args = (char*)(vector + count + 1);
	count = 0;
	while(cread->length) {
		vector[count++] = args;
		memcpy(args, &cread->buffer[cread->index],
						(unsigned)cread->length);
		args += cread->length;
		*args++ = 0;
		next_token(cread);
	}
	vector[count] = NULL;
	cread->index = index0;
	cread->length = length0;
	return vector;
}

/*
 * Reads the type from 'cread' directly in the list item and return it.
 * returns NULL in case or error.
 * errno:
 *  - EINVAL     extra characters
 *  - ENOMEM     memory depletion
 */
static struct type_list *read_type(struct confread *cread)
{
	int index, length;
	struct type_list *result;

	/* record index and length */
	index = cread->index;
	length = cread->length;

	/* check no extra characters */
	if (next_token(cread)) {
		ERROR("%s:%d: extra characters found after type %.*s",
			cread->filepath, cread->lineno, length,
						&cread->buffer[index]);
		errno = EINVAL;
		return NULL;
	}

	/* allocate structure */
	result = malloc(sizeof(struct type_list) + (unsigned)length);
	if (result == NULL) {
		ERROR("%s:%d: out of memory", cread->filepath, cread->lineno);
		errno = ENOMEM;
		return NULL;
	}

	/* fill the structure */
	memcpy(result->type, &cread->buffer[index], (unsigned)length);
	result->type[length] = 0;
	return result;
}

/*
 * Reads the mode from 'cread' and return it.
 * returns invalid_launch_mode in case or error.
 * errno:
 *  - EINVAL     no mode or extra characters or invalid mode
 */
static enum afm_launch_mode read_mode(struct confread *cread)
{
	int index, length;
	enum afm_launch_mode result;

	assert(cread->index == 0);
	assert(!strncmp(&cread->buffer[cread->index], "mode", 4));

	/* get the next token: the mode string */
	if (!next_token(cread)) {
		ERROR("%s:%d: no mode value set", cread->filepath,
							cread->lineno);
		errno = EINVAL;
		return invalid_launch_mode;
	}

	/* record index and length */
	index = cread->index;
	length = cread->length;

	/* check no extra characters */
	if (next_token(cread)) {
		ERROR("%s:%d: extra characters found after mode %.*s",
			cread->filepath, cread->lineno, length,
						&cread->buffer[index]);
		errno = EINVAL;
		return invalid_launch_mode;
	}

	/* get the mode */
	cread->buffer[index + length] = 0;
	result = launch_mode_of_name(&cread->buffer[index]);
	if (result == invalid_launch_mode) {
		ERROR("%s:%d: invalid mode value %s",
			cread->filepath, cread->lineno, &cread->buffer[index]);
		errno = EINVAL;
	}
	return result;
}

/*
 * free the memory used by 'types'
 */
static void free_type_list(struct type_list *types)
{
	while (types != NULL) {
		struct type_list *next = types->next;
		free(types);
		types = next;
	}
}

/*
 * reads the configuration file handled by 'cread'
 * and adds its contents to the launcher list
 *
 * returns 0 in case of success or -1 in case of error.
 */
static int read_launchers(struct confread *cread)
{
	int rc, has_readyfd;
	struct type_list *types, *lt;
	struct desc_launcher *desc;
	enum afm_launch_mode mode;
	const char **vector;

	/* reads the file */
	lt = NULL;
	types = NULL;
	desc = NULL;
	mode = invalid_launch_mode;
	rc = read_line(cread);
	while (rc > 0) {
		if (cread->index == 0) {
			if (cread->length == 4
			&& !memcmp(&cread->buffer[cread->index], "mode", 4)) {
				/* check if allowed */
				if (types != NULL) {
					ERROR("%s:%d: mode found before"
							" launch vector",
							cread->filepath,
							cread->lineno);
					errno = EINVAL;
					free_type_list(types);
					return -1;
				}

				/* read the mode */
				mode = read_mode(cread);
				if (mode == invalid_launch_mode)
					return -1;
			} else {
				if (mode == invalid_launch_mode) {
					ERROR("%s:%d: mode not found"
							" before type",
							cread->filepath,
							cread->lineno);
					errno = EINVAL;
					assert(types == NULL);
					return -1;
				}
				/* read a type */
				lt = read_type(cread);
				if (lt == NULL) {
					free_type_list(types);
					return -1;
				}
				lt->next = types;
				types = lt;
			}
			desc = NULL;
		} else if (types == NULL && desc == NULL) {
			if (lt == NULL)
				ERROR("%s:%d: untyped launch vector found",
					cread->filepath, cread->lineno);
			else
				ERROR("%s:%d: extra launch vector found"
					" (the maximum count is 2)",
					cread->filepath, cread->lineno);
			errno = EINVAL;
			return -1;
		} else {
			has_readyfd = NULL != strstr(
					&cread->buffer[cread->index], "%R");
			vector = read_vector(cread);
			if (vector == NULL) {
				ERROR("%s:%d: out of memory",
					cread->filepath, cread->lineno);
				free_type_list(types);
				errno = ENOMEM;
				return -1;
			}
			if (types) {
				assert(desc == NULL);
				desc = malloc(sizeof * desc);
				if (desc == NULL) {
					ERROR("%s:%d: out of memory",
						cread->filepath, cread->lineno);
					free_type_list(types);
					errno = ENOMEM;
					return -1;
				}
				desc->next = launchers;
				desc->mode = mode;
				desc->types = types;
				desc->execs[0].has_readyfd = has_readyfd;
				desc->execs[0].args = vector;
				desc->execs[1].has_readyfd = 0;
				desc->execs[1].args = NULL;
				types = NULL;
				launchers = desc;
			} else {
				desc->execs[1].has_readyfd = has_readyfd;
				desc->execs[1].args = vector;
				desc = NULL;
			}
		}
		rc = read_line(cread);
	}
	if (types != NULL) {
		ERROR("%s:%d: end of file found before launch vector",
			cread->filepath, cread->lineno);
		free_type_list(types);
		errno = EINVAL;
		return -1;
	}
	return rc;
}

/*
 * reads the configuration file 'filepath'
 * and adds its contents to the launcher list
 *
 * returns 0 in case of success or -1 in case of error.
 */
static int read_configuration_file(const char *filepath)
{
	int rc;
	struct confread cread;

	/* opens the configuration file */
	cread.file = fopen(filepath, "r");
	if (cread.file == NULL) {
		/* error */
		ERROR("can't read file %s: %m", filepath);
		rc = -1;
	} else {
		/* reads it */
		cread.filepath = filepath;
		cread.lineno = 0;
		rc = read_launchers(&cread);
		fclose(cread.file);
	}
	return rc;
}

/*
 * Creates a secret in 'buffer'
 */
static void mksecret(char buffer[9])
{
	snprintf(buffer, 9, "%08lX", (0xffffffff & random()));
}

/*
 * Allocates a port and return it.
 */
static int mkport()
{
	static int port_ring = 12345;
	int port = port_ring;
	if (port < 12345 || port > 15432)
		port = 12345;
	port_ring = port + 1;
	return port;
}

/*
%% %
%a appid			desc->appid
%b bindings			desc->bindings
%c content			desc->content
%D datadir			params->datadir
%H height			desc->height
%h homedir			desc->home
%I icondir			FWK_ICON_DIR
%m mime-type			desc->type
%n name				desc->name
%P port				params->port
%r rootdir			desc->path
%R readyfd                      params->readyfd
%S secret			params->secret
%W width			desc->width
*/

/*
 * Union for handling either scalar arguments or vectorial arguments.
 */
union arguments {
	char *scalar;  /* string of space separated arguments */
	char **vector; /* vector of arguments */
};

/*
 * Computes the substitutions of 'args' according to the
 * data of 'desc' and 'params'. The result is a single
 * piece of memory (that must be freed in one time)
 * containing either a vector or a string depending on
 * the value of 'wants_vector'.
 *
 * The vectors are made of an array pointers terminated by
 * the NULL pointer.
 *
 * Returns the resulting value or NULL in case of error
 */
static union arguments instantiate_arguments(
	const char * const     *args,
	struct afm_launch_desc *desc,
	struct launchparam     *params,
	int                     wants_vector
)
{
	const char * const *iter;
	const char *p, *v;
	char *data, c, sep;
	unsigned n, s;
	union arguments result;
	char port[20], width[20], height[20], readyfd[20], mini[3];

	/* init */
	sep = wants_vector ? 0 : ' ';
	mini[0] = '%';
	mini[2] = 0;

	/*
	 * loop that either compute the size and build the result
	 * advantage: appears only in one place
	 */
	result.vector = NULL; /* initialise both to avoid */
	result.scalar = NULL; /* a very stupid compiler warning */
	data = NULL;          /* no data for the first iteration */
	n = s = 0;
	for (;;) {
		/* iterate over arguments */
		for (n = 0, iter = args ; (p = *iter) != NULL ; iter++) {
			/* init the vector */
			if (data && !sep)
				result.vector[n] = data;
			n++;

			/* scan the argument */
			while((c = *p++) != 0) {
				if (c != '%') {
					/* standard character */
					if (data)
						*data++ = c;
					else
						s++;
				} else {
					/* substitutions */
					/* (convert num->string only once) */
					c = *p++;
					switch (c) {
					case 'a': v = desc->appid; break;
					case 'b':
						v = "" /*TODO:desc->bindings*/;
						break;
					case 'c': v = desc->content; break;
					case 'D': v = params->datadir; break;
					case 'H':
						if(!data)
							sprintf(height, "%d",
								desc->height);
						v = height;
						break;
					case 'h': v = desc->home; break;
					case 'I': v = FWK_ICON_DIR; break;
					case 'm': v = desc->type; break;
					case 'n': v = desc->name; break;
					case 'P':
						if(!data)
							sprintf(port, "%d",
								params->port);
						v = port;
						break;
					case 'R':
						if(!data)
							sprintf(readyfd, "%d",
							     params->readyfd);
						v = readyfd;
						break;
					case 'r': v = desc->path; break;
					case 'S': v = params->secret; break;
					case 'W':
						if(!data)
							sprintf(width, "%d",
								desc->width);
						v = width;
						break;
					case '%':
						c = 0;
					default:
						mini[1] = c;
						v = mini;
						break;
					}
					if (data)
						data = stpcpy(data, v);
					else
						s += (unsigned)strlen(v);
				}
			}
			/* terminate the argument */
			if (data)
				*data++ = sep;
			else
				s++;
		}
		if (!data) {
			/* first iteration: allocation */
			if (sep) {
				result.scalar = malloc(s);
				data = result.scalar;
			} else {
				result.vector = malloc((n+1)*sizeof(char*) + s);
				if (result.vector != NULL)
					data = (char*)(&result.vector[n + 1]);
			}
			if (!data) {
				errno = ENOMEM;
				return result;
			}
		} else {
			/* second iteration: termination */
			if (sep)
				*--data = 0;
			else
				result.vector[n] = NULL;
			return result;
		}
	}
}

/*
 * Launchs (fork-execs) the program described by 'exec'
 * using the parameters of 'desc' and 'params' to instantiate
 * it. The created process is attached to the process group 'progrp'.
 *
 * After being created and before to be launched, the process
 * is put in its security environment and its directory is
 * changed to params->datadir.
 *
 * Returns the pid of the created process or -1 in case of error.
 */
static pid_t launch(
	struct afm_launch_desc *desc,
	struct launchparam     *params,
	struct exec_vector     *exec,
	pid_t                   progrp
)
{
	int rc;
	char **args, **env;
	pid_t pid;
	int rpipe[2];
	struct pollfd pfd;

	/* prepare the pipes */
	rc = pipe(rpipe);
	if (rc < 0) {
		ERROR("error while calling pipe2: %m");
		return -1;
	}

	/* instanciate the arguments */
	params->readyfd = rpipe[1];
	args = instantiate_arguments(exec->args, desc, params, 1).vector;
	env = instantiate_arguments((const char * const*)environ,
						desc, params, 1).vector;
	if (args == NULL || env == NULL) {
		close(rpipe[0]);
		close(rpipe[1]);
		free(args);
		free(env);
		ERROR("out of memory in master");
		errno = ENOMEM;
		return -1;
	}

	/* fork the master child */
	pid = fork();
	if (pid < 0) {

		/********* can't fork ************/

		close(rpipe[0]);
		close(rpipe[1]);
		free(args);
		free(env);
		ERROR("master fork failed: %m");
		return -1;
	}
	if (pid) {

		/********* in the parent process ************/

		close(rpipe[1]);
		free(args);
		free(env);
		pfd.fd = rpipe[0];
		pfd.events = POLLIN;

		/* wait for readyness */
		poll(&pfd, 1, ready_timeout);
		close(rpipe[0]);
		return pid;
	}

	/********* in the child process ************/

	close(rpipe[0]);

	/* set name by appid */
	verbose_set_name(desc->appid, 0);

	/* avoid set-gid effect */
	setresgid(groupid, groupid, groupid);

	/* enter the process group */
	rc = setpgid(0, progrp);
	if (rc) {
		ERROR("setpgid failed");
		_exit(1);
	}

	/* enter security mode */
	rc = secmgr_prepare_exec(desc->appid);
	if (rc < 0) {
		ERROR("call to secmgr_prepare_exec failed: %m");
		_exit(1);
	}

	/* enter the datadirectory */
	rc = mkdir(params->datadir, 0755);
	if (rc && errno != EEXIST) {
		ERROR("creation of datadir %s failed: %m", params->datadir);
		_exit(1);
	}
	rc = chdir(params->datadir);
	if (rc) {
		ERROR("can't enter the datadir %s: %m", params->datadir);
		_exit(1);
	}

	/* signal if needed */
	if (!exec->has_readyfd) {
		write(rpipe[1], readystr, sizeof(readystr) - 1);
		close(rpipe[1]);
	}

	/* executes the process */
	rc = execve(args[0], args, env);
	access(args[0], X_OK);
	ERROR("failed to exec master %s: %m", args[0]);
	_exit(1);
	return -1;
}

/*
 * Launches the application 'desc' in local mode using
 * 'params' and store the resulting pids in 'children'.
 *
 * Returns 0 in case of success or -1 in case of error.
 */
static int launch_local(
	struct afm_launch_desc *desc,
	pid_t                   children[2],
	struct launchparam     *params
)
{
	/* launches the first, making it group leader */
	children[0] = launch(desc, params, &params->execs[0], 0);
	if (children[0] <= 0)
		return -1;

	/* nothing more to launch ? */
	if (params->execs[1].args == NULL)
		return 0;

	/* launches the second in the group of the first */
	children[1] = launch(desc, params, &params->execs[1], children[0]);
	if (children[1] > 0)
		return 0;

	/* kill all on error */
	killpg(children[0], SIGKILL);
	return -1;
}

/*
 * Launches the application 'desc' in remote mode using
 * 'params' and store the resulting pids in 'children'.
 *
 * Returns 0 in case of success or -1 in case of error.
 */
static int launch_remote(
	struct afm_launch_desc *desc,
	pid_t                   children[2],
	struct launchparam     *params
)
{
	char *uri;

	/* instanciate the uri */
	if (params->execs[1].args == NULL)
		uri = NULL;
	else
		uri = instantiate_arguments(params->execs[1].args, desc,
							params, 0).scalar;
	if (uri == NULL) {
		ERROR("out of memory for remote uri");
		errno = ENOMEM;
		return -1;
	}

	/* launch the command */
	children[0] = launch(desc, params, &params->execs[0], 0);
	if (children[0] <= 0) {
		free(uri);
		return -1;
	}

	/* returns the uri in params */
	*params->uri = uri;
	return 0;
}

/*
 * Searchs the launcher descritpion for the given 'type' and 'mode'
 *
 * Returns the description found or NULL if nothing matches.
 */
static struct desc_launcher *search_launcher(const char *type,
						enum afm_launch_mode mode)
{
	struct desc_launcher *dl;
	struct type_list *tl;

	for (dl = launchers ; dl ; dl = dl->next)
		if (dl->mode == mode)
			for (tl = dl->types ; tl != NULL ; tl = tl->next)
				if (!strcasecmp(tl->type, type))
					return dl;
	return NULL;
}

/*
 * Launches the application described by 'desc'
 * and, in case of success, returns the resulting data
 * in 'children' and 'uri'.
 *
 * Returns 0 in case of success or -1 in case of error.
 */
int afm_launch(struct afm_launch_desc *desc, pid_t children[2], char **uri)
{
	int rc;
	char datadir[PATH_MAX];
	char secret[9];
	struct launchparam params;
	const char *type;
	struct desc_launcher *dl;

	/* should be init */
	assert(groupid != 0);
	assert(is_valid_launch_mode(desc->mode));
	assert(desc->mode == mode_local || uri != NULL);
	assert(uri == NULL || *uri == NULL);

	/* init */
	children[0] = 0;
	children[1] = 0;

	/* what launcher ? */
	type = desc->type != NULL && *desc->type ? desc->type : DEFAULT_TYPE;
	dl = search_launcher(type, desc->mode);
	if (dl == NULL) {
		ERROR("launcher not found for type %s and mode %s!",
				type, name_of_launch_mode(desc->mode));
		errno = ENOENT;
		return -1;
	}

	/* prepare paths */
	rc = snprintf(datadir, sizeof datadir, "%s/%s",
						desc->home, desc->appid);
	if (rc < 0 || rc >= (int)sizeof datadir) {
		ERROR("overflow for datadir");
		errno = EINVAL;
		return -1;
	}

	/* make the secret and port */
	mksecret(secret);
	params.uri = uri;
	params.port = mkport();
	params.secret = secret;
	params.datadir = datadir;
	params.execs = dl->execs;

	switch (desc->mode) {
	case mode_local:
		return launch_local(desc, children, &params);
	case mode_remote:
		return launch_remote(desc, children, &params);
	default:
		assert(0);
		return -1;
	}
}

/*
 * Initialise the module
 *
 * Returns 0 on success or else -1 in case of failure
 */
int afm_launch_initialize()
{
	int rc;
	gid_t r, e, s;

	/* compute the groupid to set at launch */
	getresgid(&r, &e, &s);
	if (s && s != e)
		groupid = s; /* the original groupid is used */
	else
		groupid = (gid_t)-1;

	/* reads the configuration file */
	rc = read_configuration_file(FWK_LAUNCH_CONF);
#if defined(DUMP_LAUNCHERS)
	if (!rc)
		dump_launchers(stderr);
#endif
	
	return rc;
}