/*
 * inode2prog.cpp
 *
 * Copyright (c) 2005,2006,2008,2009 Arnout Engelen
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 */


#include <sys/types.h>
#include <cerrno>
#include <cstring>
#include <dirent.h>
#include <ctype.h>
#include <cstdlib>
#include <iostream>
#include <cstdio>
#include <unistd.h>
#include <string>
#include <map>
#include <sys/stat.h>
#include <fcntl.h>
#include <climits>

#include "inode2prog.h"

extern bool bughuntmode;

// Not sure, but assuming there's no more PID's than go into 64 unsigned bits..
const int MAX_PID_LENGTH = 20;

// Max length of filenames in /proc/<pid>/fd/*. These are numeric, so 10 digits seems like a safe assumption.
const int MAX_FDLINK = 10;

/* maps from inode to program-struct */
std::map <unsigned long, prg_node *> inodeproc;

bool is_number (const char * string) {
	while (*string) {
		if (!isdigit (*string))
			return false;
		string++;
	}
	return true;
}

unsigned long str2ulong (const char * ptr) {
	unsigned long retval = 0;

	while ((*ptr >= '0') && (*ptr <= '9')) {
		retval *= 10;
		retval += *ptr - '0';
		ptr++;
	}
	return retval;
}

int str2int (const char * ptr) {
	int retval = 0;

	while ((*ptr >= '0') && (*ptr <= '9')) {
		retval *= 10;
		retval += *ptr - '0';
		ptr++;
	}
	return retval;
}

static std::string read_file (int fd) {
	char buf[255];
	std::string content;

	for (int length; (length = read(fd, buf, sizeof(buf))) > 0;) {
		if (length < 0) {
			std::fprintf(stderr, "Error reading file: %s\n", std::strerror(errno));
			std::exit(34);
		}
		content.append(buf, length);
	}

	return content;
}

static std::string read_file (const char* filepath) {
	int fd = open(filepath, O_RDONLY);

	if (fd < 0) {
		std::fprintf(stderr, "Error opening %s: %s\n", filepath, std::strerror(errno));
		std::exit(3);
		return NULL;
	}

	std::string contents = read_file(fd);

	if (close(fd)) {
		std::fprintf(stderr, "Error opening %s: %s\n", filepath, std::strerror(errno));
		std::exit(34);
	}

	return contents;
}

std::string getprogname (pid_t pid) {
	const int maxfilenamelen = 14 + MAX_PID_LENGTH + 1;
	char filename[maxfilenamelen];

	std::snprintf(filename, maxfilenamelen, "/proc/%d/cmdline", pid);
	return read_file(filename);
}

void setnode (unsigned long inode, pid_t pid) {
	prg_node * current_value = inodeproc[inode];

	if (current_value == NULL || current_value->pid != pid) {
		prg_node * newnode = new prg_node;
		newnode->inode = inode;
		newnode->pid   = pid;
		newnode->name  = getprogname(pid);

		inodeproc[inode] = newnode;
		delete current_value;
	}
}

void get_info_by_linkname (const char * pid, const char * linkname) {
	if (strncmp(linkname, "socket:[", 8) == 0) {
		setnode(str2ulong(linkname + 8), str2int(pid));
	}
}

/* updates the `inodeproc' inode-to-prg_node
 * for all inodes belonging to this PID
 * (/proc/pid/fd/42)
 * */
void get_info_for_pid(const char * pid) {
	char dirname[10 + MAX_PID_LENGTH];

	size_t dirlen = 10 + strlen(pid);
	snprintf(dirname, dirlen, "/proc/%s/fd", pid);

	DIR * dir = opendir(dirname);

	if (!dir)
	{
		std::cout << "Couldn't open dir " << dirname << ": " << strerror(errno) << "\n";
		return;
	}

	/* walk through /proc/%s/fd/... */
	dirent * entry;
	while ((entry = readdir(dir))) {
		if (entry->d_type != DT_LNK)
			continue;
		//std::cout << "Looking at: " << entry->d_name << std::endl;

		size_t fromlen = dirlen + strlen(entry->d_name) + 1;
		char fromname[10 + MAX_PID_LENGTH + 1 + MAX_FDLINK];
		snprintf (fromname, fromlen, "%s/%s", dirname, entry->d_name);

		//std::cout << "Linking from: " << fromname << std::endl;

		int linklen = 80;
		char linkname [linklen];
		int usedlen = readlink(fromname, linkname, linklen-1);
		if (usedlen == -1)
		{
			continue;
		}
		assert (usedlen < linklen);
		linkname[usedlen] = '\0';
		get_info_by_linkname (pid, linkname);
	}
	closedir(dir);
}

/* updates the `inodeproc' inode-to-prg_node mapping
 * for all processes in /proc */
void reread_mapping () {
	DIR * proc = opendir ("/proc");

	if (proc == 0) {
		std::cerr << "Error reading /proc, neede to get inode-to-pid-maping\n";
		exit(1);
	}

	dirent * entry;

	while ((entry = readdir(proc))) {
		if (entry->d_type != DT_DIR) continue;

		if (! is_number (entry->d_name)) continue;

		get_info_for_pid(entry->d_name);
	}
	closedir(proc);
}

struct prg_node * findPID (unsigned long inode)
{
	/* we first look in inodeproc */
	struct prg_node * node = inodeproc[inode];

	if (node != NULL)
	{
		if (bughuntmode)
		{
			std::cout << ":) Found pid in inodeproc table" << std::endl;
		}
		return node;
	}

	reread_mapping();

	struct prg_node * retval = inodeproc[inode];
	if (bughuntmode)
	{
		if (retval == NULL)
		{
			std::cout << ":( No pid after inodeproc refresh" << std::endl;
		}
		else
		{
			std::cout << ":) Found pid after inodeproc refresh" << std::endl;
		}
	}
	return retval;
}

void prg_cache_clear() {};

/*void main () {
	std::cout << "Fooo\n";
	reread_mapping();
	std::cout << "Haihai\n";
}*/