/*
    * Copyright 2020-2023 The OSHI Project Contributors
    * SPDX-License-Identifier: MIT
    */
   package oshi.software.os.linux;
   
   import static oshi.software.os.OSProcess.State.INVALID;
   import static oshi.software.os.OSThread.ThreadFiltering.VALID_THREAD;
   import static oshi.util.Memoizer.memoize;
  
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.math.BigInteger;
  import java.nio.file.Files;
  import java.nio.file.InvalidPathException;
  import java.nio.file.Path;
  import java.nio.file.Paths;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.List;
  import java.util.Locale;
  import java.util.Map;
  import java.util.Optional;
  import java.util.function.Supplier;
  import java.util.stream.Collectors;
  
  import com.sun.jna.platform.unix.Resource;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import oshi.annotation.concurrent.ThreadSafe;
  import oshi.driver.linux.proc.ProcessStat;
  import oshi.jna.platform.linux.LinuxLibc;
  import oshi.software.common.AbstractOSProcess;
  import oshi.software.os.OSThread;
  import oshi.util.ExecutingCommand;
  import oshi.util.FileUtil;
  import oshi.util.GlobalConfig;
  import oshi.util.ParseUtil;
  import oshi.util.UserGroupInfo;
  import oshi.util.Util;
  import oshi.util.platform.linux.ProcPath;
  
  /**
   * OSProcess implementation
   */
  @ThreadSafe
  public class LinuxOSProcess extends AbstractOSProcess {
  
      private static final Logger LOG = LoggerFactory.getLogger(LinuxOSProcess.class);
  
      private static final boolean LOG_PROCFS_WARNING = GlobalConfig.get(GlobalConfig.OSHI_OS_LINUX_PROCFS_LOGWARNING,
              false);
  
      // Get a list of orders to pass to ParseUtil
      private static final int[] PROC_PID_STAT_ORDERS = new int[ProcPidStat.values().length];
  
      static {
          for (ProcPidStat stat : ProcPidStat.values()) {
              // The PROC_PID_STAT enum indices are 1-indexed.
              // Subtract one to get a zero-based index
              PROC_PID_STAT_ORDERS[stat.ordinal()] = stat.getOrder() - 1;
          }
      }
  
      private final LinuxOperatingSystem os;
  
      private Supplier<Integer> bitness = memoize(this::queryBitness);
      private Supplier<String> commandLine = memoize(this::queryCommandLine);
      private Supplier<List<String>> arguments = memoize(this::queryArguments);
      private Supplier<Map<String, String>> environmentVariables = memoize(this::queryEnvironmentVariables);
      private Supplier<String> user = memoize(this::queryUser);
      private Supplier<String> group = memoize(this::queryGroup);
  
      private String name;
      private String path = "";
      private String userID;
      private String groupID;
      private State state = INVALID;
      private int parentProcessID;
      private int threadCount;
      private int priority;
      private long virtualSize;
      private long residentSetSize;
      private long kernelTime;
      private long userTime;
      private long startTime;
      private long upTime;
      private long bytesRead;
      private long bytesWritten;
      private long minorFaults;
      private long majorFaults;
      private long contextSwitches;
  
      public LinuxOSProcess(int pid, LinuxOperatingSystem os) {
          super(pid);
          this.os = os;
         updateAttributes();
     }
 
     @Override
     public String getName() {
         return this.name;
     }
 
     @Override
     public String getPath() {
         return this.path;
     }
 
     @Override
     public String getCommandLine() {
         return commandLine.get();
     }
 
     private String queryCommandLine() {
         return Arrays.stream(FileUtil
                 .getStringFromFile(String.format(Locale.ROOT, ProcPath.PID_CMDLINE, getProcessID())).split("\0"))
                 .collect(Collectors.joining(" "));
     }
 
     @Override
     public List<String> getArguments() {
         return arguments.get();
     }
 
     private List<String> queryArguments() {
         return Collections.unmodifiableList(ParseUtil.parseByteArrayToStrings(
                 FileUtil.readAllBytes(String.format(Locale.ROOT, ProcPath.PID_CMDLINE, getProcessID()), LOG_PROCFS_WARNING)));
     }
 
     @Override
     public Map<String, String> getEnvironmentVariables() {
         return environmentVariables.get();
     }
 
     private Map<String, String> queryEnvironmentVariables() {
         return Collections.unmodifiableMap(ParseUtil.parseByteArrayToStringMap(FileUtil
                 .readAllBytes(String.format(Locale.ROOT, ProcPath.PID_ENVIRON, getProcessID()), LOG_PROCFS_WARNING)));
     }
 
     @Override
     public String getCurrentWorkingDirectory() {
         try {
             String cwdLink = String.format(Locale.ROOT, ProcPath.PID_CWD, getProcessID());
             String cwd = new File(cwdLink).getCanonicalPath();
             if (!cwd.equals(cwdLink)) {
                 return cwd;
             }
         } catch (IOException e) {
             LOG.trace("Couldn't find cwd for pid {}: {}", getProcessID(), e.getMessage());
         }
         return "";
     }
 
     @Override
     public String getUser() {
         return user.get();
     }
 
     private String queryUser() {
         return UserGroupInfo.getUser(userID);
     }
 
     @Override
     public String getUserID() {
         return this.userID;
     }
 
     @Override
     public String getGroup() {
         return group.get();
     }
 
     private String queryGroup() {
         return UserGroupInfo.getGroupName(groupID);
     }
 
     @Override
     public String getGroupID() {
         return this.groupID;
     }
 
     @Override
     public State getState() {
         return this.state;
     }
 
     @Override
     public int getParentProcessID() {
         return this.parentProcessID;
     }
 
     @Override
     public int getThreadCount() {
         return this.threadCount;
     }
 
     @Override
     public int getPriority() {
         return this.priority;
     }
 
     @Override
     public long getVirtualSize() {
         return this.virtualSize;
     }
 
     @Override
     public long getResidentSetSize() {
         return this.residentSetSize;
     }
 
     @Override
     public long getKernelTime() {
         return this.kernelTime;
     }
 
     @Override
     public long getUserTime() {
         return this.userTime;
     }
 
     @Override
     public long getUpTime() {
         return this.upTime;
     }
 
     @Override
     public long getStartTime() {
         return this.startTime;
     }
 
     @Override
     public long getBytesRead() {
         return this.bytesRead;
     }
 
     @Override
     public long getBytesWritten() {
         return this.bytesWritten;
     }
 
     @Override
     public List<OSThread> getThreadDetails() {
         return ProcessStat.getThreadIds(getProcessID()).stream().parallel()
                 .map(id -> new LinuxOSThread(getProcessID(), id)).filter(VALID_THREAD).collect(Collectors.toList());
     }
 
     @Override
     public long getMinorFaults() {
         return this.minorFaults;
     }
 
     @Override
     public long getMajorFaults() {
         return this.majorFaults;
     }
 
     @Override
     public long getContextSwitches() {
         return this.contextSwitches;
     }
 
     @Override
     public long getOpenFiles() {
         return ProcessStat.getFileDescriptorFiles(getProcessID()).length;
     }
 
     @Override
     public long getSoftOpenFileLimit() {
         if (getProcessID() == this.os.getProcessId()) {
             final Resource.Rlimit rlimit = new Resource.Rlimit();
             LinuxLibc.INSTANCE.getrlimit(LinuxLibc.RLIMIT_NOFILE, rlimit);
             return rlimit.rlim_cur;
         } else {
             return getProcessOpenFileLimit(getProcessID(), 1);
         }
     }
 
     @Override
     public long getHardOpenFileLimit() {
         if (getProcessID() == this.os.getProcessId()) {
             final Resource.Rlimit rlimit = new Resource.Rlimit();
             LinuxLibc.INSTANCE.getrlimit(LinuxLibc.RLIMIT_NOFILE, rlimit);
             return rlimit.rlim_max;
         } else {
             return getProcessOpenFileLimit(getProcessID(), 2);
         }
     }
 
     @Override
     public int getBitness() {
         return this.bitness.get();
     }
 
     private int queryBitness() {
         // get 5th byte of file for 64-bit check
         // https://en.wikipedia.org/wiki/Executable_and_Linkable_Format#File_header
         byte[] buffer = new byte[5];
         if (!path.isEmpty()) {
             try (InputStream is = new FileInputStream(path)) {
                 if (is.read(buffer) == buffer.length) {
                     return buffer[4] == 1 ? 32 : 64;
                 }
             } catch (IOException e) {
                 LOG.warn("Failed to read process file: {}", path);
             }
         }
         return 0;
     }
 
     @Override
     public long getAffinityMask() {
         // Would prefer to use native sched_getaffinity call but variable sizing is
         // kernel-dependent and requires C macros, so we use command line instead.
         String mask = ExecutingCommand.getFirstAnswer("taskset -p " + getProcessID());
         // Output:
         // pid 3283's current affinity mask: 3
         // pid 9726's current affinity mask: f
         String[] split = ParseUtil.whitespaces.split(mask);
         try {
             return new BigInteger(split[split.length - 1], 16).longValue();
         } catch (NumberFormatException e) {
             return 0;
         }
     }
 
     @Override
     public boolean updateAttributes() {
         String procPidExe = String.format(Locale.ROOT, ProcPath.PID_EXE, getProcessID());
         try {
             Path link = Paths.get(procPidExe);
             this.path = Files.readSymbolicLink(link).toString();
             // For some services the symbolic link process has terminated
             int index = path.indexOf(" (deleted)");
             if (index != -1) {
                 path = path.substring(0, index);
             }
         } catch (InvalidPathException | IOException | UnsupportedOperationException | SecurityException e) {
             LOG.debug("Unable to open symbolic link {}", procPidExe);
         }
         // Fetch all the values here
         // check for terminated process race condition after last one.
         Map<String, String> io = FileUtil
                 .getKeyValueMapFromFile(String.format(Locale.ROOT, ProcPath.PID_IO, getProcessID()), ":");
         Map<String, String> status = FileUtil
                 .getKeyValueMapFromFile(String.format(Locale.ROOT, ProcPath.PID_STATUS, getProcessID()), ":");
         String stat = FileUtil.getStringFromFile(String.format(Locale.ROOT, ProcPath.PID_STAT, getProcessID()));
         if (stat.isEmpty()) {
             this.state = INVALID;
             return false;
         }
         // If some details couldn't be read from ProcPath.PID_STATUS try reading it from
         // ProcPath.PID_STAT
         getMissingDetails(status, stat);
 
         long now = System.currentTimeMillis();
 
         // We can get name and status more easily from /proc/pid/status which we
         // call later, so just get the numeric bits here
         // See man proc for how to parse /proc/[pid]/stat
         long[] statArray = ParseUtil.parseStringToLongArray(stat, PROC_PID_STAT_ORDERS,
                 ProcessStat.PROC_PID_STAT_LENGTH, ' ');
 
         // BOOTTIME is in seconds and start time from proc/pid/stat is in jiffies.
         // Combine units to jiffies and convert to millijiffies before hz division to
         // avoid precision loss without having to cast
         this.startTime = (LinuxOperatingSystem.BOOTTIME * LinuxOperatingSystem.getHz()
                 + statArray[ProcPidStat.START_TIME.ordinal()]) * 1000L / LinuxOperatingSystem.getHz();
         // BOOT_TIME could be up to 500ms off and start time up to 5ms off. A process
         // that has started within last 505ms could produce a future start time/negative
         // up time, so insert a sanity check.
         if (startTime >= now) {
             startTime = now - 1;
         }
         this.parentProcessID = (int) statArray[ProcPidStat.PPID.ordinal()];
         this.threadCount = (int) statArray[ProcPidStat.THREAD_COUNT.ordinal()];
         this.priority = (int) statArray[ProcPidStat.PRIORITY.ordinal()];
         this.virtualSize = statArray[ProcPidStat.VSZ.ordinal()];
         this.residentSetSize = statArray[ProcPidStat.RSS.ordinal()] * LinuxOperatingSystem.getPageSize();
         this.kernelTime = statArray[ProcPidStat.KERNEL_TIME.ordinal()] * 1000L / LinuxOperatingSystem.getHz();
         this.userTime = statArray[ProcPidStat.USER_TIME.ordinal()] * 1000L / LinuxOperatingSystem.getHz();
         this.minorFaults = statArray[ProcPidStat.MINOR_FAULTS.ordinal()];
         this.majorFaults = statArray[ProcPidStat.MAJOR_FAULTS.ordinal()];
         long nonVoluntaryContextSwitches = ParseUtil.parseLongOrDefault(status.get("nonvoluntary_ctxt_switches"), 0L);
         long voluntaryContextSwitches = ParseUtil.parseLongOrDefault(status.get("voluntary_ctxt_switches"), 0L);
         this.contextSwitches = voluntaryContextSwitches + nonVoluntaryContextSwitches;
 
         this.upTime = now - startTime;
 
         // See man proc for how to parse /proc/[pid]/io
         this.bytesRead = ParseUtil.parseLongOrDefault(io.getOrDefault("read_bytes", ""), 0L);
         this.bytesWritten = ParseUtil.parseLongOrDefault(io.getOrDefault("write_bytes", ""), 0L);
 
         // Don't set open files or bitness or currentWorkingDirectory; fetch on demand.
 
         this.userID = ParseUtil.whitespaces.split(status.getOrDefault("Uid", ""))[0];
         // defer user lookup until asked
         this.groupID = ParseUtil.whitespaces.split(status.getOrDefault("Gid", ""))[0];
         // defer group lookup until asked
         this.name = status.getOrDefault("Name", "");
         this.state = ProcessStat.getState(status.getOrDefault("State", "U").charAt(0));
         return true;
     }
 
     /**
      * If some details couldn't be read from ProcPath.PID_STATUS try reading it from ProcPath.PID_STAT
      *
      * @param status status map to fill.
      * @param stat   string to read from.
      */
     private static void getMissingDetails(Map<String, String> status, String stat) {
         if (status == null || stat == null) {
             return;
         }
 
         int nameStart = stat.indexOf('(');
         int nameEnd = stat.indexOf(')');
         if (Util.isBlank(status.get("Name")) && nameStart > 0 && nameStart < nameEnd) {
             // remove leading and trailing parentheses
             String statName = stat.substring(nameStart + 1, nameEnd);
             status.put("Name", statName);
         }
 
         // As per man, the next item after the name is the state
         if (Util.isBlank(status.get("State")) && nameEnd > 0 && stat.length() > nameEnd + 2) {
             String statState = String.valueOf(stat.charAt(nameEnd + 2));
             status.put("State", statState);
         }
     }
 
     /**
      * Enum used to update attributes. The order field represents the 1-indexed numeric order of the stat in
      * /proc/pid/stat per the man file.
      */
     private enum ProcPidStat {
         // The parsing implementation in ParseUtil requires these to be declared
         // in increasing order
         PPID(4), MINOR_FAULTS(10), MAJOR_FAULTS(12), USER_TIME(14), KERNEL_TIME(15), PRIORITY(18), THREAD_COUNT(20),
         START_TIME(22), VSZ(23), RSS(24);
 
         private final int order;
 
         public int getOrder() {
             return this.order;
         }
 
         ProcPidStat(int order) {
             this.order = order;
         }
     }
 
     private long getProcessOpenFileLimit(long processId, int index) {
         final String limitsPath = String.format(Locale.ROOT, "/proc/%d/limits", processId);
         if (!Files.exists(Paths.get(limitsPath))) {
             return -1; // not supported
         }
         final List<String> lines = FileUtil.readFile(limitsPath);
         final Optional<String> maxOpenFilesLine = lines.stream().filter(line -> line.startsWith("Max open files"))
                 .findFirst();
         if (!maxOpenFilesLine.isPresent()) {
             return -1;
         }
 
         // Split all non-Digits away -> ["", "{soft-limit}, "{hard-limit}"]
         final String[] split = maxOpenFilesLine.get().split("\\D+");
         return ParseUtil.parseLongOrDefault(split[index], -1);
     }
 }