/*
    * Copyright 2025 The OSHI Project Contributors
    * SPDX-License-Identifier: MIT
    */
   package oshi.util;
   
   import java.util.Arrays;
   import java.util.HashMap;
   import java.util.List;
  import java.util.Map;
  import java.util.regex.Pattern;
  
  import oshi.annotation.concurrent.ThreadSafe;
  
  @ThreadSafe
  public final class ProcUtil {
  
      private ProcUtil() {
      }
  
      /**
       * Parses /proc files with a given structure consisting of a keyed header line followed by a keyed value line.
       * {@code /proc/net/netstat} and {@code /proc/net/snmp} are specific examples of this. The returned map is of the
       * form {key: {stat: value, stat: value, ...}}. An example of the file structure is:
       *
       * <pre>
       *     TcpExt: SyncookiesSent SyncookiesRecv SyncookiesFailed ...
       *     TcpExt: 0 4 0 ...
       *     IpExt: InNoRoutes InTruncatedPkts InMcastPkts OutMcastPkts ...
       *     IpExt: 55 0 27786 1435 ...
       *     MPTcpExt: MPCapableSYNRX MPCapableSYNTX MPCapableSYNACKRX ...
       *     MPTcpExt: 0 0 0 ...
       * </pre>
       *
       * Which would produce a mapping structure like:
       *
       * <pre>
       *     {
       *         "TcpExt": {"SyncookiesSent":0, "SyncookiesRecv":4, "SyncookiesFailed":0, ... }
       *         "IpExt": {"InNoRoutes":55, "InTruncatedPkts":27786, "InMcastPkts":1435, ... }
       *         "MPTcpExt": {"MPCapableSYNACKRX":0, "MPCapableSYNTX":0, "MPCapableSYNACKRX":0, ... }
       *     }
       * </pre>
       *
       * @param procFile the file to process
       * @param keys     an optional array of keys to return in the outer map. If none are given, all found keys are
       *                 returned.
       * @return a map of keys to stats
       */
      public static Map<String, Map<String, Long>> parseNestedStatistics(String procFile, String... keys) {
          Map<String, Map<String, Long>> result = new HashMap<>();
          List<String> keyList = Arrays.asList(keys);
  
          List<String> lines = FileUtil.readFile(procFile);
          String previousKey = null;
          String[] statNames = null;
  
          for (String line : lines) {
              String[] parts = ParseUtil.whitespaces.split(line);
              if (parts.length == 0) {
                  continue;
              }
  
              // This would happen if the line starts with whitespace
              if (parts[0].isEmpty()) {
                  parts = Arrays.copyOfRange(parts, 1, parts.length);
              }
  
              String key = parts[0].substring(0, parts[0].length() - 1);
  
              if (!keyList.isEmpty() && !keyList.contains(key)) {
                  continue;
              }
  
              if (key.equals(previousKey)) {
                  if (parts.length == statNames.length) {
                      Map<String, Long> stats = new HashMap<>(parts.length - 1);
                      for (int i = 1; i < parts.length; i++) {
                          stats.put(statNames[i], ParseUtil.parseLongOrDefault(parts[i], 0));
                      }
                      result.put(key, stats);
                  }
              } else {
                  statNames = parts;
              }
  
              previousKey = key;
          }
  
          return result;
      }
  
      /**
       * Parses /proc files formatted as "statistic (long)value" to produce a simple mapping. An example would be
       * /proc/net/snmp6. The file format would look like:
       *
       * <pre>
       *    Ip6InReceives             8026
       *    Ip6InHdrErrors            0
      *    Icmp6InMsgs               2
      *    Icmp6InErrors             0
      *    Icmp6OutMsgs              424
      *    Udp6IgnoredMulti          5
      *    Udp6MemErrors             1
      *    UdpLite6InDatagrams       37
      *    UdpLite6NoPorts           1
      * </pre>
      *
      * Which would produce a mapping structure like:
      *
      * <pre>
      *     {
      *         "Ip6InReceives":8026,
      *         "Ip6InHdrErrors":0,
      *         "Icmp6InMsgs":2,
      *         "Icmp6InErrors":0,
      *         ...
      *     }
      * </pre>
      *
      * @param procFile  the file to process
      * @param separator a regex specifying the separator between statistic and value
      * @return a map of statistics and associated values
      */
     public static Map<String, Long> parseStatistics(String procFile, Pattern separator) {
         Map<String, Long> result = new HashMap<>();
         List<String> lines = FileUtil.readFile(procFile);
         for (String line : lines) {
             String[] parts = separator.split(line);
 
             // This would happen if the line starts with the given separator (whitespace?)
             if (parts[0].isEmpty()) {
                 parts = Arrays.copyOfRange(parts, 1, parts.length);
             }
 
             if (parts.length == 2) {
                 result.put(parts[0], ParseUtil.parseLongOrDefault(parts[1], 0));
             }
         }
 
         return result;
     }
 
     /**
      * Overloaded {@link #parseStatistics(String, Pattern)} using a whitespace separator.
      *
      * @param procFile the file to process
      * @return a map of statistics and associated values
      * @see #parseStatistics(String, Pattern)
      */
     public static Map<String, Long> parseStatistics(String procFile) {
         return parseStatistics(procFile, ParseUtil.whitespaces);
     }
 }