/*
    * Copyright 2025 The OSHI Project Contributors
    * SPDX-License-Identifier: MIT
    */
   package oshi.software.os.linux;
   
   import oshi.software.os.ApplicationInfo;
   import oshi.util.ExecutingCommand;
   import oshi.util.ParseUtil;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.LinkedHashSet;
  import java.util.LinkedHashMap;
  import java.util.Set;
  import java.util.regex.Pattern;
  
  public final class LinuxInstalledApps {
  
      private static final Pattern PIPE_PATTERN = Pattern.compile("\\|");
      private static final Map<String, String> PACKAGE_MANAGER_COMMANDS = initializePackageManagerCommands();
  
      private LinuxInstalledApps() {
      }
  
      private static Map<String, String> initializePackageManagerCommands() {
          Map<String, String> commands = new HashMap<>();
  
          if (isPackageManagerAvailable("dpkg")) {
              commands.put("dpkg",
                      "dpkg-query -W -f=${Package}|${Version}|${Architecture}|${Installed-Size}|${db-fsys:Last-Modified}|${Maintainer}|${Source}|${Homepage}\\n");
          } else if (isPackageManagerAvailable("rpm")) {
              commands.put("rpm",
                      "rpm -qa --queryformat %{NAME}|%{VERSION}-%{RELEASE}|%{ARCH}|%{SIZE}|%{INSTALLTIME}|%{PACKAGER}|%{SOURCERPM}|%{URL}\\n");
          }
  
          return commands;
      }
  
      /**
       * Retrieves the list of installed applications on a Linux system. This method determines the appropriate package
       * manager and parses the installed application details.
       *
       * @return A list of {@link ApplicationInfo} objects representing installed applications.
       */
      public static List<ApplicationInfo> queryInstalledApps() {
          List<String> output = fetchInstalledApps();
          return parseLinuxAppInfo(output);
      }
  
      /**
       * Fetches the list of installed applications by executing the appropriate package manager command. The package
       * manager is determined during class initialization and stored in {@code PACKAGE_MANAGER_COMMANDS}. If no supported
       * package manager is found, an empty list is returned.
       *
       * @return A list of strings, where each entry represents an installed application with its details. Returns an
       *         empty list if no supported package manager is available.
       */
      private static List<String> fetchInstalledApps() {
          if (PACKAGE_MANAGER_COMMANDS.isEmpty()) {
              return Collections.emptyList();
          }
  
          // Get the first available package manager's command
          String command = PACKAGE_MANAGER_COMMANDS.values().iterator().next();
          return ExecutingCommand.runNative(command);
      }
  
      private static boolean isPackageManagerAvailable(String packageManager) {
          List<String> result = ExecutingCommand.runNative(packageManager + " --version");
          // If the command executes fine the result is non-empty else empty
          return !result.isEmpty();
      }
  
      private static List<ApplicationInfo> parseLinuxAppInfo(List<String> output) {
          Set<ApplicationInfo> appInfoSet = new LinkedHashSet<>();
  
          for (String line : output) {
              // split by the pipe character
              String[] parts = PIPE_PATTERN.split(line, -1); // -1 to keep empty fields
  
              // Check if we have all 8 fields
              if (parts.length >= 8) {
                  // Additional info map
                  Map<String, String> additionalInfo = new LinkedHashMap<>();
                  additionalInfo.put("architecture", ParseUtil.getStringValueOrUnknown(parts[2]));
                  additionalInfo.put("installedSize", String.valueOf(ParseUtil.parseLongOrDefault(parts[3], 0L)));
                  additionalInfo.put("source", ParseUtil.getStringValueOrUnknown(parts[6]));
                  additionalInfo.put("homepage", ParseUtil.getStringValueOrUnknown(parts[7]));
  
                  ApplicationInfo app = new ApplicationInfo(ParseUtil.getStringValueOrUnknown(parts[0]), // Package name
                          ParseUtil.getStringValueOrUnknown(parts[1]), // Version
                          ParseUtil.getStringValueOrUnknown(parts[5]), // Vendor
                          ParseUtil.parseLongOrDefault(parts[4], 0L), // Date Epoch
                          additionalInfo);
  
                 appInfoSet.add(app);
             }
         }
 
         return new ArrayList<>(appInfoSet);
     }
 }