/*
    * SPDX-FileCopyrightText: Copyright (c) 2011-2026 Yegor Bugayenko
    * SPDX-License-Identifier: MIT
    */
   package com.qulice.pmd.rules;
   
   import net.sourceforge.pmd.lang.java.ast.ASTArgumentList;
   import net.sourceforge.pmd.lang.java.ast.ASTMethodCall;
   import net.sourceforge.pmd.lang.java.rule.AbstractJavaRulechainRule;
  import net.sourceforge.pmd.lang.java.types.InvocationMatcher;
  
  /**
   * Rule to flag {@code Arrays.asList} invocations that are passed a single
   * non-array argument. {@code Arrays.asList(x)} where {@code x} is a scalar
   * (e.g. an {@code int}, a {@code String} or any non-array reference) ends
   * up allocating a backing one-element array via varargs and a wrapper list
   * around it. {@code Collections.singletonList(x)} expresses the same intent
   * with a single, immutable, fixed-size list and no implicit array
   * allocation. A single array argument is not flagged because that form
   * either spreads the array's elements (for reference arrays) or wraps the
   * array itself in a one-element list (for primitive arrays), and either
   * behaviour may be intentional.
   * @since 0.26.0
   */
  public final class UseCollectionsSingletonListRule
      extends AbstractJavaRulechainRule {
  
      /**
       * Matcher for any invocation of {@code java.util.Arrays.asList}.
       */
      private static final InvocationMatcher AS_LIST =
          InvocationMatcher.parse("java.util.Arrays#asList(_*)");
  
      public UseCollectionsSingletonListRule() {
          super(ASTMethodCall.class);
      }
  
      @Override
      public Object visit(final ASTMethodCall call, final Object data) {
          if (UseCollectionsSingletonListRule.shouldUseSingletonList(call)) {
              this.asCtx(data).addViolation(call);
          }
          return data;
      }
  
      private static boolean shouldUseSingletonList(final ASTMethodCall call) {
          boolean result = false;
          if (UseCollectionsSingletonListRule.AS_LIST.matchesCall(call)) {
              final ASTArgumentList args = call.getArguments();
              result = args.size() == 1
                  && !args.get(0).getTypeMirror().isArray();
          }
          return result;
      }
  }