/*
    * SPDX-FileCopyrightText: Copyright (c) 2011-2025 Yegor Bugayenko
    * SPDX-License-Identifier: MIT
    */
   package com.qulice.pmd.rules;
   
   import java.util.List;
   import java.util.Map;
   import net.sourceforge.pmd.lang.java.ast.ASTArgumentList;
  import net.sourceforge.pmd.lang.java.ast.ASTMethodDeclaration;
  import net.sourceforge.pmd.lang.java.ast.ASTReturnStatement;
  import net.sourceforge.pmd.lang.java.ast.ASTVariableDeclarator;
  import net.sourceforge.pmd.lang.java.ast.JavaNode;
  import net.sourceforge.pmd.lang.java.rule.AbstractJavaRule;
  import net.sourceforge.pmd.lang.symboltable.NameDeclaration;
  import net.sourceforge.pmd.lang.symboltable.NameOccurrence;
  
  /**
   * Rule to check unnecessary local variables.
   *
   * @since 0.4
   */
  public final class UnnecessaryLocalRule extends AbstractJavaRule {
      @Override
      public Object visit(final ASTMethodDeclaration meth, final Object data) {
          Object ndata = data;
          if (!meth.isAbstract() && !meth.isNative()) {
              ndata = super.visit(meth, data);
          }
          return ndata;
      }
  
      @Override
      public Object visit(final ASTReturnStatement rtn, final Object data) {
          final ASTVariableDeclarator name =
              rtn.getFirstChildOfType(ASTVariableDeclarator.class);
          if (name != null) {
              this.usages(rtn, data, name);
          }
          return data;
      }
  
      @Override
      public Object visit(final ASTArgumentList rtn, final Object data) {
          final List<ASTVariableDeclarator> names =
              rtn.findChildrenOfType(ASTVariableDeclarator.class);
          for (final ASTVariableDeclarator name : names) {
              this.usages(rtn, data, name);
          }
          return data;
      }
  
      /**
       * Report when number of variable usages is equal to zero.
       * @param node Node to check.
       * @param data Context.
       * @param name Variable name.
       */
      private void usages(final JavaNode node, final Object data,
          final ASTVariableDeclarator name) {
          final Map<NameDeclaration, List<NameOccurrence>> vars = name
              .getScope().getDeclarations();
          for (final Map.Entry<NameDeclaration, List<NameOccurrence>> entry
              : vars.entrySet()) {
              final List<NameOccurrence> usages = entry.getValue();
              if (usages.size() > 1) {
                  continue;
              }
              for (final NameOccurrence occ: usages) {
                  if (occ.getLocation().equals(name)) {
                      this.asCtx(data).addViolation(
                          node, name.getImage()
                      );
                  }
              }
          }
      }
  }