/*
 * Copyright 2012 The Error Prone Authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.errorprone.bugpatterns;

import com.google.errorprone.CompilationTestHelper;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;

/** Tests for {@link NonOverridingEquals}. */
// TODO(eaftan): Tests for correctness of suggested fix
@RunWith(JUnit4.class)
public class NonOverridingEqualsTest {
  private final CompilationTestHelper compilationHelper =
      CompilationTestHelper.newInstance(NonOverridingEquals.class, getClass());

  // Positive cases

  @Test
  public void flagsSimpleCovariantEqualsMethod() {
    compilationHelper
        .addSourceLines(
            "Test.java",
            """
            public class Test {
              // BUG: Diagnostic contains: Did you mean '@Override'
              public boolean equals(Test other) {
                return false;
              }
            }
            """)
        .doTest();
  }

  // The following two tests are really to help debug the construction of the suggested fixes.

  @Test
  public void flagsComplicatedCovariantEqualsMethod() {
    compilationHelper
        .addSourceLines(
            "Test.java",
            """
            public class Test {
              int i, j, k;

              // BUG: Diagnostic contains: Did you mean '@Override'
              public boolean equals(Test other) {
                if (i == other.i && j == other.j && k == other.k) {
                  return true;
                }
                return false;
              }
            }
            """)
        .doTest();
  }

  @Test
  public void flagsAnotherComplicatedCovariantEqualsMethod() {
    compilationHelper
        .addSourceLines(
            "Test.java",
            """
            public class Test {
              boolean isInVersion;
              String str;

              // BUG: Diagnostic contains: Did you mean '@Override'
              public boolean equals(Test that) {
                return (this.isInVersion == that.isInVersion) && this.str.equals(that.str);
              }
            }
            """)
        .doTest();
  }

  @Test
  public void flagsAbstractCovariantEqualsMethod() {
    compilationHelper
        .addSourceLines(
            "Test.java",
            """
            public abstract class Test {
              // BUG: Diagnostic contains: Did you mean '@Override'
              public abstract boolean equals(Test other);
            }
            """)
        .doTest();
  }

  @Test
  public void flagsNativeCovariantEqualsMethod() {
    compilationHelper
        .addSourceLines(
            "Test.java",
            """
            public class Test {
              // BUG: Diagnostic contains: Did you mean '@Override'
              public native boolean equals(Test other);
            }
            """)
        .doTest();
  }

  @Test
  public void flagsIfMethodTakesUnrelatedType() {
    compilationHelper
        .addSourceLines(
            "Test.java",
            """
            public class Test {
              // BUG: Diagnostic contains:
              public boolean equals(Integer other) {
                return false;
              }
            }
            """)
        .doTest();
  }

  @Test
  public void flagsBoxedBooleanReturnType() {
    compilationHelper
        .addSourceLines(
            "Test.java",
            """
            public class Test {
              // BUG: Diagnostic contains:
              public Boolean equals(Test other) {
                return false;
              }
            }
            """)
        .doTest();
  }

  @Test
  public void flagsCovariantEqualsMethodInEnum() {
    compilationHelper
        .addSourceLines(
            "Planet.java",
"""
public enum Planet {
  MERCURY,
  VENUS,
  EARTH,
  MARS,
  JUPITER,
  SATURN,
  URANUS,
  NEPTUNE;

  // BUG: Diagnostic contains: enum instances can safely be compared by reference equality
  // Did you mean to remove this line?
  public boolean equals(Planet other) {
    return this == other;
  }
}
""")
        .doTest();
  }

  @Test
  public void flagsPrivateEqualsMethod() {
    compilationHelper
        .addSourceLines(
            "Test.java",
            """
            public class Test {
              // BUG: Diagnostic contains:
              private boolean equals(Test other) {
                return false;
              }
            }
            """)
        .doTest();
  }

  @Test
  public void flagsEvenIfAnotherMethodOverridesEquals() {
    compilationHelper
        .addSourceLines(
            "Test.java",
            """
            public class Test {
              // BUG: Diagnostic contains: either inline it into the callers or rename it
              private boolean equals(Test other) {
                return false;
              }

              @Override
              public boolean equals(Object other) {
                return false;
              }
            }
            """)
        .doTest();
  }

  /**
   * A static method can be invoked on an instance, so a static equals method with one argument
   * could be confused with Object#equals. Though I can't imagine how anyone would define a
   * single-argument static equals method...
   */
  @Test
  public void flagsStaticEqualsMethod() {
    compilationHelper
        .addSourceLines(
            "Test.java",
            """
            public class Test {
              // BUG: Diagnostic contains:
              public static boolean equals(Test other) {
                return false;
              }
            }
            """)
        .doTest();
  }

  // Negative cases

  @Test
  public void dontFlagMethodThatOverridesEquals() {
    compilationHelper
        .addSourceLines(
            "Test.java",
            """
            public class Test {
              @Override
              public boolean equals(Object other) {
                return false;
              }
            }
            """)
        .doTest();
  }

  @Test
  public void dontFlagEqualsMethodWithMoreThanOneParameter() {
    compilationHelper
        .addSourceLines(
            "Test.java",
            """
            public class Test {
              public boolean equals(Test other, String s) {
                return false;
              }
            }
            """)
        .doTest();
  }

  @Test
  public void dontFlagIfWrongReturnType() {
    compilationHelper
        .addSourceLines(
            "Test.java",
            """
            public class Test {
              public int equals(Test other) {
                return -1;
              }
            }
            """)
        .doTest();
  }
}
