package org.checkerframework.common.reflection;

import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.MethodInvocationTree;
import java.lang.annotation.Annotation;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Objects;
import java.util.Set;
import javax.lang.model.element.AnnotationMirror;
import javax.lang.model.element.ExecutableElement;
import javax.lang.model.util.Elements;
import org.checkerframework.checker.nullness.qual.Nullable;
import org.checkerframework.common.basetype.BaseAnnotatedTypeFactory;
import org.checkerframework.common.basetype.BaseTypeChecker;
import org.checkerframework.common.reflection.qual.ClassBound;
import org.checkerframework.common.reflection.qual.ClassVal;
import org.checkerframework.common.reflection.qual.GetConstructor;
import org.checkerframework.common.reflection.qual.GetMethod;
import org.checkerframework.common.reflection.qual.MethodVal;
import org.checkerframework.common.reflection.qual.MethodValBottom;
import org.checkerframework.common.reflection.qual.UnknownMethod;
import org.checkerframework.common.value.ValueAnnotatedTypeFactory;
import org.checkerframework.common.value.ValueChecker;
import org.checkerframework.common.value.qual.ArrayLen;
import org.checkerframework.common.value.qual.BottomVal;
import org.checkerframework.common.value.qual.StringVal;
import org.checkerframework.framework.type.AnnotatedTypeMirror;
import org.checkerframework.framework.type.ElementQualifierHierarchy;
import org.checkerframework.framework.type.QualifierHierarchy;
import org.checkerframework.framework.type.treeannotator.ListTreeAnnotator;
import org.checkerframework.framework.type.treeannotator.TreeAnnotator;
import org.checkerframework.javacutil.AnnotationBuilder;
import org.checkerframework.javacutil.AnnotationUtils;
import org.checkerframework.javacutil.TreeUtils;

/** AnnotatedTypeFactory for the MethodVal Checker. */
public class MethodValAnnotatedTypeFactory extends BaseAnnotatedTypeFactory {

  /** {@link UnknownMethod} annotation mirror. */
  private final AnnotationMirror UNKNOWN_METHOD =
      AnnotationBuilder.fromClass(elements, UnknownMethod.class);

  /** An arary length that represents that the length is unknown. */
  private static final int UNKNOWN_PARAM_LENGTH = -1;

  /** A list containing just {@link #UNKNOWN_PARAM_LENGTH}. */
  private static final List<Integer> UNKNOWN_PARAM_LENGTH_LIST =
      Collections.singletonList(UNKNOWN_PARAM_LENGTH);

  /** A list containing just 0. */
  private static List<Integer> ZERO_LIST = Collections.singletonList(0);

  /** A list containing just 1. */
  private static List<Integer> ONE_LIST = Collections.singletonList(1);

  /** An empty String list. */
  private static List<String> EMPTY_STRING_LIST = Collections.emptyList();

  /** The ArrayLen.value argument/element. */
  public final ExecutableElement arrayLenValueElement =
      TreeUtils.getMethod(ArrayLen.class, "value", 0, processingEnv);
  /** The ClassBound.value argument/element. */
  public final ExecutableElement classBoundValueElement =
      TreeUtils.getMethod(ClassBound.class, "value", 0, processingEnv);
  /** The ClassVal.value argument/element. */
  public final ExecutableElement classValValueElement =
      TreeUtils.getMethod(ClassVal.class, "value", 0, processingEnv);
  /** The StringVal.value argument/element. */
  public final ExecutableElement stringValValueElement =
      TreeUtils.getMethod(StringVal.class, "value", 0, processingEnv);

  /**
   * Create a new MethodValAnnotatedTypeFactory.
   *
   * @param checker the type-checker associated with this factory
   */
  public MethodValAnnotatedTypeFactory(BaseTypeChecker checker) {
    super(checker);
    if (this.getClass() == MethodValAnnotatedTypeFactory.class) {
      this.postInit();
    }
  }

  @Override
  protected Set<Class<? extends Annotation>> createSupportedTypeQualifiers() {
    return new HashSet<>(
        Arrays.asList(MethodVal.class, MethodValBottom.class, UnknownMethod.class));
  }

  @Override
  protected void initializeReflectionResolution() {
    boolean debug = "debug".equals(checker.getOption("resolveReflection"));
    reflectionResolver = new DefaultReflectionResolver(checker, this, debug);
  }

  /**
   * Returns the methods that a {@code @MethodVal} represents.
   *
   * @param methodValAnno a {@code @MethodVal} annotation
   * @return the methods that the given {@code @MethodVal} represents
   */
  List<MethodSignature> getListOfMethodSignatures(AnnotationMirror methodValAnno) {
    List<String> methodNames =
        AnnotationUtils.getElementValueArray(
            methodValAnno, methodValMethodNameElement, String.class);
    List<String> classNames =
        AnnotationUtils.getElementValueArray(
            methodValAnno, methodValClassNameElement, String.class);
    List<Integer> params =
        AnnotationUtils.getElementValueArray(methodValAnno, methodValParamsElement, Integer.class);
    List<MethodSignature> list = new ArrayList<>(methodNames.size());
    for (int i = 0; i < methodNames.size(); i++) {
      list.add(new MethodSignature(classNames.get(i), methodNames.get(i), params.get(i)));
    }
    return list;
  }

  /**
   * Creates a {@code @MethodVal} annotation.
   *
   * @param sigs the method signatures that the result should represent
   * @return a {@code @MethodVal} annotation that represents {@code sigs}
   */
  private AnnotationMirror createMethodVal(Set<MethodSignature> sigs) {
    int size = sigs.size();
    List<String> classNames = new ArrayList<>(size);
    List<String> methodNames = new ArrayList<>(size);
    List<Integer> params = new ArrayList<>(size);
    for (MethodSignature sig : sigs) {
      classNames.add(sig.className);
      methodNames.add(sig.methodName);
      params.add(sig.params);
    }
    AnnotationBuilder builder = new AnnotationBuilder(processingEnv, MethodVal.class);
    builder.setValue("className", classNames);
    builder.setValue("methodName", methodNames);
    builder.setValue("params", params);
    return builder.build();
  }

  /**
   * Returns a list of class names for the given tree using the Class Val Checker.
   *
   * @param tree ExpressionTree whose class names are requested
   * @param mustBeExact whether @ClassBound may be read to produce the result; if false,
   *     only @ClassVal may be read
   * @return list of class names or the empty list if no class names were found
   */
  private List<String> getClassNamesFromClassValChecker(ExpressionTree tree, boolean mustBeExact) {
    ClassValAnnotatedTypeFactory classValATF = getTypeFactoryOfSubchecker(ClassValChecker.class);
    AnnotatedTypeMirror classAnno = classValATF.getAnnotatedType(tree);

    AnnotationMirror classValAnno = classAnno.getAnnotation(ClassVal.class);
    if (classValAnno != null) {
      return AnnotationUtils.getElementValueArray(classValAnno, classValValueElement, String.class);
    } else if (mustBeExact) {
      return Collections.emptyList();
    }

    AnnotationMirror classBoundAnno = classAnno.getAnnotation(ClassBound.class);
    if (classBoundAnno != null) {
      return AnnotationUtils.getElementValueArray(
          classBoundAnno, classBoundValueElement, String.class);
    } else {
      return Collections.emptyList();
    }
  }
  /**
   * Returns the string values for the argument passed. The String Values are estimated using the
   * Value Checker.
   *
   * @param arg ExpressionTree whose string values are sought
   * @return string values of arg or the empty list if no values were found
   */
  private List<String> getMethodNamesFromStringArg(ExpressionTree arg) {
    ValueAnnotatedTypeFactory valueATF = getTypeFactoryOfSubchecker(ValueChecker.class);
    AnnotatedTypeMirror valueAnno = valueATF.getAnnotatedType(arg);
    AnnotationMirror annotation = valueAnno.getAnnotation(StringVal.class);
    if (annotation != null) {
      return AnnotationUtils.getElementValueArray(annotation, stringValValueElement, String.class);
    } else {
      return EMPTY_STRING_LIST;
    }
  }

  @Override
  protected QualifierHierarchy createQualifierHierarchy() {
    return new MethodValQualifierHierarchy(this.getSupportedTypeQualifiers(), elements);
  }

  /** MethodValQualifierHierarchy. */
  protected class MethodValQualifierHierarchy extends ElementQualifierHierarchy {

    /**
     * Creates a MethodValQualifierHierarchy from the given classes.
     *
     * @param qualifierClasses classes of annotations that are the qualifiers for this hierarchy
     * @param elements element utils
     */
    protected MethodValQualifierHierarchy(
        Collection<Class<? extends Annotation>> qualifierClasses, Elements elements) {
      super(qualifierClasses, elements);
    }

    /*
     * Determines the least upper bound of a1 and a2. If both are MethodVal
     * annotations, then the least upper bound is the result of
     * concatenating all value lists of a1 and a2.
     */
    @Override
    public @Nullable AnnotationMirror leastUpperBound(AnnotationMirror a1, AnnotationMirror a2) {
      if (!AnnotationUtils.areSameByName(getTopAnnotation(a1), getTopAnnotation(a2))) {
        return null;
      } else if (isSubtype(a1, a2)) {
        return a2;
      } else if (isSubtype(a2, a1)) {
        return a1;
      } else if (AnnotationUtils.areSameByName(a1, a2)) {
        List<MethodSignature> a1Sigs = getListOfMethodSignatures(a1);
        List<MethodSignature> a2Sigs = getListOfMethodSignatures(a2);

        Set<MethodSignature> lubSigs = new HashSet<>(a1Sigs);
        lubSigs.addAll(a2Sigs); // union

        AnnotationMirror result = createMethodVal(lubSigs);
        return result;
      }
      return null;
    }

    @Override
    public @Nullable AnnotationMirror greatestLowerBound(AnnotationMirror a1, AnnotationMirror a2) {
      if (!AnnotationUtils.areSameByName(getTopAnnotation(a1), getTopAnnotation(a2))) {
        return null;
      } else if (isSubtype(a1, a2)) {
        return a1;
      } else if (isSubtype(a2, a1)) {
        return a2;
      } else if (AnnotationUtils.areSameByName(a1, a2)) {
        List<MethodSignature> a1Sigs = getListOfMethodSignatures(a1);
        List<MethodSignature> a2Sigs = getListOfMethodSignatures(a2);

        Set<MethodSignature> lubSigs = new HashSet<>(a1Sigs);
        lubSigs.retainAll(a2Sigs); // intersection

        AnnotationMirror result = createMethodVal(lubSigs);
        return result;
      }
      return null;
    }

    @Override
    public boolean isSubtype(AnnotationMirror subAnno, AnnotationMirror superAnno) {
      if (AnnotationUtils.areSame(subAnno, superAnno)
          || areSameByClass(superAnno, UnknownMethod.class)
          || areSameByClass(subAnno, MethodValBottom.class)) {
        return true;
      }
      if (areSameByClass(subAnno, UnknownMethod.class)
          || areSameByClass(superAnno, MethodValBottom.class)) {
        return false;
      }
      assert areSameByClass(subAnno, MethodVal.class) && areSameByClass(superAnno, MethodVal.class)
          : "Unexpected annotation in MethodVal";
      List<MethodSignature> subSignatures = getListOfMethodSignatures(subAnno);
      List<MethodSignature> superSignatures = getListOfMethodSignatures(superAnno);
      return superSignatures.containsAll(subSignatures);
    }
  }

  @Override
  protected TreeAnnotator createTreeAnnotator() {
    return new ListTreeAnnotator(new MethodValTreeAnnotator(this), super.createTreeAnnotator());
  }

  /** TreeAnnotator with the visitMethodInvocation method overridden. */
  protected class MethodValTreeAnnotator extends TreeAnnotator {

    protected MethodValTreeAnnotator(MethodValAnnotatedTypeFactory factory) {
      super(factory);
    }

    /*
     * Special handling of getMethod and getDeclaredMethod calls. Attempts
     * to get the annotation on the Class object receiver to get the
     * className, the annotation on the String argument to get the
     * methodName, and the parameters argument to get the param, and then
     * builds a new MethodVal annotation from these
     */
    @Override
    public Void visitMethodInvocation(MethodInvocationTree tree, AnnotatedTypeMirror type) {

      List<String> methodNames;
      List<Integer> params;
      List<String> classNames;
      if (isGetConstructorMethodInvocation(tree)) {
        // method name for constructors is always <init>
        methodNames = ReflectionResolver.INIT_LIST;
        params = getConstructorParamsLen(tree.getArguments());
        classNames = getClassNamesFromClassValChecker(TreeUtils.getReceiverTree(tree), true);

      } else if (isGetMethodMethodInvocation(tree)) {
        ExpressionTree methodNameArg = tree.getArguments().get(0);
        methodNames = getMethodNamesFromStringArg(methodNameArg);
        params = getMethodParamsLen(tree.getArguments());
        classNames = getClassNamesFromClassValChecker(TreeUtils.getReceiverTree(tree), false);
      } else {
        // Not a covered method invocation
        return null;
      }

      // Create MethodVal
      if (methodNames.isEmpty() || classNames.isEmpty()) {
        // No method name or classname is found, it could be any
        // class or method, so, return @UnknownMethod.
        type.replaceAnnotation(UNKNOWN_METHOD);
        return null;
      }

      Set<MethodSignature> methodSigs = new HashSet<>();
      // The possible method signatures are the Cartesian product of all
      // found class, method, and parameter lengths
      for (String methodName : methodNames) {
        for (String className : classNames) {
          for (Integer param : params) {
            methodSigs.add(new MethodSignature(className, methodName, param));
          }
        }
      }

      AnnotationMirror newQual = createMethodVal(methodSigs);
      type.replaceAnnotation(newQual);
      return null;
    }

    /**
     * Returns true if the method being invoked is annotated with @GetConstructor. An example of
     * such a method is Class.getConstructor.
     */
    private boolean isGetConstructorMethodInvocation(MethodInvocationTree tree) {
      return getDeclAnnotation(TreeUtils.elementFromTree(tree), GetConstructor.class) != null;
    }

    /**
     * Returns true if the method being invoked is annotated with @GetMethod. An example of such a
     * method is Class.getMethod.
     */
    private boolean isGetMethodMethodInvocation(MethodInvocationTree tree) {
      return getDeclAnnotation(TreeUtils.elementFromTree(tree), GetMethod.class) != null;
    }

    /**
     * Returns a singleton list containing the number of parameters for a call to a method annotated
     * with {@code @}{@link GetMethod}.
     *
     * @param args arguments to a call to a method such as {@code getMethod}
     * @return the number of parameters
     */
    private List<Integer> getMethodParamsLen(List<? extends ExpressionTree> args) {
      assert !args.isEmpty() : "getMethod must have at least one parameter";

      // Number of parameters in the created method object
      int numParams = args.size() - 1;
      if (numParams == 1) {
        return getNumberOfParameterOneArg(args.get(1));
      }
      return Collections.singletonList(numParams);
    }

    /**
     * Returns a singleton list containing the number of parameters for a call to a method annotated
     * with {@code @}{@link GetConstructor}.
     *
     * @param args arguments to a call to a method such as {@code getConstructor}
     * @return the number of parameters
     */
    private List<Integer> getConstructorParamsLen(List<? extends ExpressionTree> args) {
      // Number of parameters in the created method object
      int numParams = args.size();
      if (numParams == 1) {
        return getNumberOfParameterOneArg(args.get(0));
      }
      return Collections.singletonList(numParams);
    }

    /**
     * if getMethod(Object receiver, Object... params) or getConstrutor(Object... params) have one
     * argument for params, then the number of parameters in the underlying method or constructor
     * must be:
     *
     * <ul>
     *   <li>0: if the argument is null
     *   <li>x: if the argument is an array with @ArrayLen(x); note that x might be a set rather
     *       than a single value
     *   <li>UNKNOWN_PARAM_LENGTH: if the argument is an array with @UnknownVal
     *   <li>1: otherwise
     * </ul>
     *
     * @param argument the single argument in a call to {@code getMethod} or {@code getConstrutor}
     * @return a list, each of whose elementts is a possible the number of parameters; it is often,
     *     but not always, a singleton list
     */
    private List<Integer> getNumberOfParameterOneArg(ExpressionTree argument) {
      AnnotatedTypeMirror atm = atypeFactory.getAnnotatedType(argument);
      switch (atm.getKind()) {
        case ARRAY:
          ValueAnnotatedTypeFactory valueATF = getTypeFactoryOfSubchecker(ValueChecker.class);
          AnnotatedTypeMirror valueType = valueATF.getAnnotatedType(argument);
          AnnotationMirror arrayLenAnno = valueType.getAnnotation(ArrayLen.class);
          if (arrayLenAnno != null) {
            return AnnotationUtils.getElementValueArray(
                arrayLenAnno, arrayLenValueElement, Integer.class);
          } else if (valueType.getAnnotation(BottomVal.class) != null) {
            // happens in this case: (Class[]) null
            return ZERO_LIST;
          }
          // the argument is an array with unknown array length
          return UNKNOWN_PARAM_LENGTH_LIST;
        case NULL:
          // null is treated as the empty list of parameters, so size is 0.
          return ZERO_LIST;
        default:
          // The argument is not an array or null, so it must be a class.
          return ONE_LIST;
      }
    }
  }
}

/**
 * An object that represents a the tuple that identifies a method signature: (fully qualified class
 * name, method name, number of parameters).
 */
class MethodSignature {
  String className;
  String methodName;
  int params;

  public MethodSignature(String className, String methodName, int params) {
    this.className = className;
    this.methodName = methodName;
    this.params = params;
  }

  @Override
  public int hashCode() {
    return Objects.hash(className, methodName, params);
  }

  @Override
  public boolean equals(@Nullable Object obj) {
    if (this == obj) {
      return true;
    }
    if (obj == null) {
      return false;
    }
    if (getClass() != obj.getClass()) {
      return false;
    }
    MethodSignature other = (MethodSignature) obj;
    if (className == null) {
      if (other.className != null) {
        return false;
      }
    } else if (!className.equals(other.className)) {
      return false;
    }
    if (methodName == null) {
      if (other.methodName != null) {
        return false;
      }
    } else if (!methodName.equals(other.methodName)) {
      return false;
    }
    if (params != other.params) {
      return false;
    }
    return true;
  }

  @Override
  public String toString() {
    return "MethodSignature [className="
        + className
        + ", methodName="
        + methodName
        + ", params="
        + params
        + "]";
  }
}