/*
 * Copyright (c) 2012-2018 Institut National des Sciences Appliquées de Lyon (INSA Lyon) and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * SPDX-License-Identifier: EPL-2.0
 */

package org.eclipse.golo.runtime.adapters;

import gololang.FunctionReference;

import java.lang.reflect.Method;
import java.util.*;

import static java.lang.invoke.MethodType.genericMethodType;
import static java.lang.reflect.Modifier.*;
import static java.util.Collections.unmodifiableMap;
import static java.util.Collections.unmodifiableSet;

public final class AdapterDefinition {

  private final ClassLoader classLoader;
  private final String name;
  private final String parent;
  private final TreeSet<String> interfaces = new TreeSet<>();
  private final LinkedHashMap<String, FunctionReference> implementations = new LinkedHashMap<>();
  private final LinkedHashMap<String, FunctionReference> overrides = new LinkedHashMap<>();

  public AdapterDefinition(ClassLoader classLoader, String name, String parent) {
    this.classLoader = classLoader;
    this.name = name;
    this.parent = parent;
  }

  public ClassLoader getClassLoader() {
    return classLoader;
  }

  public String getName() {
    return name;
  }

  public String getParent() {
    return parent;
  }

  public Set<String> getInterfaces() {
    return unmodifiableSet(interfaces);
  }

  public Map<String, FunctionReference> getImplementations() {
    return unmodifiableMap(implementations);
  }

  public Map<String, FunctionReference> getOverrides() {
    return unmodifiableMap(overrides);
  }

  public AdapterDefinition implementsInterface(String iface) {
    interfaces.add(iface);
    return this;
  }

  public AdapterDefinition implementsMethod(String name, FunctionReference target) throws AdapterDefinitionProblem {
    checkForImplementation(target);
    checkStarImplementationType(name, target);
    implementations.put(name, target);
    return this;
  }

  public AdapterDefinition overridesMethod(String name, FunctionReference target) throws AdapterDefinitionProblem {
    checkForOverriding(target);
    checkStarOverrideType(name, target);
    overrides.put(name, target);
    return this;
  }

  public boolean hasStarImplementation() {
    return implementations.containsKey("*");
  }

  public boolean hasStarOverride() {
    return overrides.containsKey("*");
  }

  public AdapterDefinition validate() throws AdapterDefinitionProblem {
    checkSuperTypesExistence();
    checkStarConflict();
    checkMethodsToBeImplemented();
    checkOverridesImplementationsConflict();
    checkAllOverridesAndImplementationsExist();
    return this;
  }

  private void checkOverridesImplementationsConflict() {
    for (String key : implementations.keySet()) {
      if (!"*".equals(key) && overrides.containsKey(key)) {
        throw new AdapterDefinitionProblem("Conflict: there is both an implementation and an override for method " + key);
      }
    }
  }

  private void checkStarImplementationType(String name, FunctionReference target) {
    if ("*".equals(name) && !target.type().equals(genericMethodType(2))) {
      throw new AdapterDefinitionProblem("A * implementation must be of type (Object methodName, Object args)Object: " + target);
    }
  }

  private void checkStarOverrideType(String name, FunctionReference target) {
    if ("*".equals(name) && !target.type().equals(genericMethodType(3))) {
      throw new AdapterDefinitionProblem("A * override must be of type (Object superHandle, Object methodName, Object args)Object: " + target);
    }
  }

  private void checkAllOverridesAndImplementationsExist() {
    try {
      Class<?> parentClass = Class.forName(parent, true, classLoader);
      HashSet<String> canBeOverridden = new HashSet<>();
      for (Method method : parentClass.getMethods()) {
        if (!isStatic(method.getModifiers())) {
          canBeOverridden.add(method.getName());
        }
      }
      for (Method method : parentClass.getDeclaredMethods()) {
        if (!isStatic(method.getModifiers())) {
          canBeOverridden.add(method.getName());
        }
      }
      for (Method method : parentClass.getMethods()) {
        if (!isStatic(method.getModifiers())) {
          canBeOverridden.add(method.getName());
        }
      }
      for (String key : overrides.keySet()) {
        if (!"*".equals(key) && !canBeOverridden.contains(key)) {
          throw new AdapterDefinitionProblem("There is no method named " + key + " to be overridden in " + parentClass);
        }
      }
      for (String iface : interfaces) {
        for (Method method : Class.forName(iface, true, classLoader).getMethods()) {
          canBeOverridden.add(method.getName());
        }
      }
      for (String key : implementations.keySet()) {
        if (!"*".equals(key) && !canBeOverridden.contains(key)) {
          throw new AdapterDefinitionProblem("There is no method named " + key + " to be implemented in " + parentClass + " or interfaces " + interfaces);
        }
      }
    } catch (ClassNotFoundException e) {
      throw new AdapterDefinitionProblem(e);
    }
  }

  private Set<Method> abstractMethodsIn(Class<?> klass) {
    LinkedHashSet<Method> abstractMethods = new LinkedHashSet<>();
    for (Method method : klass.getMethods()) {
      if (isAbstract(method.getModifiers())) {
        abstractMethods.add(method);
      }
    }
    for (Method method : klass.getDeclaredMethods()) {
      if (isAbstract(method.getModifiers())) {
        abstractMethods.add(method);
      }
    }
    return abstractMethods;
  }

  private void checkMethodsToBeImplemented() {
    try {
      LinkedHashSet<Method> abstractMethods = new LinkedHashSet<>();
      abstractMethods.addAll(abstractMethodsIn(Class.forName(parent, true, classLoader)));
      for (String iface : interfaces) {
        abstractMethods.addAll(abstractMethodsIn(Class.forName(iface, true, classLoader)));
      }
      for (Method abstractMethod : abstractMethods) {
        String name = abstractMethod.getName();
        if (!implementations.containsKey(name) && !hasStarImplementation()) {
          throw new AdapterDefinitionProblem("There is no implementation or override for: " + abstractMethod);
        }
        if (implementations.containsKey(name)) {
          FunctionReference target = implementations.get(name);
          if (argsDifferForImplementation(abstractMethod, target) || varargsMismatch(abstractMethod, target)) {
            throw new AdapterDefinitionProblem("Types do not match to implement " + abstractMethod + " with " + target);
          }
        }
        if (overrides.containsKey(name)) {
          FunctionReference target = overrides.get(name);
          if (argsDifferForOverride(abstractMethod, target) || varargsMismatch(abstractMethod, target)) {
            throw new AdapterDefinitionProblem("Types do not match to implement " + abstractMethod + " with " + target);
          }
        }
      }
    } catch (ClassNotFoundException e) {
      throw new AdapterDefinitionProblem(e);
    }
  }

  private boolean varargsMismatch(Method abstractMethod, FunctionReference target) {
    return abstractMethod.isVarArgs() != target.isVarargsCollector();
  }

  private boolean argsDifferForImplementation(Method abstractMethod, FunctionReference target) {
    return (target.type().parameterCount() - 1 != abstractMethod.getParameterTypes().length);
  }

  private boolean argsDifferForOverride(Method abstractMethod, FunctionReference target) {
    return (target.type().parameterCount() - 2 != abstractMethod.getParameterTypes().length);
  }

  private void checkStarConflict() {
    if (hasStarImplementation() && hasStarOverride()) {
      throw new AdapterDefinitionProblem("Having both a star implementation and a star override is forbidden.");
    }
  }

  private void checkSuperTypesExistence() {
    try {
      Class<?> parentClass = Class.forName(parent, true, classLoader);
      if (parentClass.isInterface()) {
        throw new AdapterDefinitionProblem("The parent class cannot be an interface: " + parentClass.getName());
      }
      if (isFinal(parentClass.getModifiers())) {
        throw new AdapterDefinitionProblem("The parent class is final: " + parentClass.getName());
      }
      for (String iface : interfaces) {
        Class.forName(iface, true, classLoader);
      }
    } catch (ClassNotFoundException e) {
      throw new AdapterDefinitionProblem(e);
    }
  }

  private void checkForImplementation(FunctionReference target) throws AdapterDefinitionProblem {
    if (target.type().parameterCount() < 1) {
      throw new AdapterDefinitionProblem("An implemented method target must take at least 1 argument (the receiver): " + target);
    }
  }

  private void checkForOverriding(FunctionReference target) throws AdapterDefinitionProblem {
    if (target.type().parameterCount() < 2) {
      throw new AdapterDefinitionProblem("An overriden method target must take at least 2 arguments (the 'super' function reference followed by the receiver): " + target);
    }
  }
}