/*
 * This file is a part of the SteamWar software.
 *
 * Copyright (C) 2020  SteamWar.de-Serverteam
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

package de.steamwar.command;

import de.steamwar.command.graph.NodeData;
import de.steamwar.command.graph.RootNode;
import de.steamwar.command.utils.Pair;
import de.steamwar.command.utils.Triple;

import java.lang.annotation.Annotation;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.*;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.stream.Collectors;

public abstract class AbstractCommand<T> {

    private static final Map<Class<? extends AbstractCommand<?>>, Map<Class<?>, Function<?, ?>>> EXECUTOR_MAPPER = new HashMap<>();

    public static <E, T> void addExecutorMapper(Class<? extends AbstractCommand<E>> wrapper, Class<T> executorType, Function<E, T> mapper) {
        EXECUTOR_MAPPER.computeIfAbsent(wrapper, __ -> new HashMap<>())
                .putIfAbsent(executorType, mapper);
    }

    protected final String command;
    protected final String permission;
    private final Consumer<CommandLoader<T>> initializer;
    protected final String[] aliases;
    protected final List<String> descriptions = new ArrayList<>();

    private boolean initialized = false;
    protected final RootNode<T> rootNode = new RootNode<>();

    private final Map<String, AbstractTypeMapper<T, ?>> localTypeMapper = new HashMap<>();
    private final Map<String, AbstractTypeValidator<T, ?>> localValidators = new HashMap<>();
    private final Map<String, AbstractTypeSupplier<T, ?>> localSupplier = new HashMap<>();

    protected AbstractCommand(String command, Consumer<CommandLoader<T>> initializer, String... aliases) {
        this(command, null, initializer, aliases);
    }

    protected AbstractCommand(String command, String permission, Consumer<CommandLoader<T>> initializer, String... aliases) {
        this.command = command;
        this.permission = permission;
        this.initializer = initializer;
        this.aliases = aliases;
        initCommand();
        unregister();
        register();
    }

    protected synchronized void initCommand() {
    }

    public abstract void unregister();

    public abstract void register();

    protected void commandSystemError(T sender, CommandFrameworkException e) {
        Logger.getGlobal().log(Level.WARNING, "An unexpected error occurred", e);
    }

    protected void sendMessage(T sender, String message, Object[] args) {
    }

    public final void execute(T sender, String alias, String[] args) {
        initialize();
        List<Runnable> errors = new ArrayList<>();
        try {
            boolean executed = rootNode.execute(sender, new NodeData(alias, fixArgs(args, true), (s, args1) -> {
                errors.add(() -> sendMessage(sender, s, args1));
            }));
            if (executed) return;
            if (!errors.isEmpty()) {
                errors.forEach(Runnable::run);
                return;
            }
            descriptions.forEach(s -> sendMessage(sender, s, new Object[0]));
        } catch (CommandFrameworkException e) {
            commandSystemError(sender, e);
        }
    }

    public final List<String> tabComplete(T sender, String alias, String[] args) throws IllegalArgumentException {
        initialize();
        List<Collection<String>> tabCompletes = new ArrayList<>();
        rootNode.tabComplete(sender, new NodeData(alias, fixArgs(args, false), (s, args1) -> {}), tabCompletes);
        return tabCompletes.stream()
                .filter(Objects::nonNull)
                .flatMap(Collection::stream)
                .filter(Objects::nonNull)
                .filter(s -> !s.isEmpty())
                .distinct()
                .collect(Collectors.toList());
    }

    private String[] fixArgs(String[] args, boolean allowEmpty) {
        int removedCount = 0;
        for (int i = 0; i < args.length; i++) {
            String arg = args[i];
            if (arg.isEmpty() && i != args.length - 1) {
                removedCount++;
                continue;
            }
            args[i] = args[i - removedCount];
        }
        if (removedCount != 0) {
            args = Arrays.copyOf(args, args.length - removedCount);
        }
        if (args.length == 0 && !allowEmpty) {
            return new String[]{""};
        }
        return args;
    }

    private synchronized void initialize() {
        if (initialized) return;

        List<Object> commandObjects = new ArrayList<>();
        initializer.accept(new CommandLoader<>() {
            @Override
            public AbstractCommand<T> get() {
                return AbstractCommand.this;
            }

            @Override
            public void add(Object command) {
                commandObjects.add(command);
            }
        });

        List<Pair<DataImpl, Method>> methods = new ArrayList<>();
        for (Object commandObject : commandObjects) {
            DataImpl dataImpl = new DataImpl(this, commandObject, rootNode, EXECUTOR_MAPPER.getOrDefault(this.getClass(), Collections.emptyMap()), (Map) localTypeMapper, CommandUtils.MAPPER_FUNCTIONS, (Map) localValidators, CommandUtils.VALIDATOR_FUNCTIONS, (Map) localSupplier, CommandUtils.SUPPLIER_FUNCTIONS);
            methods(commandObject).stream()
                    .filter(method -> Arrays.stream(method.getAnnotations()).anyMatch(anno -> anno.annotationType().isAnnotationPresent(Handler.Implementation.class)))
                    .forEach(method -> methods.add(new Pair<>(dataImpl, method)));
        }

        Map<Integer, Map<Triple<DataImpl, Method, Annotation>, List<Handler.HandlerMethod<Annotation>>>> handlerMap = new HashMap<>();
        for (Pair<DataImpl, Method> commandMethod : methods) {
            List<Annotation> annotations = CommandUtils.getAnnotations(commandMethod.b);
            for (Annotation annotation : annotations) {
                Handler.Implementation handler = annotation.annotationType().getAnnotation(Handler.Implementation.class);
                Handler handlerObject;
                try {
                    handlerObject = handler.value().getConstructor().newInstance();
                } catch (NoSuchMethodException | InstantiationException | IllegalAccessException |
                         InvocationTargetException e) {
                    throw new UnsupportedOperationException("Handler " + handler.value().getName() + " cannot be used to check the argument validity", e);
                }
                if (!(handlerObject instanceof Handler.HandlerMethod)) {
                    throw new UnsupportedOperationException("Handler " + handlerObject.getClass().getName() + " is not a HandlerMethod");
                }
                handlerMap.computeIfAbsent(((Handler.HandlerMethod<?>) handlerObject).getRunPriority(), k -> new LinkedHashMap<>())
                        .computeIfAbsent(new Triple<>(commandMethod.a, commandMethod.b, annotation), k -> new ArrayList<>())
                        .add((Handler.HandlerMethod<Annotation>) handlerObject);
            }
        }

        List<Integer> runPriorities = new ArrayList<>(handlerMap.keySet());
        runPriorities.sort(Comparator.naturalOrder());
        for (int runPriority : runPriorities) {
            handlerMap.get(runPriority).forEach((dataMethodAnnotationTriple, handlerMethods) -> {
                handlerMethods.forEach(annotationHandlerMethod -> {
                    try {
                        annotationHandlerMethod.check(new Handler.AnnotationWrapper.ForAnnotation<>(dataMethodAnnotationTriple.c), new Handler.MethodWrapper.ForMethod(dataMethodAnnotationTriple.b), dataMethodAnnotationTriple.a);
                    } catch (Exception e) {
                        throw new UnsupportedOperationException("Method check failed for " + dataMethodAnnotationTriple.b.getName(), e);
                    }
                    annotationHandlerMethod.run(dataMethodAnnotationTriple.c, dataMethodAnnotationTriple.b, dataMethodAnnotationTriple.a);
                });
            });
        }
        rootNode.sort();
        initialized = true;
    }

    // TODO: Implement this when Message System is ready
    /*
    public void addDefaultHelpMessage(String message) {
        defaultHelpMessages.add(message);
    }
     */

    private List<Method> methods(Object commandObject) {
        List<Method> methods = new ArrayList<>();
        Class<?> current = commandObject.getClass();
        while (current != null) {
            methods.addAll(Arrays.asList(current.getDeclaredMethods()));
            current = current.getSuperclass();
        }
        return methods;
    }
}