/*
 * 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 java.lang.annotation.*;
import java.lang.reflect.Method;
import java.lang.reflect.Parameter;
import java.util.*;
import java.util.function.BiConsumer;
import java.util.function.IntPredicate;
import java.util.function.Supplier;
import java.util.stream.Collectors;

public abstract class AbstractSWCommand<T> {

    private Class<?> clazz; // This is used in createMappings()

    private boolean initialized = false;
    protected final List<SubCommand<T>> commandList = new ArrayList<>();
    protected final List<SubCommand<T>> commandHelpList = new ArrayList<>();

    private final Map<String, AbstractTypeMapper<T, ?>> localTypeMapper = new HashMap<>();
    private final Map<String, AbstractGuardChecker<T>> localGuardChecker = new HashMap<>();

    protected AbstractSWCommand(Class<T> clazz, String command) {
        this(clazz, command, new String[0]);
    }

    protected AbstractSWCommand(Class<T> clazz, String command, String... aliases) {
        this.clazz = clazz;
        createAndSafeCommand(command, aliases);
        unregister();
        register();
    }

    protected abstract void createAndSafeCommand(String command, String[] aliases);

    public abstract void unregister();

    public abstract void register();

    protected void commandSystemError(T sender, CommandFrameworkException e) {
        e.printStackTrace();
    }

    protected void commandSystemWarning(Supplier<String> message) {
        System.out.println(message.get());
    }

    protected final void execute(T sender, String alias, String[] args) {
        initialize();
        try {
            if (!commandList.stream().anyMatch(s -> s.invoke(sender, alias, args))) {
                commandHelpList.stream().anyMatch(s -> s.invoke(sender, alias, args));
            }
        } catch (CommandNoHelpException e) {
            // Ignored
        } catch (CommandFrameworkException e) {
            commandSystemError(sender, e);
            throw e;
        }
    }

    protected final List<String> tabComplete(T sender, String alias, String[] args) throws IllegalArgumentException {
        initialize();
        String string = args[args.length - 1].toLowerCase();
        return commandList.stream()
                .filter(s -> !s.noTabComplete)
                .map(s -> s.tabComplete(sender, args))
                .filter(Objects::nonNull)
                .flatMap(Collection::stream)
                .filter(s -> !s.isEmpty())
                .filter(s -> s.toLowerCase().startsWith(string))
                .collect(Collectors.toList());
    }

    private void initialize() {
        if (initialized) return;
        createMapping();
    }

    private synchronized void createMapping() {
        List<Method> methods = methods();
        for (Method method : methods) {
            addMapper(Mapper.class, method, i -> i == 0, false, AbstractTypeMapper.class, (anno, typeMapper) -> {
                if (anno.local()) {
                    localTypeMapper.putIfAbsent(anno.value(), (AbstractTypeMapper<T, ?>) typeMapper);
                } else {
                    SWCommandUtils.getMAPPER_FUNCTIONS().putIfAbsent(anno.value(), typeMapper);
                }
            });
            addMapper(ClassMapper.class, method, i -> i == 0, false, AbstractTypeMapper.class, (anno, typeMapper) -> {
                if (anno.local()) {
                    localTypeMapper.putIfAbsent(anno.value().getTypeName(), (AbstractTypeMapper<T, ?>) typeMapper);
                } else {
                    SWCommandUtils.getMAPPER_FUNCTIONS().putIfAbsent(anno.value().getTypeName(), typeMapper);
                }
            });
            addGuard(Guard.class, method, i -> i == 0, false, AbstractGuardChecker.class, (anno, guardChecker) -> {
                if (anno.local()) {
                    localGuardChecker.putIfAbsent(anno.value(), (AbstractGuardChecker<T>) guardChecker);
                } else {
                    SWCommandUtils.getGUARD_FUNCTIONS().putIfAbsent(anno.value(), guardChecker);
                }
            });
            addGuard(ClassGuard.class, method, i -> i == 0, false, AbstractGuardChecker.class, (anno, guardChecker) -> {
                if (anno.local()) {
                    localGuardChecker.putIfAbsent(anno.value().getTypeName(), (AbstractGuardChecker<T>) guardChecker);
                } else {
                    SWCommandUtils.getGUARD_FUNCTIONS().putIfAbsent(anno.value().getTypeName(), guardChecker);
                }
            });
        }
        for (Method method : methods) {
            add(Register.class, method, i -> i > 0, true, null, (anno, parameters) -> {
                if (!anno.help()) return;
                if (parameters.length != 2) {
                    commandSystemWarning(() -> "The method '" + method.toString() + "' is lacking parameters or has too many");
                }
                if (!parameters[parameters.length - 1].isVarArgs()) {
                    commandSystemWarning(() -> "The method '" + method.toString() + "' is lacking the varArgs parameters as last Argument");
                }
                if (parameters[parameters.length - 1].getType().getComponentType() != String.class) {
                    commandSystemWarning(() -> "The method '" + method.toString() + "' is lacking the varArgs parameters of type '" + String.class.getTypeName() + "' as last Argument");
                    return;
                }
                commandHelpList.add(new SubCommand<>(this, method, anno.value(), new HashMap<>(), localGuardChecker, true, null, anno.noTabComplete()));
            });

            add(Register.class, method, i -> i > 0, true, null, (anno, parameters) -> {
                if (anno.help()) return;
                for (int i = 1; i < parameters.length; i++) {
                    Parameter parameter = parameters[i];
                    Class<?> clazz = parameter.getType();
                    if (parameter.isVarArgs() && i == parameters.length - 1) {
                        clazz = parameter.getType().getComponentType();
                    }
                    Mapper mapper = parameter.getAnnotation(Mapper.class);
                    if (clazz.isEnum() && mapper == null && !SWCommandUtils.getMAPPER_FUNCTIONS().containsKey(clazz.getTypeName())) {
                        continue;
                    }
                    String name = mapper != null ? mapper.value() : clazz.getTypeName();
                    if (!SWCommandUtils.getMAPPER_FUNCTIONS().containsKey(name) && !localTypeMapper.containsKey(name)) {
                        commandSystemWarning(() -> "The parameter '" + parameter.toString() + "' is using an unsupported Mapper of type '" + name + "'");
                        return;
                    }
                }
                commandList.add(new SubCommand<>(this, method, anno.value(), localTypeMapper, localGuardChecker, false, anno.description(), anno.noTabComplete()));
            });
        }

        this.commandList.sort((o1, o2) -> {
            int compare = Integer.compare(-o1.subCommand.length, -o2.subCommand.length);
            if (compare != 0) {
                return compare;
            } else {
                return Integer.compare(o1.comparableValue, o2.comparableValue);
            }
        });
        commandHelpList.sort((o1, o2) -> {
            int compare = Integer.compare(-o1.subCommand.length, -o2.subCommand.length);
            if (compare != 0) {
                return compare;
            } else {
                return Integer.compare(o1.method.getDeclaringClass() == AbstractSWCommand.class ? 1 : 0,
                        o2.method.getDeclaringClass() == AbstractSWCommand.class ? 1 : 0);
            }
        });
        initialized = true;
    }

    private <T extends Annotation> void add(Class<T> annotation, Method method, IntPredicate parameterTester, boolean firstParameter, Class<?> returnType, BiConsumer<T, Parameter[]> consumer) {
        T[] anno = SWCommandUtils.getAnnotation(method, annotation);
        if (anno == null || anno.length == 0) return;

        Parameter[] parameters = method.getParameters();
        if (!parameterTester.test(parameters.length)) {
            commandSystemWarning(() -> "The method '" + method.toString() + "' is lacking parameters or has too many");
            return;
        }
        if (firstParameter && !clazz.isAssignableFrom(parameters[0].getType())) {
            commandSystemWarning(() -> "The method '" + method.toString() + "' is lacking the first parameter of type '" + clazz.getTypeName() + "'");
            return;
        }
        if (returnType != null && !returnType.isAssignableFrom(method.getReturnType())) {
            commandSystemWarning(() -> "The method '" + method.toString() + "' is lacking the desired return type '" + returnType.getTypeName() + "'");
            return;
        }
        Arrays.stream(anno).forEach(t -> consumer.accept(t, parameters));
    }

    private <T extends Annotation> void addMapper(Class<T> annotation, Method method, IntPredicate parameterTester, boolean firstParameter, Class<?> returnType, BiConsumer<T, AbstractTypeMapper<?, ?>> consumer) {
        add(annotation, method, parameterTester, firstParameter, returnType, (anno, parameters) -> {
            try {
                method.setAccessible(true);
                consumer.accept(anno, (AbstractTypeMapper<T, ?>) method.invoke(this));
            } catch (Exception e) {
                throw new SecurityException(e.getMessage(), e);
            }
        });
    }

    private <T extends Annotation> void addGuard(Class<T> annotation, Method method, IntPredicate parameterTester, boolean firstParameter, Class<?> returnType, BiConsumer<T, AbstractGuardChecker<?>> consumer) {
        add(annotation, method, parameterTester, firstParameter, returnType, (anno, parameters) -> {
            try {
                method.setAccessible(true);
                consumer.accept(anno, (AbstractGuardChecker<T>) method.invoke(this));
            } catch (Exception e) {
                throw new SecurityException(e.getMessage(), e);
            }
        });
    }

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

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

    @Retention(RetentionPolicy.RUNTIME)
    @Target({ElementType.METHOD})
    @Repeatable(Register.Registeres.class)
    protected @interface Register {
        String[] value() default {};

        boolean help() default false;

        String[] description() default {};

        boolean noTabComplete() default false;

        @Retention(RetentionPolicy.RUNTIME)
        @Target({ElementType.METHOD})
        @interface Registeres {
            Register[] value();
        }
    }

    @Retention(RetentionPolicy.RUNTIME)
    @Target({ElementType.PARAMETER, ElementType.METHOD})
    protected @interface Mapper {
        String value();

        boolean local() default false;
    }

    @Retention(RetentionPolicy.RUNTIME)
    @Target({ElementType.METHOD})
    protected @interface ClassMapper {
        Class<?> value();

        boolean local() default false;
    }

    @Retention(RetentionPolicy.RUNTIME)
    @Target({ElementType.PARAMETER, ElementType.METHOD})
    protected @interface Guard {
        String value() default "";

        boolean local() default false;
    }

    @Retention(RetentionPolicy.RUNTIME)
    @Target({ElementType.METHOD})
    protected @interface ClassGuard {
        Class<?> value();

        boolean local() default false;
    }

    @Retention(RetentionPolicy.RUNTIME)
    @Target({ElementType.PARAMETER})
    protected @interface StaticValue {
        String[] value();

        /**
         * This is the short form for 'allowImplicitSwitchExpressions'
         * and can be set to true if you want to allow int as well as boolean as annotated parameter types.
         * The value array needs to be at least 2 long for this flag to be considered.
         * While using an int, the value will represent the index into the value array.
         * While using a boolean, the value array must only be 2 long and the value will be {@code false}
         * for the first index and {@code true} for the second index.
         */
        boolean allowISE() default false;
    }

    @Retention(RetentionPolicy.RUNTIME)
    @Target({ElementType.PARAMETER})
    protected @interface OptionalValue {
        /**
         * Will pe parsed against the TypeMapper specified by the parameter or annotation.
         */
        String value();
    }
}