package io.trygvis.rules.engine;

import ch.qos.logback.core.util.FileUtil;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.type.TypeFactory;
import com.fasterxml.jackson.dataformat.yaml.YAMLFactory;
import com.fasterxml.jackson.dataformat.yaml.YAMLGenerator;
import org.drools.core.common.DefaultFactHandle;
import org.kie.api.KieBase;
import org.kie.api.runtime.rule.FactHandle;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.*;
import java.util.function.Function;

@SuppressWarnings("unchecked")
public class DbIo {
    private final ObjectMapper mapper;

    public DbIo(KieBase kieBase) {
        var factory = new YAMLFactory();
        factory.enable(YAMLGenerator.Feature.USE_NATIVE_TYPE_ID);
        factory.enable(YAMLGenerator.Feature.USE_NATIVE_OBJECT_ID);
        mapper = new ObjectMapper(factory);
        var typeFactory = TypeFactory.defaultInstance()
                .withClassLoader(new AcmeClassLoader(kieBase));
        mapper.setTypeFactory(typeFactory);
        mapper.findAndRegisterModules();
    }

    public List<Object> load(String file) throws IOException {
        var parser = mapper.getFactory().createParser(new File(file));

        var objects = mapper.readValues(parser, DbObject.class).readAll(new ArrayList<>());

        List<Object> items = new ArrayList<>(objects.size());
        for (DbObject object : objects) {
            try {
                var type = mapper.getTypeFactory().findClass(object.type);
                var x = mapper.treeToValue(object.data, type);
                items.add(x);
            } catch (ClassNotFoundException e) {
                // ignore
            }
        }

        return items;
    }

    public void dump(String s, Collection<FactHandle> factHandles) throws IOException {
        dump(s, factHandles, (o) -> true);
    }

    // This should just sort by all getters instead.
    static class FactCollection<T> {
        public final Class<T> type;
        public final List<T> values;

        public FactCollection(Class<T> type) {
            this.type = type;
            this.values = new ArrayList<>();
        }

        public void sort() {
            var comparator = comparable(type);

            this.values.sort(comparator);
        }
    }

    private static final Map<Class<?>, Comparator> comparators = new HashMap<>();

    private static <A, T extends Comparable<T>> Comparator comparable(Class<A> klass) {
        var comparator = comparators.get(klass);
        if (comparator != null) {
            return comparator;
        }

        // TODO: check if klass is a Comparable directly.

        var prioritizedKeys = List.of("key", "name", "fqdn");

        var discoveredFieldsP1 = new LinkedHashMap<String, Function<Object, Object>>();
        var discoveredFieldsP2 = new LinkedHashMap<String, Function<Object, Object>>();

        var prioritizedTypes = List.of(String.class, int.class, Number.class);

        for (var f : klass.getDeclaredFields()) {
            if (f.getDeclaringClass() == Object.class) {
                continue;
            }

            if (!f.trySetAccessible()) {
                continue;
            }

            var collection = discoveredFieldsP2;

            if (prioritizedTypes.contains(f.getType())) {
                collection = discoveredFieldsP1;
            }

            collection.put(f.getName(), (Object o) -> {
                try {
                    return f.get(o);
                } catch (IllegalAccessException e) {
                    throw new RuntimeException(e);
                }
            });
        }

//        for (var m : klass.getFields()) {
//            if (m.getParameterCount() != 0) {
//                continue;
//            }
//
//            var name = m.getName();
//
//            if (name.startsWith("get") && name.length() > 3 && Character.isUpperCase(name.charAt(4))) {
//                name = name.substring(3, 3).toLowerCase() + name.substring(4);
//            } else {
//                continue;
//            }
//
//            if (!m.isAccessible()) {
//                if (!m.trySetAccessible())
//                    return null;
//            }
//
//            discoveredFields.put(name, m);
//        }

//        System.out.printf("Sorting %s by:%n", klass.getName());

        var discoveredFields = new LinkedHashMap<>(discoveredFieldsP1);
        discoveredFields.putAll(discoveredFieldsP2);

        List<Function<Object, Object>> accessors = new ArrayList<>();
        for (String prioritizedKey : prioritizedKeys) {
            var m = discoveredFields.remove(prioritizedKey);
            if (m == null) {
                continue;
            }

            accessors.add(m);
//            System.out.println("  + " + prioritizedKey);
        }
        accessors.addAll(discoveredFields.values());
//        discoveredFields.keySet().forEach((s)-> System.out.println("  - " + s));

        comparator = (a, b) -> {
//            if (klass.getName().contains("AcmeServer")) {
//                System.out.println("AcmeIo.comparable");
//            }

            for (var method : accessors) {
                var x = method.apply(a);
                var y = method.apply(b);

                if (x == null && y == null) {
                    continue;
                }

                if (x == null) {
                    return -1;
                } else if (y == null) {
                    return 1;
                } else {
                    var res = x.toString().compareTo(y.toString());
                    if (res != 0) {
                        return res;
                    }
                }
            }

            return 0;
        };

        comparators.put(klass, comparator);

        return comparator;
    }

    public void dump(String s, Collection<FactHandle> factHandles, Function<Object, Boolean> filter) throws IOException {
        var yamlFile = new File("out", s + ".yaml");

        FileUtil.createMissingParentDirectories(yamlFile);

        var facts = new TreeMap<Class<?>, FactCollection<Object>>(Comparator.comparing(Class::getName));
        for (var handle : factHandles) {
            if (handle instanceof DefaultFactHandle h) {
                var obj = h.getObject();
                if (!filter.apply(obj)) {
                    continue;
                }

                Class<?> type = obj.getClass();
                var collection = facts.get(type);

                if (collection == null) {
                    collection = new FactCollection(type);
                    facts.put(type, collection);
                }

                collection.values.add(obj);
            }
        }

        var factory = mapper.getFactory();
        try (var writer = new FileWriter(yamlFile);
             var g = factory.createGenerator(writer)) {
            for (var e : facts.entrySet()) {
                var name = e.getKey().getName();

                var collection = e.getValue();
                collection.sort();
                for (var fact : collection.values) {
                    g.writeObject(new DbObject(name, mapper.valueToTree(fact)));
                }
            }
        }
    }

    private static class AcmeClassLoader extends ClassLoader {
        private final KieBase kieBase;

        public AcmeClassLoader(KieBase kieBase) {
            this.kieBase = kieBase;
        }

        @Override
        public Class<?> loadClass(String name) throws ClassNotFoundException {
            try {
                return super.loadClass(name);
            } catch (ClassNotFoundException e) {
                var i = name.lastIndexOf('.');
                String pkg, klass;
                if (i == -1) {
                    pkg = null;
                    klass = name;
                } else {
                    pkg = name.substring(0, i);
                    klass = name.substring(i + 1);
                }
                var clazz = kieBase.getFactType(pkg, klass);
                if (clazz == null) {
                    throw e;
                }

                return clazz.getFactClass();
            }
        }
    }
}