package io.trygvis.rules.network;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;
import org.checkerframework.checker.nullness.compatqual.NonNullType;

import javax.annotation.Nonnull;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
import java.util.regex.Pattern;

@JsonSerialize(using = Ipv4Cidr.Serializer.class)
public class Ipv4Cidr implements Comparable<Ipv4Cidr> {
    public final int network;
    public final int bits;

    public Ipv4Cidr(int network, int bits) {
        if (bits < 0 || bits > 32) {
            throw new IllegalArgumentException("bits must be [0, 32]");
        }

        int hostBits = 32 - bits;
        int netmask = (-1 >> hostBits) << hostBits;

        int x = network & ~netmask;

        if (x != 0) {
            throw new IllegalArgumentException("The host part of the address must be 0.");
        }

        this.network = network;
        this.bits = bits;
    }

    @Override
    public String toString() {
        return "%d.%d.%d.%d/%d".formatted(
                network >> 24 & 0xff,
                network >> 16 & 0xff,
                network >> 8 & 0xff,
                network & 0xff,
                bits);
    }

    private String formatIpv4(int address) {
        return "%d.%d.%d.%d".formatted(address >> 24 & 0xff, address >> 16 & 0xff, address >> 8 & 0xff, address & 0xff);
    }

    public List<Ipv4Cidr> partition(int bits) {
        if (bits <= 0 || bits <= this.bits || bits > 32) {
            throw new IllegalArgumentException("Invalid new network size");
        }

        var list = new ArrayList<Ipv4Cidr>();

        int count = 1 << (bits - this.bits);
        for (int i = 0; i < count; i++) {
            var network = this.network | (i << (32 - bits));

            list.add(new Ipv4Cidr(network, bits));
        }

        return list;
    }

    public List<Ipv4Address> addresses() {
        int size = 1 << 32 - bits;
        var end = network + size;
        var addresses = new ArrayList<Ipv4Address>(size);
        for (int address = network; address < end; address++) {
            addresses.add(new Ipv4Address(address));
        }

        return addresses;
    }

    @Override
    public int compareTo(Ipv4Cidr o) {
        if (this == o) {
            return 0;
        }

        var ret = network - o.network;
        if (ret != 0) {
            return ret;
        }

        return bits - o.bits;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Ipv4Cidr ipv4Cidr = (Ipv4Cidr) o;
        return network == ipv4Cidr.network && bits == ipv4Cidr.bits;
    }

    @Override
    public int hashCode() {
        return Objects.hash(network, bits);
    }

    private static final Pattern pattern = Pattern.compile("([0-9]{1,3})\\.([0-9]{1,3})\\.([0-9]{1,3})\\.([0-9]{1,3})/([0-9]{1,3})");

    public static Ipv4Cidr parseCidr(String cidr) {
        var matcher = pattern.matcher(cidr);
        if (!matcher.matches()) {
            throw new IllegalArgumentException("Not a CIDR: " + cidr);
        }

        var b1 = matcher.group(1);
        var b2 = matcher.group(2);
        var b3 = matcher.group(3);
        var b4 = matcher.group(4);

        int network = parse(b1) << 24 |
                parse(b2) << 16 |
                parse(b3) << 8 |
                parse(b4);

//        System.out.printf("network = %x%n", network);

        var l = matcher.group(5);
        var bits = Integer.parseInt(l);
//        System.out.printf("netmask = %08x%n", netmask);

        return new Ipv4Cidr(network, bits);
    }

    private static int parse(String s) {
        var i = Integer.parseInt(s);
        if (i > 255) {
            throw new IllegalArgumentException("Not a CIDR");
        }

        return i;
    }

    public static class Serializer extends JsonSerializer<Ipv4Cidr> {
        @Override
        public void serialize(Ipv4Cidr value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
            gen.writeStartObject();
            gen.writeObjectField("value", value.toString());
            gen.writeEndObject();
        }
    }
}