package at.yawk.numaec;

import java.util.Random;
import java.util.concurrent.ThreadLocalRandom;
import java.util.function.LongSupplier;

public final class LinearHashMapConfig {
    final float loadFactor;
    final int regionSize;
    final int bucketSize;
    final int pointerSize;
    final int hashLength;
    final LongSupplier sipHashK0;
    final LongSupplier sipHashK1;

    private LinearHashMapConfig(Builder builder) {
        this.loadFactor = builder.loadFactor;
        this.regionSize = builder.regionSize;
        this.bucketSize = builder.bucketSize;
        this.pointerSize = builder.pointerSize;
        this.hashLength = builder.hashLength;
        this.sipHashK0 = builder.sipHashK0;
        this.sipHashK1 = builder.sipHashK1;
    }

    public static Builder builder() {
        return new Builder();
    }

    public static class Builder {
        float loadFactor = 0.75f;
        int regionSize = 16;
        int bucketSize = BTreeConfig.PAGE_SIZE;
        int pointerSize = 4;
        int hashLength = 4;

        LongSupplier sipHashK0;
        LongSupplier sipHashK1;

        { generateHashKey(); }

        public Builder loadFactor(float loadFactor) {
            this.loadFactor = loadFactor;
            return this;
        }

        public Builder regionSize(int regionSize) {
            this.regionSize = regionSize;
            return this;
        }

        public Builder bucketSize(int bucketSize) {
            this.bucketSize = bucketSize;
            return this;
        }

        public Builder pointerSize(int pointerSize) {
            this.pointerSize = pointerSize;
            return this;
        }

        public Builder generateHashKey(Random rng) {
            sipHashK1 = sipHashK0 = rng::nextLong;
            return this;
        }

        public Builder generateHashKey() {
            sipHashK1 = sipHashK0 = () -> ThreadLocalRandom.current().nextLong();
            return this;
        }

        
Number of bytes to use as the hash. Lower values reduce numa memory footprint but effectively limit map size.
/**
         * Number of bytes to use as the hash. Lower values reduce numa memory footprint but effectively limit map size.
         */
        public Builder hashLength(int hashLength) {
            if (hashLength != 1 && hashLength != 2 && hashLength != 4 && hashLength != 8) {
                throw new UnsupportedOperationException("Unsupported hash length");
            }
            this.hashLength = hashLength;
            return this;
        }

        
Do not store the hash of entries, but instead compute it on the fly from the stored key. Lowest possible
numa memory footprint at cost of cpu use during both read and write operations.
/**
         * Do not store the hash of entries, but instead compute it on the fly from the stored key. Lowest possible
         * numa memory footprint at cost of cpu use during both read and write operations.
         */
        public Builder dontStoreHash() {
            this.hashLength = 0;
            return this;
        }

        public LinearHashMapConfig build() {
            return new LinearHashMapConfig(this);
        }
    }
}