// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.config.server;

import com.yahoo.config.model.api.ConfigDefinitionRepo;
import com.yahoo.vespa.config.ConfigCacheKey;
import com.yahoo.vespa.config.ConfigDefinitionKey;
import com.yahoo.vespa.config.PayloadChecksum;
import com.yahoo.vespa.config.buildergen.ConfigDefinition;
import com.yahoo.vespa.config.protocol.ConfigResponse;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.Function;

import static com.yahoo.vespa.config.PayloadChecksum.Type.XXHASH64;

/**
 * Cache that holds configs and config definitions (builtin and user config definitions).
 *
 * @author vegardh
 */
public class ServerCache {

    private final ConfigDefinitionRepo builtinConfigDefinitions;
    private final ConfigDefinitionRepo userConfigDefinitions;

    // NOTE: The reason we do a double mapping here is to de-dupe configs that have the same md5.
    private final Map<ConfigCacheKey, PayloadChecksum> checksums = new ConcurrentHashMap<>();
    private final Map<PayloadChecksum, ConfigResponse> checksumToConfig = new ConcurrentHashMap<>();
    private final Object [] stripedLocks = new Object[113];

    public ServerCache(ConfigDefinitionRepo builtinConfigDefinitions, ConfigDefinitionRepo userConfigDefinitions) {
        this.builtinConfigDefinitions = builtinConfigDefinitions;
        this.userConfigDefinitions = userConfigDefinitions;
        for (int i = 0; i < stripedLocks.length; i++) {
            stripedLocks[i] = new Object();
        }
    }

    // For testing only
    public ServerCache() {
        this(new StaticConfigDefinitionRepo(), new UserConfigDefinitionRepo());
    }

    private void put(ConfigCacheKey key, ConfigResponse config) {
        PayloadChecksum xxhash64 = config.getPayloadChecksums().getForType(XXHASH64);
        checksums.put(key, xxhash64);
        checksumToConfig.put(xxhash64, config);
    }

    ConfigResponse get(ConfigCacheKey key) {
        PayloadChecksum xxhash64 = checksums.get(key);
        if (xxhash64 == null) return null;
        return checksumToConfig.get(xxhash64);
    }

    public ConfigResponse computeIfAbsent(ConfigCacheKey key, Function<ConfigCacheKey, ConfigResponse> mappingFunction) {
        ConfigResponse config = get(key);
        if (config != null) {
            return config;
        }
        synchronized (stripedLocks[Math.abs(key.hashCode()%stripedLocks.length)]) {
            PayloadChecksum xxhash64 = checksums.get(key);
            if (xxhash64 == null) {
                config = mappingFunction.apply(key);
                put(key, config);
                return config;
            }
            return checksumToConfig.get(xxhash64);
        }
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("Cache\n");
        sb.append("builtin defs: ").append(builtinConfigDefinitions.getConfigDefinitions().size()).append("\n");
        sb.append("user defs:    ").append(userConfigDefinitions.getConfigDefinitions().size()).append("\n");
        sb.append("md5sums:      ").append(checksums.size()).append("\n");
        sb.append("md5ToConfig:  ").append(checksumToConfig.size()).append("\n");

        return sb.toString();
    }

    public ConfigDefinition getDef(ConfigDefinitionKey defKey) {
        ConfigDefinition def = userConfigDefinitions.get(defKey);
        return (def != null) ? def : builtinConfigDefinitions.getConfigDefinitions().get(defKey);
    }
    
    /**
     * The number of different {@link ConfigResponse} elements
     * @return elems
     */
    public int configElems() {
        return checksumToConfig.size();
    }
    
    /**
     * The number of different key→checksum mappings
     * @return elems
     */
    public int checkSumElems() {
        return checksums.size();
    }

}