package redis.clients.util;

import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.SortedMap;
import java.util.TreeMap;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Sharded<R, S extends ShardInfo<R>> {

    public static final int DEFAULT_WEIGHT = 1;
    private TreeMap<Long, S> nodes;
    private final Hashing algo;
    private final Map<ShardInfo<R>, R> resources = new LinkedHashMap<ShardInfo<R>, R>();

    /**
     * The default pattern used for extracting a key tag. The pattern must have
     * a group (between parenthesis), which delimits the tag to be hashed. A
     * null pattern avoids applying the regular expression for each lookup,
     * improving performance a little bit is key tags aren't being used.
     */
    private Pattern tagPattern = null;
    // the tag is anything between {}
    public static final Pattern DEFAULT_KEY_TAG_PATTERN = Pattern
	    .compile("\\{(.+?)\\}");

    public Sharded(List<S> shards) {
	this(shards, Hashing.MURMUR_HASH); // MD5 is really not good as we works
	// with 64-bits not 128
    }

    public Sharded(List<S> shards, Hashing algo) {
	this.algo = algo;
	initialize(shards);
    }

    public Sharded(List<S> shards, Pattern tagPattern) {
	this(shards, Hashing.MURMUR_HASH, tagPattern); // MD5 is really not good
	// as we works with
	// 64-bits not 128
    }

    public Sharded(List<S> shards, Hashing algo, Pattern tagPattern) {
	this.algo = algo;
	this.tagPattern = tagPattern;
	initialize(shards);
    }

    private void initialize(List<S> shards) {
	nodes = new TreeMap<Long, S>();

	for (int i = 0; i != shards.size(); ++i) {
	    final S shardInfo = shards.get(i);
	    if (shardInfo.getName() == null)
		for (int n = 0; n < 160 * shardInfo.getWeight(); n++) {
		    nodes.put(this.algo.hash("SHARD-" + i + "-NODE-" + n),
			    shardInfo);
		}
	    else
		for (int n = 0; n < 160 * shardInfo.getWeight(); n++) {
		    nodes.put(
			    this.algo.hash(shardInfo.getName() + "*"
				    + shardInfo.getWeight() + n), shardInfo);
		}
	    resources.put(shardInfo, shardInfo.createResource());
	}
    }

    public R getShard(byte[] key) {
	return resources.get(getShardInfo(key));
    }

    public R getShard(String key) {
	return resources.get(getShardInfo(key));
    }

    public S getShardInfo(byte[] key) {
	SortedMap<Long, S> tail = nodes.tailMap(algo.hash(key));
	if (tail.isEmpty()) {
	    return nodes.get(nodes.firstKey());
	}
	return tail.get(tail.firstKey());
    }

    public S getShardInfo(String key) {
	return getShardInfo(SafeEncoder.encode(getKeyTag(key)));
    }

    /**
     * A key tag is a special pattern inside a key that, if preset, is the only
     * part of the key hashed in order to select the server for this key.
     * 
     * @see http://code.google.com/p/redis/wiki/FAQ#I
     *      'm_using_some_form_of_key_hashing_for_partitioning,_but_wh
     * @param key
     * @return The tag if it exists, or the original key
     */
    public String getKeyTag(String key) {
	if (tagPattern != null) {
	    Matcher m = tagPattern.matcher(key);
	    if (m.find())
		return m.group(1);
	}
	return key;
    }

    public Collection<S> getAllShardInfo() {
	return Collections.unmodifiableCollection(nodes.values());
    }

    public Collection<R> getAllShards() {
	return Collections.unmodifiableCollection(resources.values());
    }
}